Thunder-Lizards
LIFE OF THE PAST James O. Farlow, Editor
INDIANA UNIVERSITY
PRESS
Bloominston and Indianapolis
Thundertizards
The Sauropodomorph Dinosaurs Edited by Virginia Tidwell and Kenneth Carpenter
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Librarv of Congress Cataloging-in-Publicatron Data Thunder-lizards : the Sauropodomorph dinosaurs / edited by Virginia Tidwell and Kenneth Carpenter. p. cm.-(Life of the past) L.rcludes bibliographical references and inder. ISBN 0-253-345.{2-1 (cloth : alk. paper)
1. Saurischia. 2. Saurischia-Anaromy.
3. Saurischia-Aging. 4. Saurischia-Infancv. 5. Saurischia-Evolution. 5. SaurischiaMorphologv. 7. Animal mechanics. i. Tidr.vell,
Virginia. II.
Carpenter, Kenr.reth. QE862.53T48 2005
III.
Series.
567.913-dc22 2004018474
r2345100908070605
CONTENTS
Contributors
PART 1
ONE:
Sauropods Old and New
. Postcranial Anatomy of Referred Specimens of the Sauropodomorph Dinosaur Melanoroslurus from the Upper Triassic of South Africa Peter
2. 3
.
ix
L
M. Galton, JacquesVan Heerden, and Adam M. Yates
The Genus Barosaurus Marsh (Sauropoda, Diplodocidae) 38 John S. Mclntosh Reassessment of the Early Cretaceous Sauropo d Astrodon
johnsoni Leidy 1865 (Titanosauriformes) 78 Kenneth Carpenter and Virginia Tidwell
4
.
Osteology of Ampelosawrws atacis (Titanosauria) from Southern France 115 Jean Le Loeuff PART
T\7O:
Sauropods Young to Old
5 . New Juvenile Sauropod Material from Sfestern Colorado, and the Record of Juvenile Sauropods from the Upper Jurassic
Morrison
Formation
1'41,
John R. Foster 6 . New Adult Specimens of CamarasAurus lentus Highlight Ontogenetic Variation within the Species 154 Takehito lkejiri, Virginia Tifuaell, and Dauid L. Trexler
.
\Se -Related Cl'rar:rcterrstics For,rnd
in a Partial Pelvis of Camaraslurus \-irgini; Tidu,ell, Kenneth Stadttnan, and Allen Shaw S
11
Ontogeneric Variation and Isometric Growth in rhe Forelimb of the Early Cretaceous Sauropod Venenosaurus Virginia Tidwell and D. Ray Wilhite
PART
THREE: Body Parts: Morphology and Biomechanics
.
Neuroanatomy and Dentition of Camarasaurus lentus Sankar Chanerjee and Zhong Zheng
9
.
10
.
.
Neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs Kent A. Steuens and J. Michael Parrish Neck Posture of Sauropods Determined Using Radiological Imaging to Reveal Three-Dimensional Structure of Cervical Vertebrae Dauid S. Berman and Bruce M. Rothschild 12
13
'
.
180
t87
199
21,2
L.).1
Evolution of the Hyposphene-Hypanrrum Complex within Sauropoda 248 Sebastidn Apesteguia
variation in the Appendicular Skeleton of North American
SauropodDinosaurs:Taxonomiclmplications 268 D. Ray'Wilhite
14
.
First Articulated Manus of Diplodocus carnegii 302 Malcolm'W. Bedell Jr and Dauid L. Trexler 15
.
Evolution of the Titanosaur
Metacarpus 3ZI
Sebastidn Apesteguia
16
.
Pes
Anatomr- in Sauropod Dinosaurs: Implications for Functional Morphology, Evolution, and Phylogeny 346 Mattheu F. Bonnan
17
vi .
Contents
.
Sauropod Stress Fracures as Clues to Activity Bruce M. Rothschild and Ralph E. Molnar
381
PART 18
.
FOUR: Global Record of Sauropods
Between Gondwana and Laurasia: Cretaceous Sauropods in an Intraoceanic Carbonate Platform
395
Fabio M. DaIIaVecchia 19
.
Sauropods of Patagonia: Systematic Update and Notes on Global Sauropod Evolution Leonardo Salgado and Rodolfo A. Coria
20
21
.
.
Observations on Cretaceous Sauropods from Australia Ralph E. Molnar and Steuen W. Salisbury
430 454
Late Cretaceous (Maastrichtian) Nests, Eggt, and Dung Mass (Coprolites) of Sauropods (Titanosaurs) from India D. M. Mohabev
466
Index
491,
Contents
.
vii
CONTRIBUTORS
Sebasti6n Apesteguia, Museo Argentino de Ciencias Naturales "B. Rivadavia," Av. Angel Gallardo 470, (1405) Buenos Aires, Argenuna. Malcolm'\i7. Bedell Jr., Big Horn Basin Foundation, P.O. Box 868,
Thermopolis,'V7yoming 82443.
David S. Berman, Section of Vertebrate Paleontology, Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, Pennsylvania 1.521.3.
-$Testern
^\latthew F. Bonnan, Department of Biological Sciences, Illinois University, Macomb, Illinois 61455. Kenneth Carpenter, Department of Earth Sciences, Denver Museum of Natural History, 2001 Colorado Blvd., Denver, Colorado 80205. Sankar Chatterjee, Museum of Texas Tech University, Box 43191, Lubbock, Texas 7 9 409-319 1. Rodolfo A. Coria, Direcci6n Provincial de Cultura-Museo Carmen Funes, Av. C6rdoba 55 (8318) Plaza Huincul, Neuqu6n, Argentina. Fabio M. Dalla Vecchia, Museo Paleontologico Cittadino di Mon-
falcone (Gorizia), Via Valentinis 134, I-34074 Monfalcone (Gorizia), Italy.
Iohn R. Foster, Museum of \Testern Colorado, P.O. Box 20000, Grand Junction, Coiorado 81502. Peter M. Galton, College of Naturopathic Medicine, University of Bridgeport, Bridgeport, Connecticut 06601,-2449. T.rkehito Ikejiri, Department of Geosciences, Fort Hays State University, Hays, Kansas 67601..
':an Le Loeuff, Mus6e des Dinosaures, LL260 Esp6raza, France. -,rlrn S. Mclntosh, 278 Court St., Middletown, Connectrcut 06457. l. \L Mohabey, Geological Survey of India, Seminary Hills, Nagpur-440 006,India. 3.:lph E. Molnar, P.O. Box 158, Flagstaff, Arizona 86002.
J. Michael Parrish, Department of Biological Sciences Northern
Illi-
nois University, DeKalb, Illinois 60115. Bruce M. Rothschild, Arthritis Center of Northeast Ohio, 5500 Market Street, Youngstown, Ohio 44572. Leonardo Salgado, Museo Universidad Nacional del Comahue, Buenos Aires 1400 (8300) Neuqu6n, Argentina. Steven \X/. Saiisbury, Department ol Zoologv and Entomology, University of Queensland, Brisbane, Queensland , 4072, Australia. Allen Shaw, Section of Vertebrate Paleontologl', Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, Pennsylvania 15213. Kenneth Stadtman, Brigham Young University Earth Science Museum, P.O. Box 23300, Provo, Utah 84602.
Kent A. Stevens, Department of Computer and Information Science, University of Oregon, Eugene, Oregon 97403. Vrrginia Tidrvell, Department of Earth Sciences, Denver Museum
of Natural History, 2001 Colorado Blvd, Denver, Colorado 80205.
David L. Trexler, Timescale Adventures, P.O. Box 356, Choteau, Montana 59422. Jacques Van Heerden, Biological and Nursing Sciences, Universitl' of Fort Hare, Alice 5700, South Africa. D. Ray \7ilhite, Department of Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana 70803.
Adam M. Yates, Bernard Price Institute of Paleaontological Research, Witwatersrand University, Johannesburg 2050, South Africa. ZhongZheng, Museum of Texas Tech Universitn Bor 43191,Lubbock, Texas 79409-3791.
x .
Contributors
Part One Sauropods Old and New
L. Postcranial Anatomy of Referred Specimens of the Sauropodomorph
Dinosasr Melanorosaurus from the Upper Triassic of South Africa Psrpn M. GerroN, Jecquns VeN HnenopN, AND Aoeu M. Yarps
Abstract Postcranial remains of two referred specimens of the sauropododomorph dinosaur Melanorosaurus readi Haughton 7924 ate described from the Lower Elliot Formation (Upper Triassic, Norian) of South Africa. The two specimens, found together, are about the same size, but one is slightly more massive than the other. The bones include vertebrae, two complete sacra, scapulae, a humerus, an ulna, and most of the peivis and hindlimb. One autapomorphy noted is the presence of four vertebrae in the sacrum with incorporation of a dorsosacral. Therefore the sacral count is DS1 + S1 + 52
+
CS. Depending on the cladistic analysis followed, Melano' rosaurus readi ts either a prosauropod with a few characters convergent to Sauropoda, or it is a sauropod with several prosauropod characters. We tentatively regard Melanorosaurus as Sauropodomorpha incertae sedis pending further analysis of the holotype and of all the referred speclmens.
Introduction Four valid taxa of sauropodomorph dinosaurs have been described from the Lower Elliot Formation (Upper Triassic, Norian) of South
Africa (Olsen and Galton 1984; Lucas and Hancox 2001), the fauna of which is discussed in several papers (Olsen and Galton 1984; Kitching and Raath 1984; Galton and Van Heerden 199g; Lucas and Hancox 2001). The most common remains have been re-
ferred to the prosauropod Ewskelosaurus browni Huxley, 1g66 (Van Heerden 1.979; Kitching and Raath 1984). Howeveq as pointed out by Yates (in press a), the holotype of E. browni rs a nomen dubium. The holotype of the next available species name for
rhis material , Plateosauraerzs Huene 1932 (for plateosaurus cullingworthi Haughton 7924), has a unique combination of prosauropod
and sauropod characters, as well as two autapomorphies (yates in prep.). It is therefore considered as sauropodomorpha incertae sedis (Yates in press a). Blikanasaurus cromptoni (Galton and Van Heerden 1985), which is represented by a very stocky partial hindlimb (Galton and Van Heerden 1998), was originally described as a prosauropod, but is now considered to be a sauropod (Galton and Upchurch in Upchurch et al. 2002; Galton and Upchurch in press; Upchurch et al. in press; Yates 2003a). The partial skeleton of Antetonitrus ingenipes (Yates and Kitching 2003) is also a sauropod. Based on a revised concepr of the Sauropoda (yates in press b), Yates (in press a) considers an associated partial vertebral series and
femur (BPI 114953) to be the only true prosauropod described to
date from the Lower Elliot Formation. However, the Melanorosauridae (and Pldteosaurauus as Euskelosaurus\ are considered to be prosauropods by other workers (Fig. 1.1A) (e.g., Galton and Upchurch in Upchurch et al. 2002; Upchurch et al. 20041Galton and Upchurch 2004; Sereno 1999; IJpchurch 1998; Wilson and Sereno 1998; Wilson 2002). The Melanorosauridae Huene 1929 is based on Melanorosaurus readi Hatghton 1,924 (for biography see Raath 7994). Van Heerden
(1979) regarded
M. readi as a junior synonym of the
sympatnc
"Euskelosaurus browni," which he transferred from the Melanorosauridae to the Plateosauridae Marsh 1895. However, Galton (1985) pointed out that the femur of Melanorosdurus resembres that of Riofasaurus from the Upper Tliassic of Argentina (Bonaparre 7972), a raxon accepted by Van Heerden (1979) as a non_ plateosaurid, because the femur is straight in anterior or posrerlor viervs r'vith the fourth rrochanrer close to or on the medial margin of the shaft. In"EuskelosAttrLts" (Huene 1906; Van Heerden 1979lGalton 1985), the femur is sigmoidal in these views, with the fourth trochanter well removed from the medial edge of the shaft as in other plateosaurids. Concerning the femur of Melanoroslurus, Van Heerden (1979) noted that the straightness of the femoral shaft may be due to distortion because the prorimal end, which lacks a proper
head,
is unlike that found in
Rioiasaurus and
is similar to
"Euskelosaurus." Galton (1935) noted that the femur does not ap-
2.
Peter
M. Galton,
Jacques Van Heerden, and Adam
M. yates
Ancslor
An@stor
B
Blikanasaurus Kotasaurus Vulcanodon
Satumalia Ihecodonfosaurus Efraasia
Banpasautus Shunosaurus
Rlolsaurus
Thecodontosaurus
P/al@saurus
Satunalia Ammosautus Anchisautus Riojasautus Melanorosaurus Camelotia VatIIetUrIc Lessemsaurus
l/t ssGpondy,us LtJfengosaws
Aroiisaurus
e
fulelaf,ffiawus
Jingshanosautus
Antelonitrus
Yunnanosaurus MassosPondylus Mussaurus Coloradisaurus "G." sinensis Lulengoseurus
/sanosaurus
Euskelosaurus Plateosaurus Serrosaurus
Kolasaum
Vulcil&M Shun6aurus Barapasautus
Omsaurus Ne6auropoda
Fig. 1.1. Two recent cladistic dndlyses of bdsal Saurctpodotnorpha. (A) One of the two most parsimonious trees found by a Heuristic anall'sis using PAUP 4.0 [Swofford (1c)98); see Galtott and Llpcburch (2001) for details]. The other mrtst parsimctnious tree is identical to tbat shott'n, except that Nlassospondvlus azd Yur.rnanosaurus haue sutapped positictrts. Tree statistics: Length = 279 steps; Cl = 0.5'11; RI = 0.63.5; RCI = 0.J55. From Galton and Llpchurcb (in press)' who prouide a full discussion of the 136 chdracters, nodes, and genera, plus the chardcter matrix. Tbe s!*napomorphies cited for the nodes are based ttn NM QRi.551, with mention if these are also present in SAM 3149 or 34i0. "G." sinensis = G)'posaurus sinensis of Young (1911 a, 1L)48), Sellosaurus = Efraasta, the genus to which most of the Pfdffenhofen specimens dre now referted, see Yates (2003b). (B) Simplified cladogram of fiue mr,tst-parsimonictus trees. Tree statistics:
Length = 149 steps; CI = 0.513,1; Rl = 0.7288 after ttnstable Blikanasaurus /:as been pruned. After Yates and Kitcbing (2003), a'ho prouide details on 212 characters, nodes, and genera plus character matrix. Abbreuiations: p = Prosauropoda; s = SauroPodomorphd: sa = Sduropoda.
pear distorted (see stereo photographs in Van Heerden 1977, pls. 6-8; Van Heerden 1979,p\s.64,65), and the degree of development of the head varies in different-sized femora of Riojasauras (Bonaparte 7972,
fig. 68). The tabular listing of the constituent genera of the Plateosauridae and Melanorosauridae given in Galton (1990, table 15.1) is in error. In the table, Plateosauridae includes only Ammosdurus, Musslurus, Plateosaurus, and Se/iosaurus. Three other genera, Co/oradosdurus, "Euskelosaurus," and Lufengosaurzs, which are discussed as plateosaurids in the text, were incorrectly tabulated within the Melanorosauridae and this has lead to some confusion. \Wellnhofer (1993) used the genera listed in Galton (1990, table 'Wellnhofer) for the 15.1; sometimes mistakenly cited as 1985 by Plateosauridae and Melanorosauridae. Benton (1'993, L994) rncotrectly cited "Euskelosaurus" as an earliest record and Lufengosdurus as the latest record for the Melanorosauridae. However, Postcranial Anatomy of Referred Specimens of Melanorosaurus
'
3
these three genera are included in the plateosauridae in Galton (7992, table 15.1), in which the Melanorosauridae is restricted to three genera from the Upper Triassic, namely, Camelotia borealis Galton 1985, Melanorosaurus readi Haughton 1.924; and Riojasaurus incertus Bonaparte 1969, plus an unnamed melanorosaurid from Argentina (Bonaparte 1986). Camelotid was found in the \Testbury Formation (Upper Triassic, Rhaetian) of England, and the described remains consisr of vertebrae, a femur, and phalanges with fragments of a pubis, an is-
chium,
a tibia, and a
metatarsal (Galton 1998). Details on
Melanorosaurus are given below. Riojasaurus comes from the Upper Los Colorados Formation (Upper Triassic, Norian; Bonaparte 1972) of Argentina. It is the best-known melanorosaurid, with remains of approximately rwenty individuals. There are some compiete skeletons and remains of different age groups that illustrate growth changes (Bonaparte 7972), and a complete skull and associated skeleton (Bonaparte and Pumares 1995). An unnamed melanorosaurid from the Late Triassic (Norian) of Argentina was briefly described by Bonaparte (1986) on the basis of two neural arches, those of a posterior cervical and an anterior dorsal that now comprise part of the holotype of Lessemsaurus sauropoides Bonaparte 7999. Unfortunately, the holotype only consists of the neural arches of three cervicals, fourteen dorsals, and fivo sacrals, together with the centra from three cervicais and numerous dorsals. These vertebrae are much more sauropod-like than those of other prosauropods, and, as noted by Yates and Kitching (2003), they bear a close resemblance to those of Antetonitrus. Van Heerden and Galton (1997)provided a preliminary description of a new specim en of MelanosAurus readi. The characers of this specimen were used in cladistic analyses of the Sauropodomorpha, which placed Melanorosauras in the Prosauropoda (Fig. 1.1A; Galton and Upchurch in Upchurch et al. 2002; Galton and Upchurch 2004) and in the Sauropoda (Fig. 1.1B; yates 2003a; yates and Kitching 2003). These referred bones of MeldnorosAurus are irlustrated in detail in this paper and their affinities are considered on the basis of the cladistic analyses cited above.
Institutional abbreuiations. BPl-Bernard price Institute for
Palaeontological Research, University of \fitwatersrand, Johannesburg, South Africa; NM-National Museum, Bloemfontein, Free
State, South Africa; and SAM-South African Museum. Caoe Town, South Africa. Systematic Paleontology Prosauropoda Melanorosaurus r eadi Hatghton 1924 Syntypes. SAM 3449 includes a right ilium (Haughton 7924, fig. 44), a left pubis, a left tibia (Haughton 1924, fig.46; Van Heerden 1979, fig.22, pls. 66, 67), aleft fibula, metatarsals, a right ulna (Haughton 1924: fig.43), and both radii. SAM 3450 consists of a
4.
Peter -\I. Galton, Jacques Van Heerden, and Adam
M.
yates
right femur (Haughton 1924, fig.45; Van Heerden 7979, fig.21. pls. 64, 65) and the proximal half of an eroded right humerus. Type locality. Base of the Elliot Formation (formerly known as the Red Beds), under the first sandstone ridge u'est of the dolerite dike on the north slope of the Thaba 'N1'ama (Black Mountain). Thaba is iocated betr'veen Josana's Hoek and Josana's Nek near Bensonvale, Herschel District, Transkei (formerly in eastern Cape Province), South Africa (SAM Archives). Comments. Van Heerden (1979) cited Haughton (1924) that the femur r,vas found some distance a\ ray from the rest of the skeletal material. Haughton (7924, 429, 433) noted that the bones "were lying isolated and embedded in a soft red mudstone below a sandstone band," "together with a femur partiy embedded in the overlying sandstone and the proximal half of a humerus found weathered down the slope" and that the femur "was in doubtful association with the other remains and may possibly belong in another form." This material was restudied by Van Heerden (1979) and most of it was referred to Euskelosaurtts browrtL r'vith the exception of one sacral, possibly the tibia, and the weathered femur. The femur was thought to be possibly distorted and therefore unsuitable as the holotype of the genus and species, thereby rendering Meldnorosatrrus readi a nomen dubium. However, M. readi Haughton 7924 must be a valid taxon because the femur is, in all likelihood, undistorted, and the lack of a proper head is probably the result of weathering. Many additional bones, mostly of Plateosdurduus, were catalogued with SAM 3449 and SAM 3450 since 1921, bm apart from these, the remaining bones probably represent one individual, the syntype. Except for unfigured vertebrae, it would appear from the text that the right ulna and both radii form part of SAM 3449 (Haughton 1924). The bones of SAM 3450 were found separately twenty yards (18.3 m) east of SAM 3449 (SAM archives), with the right humerus downslope of the femur.
Referred Specimens SAM 3532-Referred Specimen of Haughton (1921)
Mdterial. Unfigured vertebrae, an almost complete left scapula, a right humerus (Haughton 1924, fig. 42), a complete left ilium, and a metatarsal lll (Haughton 1924,Fi1.47). Locality. About one-third up in the Lower Elliot Formation, at a higher horizon than the holotype. From below the Rooi Nek, between Kromme Spruit and Ma;uba Nek, Hershel. Cornments. A somelvhat smaller specimen than the holotype, it was referred to MelanorosaurLts readi bv Haughton (1924). The left scapula and right humerus were incorrectly referred to the holotype b,v Van Heerden (7979). They were briefly described but not figured, as was metatarsal III. The taronomic status of this specimen, which includes other prosauropod material given the Postcranial Anatomy of Referred Specimens of Melanorttsaurus
'
5
same catalog number srnce 1924, is still to be determined. therefore not be referred to further.
It will
NM QR3314-Specimen of 'Welman (1998, 1999) Material. Most of an articulated skeleton (see photo as preserved in MacRae 1999,202), including a complete skull (see photos in \felman 7999, fi1. a). Locality. Lower part of the Elliot Formation, near Ladybrand, Free State Province.
Comments. Of the skull, only the ventrai aspecr of the basicranium has been described (in Welman 1.999, as a basal prosauropod;
in \Welman 1998, as Euskelosaurers). Although a juvenile individual, this is the most complete specimen of Melanorosaurus discovered to date. A full description of the material will be given elsewhere (Yates, Van Heerden, and Galton in prep.)
NM QR1-t51-Referred Specimen of Van Heerden and Galton (1997)
Mdterial. A cervical verrebra, several dorsal and caudal vertebrae, four associated sacrals, and various girdle and limb bones belonging to two individuals of approximately the same size (but one slightly more robust).
Locdlity. Base of the Elliot Formation, Miiner Farm, 'Wodehouse (Dordrecht) District, Free State Province. Comments. The original excavation rn 1967 included a weathered femur (since lost). The rest of the material was ercavared rn 7971 from the banks of a narrow furrow and over a rectangular area of approximately 6 m. NM QR1551 lacks cranial remains, but there is a fair representation of the different elements of the postcranial skeleton. Most of the material is well preserved. bur some elements exhibit signs of transportation over a short distance prior to fossiiization. This material formed part of the thesis of Van Heerden 11977). A preliminary description was given by Van Heerden and Galton (1997) and is elaborated upon below. Description of NM QR1551 with Brief Comparisons To supplement the description of the bones of NM eR1551, brief comparisons are made with several other sauropodomorphs and basal sauropod genera. The genera, and the references involved
(unless indicated to the contrary), are: Anchisaurus and Ammoslurus (Lower Jurassic, Connecticut Valley, United States; Gal, ton 1976), Antetonitrus (Upper Triassic, South Africa; yates and Kitching 2003), Barapasaurus (Sauropoda, Lower Jurassic, Indra; Jain et al. 1975, 7979), Blikanasaurzs (Sauropoda, Upper Triassrc, South Africa; Galton and Van Heerden 1998), Camelotia (Upper Triassic, England; Galton 1998), "Gyposaurus" capensis (Lower Jurassic, China; Young L941,a, 1948), Kotasaurus (Sauropoda, Lower Jurassic, India; Yadagiri 2001), Isanosaurus (Sauropoda, Upper Triassic, Thailand; Buffetaut et al. 2000, 2002\, Lessem-
6.
Peter
M. Galton,
.|acques Van Heerden. and
Adam M. Yates
saurus (Upper Triassic, Argentina; Bonaparte 1999), Lttfengosaurus (Lower Jurassic, China; Young 1941.b, 1947 , 19 57), Massospondylus (Lower Jurassic, South Africa and Zimbabwe; Cooper 1981), Plateosaurus (Upper Triassic, Germany; Huene 1926,1932;
Galton 1990, 7992, 2001a), Plateosaurauus ("Euskeloslurus," Upper Triassic, South Africa; Van Heerden 1979), Rioiasaurtts (Upper Triassic, Argentina; Bonaparte 1972), Shunosaurus (Sauropoda, Middle Jurassic, China; Zhang 1988), and Vulcanodon (Sauropoda, Lower Jurassic, Zimbabwe; Raath 1972: Cooper 7984). Two proposed relationships for most of these taxa are shown in the cladograms (Fig. 1.1), and the systematic position of Melanorosdurus is discussed below In the section on the anatomy of prosauropods in Galton (7990,7992) and Galton and Upchurch (2004), the condition for Melanoroscturus is based on NM QR1551 (Fig. 1.1A), as it is in Yates and Kitching (2003)' in which this genus is considered to be a sauropod (Fig. 1.18). Vertebrae
Ceruical uertebrae. The centrum of cervical 6 or 7 (Figs. 1.2B, 1.3A-D) is short, broad, and high in comparison to that of cervical 6 of Rioiasaurus and Plateosdunrs (Fig. 1.2A, C, D), with the length:height ratio at about 2.0 rather than more than 3.0 (measurements given in Table 1.1). The diapophysis is better deveioped, but it is close to the parapophysis and is relatively low. The articular ends are not well preserved, but the centrum was probably amphicoelous or opisthocoelous. The articular ends are inclined at 60' (anteriorly) and 80' (posteriorly) to the long axis of the centrum' indicating a distinct anteroventral curvature in the neck. The ventral margin of the centrum is concave in lateral view. The parapophyseal facet is not preserved but it was probably close to the ventral margin. Above this ridge, the lateral side of the centrum is very distinctly concave. The neural arch is fairly low. The neural spine has a narro% short base and projects slightly anteriorly. The anterior half of the dorsal tip of the neural spine is transversely expanded. The zvgapophyses have flat, long, and broad facets inclined at 30-35'to the horizontal. The terminology of \(iilson (1999) for the laminae of sauropod vertebrae is followed for the laminae (or the equivalent ridges) associated with the processes of the vertebrae of NM QR1551. Each parapophysis has a sharp, low ridge extending a short distance posteriorly, but this is the base of the parapophysis. The posterior centroparapophyseai lamina would be more extensive and, although thought to be restricted to dorsal vertebrae in sauropods, it is present in cervicals of Sauroposeiden (Sauropoda, Lower Cretaceous, 'Wedel et al. 2000). The lateral edge of the prczyOklahoma; gapophysis is prolonged posteriorly to the base of the neural spine as a prominent ridge (spinoprezygapophyseal lamina), whereas the posterolateral edge of the postzygapophysis forms a more promir-rent edge (spinopostzygapophyseal lamina) that continues posterodorsally to the broken top of the neural spine. The diapophysis Postcranial Anatomy of Referred Specimens oi Melanorosdurus
'
7
Fig. 1.2. (A) Skull and ceruical ,,/ Riojr,.ruru' ineerru. irz lelt Ltteral t rcu (reucrscdt lrom Bonaparte and Pmnares (191),5). (B) Left lateral uiea, of sixth or
-.6y'i,5
scuctrth ccn'ical t crtclrrs
uf
N{elanorosaurus readi, NM QR 1{51 C-D: Lcfr ldternl uictt of cerui cal s o/ Plateosaurus, /rorz Huerte (19.)2): (C) sixth and (D) eighth. E-F: Leli lateral uietu of t h e tl orsals o/ Melanorosaurus readi, NM QRl.i.i7: (F,) neural arch ottl,- of the eighth 1?); (F) incomplete ninth (l). ()-H: Left Ittteral uietu of the dorsals of Camelotia borealis, reuersed from Seelet (1898): (G) anterior dorsdl
F-l
(?
fourth) and (H) the fourteenth.
I-J: Left lateral uieu of the dorsals o/ Plateosaurus , frotn Huene (1932): (l) eighth and (J) tenth. K-M: Left lateral uieu' of dorsals crf Riojasaurus,
from Bctnaparte
(1972): (K) fifth, (1.) ninth, and
(M) ta,elfth. Scale is tlpploximateb' .i0 mm.
is small compared to those of the dorsal vertebrae. Its base lies just
above the floor of the neural canal and it projects anteroventrafiy towards the parapophysis. There are rwo lamina supporting the diapophysis ventrally. The posterior centrodiapophyseal lamina, which is inclined slightly ventrallv. is much larger that the anterior centrodiapophyseal lamina. Dorsal uertebrae. Remains of four dorsal vertebrae are preserved (Figs. 1.2E, F; 1.3E-I; 1.4A) (measurements given in Table 1.1). A neurai arch possibly represents dorsal 8 (Figs. 1.2E; l.-iE,
8.
Peter N{. Galton, Jacques Van Heerder.r. and Adam
M.
yates
,ffi B
Flg. -1.3. Melanorosaurus readi, NM QR1.t51. A-D: Ceruical uertebra 6 or 7 in (A) left lateral, @) dorsal, (C) anterior, dnd (D) posteriol uiews. E-F: Neural arch ctf sixth or seuenth dorsal uertebra in (E) right lateral and (F) dorsdl uieu's. G-H: Neural arc.b of a posterior dorsal uertebra in (G) dntetior and (H) dorsal uietus. I-J: Centrum of dorsal uertebra in (I) lateral and (J) dorsal uiews. Scale is 50 mm.
H
w TABLE 1.1. Measurements (in mm) of Three Presacral Vertebrae (NM QR1551)
Descriotion Centrrrm
lenoth
6th?
cervical 9th? dorsal 11th? dorsal
+ 118
124
105
Centrum height anteriorly
49
96
r02
Centrum width anteriorly
55
72
+75
Centrum height posteriorly Centrum width posteriorly
61
68
+92 +71
-\{aximum length of vertebra
164
?145*
Maximun-r height of vertebra
||
l
?245"
102 L L
1/ /a
These figures based on a combination of the supposed 8th and 9th dorsals.
Postcranial Anatomy of Referred Specimens ol Melanorosaurus
'
9
'K K qw_
+ -=t €-
.r Le MA N df gl
v'-'r
ur o& *&t af -,
.-=- I g *
rc
jryl
,3f-
-,:sr
-
-'
Fig. 1.4. Melanorosaurus readi, NM QR75J1. (A) Ninth(!) dorsal uertebra in right lateral uietu.
B-D: First sacral uertebra in (B) left lateral, (C) dorsal, and (D) dnterior uieus. E-H: Second and third sacral uertebrae in (E) dnterior, (F) Ieft lateral, (G) right lateral, and (H) dorsal uiews. l-J: Fourth sacral uertebra in (I) dorsal and (J) anterior uiews. K-L: Anterior caudal uertebru in (K) right Iateral and 1Lt anterio, uiews. M-N: Middle caudal uertebra in (M) anterior and (N) Ieft lateral uieus. O-P: Middle caudal uerlebra in tO) posterior and (P) rigbt lateral uiews. Q-R: Middle caudal uertebra in (Q) anterior and (R) Ieft lateral wews. Scale is 50 mm.
10 .
Peter
M. Galton,
F). The neural spine is fairly high, but the ratio of the height to length of the transversely narrow base is less than 1.5. It thickens a little transversely at the dorsal edge and becomes thinner passing posteriorly. The rounded dorsal tip may be the result of weathering. The lower half of the anterior margin of the spine has a deep sulcus, whereas the upper half bears an indistinct keel. The prezygapophysis has a rather long, narrow facet facing dorsomedially at about 30" to the horizonral. Posterodorsally it forms a spinoprezygapophyseal lamina that extends to the base and onto the lower third of the neural spine. There is a distinct hypantrum between the
two prezygapophyses, which is as long axially as the prezygapophyseal facets (Fig. 1.3F). The postzygapophysis also has a long, narrow facet, which is inclined ventrolaterally at about 30" to the horizontal. The dorsoventrai height of the hyposphene equals that of the neural canal, as in sauropods, rather than being much lower, as in prosauropods (Yates and Kitching 2003). Dorsally, a spinopostzygapophyseal lamina ertends to the lorver part of the neural spine. The diapophysis is short, robust, and situated above the level of the neural canal; it projects slightly posterodorsally and is subcircular in axial section (Figs. 1.2E; 1.3E). It is connected ro the zygapophysis by the prezygodiapophyseal, the most prominent lam-
Jacques Van Heer.den, and Adam
M.
Yates
ina, and the postzygapophyseal lamina, rn'hereas ventrally there are posterior and anterior centrodiapophyseal laminae; the latter is the weakest lamina and terminates at the parapophysis. The most complete vertebra probably represents dorsal 9 (Figs. 1.2F; 1.4A). The centrum is distinctly amphicoelous, with no appreciable difference between the anterior and posterior surfaces. As in other prosauropods, the length:height ratio is less than 1'5' The sides are concave, especially in the upper half of the centrum. The ventral margin is concave in lateral view and the edge is rounded in cross-section. The neural arch is high. The base of the neural spine extends beyond the posterior articular surface of the centrum. What remains of the incomplete prezygapophyses are similar to those of dorsal 8. The postzygapophysis has a long, narrow facet inclined at about 40' to the horizontal. It has the same laminae as the preceding vertebra, and a hyposphene situated ventrally' the dorsoventral height of which equals that of the neural canal. The diapophysis has an elliptical base, the three lamina associated with it are slightly better developed, and it is closer to the parapophysis than in cervical 8. A centrum (Fig. 1.3I, J), possibly from dorsal 11, is similar to cervical 9 ercept that it is slightly longer. An incomplete neural arch (Fig. 1.3G, H) is probably from one of the last dorsals and, as in other prosauropods' there is no prezygapophyseal lamina. The base of the neural spine has the same axial length as dorsal 8, but it is broader posteriorly than anteriorll'. The postzygapophyseal lamina is somewhat stronger on this arch than it is in the more anterior dorsals. Sacrum. All the bones in the fossil pocket were disarticulated except for the four sacral vertebrae (Figs. 1.4B-J; 1.5A; 1'6A-D). whose articulated state indicates that they were originally united together as a functional unit. The four sacrals are a little shorter than the ilium, and the sacral ribs fit the rugose medial surface of the ilium (Fig. 1.10B) very well. Comparisons with other prosauropods show that the sacrum has the reptilian sacral vertebrae 1 and 2 and a caudosacral, the plesiomorphic form for the sacrum in prosauropods, and that a dorsosacral is incorporated anteriorly (Fig. 1.6A; see discussion in Galton 7999,2007b). The dorsosacral (Figs. 1.4B-D; 1.6A, B) lacks the neural spine and postzygapophyses, but the rest of this element is well preserved. The centrum is amphicoelous and has concave sides. The ventral margin is concave in lateral view and is less rounded in cross section than is the case in the middle dorsals. The facet of the prezygapophysis faces dorsomedially and is inclined at approximately 40' to the horizontal. It is almost as broad as it is long, it is slightly concave transversely, it has a robust base, and no spinal lamina can be distinguished. The prezygapophyses project a little beyond the centrum anteriorly. The postzygapophyses are broken off, but there is a robust, wedge-shaped hyposphene. The diapophr-sis is fused to its sacral rib. The suture is still visible on the lefthand side in anterior view (Fig. 1.4D). The dorsal surface of the diPostcranial Anatomy of Referred Specimens of Melanorosaurus
'
11
=F*
eE Fig. 1.5. Ivlelanorosaurus readi,
NM QRIiil. (A) Fourth sacral
uertebra in left lateral uieu. B-D: First caudal uertebra in (B) left lateral, (C) right lateral, and (D) posterior uieu,s. E-F: Third(?) caudal uertebra in (E) right lateral dnd (F) posterior uiews. G-I: Middle caudal uertebra in (G) antelior, (H) left lateral, and (I) dorsal uietus. U) Centrum of middle caudal uertebra in rigbt ldterdl t,iew. K-O: Progressiuely more posterior caudal uertebrae in leit lateral fK, I-, N, O) and right lsteral (trl) uiews. Scale is 50 mnt.
ww Ww -M G*
M
ffi"M apophysis-sacral rib complex is flat and horizontal, being extended transversely at its proximal end by the pre- and postzygodiapophy_
seal laminae. The anterior centrodiapophyseal lamina
fo.-,
" strong ventral buttress, extending onto the anterodorsal quarter of the side of the centrum. A low, rounded posteroventral ridge below the posteriorly projecting plate represents a remnanr of the posterior centrodiapophyseal lamina, which is much more prominenr in the preceding dorsals. Laterally the sacral rib has a short anrerior projection that lies in the horizontal plane; and a longer exrension that lies in the vertical plane. The latter is fused with the anterior extension of the second sacral rib. A deep, wide sulcus is presenr between the first sacral rib and the horizontal olate. The centra and sacral ribs of the second thi.d vertebrae of "trd
12 o
Peter
M. Galton,
Jacques Van Heerden, and Adam
M. yates
,i" ' ...-:,1 ;,,:!.,-,rlr, 'i !.'-:-, . i:-
| . \ rr',--!...,...-
;.' _._-l
' .il'_....-'-
_1.,:1,-
" -\l
/
Fig. 1.6. A-D: Left lateral uiew the sacral uertebrae of N{elanorosaurus readi, NM
of
QRl5-51: (A) outline drawing shoLt,ing the fottr sacral uertebrae in articulation; (B) /irst sacral; (C)
ankylosed second and third sacrals uith the sacral rib of the
tI'B
"/
{1L!t4"'-.j? --F
first fused to tbat of the second; dnd (D) fottrth sacral. (E) Left laterdl uieu of the sdcral uertebrae o/ Riojasaurus, from Bondpdrte (11)72); third sacral should be at
I
front
it
as a dorsosacral (Nctuas
1996). F-H: Left lateral uiew of
caudal uertebrae of Melanorosautus readi
IE
F -n\ t)
\nf
lNM
QR155/): (F) the first, (G) the
ltresumed fourth, and (H) a distal caudal uertebra. I and J: Left lateral uiew of caudal uertebrde of Camelotia borealis, from Huene
(1907-08): (I) second and 0) sixth. (K) Left lateral uiew of first
and second caudal uertebrae of Plateosaurus, from Huene (1932). Scale is approximately .50 mm.
the sacrum are fused together (Figs. 1.4E-H; 1.6A) and represent the reptilian sacrals 7 and 2. The centra have the same general shape as the dorsosacral, but that of sacral 2 is slightly longer. The neural spines are high, with transversely thickened tips and short, broad bases. The anterior surface of the neural spines was probably keeled, whereas posteriorlv the ventral two-thirds shows a narrow groove. The spines are directed slightly posteriorly. The prezygapophysis has a short, broad facet facing dorsoventrally and inclined at about 55" to the horizontal. The sacral rib is fused with the diapophysis. In sacral vertebra 1, the diapophyseal part of the complex has a flat dorsal surface in the horizontal plane. Almost all of this is directly supported by the very strong anterior centrodiapophyseal lamina, which extends slightiy farther ventrally than in rhe dorsosacral. The diapophysis proiects beyond the posterior cenPostcranial Anatomy of Referred Specimens of Melanorosaurus
.
1'3
trodiapophyseal lamina
to form a slight
ridge
in the horizontal
plane. There is a strong constriction between the diapophysis and the sacral rib. Just lateral to the diapophysis, the sacral rib divides into a dorsal and a ventral part. The dorsal part curves around to the anterior side and forms a thin plate, which is again yoined to the anterior extension of the ventral part of the rib. Below the dorsal extension, and behind the anterior plate, there is a deep, concave excavation. The ventral part of the sacral rib is very robust. It is expanded dorsally and ventrally and oriented anterodorsally and posteroventrally. The anterodorsal part is confluent rvith the anterior extension of the dorsal part of the sacral rib, whereas the posterior part ioins the anterior extension of the rib of sacral vertebra 2.The diapophysis-sacral rib complex of sacral vertebra 2 lacks the anterior extension of the dorsal part, and there is no lateral connection between the dorsal and ventral parts of the sacral rib. The anterior centrodiapophyseal lamina extends downward to just below the middle of the centrum height. The caudosacral (Figs. 1.4I, J;1.5A; 1.6.4, D) is, in general, similar to sacral 2. The centrum is a little shorter and the neural spine is situated more anteriorly. On each side the diapophysrs forms a shelf anteriorly and slopes posteroventrally. The postzygapophyseal facet is inclined at approximately 65" to the horizontal. Anteriorly it is confluent with the base of the neural spine (as in sacrals 7 and2), and between the paired facets there is a wide sulcus. There appears to have been no hyposphene. The pre- and postzygodiapophyseal laminae are small. The sacral rib has an elliptical end surface, with the long axis inclined obliquely ventralll., the anterior end being lower. There is only a small dorsolateral extension of the sacral rib. Berween this and the large lower part, there is a distinct sulcus on the anterior side. The complex has a single medial and ventral anterior centrodiapophyseal lamina that extends to just below the middle of the centrum height. The anterior surface of this lamina is concave. Caudal uertebrae. There are twenty-two caudal vertebrae (Figs. 1.4K-R; 1.5B-O; 1.6F-H). The proximai caudals (Figs. 1.5B-F; 1.6F) have a high, amphicoelous cenrrum that anteroposteriorly is extremely short with concave sides. The ventral surface is transversely broadened with demifacets for chevrons. The neural spine is tall, being almost as high as those of the sacrals, and it is inclined slightly posteriorly. The postzygapophysis is situated on the base of the neural spine. The facet is slightly longer than broad, and it is inclined between 55o and 60' to the horizontal. Each transverse process is incomplete, but they were probably fairly short; the base is not deep in posterior view (Fig. 1.5D, F) as in sauropods. Each lacks distinct ventral burtresses, but the base is nearly as long as the centrum. The immediately succeeding caudals (Figs. 1.4K-N; 1.6G)have comparatively longer, lower centra. The zygapophyses are smail and their facets are inclined at 50-60'to the horizontal. The neural spine is tall, directed slightly posteriorly, with the base situated on 1.4
.
Peter
M. Galton,
Jacques Van Heerden, and Adam
M.
Yates
the posterior half of the centrum. The spine is eiliptical in cross sec-
tion and the posterior surface is keeled. The transverse processes have a fairly long base, extending almost the whole length of the centrum. The transverse process is directed obliquely posteriorly in the horizontal plane. The mid-caudals (Figs. 1.4O-R; 1.5G-J) are approximately the same length as the anterior ones, but the centrum and neural arch become progressively lorver posteriorly along the series. The neural spine and transverse processes are placed posteriorly. The spine is directed more posteriorly, lvhereas the transverse processes are in-
clined slightly posteriorly and dorsally. The distai caudals (Figs. 1.5L-O; 1.6H) lack a neural spine, and the transverse process is represented only by a slight ridge on the lateral surface of the centrum. The transverse width of the ventral surface, which is slightly concave transversely, almost equals the centrum height. The terminal caudals are very small. Pectoral Girdle and Forelimb
The combined length of the humerus and ulna is 63"h of the length of the femur plus tibia, compared to 70"/' in Rioiasdurus. The relatively shorter forelimb, somewhat shortened trunk (through the inclusion of the last dorsal in the sacrum), and the concurrent strengthening of the sacrum may indicate that Melanorosaurts was more facultatively bipedal than Rioiasdurus. Scapula. The pectoral girdle is represented only by the scapulae: the right is almost complete (Figs. 1.7A, B; 1.8A-C) and the left is incomplete (Fig. 1.11D) (measurements given in Table 1.2). These two are very similar and are probably from the same individual.
The scapula is a long, broad element that would have been held more or less horizontallv. The posterior end measures about 90 mm across (as preserved) whereas the anterior (proximal) end measures at least 190 mm in width (185 mm preserved, restored width 210
mm, Fig. 1.8A). The major portion of the bone is flat, blade-like, and elliptical in cross section. The long edges of the blade are subparallel, being slightiy concave superiorly and straight inferiorly. The glenoid region is transversely thickened. The scapular fossa, adjacent to the glenoid fossa, is large and distinctly separated from the blade, especially in the acromial region. Humerus. There is one weathered right humerus (Figs. 1.7E; 1.8D-F) and the distal ends of a left and a right (not illustrated) (measurements given in Table 1.2). The humerus is 71."h of the length of the femur and its proximal and distal expansions lie in the same plane. The humerus is slightly sigmoidal in lateral view. The head lies just lateral to the midline of the bone. The proximal half is triangular with a concave anterior surface and a convex posterior surface (Fig. 1.8D, F). The deltopectoral crest is broken off, but its base indicates that it extended to the distal half of the bone as in Riojasaurus (Fig. 1.7F); in Anchisdurus, Plateosaurduus, and Plateosaurus (Fig. 1.7G) the deltopectoral crest is limited to the proxiPostcranial Anatomy of Referred Specimens ol Melanorosaurus
'
15
ffi W{
Fig. 1.7. A-B: Left scdpuld euersed) o/ Melanorosaurus
(r
readi, NM QR1J51, in (A) uentral (pctsterior) and (B) Iateral uielus. C and H: Left scapula and coracoid o/ Riojasaurus, from B ondp drte (1972), in (C) Iateral and (H) uentral (posterior) uiews. (D) Left scapula and coracoid of Plateosaurus, reuersed from Gabon (1990). E-G: Antenor uieus of right humerus of (E) Melanorosaurus readi lNM QR1551); /F/ Riojasaurus, reuersed from Bonaparte (1972);
\t /
G I
and (G ) Plateosaurus, /roz Galton (1990). I-J: Left ulna r:f
pl
o
x
i7 n
ffi $/ vt
N{elanorosaurus readi, NM QR1.t51 in (I) lateral and (J) medial uiews. K-L: Left ulna of Rio jasaurus, from B ondp drte (1972), in (K) lateral and (L) medial uieuts. (M) Lateral uietu of the left ulna ofPlateosaurus, from Galton (1990). Scale d[)
ItH h/
E [ lr 11 &\ It\
L%/
dt elt- 5 0 m m.
mal half. In most sauropods the deltopectoral crest is reduced to a low crest or ridge, but it is large in Antetonitrus. The shaft is short and subcircular in cross section proximally. More distally it is elliptical in section, with the long axis placed transversely. The distal end is slightly erpanded, with a flar posterior surface; the anrerior surface has a vague fossa that is not as rounded or as nicely sharpedged as inPlateosaurus (Fig. 1.7G) nor is it as flat as in sauropods. The articular surfaces at both ends are weathered. The humerus rs more massive than that of Plateosaurus (Fig. 1.7G) and, although eroded and incomplete, it is much less massive than that of Rio-
jasaurus (Fig. 1.7F).
16
.
Peter NI. Galton, Jacques Van Heerden, and Adam
M.
Yates
ffi
GW :""1)l'9
% Iig.
1.8. Nlelanorosaurus readi, N,\,I QR l ii L A-C: Right scaPula in (A) lateral, (B) superior tJnlcriot'). and tCt ntediol uitws. D-F: Right humerus in (D) anterior, (E) lateral, and (l) posterior uieuts. G-l: Lelt ulna it (G) dnterior, (H) lateral, and (l) p o sterctlat eral uiet,s. J -1, : Right metatarsal I in ([) laterdl, (K) rnedial, and (L) anterior uiews. Scole is 5() nrm.
Postcranial Anatomy of Referred Specimens of Melanorositurus
'
1'7
TABLE 1.2. Measurements ( in mm)
Element
?*Tii;trtllT: rl*.'
Total length
of Metanoros aurus
Proximal width
Distal width
Scapula
489
?
?
Humerus
450
155
r47
Ulna
269
Pubis
499
178
134
485
176
126
476
?
\t4
Ilium
476
Ischiurn
140
Femur
638
140 135
?
Tibia
640 / oo
217
143
Fibula
185
509
t76
120
485
190
130
481
100
)
Forearm. No recognizable part of a radius or manus rs preserved, but there is a fairly complete left ulna (Figs. 1.7I, J; 1.8G-I). In general it is similar to those of Plateosaurauus and Plateosaurus
(Fig. 1.7M), but it is less robust than in the former. The proximal end appears to be subtrianguiar in outline rather than triradiate, with a deep radial fossa as in Antetonitrus and sauropods; the lateral process is incomplete, so it cannot be determined if it was Ionger than the anterior process. The olecranon process is prominent, as in prosauropods and Antetonitrus, rather than reduced or absent as in sauropods. The incomplete distal end has a longitudinal ridge on the medial side of the posterior surface. Peluic Girdle and Hindlimb
Ilium.There is a well-preserved right ilium (Figs. 1.9A; 1.10A, B) that is not as robust as rhar of Riojasawras (Fig. 1.9B, C) (measurements given in Table 1.2). The dorsal margin is stepped, but not as distinctly as in Rioiasaurus, and the anterior process of the iliac blade is short and pointed, whereas the posterior process ls both deeper and much longer as in most prosauropods. In Anchisaurus and Ammosaurus the anterior process is long, and it makes an acute angle with the pubic process. The ischial process has about the same vertical extent as the pubic process, so it is
not reduced as in the
sauropods Bardpdsaurus, Kotasaurus,
Shunosaurus, and Vulcdnodon. The acetabulum is not backed by bone and the overail form is more similar to that of Plateosaurws than to that of Riojasaurus (Fig. 1.9B-D). The anterior part of the
18
.
Peter
M. Galton,
Jacques Van Heerden, and Adam
M.
yates
lig. 1.9. A-B: Lateral yiew of right ilium o/ /A) Melanorosaurus readi, N-&{ QR1551, and (B) Riojasaurus, reuersed front
OGR^,
,F$'. U'\
Bonaparte (1972). C-D: Reconstrttctiun oI right peluis in lateral uiew o/ /C/ Riojasaurus, from Bonaparte (1972), and (D) Scdle
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supra-acetabular ridge is better developed than the posterior part, Lr-rdicating that in life the dorsal margin of the ilium was orientated anterodorsally. Pubis. There are three pubes, one left and two right. One of the
right pubes is almost complete and virtually undistorted (Fig. 1.10C-E) (measurements given in Table 1.2). Laterally the pubic plate has a strong ridge in the proximal half of its length. Between ihis ridge and the obturator foramen, there is a distinct depression ,rnd the bone is very thin. The obturator foramen is large, as in ,rther prosauropods such as Plateosaurauus and Plateosaurus (Ftg. 1.9D), rather than small, as in Riojasaurzs (Fig. 1.9C). The proxi-
Fig. 1,10. tr{elanorosaurus readi,
NM QRl.t.tl. A-B: Right ilium in \At ldtcrcl ,tnd
1Bt
tnedial uiews.
C-E: Right pubis in (C) posterouentral and slightly lateral), (D) medial, and (E) dorsdl (and slightly medial) uieuts. F-G: t
More massiue left tibia in (F) lateral and (G) posterior uiea's. H-I: Incomplete left tibia in (H) medidl and (I) dnterior uietus. Scale is .50 mtn.
Postcranial Anatomy of Referred Specimens of Melanorosaurus
'
19
mal part is turned through 50' with regard to the distal part. The distal half of the pubic plate is triangular in cross section, the lateral edge forming the narrorv base of the triangle. The distal end is expanded anteroposteriorh, rl'ith its greatest thickness near the lateral margin. In this wa)'a posterioriy directed "foot" is formed, but this is much less prominent than in theropod dinosaurs. In anterior view the Iateral margin is slightly sigmoidal, not stepped as in Riojasattrus, whereas the medial margin (a1ong the pubrc symph,vsis) is straight.
Ischia (Measurements given in Table 1.2). The united distal ends of two ischia are preserved (Fig. 1.11A-C). The shaft of each is trianguiar in cross section. There is slight transverse and strong
anteroposterior expansion on the distal ends, but not as much
as
rn Pldteosdurauus, and the distal ends are not blade-like as in sauropods.
Femur. One of the elements found originall,v in 1967 was a weathered femur that was iost. In addition, NM QRl551 includes three other femora, one of r.vhich is virtually complete and undistorted. As far as can be ascertained, rhe femora are about the same length, but one pair is more massive (Fig. 1.11E-H; cf. Fig.
H
We B
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.t,t.l
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1.12A-D) (measurements given in Table 1.2). The best-preserved femur, 638 mm long, is straight in anterior view and slightly sigmoidal in lateral view (Figs. 1.12A-D; 1.138, H).In these respects it resembles those of other members of the Anchisauria (Fig. 1.1A; -\ttchisaurus, Ammosaurus, Camelotia, and Riojasaurus), as well as Lttfengosdurus, "Gyposaurtts" capensls, and the sauropod Ante-
tonitrus; the femur is straight in lateral view in other sauropods, such as BarapdsdurLts, Kotasaurus, Isanosaurus, Shunosaurus, and \-tilcanodon. The head projects perpendicular to the shaft and posteriorly a shallow sulcus separates it from the rest of the proximal end. The medially directed head does not project from the center of lhe proximal part of the shaft but is shifted anteriorly. In these three respects it resembles the femora of SAM 3450, Riojasaurus and Cunelotia (Figs. 1.13A., G; 1.13D, J, E, K). Lateral to the head, on ihe posterior surface, there is a rounded ridge. The upper part of the :rochanter major is damaged. The anterior (lesser) trochanter is well developed, sheet-like, nore or less parallel to the lateral margin, and partly visible in pos:e rior view, as in Riojasaurus, Camelotia, and Antetonitrus,' it is not -i low ridge as in other prosauropods and sauropods. It is situated some 110 mm below the prorimal end with a quite abrupt proximal :e rmination, but distally it becomes gradually lower and disappears.
Fig. 1.12. Melanorosaurus readi,
NM QR1551. A-D: Left femur tn (A) lateral, (B) anterior, (C) mLdial. and (Dt posterior uteu's. E-H: Right libula in (E) lateral, (F) medial, (G) anterior, and (H) posterior uiews. I-L: Right tibia in (l) Lateral, (J) anterior, (K) medial,
and (L) posterior uieu's. Scale
.50
tntn.
Postcranial Anatomy of Referred Specimens of Melanorosaurus
.
21'
c
D
/-. \ '/ tl{ tl
tl ll
\ .,,
I
\,,,.1I
-
Iqli
t\J\.::
rc
ff\ f*P 5P
{/ \
\il ( ir
Fig. 1.13. Left femora
\
bii,
of
melanorosaurids (A-E, G-K) and Plateosaurus (F and L) in Poslerior tA-lt and medial tC-Lt uiews; (A, G) holotype of tr{elanorosaurus readi, SAM 3450; (8, H) lt{. readi, NM QR/;i/: iC. /l M. thabarren'is. from Gauffre (1993); (D, J) Riojasaurus, from Bonaparte (1972); (E, K) Camelotia, from Gabon (1985); (F, L) Plateosaurus. (F) from Gabon (1990); (L) from Weishampel and Chapman (1990). Scale dpproximately 50 mm.
>--1
ffi
/l
\vi
K
lr9D s
l.t, I
l'\
]{\
1
fI
I.d
l'1 1'
LIJ
\.\
\.l':
(tl"
ffi qh
!l
I
,ll
I
I
\t"/
}$ L
F} 111
axt
i'1
|
i\ { ('\ \I+,\.df
J {t inl ..,,,t !r. ll'1'
I
i:l
\l
J \i'1
Ltr
lt
F
E
\&rdF v
!\ t1 i
.t
#
The lower end of the fourth trochanter is 334 mm below the proximal end of the femur, so it extends to iust below femoral midlength. The fourth trochanrer:length ratio of 52% is similar to rhat of Riojasaurus.The upper end of the trochanter lies on the medial margin of the femur and its lower end is slightly removed from it; such a medial position occurs in Anchisauria (Fig. 1.1A.) and in sauropods. The trochanter is large as in other prosauropods and in Antetonitrus; it is not reduced to a crest or ridge as rn BdrdpasaLrrus, Isanosaurus, Kotasaurus, Shunosaurus, and Vulcanodon.
The medial surface of the trochanter and the adjacent medial surface of the femur are concave. There is also a distinct concavity proximolateral to the trochanter on the posterior surface. Above the fourth trochanter the femur is triangular in cross section, with the lateral margin forming the short base and the medial margin the apex of the triangle. Below the fourth trochanter the femur is elliptical in cross secrion, with the long axis oriented rransversely, as in SAM 3450, RioiaslLtrLts, Camelotia (Fig. 1.13A, D, E, G, J, K), Antetonitrus, and sauropods. However, the ratio of transverse to anteroposterior widths at midlength is 1.2 as against more than 1.5 in sauropods (\X/ilson 2002). The distal end of the femur is expanded medially, laterally, and posteriorly; the distal width exceeds the proximal width of the femur. The posteromedial condyle (pos-
22
.
Peter
M. Galton.
Tacques Van Heerden. and
Adam M. Yates
terior tibial condyle) lies on the medial margin. There is a deep, narrow sulcus between it and the fibular condyle. The sulcus is limited to the posterior surface. It is continued dorsally as a shallor,v depression. Halfway to the fourth trochanter, it passes over obliquely to the lateral side. The anteromedial condyle (anterior tibial condyle) is very incomplete. The fibular condyle is smaller than the posteromedial one. From the former extends a prominent, rounded ridge proximally on the posterior surface. Lateral to this ridge there is a distinct longitudinal concavity that forms a prominent "shelf." Although the surface is abraded, the holotype femur (SAM 3450) of Melanorosattrus readi is more or less complete (Fig. 1.13A, G; Haughton 1924, fig. 45; Van Heerden 1979, fig. 21, pls. 64,65). The femora of SAM 3450 and NM QR1551 are similar in that they are straight in anteroposterior views, with the head directed medially, the distal condyles projecting posteriorln the fourth trochanter on (or very close to) the medial margin in posterior view, and immediately distal to the fourth trochanter. The shaft is roughly suboval in cross section (the anteroposterior width is less than the transverse width). The femur of Riojasaurzs (Fig. 1.13D, J) is similar, except that the lesser trochanter is smaller. Flowever, in Plateosaurauus and Plateosaurus (Fig. 1.13R L), the distal part o{
the shaft is curved in anteroposterior views, so that the distal condyles face posterolaterally, the fourth trochanter is well removed from the medial margin, and the anteroposterior and transverse widths of the subcircular shaft are subequal. Based on a single large femur, Gauffre (1993) described a second species, Melanorosaurus thabanensis, from the Upper Elliot
Formation of Lesotho, southern Africa (Hettangian to Pliensbachian, Lower Jurassic; Olsen and Galton 1984; Olsen and Sues 1986). This femur (Fig. 1.13C, I) differs from NM QR1551 in being slightly more robust, but particularly in that the fourth trochanter is situated away from the medial margin (in posterior view) and extends slightly more distally than in either M. readi or Riojasaurus. Tibia. There are three more or less complete tibiae and the \\reathered proximal end of a fourth (Figs. 1.1OF-I;7.721-L 1.148 1.16J) (measurements given in Table 1.2). These represent two pairs of about the same length, but one pair is slightly more robust Fig. 1.10F, G; 1..1.6J) than the other (Figs. 1.10H, I; 1.12I-L; 1.148). The tibia is 79% of the length of the femur. It is compararir.ely slender and its two ends are mildly expanded compared to Rioiasawrus (Fig. 1.14C, E) and especially to the sauropod Blikanasauras, but still massive compared to Plateosaurzzs (Fig. 1.14D). The proximal articular surface is triangular, the anteromeJral margin forming the long base of the triangle, and it is flat, exrept for the condyles, sloping appreciably posterolaterally. Between :he two condyles there is a shallow sulcus (just behind the lateral :ondyle), which extends over the posterolateral edge onto the pos:crolateral surface. There is a prominent cnemial crest on rhe prox:rnal third of the bone. Lower down it is continued as a rounded
Postcranial Anatomv of Referred Specimens of Melanorosaurus
.
23
ffitr I Fig. 1.11. A-D: Right tibiae in lateral uieu. 14) Melanorosaurus readi, holotype SAM 3,150; (B/ M. readi, NM QR1.5.f 1; /C) Riojasaurus, from Bondpdrte
c)72 ) ; (D ) Plateosaurus, /rorz Gabr,tn (1990). (E) Ri1bt tibia and
(1
fibula oIRit:'jasJurus r/7 anterior uieru, from Bonaparte (1972). (F) Right fibula o/ Melanorosaurus readi, NM QR155l, in lateral uieru. (G) Right fibula of Plateu\aurur irt laterol uiew, lrom Gdlton (1990). H-J: Right dstrdgdlus in proximal uietu of (H) N,Ielanorosaurus readi, NM QRl551; (f Riojasaurus (r.rlrD calcaneum), from Nouas (1989); and (J) Plateosavrus, from Gabon (11)90). K-M: Left metdtdrsdls of Melanorosaurus readi, NM 8R/J51. (K. Lt llin tKt posterior and (L) lateral uieus; (M) lll in medidl uietu. N-O: Anteriur uiew of left pes o/ /N/ Riojasaurus, from BondpLlrte (1972), and (O) Plateosaurus, from Galton (1990). Scalc dpproximatelv .50 mm.
"11
o I ii
L$ &J
m
/ I' ii f l
ci{rl
{* ,'[i
rll ltl
Ir
1I
ilT{
u
t..'h
'J KL
r_.#
fl Tf,l
*s
ridge that extends to the medial margin of the bone. The distal third of the tibia is triangular in outline; the anterior surface is flat, and the medial and posterolateral surfaces are rounded. The distal end has the usual sauropodomorph configuration, with a prominent descending process that fits a corresponding depression in the astragalus. The lateral margin of the descending anteroventral process of the distal tibia protrudes lateraily as far as the anterolateral corner as in prosauropods (Fig. 1.12L) rather than being set well back from it as in Antetonitrus and sauroDods (Yates and Kitching 2003).
The holotype tibia (SAM 3449; Fig. 1.14A; Haughton 1.924, fig. 45; Van Heerden L979, fig.22, pls. 66,67) is somewhar more robust than that of NM QR1551 (Fig. 1.1a8). Like the femur, the
holotype tibia is weathered and the distal end is incomplete. Fibwla. There is a fairly complete right fibula (Figs. 1.12E-H; 1.14F) and the proximal half of a left one (Fig. 1.16K) (measurements given in Table 1.2). The prorimal end is flattened and has
24 .
Peter
M. Galton,
Jacques Van Heerden, and Adam
M.
Yates
Wff
ww
w cg
wffi, ffi &
w
Iq
&
H
w
KffiW
n
Y
W
ww
broad anteromedial and posterolateral surfaces. The latter is rounded, whereas the former has a knoblike elevation in the middle, with a shaliow groove on either side. The proximal half of the shelf is elliptical and the distal half subcircular in cross section. The distal end is less expanded than the proximal one. The posterolateral surface is slightly rounded, whereas the anteromedial surface has a distinct sulcus that becomes narrower proximally. Near the distal end the sulcus width is more than half that of the 6bula and
is confluent with a transverse groove just proximal to the distal condyle. The condyle itself is placed medially, as in PlateosdLtrus
(Fig. 1.14G). Tarsals. The only proximal tarsal represented are two right astragali, one well preserved (Figs. 1.14H; 1.15A-D) and the other weathered. It is a rounded, disk-like bone that articulates with the distal end of the tibia. In form it is similar to those of Rioiasaurus and Plateosaurws (Fig. 1.14I, J, N). The medial half of the dorsal surface is slightly concave, with the anterior margin turned dorsally. There is a very robust ascending process, with a rvelldeveloped excavation posteriorly that articulates with the descending process of the tibia. The astragalus thus closely interlocks with the tibia as in all sauropodomorphs. Anteriorly there is a fossa at the base of the anterior surface of the ascending process. A vascular ioramen is present here in prosauropods and Blikanasaurus (SAM K403), but it is lost in Vwlcanodon and other sauropods (Wilson :rnd Sereno 7998). The condition rn Melanorosaurus is unknown because matrix still fills the area. The lateral surface of the astragalus is slightly higher than broad, and there is a shallow concavity
W
Fig. 1 .15. Melanorosaurus readi,
NM QR1.t.t1. A-D: Right astragalus in (A) anterior, (B) proximal, (C) posterior, and (D) distal uiews. E-F: Distal tarsals in (E) proximal and (F) distal utea,s. G-H: Distal pdrt of left metdtarsdl IV in tGt lateral and tHt postcrior uiews. l-K: Left metatarsal lll in (I) medidl, (J) anterior, and (K) lateral uiews. phalanges
in
L-Q:
Pedal ungual
(1., P) dorsal and
(M-O and Q) side uiews. Scale is 50 mm.
Postcranial Anatomy of Referred Specimens of Melanorosaurus
'
25
TABLE 1.3. Measurements (in mm) of Metatarsals of Melanorosawrus readi
(NM QR1ss1) MT I (1) MT I (2) MT II t29 t20 180
Description Length
\fidth of proximal
MT III 225
70
a/
65
29
31
.)L
z5
69
63
59
63
surface
76
\)(/idth of proximal surface
(parasagitally) (para-rransversely
)
\fidth of distal end (
para-transversely)
where the calcaneum abutted against it. The ventral surface of the astragalus is strongly convex anteroposteriorly. A single, distal tarsal is known for Melanoroslurus, but not
from which side of the bodn nor if it was the only one present. The distal tarsals of Riojasdttrus are in articulation (Fig. 1.14N), thus limiting what can be seen, and those of the saurop od Blikanasdurus are poorly preserved (these elements are absent or unossified in other sauropods; \(ilson 2002). The distal tarsal of Meldnoroslurus has a gently convex proximal surface (Fig. 1.15E) and is mostly concave distally, with a more strongly concave part with a large foramen (Fig. 1.15F). The convex edge is sharp, whereas the opposite concave edge is beveled and pierced by another foramen (Fig. 1.1sE). Metatarsdls. There are remains of two metatarsals
I and one metatarsals II and III, and the possible remains of metatarsal IV (Figs. 1.SJ-L; 1.14K-M; 1.15G-K; 1.16A-D) (measurements given in Table 1.3). The metatarsals are similar to those of Rioiasaurus, Plateosaurus (Fig. 1.14N. O), and Pldteosaurauus, but are much less massive than those of the early sauropods Antetonitrus and B likanasaurus. One of the right metatarsals I (Figs. 1.8J-L) is slightly larger and more weathered than the other. The proximal end surface is elIiptical. The posterolateral surface, which abuts against the proximal end of metatarsal II, is divided into two subequal halves: the larger, aimost flat surface faces posterolaterally, whereas the smaller, flat surface faces laterally. The metatarsal is slightly constricted about two-thirds from the proximal end and broadens distally. The each
of
lateral distal condyle is much larger than the medial one, so that the first digit was directed anteromedially as in prosauropods (Galton and Cluver 1976). The proximal articular surface of left metatarsal II (Fig. 1.16A-D) is hourglass-shaped, with concave long sides an' teromedially and posterolaterally, whereas the other two sides are short and straight" All four surfaces of the proximal third are longitudinally concave. The largest and deepest of these concavities is the
26.
Peter
M. Galton,
Jacques Van Heerden, and Adam
M.
Yates
€
:'r
,
,h,l ut, !{lr,
;,,,
W
c
i|[
ffi
,''.St"'
llirl&r
Fig. 1.15. N{elanorosaurus readi,
NM QR15i1. (A-D:) Left
";$, k: ,.
I
,w
fr-*re ru ru
metatarsal II in (A) mediaL, (B) anterior, (C) lateral, and (D1 posterior uietus. E-C: Problenl bone in three uiews. H-l: Phalanx tprohahly digit lVt in tHt anteriur and (l) side uiews. (J) More massiue left tibia in lateral uietu. (K) Proximal part of left fibula in medial t icu'. Scalc is \o mrn.
anteromedial one. The shaft is short without being stocky. Distally, the lateral condyle is slightiy larger than the medial one. Metatarsal III is complete, but weathered (Figs. 1.14M; 1.15I-K). It is 36% of the length of the femur. The proximal articular surface is triangular,
rvith the apex of the triangie directed posterolaterally. The medial long side is slightly concave and the posterolateral long side is straight. The medial surface of the proximal end has a triangular concavity, whereas the anterior surface has a much smaller, circular concavity. The posterolateral surface is subdivided into a smaller, concave posterior part and a rounded lateral part. The shaft is comparatively long, slender, and subcircular in cross section. The two distal condyles are of equal size, but the lateral one proiects farther distalll'. The left metatarsal IV is incomplete proximally and poorly preserved (Fig. 1.15G, H). Phalanges. There are thirteen disarticulated phalanges, five of rvhich are unguals (Figs. 1.15L-Q; 1.16H, I), but it has not been possible to reconstruct any digit with certainty. Most of the phalanges are the same shape as in other prosauropods, such as Rioidsaurus and Plateosdurus. (Fig. 1.14N, O). However, some ot them are broader transversely than they are long anteroposteriorln Postcranial Anatomy of Referred Specimens of Melanorosaurus
.
27
as in Camelotia and sauropods including Blikanasaunzs. The unguals vary in size from rhe very large rrenchanr ones, which proba-
biy belonged to the first digit of the manus, to the less trenchant, smaller ones found on the outer digits of the pes (Fig. 1.1L-Q). Discussion Sacral types. Comparisons with
NM QR1551 (Fig. 1.6A) indi-
cate that the three cenrra illustrated by Van Heerden (1979, pls. 58,
59, 60) are those of sacral vertebrae 1 and 2 (with most of left rib) and a possible proximal caudal of Plateosaurauus. Comparisons with Plateosaurus and other prosauropods (Gaiton 1999, 200Ia, 2001b) indicate that the sacrum of Plateosaurauus probably had the derived prosauropod sacrum with three vertebrae, namely, sacral vertebrae 1 and 2 (Van Heerden 1979: figs.7,9, pIs. 13, L6, 17) with a dorsosacral (Van Heerden 1979: fig. 8, pls. 74, 15; misidentified as the third sacral, a caudosacral, see Galton 2001b); Novas \1996) came to the same conclusion for Riojasaurus (Fig. 1.6E). In prosauropods, the plesiomorphic condition of rwo sacral vertebrae are supplemented by a third, which can be incorporated from either the tail (S1 + 52 + CS as in Plateosaurus) or from the dorsal series (DS + 51 + 52 as in Massospondylzs) (Galton 1999, 2001b). The basal sauropodomorph Saturnalia (Santa Maria Formation, Upper Triassic, Brazil) has incorporated a caudosacral into the sacrum (Langer etal. 1999), as was probably also the case for the basal sauropodomorph Thecodontosaurus (Norian, Upper Triassic, England; Galton 1999;Benton et al. 2000). A cladistic analysis of the Prosauropoda (Galton and Upchurch
2004) indicates that a sacrum with a caudosacral (S.l + 52 + CS) represents the plesiomorphic state for the Prosauropoda, whereas a sacrum with a dorsosacral (DS + 51 + 52) represents rhe synapo, morphic state. However, a detailed cladistic analysis shorvs that the history of the sacrum in prosauropods is complicated (Galton and Upchurch 2000, Galton and Upchurch 2004; for figures of sacra see Galton 1999). Apart from Melanorosaurus, the only other prosauropod in which there were previously thought to be four sacral vertebrae is Massospondylus (as DS1 + 51 + 52 + CS, Cooper
1981). However, Galton (1999) reinterpreted the sacrum, suggesting that DS1 is probably an unmodified dorsal, 51 is a modified dorsal, and 52 and CS represent the two reptilian sacral vertebrae. This results in the sacrum being DS1 + 51 + 52, a concluslon confirmed by undescribed sacra of Massospondylus (BPI, Vasconcelos, pers. comm.). Basal sauropods have four sacral vertebrae but this represents a convergence, the extra vertebra being another caudosacral ('!7ilson and Sereno 1998;'Sfilson2002). so rhe sacrum is 51+52+CS1+CS2. Relationships o/ Melanorosaurus readi
The absence of a skull and manus and the incompleteness of the pes, the sources of many character states used in cladistic analy-
28 .
Peter
M. Gahon,
Jacques Van Heerden, and Adam
M.
Yates
of the Sauropodomorpha, greatly reduce the number of characters available to classify Melanorosdurus. The synapomorphies used to place Melanorosaurus within the cladogram (Fig. 1.1A) are based on the cladistic analysis of Galton and Upchurch (2004). NM QR1551 is referred to the Sauropodomorpha (Node 1) because the large ascending process of the astragalus keys into the distal articular surface of the tibia (Fig. 1.15A-C; tibia SAM 3449, Fig. 1.14A).It is a prosauropod (Node 2) because the centra of the posterior dorsal vertebrae are elongate (length:height ratio is greater than 1.0, Fig. 1.4A), the posterior dorsal vertebrae lack a prezygodiapophyseal lamina (Fig. 1.4A), and the pubis has a large obturator foramen (Fig. 1.10C-E). It is referred to Node 3 (unnamed) because the deltopectoral crest terminates at or below the midlength of the humerus and the distal end of the ischium is expanded dorsoventrally (Fig. 1.11B). Referral to Node 4 (unnamed) is based on the acetabulum not being backed medially by a sheet of bone (Fig. 1.10A; SAM 3449, Haughton L924,frg.44),the subtriangular outline to the distal end of the ischium (Fig. 1.11A-C), and the increased robustness of metatarsals II and III (Figs. 1.151-K; 1.16A-D). NM QR1551 is referred to the Anchisauria (Galton and Upchurch 2004) (Node 5, Fig. 1.1A) because the forelimb:hindlimb length ratio is greater than 0.60, the obturator foramen is completely visible in the anterior view of the pubis (Fig' 1.10E), the femoral shaft is distally straight in anteroposterior views (Fig, 7.1,28, D; 1.13B; SAM 3450, Fig. 1.13A), the fourth trochanter of the femur is displaced to the posteromedial margin of the shaft (Fig. 1.12D; 1.138; SAM 3450, Fig. 1.13A), and the proximal end of metatarsal II is hourglass-shaped. NM QR1551 and SAM 3449 are referred to the Melanorosauridae Huene 1929 (Node 7,Frg. 1.1A) because of the following apomorphies: the ilia have a step-like sigmoid profile to the dorsal margin in lateral view (Figs. 1.9A;1.10A) and, for the femora, the proximal and lateral margins meet at an abrupt right angle in anterior view (Fig. 1.128, C; SAM 3450). The lesser trochanter is a prominent, sheet-like structure (Fig' 1.12A' B; also SAM 3450 but eroded), which projects beyond the lateral margin of the femur so that it is visible in posterior view (Figs' 1'.12D; 1.13B; SAM 3450), the distal end of the fourth trochanter lies at or below femoral midlength (Figs. 1.11F; 1.12A, C, D; 1.138; SAM 3450, Fig. 1.13A, G), and below that the shaft is transversely rvidened and anteroposteriorly compressed (Figs. 1.12A, C; 1.13H; cf. Figs. 7.128, D; 1.13B; SAM 3450, Fig. 1.13A, G). NM QR1551 is referred to Node 8 (unnamed lCdmelotia + Melanorosaurusl) because the proximal caudal centra are high relative to their axial length (Fig. 1.5B, C) and at least some pedal phalanges, ercluding unguals, are broader transversely than their proximodistal length (Fig. 1.16H,I). An autapomorphy for Melanorosattrzs (NM QR1551) is a dorsosacral as the fourth sacral vertebra, so the sacrum is DS1 + S1 ses
Postcranial Anatomy of Referred Specimens of Melanorosaurus
'
29
+ 32 + CS. The sacrum of Massospondylus was rhoughr to consist of four vertebrae but, as noted above, several undescribed sacra show that it is DS + 51 + 2. The sacrum of NM QR1S51 differs from those of sauropods in which the extra sacral is a caudosacral (Wilson 2002), so the sacrum is 51 + 52 + CS1 + CS2 (Galron 1999\.
NM QR1551, however, does not possess the following synapomorphies of the Anchisaurudae Marsh, 1885 (Node 6, Anchisaurus and AmmosdLtrus, Fig. 1.1A), the sister group to the Melanorosauridae (Galton and Upchurch 2004): the iength:height ratio of
the longest post-axial cervical centrum is at least 3.0 (2.0, Fig. 1.3A), the deltopectoral crest terminates above 50% of humerus length (below midlength, Fig. 1.8D, E), the anterior process of the ilium terminares in front of the distal tip of the pubic process in lateral view (or rather behind it, because the process is short; Figs. 1.9A; 1.10A; SAM 3449,Haughton 1,924, fig. 44), and the area between the anterior and pubic processes of the ilium is acute in lateral view (not acute, Figs. 1.9A; 1.10A; SAM 3449, Haughton 1924, fig.44). NM QR1551 also lacks the following synapomorphies of the Plateosauria Tornier 1913 (Node 10, Fig. 1.1A), the sister group of the Anchisauria (Galton and Upchurch 2004). The length:height ratio of the longest post-axial cervical centrum is at least 3.0 (2.0, Fig. 1.3A) and the sacrum consists of a dorsosacral plus sacral vertebrae 1 and 2 with loss of the caudosacral (piesiomorphic caudosacral retained in the sacrum, Frg. 1.6A). The characters of the Sauropoda have been discussed by Wilson and Sereno (7998), Upchurch (1998), Sereno 11.199), and mosr
recently by rWilson (2002). Of the twenry-one synapomorphres listed by Wilson (2002), seven refer to elements nor preserved in NM QR1551. As in sauropods, the humerus-to-femur ratio is 0.70 or more (0.71) and the femoral midshafr is elliptical in crosssection but the rransverse diameter is only about I20"h of the anteroposterior diameter, not at least 150% as in sauropods. The
basal saurop ods Barapasdurus, Kotasdwrus, and Shunosaurus have
four sacral vertebrae, a synapomorphy for Sauropoda (Upchurch 1995; \iliilson and Sereno 7998; \flilson 2002\. but the additional sacral vertebra of NM QR1551 (Fig. 1.6A, B) is a dorsosacral, not a caudosacral as in Sauropoda (\X/ilson and Sereno 1998; Wilson 2002). Unlike the situation in sauropods, the posture of NM
QR1551 was probably nor that of a columnar, obligate quadruped; the base of the anterior caudal transverse processes is shallow, not
deep (Fig. 1.5D, F); the incomplete deltopectoral crest of the humerus is large, not reduced to a low crest or ridge (Fig. 1.8D-F); the proximai end of the ulna (Fig. 1.SG-I) lacks three sauropod characters (triradiate with deep radial fossa [appears to be subtriangular], ulnar proximal condylar processes unequal in length with anterior arm longer [unknown, forearm incomplete], olecranon process reduced or absent [large]); the ischial peduncle of the ilium
30.
Peter
M. Galton,
Jacques Van Heerden, and Adam
M.
Yates
is deep (Figs. 1.9A; 1.10A), not low; the distal ischium is triangular,
not bladelike (Fig. 1.11A-C); the fourth trochanter of the femur is large (Figs. 1.11E, F; 1.12C, D), not reduced to a crest or ridge; the vascular fossa at the anterior base of the ascending process of the astragalus is not lost (Figs. 1.14H;1.15A, B; foramina hidden by matrix in fossa); and there is an ossified distal tarsal (Fig. 1'15E' F); but present in BlikanasaurLts, a sauropod sensu (Upchurch et al. 2004\.
In Yates (2003a), Ancbisawrus and Meldnorosaurus are Prosauropoda in their traditional position outside of the Sauropoda (Fig. 1.1,{; e.g. Gaiton 1990; Sereno 1999; Benton and Storrs in Benton et al. 2000; Upchurch 1995,1998; Upchurch et aL.2002; 'Wilson and Sereno 1998, Wilson2002). However, Yates and Kitching (2003) include these genera in a modified concept of the Sauropoda (Fig. 1.1B; also Yates 2002), but the reasons for this change are yet to be published (Yates in press b). Yates and Kitching (2003: electronic appendix A) list seventeen unambiguous synapomorphies for Sauropoda, but onlv three of these characters involve bones preserved in NM QR1551, namely, the loss of a strong constriction between the transverse process and the sacral rib of sacral vertebra 1 (vs. constriction stiil present' Fig. 1.4H), reversal to a humerus with a transverse width of the distal end that is less than 33% of the length (vs. present, 24'/.), and a distal end of the tibia with a posteroventral process that does not extend as far laterally as the anterolateral corner (vs. no, prosauropod condition in which it projects at least as far, Fig. 1.L2J,L; coded as a sauropod because Yates previously only saw the incomplete tibia of NM QR1551)' Two of the three sauropod synapomorphies with DELTRAN of Yates and Kitching (2003) are for bones preserved in NM QR1551, namely, loss of semicircular fossa on the distai flexor surface of the humerus (vs. vague fossa present, not as flat as in sauropods and not sharp-edged as in prosauropods, but the distal surface is a little eroded; Figs. 1.7E; 1.8D) and the fourth trochanter is on the medial margin of the femur in posterior view (present, Figs. 1.12D; 1.138; SAM 3450, Fig' 1.13A). Only five of the twenty-five character states for the sauropod synapomorphies with ACCTRAN of Yates and Kitching (2003) involve bones present in NM QR1551, namely, reversal to a scapula blade rvith a midsection that has parallel margins (vs. present, Figs' 1.7B; 1.8A), reversal to a deltopectoral crest that extends to less than midlength (no, beyond midlength, Fig. 1.8D, E). For the proximal condyles of the ulna. the anterior process is much greater than the lateral process (not known as lateral process incomplete), and the transverse width of the ischial shaft is greater than its depth (vs' no, the re-
of the fourth trochanter of the femur is not rounded and symmetrical (asymmetrical' Figs. 1.11E, F; 7.IzC) as in sauropods. Yates and Kitching (2003) list four unambigous synapomorphies for the next node (Melanorosdurus + the rest' Fig. 1.1B), all
verse, Fig. 1.11A-C), and the profile
of which involve
bones present
in NM QR1551,
namelS the
Postcranial Anatomy of Referred Specimens of Melanorosaurus
'
31
dorsoventral height of hyposphenes equal to thar of the neural canal (present), and reversal to tall dorsal neural spines that are greater than 1.5 times the length of their bases (not the case but only one dorsal with a neural spine, Figs. 7.2E; I.3E). The sacrum includes a caudosacral vertebra (present, Fig. 1.6A, D), and there is a deep radial fossa on rhe proximal ulna (it appears to be subtriangular in NM QR1551, present in SAM 3449).
Yates and Kitching (2003) list thirty-three synapomorphies with ACCTRAN for this node, but only four of these characteis relate to bones preserved in NM QR1551, namely, loss of the free tip from epipophyses of all postaxial cervicals so epipophyses are joined to postzygapophyses along their length (present, Figs. 1.28; 1.3A), with a minimum width of the scapular blade greater than 20"/. of its length (present, 23ok,Figs.1.78; 1.8A), anreroposrerior length of distal pubic expansion is greater than 15% of the length of the pubis (vs. no, 1.2o/o, Fig. 1.10D), and a crestlike lesser trochanter on the femur with height exceeding basal width (present, Fig. 1.12A, B). The referred specimen NM QR1551 of Melanorosdurus is a prosauropod according to the analysis of Galton and Upchurch 1in Upchurch et aL.2002; Upchurch et al. 2004). Based on the synapomorphies given by V/ilson (2002), it is not a sauropod (Fig. 1.1A). However, this specimen is placed within a redefined Sauropoda as the sister group of the rest of the Sauropoda (Fig. 1.1B) by yates and I(itching (2003; also Yates in press b), but, based on the dererminable character states, NM QR1551 lacks several synapomorphies for both of these nodes. A more detailed cladistic analysis of the basal Sauropodomorpha is being prepared by Upchurch, Bar, rett, and Galton (in prep.). In addition, a more detailed analysis of
NM QR1551, NM QR3314, and the original material
of
Melanorosaurus (SAM 3449,3450,3532) of Haughton (1924) is being undertaken by Yates, Van Fleerden, and Galton (in prep.). It is hoped that these studies will clarify the systematic position of
Melanorosaurus readi that,
for the moment, is
referred
to
as
Sauropodomorpha incertae sedis. Acknowledgments. Jacques Van Heerden thanks Teresa Bos-
well (NM) for the drawings of Melanoroslurus. Adam M. yates thanks Elize Butler and John Nyaphuli (NM) and Sheena Kaal (SAM), for assistance with the collections; earlier, Anusuya Chinsamy-Turan (formerly at SAM, now ar University of Cape
Town, South Africa) kindly provided information and photographs of Haughton's material. Peter M. Galton thanks Michael euinn and Joseph Souza (University of Bridgeport) for printing the photographs.'We thank Cecilio Vasconcelos (BpI) for providing information on the sacrum of Massospondylus and appreciate the useful comments made by the editors and especially those by paul M. Barrett (The Natural History Museum, London, England), who provided excellent detailed reviews of the different versions of this paper.
32.
Peter
M. Galton,
Jacques Van Heerden, and Adam
M. yates
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Postcranial Anatomy of Referred Specimens oi Melanorosaurus
.
37
2. The Genus Barosaurus Marsh ( Sauropoda, Diplodocidae) JonN
S.
McINrosH
Abstract The sauropod genus Barosaurus, which was long thought to be rare (in North America at least), is shown to be relatively common. Four partial skeletons (in addition to the holotype) are described, one of which also possesses the greater part of the appendicular skeleton. Barosaurus is closely related to Diplodocws and to the African species Gigantosaurus africanus Fraas, referred to Barosaurus by Janensch. The latter relationship is discussed briefly at the end of the paper, but the diagnosis of Barosaurzs presented here derives solely from the American species B. lentus Marsh. The three diplodocids from North America-Diplodocus, Barosaurus, and Apatosaurus-share the following postcranial characters (in contrast to CamarasaLlrLts, Bracbiosaurus, Haplocanthosdurus, etc.): (1) an increase in the number of cervicals at the base of the neck by cervicalization of the most anterior dorsals, (2) a deep, "V"-shaped cleft in the presacral spines in the shoulder region, (3) vertebral spines very high and slender in the sacral region, (4) anterior caudals with winglike transverse processes resembling sacral ribs, (5) median and posterior caudals elongated, and a 38
whiplash at the end of a very long tail (80 + vertebrae contrasted
with the usual 50+), (6) median and posterior chevrons developing an anterior extension in a typical Diplodocus pattern, (7) a marked shortening of the forelimb, with the humero-femoral length ratio = 2/s (compared to the typical 3/ra/s), (8) relatively short metacarpals, (9) an absence of a calcaneum, (10) the presence of lobe on the rear-lower corner of the lateral face of metatarsal I, (11) the longest metatarsals III and IV (rather than II and III in Camarasaurus, Brachiosarus, etc.), and (12) an expanded distal end of ischium. Diplodocus and Barosaurus differ from Apatosaurus in (1) overall lightness of the skeleton, (2) much longer cervical vertebrae,
with much lighter cervical ribs, (3) winglike, caudal
transverse
tail, (4) possession of pleurocoels on the anterior caudal centra, (5) ventral scuipturing of the anterior and anteromedian caudal centra, (6) much greater development of the typical diplodocoid chevrons, (7) pronounced lightness of the limb bones, particularly in contrast to the very robust forelimbs in Apatosaurus, and (8) possible retention of two carpals in contrast with one in Apatosaurus. The characters that separate Barosaurus from Diplodocus are derived almost totally from the vertebrae. The cervicalization of the presacrals, which results in fifteen cervicals and ten dorsals in Approcesses extending much further back in the
atosdurus and Diplodocws, reached its extreme in Barosaurus, where the number of dorsals was nine (or possibly eight). The cervicals are enormously elongated, fully 50% longer than those of Diplodocus in the postmedian part of the neck. The tops of the caudal spines, of which the first eight or nine bear notches in Diplodocus, are {l,at in Barosawrus. The winglike transverse processes and pleurocoels do
not persist as far back in the tail of Barosaurus. The tail itself is shorter. Although the number of caudals is unknown, the ratio of the sum of the lengths of the first twenty caudals to that of the ilium is 4.8 in Barosaurus and 5.6 in Diplodocus. Few chevrons are known to exist in Barosaurus, and their development may have been somewhat less extreme than in Diolodocus.
Introduction The genus Barosaurus (Sauropoda, Diplodocidae) was established by Marsh in 1890, but now, over one hundred years later, it is still not well understood. If reference to the genus of material from East Africa is disregarded, only one substantial, comprehensive treatment of the genus has appeared since the original descriptionnamely, Lull's 1919 memoir on the type specimen. There are six well-established Morrison sauropods, and it is widely assumed
that three were common-Camarasaurus, Diplodocus, and Apcttosdurus-and that three were rare-Haplocanthosaurus, Brachiosaurus, and Barosaurus. As will be shown, Barosaurus was far from rare, and several new skeletons will be described. lnstitutional abbreuiations. AMC-Amherst College Museuml AMNH-American Museum of Natural Historv: BMNH-The The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
. l9
Natural History Museum, London; CM-Carnegie Museum of
Natural History; DINO-Dinosaur National
Monumentl
DMNH-Denver Museum of Natural History; HMB-Museum fiir Naturkunde der Humboldt Universitdt Berlin; HMNS-Houston Museum of Natural Science; ROM-Royal Ontario Museum; SDSM-South Dakota School of Mines; USNM-National Museum of Natural History; UT-University of Texas; YPM-Yale Peabody Museum; and YPM-PV-Yale Peabody Museum, Princeton University Specimens.
History of Discoveries During the summer of 1889, Professor O. C. Marsh made one of his periodic trips to the 'Western United States. He visited J. B. Hatcher, who was collecting spectacular Triceratops skulls from the Upper Cretaceous in the Lance Creek area in Wyoming. Hatcher had learned of the discovery of dinosaur remains in the Black Hills of South Dakota, a hundred miles to the northeast. Marsh and Hatcher proceeded to the site, located one-half mile east of Piedmont, where they spent several days collecting part of the tail of a skeieton that was discovered by Mrs. E. R. Ellerman on land owned by Mrs. Rachel Hatch. Before leaving, Marsh obtained the promise of these two women to protect the remainder of the skeleton until he could send someone to collect the rest of it. Two boxes (Yale Accession number <2054>), containing six caudal ver-
tebrae and a chevron, arrived in New Haven on November 4, 1889. The bones were immediately prepared for study so that Marsh could include a brief description in a paper submitted on Decenrber 21, 1889 (Marsh 1890). The specimen was assigned to a new genus and species of sauropod, Bctroslurus lentus. Marsh noted that it resembled Diplodocus, but differed from that animal by the possession of deep pleurocoeis in the caudal centra, relatively shorter caudal centra, and a lack of anterior extension of the chevrons characteristic of Diplodoczs. As will be shown below, most of these supposed differences arose from the comparison of more anterior caudals of Barosaurlzs with posterior ones of Diplodocus.
No further attempt was made to collect the rest of the skeleton until nine years later, when Marsh sent George \X/ieland to South Dakota (Wieland 1920). Wieland arrived in Piedmont on August 10, 1898.'When he learned that Mrs. Ellerman had died in 1895, he secured the help of her daughter in retrieving fragments of the skeleton that had been carried off by various people during the intervening years. Proceeding south and west from where Marsh and 'S7ieland
Hatcher had worked, collected during the next two months seven more caudals, fragments of the sacrum, seven dorsals, four posterior cervicals, a number of ribs, several chevrons, a sternal plate, and most of the right pubis. These were sent in sixteen boxes to New Haven (Yale Accession numbers <2438>, <2444>, and <2457>). Sent with them were a number of fragments
49 .
John S. Mclntosh
from a different site in the area referred to as possibly belonging to Barosaurus (?) II by Wieland in his letters to Marsh. Among these were fragments of a femur, tibia, coracoid, and scapula. Although later attributed bv Lull (Lull 1919) to the Barosaurzrs skeleton, these fragments almost certainly do not pertain to it, and there is no reason to believe that they even belong to Bdrosaurus. Before obtaining this new material, Marsh referred briefly to Bctrostturtts in his memoir Dinosaurs of North America (Marsh 1896), placing it in the Atlantosauridae rather than the Diplodocidae. Then in 1898, l-re visited the American Museum of Natural History and observed the partial skeleton of Diplodoczs that H. F. 'Wyoming (Osborn 1899). Osborn had collected at Como Bluff, From this visit, he r,vas able to correct some misconceptions he had of Diplodoozs based on material from Colorado. Shortly thereafter, the \X/ieland material arrived in Nelv Haven, allor,ving Marsh to write one of his last papers (Marsh 1898), in which he corrected his diagnosis of the Diplodocidae and moved Bdrosaurus into it. In his very last paper submitted several months later, which rvas devoted to dinosaur footprints collected in the Black Hills, Marsh included a single sentence stating, "\Vith these remains [the rest of the Barosaurzs skeleton collected by Wieland] were found remains of a much smaller species, which may be called Barosaurus affinis" (Marsh 1899,228). His death less than a month later precluded any further statement on this species. It was not until twenty 1-ears after Marsh's death that the Barosdurus skeleton was fully prepared for study and description by R. S. Lull (Lull 1919). Lull determined that two small "metacarpals" found among the miscellaneous fragmentary material collected by Wieland must be the "smalier species" that Marsh named Barosaurus affinis.In the meantime E. Fraas (Fraas 1908) had described two sauropod specimens from East Africa as two new species of a new genus Gigantosaurus. One of these, G. africantts,
resembled Diplodocus
and was
subsequently referred to
Barosdwrus by Janensch (1922). In later papers, Janensch gave detailed descriptions of the skull parts (Janensch 1.935-1936) and bones of the appendicular skeleton (Janensch 1.961.) of several specimens he referred to this species. He also established a nerv subspecies, Barosaurus africanus gracilis for some very slender limb elements (Janensch 1961,). In another part of the rvorld, Earl Douglass was engaged by the Carnegie Museum of Natural History to excavate the magnificent quarry north of Jensen, Utah (now Dinosaur National Monument). A fine, articulated skeleton of Diplodocas, field #150 (now DMNH 7492), had been located at the end of the 1912 field season, and some disarticulated cervical vertebrae found near the dorsais were assumed to go with them. With so man,v specimens in the quarry', it was not until two years later that Douglass got around to fully uncovering these vertebrae, and he found to his amazement that they were over three feet long. This, coupled with the fact that the artic-
ulated Diplodocus cervicals extended from the front of the dorsal The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
.
41
series of #150, made it clear that the huge cen'icals belonged to a different individual, and they were assigned field #1508. In a letter to \X/. J. Holland (November 78,1974), Douglass speculated that the elongate cervicals might belong to Barosaurzs. This was a remarkable observation, because up to that time there was nothing in print to indicate that Barosaurushad a very long neck. In his annual report (March 31, 1915), Holland mentioned the "huge sauropod" but did nor try to identify it. These elongate cervicals (CM 1198) probably belong to a partial skeleton, field #155 (now ROM 3570), which was originaliy identified as Diplodocus. Several years later, Douglass made a diary entry on October 17, 1918, mentioning another long-necked sauropod (field #310), which he again suggested might be Barosaurus, but later questioned whether it might not be "Brachysaurus" [slc]. By this time, Lull had presented an oral paper attesting to the long neck of Barosaurus (Lull 1917). However, on receiving Lull's memoir (Lull 1919) on Barosaurus, Douglass wrote to Holland on February 14, 7920, confr,rming that #310 (now CM 77984) was indeed Barosaurus, and this information was published by Holland in his annual report on March 31, 1920. Surprisingly, when Gilmore published the map of the Dinosaur National Monument quarry in 1936, he misidentified the specimen as "?Brachyosaurus" (but in
all fairness it must be stated that he never saw the specimen because had not been prepared at that time). This fine specimen was finally worked out in relief by Allen McCrady in the 1970s and
it 1
980s.
In 1979, the death of Andrew Carnegie, the source of the financing of this very expensive operation, signified that quarry work would terminate soon. The easternmost part of the quarry, which was just then being worked, was producing the finest series of articulated skeletons. It was decided to take out only those skeletons needed for mounting in Pittsburgh and to leave the rest for other institutions. Among the latter group were two fine skeletons, #340 and #355, thought at the rime to be Diplodoazs. The National Museum of Natural History expressed interest in obtaining one of these, and Douglass intended to collect the other for the University of Utah, whose staff he now joined. Gilmore arrived from Washington, D.C., in the summer of 1923, and decided to collect #355. This was a splendid skeleton, but when it was discovered that the skull, cervicals, and orher parts had weathered awa5 the new director of the Carnegie Museum, Douglas Stewart, and Gilmore arranged to supplemenr the skeleton with parts from #340, including the cervicals. This placed Douglass and the University of Utah in a difficult position, but he cooperated fully with Gilmore and turned over to him the grearer part of the cervicals from #340, which the Carnegie Museum had already taken out. After the National Museum field crew had completed their work, the University of Utah party under Douglass proceeded to collect the rest of #340, which consisted of most of the dorsal vertebrae and ribs, the pelvis, the sacrum, the tail, and one hindlimb, but
42
.
John
S.
Mclnrosh
lacked the cervicals, anterior dorsals, pectoral girdle, and humerus, which had gone to $Tashington, D.C. The skeleton was prepared, but it was never mounted at the University of Utah. Ironically, when the cervicals were finally prepared in \Tashington, D.C., what had been thought to be two cervicals in the field was in reality one long cervicai. Thus the cervicals reaily belongedto Barosaurus and were thus of no use for the mounted Diplodoctts skeleton (Gilmore 1932). The latter skeleton, USNM 10865, was completed with casts of the cervicals of Diplodocus carnegii (CM 84) and went on
display in 1932.
Barnum Brown nolv entered the picture. After a trip to Salt Lake City in 1929 to evaiuate the University of Utah collection, Brown managed to arrange trades with the National Museum of Natural History, the University of Utah, and the Carnegie Museum of Naturai History (where a section of the tail had been sent previously), and so he was able to unite the Barosaurus skeleton in New York City. The American Museum of Natural History, which had done no work in the quarrl', ended up with one of its most important specimens (AMNH 6341). A cast of the skeleton was recently mounted in the American Museum of Natural History by Research Casting International. In a spectacular but controversial pose, the Barosaurus is shown rearing up on its hind legs to a height of over fifty feet, protecting its young from a marauding Allosdurus. Further Barosaurws material from South Dakota has been reported by John Foster (1996). It is now apparent that, far from being rare, Bdrosattrus is really a common Morrison sauropod. The limb bones are in many cases indistinguishable from those of Diplodocus and many of those previously identified as belonging to that genus undoubtedly belong to Barosauras. This paper will concentrate on a description of AMNH 6341, supplemented by CM 1,1.984 and other specimens. The characterization of Barosaurus is strictly limited to North American specimens. The status of the East African material will be discussed at the end. Systematic Paleontology Order Saurischia Suborder Sauropoda
Family Diplodocidae Marsh Genus Barosaurus Marsh 1890 Barosaurus lentus Marsh 1890 Synonym. Barosaurus affinis Marsh 1899 Type specimen. YPM 429: 31/z cervicals, 6+ dorsals, fragments of sacrum, 13+ caudals,T left and 2 right ribs,3 chevrons, sternal plate, right pubis. Referred specimens. AMNH 6341: cervicals 10-16 (?), dorsals 1-9, sacrals 1-5, caudals 1-29, six ribs and fragments, 1 chevron, complete pelvis, left scapula-coracoid and part of right scapula, Ieft humerus, right hindlimb and part of pes. CM 77984: cervicals The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
. {3
7-16 (?) (cervicals 4-6 have apparently been destroyed), dorsals 1-7, several ribs, left pes questionably associated. CM 1198:4 cervical vertebrae (others destroyed), likely associated with partial skeleton ROM 3670. YPM 419: left metatarsal I and a fragment of II (type specimen of so-called Barasaurus "affinis"). SDSM 25210: 2 dorsals, 15 caudals, vertebral fragments, 4 chevrons, right scapula-coracoid (incomplete), pelvis. SDSM 25331: 5 caudals. Age. Upper Jurassic, Morrison Formation. Locale. North America.
Diagnosis. Skull unknown. The vertebrae ciosely resemble those of Diplodocus but differ in (1) enormously elongated, very delicate cervicals up to 50% longer in the postmedian part of the neck; (2) the development of V-shaped, divided neural spines that commence in the middle, rather than in the anterior part of the neck, and do not continue as far back in the dorsal column; (3)the cervicalization of vertebrae in the shoulder region, reducing dorsals
to nine (or possibly eight); (4) the summits of the caudal
spines
lower in anterior part of tail and flat across top (first eight or nine are notched in Diplodoczs); (5) a proportionally shorter tail; (6) winglike transverse processes and pleurocoels that do not persist as far back in the tail; and (7) a ventral excavation of the caudal centra less pronounced than in Diplodocus. Chevrons are not well known, but the anterior process of the midcaudal chevrons appear to be less developed. The slender limb bones are virtually indistinguishable ftom Diplodocus, but the humero-femoral ratio is greater. The upper end of the scapula is very little expanded; the distal end of the ischium is exoanded.
Description Skull and Mandible
The skull and mandible have not been recovered with any Barosdurus specimens in North America. It is possible that some of the skuli materials referred to Diplodoczs actually belong to this taxon, but this possibility will be explored elsewhere. Vertebral Colttmn
The presacral vertebral formula is not yet known in Barosaurus. Because the other North American diplodocids, Drplodocus and Apatosaurus, are each known with 95% certainty to have 15 cervicals, 10 dorsals, and 1 dorso-sacral, as well as 3 primary sacrals, a caudo-sacral, and 80+ caudals, it is reasonable to assume that Barosaurzs, which is very closely allied to Diplodocus, probably had the same number of presacrals. I should point out, however, that the number of cervicals is based on one individual,
CM 84 for Diplodocus and CM 3018 for Apatosaurus.ln both trunk sections when they were found, relatively small in CM 84 but large in CM 3018. It is conceivable that a vertebra could be missing in either, although cases there was a break between the neck and
44 .
John S. Mclntosh
this appears unlikely because the vertebrae fit together so r,vell. Furthermore, in the more distantly related genus Mamenchisaurus, there are 19 cervicals and 12 dorsals and dorso-sacrals. The evidence for the vertebral count in Barosaurus is from two specimens, AMNH 6347 and CM 11984. Excluding the dorso-sacral, there are 18 presacrals preserved in the former and 19Vz in the latter, of which 17 remain. The quarry diagram for CM 11984 shows that all the vertebrae were articulated, a fact borne out by the blocks that fit together. The diagram for AMNH 6341 indicates that nine presacrais were preserved in articulation from the sacrum forward. At that point, the cervicals are separated and directed upward and
somewhat backward. The possibility that the multi-institutional collecting of this specimen might have resulted in the loss of a vertebra is dispelled b,v a letter written by Gilmore to Barnum Brorvn In this letter, Gilmore states that the Smithsonian party had disarticulated the third of the three anterior dorsals, which they collected, from the fourth and that the only break came between the
last cervical and the first dorsal. Regrettabll', the ninth presacral forward fron-r the sacrum is the one in the whole series that has suffered the most from distortion-the whole vertebra has been compressed downward and the arch rotated to the right. The eighth presacral is unquestionably a dorsal and the tenth a cervical, but lvhat is the ninth? At first glance it certainly appears to be a cervical-the parapophysis projects from the very bottom of the centrum well below the pleurocoel. However, in sauropods the cervical-to-dorsal transition is gradual, u,ith the parapophysis ascending frorn its position low on the centrum to high on the neural arch over a span of three or four vertebrae. The most abrupt change occurs in the ribs, and if these are present and articulated to their respective vertebrae it is not difficult to assign each vertebra to its place in the column. In the case of the ninth presacral, neither
rib is co-ossified to the parapophyses and diapophyses as in the cervical vertebrae anterior to it. Largely for this reason, I have concluded that it is the first dorsal. It is possible that future finds will indicate that the ninth presacral was attended by cervicai ribs and should be moved to that part of the column. \X/ith its assignment as a dorsal and the assumption of 25 presacrals (not including the dorso-sacral). there are 16 cervicals in Bdrosaurus. Ceruical uertebrae. Measurements are given in Tables 2.1 and 2.2. The two cervical series cover almost the same range. In AMNH 6341 there are cervicals 8-16 (Fig. 2.1), whereas CM 71984 has cervicals 7-16,bt the first is so poorly preserved that it has little value. CM 11984 is about 3VzTo larger than AMNH 6341. The massive distortion and/or incompleteness of the 3r/z cervicals belonging to the t.vpe YPM 429 makes their positioning difficult. The centra of Bdrosauras gradually increase in length, reaching a maximum at cervicals 13 and 14 (fourth and third predorsals). Cervicals 13 and L4 arc also the longest inDiplodocus carnegii (CM 84), but these represent the third and second predorsals in that species. In AMNH 6341, these cervicals are 3 5o/o longer The Genus Barosaurus N{arsh (Sauropoda, Diplodocidae)
.
{5
TABLE 2.1. Measurements (mm) of Barosaurus Cervicals (*' Length Cervical F
Length without
(max)
ball
21.0"
930
220
216
890
300
618
590
685
630
10
737
660
I1
775
7r5
T2
813
715
13
8s0
760
I4
865
745
15
840
731
I6
750
620
l-)
14
slightly distorted; e
:
estimated)
\7idth across Height prezyga- postzyga- diapobreadth height breadth height overall pophysis pophy'sis physis AMNH 6341 Centrum
anterior end
72 157 118 145 e 138 133 135 130" 143"
8
9
:
58
65 80 98 1
18
725 165
165*
Centrum posterror eno
130 I23 168 145 155 180 155', 160* 250
115
300
173
218
24s
135
375
205
215
305
147
390
220
245
330
165
413
230
275
330
190
450
265
283
363
230
,10(]
300
302
415
225*
s82
328
/-v 5
470
260"
61.5
303
280
500
240
657
297
300
540
273
560
YPl'4 429"
15 16
720
220 345
570
300 365 AMNH
220 200
760
6341
" Measurements from Lull 1919. These vertebrae have all suffered from crushing, often severe. Their assigned positions are uncertain. and the measurements themselves should be treated rvith extrene cauuon.
than in CM 84. On the other hand, the pelvis of AMNH 6341 rs 11% smaller than that of CM 84. Thus, based on equally sized pelves, the posterior cervicals of Bdrosdurus are nearly 50% longer than those of Diplodocus. The cervical centra in Barosaurus are all strongly opisthocoelous and all possess complicated systems of pleurocoels that dif, fer noticeably from those of Diplodocus. The general pattern is a
three-part division. There is the sharply margined pleurocoel proper, which is a deep, elongated depression sharply pointed at its anterior and posterior ends, situated just behind the overhanging diapophyses. It is subdivided in two by a vertical ridge in cervical 11 and perhaps in ali the cervicals, but the pleurocoels in these have not been prepared in sufficient detail to be certain. A somewhat similar, but even more complicated arrangement is evident in the posterior cervicals of Diplodoczs (CM 84). In Barosaurus, the lower margin of the pleurocoel proper is equaily divided by two sharp ridges of bone. Beneath the posterior ridge there is a broad depression covering much of the lower part of the posterior half of the centrum. A less well-defined deoression lies under the front
46 .
John S. Mclntosh
TABLE 2.2. Length without Anterior Ball of Barosautus Presacral Centra, CM 11984 (Figure 10.1)
cervical 7
585
cervical 16
654"
cervical
6200
dorsal
1
500 "
cervical 9
618
dorsal 2
401 *
cervical 10
dorsal
261
cervical 12
659" 689" 760"
cervical 13
857*
cervicai 14
800*
cervical 15
720
cervical
8
11
3
dorsal 4
228
dorsal 5
225
dorsal dorsal
240
6 ./
" These vertebrae have been partially rvorked out in relief in their blocks, and the blocks have not been put together, so accurate measufements are not possible. " - sum of measurements for vertebrae in separate blocks; should be rierved uirh oarrieuhr c.rution.
---'i'
-
,l'
*---'-.:,
-'': l\
{
w t B
Fig. 2.1. Barosaurus lentus,
AMNH 6311. (A-C) Ceruical t crtebra,'8 to l o. left sidc uieu s tiiilr,:
(or right side reuersed). Scale bar: 70 ctn.
ridge, and
it
extends beneath the cervical rib. The laminae extend-
ing to the zygapophyses and diapophyses are generally similar to those of Diplodocus. The neural spine of cervical 8 is flat across the top, and that of cervical 9 shows the first trace of a divided spine (FiS. 2.2A. This division increases gradually in sequential vertebrae, being moderately developed in cervicals 12 and 13, and as a deep V-shape in cervicals 15 and 16. This development is in sharp contrast to Diplodoclls, where cervical 3 already shows the first The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
' {7
'?'
ry?
A &.,. Fig. 2.2. (AJ Barosaurus lentus AMNH 5311 ceruical uertebra 8 in antcrior. le[t side. and pos!erior t iews. rB) Dipludur u' cerrregii CM 81 ceruical 8 in anterior, Ieft sitle, and posterior uieu,s (front
Httcher
1c)01).
t-
't
B trace of division, and where the division is already quite deep in cervical T (Fig. 2.28).By cervical 11 it is as well developed as cervical 16 of Barosaurus (AMNH 6341; Fig. 2.3A). In the spines, a further difference is that those of the last two cervicals (14 and 15) of Diplodocus project anterodorsally, whereas those of Barosaurus are ail directed dorsally (Fig. 2.3B). The cervical ribs are firmly coalesced to all the cervicals, and as
far as can be determined are indistinguishable from those of Diplodocus (the shafts have been severely damaged in AMNH 6347). An anterior extension of the rib can be seen in cervical 15 (AMNH 6341) and also in CM11984 (Fig. 2.4A), where some of the ribs of the more anterior cervicais are well preserved. The straight, slender rib does not extend beyond the posterior margin of the centrum as in Diplodocus, Apatosaurus, Dicraeosaurus, and Haplocanthosaurus, which is in sharp contrast to Bracbiosaurus, Eub elop us, and Cam ar as Aurus.
Dorsdl uertebrae. Measurements are given in Table 2.3 All the dorsals of AMNH 634L were articulated to one another and to the sacrum. In CM 11984 dorsals 1-7 were found articulated with one another and with the iast cervical. Assuming ten dorsals as in Diplodocus, Lull (1919) determined that those preserved in YPM 429 were dorsals 1, 4, 5; spine of 6,7, 9; and 10. Accepting nine as the correct number of dorsals, I would now identify these as dor-
2,4,5; spine of 7,8,9; and the dorsosacral. All of these have suffered from various distortions and mutilations (Fig. 2.5). The dorsals are very lighdy constructed and bear a strong resemblance to those of Diplodoczs. Dorsal 1 (presacral 9) is by far the longest. As stated above, it conforms in every way to a cervical, except that the ribs are not coalesced to it; they were probably thoracic. In AMNH 634I the vertebra is comolete but crushed downward, the arch having undergone torsion. Taken together with the sals
43 .
John S. Mclntosh
:f
t
L\ \
&
i
,,,.
,8s'
lxS & lJt
!E
Lig. 2.3. iA) Barosaurus lentus
AMNH 6317 ceruical uertebra
13
in rigbt side (reuersed) and dnterior uieu's. (B) CM 84 Diplodocus carnegii ceruical 13 in leit side dnd anterior uietL,s. (Some data from Hatcher 1901 .)
Iig. 2.4, Barosaurus lentus CM 11981. (A) Ceruical uertebra number 9 with complete rib, and (E;t dorsal tn rtSnl sldc dila pa)stertor uteL's.
The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
' {9
TABLE 2.3. Measurements (mm) of Barosauru.s Dorsals
Length
Cervical Length witliout
(max) ball
#
s65 422 332 265 280
1
2 3
4 5
)49, 265 z/) 270
6
7 8
9
5
470 260 310
d
270"
9
212
2
4
Dorso-
Centrum end
rWidth across Centrum end Height pr.r@ breadth height breadth height overall pophysis pophyiis
anterior
posterior
AMNH 500
290
310
278
250
2s5
zrs
LJ \)
240
235
))
s
248
243
220
/-.t)
220
215
2r6
328
165
290
220
320
200
240+
260
260
265
123 r82 160+ 215 220 209 215 212 248
physis
6341
34s 322 307 270 285 264 254 249 240
235 223
245
230 235 240 255 255 272
480* 640 723 674+ 778 828 865 906 901
377 413
378 386 300
438
285
485
200
467
169
290
465
720 720 730
177
464
150
472
147
370
YPM 429"
245
350 330 320 240" 30s 290
250 23s 2ss 280 280 280
590* 760
530 26s
460
*t
2;
300
840 800 850
240
sacral
" Measuremenrs from Lull 1919
moderate latero-medial crushing of cervical 16, this produces marked changes in the measurements from one vertebra to the next. Most striking is the total height, which is enhanced in cervical 16 and greatly reduced in dorsal 1. The dorsal centra, all of which bear prominent pleurocoels, decrease in length rapidly from cervical 15 to dorsal 4, at which point the length remains continuous. The ratio of the centrum length of presacral 10 to presac ral 6 is 2.8 in AMNH 6341, but only 2.0 in Diplodocrzs CM 84. The parapophysis is at the very bottom of the centrum on dorsal 1. It is slightly higher on dorsal 2, but it is still below the pleurocoel. On dorsal 3 it is directly in front of the pleurocoel, and on dorsal 4 it is just above the border of the centrum and arch. On dorsal 5 it is well up on the arch, where it is on dorsals 6-9. The first three dorsals are strongly opisthocoelous. The anterior ball becomes progressively less prominent on 4 and 5, and the last four dorsal centra are virtually plano-concave. As with the cervicals, the complicated laminae on the arch extending to the zygapophyses and diapophyses do not differ from those of Diplodocus (Hatcher 1901). A
59
.
John S. Mclntosh
TABLE 2.4. Measurements of the Barasaurtts Sacrum. AMNH 6341
Number
1
I 3 4 5
Heieht of Centrum Proximal Proximal Distal breadth height breadth prezygapoph,vses length 185
23-
455
229
'!flidth
across
diapophyses I q)
r80 t35 r80
205
lez
hyposphene-hypantrum articulation is present between dorsals 4 and 5, as well as the remaining dorsals. The V-shaped cleavage of the neural spine is quite deep in dorsal 1, gradually decreasingin2 and 3 and then rapidly in 4 and 5 (presacrals 6 and 5). A trace remains in dorsals 6 and7, but the tops of the spines of 8 and 9 are virtually flat. In CM 11984, the notch is still evident on dorsal 6 but has disappeared on 7 and also on the detached spine tentatively identified as that of 7 in YPM 429. A small, secondary median spine at the base of the cleft, shown by Hatcher (1901) to be present in the first three dorsals of Diplodocus carnegii CM 84, is also present in the first three dorsals of AMNH 6341 and can be traced forward in this specimen to the last two cervicals as well. These spines may serve as a rear anchor for the attachment of the long ligament that extends forward to the
skull (Colbert 1.961). From dorsal 5 posteriorly, the spines increase in length, with those of the last two dorsals being about the same height. The spine of the last dorsal is inclined forward as in Diplodocas (Gilmore 7932), but not to the same degree. Sacrwm. Measurements are given in Table 2.4. As in the other Morrison sauropods, Barosaurus possessed five functioning sacrals: a dorso-sacral; three primary sacrals and a caudo-sacral, or probably more correctln as Hatcher (1901) noted, a dorso-sacral; two primary sacrals; and two caudo-sacrals. However in all adult sauropods, the anterior most of these caudo-sacrals has become so modified as to appear more like a true sacral. In AMNH 6341,,the five centra and the heavy costal yoke on both sides are preserved, but the arches and diapophyses are largely restored and parts of the spines are missing. Lull (1919) noted that in the type specimen YP,l4 429 all that remained of the sacrum was part of one centrum and the co-ossified summits of the spines of the three primary sacrals. To this may be added the vertebra, which he described as dorsal 10, but which is most likely the dorsosacral. As far as can be seen from its state of preservation and preparation, the sacrum of AMNH 6341, drffers from that of Diplodocus The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
.
J1
,.{ I
ttlt,
":,
\
'.rT*
\.T "-
v
w
t,9.,.,,
% fu"-
"\,,,. :"jl,i
ii,-l
"f' ,r;"1,,i;
D
C!,,
* -#tr{'
E
Fig.2.5. Barosaurus lentus AMNH 6341 dorsdl uertebrae 1 to 9 (A-l) in anterior, lc[t sid,', aud p, 'sterior uiews.
52 .
John S. Mclntosh
'3
,$,
1
:t!
'w. ,.b
etr
,q\
I lrii, lil 1. :
,.]
The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
.
J3
only in minor respects. The anterior centrum face of sacral 1 is flat. The parapophysis or capitular facet for the modified thoracic rib is high on the anterior part of the lateral face of the centrum, in front of the large pleurocoel. The cenrra of sacrals 2-5 are firmly coossified, but the dorso-sacral is not in AMNH 6347: rt also is not in YPM 429 if the identification of that element is correct. The rib of sacral 1 is restored on the left side, as is the middle part of the right rib. It does not appear to send a lower spur to the pubic peduncle of the ilium as in Diplodocus (CM 94), but this may be due to incompleteness. The sacral spines of AMNH 6341 are damaged and have been restored. The overall heights of the dorso-sacral and first primary sacral (sacral 2) are about the same height as that of the last dorsal. Cdudal uertebrae. Measurements are given in Table 2.5. The caudals of AMNH 6341 were almost completely articulated. By comparison with the tail of Diplodocus, Lull (1979) determinec that the caudals of YPM 429 represented caudals 2-6, 1.3,15-1.7, 19-20; fragments of 23, 25 , 28, 32 and distal caudals 42 and 70 . \X/ith the articulated caudals of Barosaurzs available for AMNH 6341,I now believe that the five anterior caudals of YPM 429 are more likely caudals 1-5, 10, 1,2, 14,15,17,18; I shall not attempt to position the incomplete and the posterior ones. LuJl (1919) has described the anterior caudals in great detail. The anterior caudals resemble those of Diplodocws in that the centra have deep pleurocoels and are excavared ventrally. They are very slightly procoelous, less so than in Diplodocus. The anterior surfaces are mildly concave, the rear ones nearly flat or slightl,v convex. The transverse processes (more correctly caudal ribs) are of the winglike type, and are very similar ro the sacrals ribs characteristic of Diplodocus and Dicraeosaursus. These winglike ribs are only present in the first three or four caudals of Apatctsaurws (Ftg. 2.6A). The transition to the more normal type of transverse process occurs more rapidly in Barosaurus than rn Diplodoczs. By caudal 5, they have proceeded down onto rhe centrum and by caudal 7 have assumed almost the normal sauropod form, projecting from just anterior of the pleurocoel (Fig. 2.68). In contrasr, the winglike development is still evident on caudal 12 in Diplodoczzs, where the transverse process arises on the arch and extends down only as far as the border of the arch and centrum. The transverse process disappears on caudal 18 (AMNH 223) or 19 (USNM 10865), whereas it disappears by caudal 15 of Barosaurus AMNIH 6341. The pleurocoel also persists further back in Diplodocus, to caudal
18 (AMNH 223), caudal 19 (USNM 10865), or caudal 16 (DMNH 1.494); the last trace of a rrue pleurocoel in Barosaurus (AMNH 6341) is caudai 14 (Fig. 2.6C). A striking difference between the caudal vertebrae of Barosaurus and Diplodocus is evident in the degree of ventral sculpturing. In Barosaurus, this begins as a prominent, squarish pit in the anterior caudals (Fig. 2.6G) but soon becomes a broad,
rounded concavity covering the entire ventral surface of the cen-
54
.
John S. Mclntosh
TABLE 2.5. Measurements (mm) of Barosaurus Caudals
AMNH
6341
Centrum
Number length
Centrum
anterior face
breadth height
1
153
300
2
175
280
3
160
320
4
195
295
5
183
290
6
190
275
7
190
288
8
200
283
9
206
270
10
227
279
11
227
283
12
250
265
13
266
245
I4
263
235 +
15
263
230
t6
276
228
1a
278
209
18
195
I9
283 279
20
268
170
21
268
163
22
260
149
L.)
248 240
r13
24 25
220
125
LO
21.3
120
27
198
110
28
182
94
29
17l
9I
186
139
283 27s 270 252 247 256 236 223 22r 214 212 215 205 274 202 180 165 1.64 152 133 130 1.27 123 122 93 98 82 80 70
I
185
345
265
2
220
340*
230
3
210
370
345
.+
210
355
235
5
205
325
200
10
245
250
208
12
245
240
215
1.4
270 270
2t5
203
220
180
15
(" -
slightly distorted)
Centrum
face Overall Postzygapophysis '!ilidth across breadth height height to top of spine postzygapophyses AMNH 6341 posterior
26s 290 278 275 259 268 273 253 278 280 263 253 250 238 224 228 195 188 179 775 748 151 140 127 109+ 118 110 98 85
320 340 330 315 230 23s 230 270
29s 235
126
2s2
133
230
660
490
180
240
463
21.5
228
590 498
41s
178
225
520
446
t65
21.9
505
452
143
21.9
439
458
t)A
21s
433
390
135
189+
396
240
415 +
209
448
11)
113
r95
408
390
98
189
375
393
115
172
185 169
298
381
75
268
380
71
153 149
87 78
-/ /1
70
743 113
233
108
210
322
197
258+
76
132
185
48
57
113
186
42
195
670
180
185
200
640
220
215
585
245
155
109 109
65 63
60
99 85
49
71.+
YPM429230
185
200
21s
443
205
422
200 180
360
The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
.
JJ
Centrum
Number t7
Centrum length
285
anterior
200
a
b o'7
d
Centrum
face overall
posterior
breadth height breadth height
18
c
face
il3 77 47
e
6+
f
hejght
155 210 170 183 142 135 |]3 e- il92 70 90 70 38 38 43 21 12
Postzygapophysis \(idth across to top of spine postzygapophyses
310*
53
20 17
" These vertebrae are not available for re-measuring at this time. I have therefore used those made by C. C. I{ook in 191.7 for caudals 1 through 17. These differ slightlv from those published bv Lull in 1919. Lull's measurements were used for 18, d, and f, and all others were made by me. The anterior and posterior portions of caudals "b" and "c" do not connect and may belong to seDarate vertebrae.
g
ff* n';:' &"'
r'
.!
iri'rr':f
i
.v{,,,',.
4&,,,,'
\k's
f-
e;"-
Afli-i t
B
,.
* ""
-rc#t*q--
{9
.;
,;tot
i
''"
J,'"*"".S",,
J F
F ,rr,.;
"
t1;;.4. ril
Fig. 2.6. Barosaurus lentus uertebrae itt Ieft side uieus (A-F), dnd caudal
AMNH 5311 cattdal 5, uentral uiew (G).
56
.
John S. Mclntosh
tl
",|
H. .
trum. It persists throughout the entire series of 29 vertebrae in AMNH 6341, becoming gradually shallower until, on number 29,the ventrai surface has become almost flat. In Diplodocus, the ventral sculpturing is much deepeq particularly in caudals 1-20 (AMNH 223).In addition, Diplodocus caudals are greatly elongated, whereas those of Barosaurus are somewhat less so (Fig. 2.6D-F). Those of Apatosaurus are elongated still less so but are considerably longer than those in most sauropods, for example, Camarasaurus, and to an even greater degree in Haplocanthosaurus and Brachiosaurus. Another noticeable difference between Barosaurus caudals and those of Diplodoczs involves the height of the spines in the anterior part of the tail. In BarosAurus, the overall height of the spine in the few anterior caudals is almost twice the diameter of the centrum, whereas in Diplodocus it is almost three times as great. A less striking difference is seen in the broader transverse diameter of the spine in the most anterior caudals of Barosauras. Also, the caudal spines in Barosaurus show no trace of a cleft, whereas rn Diplodoczs a small, but definite cleavage is evident as far back as caudal 8 (CM 84) or caudal 7 (AMNH 223). A final difference is in the greater anteroposterior breadth of the spine in Barosaurzs beginning at caudal 16 or caudal 17 posteriorly. No caudals were found with AMNH 6341 posterior to caudal 29. but Lull (1.9L9) believed he found one, which he identified as caudai 32. If Holland's (1906) estimate of the positions of the caudals in Diplodocus (CM 307) is correct, the position of the YPM caudal is probably in the 40s. Nothing need be added to Lull's (1919) description of it except to state that it is relatively shorter than its counterpart rn Diplodours. Another fragment found with YPM 429 suggested the presence of a distal whiplash as in Diplodocus and Apatosaurus. To summarize, there are more similarities between the caudais of Barosaurus and Diplodocus than there are between those of any other sauropod genera. However, the specialization is more advanced in Diplodoozs in that it had a longer tail; higher neura spines in the sacral region; greater development of the anterior, winglike transverse processes; longer persistence of the pleurocoels and transverse processes; and more pronounced procoelous ante-
rior centra. Thoracic Ribs
A number of ribs, none complete, were found with both YPM 429 (Fig.2.7A) and AMNH 6341. These ribs resemble those figured by Gilmore (1936) for Apatosaurus ICM 3018). The proximal end likely belonging to rib 1 (?) shows the wide separation of the head and tuberculum. If it is truly rib 1 and not rib 2, there is a difference from that of Apatosaurus in that the head continues in a direct line from the shaft and is not directed outward. A similar fearure is noted in what is probably the same rib from the right side of
The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
.
57
AMNH 6341. Further description of the ribs in their
present frag-
mentary state would not be useful. Cheurons The two most anterior chevrons of the type determined by Luli (1919) to be chevron 5 and chevron 9 are typical anterior sauropod chevrons (Fig.2.78, C). They have been described by Lull (1919), and no further comment need be made except to note that the
hemal canal is strongly bridged over as is usual in the diplodocids, and in contrast with, for example, Camarasaurzs. The third chevron is from the transition region in which the anterior projection typical of Diplodocrzs has begun to form (Fig. 2.7D). Lull
it as about chevron 16, but rf Diplodocus (AMNH 223\ is taken as the guide, it is more probably chevron 13. However, it is unclear tf Diplodoclzs should be used as a guide based on one side of a more posterior chevron preserved with AMNH 6347 (FiS. 2.7E).Its position is not known, but it was collected from near caudals 22-28.It resembles most closely chevron 18 of Diplodoczs (AMNH 223) and has a fully developed anterior process. However, it is only about2/z as long (about 200 mm long when complete). This shortening is in keeping with the general trend noted in the caudals of the two genera. This chevron is important because it clearly demonstrates the chevrons in the mid-tail region of Barosaurlrs were of the typical Diplodocus-type, al(1.919) identified
though shorter, and that they were much more advanced than those
.\ril,i
ffia
W%
*.,w \
,,'1
'\
'.,
\ ,,'t
r$\ ,w , l'!i.
e$j ts'
p
Fig. 2.7. Barosaurus lentts (A) left ribs of YPM 129; (B-D) cheurons
of YPM; (E) cheuron of AMNH 6311.
53 .
John S. Mclnrosh
,ff f
.t
ffi, D
E
':,
"-4t
*'.."-*tt '*-:":
TABLE 2.6. Measurements (mm) of Barosaurus Pectoral Arch,
AMNH
63,11
Length of scapula, on the curve Length of scapula, in a straight line
1300
1240
Breadth of distal end Least breadth of shaft
375
Length of coracoid
297
\(/idth of
420
same
195
of Apatosaurzs (AMNH 339), where Diplodocus-like chevrons are present but smaller.
Pectoral Girdle
Scapula and cordcoid. The right scapula and coracoid of AMNH 634L are complete except for a portion of the anterior edge of the broad plate that forms the proximal end of the scapula. They are firmly co-ossified and resemble those of Diplodocus (Fig. 2.8A, B). The scapular blade, directed upward and backward, expands gently and continuousl,v toward the distal end, the rear border flaring slightly just below the end, but the erpansion is less than in Diltlodoozs (CM 94, AMNH 223). Except for the upper expansion and a small bulge at midlength, the posterior border is straight until it flares out ventrall,v. As in Diplodocus, the ridge on the lateral surface of the proximal plate between the great muscle fossa and the superior fossa makes an acute angle -40', contrasted with -60" in Cdmarasaurus and Apdtosaurws (measurements in this secrion refer to figures in Table 2.6). Otherwise, the scapula resembles that of the latter quite closely. The coracoid is not distinctive. It is a squarish bone, rounded at the corners) thickest at the posterior border where it forms part of the glenoid fossa for the humerus. The fully enclosed circular foramen is located below the scapular
articulation. Sterndl Plates
Lull's (1919) thorough description of the sternal plate need not be repeated, except to note that the anterior and posterior ends \\.ere reversed by Lull (19L9). Forelimb. Measurements are given in Tables 2.7-2.9. A right manus, field #310/L, was found near the junction of the cervicals and dorsals of CM 11984 and was given the same field number by Douglass. It is possible that it does belong to Bdrosaurezs, but I believe that unlikely. The manus is indistinguishable from that of ApJtosaurus and is the exact size of the left manus of Apatosaurus Iouisae (CM 3018) found about 21 m west of CM 11984. CM The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
.
59
'qr\.
,\
t\
s,* 'p ,,
'e
,,
".{tr :l{
c
A
ffi,'"
D ir..-
B
q
'",
\{ i'$
t$ .i,.y
E
frg. 1.8. Barosaurus lentus: /A-B)
t
sc.rPttla/corcoid in posterior L1l1Ll side uietus AMNH 5311; r tel:
tC-Dl right humerus in antertor and obliqtte uiews AMNH 5311; (E) carpal, top uiew CM 21711; (F) right ulna, radius, and iltet)(arpols I !o lV in anlerior uieu'.
69 .
John S. Mclntosh
TABLE 2.7. Ratio of Humerus: Femur Length in Diplodocids
Barosaurus lentus AMNH 6341,
.72
Diplodocus sp. AMNH 5855 Diplodocus "longus" USNM 10865 Diplodocus hayiHMS 175 (formerly CM 662) Gigantosaurus africanus HMB, quarry A Gigantosaurus africanus HMB, quarry k
.67 .67 .64 .72 .72
TABLE 2.8. Comparative Measurements (mm) of Diplodocid Forelimbs. Ratios given in ( ) are relative to bone length (100). Circumference is minimal shaft. Barosaurus
lentus
AMNH
CM
Diplodocus
"longus"
USNM 10865
Diplodocus hayi
HMNS 175
Gigantosaurus robustus
HMB A HMB K right left left right Lt / /a (100) 970 (100) (100) (100) 990 (100) 936 (100) 910 (-) 965" 1032 (100) Humerus, 1034 Iength (-) 429 147) 400 (43) 440 i44) 445 147) (-) 382 (37) 340 (33) Breadth, proximal (-) 162 1161 150 (16) 173 (19) 188 (20) r70 (17) 1s0 (1-s) 151 (15) Breadth, shaft - (-) (32) 328 (34) 265 (,29) 317 B4) 330 (33) 320 (33) 333 278 250 Breadth, distal 124) (45) 438 (,+5) 449 119) 470 (50) 502 (51) 430 144]) (-) 460 440 circumference 143) (-) 740 (100) (100) 720 (100) 728 (100) (100) (-) 735 940 ulna, length - (-) - (-) 210 Q6) 240 (33) 22S (33) 797 \27J - (-) (-) 255 (34) Breadth, 6341
proximal
shaft Breadth distal Breadth,
Circunrference Radius, length Breadth, prorimal Breadth, shaft Breadth, distal Circumference -
(-) (-) (-) (-) (-) (-) (-) (-)
(-) - (14) 302 (32) 930 (100) 117 (13)
\14) (18) 29-5 (40) (-) - (-) (-) 77 \8) - (-) 147 \16) - (-) 219 (27) -
139
102
129
(16) 83 (11) - (-) (22) 130 (18) - (-) (38) - (-) - (-) 275 632 (100) 686 (100) 660 (100) 148 (22J 151' 122) 7s7 124) 113
159
(13) 1,48 (22) 254 137) 88
83 (12) 106 157 123) 160 233 (34) 265
-
(-) (-) (-) (-) (-)
116) - (-) 124) - (-) \10) - (-)
1s5 (21)
21s
129)
249 (34)
(-) - (-) (-) - (-) - (-) -
" Extreme proximal end restored, measurement, probably too [ow.
3018 is the largest Apatosaurus, indeed the largest sauropod in the entire quarry at Dinosaur National Monument. I think that this specimen is the missing right manus of that otherwise almost complete skeleton, which was washed downstream from the Apatosaurus. Another specimen, CM 27744 (field #312)' comprising
part of the right forelirnb and foot, found 4 m west of the Barosaurus skeleton (CM 11984), may belong to that specimen (Mclntosh 1981). The iimb bones are very long and slender but cannot belong to Brachiosaurus or Camarasaurus because the ratio of the length of metacarpal II to that of rhe ulna is only 0.31 compared to 0.49 in Brachiosaurus and 0.44 in Camarasaurzs,' 0.31 is a reasonable ratio for a diplodocid, but the limb is immediately excluded from Apatosaurus whose forelimb is much more robust. The metacarpals are also much more slender than those of the rela-
tively stout-limbed Diplodocus Daf i (HMNS 175' formerly cM 662: see also Bedell and Trexler, this volume). The metacarpals are also more slender than those of AMNH 380, which are referred by Osborn and Granger (1901) to Diplodocus? and probably belong The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
'
(1
TABLE 2.9. Comparative Measurements (mm) of the Sauropod Manus (e
Element
Barosaurus lentus
hayi
cM
HMNS 175
Ulna Radius
Metacarpal I Metacarpal II Metacarpal III Metacarpal IV Metacarpal V Metacarpal II: ulna ratio Phalanr I-1
21774
:
estimate)
Diplodocus
940
728
sp. AN,INH 707
380
Camarasaurus grandis
sp.
AMC
695
840
AMNH
823
AMNH
573
716
930
686
645
810
549
672
230 distal
170
187
/_+ 5
213
288
293
212
226
260
247
322
225
./-l1')
242
-)
215
/-+
\
))4
300
965
L-)
257
191 182
188
220
202
)1n
0.31
0.29
0.32
0.31
0.42
0.45
54
Phalanx I-2 Phalanx III-1
58
Phaianx IV-1
48
Phalanx V-1 Phalanx V-2
aa .)L
78
to that animal. Interestingly, the limb of CM 21774 ls 28% longer than that of a large Diplodocws (USNM 10865) from the Carnegie Quarry. Since I think it plausible that CM 21774 does belong to Barosaurus, if not to CM 11984 itself, I shall describe it as such be1ow.
Humerus. The humerus of AMNH 6341 is a long, straight, slender bone whose shaft is not twisted (Fig. 2.8C, D). It is expanded at both ends, more so at the upper end, but nor ro the degree seen rn Camarasaurus er, particularly, rn Apdtosaurzs. As in most sauropod humeri, the radial and ulnar condyles are weakly developed. A prominent deltoid crest extends down the lateral margin of the bone from near the proximal end to just above half the length, where it ends abruptly. The bone overall is virtually indistinguishable from that of Diplodocus, and there can be little doubt that isolated humeri belonging to Barosaurushave been attributed to Diplodoczs. The ratio of its length to rhar of the femur is greater than in Diplodocws (see Table 2.7). The presence of a relatively longer forelimb than in Diplodocus is not unexpected in light of the longer neck and shorter tail of Barosaurus. ulna. The ulna of CM 21774 is very long and slender (Fig. 2.8F). The lower third is gently bent backward. The rwo processes on the proximal end, which cradle the proximal end of the radius, are, like Diplodocus,less prominenr than in most other sauropods.
62
.
John S. Mclntosh
Radius. The radius is very long and slender (Fig. 2'8F). Its proximal end is squarish with blunted corners. The lower half of the bone is slightly flattened latero-medially and expanded in this direction. It gently bends toward the ulna. Manus. The preserved parts of the right manus of CN{ 2I744 (Fig. 2.8F) include one large carpal; metacarpals I, II, and IV and the upper half of III; phaianges I-1 and parts of I-2,1V-1', V-1, and V-2. The carpal, which is often called the radiale in sauropods but is more likelv the first carpal of the second row, is crushed against the upper end of metacarpal I (Fig, 2.8F). It is massive and generally circular, covering the proximal ends of metacarpals I and II. It measures 159 mm by 135 mm by 48 mm. The metacarpals almost approach those of Camdrasaurzzs in their slenderness, but their length ratios with the ulna and radius are typical of the Diplodocidae. They are more slender than those of Apatosaurus or Diplodocus hayi and to a lesser degree to the two mani with accompanying radius and ulna, from Bone Cabin Quarrn \fyoming, which probably belong to Diplodocrzs (AMNH 380 and 695, the latter now AMC 658). Recently, an associated forelimb and manus from the Black Hills of South Dakota, SDSM 25277, was described by Foster \1996), and referred with a query to Barosdurus or perhaps Diplodocus. The proportions of the elements of this well-preserved limb to those of CM21774 indicate a somewhat more robust limb. Peluis
In AMNH 6341', the right ilium is complete except for a small part of the upper border; of the ieft ilium, only the acetabular portion was preserved. Both pubes and ischia were complete except for portions of the proximal ends of the pubes and the right ischium' The greater portion of the right pubis of the type YPM 429 lacked the disral end and part of the head (measurements are given in Table 2.10).
Iliwm. The most notable feature of the ilium, which is virtually indistinguishable from that of Diplodocus, is its long, slender public peduncle (Fig. 2.9A-C). As in the latter genus, the outwardly directed anterior lobe is a iittle larger than that of Apatosaurus. Pubis. The pubis, with its relatively slender shaft, likewise re-
that of Diplodocus. The circular pubic foramen opens down"vard from the lateral face. It is open in both pubes of AMNH 6341 but closed in those of YPM 429, and it is probably ontogenetic. The most prominent feature of the Diplodocus pubis is the strong development of the process for the attachment of the ambiens muscle on the anterior margin of the upper end of rhe bone. A hook-shaped process develops even in juveniles, as shown by a specimen on the face at Dinosaur National Monument (DINO 3783). A similar deveiopment is seen in the African genus Dicraeosaurus and also in Gigantosaurus africanus, but not in Apatosdurus. On the right pubis of AMNH 6341 most of the ambiens process has eroded away (Fig.2.10A). The upper end of the sembles
The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
'
(3
TABLE 2.10. Measurement (mm) of the Barosaurus Pelvic Bones, AMNH 6347 G: estimate) Length of ilium Length of pubic peduncie Diameter of acetabulum
940 285 310
Breadth across anrerior tips of both ilia Length of pubis
1010e 890
Extent of ischiac articularrons
315
Least breadth of shaft Breadth of distai end
220
155
Length of ischium Least breadth of shaft Breadth of distal end
219
Thickness of distal end
80
873 707
K.'ir.:
,
r,,x
qt:
{
Fig. 2.9. Barosaurus lentus
AMNH 6311 ilia and parrial in (A) right side, (B) uentral, and (C) anterior uiews.
sacTum,
64
.
John S. Mclntosh
B
A
t
i!i:
$
,,*-'ta""r,l. Fig. 2.10. Barosaurus lentus 6341 all lateral uieus. Left (A) and right (B) Pubis; YPM
AMNH
D
429 rigbt pubis (c): AMNH 6341 left iscbium (D).
left one is also incomplete but shows the beginnings of the process (Fig. 2.10B). The type pubis YPM 429 has a prominent process) but even here it is not complete, so it is not certain that a true hook was present (Fig. 2.10C). Lull's (1'91'9) estimated length of the incomplete pubis of YPM 429 is grossly inflated because he estimated the length from Hatcher's figure of the pubis of Diplodocus (CM 94), which was drawn at the oblique angle as the bone appears in an articulated pelvis. This reduced considerablv the apparent breadth of the shaft as determined by Lull. It seems more likely that the pubes of YPM 429 were about the same as those of
AMNH 6341. Ischium. The ischia also closeiy resemble those of Diplodocus, with their expanded distal extremities, which in AMNH 634L were co-ossified, a common occurrence in adult members of the Diplodocidae (Fig. 2.10D). The distal expansion is similar to that in Diplodocrzs, but less exaggerated than that in Apatosaurus (Ftg. 2.11). The manner in which the distal ends abut one another is in sharp contrast to the edge-to-edge articulation of the unexpanded distal ends in Camarasaurus and Brdchiosaurus' The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
' (5
Fig. 2.11. Distal ends of ischid.
/A/ Barosaurus lentus AMNH 6311 ; (B ) "Gigantosaurus" africanus k 14 and 4.t; (C) BMNH
M
specimen; /D/ Camarasaurus supremus
AMNH 5761; (E)
Dipodocus cargegii CM 81 (F) CM 91; (G) CM 91; (H) D.Iongus USNM 10855; {/ Apatosaurus ajax (Atlantosaurus immanis/r YPM 1810; /// A. excelsus YPM 1980; (K) A. louisae CM 3018.
Hindlintbs The hindlimb of AMNH 6341 is beautifully preserved and uncrushed (Fi9.2.12) and is exrremely similar ro those of Diplodocus. This similarity is most evidenr with AMNH 5855. an isolated specimen comprising all rhe limb bones from both sides and several qir-
dle bones, but no verrebrae. Ir was described by Mook 11917) as Diplodocws sp. but the similarities are so striking that I would have referred it unhesitatingly to Barosaurus were there not a striking difference in the humero-femoral ratio: 0.72 tn Barosaurus and 0.66 in AMNH 5855. Associated fore-and hind limbs provide a significant difference in distinguishing the two taxa (measurements are given in Tables 2.11 and 2.12\. Femur. The femur is readily distinguished from those of other non-Diplodoczs sauropods from the Morrison Formation by its overall slenderness. The femur of Barosaurus falls inro one of two variants of the "standard" Diplodocus-type femur. The standard type has a generally straight shaft, which becomes somewhar expanded in its upper third, and it also has an oval cross-section. Examples are D. carnegii (CM 94, CM 86 now at the Field Museum
in Vernal, Utah), D. hayi (HMNH 175), and a number of
speci-
mens from Dinosaur National Monument and Bone Cabin Quarry. In the first variant, which grades into the "standard" type, the expansion of the upper third is enhanced, giving the shaft a slight sig-
66 .
John S. Mclntosh
TABLE 2.11.
Tibia: Femur Lengths in Diplodocids Barosaurus lentzs AMNH 6341
-A ./a
Diplodocus carnegii CM 94 Diplodocus DINO 378, DINO 4236 Diplodoar DNM field #601I5-16 in Durham and Toronto Diplodocus AMNH 5855 Diplodocus "longus" DMNH 1494 Diplodocus hayi HMS 175 (formerly CM 662)
.72
Diplodctcus "longus" USNM 10865 Gigantosaurus africanus HMB Quarry k
.65 (or .75")
.72 .71.
.69 .68 .65 .64
" Two articulated sets of left tibia-fibula-astragalus r.vere found rvith DNM field #355. The shorter set r'vas used by Gilmore in the mounted skeleton, br'rt there is some reason to believe that the longer ones mav have been the correct sei.
moid curve. Examples are the Barosaurus femur (AMNF{ 6347 U.T. 993.1, YPM-PU 18710 [formerly AMNH 651], AMNH 5855). The type femur of Gigantosaurus africanus from Quarry A at Tendaguru also falls into this category, whereas the type of D. carnegii (CM 84) is intermediate with the standard type. The second, more striking of the two variations is the so-called Amphicoelids or stovepipe type, where the anteroposterior diameter is increased, resulting in an almost circular cross-section of the shaft; the head of the femur is also more weakly developed. Examples include the type femur of Amphicoelias ahus AMNH 5764, a specimen in the University of Utah collection from the Cleveland-Lloyd Quarry, and two Diplodocus femora (AMNH 223, USNM 10865 on the mounted skeleton). Finally, Lull's (1919) estimate of a femur over 2.5m long in YPM 429 is incorrect. The fragment he used in making the estimate does not belong to the type skeleton. Tibia. The shaft is straight and slender. It is little expanded at the distal end, more so at the proximal end, with a prominent cnemial crest typical of the diplodocids (Fig. 2.1.28), in contrast to CamdrdsAurus, where it is smaller. There is a wide variation in the ratio of the length of the tibia to that of the femur, which is not easiiy explained and will be treated more fully in a forthcoming publication. Fibula. This long, slender, flat bone is slightly expanded at each end. The usual triangular muscle scar appears on the medial face of the proximal end (Fig. 2.1,2C). The only other feature of the bone is a muscie scar about one-third of the wav down the shaft from the The Genus Barosautus Marsh (Sauropoda, Diplodocidae)
'
(7
TABLE 2.I2. Measurements (mm) of Hindlimbs
DiPlodorus
Barosaurus sp.
Ientus
AMNH
cL1l
634I
Femur, lc. oth
ne8tc
CM
94
A.\4NH
5855
left
rieht
- (_) 3es 127) 393 (27) 313 (28) - (-) 202 (14) 183 (13) 162 (r4) 150 (-)
1440
breadth,
proximal breadth, shaft breadth, distal
(100)
385
1410
(27)
(100) 113s (100)
369
(2.6)
274
(24)
263
*t^."^..-* ru.ta45 USNM 10865
t,-)
circunrference 540 (38) 510 (36) 410 (36) 408 (-) Tibia, Iength 1064 (100) 1010 (100) 783 (100) 770 (100) breadth,
27s
\26)
274
136
(13)
130 24s
proximal breadth,
shaft
(27)
195
(25)
215
(28)
(13)
100
(13) l23J
108
(14)
"
hayi
HMNS 175
(cM
562)
393 \27)
430
(31) - (-)
208 (13)
227 (16)
195
114)
208 (16)
301 (19)
382 \26)
420
(30)
387 \29)
563 (37)
590 (41)
548
1020 (100)
93.r (100)
362 (32J
301 (32)
-
))\ t)4\
circumference 368 (35) 358 (35) 273 (35) 279 136) 419 141) Fibula, length 1120 (100) 1055 (100) 800 (100) 798 (100) 107s (100)
444 147) 983 (100)
(24) (21t
178
(18)
223
179
\9) (16)
88 (8) 63 (S) 165 11.6) 1.28 (16)
circumference 267
(24J
240
breadth,
205
185
proximal
shaft breadth, breadth,
99
distal
\23)
1,75
768
(22)
(23) - (-)
\22)
63 (8)
214 t20)
)\) t)4\
(-)
17s \76)
-(-)
107 (11) 172 lr7)
180 (23)
)q\ t)7\
279 (28)
-
Quarry k
34e (23)
174 119)
(24)
A
(100)
1448 (100)
1Sg (15)
zss
Quarrv
1s75 (100)
247 (24)
breadth, distal
Gigantosaurus" africanus
1380
-
1340 (100)
(40) ss9 (42) (-) 860 (100) i-) 325 (38) (-) 1,40 \16) (-) 2s.5 (30)
- (-) -(-)-(-) -(-)-(-) -(-l-(-)
362 t43)
- (-) -(-)-(-)
(-)
Ratios given in ( ) are relative to bone length (100). circumference is minimu.-r shafr
top on the lateral face. The distal end is expanded mediaily opposite a concavity in the astragalus. Tarsals. The astragalus of AMNH 6341 (Fig. 2.12D) is virtually a carbon copy of AMNH 5855, but it differs from that of Diplodocus (CM 94) and those of the African species in that the medially directed process, which lies beneath the tibia, is somewhat longer in Barosaurzs. It resembles that of Apatosaurzzs closely. There was no calcaneum found with AMNH 6341 or with any other diplodocid. Indeed there was no room for one beneath the Iower end of the fibula, whose distal end extends well beneath that of the tibia. Bonnan (2000) has reported the presence of a calcaneum associated rvith a Diplodocws pes CM 30767. The specimen, Field Number 1,75 from Dinosaur National Monument. was as-
63
.
John S. Mclntosh
*
I '
l,
:t. '1,'
'M :'11''
,ttli
.
'.
:r tir6
.l 1
t,,,,$ti',',
li .i Y:,'
,,,,"
& |
.i
eq'
.-,il
signed to scattered bones of a number of individuals. Having studied the records carefully, I do not believe the association of this bone with the foot can be substantiated. Pes. Metatarsal I is short and massive, with the prominent process on the lower part of the posterior margin of the lateral face (that facing metatarsal II) so characteristic of the diplodocids Diplodocus, Apatosaurus, Cetiosawriscus, and Dicraeosaunzs; it is so far not known in others (measurements are given in Table 2.13).
'a
,
Fig. 2.12. Barosaurus lentus
AMNH 5311 right hindlimb bones: (A) femur posterior and distal uiews; (Bt tibia posterior; (C) fibula in lateral and distal uieuts; and (D) astragalus in
posterior uiew,
The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
' (9
TABLE 2.13. Measurements (mm) of the Pes of Barosaurus
AMNH
6341
Height of astragalus Maximum transverse breadth Anteroposterior breadth
139 246 167
lentus 6341 IIIV
Metatarsal length Metatarsai proximal transverse breadth Meratarsal proximal anteroposrerior
B.
B. "affinis"
AMNH
YPM 419 TTT
140 181
175
704 94 136 131 134 82
138 86
97
105
98
?cM 11984 III IV
il
208 2r7 242 239 231 142 132. 101 706 199 183 192 140 137 1r2
breadth
Metatarsal distal transverse breadth Metatarsal distal anteroposterior breadth
r21
Shaft least circumference Length of first phalanx
158
86 58
Length of second phalanx Length of claw
108 92 187
93
120
58
69
167 146 113 110
t75 77
;10; 265
A 'il:i),,,'' ' '|LY'&'fit'
B
Fig. 2.13. Barosaurus lentus bones of the right
AMNH 6341
(A-C) Metdtdrsdls I,II, and V in anterior, posterior, lateral, and dorsal uiews.
Pes.
70
.
John S. Mclntosh
c
119
*$d
; 188
91
79
i+ B
,i"u.
)t
'6'n t*'"'*-e; The bone is virtually identical to that of Diplodouzs, but a bit less massive than that of Apatosaurus. Metatarsal II possesses a similar, though smaller, distal process and the comparisons are the same as for metatarsal I. Metatarsal V cannot be compared with that of CM 94 (Diplodocus) because it was broken in life and is so distorted as to make comparisons worthless. Compared to that ol Apatosaurus (CM 89), metatarsal Y in Barosaurus is surprisingly more robust, particularly at the distal end. It bears a close resemblance to that of Camarasaurus grandls (YPM 1905). The phalanges do not differ noticeably in AMNH 6347 and CM 94. They may be tentatively identified as I-1, lI-I,ll-2,II-3, III-2, and III-3 (Fig. 2.13). As expected they closely resemble those of Diplodocus
Fig. 2.11. /A) Barosaurus lentus YPM 419 E. "affinis") left metatarsal I in anlcrior, fosterior, medial, and laterdl uiews. (B) CM 11981 (?) Ieft metdtdrsdls I to V in InteTK)r utew.
carnegii (Hatcher 1901) and "Barosaurus" africanus (Janensch 1961\.
Lull (1919) identified the type of Barosaurus affinis Marsh as two metapodials that he inexplicably called metacarpals I and II. One is clearly the left metatarsal I and the other appears to be the upper end of left metatarsal II (Fie.2.1a). They do not differ from those of AMNH 6341 except that they are a little smaller. A large diplodocid left pes was found just below the junction of the cervicals and dorsals of CM 11984 and assigned the same field number #310/N. Although the first metatarsal differs from that of AMNH 6341, in minor respects, the pes has been provisionally catalogued as part of CM 719B4.
The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
.
/1
Discussion Status o/ Gigantosaurus africanus Fraas
In 1908, E. Fraas described two species of a nerv genus of sauropod dinosaurs from Tendaguru, German East Africa (now Tanzania). He named them Gigantosaurus africanus and G. robustus, aware that Seeley had used the generic name for an English sauropod in 1869. Fraas argued that Seeley had never properly characterized this genus and had never figured it, and that therefore the name was open for use. Citing nomenclatural rules then in effect, Sternfeld in 1911 argued that the name Gigantosdurus was not available and renamed the African genus Tornieria. Then in 1.922, lanensch concluded that the two species belonged to separate genera and in a brief footnote referred to G. africanus as Barosaurus africanus. Until recently, following Nopcsa (1930), most writers incorrectly referred to the other species as Tornieria robusta. This reference is incorrect because Tornierid replaced Gi-
gantosdurus africanus and thus may still be available for that species if it proves not to belong to Barosaurus. GigdntosAurus robustws is properly called ldnenschia robusta, as proposed by \X/ild in 1991. However, Janensch never really made his case for assigning G. africanws to Barosaurzzs. Fraas (1908) noted the great similarity of the the material assigned to this species wtth Diplodocus, and my observations of the large collections at the Museum fiir Naturkunde in Berlin and the Natural History Museum in London reveal that the preponderance of the specimens belong to Bra-
chiosaurus and animals closely allied to Diplodocus. Does this diplodocid material belong to a single genus, does it belong to both Diplodocus and Barosaurus as rn North America, or does some or all of it belong to a third, as yet unnamed genus? A series of anterior caudal centra exhibit ventral sculpturing quite different from that seen in either Barosaurus or Diplodocus from North America. There is a central pit divided in two by an anteroposteriorly directed midridge. Some of the caudals do closely resemble those of Barosaurus, particularly as to rheir slight ventral sculpturing, but there are others that have a greater resemblance to those of Diplodocus. The only Barosaurus-like cervical figured by Janensch (1929; dd 1,79) is not overly elongated and resembles Diplodocus more than Barosaurus. The humerus:femur ratio is 0.72 for both the skeleton from Quarry k and that from Quarry A (Table 2.7).Both agree with that of AMNH 634l implying a long forelimb. These ratios for the Tendaguru material musr be viewed with caution, because the humerus from Quarry A was collected by the German expedition at the same site from which Fraas had obtained the type femur of Gigantosaurus africanus. Fewer than a dozen scattered bones were taken up there by the two expeditions, and although there is no duplication, at least one anomalous bone, a Brachiosaurus fibula, was taken from the site. As to skeleton k, the humerus:femur ratio is suggestive of Barosawrzs, but the
72
.
John S. Mclntosh
tibia:femur ratio of 0.64 as compared to 0.74 for AMNH 6341 (Table 2.10) suggests a very different animal. The conclusion I come to is that further study must be made of Gigantosaurws africanus material, particulariy of its vertebrae, before it can be assigned with any assurance to Barosdurezs. This may require preparation of more material in Berlin if indeed this material survived \forld War IL Barosaurus Compared with Other Diplodocids Barosaurus differs from ApatosAurus (1) in having one less dorsal vertebrae; (2) in having more slender cervicals with slender,
rather than robust, ribs; (3) in having winglike,
transverse
processes on the caudals extending much further posteriorly; (4) in
having both pleurocoels and ventral excavations in the anterior caudals; (5) in having more slender limb bones; and (6) in having a humerus:femur ratio of 0 .72, instead of 0.67 . Barosaurus differs from Dicraeosaurus (1) in having many more and much longer cervicals and fewer dorsais, 9 instead of 12; (2) in having pleurocoels in its dorsals; (3) in having much less cleavage in the spines of the posterior cervicals and anterior dorsals; and (4) as cited above for Apatosaurus, in having both pleurocoels and ventral excavations in the anterior caudals. Barosaurus differs from Cetiosauriscus (1) in having more complex sculpturing laterally and ventrally in the caudals; (2) in having a larger humerus:femur ratio; and (3) in having differently developed chevrons.
Barosaurws has both similarities and differences with Superslurus. Various specimens formerly assigned to other taxa may in fact belong to Supersaurzs, including the large anterior caudal (BYU 9045, formerly BYU 5002; Curtice et aI. 1996) and the gigantic cervical (BYU 9024, formerly BYU 5003), although it is so badly crushed that many important details cannot be seen. The type specimen, the right scapula-coracoid, is of the diplodocid type as noted by Jensen (1985). Supersaurus differs (1) in that the scapula has a greater expansion of the distal end from that of Diplodocus and Barosaurus, (2) the ischium is virtually indistinguishable except for size from those of both genera, and (3) the caudal vertebrae are more reminiscent of Barosawrzs. If BYU 9045 is caudal 1 or caudal 2 because of its very short centrum, then the spine is relatively low and transversely broad as in Barosaurus, in contrasted with Diplodocus. The midcaudals referred by Jensen (1985) to Supersawrus also exhibit the rounder, less exaggerated ventral sculpturing of Barosaurzs. Finalln the truly enormous size difference may be gauged from the length of the scapula of Supersaurus, which is 2.2 m in its somewhat flattened condition. This is 1.7 times as long as 1.3 m (measured on the curve) for the scapula of Barosaurzs (AMNH 6341). At one time, I thought that Supersaurus might be a gigantic species of Barosaurus, btt norv believe that there is evidence to indicate that it is a valid senus. A final de-
The Genus Barosaurus Marsh (Sauropoda, Diplodocidae)
.
7J
{/r tl\
Fig. 2.15. Comparison of lateral uieus of last dorsal: (A)
Arnphicoelias altus AMNH .5764; (B) Diplodocus "longus" USNM 10865 (after Gilmctre 1932); (C) Barosaurus lentus AMNH 5341 (data from Osborn and Mook 1e21 ).
f\
(*\
t
\*4 I
"-*\l
termination must await full preparation and study of the large Brigham Young University collection from the Dry Mesa Quarry. Comparing Barosaurus and Amphicoelias altus Cope is difficult due to the paucity of material of the latter. Its straighr, stovepipe-like femur, with an almost circular cross-section, is more reminiscent of Diplodocus (USNM 10865) than Barosaurus (AMNH 6341). On the other hand, the well-preserved posterior dorsal of A. altus (AMNH 5764) dilfers from both Barosaurws and Diplodocus (Fig. 2.15). Osborn and Mook (192I) concluded, probably correctly, that it is the last dorsal. It cannot belong to Diplodocus because its spine is straight and vertical, in contrast with Diplodoczs (USNM 10865), where it is angled anteriorly (Gilmore 1932). The spine of the last dorsal vertebra of Barosaurus is anteriorly angled but less so than in Diplodoczs. In the less likely event that the Amphicoelias dorsal is the next-to-the-last one, it cannot be Diplodoczs because its spine shows no sign of a cleft, which is present in that genus. The anteroposterior breadth of the spine of Ampbicoelids (AMNH 5764) greaily exceeds that of either Diplodocus or Barosdurus, and its pleurocoel is smaller than in either of these. How significant these differences are must await better material from the Cope locality, but it is doubtful whether Amphicoelias can ever be raised from the status of a nomen dubium. Finally, the large, incomplete scapula (AMNH 5764a), referred to Amphicoelias by Osborn and Mook (1.921), suggests that Amphocoelias is perhaps closer to Supersaurus than it is to either B arosaurus or D iplodo cus.
74 . lohn S. Mclntosh
Conclusions Bdrosaurus is a valid genus of the family Diplodocidae which is closely related to Diplodours, but it is more advanced in some respects and more primitive in others. Advance conditions are in the anterior part of the skeleton where Baros aurus has incorporated an
additional dorsal into the cervical series, leaving nine dorsals. Furthermore, the cervicals and anterior dorsals are up to 507o more elongated rn Barosaurus, and the forelimb is relatively longer. On the other hand, the tail of Barosaurtts is more primitive in that the centra are relatively shorter, the spines of the anterior caudals are shorter and unclefted, the caudal pleurcoels and transverse processes disappear several vertebrae anterior to those of Diplodoaus, and the ven-
tral sculpturing is less extreme. Finally, the typical Diplodocus-llke chevrons in the midcaudal region have a less developed anterior extension. The referral of Gigantosaurus africdnus to Barosaurus, though possible, should arvait further study. Acknowledgrnents. I am deeply indebted to Drs. Eugene Gaffney, Mary Dawson, the late Hermann Jaeger, the late Nicholas Hotton II, the iate Alan Charig, and John Ostrom for permission to examine materials in their care. I also want to thank Michael Brett-Surman and Robert Long for photographs of the Barosaurus cervicals. I have tried to measure personally as many of the bones mentioned in this paper as possible, but in some instances where this was not possible I have made use of published measurements of Lull, Janensch, and Foster as well as an unpublished measurement of the late C. C. Mook. I express my extreme gratitude to Allen McCrady for his painstaking, very skillful work on the neck of CM 11984. I am most grateful to Kenneth Carpenter and Virginia Tidwell for their help in preparation of the vertebral figures. References Cited
Bonnan, M. F. 2000. The presence of a calcaneum in a diplodocid sauropod. Journal of Vertebrate Paleontoktgy 20(l: 3f7423. Colbert, E.H. f96L Dinosaurs: Their Discouery and Their'Vlorld. New
York: Dutton. Curtice, B. D., K. L. Stadtman, and L.J. Curtice. 1996. A reassessment of Utrdsaurus macintosbi (Jensen, 19851. Museum of Northern Arizona
Bulletin 60:87-95. Foster, J. R. 1996. Sauropod dinosaurs of the Morrison Formation (Upper
Jurassic), Black Hills, South Dakota and \Wyoming. Contributions to Geology, Uniuersity of Wlyotning 31(1): 1-25.
E. 1908. Ostafrikanische Dinosauier. Palaeontographica 55: 105-144. Gilmore, C.W. L932. On a nen4y mounted skeleton of Diplodoats in the United States National Museum. Proceedings of the United States National Museum 81(18): 1-21. 1936. Osteology of Apatosaurus wrth special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 1,1,: 1-63.
Fraas,
The Genus Barosaurus Mrrsh (Sauropoda. Diplodocidae)
.
75
Hatcher, .J. B. 1901. Diplodocus (NIarsh): Its osteologn taronomy and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1,: 1,-63.
Holland, W. J. 1906. The osteology of Diplodoars Marsh. Memoirs of the Carnegie Museum 17 : 225-27 8.
1915. Section, "Paleontology." Annual Report of the Carnegie Museum for 1914.30-33. 1920. Section, "Paleontology." Annual Report of the Carnegie Museum for L9L9. 34-37. 1,922. Das Handskelett von Gigantosaurus robustus u. Brachiosaurus brancai aus den Tendaguru Schichten Deutsch-Ostafrikas. Centralblatt Mineralogie, Geologie und Palaeontologie (1922):
464480. Janensch, W. 1,929. Magenstein bei Sauropoden der Tendaguru-Schichten.
Palaeontographica. Supplement 7 (1): 137-143.
L935-I936. Die Schadel der Sauropoden Brachiosaurus, Barosaurus, und Dicraeosdurus aus den Tendaguru Schichten Deutsch Ostafrikas. (Schluss). Palaeontographica Supplement 7(1'): 14s-298. 1,961,. Die Gliedmassen und Gliedmassengurtel der Sauropoden der Tendaguru-Schichten. Palaeontographica Supplement 7(Iir: 177-235. Jensen, J. A. 1985. Three new sauropod dinosaurs from the Upper Jurassic of Colorado. Great Basin Naturalist 45(4): 697-709. Lull, R. S. 1.917 . Barosaurus: A gigantic sauropod dinosaur. Btilletin of the Geological Society of America 28: 214 (abs.) 1919. The sauropod dinosaur Bdrosanrus Marsh. Memoirs of the Connecticut Academy of Arts and Science 6: 1-42. Marsh, O. C. 1890. Description of new dinosaurian reptiles. American Journal of Science 39(3): 81-86. 1896. The Dinosaurs of North America. U.S. Geoktgical Suruey Annual Report 16: 1.33-244. 1898. On the families of the sauropodous dinosaurs. American Journal of Science 6(4):487-488. 1899. Footprints of Jurassic dinosaurs. American Journal of Scien
ce / t+ )i
/_./_
/ -^!_ J/_,
Mclntosh, J. S. 1981. Annotated catalogue of the dinosaurs (Reptilia, Archosauria) in the collections of the Carnegie Museum of Natural History. Bulletin of Carnegie Museum of Natural History, r1o t$. Mook, C. C. 1,91,7. The fore and hind limbs of Diplodocus. Bulletin of the American Museum of Natural History 37: 815-819. Nopcsa, F. 1930. Zur Systematik und Biologie der sauropoden. Palaeobiologica 3:40-52. Osborn, H. F. 1899. A skeleton of Diplodocus. Memoirs of the American Museum of Natural History 1': 191'-21'4. Osborn, H. F., and C. C. Mook. 1.921. Cdmardsdurus, Amphicoelias and other sauropods of Cope. Memoirs of the American Museum of Natural History, new series 3(3): 249-387. Osborn, H. F., and'W. Granger. 1901. Fore and hind limbs of sauropoda from the Bone Cabin Quarry. Bulletin of the American Mttseum of
Natural History 14(13): 199-208. H. G. 1869. Index to the Fossil Remains of Aues, Ornithosauria, and Reptilia. Cambridge, UK: Deighton' Bell, and Co.
Seeley,
76 o John S. Mclntosh
Sternfeld, H. L911. Zur Nomenklatur der Gattung Gigantosaurus Fraas. Sitzungsberichte der G esellschaft naturforschender Freunde du B erlin
1911(8):398.
'Wieland,
G.L. 7920. The long neck sauropod Barosaurus.
series (1326):
'Wild,
Science, new
528-530.
R. 1.991-. lanenschia n.g. robusta (E. Fraas 1908) pro Tornieria robusta (E. Fraas 1908) (Reptilia, Saurischia, Sauropodomorpha). Stuttgarter Beitraege Zur Naturkunde (B\ 173: 14.
The Genus Barosaurus Marsh (Sauropoda, Diplodocrdael
'
/7
3. Reassessment of the Early Cretaceous Sauropod Astrodon iohnsoni Leidy 1865 (Titanosauriformes ) KeNNrru CenppNTER AND VrncrNre Trownrr
Abstract Sauropod material from the Arundel Formation (Aptian-Albian boundary) of Maryland has been variously referred to Astrodon johnsoni Leidy 1865 or to Pleurocoelus nanus Marsh 1888. Most of the specimens are juvenile as demonstrated by the small size of the bones, the lack of neurocentral fusion, absence of an olecranon, and underdevelopment of muscle scars. Contrary to some recent statements, the Arundel sauropod is diagnostic. Only a single sauropod taxon is present in the Arundel Formation, to which the name Astrodon jobnsoni must be used under the Principle of the
First Reviser of the Inrernational Code of Zooloeical Nomenclature.
Introduction Prior to 7996,Early Cretaceous sauropods were assumed to be rare in North America, and most specimens were referred to Pleurocoelus, a taxon from Maryland first described by Marsh (1888). Since 1996, the diversity and number of Lower Cretaceous sauro78
pod specimens from North America have increased dramatically, although not all of the specimens have been formally described. The brachiosaurid Cedarosaurus weiskopfae (Tidwell et aI. 1999) and Venenosaurus dicrocei (Tidwell et al. 2001) are known from sediments low in the Cedar Mountain Formation (Barremian-basal Cenomanian) of Utah. The brachiosaurid Sattroposeiden proteles ('Wedel et al. 2000) has been described from a single specimen recovered from the Twin Mountain Formation of Oklahoma. Isolated teeth from Utah and Texas have been referred to Astrodon (Cifelli et a|. 1997), although this is probably not correct because similar teeth occur in other taxa. The brachiosaurid Sonorosatrus thompsoni (Ratkevitch 7998), from the Turney Ranch Formation of Arizona. may be Cenomanian in age. In recent years, Pleurocoelus has become a wastebasket for fragmentary Jurassic and Cretaceous sauropod specimens. The referral by Langston (1974) of various Texas specimens to Pleuro' coelus has resulted in a great deal of confusion about Pleurocoelus (e.g., Gallup 1975; Mclntosh 1990). The recent discoveries of numerous taronomically diverse sauropods from the Lower Cretaceous of North America highlight the need for a reexamination of the original material of Pleurocoelzs, which we present beiow.
Taxonomic History The first sauropod named from North America was Astrodon johnstoni, found in the Arundel Formation near Bladensburg, Maryland (Fig. 3.1). Although Joseph Leidy (1865) is usually credited with the name, in fact the genus was proposed in 1859 by Christopher Johnson. However, because no species was named by Johnson, Leidy is considered the author (permissible under ICZN 1999 67.2.2:l "if a nominal genus . . . was established before 1931 .. . without included nominal species . . . , the nominal species that were first subsequently and expressly included in it are deemed to be originally included nominal species"). The syntype is a spatulate tooth and a thin section of a second tooth (YPM 798) (Figs. 3.2G; 3.4A, B). Additional specimens of sauropods from the Arundel Formation were recovered by John Hatcher in 1887 and 1888, including a number of teeth with a similar morphology. As was common for the time, Marsh did not refer any of his specimens to a previously named taxon) especially one created by someone else. Instead, he proposed new names, Pleurocoelus nAnus ancPleurocoelus altus (Marsh 1888). The type series (syntypes) consists of several specimens, some of which were illustrated by Marsh in lBBB and more rn 1896. The specimens were transferred to the U.S. National Museum,'Washington, D.C. (now the National Museum of Natural History) in 1898-1899. John Hatcher (1903) offered the first review of the Maryland sauropods while describing some iuvenile sauropod bones from the Morrison Formation (see also Carpenter and Mclntosh 1994). He notes that it was he who had collected the specimens described by Reassessment of the Early Cretaceous Sauropod Astrodon iohnsoni Leidy
1865
'
79
Washington D.C.
Hanover Jessup Fig. 3.1. Geographic dis*ibution of Astrodon localities in eastern
Gontee
Maryland. Specific sites around Muir ki rk include : Cb ero kee Sdnford Brick Qwarry ( = Maryland Clalt Products Brick
Muirkirk
Quarry,), Duuall's lron Mine, Dut,all's Bank, Engine Bank, Henson's Bank, Island Bank, Latcbford Dump, Shea's Bank, Srt,ttnp Poodle r = Co[fin's LnBine Bank, Coffin's OId Engine Bank).
Bladensburg Washlngton D.C.
r..//
0
50km
-E
Marsh and that most of the specimens came from the same general location and horizon (for a history of the Maryland iron industry and the discovery of the Arundel sauropods, see Kranz 1996). Hatcher also notes that there was no evidence to indicate the presence of more than one species of sauropod, a point on which we concur. Hatcher concluded that Astrodon johnsoni had prioriry and that this name should be applied to the Arundel sauropod. Nomenclature stability could have been insured for the Arundel sauropod had it not been for Richard Lull. Lull (1917\ described and figured a representative sample of the Arundel sauropods at the U.S. National Museum, as well as specimens in Gloucher ColIege (the specimens have since been transferred to the National Museum of Natural History). Based on the relative abundance of the two size classes, he concluded that "Pleurocoelus abus. . . could have been the possessor of teeth like those of Astrodon lohnstoni. .. . It is therefore quite possible that Pleurocoelus altus should be considered as synonymous with Astrodon johnsoni, in
which case the latter name would take precedence" (Lull 1911, 203). By inference, P. nanus would be a separate taxon. Despite his
80
.
Kenneth Carpenter and Virginia Tidwell
prootic antotica
frontal laterosphenoid
adductor fossa
@ffi@ A
c
B
premaxillary process
fenestra ovalis
vidian
E
ffiffiffiffiftffiffi&ffiffim H
conclusion, he left the three taxa separate, which has led to the present nomenclatural confusion regarding Astrodon versus Pleurocoelus. Charles Gilmore (1921,) presented a brief summary of the Arundel fauna and attempted to head off the confusion when he concluded that "I think it preferable to assign all to the genus Astrodon, which clearly has priority" (Gilmore 1921,588). He listed three species ol Astrodon: A. nanus, A. ahus, and A. iohnstoni. After Gilmore's study, little mention was made of the Arundel sauropods until Kingham (1,962) did a brief review. He recognized only a single species of Arundel sauropod, Astrodon iohnsoni, but oddly he also synonymized Brachiosaurus with Astrodon as well, a synonymy not followed by subsequent authors. Ostrom (1970) discussed the Arundel sauropod in the context of sauropod material from the Lower Cretaceous Cloverly Formation. He agreed with Hatcher, Lull, and Gilmore that only a single sauropod taxon was present in the Arundel. However, he chose to follow Lull in retaining temporarily all three taxa; he was apparently not aware of Kingham's study. Langston (1,974) followed Ostrom and also retained all three taxa. However, he referred the postcrania of a Lower Cretaceous Texas sauropod to Pleurocoelus sp', thereby Reassessmenr
J Fig.3.2. Cranial bones o/Astrodon johnstoni as illustrated b1'Lull (1911). Supraoccipital in (A) posterior, (B) dorsal, and (C) anterior uiews. Left or b ito sp h e n o i d- lat er o sp h eno i d (alisphenoid of Lull 1911) in lateral uieu (D); parts labeled as c.urrently identified (not labeled by Lull). Left maxilla in lateral uiew (E), showing the premaxillary prucess as originall1, preserued (now missing; figure not originalll'labeled by 1,vllt. Lcft dentary in lateral uiew (F). Teeth were restored b1' Lull, original is edentulous. Teeth (to scale) include the holotype in buccal, marginal, and lingual uiews (G); anterior(l) semi-spdtuldte tooth in lingual and marginal uieuts (H); small poste-
riortll. semi-spatulate lootb in buccal, marginal, lingual, and marginal uiews (I); posterictr(?) semi-sptfiulate tooth in buccal,
rnarginal, lingual, and marginal t,iews (J).
of the Early Cretaceous Sauropod Astrodon iohnsoni Leidy 1865
.
81
changing the diagnosis of the genus, as can be seen by that given by Mclntosh \1990). Salgado et al. (1995) presented a preliminary review of Pleurocoelws, accepting P, nanus as a valid taxon and "Plewrocoelus" altus as a separate taxon distinguished by the distal end of the tibia. Nothing was said regarding Astrodon, although they did question the identity of the Texas sauropod as Pleurocoelus. Later, Salgado and Calvo (7997) reversed themselves, accepting only a single taxon, P. nanus, and they referred to the Texas specimens as Pleurocoelus sp. More recently Kranz (1998) has referred to the Arundel sauropod as Astrodon johnsoni. This brief historical view shows that earlier authors tended tt-rward Astrodon, and some, but not all, recent authors tended toward Pleurocoelus. Most of the authors, Salgado et al. (1995) excepted, consider the Arundel sauropod to represent a single genus and possibly a singie species. Our examination of the material also leads us to conclude that a single taxon is present, as first stated by Hatcher (see additional discussion below). Because Hatcher (1903) was the first reviser of the taxon, we have accepted his determination that Astrodon iohnsoni is the correct nomen under the Determination of the First Reviser: "'When the precedence between names li.e., Astrodon vs. Pleurocoelusl . . . cannot be objectively determined, the precedence [i.e., the name to be used] is fixed by
the action of the first author citing in a published work" (ICZN 1999, 24.2). Specifically, Hatcher (1903, 7I-12) conciuded:
1. comparison of the syntype teeth of Astrodon jobnstoni with those studied by Marsh showed "a verv striking similarity . . ." 2. that the material was collected from the same deposits (i.e., Arundel Formation) as the syntype teeth "likewise was found in a bed of iron ore near Bladensburg
Maryland"
3, the remains are from the same area, "since these remains were found essentiallg and perhaps identically, the same locality and horizon . . ." 4. the preservation is the same, "the great similarity which they exhibit . . ." 5. only a single species is present, "there appears no good reason for considering them as pertaining to either different genera or species."
6. therefore, " Astrodon johnstoni Leidy having priority should therefore be retained, whlle Pleurocoelus nanus would become a synonym." 'We are cognizant that this decision
will not be universally accepted, but not to accept Astrodon iohnsoni as the valid name wiil upset nomenclature stability because of the implication it would have that more than one species of sauropod is present in the Arundel Formation. Because such an implication was not substantiated by us, the oldest name available (ICZN 1999,23.1) is Astrodon
82.
Kenneth Carpenter and Virginia Tidwell
iohnsoni, as acknowledged by Hatcher (1903), and subsequently
by Lull (1911), Gilmore
(7921.), Kingham (1962), and Kranz
(1998). Although as shown above, both Astrodon and Pleurocoelus have been used for the Arundel material, suppression of the name Astrodon is not possible under the non-use guidelines of the ICZN (1,999,23.9.1,, "the senior synonym or homonym has not been use as a valid name after 1899") because Astrodon has been used as recently as 1998 (Kranz 1998\.In addition, the use of the name Astrodon does not promote taronomic instability or cause confusion, thus it cannot be abandoned in favor of Pleurocoelus (ICZN 7999, 23.9.3 with 23.2). Finally, the question of whether or not the syntype teeth are diagnostic needs to be addressed. Although the teeth are said to have come from Bladensburg, Maryland, there is no indication that they were found adjacent to one another. Given that most specimens from the Arundel Formation occur as isolated specimens, ir seems more probable that the teeth were not found together. Nevertheless, both Johnson and Leidy treated the teeth as belonging to the same taxon, and today they comprise the syntype for Astrodon iobnsoni (ICZN
1999 72.1..I: "all specimens on which the author established a nominal species-group taxon . . . in the absence of holotype designation . . . all are syntypes and collectively they constitute the namebearing type"; Art.73.2: "Syntypes are specimens of a type series that collectively constitute the name bearing type . . . for a nominal species-group taxon established before 2000 . . . all the specimens of the type series are automatically syntypes if neither a holotype . . ' or lectotype . . . has been fixed . . . all have equal status nomenclature as components of the name-bearing type"). That the syntypes probably came from more than one locality is acceptable by the ICZN (1999,73.2.3: "if the syntypes originated from two or more locali-
ties (including different strata), the type locality encompasses all of the places of origin").
'!7hen Leidy described the syntype of Astrodon johnsoni in 1856, the characters were unique at that time. Since then, however, other teeth have been referred to either Astrodon or Pleurocoelus (which was based on the assumption that this was the correct nomen for the Arundel specimens). Some of these specimens do not resemble any of the Arundel specimens (e.g., specimen of Langston 1974), whereas others do have some resemblance (e.g., Cifelli et al. 1997). Thus, under current rules of the ICZN (1999,13.1.1), the syntypes cannot "be accompanied by a description or definition that states in words characters that are purported to differentiate the taxon." However, this ruling applies to names published after 1930 (Art. 13). Because Astrodon johnsoni was named before that time, all that is required is that the name satisfy Article 11 (which it does, e.g., properly published, created from Latin alphabet, etc.), and "be accompanied by a description or definition of the taxon." Differentiation is not a requirement for the taxon named prior to 1931. Hatcher (1903), however, has made it possible for us to dif
Reassessment of the Earlv Cretaceous Sauropod Astrodon iohnsoni Leidv
1865
'
83
ferentiate Astrodon iohnsoni by his nomenclatural act under Determination of the First Reviser (ICZN 7999,24.2) whereby ali of the Arundel specimens, including the syntypes of Pleurocoelus nanus, were referre d to Astrodon johnsoni. In our studS comparisons were made with various taxa from the literature (citations in parenthesis), casts, and actual speci-
mens (denoted by catalog numbers). In addition, one of us (V. Tidwell) examined specimens at various museums in Argentina and England (see Acknowledgments, end of this chapter). Specrmens considered include: Aegyptosaurus (Stromer 1932 Lapparent 1960); Aeolosaurus MACN RN 147 (Powell 1986; Salgado and Coria 1.993a); Alamosaurus UT WL 476 (Gtlmore 1946; Lucas and Sullivan 2000); Andesaurus MUCPv132 (Calvo and Bonaparte 1991); Antdrctosaurers MACN 6904 (Huene 1929); Argentinosaurus PYPH-I (Bonaparte and Coria 1993); Argyrosaurus MLP 77-V-29-1, MACN VH 217 (Huene 1929;Powel| 1986); Brachiosaurzs USNM 5730, FMNHP25107 (Riggs 1903; Janensch 1.935-1936, 1950); Camarasaurzs DMNH 2850 (Mc-
Intosh et al. 1996a, 1996b; Ostrom and Mclntosh 1966): Cedarosaurus DMNH 39045 (Tidwell et al. 1999): ChubutisAurus MACN CH1.8222 (Salgado 1993); Epacbthosaurus MACN 1.3689 paraplastotype (Powell 1986, 7990; Gimenez 1992); Eucamerotus /oxl BMNH R 90 (Blows 7995); Gondwa-
natitan (Kellner and Azevdo 1999); Jones Ranch unnamed SMU 61732 (Langston 1974; Gomani et al. 1.999); Laplatasaurzs MLP CS 1128 (Huene 1.929;Powell1.979); Lirainosaurzs (Sanz et al. 1999); Magyarosaurzs (Huene 1.932); Malauisaurzzs MAL 181, 182, 200 (Jacobs et al. 1993; Gomani er al. 1999); I'Iewquensaurus MLP Ly 1-6 (Huene 1929; Powell 1986; Salgado and Coria 1993b); Paralititan (Smith et al. 2001); Phuuiangosaurus (Martin et a|. 7999); Rapetosaurus UA 8698, FMNH PR 2209 (Curry, Rogers, and Forster 2001); Saltasaurus (Powell 1992); Sauroposeidez OMNH 53062 (-ifedel et al. 2000); Isisaurus colberti (Jain and Bandyopadhyay 1997; Wilson and Upchurch 2003); Venenosaurus DMNH 40932 (Tidwell et al. 2001). Institutional abbreuiations. BMNH-British Museum Narural History, !-ondon, United Kingdom; DMNH-Denver Museum of Natural History, Denver, Colorado; FMNH-Field Museum of Natural Historn Chicago, Illinois; MACN-Museo Argentino de Ciencias Naturales, Buenos Aires, Argentina; MIOW-Museum of the Isle of Wight, Sandown, Isle of \X/ight; MLP-Museo de La Plata, La Plata, Argentina; MUCP-Museo de Ciencias Naturales de la Universidad Nacional del Comahue, Neuquen, Argentina; NSMT-National Science Museum Tokyo, Tokyo, Japan; PVPH-Paleontologia de Vertebrados, Museo "Carmen Fumes," Plaza Huincul, Argentina; SMU-Southern Methodist UniversitS Dallas, Texas; USNM-National Museum of Natural History, '$Tashington, D.C.; UT-University of Texas, Austin, Texas; YPM-Yale Peabody Museum of Natural History, New Haven, Connecticut.
84.
Kenneth Carpenter and Virginia Tidwell
Systematic Paleontology
Order Saurischia Seeley 1888 Suborder Sauropodomorpha Huene 1932 Infraorder Sauropoda Marsh 1878 Titanosauriformes Salgado et aI. 1997 Family incerta sedis Astrodon johnsoni Leidy 1865 Astrodon johnstoni Leidy 1865 Pleurocoelus nanus Marsh 7888 Pleurocoelus a/ras N{arsh
18
88
Astrodon nanus Grlmore 1921 Astrctdon altus Gtlmore 1.921
Syntypes-YPM 798 tooth and a thin section of another. Locality dnd horizon Arundel Formation, Potomac Group, near Bladensburg, Maryland. Age. Aptian (Doyle 1992). Referred material. See Table 3.1. All specimens are from the Arundel Formation, Potomac Group, Muirkirk, Maryland. Diagnosis: Supaoccipital with low, wide crest and tall, narrow foramen magnum. Cervicals short, very wide, camerate centra with very large pleurocoels that leave the centrum a mere sheil. Dorsals with deep, well-defined pleurocoels. Sacrals with deep pleurofossa, posterior sacrals rvith prominent groove on ventral surface. Anterior caudal centra ver-v short, circular, amphiplatyan; neural spines low. Coracoids very thick along edges and with a prominent lip. Radius with distinct ridge extending obliquely down shaft, and two small postero-distal condyles.
Description Some of the bones illustrated by Marsh (1888) and Lull (1911) have been damaged and processes have been lost. Other bones, notably a small femur (USNM 2263), cannot be found. To show what
the bones used to look like, Lull's illustrations are reproduced below to ease comparison rvith the bones as they are today.
Skull The cranial material is from different localities, hence from different individuals. Horveve! as noted by Lull, the individuals were all very young, as indicated by the lack of fusion of the braincase elements.
Supraoccipital. The supraoccipital (Fig. 3.3A-D) is low and wide, rather than tall as in most other sauropods (e.g., Camardsdurus, Brachiosaurus, Jainosaurus). It forms part of the lateral wall and the roof of the foramen magnum. The foramen magnum is tail and narrow as it is in the titanosatr Jdinosaurus and an unnamed titanosauriform from Texas (Tidwell and Carpenter 2003). Reassessrnent
of the Earlv Cretaceous Sauropod Astrodon iohnsoni Leidv 1865
.
85
Table 3.1 Referred Specimens of Astrodon and References of Figured Specimens
Material
CatalogNumber
Reference
maxilla maxilla with tooth maxilla maxillary tooth
USNM 5667 USNM 7288
Lull 1911, pl. 14,
altisphenoid pterygoid, frag. laterosphenoid supraoccipital dentary
357091.
USNM USNM USNM USNM USNM USNM
9152 5668
Lull 1911, pl. 16, fig.
5670 5688 5692 5669
Kingham 1,962, fig. 3b
1
Lull 1911, pl. 15, fig.3
I;
USNM 6104
Marsh 1896, pl. 40, frg. Lull 1911, pl. 14, fig. 5 Kingham 1962, fig.2b
tooth
USNM 357052 USNM 5691
Marsh 1896, pl. 40, frg.2;
roorh roorh
USNM 6105 USNM 6106
toorh tooth, frag. tooth tooth, frag. toorh tooth tooth toorh tooth tooth, frag. tooth tooth tooth
USNM 8443 USNM 8457 USNM 8458 USNM 8459 USNM 8460 USNM 8461 USNM 8462 USNM 8463 USNM 8464 USNM 8465 USNM 8466 USNM 8467 USNM 8468 USNM 8469 USNM 8470 USNM 8471 USNM 8472 USNM 8516 USNM 357080 USNM 357085 USNM 435228
dentary, frag. angular, frag.
roorh
tooth tooth, frag. toorh
tooth tooth tooth tooth tooth tooth tooth tooth tooth
pl. 79, frg. 4
USNM 481078 USNM 481088
USNM 6094 USNM 6:I22
Kenneth Carpenter and Virginia Tidwell
191'1,,
USNM 438042
cervical centrunr cervical centrum
?
Lull
USNM 442452
cervical centrum cervical centrum cervical centrum
axis
Lull 1911, pl. 14, fig. 5 Lull 1911, pl. 14, fig. 8
USNM 437986
USNM USNM USNM USNM USNM
AXIS
86 .
usNM
frg. 6
5452 57OO
5640 5641
5678
Marsh 1896, pl. 40, fig. 3; Lull 1911, pl. 15, fig. 2
Material
CataloeNumber
Reference
dorsal centrum
USNM 4968
Marsh 1888, figs. 1, 2; Marsh 1896. pl. 40. figs. 4, 5; Lull 1911, pl. 15,
dorsal centrum dorsal centrum dorsal centrum dorsal centrum dorsal centrum dorsal centrum dorsal centrum dorsal neural spine rib, frag.
USNM 5675 USNM 5705 USNM 6092 USNM 6097 USNM 6103 USNM 8499 USNM 85OO USNM 6110 USNM 5679 USNM 6102 USNM 8509 USNM 8515
fie.4
rib rib, frag.
rib
head
sacral centrum
USNM 4969
Marsh 1888, figs. 3, 4; Marsh 1896, pl. 40, figs
6,7;LulI fie. sacral centrum sacral centrum sacral rib sacral rib caudal centrum caudal centrum
USNM USNM USNM USNM
caudal
USNM 5372
1911, pl. 15,
5
5666 8475
5672 6117 USNM 2266 USNM 4970
Marsh 1888, figs. 5, 6; Marsh 1896, pl. 40, figs. 8, 9; Lull 1,9'1,1, pl. '1,6, fre.2 Manh 1896. pl. 40. figs. 10.
ltr Lull l9lt. pl. 16.
fre.1 caudal centrum
USNM 5639
Marsh 18q6. figs.38-4 l:
Lull 1911, pl. 1,6, fi1. caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal
centrum centrum centrum centrum centrum centrum centrum centrum centrum centrum centrum centrum centrum centrum centrum
USNM USNM USNM USNM USNM
2
5643 5644 5650 5651
5662
USNM 5663 USNM 5664
USNM USNM USNM USNM
5665 5680 5682 5683 USNM 5694 USNM 5702 USNM 7290
USNM 7291 USNM 7293 Reassessment of the Early Cretaceous Sauropod Astrodon iohnsoni Leidv
1865
.
87
Table 3.L (continued)
Refered Specimens of Astrodon and References of Figured Material
CataloeNumber
caudai caudal caudcI caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudai caudai caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal caudal neural neural
USNM USNM USNM USNM USNM USNM USNM USNM USNM USNM USNM USNM USNM USNM USNM
centrum
centrun
centrur centrum centrurr centrurr centrurr-
centrurr centrurn centrum centrum centrum centrum centrum centrum centrum centrum centrum centrurrt centrum centrum centrun-r
centruni centrum
centrur,
centrum centrum centrum centrum centrum centrum centrum centrum centrum centrum neural arch arch arch, frag. neural arch, frag. neural arch zygapophysis. frag. zvgapophl sis. frag. centrum centrum centrum, frag. centrum, frag, centrum, frag. centrum, frag. vertebra, frag. scapula, frag.
88 .
Kenneth Carpenter and Virginia Tidwell
73OO
7301
7302 7303
7319 8442 8455 8476
8477 8,178
8479
8480 8481
8482
8483 USNN,I 8484 USNM 8485 USNM 8486
USNM 8487 USNM 8488 USNM 8489 USNM 8490 USNM 8491 USNM 8492 USNM 8493 USNM 8494 USNM 8495 USNM 8496 USNM 8497 USNM 8498 USNM 8501 USNM 8506 USNM 3570,+5 USNM 357069 USNM 357084
USNM USNM USNM USNM USNM USNM USNM
357096
USNM USNM USNM USNM USNM USNM
6101
6111
8510 357039 357060 7287 357103 USNM 2264 357051 357083 357100 357101 357044 USNM 5677
Reference
Specimens
Material
CataloeNumber
scapula, frag. scapula, distal end coracoid, frag. coracoid, frag. sternal plate
USNM 8474 USNM 357093 USNM 6096
Reference
USNM 8473 USNM 357075 USNM 2263
humerus
Kingham 1,962, frg. 4 Lull 1911, fig. 16, fig. 5;
pl. USNM USNM USNM USNM
humerus, frag. hr,merrrc hrrmerrtc)
f
rr o frao
ulna, ulna, ulna, ulna, ulna,
6098
357066 357105 USNM 357106 USNM 5673 USNM 5674 USNM 9150 USNM 9153 USNM 357092 USNM 2263
humerus, prox. end humerus, prox. end
prox. end prox. end distal end distal end distal end
radius
1,7, frg. 2
5697
Lull 1911, fig. 16, fig.
5;
pI. 77, frg.2 radius, prox. end radius, prox. end metacafpal
USNM 9147 USNM 9149 USNM 2265
phalanx
USNM 2265
metacarpal metacarpal metacarpal, prox. end metacarpal metacarpal
USNM 5646 USNM 5648
--+^,-^-^..1
metacarpal
*-,^^^--^t lrrL rdLdrydr,
f-^-
f-^rra5.
metacarpal ntetacarpal, prox. end f*^'-^+^..^-^^lPdr! rra5. * -.^..^ -^^ f-^ y4'r| rraE.
ischium?
ischiurn, frag. ischium, frag. ischium femur
Marsh 1896, pl. 41, fig. Lull 1911, p1. 17, fig. 1 Marsh 1896, pl. 41, fig. Lull 1911, pl. 17, fig. 1
1; L;
USNM 5649
USNM 5658 USNM 5659 USNM 5686 USNM 5689 USNM 5695 USNM 5698 USNM 5699 USNM 8513 USNM 357056 USNM 6095 USNM 6118 USNM 357094
usNN{ 3s7107 USNM 2263
Lull 1911, fig. 16, fig.
5;
pL. 1.7, fi1. 2
femur, frag. t-emur,
distal end
femur femur, distal end
tibia tibia
tibia, distal end
USNM USNM USNM USNM
5696 6112 16710 452029 USNM 4971 USNM 5656 USNM 6114
Lull 1911, pl. 18, fig.3 Luil 1911, pL 1,7, frg. 3
Reassessment of the Earlv Cretaceous Sauropod Astrodon iobnsoni Leidv
1865
.
89
Table 3.1 (continwed) Refened Specimens of Astrodon and References of Figured Specimens Material
CataloeNumber
tibia, prox. end
USNM USNM USNM USNM USNM USNM USNM USNM
tibia fibula fibu1a
fibula 6bula, prox. end fibula, distal end metatarsal
Reference
6121 357T07 4971
Lull 1911, p1. 18, fig.3
5657 5676 6113 9155 2267
Lull 1911, pl. 17, fig. 3
Marsh 1896.
pl.4l.
3.4. s.6r Lull lell.
figs.
pl.
15, figs. 1, 2 metatarsal metatarsal metatarsal metatarsal metatarsai metatarsal
phalanx, pes
USNM USNM USNM USNM USNM USNM USNM
5660 5681 5687 6093 6119 6120 2267
Lull 1911, pl. 19, fig.1
Mar:h l8qo. pl. 41. fig'. 3, 4, 5, 6; Lull 1911, 15, figs. 1, 2
phalanx, indet. phalanx, indet. phalanx, indet. .holo.*
i.,-lot
phalanx, indet. nhalenw
inlct
phalanx, phalanx, phalanx, phalanx, phalanx,
indet. indet. indet.
frag. indet. frag. indet.
USNM USNM USNM USNM USNM USNM USNM USNM USNM USNM USNM
p1.
5642 5653 5654 5661 5690 6119 7294 7296 8514
357042 357049
Ventrally (Figs. 3.2C; 3.3C, D), the supraoccipital is open its entrre length, rather than partially constricted as in Cdmarasdurus (see Madsen et al. 1.995, fig. 27). The supraoccipital crest, seen on the posterior side above the foramen magnum (Fig. 3.3A), is low and very wide; it is narrow and sharp in Camarasdurus, and it is narrow and flat in Brachiosaurus and Jainosaurus. The sutures for the opisthotic and basiocciptal are triangular in outline, whereas they are more rectangular tn Camdrdsaurus. Two small facets above the foramen magnum are for the proatlas. C)rbitosphenoid and laterosphenoid. L:ull (1911) originally figured and illustrated these two bones as the alisphenoid (see Fig. 3.2D). These are separate today (Fig.3.3E-H), and we have been unable to articulate them as shown by Lull. In addition, the "hook-
90.
Kenneth Carpenter and Virginia Tidwell
Flg. 3.3. Cranial bones
of
Astrodon lohnstoni, Swpraoccipital /USNM 5592) in (A) pctsterior, (B) anterior, (C) dorsal, and (D) uentral uiews. Ahhreuialion: ps = proatlas shelf. Left laterosphenoid (USNM 5688 mislabeled as USNM 357091) in lateral (E) and medial (F) uieus. Left orbitosphenoid (USNM 5688 mislabeled as USNM 357091) in lateral 1C) and medial tH) uiews. I-eft maxilla /USNM 5667) m lateral (J) and medial (I) uiews; crowns of replacetnent teeth uisible at first and third alueoli.
9't :, '1*!r '€
G
Scale
in cm.
like" process illustrated by Lull, which is actually part of the laterosphenoid, can no longer be found. Neither element is complete, making comparisons with counterparts on other skulls difficult. If we accept the illustration given by Lull as accurate, then based on their relative sizes and positions, the fenestra include that for cranial n V and the vidian canal into the pituitary fossa. The problem with such an interpretation is the apparent absence of a fenestra for Reassessment of tl.re Earlv Cretaceous Sauroood Astrodon iohnsoni Leidv
1865
.
91
n II-IV. To resolve the problem will require that all of the pieces be relocated and rearticulated in the manner available to Lull. Maxilla. None of the maxillae (e.g., Fig. 3.3I, J) are as com-
plete as illustrated by Lull (see Fig. 3.2E). The maxillary body is wedge-shaped in profile, being deep anteriorly and tapered some-
what posteriorly. The sutural surface with the premaxillary is slightly convex and vertical in profile. In contrast, it is posteriorly sloped in Camardsaurus and Brachiosaurzs. In addition, the hooklike premaxillary process projects anteriorly and leaves little or no space for the subnarial fenestra. In Camdrasaurus, the process arises from the dorsal surface of the maxilla and does not protrude
anteriorly very much beyond the sutural surface. ln Brachiosaurus,
the process is similar to that in CamarasaurusJ but it originates more posteriorly on the dorsal surface of the maxilla. The alveoli of the Astrodon maxillae are damaged on all the specimens noq although Lull noted that a maximum of ten were present. Pterygoid. A pterygoid fragment was illustrated by Kingham (1962), but it was not found by us. Assuming that the illustration and identification are correct, the pterygoid is more arched dorsally than in Camarasaurus,but less arched than in Brachiosauras. It is difficult to compare the various processes (e.g., the quadrate process) because they appear damaged. It is therefore not known if there was originally a dorsomedially oriented, hook-like, basipterygoid process as in Camarls*urus. Dentary. The complete dentary illustrated by Lull (1911; see Fig. 3.2F) cannot be found, and those that remain are damaged (Fig. 3.3K). The dentary is most like that of Brachiosaurus, although it is proportionally deeper as compared to its length. Medially, the meckelian groove extends anteriorly towards the symphysis, which is missing. The coronoid process is long and low, as in Brachiosauras. Lull 11911) has noted that there are thirteen alveoli present. Lull also claims that none of the teeth present in the dentaries are spoon-shaped, a point we have been unable to substantiate. If true, then perhaps the slender, isolated teeth (e.g., Figs. 3.2H, I; 3 .4C, E) are from the dentary. All of the dentaries are edentulous. Teeth.Isolated brachiosaurid-like teeth from the Lower Cretaceous have frequently been referred to both Astrodon and Pleurocoelus (e.g., Langston 1.974; Cifelli et al. 1999; Kirkland et al. 1999) . Many of these identifications are based on superficial resemblance to teeth illustrated by Lull (1911; see Fig. 3.2G-J). Unfortunateln few of the identifications have been based upon direct comparisons with the holotype of Astrodon iobnstoni, nor have they been based on the large number of referred teeth from the Arundel Formation in the USNM. In fact, most of the non-Arundel teeth differ from the Arundel teeth, as noted by Maxwell and Cifelli (2000). Marsh's description of the teeth is, "their crowns are mainly compressed cones," thus not spoon-shaped. The teeth may actually be defined as semi-spatulate or semi-peglike (Figs. 3.2G-J; 3.4). The differences are probably due in part to the position in the mouth, with the broader teeth probably more anterior to the semi-
9r .
Kenneth Carpenter and Vrginia Tidwell
n*o
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Fig. 3.4. Teeth oi Astrodon johnsoni (A-F) and Langston Texas sauropod (G-H): wear facets denoted uith drrows.
F
h,l
Synttpe (YPM 798) in buccal (A) and lingual (B) ttieu,s (comldre u,ith Fig.3.3, G); stnall pctsterior(?) tootb (USNM 5105) in buccal (C) and lingual uiews (D) (compare tuith Fig, 3.3,l); larger, anterior(?) tooth (USNM 8516) in buccal (E) and lingual uiews (F). Tooth (USNM 187535) incorrectly referred by Langston (1974) as Astrodon from the Paluxy F ormation, Montague County, Texas (G and H). Note the prismatic angles on the crown (at lines) and tbe double uear facets. Scale in ctn.
peglike teeth based on comparison with other sauropods. All of the teeth share the feature of having the wear facet along the margin of the crown (Fig. 3.4), rather than centrally on the top or lingual side (Fig. 3.4G, H). Furthermore, most teeth show only a single wear facet, which begins near the top and expands toward the root as wear increases. The crown is typically smooth in the upper half of the buccal side, and faintly rugose or crinkled in the lower half, especially near the root. The crown may be very slightly constricted where it joins the root (e.g., Fig. 3.4E), but not always (e.g., Fig. 3.4C). On the lingual side, the crown is often finely crinkled under magnification, Reassessment
of the Early Cretaceous Sauropod Astrodon iohnsc,tni Leidy 1865
'
93
although this is highly variable. A weak vertical ridge may be present on the lingual side of rhe crown dividing the crown in half (e.g., Fig. 3.2I; 3.4F); its presence is probably dependent on its position
in the mourh. The tooth referred by Langston (I974) as pleurocoelzzs cannot be referred to that taxon. The crown has a distinct prismatic appearance on both buccal and lingual sides, with a sharp angle be_ tween "prisms" (Fig. 3.4G, H). This prismatic condition is unusual among sauropods. Furthermore, there are two wear facets, one at the lingual side of the tip and the other along one side of the tooth. Postcrania Few of the postcranial elements were found in articulation, and most were widely scattered. As a result, vertebral counts for the various segments are unknown. Nevertheless, most of the individuals were immature, as indicated by the near lack of fusion between the neural arches and their centra.
The cervicals and dorsals are characterized by very large cavi-
ties in the centra, especially in the dorsals, as noted by Marsh (1888): "The latter [dorsals] . . . have a very long, deep cavity on each side of the centrum, to which the proposed generic name refers." Such cavities have been variously referred to as ..pleurocoels" (Marsh 1888), "lareral depressions" (Lull 1911), and "pneumatic fossa" (Makovicky 1997). More recentll', pleurocoels in dinosaurs have been defined as "fossae and foramina,' (Britr 1997), that is, any depression and cavity in the lateral surface of the centrum (e.g., Mclntosh 1990; Wilson and Sereno 199g) or a deep excavation in the lateral sides of the centrum (Upchurch 1998). Bonaparte (1999) is one of the few modern authors who separates a depression in the lateral side of rhe centrum, which he calls a "lateral depression," from a cavity into the centrum, which he calls a "pleurocoel."'We have independently come to the same conclusion and note that it is not always clear whether an aurhor of a reference means that the "pleurocoel" is a shallow depression or a cavity. Considering that Marsh (1888), in establishing the name Pleurocoelws, created the term "pleurocoel" to mean a large cavity within the centrum, we propose that the term be restricted to such a cavity, and that the term "pleurofossa', (,,lateral depres_ sion") be used for the lateral depression on rhe sides of the centrum. In some sauropods (e.g., Argentinosaurus and Epacb_ thosaurws), a pleurocoel is developed within a pleurofossn in a manner analogous to the antoribital fenestra within the antorbital fossa in theropods. Ceruicals. Lull (1911) identified a damaged cervical centrum (USNM 5700) as possibly the axis, based on what appeared to be a coossified odontoid. Although he may be correct, he also notes that the posterior cotyle for articulation with the next cervical is shallow, suggesting that the centrum is a damaged dorsal. The cervicals are opisthocoelous, and the mid- and posterior cervicals have large pleurocoels separated medially by a thin vertical wall (Fig. 3.5A-D;
94.
Kenneth Carpenter and Virginia Tidwell
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trum is almost a shell of bone. Although known in some juvenile sauropods (Carpenter and Mclntosh 1994), they generally do not leave the centrum as a shell of bone.
large pleurocoels are
The centrum of the mid- and posterior cervicals are very wide compared to the height. The centrum is also wider than it is high in the titanosaurids lleuquensdurus and Sahosaurus. However, in these sauropods, the pleurocoels are not proportionally as large as in Astrodon. The neural canal in Astrodon is hourglass-shaped and has a thin ridge extending down its length (Fig. 3.5C).
Dorsals. Only anterior and mid-dorsal centra (Figs' 3.5E-I; 3.6C, D) are known, and these are opisthocoelous, with centra as tall as they are wide. This contrasts with the centra of Ewcamero/ns, whose centra are dorso-ventrally compressed. The pleurocoels ol Astrodon are very large and somewhat teardrop-shaped, being tallest anterioriy and tapering posteriorly as is characteristic of many titanosauriforms (Salgado et al. L997)' The pleurocoels of Cedarosaurus are lenticular and divided by lamina, unlike the simple pleurocoels of Astro don. The neural canal is also hourglassshaped in dorsal u;.v' (Fig. 3.5I), but it lacks the midline ridge seen in the cervicals. Although the posterior dorsals are not known,
R Fig. 3. 5. Representdtiue uertebrae
o/Astrodon johnsoni. P ostelrcr ceruical centrum (USNM 5678) in left lateral (A), anterior (B), dorsal (C), and uentral (D) uiews. Anterior dorsal centrum /USNM 4958) in left lateral (E), rilht lateral (F), anterior (C), posterior 1H1. and dursal rlt utews. Anlerior caudal neural spnte (USNM 5650) in right lateral (J), posterior (K), and le[t lateral 1Lt uiews. Anterior caudal TUSNM 8188t in posterior (M) and right lateral (N) (anterior tou,ard rigbt) uieuts. Mid-caudal centrum /U.SNM 4970) in left lateral (O), posterior (P), dorsal (Q), and uentrdl (R) uiews. Distal caudal in left lateral (S), antenor (T), and right lateral (U) uiews. Scale
in cm.
Reassessment of the Early Cretaceous Sauropod Astrodon iobnsoni Leidy
1865
'
95
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.
n. \ trtt,brte o/. Astrodon :s illustrated bt' NIdrsh
(.:r:rs(rni
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tnd Lull (1911). Posterior
cert,iccrl centrutn in left laterdl t'ietu (A) and cross sectiotl (B) shotuing the deuelopment of the
pleurococls. Dorsol centrttm in Ieft lateral (C) and posterior (D) uiews. Arrlerior sdcral cenlrum in Ieft lateral (E) and posterior (F) uiews. Anlerior caudal cenlrum in posterior (G), left lateral (H), and
dnterior (I) uieuts. Mid-caudal centrutll in left lateral 1J) and dorsdl (K) uiews. Distal caudal in anterior (L), left lateral (M), and posterior (N) uieuts.
based on the sacrals and mid-dorsals, the centra shourd be progressively more amphiplatyan and have smaller pleurocoels. Sacrals. The sacral centra (Figs. 3.6E, F;3.7) have an elongate
pleurofossa on each side, a character known in few titanosauriforms, although present in Diplodocus and variably found in camarasdurus. On the second(?) sacral (Figs. 3.6E, F; 3.7A_D), the pleurofossa is located posterior to the parapophysis and is partially excavated into it (Fig. 3.7A). The suture for the neural arch on the second sacral is located over the anrerior two-thirds (Fig. 3.7c). The anterior articular face is triangular (Fig. 3.7B), whereas the posrerior face is almost circular (Fig. 3.68). The last(?) two posrerior sacral cenrra are coossified (Fig. 3.7E-H). The centra are low and wide (Fig' 3'7E, G). The pleurofossa are low in height, elongated, and moderately deep. on the dorsal surface of the centra, the neural canal has a pair of circular fossa and another pair that are elongate (Fig. 3.7G). Ventrally; there is a shallow srlou. .rtending the length of the centra (Fig. 3.7H). This groove apparently did not extend the full length of the sacrum becauie it is not presenr on the second(?) sacral. caudals. Most of the vertebrae of Astrodon are caudars (Figs.
3.5M-U; 3.6G-N). The articular faces are circular and am_ phiplatyan. The anterior caudal centra are short anteroposteriorly and become progressively longer (compare Fig. 3.6Ft with Fig. 3'5N), reaching their maximum length in the mid-caudals (Figs. 3.5o; 3.6J). None of the caudal centra have either pleurocoels or pleurofossa. The neural arch of all caudals is locared on the anterior half of the centra, a titanosauriform character (Salgado et al. 7997). However, the anterior edge of the neural arch is set back
slightly as in Andesaurus, cedarosauru.s, and venenosauru.s. The floor of the neural canal is constricted between the pedicels (Figs. 3.5Q; 3.6K). The facets for the chevrons are small, short, and not
96
.
Kenneth Carpenter and Virginia Tidwell
k
ro".
A
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c
m
cm Fig.3.7. Sacral uertebrde of Astrodon johnsoni in right lateral
F
uiew (A) shou'ing Pleurofossa (arrou'), anterior uiew (B), dorsal uiew (C) (anteriol rigbt), and uentral uiew (D). Coossified posterior sacrals in right lateral
uieu (E) shouing Plettrofossa (arrouts), cross section (F), dr,trsal uiew (G) showing paired shalloa' fossa in the floor oi the neural canal prrows). and uentral uicw (H) showittg longitudinal grooue. Scale in cm.
very prominent. The neural arch of the most posterior caudal (Figs. 3.5S-U; 3.6L-N) is coossified to the centrum' suggesting that fusion of these two structures in the caudals occurs progressively
from back to front as in crocodiles (Brochu 1,996)' The anterior caudal neural spine is somewhat triangular, being anteroposteriorly longer along its top than along its base (Fig. 3'5J-L). The spine is simple. The postzygapophysis is developed at the base of the spine, rather than projecting posteriorly as in all other sauropods. However, neural spines are poorly represented elements in the very small juvenile specimens recovered to date. Further discoveries may allow us to determine if this feature is restricted to very young individuals. Ribs
A fragment of a large, hence adult, dorsal rib, was briefly deLull (1911). The tuberculum is very prominent and separated from the capitulum by a deep notch suggesting that it is an scribed by
Reassessmenr
of the Earlv Cretaceous Sauropod Astrodon iohnsoni Leidy 1865
'
97
Fig. 3.8. Large rib /USNM 8515/ o/ Astrodon ;ohn'oni shou'ing pleurocoel (arrotu) in web between capitulum dnd tuberculum. Scale in cm.
anterior rib (Fig. 3.8). A V-shaped depression in the web between the heads of the rib extends into a shallow pleurocoel on the posterior side, a condition also known in Venenosaurus, A Dneumarrc rib is characteristic of the titanosauriforms as defined tv '$Tilson and Sereno (1998), but this characer is also found in nontitanosauriforms, including Swpersaurus (Lovelace et al. 2003), and in a rib referred to Apatosaurus by Marsh \1896) (see Tidwell et ai. 2001; this rib may actually belong to Brachiosaurus). Forelimb Scapula. Only a fragment of the distal end of the scapular blade is known, and this is not very informative. Coracoid. The coracoids are incomplete (Fig. 3.9), but they do show unique features. First is the unusual thickness of the coracoid as compared to its size, even at the distal edges. The coracoid foramen must be set high, as in many titanosaurs, because it is nor visible on the fragments. Lull (1911) alleges that a small portion of the coracoid foramen is present, but we were unable to substantiate his claim. Furthermore, the anterior edge of the glenoid forms a promi-
98
.
Kenneth Carpenter and Virginia Tidwell
scapula facet
Fig. 3.9. Coracoid o/Astrodon jolrnsoni (USNM 6096) in uentral (A) and glenoid (B) uiews. Scale in cm.
nent lip more pronounced than that in Camarasaurus, and it is bordered by a deep notch. Hwmerus. The humerus is long and slender, although less so
than in Brachiosaurws and Cedarosaurus (Figs. 3.10; 3.11A-D). The deltopectoral crest is small in titanosaur fashion and is located a little over a quarter down the shaft; it proiects perpendicularly almost at a right angle, as rn Brachiosaurus, rather than medially, as in Cedarosaurus and titanosaurids. The proximal end of the humerus is slightly more expanded relative to the width of the shaft than it is in Cedarosdurus, but considerably less than it is in Chubutisaurus, Camarasdurus, or Brachiosaurus. Both the medial and lateral sides of the shaft are concave so as to give the humerus an hourglass shape. This profile makes the medial edge of the humeral shaft appear straighter than in Brachiosaurws. The shaft is not as slender in proportion to its length as in Brachiosaurus. The proximal end lacks the well-developed dorsal tuberosity for the M. subscapularis seen in many titanosaurids. This absence makes the proximal end appear slightly narrower than the distal end' Distally, the radial and ulnar condyles are not developed, possibly because of the immature nature of the bone. In ventral view, the articular surface is more rectangular than in Brachiosaurus. The supracondylar ridges on the posterior surface are not well developed. U/za. Neither ulna is complete (Fig. 3.12). The olecranon is Reassessment of the Early Cretaceous Sauropod Astrodon iobnsoni Leidy
1865
.
99
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absent, in marked contrast to the low olecranon in Cedarosaurus, Bracbiosaurus, and Camarasaurzzs. However, the ulna of a juvenile Venenosaurus has only a slightly developed olecranon (see Tidwell and ril/ilhite, this volume), whereas in the adult, it is rvell developed (see Tidwell et al. 2001). In dorsal view, the radial notch is well developed. The medial side of the ulna is almost straight and the lateral process almost perpendicular (Fig. 3.12A) as in Cedarosaurus and Brachiosaurus.
100
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Kenneth Carpenter and Virginia Tidwell
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Lull (19111. Hurnerus in posterior (A), proximal (B), distal (C), and lateral (D) uiews. Femur in posteric;r (E), proximal (F), uentral (G), and lateral (H) uteuts Tibia and fibula in anterior (l), proxinnl as illustrated (J) and corrected $) (fibula should not arttcttlata with the cnential tresl'. distdl (L), and posterior (M) as illustrated by
ulews.
Radius. The radius is very slender and straight (Fig.3.13). As Rapetosaurus, a prominent ridge extends obliquely down the posterior side. This feature contrasts with Cedarosdurus and Brachiosdurus, which have two ridges extending the length of the radius. The ridge begins just below the proximal end and terminates just above the distal ulnar expansion. The distal end has two small condyles on its posterior surface and is wide transversely. These features have not been found in any other sauropod and give the Astrodon radius a unique profile.
in
Metacarpals. The metacarpals are long and slender (Figs. 3.14A-H; 3.19A), a camarasauromorph character according to Salgado et al. (1997). However, the distal ends are undivided and lack ventrally distinct condyles, suggesting the absence of phalanges, a titanosaurid feature for Salgado et aL. (7997) and a titanosauriformes character for Wilson and Sereno (1998). However. some Astrodon metacarpals show poorly developed condyles on the posterior sides, similar to those in Venenosaurus and Antarctosaurus. Peluis
All that is known of the pelvis is an ischium. Ischium. The ischium is damaged (Fig. 3.15); nevertheless, it is complete enough to show that it is sharply bowed (Fig. 3.15B, D), and it is twisted along its long axis as in Camarasaurus and Brachiosaururs. The articular surface for the ilium is set on a short peduncle as in Andesdurtrs, Gondwandtitan, and Aeolosaurus; the peduncle is poorly developed in Camarasaurus and Brachiosaurus. Reassessment
ofthe Earlv
Fig. I.12. U/ra u/'Arrrudor. johnsoni. USNM J67J nr proximal (A) and left lateral (B) uiews. Scale in cm.
Cretaceous Sauroood Astrodon iohnsoni Leidv
1865
.
101
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l,l
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:nd tncdinl
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in cm.
tB). Scdle in cm.
Hindlimb Femur. The right femur has been damaged since illustrated by
Lull (1911; compare Figs.3.11E and 3.16). The shaft is slightly constricted just below midlength (Fig. 3.16), thus making it more slender than in Brachiosdunzs. The greater trochanter is slightly lower than the femoral head, as in Brachiosaurus and I'Jeuquensdurus, and it is not offset by a step as in Cedarosaurus. Just below the greater trochanter, the femur has a prominent, titanosauro1
I .
Kennetir Carpenter and Virginia Tidwell
morph-like lateral bulge. The fourth trochanter is a slight swelling located at midlength of the shaft. The distal condyles are more prominent than in Cedarosaurus and are separated by deep
+- greater trochanter
grooves.
\7e would like to take this opportunit,v to correct a common error in discussions of the greater trochanter in sauropods. This trochanter has, in recent years, been identified as the region dorsal and lateral to the femoral head (i.e., the top of the femur; see Borsuk-Bialynicka 1977, fig. 17A). However, as pointed our by Gregory (1918,535), "the greater trochanter in most repriles (including the Sauropoda) remains on rhe outer side of the shaft more or less near the proximal end. The outer portion of the head itself has sometimes been wrongly called 'great trochanrer,' especially in the femur of the Sauropoda." In a footnote he continues, "the proximal surface of the so-called great trochanter was co\rered by bursa . . . and that the gluteal muscles [i.e., M. iliofemoralis externus] were attached on the outer side of the great trochanter and not upon its top" (see Fig.3.16). Indeed, this area on the sauropod femur is often rugose, showing the insertion for various muscles (see further discussions by Carpenter and Kirkland 1998); it is also the region that corresponds to the proximal half of the "lateral bulge." In fact, development of the bulge is probably analogous to the development of the raised fourth trochanter, which, in sauropods, can appear as a broad ridge. The lateral bulge, is in fact, an extension of the greater trochanter; it is so variable in sauropods that its utility in phylogeny is questionable without quantification. Tibia. The tibia and fibula of the holotype Pleurocoelus altus (USNM 4971) cannot be found. Based on the illustrations of Lull
,q ,$
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Fig. 3.16. lentur of Astrodon johnsoni /USNI4 5696) irt posterinr uiew. Note large lateral
bulge (arrout). The trLte greater trochanter is noted. Scdle in crn.
*;.$, &*
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Fig. .3.17. Tibia of Astodor johnsoni /USNM .56.57) irtmedial (A), anterior (B), and laterttl (C) uiews. Distttl entl of tihh fUSNM 61.11) in onterior (D) and uetttral
E
B Reassessment
tr T
rLt t tcu s. lthrtlo irr tncdiLl t'ieu
.
Scdle in cm.
of the Early Cretaceous Sauropod Astrodon johnsoni Leidl' 1865
.
103
Fig. 3.11I-M), we find no reason to maintain this species as distinct contrary to Salgado et al. (1995; but apparently no longer distinct in Salgado and Calvo 1997). The distal end of the complete tibia of Astrodon (Fig.3.17A-C) is abraded, as indicated b1'the absence of the astragalar notch (this may be the tibia that (7911;
see
Salgado et al. (1995) used to separate P. dltus from "P. nanws"). This feature is well preserved on another, partial tibia (Fig. 3.17D, E). The tibia is more slender in proportion to its length than in Bra-
chiosaurus, but this may be a size- or weight-related difference and might change ontogenetically. The cnemial crest is ver1, prominent, much more so than rn Brachiosaurus, and it extends almost to midshaft (Fig. 3.1,7 A, C). The astragalar facet is not as open as in Brachiosaurus. The ventral surface of the distal end of the tibia resembles that of Brachiosaurus, contrary to Salgado and Calvo (1.997), and it is transversely wider than anteroposteriorly long. Fibula. The fibula is rather robust for its length (Figs. 3.11I, M; 3.17F). The fibula found r,vith a tibia (USNM 4971) cannot be located, but based on the illustration by Lull (1911), it does not differ markedly from another we refer to Astrodon (Fig. 3.17F). The fibula is slightly bowed in lateral view. The scar for M. iliofibularis is a well-defined ridge rather than the low, broad oval found in Camarasaurus. The proximal end is slightly C-shaped, rather than Dshaped as in Brachioslurus.
Metatarsals. The metatarsals are mostly of iuveniles (Figs. 3.18A-E;3.19B), but there is also one large aduit (Figs.3.18F G; 3.19D). They are the typical short, wide form of sauropods. Some of these show an articular surface on the distal end, indicating that 'We phalanges were present. do not accept the referral by Gallup (1989) of a pes from the Lower Cretaceous of Texas as Pleurocoelus for reasons discussed below. Thus, the number of claws on the pes remains unknown for Astrodon (= Pleurocoe/zs), contrary to Salgado et al. (7997).
Comparisons with Other Sauropods Sauropods from the Lower Cretaceous of Texas have been referred
to Pleurocoelws by Langston (1974), as well as more recently by Salgado and Calvo (1997). However, as Gomani et al. (1999) have
noted, the most proximal caudals of the Teras specimens are slightlv procoelous and grade posteriorly to plani-concave (see Table 3.2), rvhereas all the caudals of Astrodon are amphiplatyan. The hypantrum and hyposphene are also well developed in the Texas sauropod, but are absent in Astrodon (contrary to Tidwell et al. 1999, fig. 14; see Fig. 3.5K). Gomani et al. (1999) conclude that the Texas sauropod is a basal titanosauriform more derived than Brachiosauras, but less derived than Somphospondyli. Vertebrae belonging to other titanosauriformes show a variety of similarities and differences with Astrodon. The cervical vertebrae of Astrodon are proportionally much shorter and wider than those of Brachiosaurus and Sauroposeiden, suggesting a relatively 104
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Kenneth Carpenter and Virginia Tidwell
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ry
ffi "/: distal E
short neck compared with other North American titanosauriformes. All presacral centra of Astrodon exhibit a degree of internal excavation due to the extremely large pleurocoels beyond anything found in the titanosauriformes Brachiosaurus, Cedarosaurus, Andesaurus, or the 'Wealden brachiosaurs of England. This difference is even more noticeable in comparison with the basal titanosaur Malawisaurus and with more derived titanosaurs like Argentinosaurus, Aeolosaurus, and Saltasaurws, all of whom show very shallow pleurocoels in the presacral vertebrae. The unusually deep pleurocoels of Astrodon are sometimes ascribed to its immature development, as large pleurocoels have been considered a juvenile character in the past (Carpenter and Mclntosh 1,994).Indeed, presacral vertebrae in baby Cdmarasdunzs specimens from Oklahoma show deep pleurocoels (Carpenter and Mclntosh 1994), although not as deep as those in Astrodon. However, pleurocoels in the somewhat larger juveniles Cdmarasauras CM 11338 and YPM 1.91.0 are smaller in proportion to the centrum size, a trait that is also found in Bellusaurus and Phuwiangosaurus (Martin 1994). Astrodon shares with CedarosaLtrus, Epachtbosaurus, ChubutiReassessment
G
Fig. 3.18. Metcttalsals of Astrodon johnsoni. (A) Metatdrsdl i /USNM -5660) in proximal, dntelior, posterior, and distal uietus. (B-E) Melalarsnls r( SNM 22t,-1 in proximdl, dnterior, posterio/, and distal uiews. Scale in cm. Metatarsal (USNM 5687) irt dnterior dnd posterktr (l) ueus. Ungual oI Astrodon jol.tnsuni /USNM 2267) in laterdl and nredial uiews (G). Scale in cm.
of the Early Cretaceous Sauropod Astrodon iohnsctni Leidv 1865
.
105
lrl !\
{-}
ffi tifl t' '[
ru
J,ffi
ffi
4,Uer\ lf,lr*;{Cr?
WA
l'{ (1
Pwn
\_$
fh a$
ffi
Fig. 3.1 9. Metapodials of Astrodon johnsoni as illustrated
B
qcr*-/
bt Lull. Metdcdrpdl (A) in proxinlal, anterior, distal, and ntetlial t.,iews. Metatarsdl (B) in
proxinnl, anterior, distal, and nteLllrtl Ltie&'s. Distal ungual (C) in
ltroxirntl, lateral, dorsal, and tttteriol' ttieu,s. Metatdrsal (D) in
protittnl, anterior, and distal t,iett
ffiWW
s.
sAurus, and Andesau,,as pleurocoels that are teardrop-shaped and
posteriorly acumate. The dorsai centra of Astrodon are camerate in structure, in contrast to the camellate vertebrae of Cedarosaurtts, ChubutisAurus, and Malawislurus. The amphiplatyan anterior caudal centra of Astrodon are similar to those in Brdchiosaurus and Venenosaurus, though differing from the plani-concave anterior caudals of Cedarosaurus, "PelorosdLtrus," Chubwtisaurus, and Andesaurus. Although Calvo and Bonaparte (1991) describe the ante106
.
Kenneth Carpenter and Virginia Tidwell
TABLE 3.2. Terminology for Vertebra Types Based on Articular Surfaces of Centrum Etymology Term
G:
Greek;L
amphicoelous (G) double
- Latin
cavit_v
Definition deep cotvle on both articular surfaces.
amphiplatyan (G) double flat amphicyrtian (G) double convex
both articular surfaces flar.
biconvex
ball on both articular surfaces.
(L) two curves outr,vard opisthocoelous (G) behind cavity
plani-concave (G) flat concave
plani-convex
(G) flat convex
platycoelous (G) "flat"
cavity
-
biconvex.
ball'and-socket, with ball on
anterior surface and cotyle on posterior surface. one articular surface flat, the other concave. one articular surface f1at, the other convex. shallow cot\,le on both articu-
lar surfaces.
procoelus
(Ct hefore caviri
ball-and-socket, with cotl'le on anterior surface and ball on posterior surface.
Adapted iron-r'$(illiston 1925; Hoffstetter and Gasc 1969. Cot,vle articulatine surface of the cenrrum.
: cavit)'on
the
rior caudals of Andesaurzs as amphiplatvan, Salgado et al. (1997) call them slightly procoelous. A reexamination of the specimen shows that they are plani-concave, as in Cedarosaurus.In addition, three of the most anterior caudals are laterally compressed, producing the slight distal convexity that led Salgado et aI. (1997) to call them procoelous. The caudal vertebrae of Astrodon lack the lateral pleurofossa found in Venenosaurus, Cedarosdurus, and Malawisaurzs; however, it is possible that these features may develop later in life. In those Early Cretaceous titanosauriformes where the humerus is preserved, most display the elongate shaft found in Astrodon, in-
cluding Cedarosaurus, " P elorosaurus," Phuwiangosaurus, Chubutisanffus, and Malawisaurus. This elongate morphology persists into the Late Cretaceous, and it is found in the titanosaurs Laplatasaurus, Rapetosaurus, Lirainosaurus, Isisdurus colberti, and the juvenile titanosaur referred to Alamosaurus by Lehman and Coulson (2002), although it is not found in the adult specimen described by Gilmore (1946).The Astrodon humerus lacks a dorsal prominence lateral to the humeral head, as do most Early Cretaceous titanosauriformes; this process is only reported in Malawisaurus and Paralititan.In contrast, most Late Cretaceous titanosauriformes developed this process Reassessment
of the Early Cretaceous Sauropod Astrodon iohnsoni Leidv 1865
.
107
to varying degrees, except for Laplatasaurus, Isisaurtts colberti, and the juvenile material of Alamosaunts. All of the very slender radii in Astrodon more closely resemble
in Ceddrosaurus, Maldtuisaurus, and Rapetosaurus than those in the much heaver radii found in Venenosattrus, Chubutiscturus, and I'Jeuquenscturus. Neither the strongly developed, oblique ridge extending along the shaft nor the prominent distal condyles are found rnVenenosaurus or Chubwtisdurus. A complete set of metacarpals, unfortunately, is not known for Astrodon; just individual elements, all of which are very slender, as those
in Ve n en o s aur u s, Mal aw i s aur u s, Lap I a t a s dunzs, and Rap et o s auru s. Many of the Astrodon metacarpals possess a posterior ridge or process arising near the proximal end, and extending distally just past the mid-shaft region. Similar processes are found in Venenosdurus, Laplatasaurus, and R(tpetosaurus. However, in Antdrc' tosaurus and Chubutisdurws, the posterior process is located on the distal portion of each metacarpal, rather than proximally. Two characters often assigned to titanosauriform femora, a weildeveloped lateral bulge on the proximal end of the femur and a medial deflection of the femur head, are developed to varying degrees among the broad range of titanosauriform taxa' The lateral bulge shows an uneven distribution in titanosauriformes. Although clearly present in Chubutisdurws, I:Ieuquensdurus, Sabasaurus, and Rapetosdurus, in other taxa it is developed only moderately or poorly, such as in Cedarosaurus, Phuwiangosdurus, Aegyptosaurtts, and Argyrosaurus. Although this character is often difficult to assess, Salgado et al. (1997) attempt to quantif it among several sauropod taxa. It should be noted that moderate development of this character is also present in Apatosaurus femora (YPM 1980; NSMT 20375; casts on display at the Wyoming Dinosaur Center, Thermopolis, 'Wyoming). The medial deflection of the femur head is even more difficult to assess between taxa due to a number of factors: the relative length of the medial and distal condyles, which influences the inherent tilt of the femur; difficulty in pinpointing the greater trocanter on weathered or eroded proximal ends; and compression or taphonomic distortion on the proximal end. In only a few titanosauriform taxa is this character unmistakable: Astrodon, Cbttbutisaurus, Phuwiangosaurus, and Neuquensaurus. ln Antdrctosdurus it is variably developed, whereas in most others it is less apparent. Marsh (1898) iisted several characters in establishing the family Pleurocoelidae; however, all of the characters occur in other sauropods. Although Astrodon can be separated from other sauropods, there is no suite of unique characters that would war'We aiso note that there has been an errorant a separate family. neous assumption beginning with Marsh ( 1 8 8 8 ) that Astrodon is a small sauropod. However, as Kranz (1996) has noted, considerably larger specimens are known, including a femur that, when whole, would have been 1.25-1.50 m long. Such a large size piaces Astrodon well within the size range of another Lower Cretaceous brachiosaur, Cedarosaurus (see Fig. 3.20).
108
.
Kenneth Carpenter and Virginia Tidwell
Historically, there has been some concern regarding comparison of the juvenile Astrodon elements with those belonging to other adult sauropod taxa. Only a ferv studies have looked at ontogenetic variation in sauropods (Carpenter and Mclntosh 1994; Vilhite and Curtice L998; Martin 1994 Wilhite 1999; Tidwell and Wilhite this volume; Ikejiri et al. this volume). However, these studies suggest some general trends in morphologic change that may be applied to understand possible ontogeny in Astrodon An adult specimen of Astrodon is predicted to have more elongate cervical vertebrae, although never reaching the proportional length found in Brachiosaurus or Sauroposeiden; increased complexity of the pleurocoel cavity; or possible development of pleurofossa in the anterior caudal vertebrae. Less variability between juveniles and adults is found in the limbs, suggesting that adult Astrodon lin.'bs would closely resemble those of juveniles. Because a phyletic definition of the titanosaurids is presently underway by Curry-Rogers, no attempt has been made to replicate or impinge upon her work. Acknowledgments.'We thank Dr. Mike Brett-Surman and Mr. Robert Purdy (National Museum of Natural HistorS'Washington, D.C.) for access to the sauropod specimens from the Arundel Formation, and for the Brdchiosattrus skull from Marsh-Felch Quarry I. We also thank Mr, Cliff Miles (\Testern Paleontological Labs, Lehi, Utah) for a cast of the disarticulated skull of Camdrdsaurus grandis. V. Tidwell would also iike to thank the many individuals -"vho gave her access to the sauropods in their collections: Dr. Jose Bonaparte and Dr. Fernando Novas (Museo Argentino de Ciencias
F
ig. 3.20.
Skel etal r econstr uctioTt
o/Astrodon johnsoni. To
sc.ale
skeleton as a juuenile, use scale A; as an adult, use B. Courtesy of Greg Paul.
Reassessment of the Earlv Cretaceous Sauropod Astrodctn iohnsoni Leidy
1865
.
109
Naturales, Buenos Aires, Argentina); Dr. Oliver Rauhut (Museo Paleontologico Egidio Feruglio, Trelew, Argentina); Dr. Marcelo Requero (Museo Argentino de Ciencias Naturales, La Plata, Argentina); Dr. Leonardo Salgado and Dr. Jorge Calvo (Museo de ia Universidad Nacional del Comahue, Neuquen, Argentina); Dr. Rodolpho Coria (Museo Municipal Carmen Funes, Plaza Huincul, Argentina), Ms. Sandra Chapman (Natural History Museum, London, England), Dr. Martin Munt (Dinosaur Isle, Isle of V/ight, England). References Cited
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Kenneth Carpenter and Virginia Tidwell
4. Osteology of Ampelosaurws atacis (Titanosauria) from Southern France JeeN Lp Lonupr'
Abstract More than 500 titanosaur bones referred to Ampelosaurus atacis (Le Loeuff 1995) have been excavated since 1989 at the Upper Cretaceous locality of Bellevue in the Upper Aude Valley (Aude department, southern France). The skeleton of A. atacis is described and compared to other European titanosaurids. Evidence is accumulating that Late Cretaceous sauropods in Europe were more diverse than previously realized.
Introduction Late Cretaceous titanosaurids were first reported in Europe by P. E. Matheron rn 1.869, when he described Hypselosaurus priscus on the basis of fragmentary bones collected from the continental red beds of Provence in southern France. Matheron thought that H. priscus was a gigantic crocodilian and that belief prevailed as late as 1891. It was not until 1900 that Charles Dep6ret suggested that the material was from a sauropod. He also claimed that a second sauropod. Titanosaurus, was present in southern France. In 187-. 115
R. Lydekker described Titanosaurus as Z indicus on the basis of two caudal vertebrae from the Upper Creraceous localit.v of Bara Simla in India. In 1947, Albert de Lapparent follorved Dep6ret,s systematics, referring the titanosaurid bones from Provence to FL
prisctts and I indicus. However, these are here considered as nomina dubia (cf. Le Loeuff 1993; Wilson and Upchurch 2003). Dinosaur localities of the Upper Aude Valley \vere at first mentioned by the French zoologist and palaeontologist paul Gervais in 1877.He noted "des vertdbr6s fossiles d'Esp6raza, dans I'Aude', in the Mus6um National d'Histoire Natureile in Paris. Gervais also referred to "deux vertdbr6s caudales de Rbabdodon, d6couvertes un peu au sud du viilage de Fa," which were found b1. Alexandre Le,vmerie, a geologist from Toulouse (mentioned by Lapparent 1947). The local scientific bulletin (Bulletin de la Socidtd d'Etudes Scientifiques de I'Aude) has yielded further information about earlv fossil discoveries in the area (Le Loeuff 1991).In 1892, the architect Isidore Gabelle, from Couiza, made a list of the items in his important natural history collection, reporring "des vertbbr6sde reptiles et plusieurs fragments d'os de grands mammifdres dont I'un mesure 0.13 centimbtres [sic] de diamdtre, sortis du rerrain garumnien." Garumnien was a local stage created by Alexandre Leymerie for continental strata of Upper Cretaceous and Lower Tertiary ages, but Gabelle did not specifv the provenance nor illustrate his probable dinosaur bones. Further information about Gabelle's discoveries was given by the amateur archeologist Antoine Fages in 7928.He indicated that the bones had been found "au nord du village de Saint-Ferriol, prds de la corniche de Brantalou." Fages was active as an acrive amateur paleontologist and had worked in the field with the leading French paleontologist Charles Dep6ret. Fages had earlier presented to the Soci6t6 d'Etudes Scientifiques de I'Aude "des ossements p6trifi6s," r.vhich he had excavated "dans la vali6e du ruisseau de Granes. prbs des bains de Campagne" (Fages 1903). The secretary of the Society stated that "ces ossements p6trifi6s paraissent appartenir i un pachyderme" (Fages 1903). A few years later, Fages met r.vith the professional paleontologist Dep6ret, who possibly informed him of the exact nature of his discoveries. In 1909(a) Fages reported ..des ossements de dinosauriens" in the private collection of a schoolteacher named Mr. Brun in the viilage of Fa. Fages stated in 7928 that the dinosaur bones of Brun's collection had been found on the "rive gauche de I'Aude, en face des Bains de Campagne" (45). Fages reported the same year (1909b) from north of Rennes-leChiteau, in the ruisseau de Couleurs valley, "les couches sombres du Danien . . . trds caract6ristiques par les ossements de Tritonosaurus [sic] qu'on y trouve accompagn6s le plus souvent de parties de carapaces de tortues." The name Tritonosdurus deserves further explanations (it was later written Tritondusaurus by Fages 1928), as this genus name has never been used for a dinosaur. It is probably a mispelling of the name Titanosdurus, an Indian sauropod to l'n'hich Dep6ret
.
Jeln Le Loeuff
(1900) referred some vertebrae from the Upper Cretaceous of the Saint-Chinian area, 100 km northeast of the Upper Aude Valley. a new genus name Fages clearly did not intend Tritonosaurus ^s and he did not give any illustration or description of this material, which is now lost. The name Tritonosaurus cannot be considered as valid according to the International Code of Zoological Nomenclature. In 1935, Fages persisted in his misspelling, when he mentioned the discovery "d'ossements de Tritaunosaurus lsic] dans le danien du ruisseau du Rieutord" by Mallet, from Esp6raza,FranceAll these early discoveries were quickly forgotten. In his "M6moire sur les dinosauriens du Midi de la France," French paleontoiogist Lapparent (1,947) mentioned Leymerie's discovery (but he did not know about those of Gabelle, Brun, Mallet, and Fages). Lapparent concluded that "aucun vrai gisement i Dinosauriens n'est pr6sentement connu dans les Corbidres." French palaeontologists showed a lack of interest for dinosaurs (and even more for French dinosaurs), which led to forgetting the dinosaurs from the Upper Aude Valley (see Buffetaut et al. 1993). They were "rediscovered" in October 1982 following a fortuitous discovery of a dinosaur leg bone by a hunter near the village of Campagne-sur-Aude (see Le Loeuff 1991). Amateur fossil collectors from Esp6raza were attracted to the site and recovered a humerus and several caudal vertebrae from a deserted path eroded by running water (Bilotte et al. 1986 Clottes and Raynaud 1983). The site was further exca-
vated by professional paleontologists beginning in 7989 (Buffetaut et al. 1989). The richness of the site led paleontologists to prospect the Upper Aude ValleS resulting in the discovery of forty dinosaur localities, including many localities for dinosaur eggs. The Upper Aude Valley is now the best-known area in Europe for Late Creta-
ceous dinosaurs, and excavations are being conducted several months each year by the team of the Esp6raza Dinosaur Museum (MDE). Excavations at Bellevue Farm have produced abundant, wellpreserved titanosaurid material that was described as Ampelosdurus atacis (Le Loeuff 1995). Only a preliminary description of this taxon was given and only a few bones were iilustrated (i.e., a tooth and dorsal vertebrae). Later, the osteoderms of A. atacis were described (Le Loeuff et aI.7994). A large amount of new material has been unearthed at Bellevue, allowing for a more complete osteological description of Ampelosaurus. Despite some differences in the proportions of long bones, which might be linked to individual variation, it seems likely that only a single titanosaurid species is represented in this locality. All the titanosaur bones from Bellevue are provisionally referred to A. atacis.
Geographical and Geological Settings
Fifty kilometers south of Carcassonne (department of Aude, France; Fig.4.1), in the Upper Aude Valley, between the smali towns of Alet-les-Bains and Quillan, are exposures of continental Osteology oi Ampelosaurus atacis (Titanosauria) from Southern France
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O Campagnc-sur Aude
Fig. '1.1 . Location map indicating the Belleuue localitl, in Campagnesur-Attde. Scale bar: '10 ktn.
strata of Upper Cretaceous age around the villages of Campagnesur-Aude, Esp6.raza, Rennes-le-Chdteau, Fa, Granes, Brenac, and Saint-Ferriol. Dinosaur-bearing beds belong to the grds des Estous and marnes de la Maurine members of the Marnes Rouees Inf6rieures Formation (cf. Bilotte 1985). Usually referred as ro rhe Maastrichtian because of the discovery of an upper Campanian palynoflora in the underlying marnes de Campagne member (Bilotte 1985), the grBs des Estous could also be of upper Campanian age (M. Bilotte, pers. comm.). The type locality of Ampelosaurus (Bellevue Farm) shows a normal magnetic polarity, consistent with either hypothesis. The locality is situated at the bottom of the Marnes de la Maurine member. The dinosaur-bearine beds consist of 6ne- ro coarse-grained conglomerares and red maris deposited in a fluviatile environment. Most of the bones are disarticulated and many of them are much abraded. Plant, invertebrate, and verte, brate fossils have aiso been recovered at Bellevue (Table 4.1).
Systematic Paleontology Sauropoda
Titanosauridae Ampelosaurus atdcis (Le Loeuff 1995) Holotyp e. MDE-C3 -24 7, thr ee articulared dorsal vertebrae. Locality. Bellevue (C3), Campagne-sur-Aude, Aude department, France. Horizon. Marnes Rouges Inf6rieures Formation, Marnes de la
Maurine member, upper Campanian (Bilotte 1985).
to lower
Maastrichtian
Amended diagnosis. Axial part of the teeth cylindrical, with thin
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.
JeanLeLoeuff
TABLE 4.1. Vertebrates from the Bellevue Farm Locality, Upper Aude Valley, France
Osteichthyes Lepisosteidae
Lepisosteus sp. (isolated scales and teeth) Chelonia indet. (carapace fragments, two unidentified skulls) Crocodylia (teeth, isolated limb bones, three partial or complete skulls) AIlo dap
o
su ch
us pr
e
ce de
ns
crocododylian indet. Dinosauria Sauropoda
Titanosauridae Ampelosaurus dtdcis, Le Loeuff 1995 Theropoda Dromaeosauridae (teeth)
Ornithopoda Iguanodontia incertae sedis Rhabdodon priscrls, Matheron 1869 (cranial and post-cranial) Thyreophora
Ankylosauria indet. (dermal plates) Pterosauria indet. (fragmentarl' hollow bones) Aves
Family indet. Gargantuauis philoinos, Buffetaut and Le Loeuff L998 (synsacrum)
rostral and caudal expansions; constriction between the crown and the root; presence of an accessory spinal lamina in posterior cervicals; posterior centroparapophysial lamina very developed in dorsal vertebrae; well-developed accessory lamina between the postzygapophysis and the posterior centrodiapophyseal lamina in dorsal vertebrae; dorsal neural spines directed backward; two sacro-caudals in the sacrum; first three caudals procoelous with very elongated prezygapophyses; scapular blade unexpanded distally; shaft of the ischium unexpanded; and presence of osteoderms including spines.
Description Skwll
Cranium and teeth. A partial cranium consisting of frontals, parietals, supraoccipital, exoccipitals, basioccipital, prootics, Iaterosphenoids, orbitosphenoids, and the dorsal part of the parasphenoid-basisphenoid complex (C3-7 61.;Fig. 4.2). Almost no sutures can be distinguished, most of the bones being completely fused. The most conspicuous features of this cranium are the narrow supratemporal fenestra, the thick parietals forming a marked promontory similar to that of Antarctosaurus wichmannianws (cf. Osteoiogy ol Ampelosaurus cttdcis (Titanosauria) from Southern France
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r-r--T-t Fig. 1.2. Brdincase
of
Ampelosaurus atacis (C3-761) in tlorsal (A), uentral (B), rostral (C), occipital (D), and right ldtenl 1E1 uiews, Scale bar: 5 cm. Abbreuiations : bo = b asi o c cip ital; eo = exoccipital; fm = foramen Tnagnum;
fr
=
frontal; ls
=
laterosphenoid; ilc = nuchal crest; ctp = opisthotic; os = orbitosphenoid; pd = parietdl; pop
= paroccipital process; pr = prootic; so = suprdoccipital; stf =
slrprdtemporal fossa.
Huene 1929, pl.28), and a strong nuchal cresr. A partial dentary (MDE-C3-3961' Frg. 4.3) preserves nine alveoli. The tooth (C3-52; Fig.4.4) is 21 mm high and has a maximal width of 6 mm. The axial part of the crown is roughly cylindrical, with thin rostral and caudal expansions that stop at the base of the crown, making a slight constriction betrveen the root and the crown. Labially, there is an apical wear facet. This slightly spatulate tooth is quite different from the more usual peglike teeth of Titanosauridae. It is very different from the cylindrical titanosaurid teeth recovered in Romania and Spain, and referred to the genera Ma gy ar o s auru s and L i r a i n a s a u r us respecti vely. The generai morphology of the cranial elements of A. atacis (position of the foramina for cranial nerves, thickened parietals) is very similar to that of other titanosaurids such as A. wicbmaniannus and the braincase from Dongargaon (see Berman and Jain
1982). Another partial titanosaurid skuli was described from
120
.
Jean Le Loeuff
southern France by Le Loeuff et al. (7989), and shows some differences with Ampelosdurzzs (including the presence of facets around the occipital condyle), suggesting the presence of at least one other titanosaur species in the Upper Cretaceous of southern France (see aiso Le Loeuff 1998\.
Lig. 1.3. Right dentary o/A. atacrs (C3-396) in lateral (A), medial (B), and dorsal (C) uiews. Scale bar: 5 cm.
Axial Skeleton Ceruical uertebrde. Cervical r'ertebrae are uncommon in Bellevue and rnost of them are very poorly preserved; all show the characteristic cancellous bone of titanosaurids. The single anterior cer-
vical (C3-335; Fig. 4.5) is a partial centrum whose left side
is
crushed. The opisthocoelous, elongated centrum is 29 cm long. The poorly preserved ventral face is slightly concave transversally between the parapophyses, and flat or slightly convex more caudally. The well-preserved lateral face of the centrum is marked by a deep
pleurocoel. The laminar parapophyses originate jusr posterior to the cranial condyle. The preserved parts of the neural arch show that it possessed deep and narrow postspinal and prespinal fossae. Osteolog,v ol Ampelosaurus atdcis (Titanosauria) from Southern France
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121
t It
I
Fig. 1.1. Tooth of A. atacis 1C352) in labial (A) and lingual (B) uieu,'s. Scale bar: 5 mm.
rrrr-l Fig. 1.5. Ceruical uertebld o/A. atacis (C3-33,t) in dorsdl uiew. Scale bar: 5 cm. Abbreuiations: dp = diapophltsis; pp pdrdpophysis; po. = postzygdPoPht'sis; prz = preOtg.lpophrsis.
122
.
Jean Le
Loeuff
=
prsl asdl
cpr'l
poz
podl tpol
Fig. 1.6. Posterior ceruical uertebra of A. atacis (C3-265) in crntial 1A1 and caudal 1B) uieu s. Scale bar: 5 cm. Abbreuiations: dcdl = dnterior centrodiapophyseal lamina; asdl = a
cce
ss
o
rl
sup r adiap op
h yse
al
lamina; cpol = seal la m i na : q, gdp op h y s edl
c en I ro
p o st.)' Ba p o p h y
cp r I --
ce
ntr op
r
e
Iamina; dp = didpophysis: pcdl = p o
stet
ior
ce
ntr
o
diap op h.t
se
al
lamina; podl = s e al la mina ; = postzygapophlsis; prsl =
p o st zy go d iap op hy
prespinal lamina; prz
r-r-=r_1
p
r e4' gapop hy sis;
1t
oz
=
sprl =
sp i nop re z1'ga pophyseal la m i n,t :
ol = intrap lamina. tp
o
stzygap op hy seal
Regarding C3-265, there is an almost complete, poorly preserved, posterior cervical vertebra (Fig. a.6). The short centrum is 180 mm long and dorsoventrally flattened (anterior height is 125 mm; anterior r,vidth is 165 mm). It is proportionally much shorter than the anterior cervical centrum. The centrurn is strongly opisthocoelous, with a deep caudal concavity. The ventral face of the centrum is concave cranio-caudally. The parapophyses are broken, but extend from the anterior half of the centrum. They seem to have borne a dorsal longitudinal ridge, projecting from the deep pleurocoelous cavit.v, which is divided by this ridge. Osteologv ol Ampelosaurus atacis (Titanosauria) from Southern France
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123
The neural arch is very elongate laterally and dorsally, and is directed slightly caudally. The prezygapophyses are borne by the diapophyses. In cranial view, the diapophyses are ventrally convex, with two centrodiapophyseal laminae. The neural spine is wide and high, with a prespinal and a postspinal fossae. It is reinforced with spinoprezygapophyseal, spinodiapophyseal, and spinoposrzygapophyseai laminae. The spinodiapophyseal laminae show a slight constriction above the level of the prezygapophyseal facets; above this constriction, the neurai spine lvidens dorsally. An accessory spinal iamina runs from the spinodiapophyseai lamina to the prespinal lamina. The dorsal extremity of the neural spine is not well preserved. Cranially, the spine bears a prespinal ridge that is longitudinally striated. Laterally, the neural arch bears a deep triangular depression limited cranially by the spinodiapophyseal lamina, caudally by the centropostzygapophyseal lamina, and ventrally by the posterior centrodiapophyseal lamina. The constriction of the neurai spine, which is also obsen'able on the dorsai vertebrae, seems to be a characteristic feature of Ampelosaurus atacis. The deep prespinal and postspinal fossae are also remarkable on the cervical vertebrae. Dorsdl uertebrae. The dorsal centra are strongly opisthocoelous and have well-defined pleurocoels and no sagital ventral ridge; they show the characteristic cancellous tissue. Three anterior dorsal vertebrae are preserved, including a well-preserved juvenile
vertebra (C3-395) lacking the neural spine, prezygapophyses, postzygapophyses, and diapophyses. The centrum is very short anteroposteriorly, with elongated pleurocoels. The ventral face is concave transversely. In anterior vierv, the neural arch has very thick pedicels formed by the centroprezygapophyseal laminae. Above the
broken prezygapophyses, the spinoprezypapophyseal laminae defossa. Above the wide neural canal, the intra-
limit a prespinal
postzygapophyseal laminae demarcate two accessory fossae below the deep postspinal fossa. A postspinal ligamenrary cresr arises in the middle of this fossa. In lateral view, the centroprezygapophyseal and anterior centroadiapophyseal laminae delimit a deep infraprezygapophyseal cavitn which is divided by an accessory lamina interpreted as a poorly developed posterior centrodiapophyseal lamina. Mid-dorsals have more elongated opisthocoelous centra with well-defined pleurocoels. The neural spines are directed strongly backward (C3-247;Fig. 4.7), and they have a dorsal expansion. The posterior centroparapophyseal lamina is very developed in the first two vertebrae extending from the posterior extremity of the centrum to the centrodiapophyseal laminae. An accessory lamina joins the postzygapophysis to the posterior centrodiapophyseal lamina. Sacral uertebrae. Two poorly preserved sacra have been discovered. Based on a juvenile partial sacrum (C3-1469), it seems that the antepenultimate sacral vertebra was biconvex and articulated with two procoelous sacro-caudal vertebrae. A complete sacrum discovered in2002 should provide more information once prepara-
tion has been comoleted. 122+
.
Jean Le l_oeuff
Fig. 1.7. Dorsdl uertebrae of A. atacrs (C3-217; holotype) in catrdal 1A) dnd loteral 1Bt uicu s. Scalc bar: 20 on. Abbr,'uialions: acdl = anterior centr o d iap o p h t- s ea I lamin a ; cp ol = c en t ru pos I z) Bd pn pht'seol la rn i no : dp = diapophysis; ns = neural
spine; pcdl = posteriol
centrodiapophyseal lamind; pcpl p o
ster
ior centr
o p
dr d p op
h ),se
=
dl
Iam in a ; pr.tz = p ostz,\) gdp op h)r sis ;
pp = pdrapophysis; prsl = l)respindl lamina; prz =
prezygaPoPhl,sis; sPdl = s pin odidp op h.\ s edl ldtnirut ; sp o I = sp i n upusl )'ga P o Physeal lam i na.
Caudal uertebrae. The most anterior caudal vertebrae of Ampelosaurus were recovered associated with a juvenile sacrum. These vertebrae (caudals 1 and2r C3-1470 and C3-14721 appeat to have very long prezygapophyses set very cranially on the procoelous cen-
tra. The caudals appear not to have had a neural spine, or else it was very short. The third caudal has a very short centrum and is transitional with the fourth caudal (C3-1'477; both were found in articulation). The fourth caudal has a more "normal" morphologn with short prezygapophyses and a developed neural spine. The weil-preserved anterior caudals (fifth to eighth caudal; C3-58; Fig' 4.8) are deeply procoelous, bearing a well-developed neural spine that is cranially situated and that has cranial and posterior vertical laminae for ligamentary insertions. The mid-caudals are procoelous, with a very low neural arch (Fig. 4.9) set on the cranial half of the centrum. The centrum becomes progressively longer and lower in the caudal series. The prezygapophyses also become longer than in the anterior caudals (with the exception of the first three caudals). Distal caudals are rod-like but still distinctly procoelous (C3-101; Fig. 4.10).
Appendicular Skeleton Scapula. The best-preserved scapula shows a narrow scapular blade that is not expanded distally (C3-1043; Fig. 4.11). There is a ventral crest and a medio-dorsal protuberance around the base of the scapular blade. The scapula does not bear the internal crest characteristic ol Lirainosdurus clstibidi (Sanz et aI. 1.999). C3-1043 is the largest specimen in the collection with a total length of 91 cm. There is no fused scapulo-coracoid.
in outline, the scapular to close located dorsally, with the coracoidal foramen lateral surconvex The dorso-ventrally margin (C3-351; Fig.4.I2). Coracoid. The coracoid is roughly quadrangular
Osteologv oi AmpelosaurLrs atdcis (Titanosauria) from Southern France
'
12-5
Fig. 1.8. Anterior caudal of A. atacis (C3-58/ in right lateral uiew. Scale bar: 5 ctn. Abbreuiations: ns = neural spine: poz = postzygdpopbysis; prz = Prezygapophysis.
face shows a cranio-dorsal protuberance. In most specimens, the coracoidal foramen is open dorsally, but new marerial shows that it was dorsally closed by a thin blade of bone that is easily damaged. The cranial margin of rhe coracoid is thickened. Humerus. The humerus is one of the most common bones from the Bellevue locality, with eighteen thus far recovered. C3-S6 (Fig. 4.13) is robust, 63 cm long, and with proximal and distal ends that are remarkably expanded (proximal medio-lateral width is 26 cm; distal medio-lateral width is 19.5 cm). This makes the medial border strongly concave in cranial and caudal views. In caudal view, two ridges distally delimit a supracondylar depression.
126 o
Jean Le
Loeuff
Fig. 4.9. Middle caudal uertebra of A. atacis (C3-1009) in cranial 1A), posterior (B), dorsal (C), lateral (D), and uentrdl (E) uietus. Scale
bar: 5 cm. Abbreuialions: ns = neurdl spine; poz =
rT-r-1
postzygapop 4tsts: prz = pre4rgdpop hysts.
ffi
Fig. 4.10. Distal caudal uertebra
o/A. atacis (C3-1.01) in lateral (A) and dorsal (B) uiews. Scale bar: 5 cm.
Osteology ol Ampelosaurus atdcis (Titanosauria) from SouthernFrance
.
1.27
tu I .-rlts
A Fig. 4.1 1 . Left scapula o/ A. atacrs
(C3-1013) in medial (A) and lateral (B) uiews. Scale bdr: 20 on.
B '{.
.I Fig.4.1 2.Leftcoracoid o/A.atacis (C3-351)inmedial(A),dorsal(B),andlateral
128
.
Jean Le Loeuff
r-
(C) uiews.Scdlebar:70cm.
|:
,':.:i
..
:1:Lt: ,::;::.: '::
: '' ..'t
.,tla
. r:lf 1,'
:ia,t:,4
:'
tr tl;l
:.-'".
.d$-
l,t:llllid
:" ,'
...
'l' . f'.
t"t'
I I l
B
Fig. 1.13. Left humerus of L. atacis iCJ-86l in cranial (A) and caudal (B) uietus. Scale bdr:20 cn1.
Radius. C3-102 is an incomplete right radius that lacks proximal and distal extremities (Fig. 4.14). The shaft is distally quadrangular and proximally triangular. It bears a very prominent caudolateral, oblique, interosseous ridge. tllna. C3-1490 is the best-preserved specimen (Fig. a.15C-F). It is a small right ulna (total length 395 mm). The olecranon is bro-
ken on this specimen. The ulna is rather slender. The cranial face shows a distinct distal facet for the radius and a r,vell-marked interosseous ridge (C3-1296,Fig.4.15A, B). The lateral and medial faces join posteriorly to form the caudal border of the bone. The largest specimen is C3-1238, a left ulna with a total length of 725 mm. Metacarpals. Several isolated metacarpals are known but will not be described before articulated material is discovered. Ilium. Only very fragmentary ilia were discovered and will not be described here.
Pubis.
All of the pubes are incomplete, but from the analysis of Osteology of Ampelosaurus dtdcis (Titanosauria) from Southern France
'
129
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,4F..
j:'l':,il:" "
i'ft.t.
:1.::,,:::i. 'aa:.:.41.:
1I
:':',:,
'$; ,1..
I
Fig. 1.11. Right radius o/A. atacis (C3-102) in caudal (A),lateral (B), cranial 1(t, atrd medial 1D1 uieu's. Scdle
A
bar:10 on.
B
C
"L, !i
: Fig. 1.15. Right
tina o/A.
atacis
tC3-1296) in ntedial (A) and l.tterul (B) uiews; right ulna (C3l49At in caudal (C), lateral (B), crttti,tl (C), and medial uieu,,s. Sctle b,tr: 20 cm.
139 o
Jean Le Loeuff
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i:
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.
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s"J L-
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t
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Fig. 1.16. Left pubis o/ A. atacis (C3-wtnumbered: A-8, and C381: C-D) in lateral (A, D) and medial (8, C) uiews. Scale bar: 20 ct17.
the different specimens it was found that the pubic foramen was situated about two centimeters cranially of the ischiatic suture. The shaft is flattened and twisted distally, with a distal expansion (Fig. 4.1,6\.
Iscbium. The shaft of the ischium is unexpanded distally (it is even less expanded distally than proximally) and strongly flattened (FiS.4.1,7). The pubic symphysis is very well developed as in other
titanosaurids. Femur. The femur is the most common bone from the Beilevue locality, with twenty-seven more or less complete specimens recovered. The femur lacks any remarkable characters. As is usual in titanosaurids, the proximo-lateral deflection is prominent. C3-87 (Fig. 4.18C, D) is strongly flattened cranio-caudally. Osteology of Ampelosaurus atdcis (Titanosauria) from Southern France
.
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, ..{i Ftg. 1.17. Right ischia o/A. atacis left and C3-11.95, right)
l
i:
I
l
' ;,1"1."
lll,,
n
.i
1",,,'';;.,,1
,l
'C-l-i91.
u:
l.itertl (A-B) and medial (C-D)
l!!,l .,,,,
t ie:t -.. Scale bar: 20 cm.
,rl;iil..t
Tibia. C3-7303 (Fig. 4.19A, B, C) is a slender right tibia without any conspicuous feature. Fibula. C3-48 (Fig. 4.20) is a siender left fibula showing a sigmoid crest on the upper half of its cranio-caudally convex lateral face. The medial face is flat or slightly concave. C3-137 is a more robust right bone. Tarsals, nTetatdrsdls, phalanges. As for the metatarsals, I prefer to wait for the discovery of articulated material to describe the pes of Ampelosdurus. C)steoderms, Three different morphotypes have been recognized by Le Loeuff et al. (1994), including large spines (C3-L92,
132
.
Jean Le Loeuff
ll';
q,
Fig.4.18. Left (C3-1182: A, B) and right (C3-87: C, D) femora of A. atacis in cranial (A, D) and caudal (B-C) uiews. Scale bar:20
t".
L,. B
cm.
,]f
..
t.
B ' .:::i;Ll:$
C
I
t Fig. 1.19. Right tibias (C3-1303: A, B, C; C3-13B: E, F) and right
t)
tl
;;i l'l
astragalus (C3-1000: D) of A. atacis ln caudal (A),lateral (8, E), medial (C, F), and dorsal (L, uiews. Scale bar: 20 cnt.
Osteology of Ampelosaurus atacis (Titanosauria) from Southern France
.
133
i'! 'ti. .r
'..11-'.1 l:, .t. ' :,..
i
L:
i
h'
'
.l ..-.l..,ill
::,r,,.-
:
:, ,.::4
r
Fig. 4.20. Right (C3-18: A, B) and left (C3-137: C, D) fibulas of A. in lateral (A, C) and medial ^tacis (8, D) uiews. Scale bar: 20 cm.
{-
Ftg. 4.21,). Two large foramina open internaliy at the level of the spine, which is 12 cm tall. The internal face ts concavo-convex, with a longitudinal bilobate ridge that is less marked opposite of the spine. In side view, the osteoderm has two very different parts: half is low and thickens progressively to form a cingulum at the base of the spine. The two parts of the osteoderm have different textures: the lower part shows an irregular pattern of nodules and foramina, and the spine sholvs a more regular pattern of radiating fibers. The internal face of all osteoderms is smooth. with a oeculiar pattern of intersecting bone fibers.
Comparisons Titanosaurid remains are very common in most Upper Cretaceous European localities. Once referred to as Hypselosaurus priscus and Titanosaurus indicus (two species now considered as nomina dubia, cf. Le Loeuf f , 1993; Sfilson and Upchurch 2003 ), this material needs restudy, but this is complicated by the disarticulated and broken condition of the remains (cf. Lapparent 1947). All of these specimens should be provisionally considered as Titanosauridae indet. \fork in progress suggests that most of these bones belong to taxa different from A. araas. A. atacis is different from the two other valid European titanosaurids Lirainasdurus and Magylroscturus. The teeth referred to Magyarosaurus (Upper Cretaceous of Romania) and Lirainasaurus are cylindrical and lack the thin expansions of Am1
34 o Jean Le Loeuff
Fig.4.21. Osteoderm of A. atacrs (C3-192) in external (A), internal (B), and side uiews (C). Scale bar: 10
cn.
pelosaurus. The distal caudal vertebrae ol Lirainasaurus are dorsoventrally compressed. Its long bones are much more slender than in Ampelosaurus and its scapula bears a dorsal internal ridge that is absent in the French genus. Buffetaut et al. (1999) described a new
late Campanian-early Maastrichtian fauna from Cruzy (H6rault department). Titanosaurids are represented by a few limb bones, caudal vertebrae, and very slightly spatulate teeth. This material is also referred to Ampelosaurus. Conclusions Ampelosaurus atacis is among the best-known Titanosauridae from Europe, with more than 500 bones from the Bellevue bonebed. Its phylogenetic position among titanosaurids is beyond the scope of this paper. Indications are that European titanosaurid diversity was greater than previously suspected at the end of the Cretaceous, with probably four or five different species during the late Campanian and Maastrichtian (cf. Le Loeuff 1998). Recent exca-
vations
in
Bellevue (summers
of 2001, 2002,
and 2003) have
Osteology ol Ampelosaurus atacis (Titanosauria) from Southern France
.
135
yielded the first articulated skeleton of Ampelosaurus atacis. This material, which includes a well-preserved disarticulated skull is not yet prepared and will be described later. Acknowledgments.l thank all the \rolunteers who participated in the thirty months of excavations at Bellevue since 1989 and especially Alain Le Loeuff, who led the teams for many years, as well as the owners of the site, the GAEC de Bellevue. Special thanks to Lionel Cavin, Eric Buffetaut, Haiyan Tong, Michel Martin, Val6rie Martin, and Jimmy Powell for their help at various stages of this long-term field work; to Kenneth Carpenter and Virginia Tidwell for soliciting this paper and also for their (infinite) patience; to Leonardo Salgado for helpful comments; and to Jill Hall for revising the English grammar. The line drawings were made by G. Le Roux at the Dinosaur Museum in Esp6raza. The following institutions helped in funding the excavations: Conseil G6n6ral de I'Aude,
Ministdre de la Jeunesse et des Sports, FNADT, Pr6fecture de I'Aude, Conseil R6gional du Languedoc-Roussillon, SIVOM de la Haute Vall6e de I'Aude, CNRS, Association DINOSAURIA, Commune d'Esp6raza, and Communaut6 de Communes "Aude en Pyr6n6es." This paper is a contribution of the G.I.S. Pal6ontologie et S6dimentologie continentales (Universit6 de Toulouse III, Mus6e des Dinosaures d'Esp6raza). References Cited
Berman, D. S., and S. L. Jain. 1982. The braincase of a small sauropod dinosaur (Reptilia, Saurischia) from the Upper Cretaceous Lameta Group, central India, with review of Lameta Group localities. Annals of the Carnegie Museum 51(21): 405-422. Bilotte, M. 1985. Le Cr6tac6 sup6rieur des plate-fonnes est-pyr6n6ennes. Strata, s6lie 2, 5: 1-438. Bilotte, M., F. Duranthon, P. Clottes, and C. Raynaud. 1986. Gisements de dinosaures du Nord-Est des Pyr6n6es. In Les dinosaures de la Chine d la France, 151-160. Toulouse: Mus6um d'Histoire Naturelle.
Buffetaut, E., P. Clottes, G. Cuny, S. Ducrocq, J. Le Loeuff, M. Martin, J. E. Powell, C. Raynaud, and H. Tong. 1989. Les gisements de dinosaures maastrichtiens de la haute vall6e de I'Aude (France): Premiers r6sultats des fouilles de 1989. Comptes rendtts de I'Acadimie des Sciences de Paris 309 1723-1727. Buffetaut, E., G. Cuny, and J. Le Loeuff . 1993. The discoveri' of French dinosaurs. Modern Geology 18 161-182. Buffetaut, E., and J. Le Loeuff. 1998. A new giant ground bird from the Upper Cretaceous of southern France. Journal of the Geological Society ot' London 155:
l-4.
Buffetaut, E., I. Le Loeuff, S. Duffaud, L. Cavin, G. Garcia, H. Tong, D. \7ard, and ACAP. 1999. Un nouveau gisement de vert6br6s du Cr6tac6 sup6rieur ) Cruzy (H6rault, Sud de la France). Comptes rendus de I'Acadimie des Sciences de Paris 328 203-208. Clottes, P., and C. Raynaud. 1983. Le gisement i Dinosauriens de Campagne-sur-Aude-Esp6raza: observations pr6liminaires, premiers r6sultats. Bulletin de la Soci,lti d'Etttdes Scientifiques de I'Aude 83:
5-r4. 136 o
Jean Le Loeuff
Dep6ret, C. 1900. Sur les dinosauriens des 6tages de Rognac et de Vitrolles au pied de la Montagne-Noire. Contptes rendus de I'Acdddmie des Sciences de Paris 130 637-639. Fages, A. 1903. Ossements p6trifi6s du ruisseau de GranBs ) Campagne. Bulletin de la Sociltd d'Etudes Scientifiques de I'Aude 1,4:70. 1909a. Excursion du 26 avril 1908 i Antugnac, Croux, la Serpent, Fa. II-Notes g6ologiques. Bulletin de la Soci1td d'Etudes Scientifiques de I'Aude 20:1,6-1,9. 1909b. De Campagne-les-Bains i Rennes-le-Chiteau. Bulletin de la Socidtd d'Etudes Scientifiques de I'Aude 20 128-133. 1928. Excursion i Fa, Esp6raza et Couiza. Bulletin de la Soci1tl d'Etudes Scientifiques de I'Aude 32 45-47. 1935. Notice n6crologique de M. Mallet, d'Esp6raza. Bttlletin de Ia Socidtd d'Etudes Scientiliques de I'Aude 39 1,-94. Gabelle, I. 1892. Rapport sur l'excursion de la Soci6t6 du 12 avril 1891 n Couiza. Mdmoires de la Socidtd gdologique de France 56: 1-54. Le Loeuff, J.'1991. Les d6couvertes de reptiles m6sozoiques dans l'Aude. Bulletin de la Socidti d'Etudes Scienti/iques de I'Aude 91:23-28.
1993. European titanosaurids. Reuue de Pal6obiologie
7:
105-717. 1,995. AmpelosaLrrus dtctcis (nov. gen., nov. sp.), un nouveau Titanosauridae (Dinosauria, Sauropoda) du Cr6tac6 sup6rieur de la Haute Vall6e de l'Aude (France). Comptes rendus de I'Acaddmie des Sciences de Paris 321:693-699. 1998. New data on the Late Cretaceous titanosaurid diversity in 'V/orkshop the 'Western European islands. Abstracts Third European (Maastricht): Palaeontology 42. of Vertebrate Le Loeuff, J., and E. Buffetaut. 1998. A new dromaeosaurid (Dinosauria, Theropoda) from the Late Cretaceous of Southern France. Oryctos \: 105-1 12.
Le Loeuff, J., E. Buffetaut, L. Cavin, M. Martin, V. Martin, and H. Tong. 1,994. An armoured titanosaurid sauropod from the Late Cretaceous of Southern France and the occurrence of osteoderms in the Titanosauridae. Gaia 1.0: 155-159. Le Loeuff, J., E. Buffetaut, P. M6chin, and A. M6chin-Salessy. 1989. Un arridre-crAne de dinosaure titanosaurid6 (Saurischia, Sauropoda) dans le Cr6tac6 sup6rieur du Var (Provence, France). Comptes rendus de I'Acaddmie des Sciences de Paris 309: 851-857. Lydekker, R. 1877. Notices of new and other Vertebrata from Indian Tertiary and Secondary rocks. Record Geological Suruey of India 10:
38-41. Matheron, P. 1869. Note sur les reptiles fossiles des d6p6ts fluvio-lacustres cr6tac6s du bassin i lignite de Fuveau. Bulletin de ld Soci1td g1ologique de France 26: 781,-79 5 . 1891. Sur les animaur vert6br6s dans les couches d'eau douce cr6tac6es du midi de la France. Comptes rendus de I'Association frangaise pour I'Auancement des Sciences 20 345-379.
Sanz, J. L., J.E. Powell, J. Le Loeuff, R. Martinez, and J. PeredaSuberbiola. 1999. Sauropod remains from the Upper Cretaceous of Laio (Northcentral Spain): Titanosaur phylogenetic relationships. Estudios del Museo de Ciencias Naturales de Alaua 1,4:235-255. Wilson, J. A., and P. A. Upchurch. 2003. A revision o{ Titanosatrrus Ly-
dekker (Dinosauria-Sauropoda), the first dinosaur genus with "
Gondwanan" distribution
. Sy
stematic P alaeontolo gy
1
(
3
)
a
: 1 25-1 60.
Osteology of Ampelosaurus atacis (Titanosauria) from Southern France
.
137
Part Two Sauropods Young to Old
5. New Juvenile Sauropod Material from Western Colorado, and the Record of Juvenile Sauropods from the Upper Jurassic
Morrison Formation
JoHN R. Fosrpn
Abstract Juvenile Apatosaurus and Camarlsdurus specimens have been found among abundant remains of adults of these taxa at the Mygatt-Moore Quarry in western Colorado. The juvenile material consists of a dorsal centrum and left scapula of Apatosaurws and a dentary fragment, dorsal vertebra, and pubis of Camarasaurus.ln addition, there are three cervical centra and a dorsal centrum of unidentified sauropods from the quarry. The Kings View Quarry near Fruita yielded a partial, fragmentary specimen of a juvenile Camarasawnzs. According to a census of collections, approximately one in six sauropod specimens from the Morrison Formation are juveniles. The relative abundance percentages for juveniles of each genus are similar to those of adults.
Introduction Juvenile, baby, and embryonic sauropod dinosaurs have been reported from a growing number of sites worldwide in recent years (e.g., Martin L994; Chiappe et al. 2001), including the Upper 1,41,
Jurassic Morrison Formation of North America. Peterson and Gilmore (1902) described a very young Apatosaurus (CM 566) from the Sheep Creek area in \il/yoming. One of the most complete sauropods ever found (CM 11338) was described by Gilmore (1925) as a juvenile Camarasaurus specimen from the Dinosaur National Monument Quarrl'. Carpenter and Mclntosh (1994) described numerous baby sauropod elements from quarries near Kenton, Oklahoma. Embryonic and juvenile material has been found at the Dry Mesa Quarry near Delta, Colorado, including elements of Camarasaurus and Diplodocus (Britt and Naylor 1994; Curtice and \X/ilhite 7996). A partial pes of a haif-grown Cdrndrasaurus (SDSM 25338) was collected at the Little Houston Quarry in northeastern $Tyoming (Foster 1996a), and a humerus (SDSM 25413) and femur (SDSM 25334) of a juvenile Apatosaurus have been recovered from a site near Spearfish in western South Dakota (Foster 1,996a, 1996b). Curry (1999) studied several juvenile elements of Apatosaurtts from Cactus Park in western Colorado. Ad, ditional juvenile specimens have been recovered from sites in western Colorado, including the Mygatt-Moore Quarr,v, the Kings View Quarry, and a site in Sinbad Valley; these are described below. The Mygatt-Moore Quarry is located in west,central Colorado approximately 3 km from the Utah border, in the middle of the Brushy Basin Member of the Morrison Formation. The quarry matrix is a slightly greenish-gray siltstone with abundant carbonized plant fragments (Tidwell et al. 1998). Dinosaur bones in the quarry occur in an approximately 1.5 m-thick la,ver and are most abundant along the base of the deposit. Many bones are eroded on the ends and a number of them exhibit breaks that occurred before burial. Among the several hundred bones collected from the quarry over the years, no two were closely articulated, and there are very few cases of association. There are also a number of bones with tooth-scratch marks of predators, and shed theropod teeth are common at the site. In addition to the sauropods ApatctsAurus, Cctmdrasaurus, and Diplodocus(?), other dinosaurs found ar the quarry include Allosaurus and Mymoorapelta. The Kings View Quarry is also in west-central Colorado, about 3 km south of the town of Fruita near the Colorado River. The quarry is about 400 m west of Riggs Quarry 15 at Dinosaur Hill (site
of excavation of the Apdtosaurus, which is now mounted at the Field Museum in Chicago). The quarry is in the middle of the Brushy Basin Member in a 1.5 m-thick fine-grained sandstone with numerous small clay clasts. The bone is concentrared in the lower part of the sandstone unit. The site, worked rn 1993 and 2002, has yielded a juvenile Cdmarasduras, along with a sub-adult Stegosaurus ttbia, turtle shell, teeth of a theropod and a crocodilian, and one pterosaur lving bone. The site in Sinbad Valley was collected by Al Look in the 1930s and is most likeiy somewhere on the western or northern sides of
the valley in the Morrison Formation, just a few miles from the Utah border. Its exact location is unknown. 142
.
John R. Fosrer
The review of juvenile sauropods of the Morrison Formation is based on data from a minimum number of individuals (MNI) census of dinosaur specimens in museum collections (Foster 1998).In addition to counting MNI, the census noted juvenile specimens, which were defined as those less than 50% the approximate average adult size in linear proportions.
lnstitutional abbreuiations. BYU-Brigham Young Universitn Earth Science Museum; CM-Carnegie Museum of Natural History; M\fC-Museum of 'Western Colorado; OMNH-Oklahoma Museum of Natural History; and SDSM-South Dakota School of Mines and Technology.
Systematic Paleontology
Reptilia Saurischia
Sauropodomorpha Sauropoda Camarasauridae Camarasaurus grandis (FiS.
5.1A-D)
Referred Specimens. MITC 2538, two cervical vertebrae, three dorsal vertebrae, a cervical rib?, and a dorsal rib, from Kings View
Quarry; and
M\fC
3630 and a dorsal centrum from Mygatt-
Moore Quarry.
Description. MWC 2538 (Fig. 5.1A, B) is gently opistho-
coelous, and it is 130 mm long and 130 mm in diameter. The pleurocoels are deep, subtriangular, and set relatively high on the centrum; the pedicels are set at the upper level of the neural canal, and the neurocentral suture is unfused, although the neural arch, spine, laminae, and processes as a unit are only slightly displaced from the life position. The diapophyses are missing, and only the right parapophysis is preserved; anterior and posterior zygapophyses and the hyposphene are intact. The neural spine is broken above the level
of the postzygapophyses (at about the point of fusion of the left and right spinopostzygapophyseal laminae). The total height of the preserved neural arch and spine is 230 mm. A second dorsal vertebra is very similar, and the third consists of a partial centrum with an unfused and displaced neurai arch, and a transversely expanded neural spine. More of this specimen is likely still in the quarry, and a more detailed description wili be published later.
M\fC 3630, the centrum
(Fig. 5.1C, D), is gently opistho-
coelous, 95 mm long and 85 mm in diameter; the rounded triangular pleurocoels are 25-30 mm deep in the upper half of the centrum
and up into the lower-centrum half of the neural arch, both nearly meeting at the mid-line of centrum. The neural canal is nearly enclosed by the lower arch with pedicels almost co-joined at the top, near mid-centrum; the pedicels contain deep grooves indicative of unfused upper neural arches. 'Western Colorado New Juvenile Sauropod Material from
.
143
B
rj
3..Ji
,r{, rii:*ii.._tl
-{d
ll.:.lr' i. .t
Flg. -5.1. A-B: MWC 2538, Camarasaurus grandis dorsdl ueltebra in right lateral (A) and posterior (B) uietus, Kings View Quarrr. C-D: MWC 3630, Camarasaurus gr andis dor sal t.ertebr't centrum in dorsal (C) and rtgl:t lateral (D) uiett,s, MygattIfr:ore Quarry. (E) MWC 5051, C.rnrara'.rurur sp. Ieft pubis in I dt e r r I L,ietu, Mygatt- Moor e Qu,trrt. (F) M\Y/C 5009, Carnarasaurus sp. rigbt dentary irsgntent in lingual uiew, M1'gattlloore Qttarry. (G) MWC 1818, Apatosaurus sp. Ieft scapula m l,tt er ; I t, iew, Mygatt-Moor e Qutrry. All scale bars: 70 cnt.
ll..
i$..ri$
r:rtrr iail
Discussion. M\fC 2538 originally included another dorsal vertebra that is now missing. Fortunately lab photographs of this specimen indicate that it was a posterior dorsal, with a wide neural spine and laterally flared prespinal lamina characteristic of Cdmardsdurus. The height of the pedicels above the neural canal in the dorsal described above suggests assignment to C. grdndis (McIntosh 1990). The poor preservation of the distal end of the tibia? precludes any certainty in the identification of this element, but it most likely is part of the juvenile Camarasaurus specimen. The proportions of M\fC 3630 suggest that the specimen belongs to a young Camarasaurus, and the placement of the pedicels well above the level of the neural canal are also suggestive of C. grandis.
144
.
John R. Foster
Camarasaurus sp. fFig. 5.1E-F) Referred specimens. M\fC 5051, left pubis; MN7C 5009, fragment of right dentary with three teeth; both from Mygatt-Moore
Quarry.
Description. The pubis M\fC 5051 is 290 mm long and is well preserved along the shaft (Fig. 5.1E). Like much of the material from the Mygatt-Moore Quarry, however, the ends of the bone are poorly preserved, including the proximal end of the articular surface for the ischium. There is a large fracture crossing the shaft just distal to the clearly preserved obturator notch. Interestingly, this fracture occurs only on the lateral side of the bone, the medial side being entirely intact. The right dentary fragment MITC 5009 is 90 mm long and 65 mm deep (Fig. 5.1F). The three teeth (one partially erupted and two unerupted) are 1,7-1,8 mm wide, and are in alveoli above the deep groove for the splenial. The fragment seems to be from the posterior part of the dentary. Discussion. The pubis (M\fC 5051)most likely belongs to Camarasaurus because the proximal end lacks the ambiens process, which is characteristic of Morrison diplodocids. In addition, the length from the articular surface for the ischium down to the distal end of the shaft is longer than in diplodocids but not as deep as in Brachiosauras. MlfC 5009 closely matches the dentary and tooth structure of Camarasattrus (Madsen et al. 1995).
Diplodocidae Apatosaurus sp. (Figs. 5.1G; 5.24)
Referred specimens. M\fC 1848, left scapula; M'WC 5072, dorsal centrum; both from Mygatt-Moore Quarry. M\7C 645,left humerus, from an unknown quarry in western Colorado. Description. M\7C 1848 is a nearly complete left scapula 467 mm long (Fig. 5.1G); the distal end is slightly expanded and the shaft is only slightly bowed. M\fC 5072 is a dorsal centrum 74 mm long, 40-45mm in diameter, with moderately shallow pleurocoels and a deep neural canal. M\fC 645 is a humerus 600 mm long with a nearly symmetrical hourglass shape in anterior view and a distinct deltopectoral crest more than a third the length of the bone (Fig. 5.2A). The humerus is robust, with a minimum circumference: length ratio of 0.56. Discussion. The scapula (M\7C 1848)is clearly diplodocid because the distal end of the shaft is relatively narrow and not expanded as in Camarasdurus and Brachiosaurus. It differs from Diplodocus and Barosaurus in having the shaft of the dorsal process set at nearly a right angle to the main shaft of the bone, unlike the more acute angle seen in those genera. MIJfC 5072 is similar in overall appearance to a juvenile Apatosaurws centrum from Stovall Quarry 1 in Oklahoma (OMNH 1217).It lacks the slightly opisthocoelous centrum and more dorsally set pleuroco els of Ca-
New Juvenile Sauropod Material from 'Western Colorado
.
145
B yt-"t
1:,',,1:11::.y,;ral)y.,::l/t4tl'' .
.l
.,,u,%,,,o,*
r
lr Fig. 5.2. (A) MWC 61s, Apatosaurus sp. Ieit humerus m anterior uiew, unknown ktcality, Luestern
Colorado. B-D: MWC
1916, Sauropoda ceruical uertebra in dorsal (B), ight lateral (C), dnd left lateral (D) uiews, MygattMoore Quarry. E-F: M\YC 1917, Sartropoda ceruical uerlebra in dorsal ,Et and uentrdl 1l) uiews.
Mygatt-Moore Quarry. G-H: MWC 3828, Saurctpoda ceruical uertebra in dorsal (G) and uentral H ) uiews. M1'ga I I - Moore Q tta rr1'. All scdle bars: 10cm. 1
marasaurus. MI7C 645 is more robust than Brachiosaurus and slender diplodocids such as Diplodocus and Bdrosdurzs, and has a more symmetrical profile in anterior view than does Cdmarasdurus. It is therefore identified as Apcttosaurus.
Diplodocusi sp. (Fig. 5.3) Referred specimen. MN7C 641, seventeen mid-caudal cenrra, representing approximately positions 18-34; from Sinbad Valleg Mesa (or possibly Montrose) County, Colorado. Description. The centra are all elongare, with shallow ventral excavations on the more anterior elements. Centrum 18(?) shows a very shallow pleurocoel laterally. All centra are missing the neural arches and spines, and the chevron facets are not pronounced on the more anterior elements. Centra 21(?) and 22(?) are fused by a dark-red concretionary matrix, and this does not appear to involve
146
.
John R. Foster
I
Fig. 5.3. M\tlC 641, Diplodocusi sp., twelue of seuenteen caudal centra, Sinbad Yalley, Colorado. A, B. and D-M in right lateral uicw. (A) caudal 18, (B) caudal 19, (C)
ryK,W
caudal 19 in uentral uiew, (D) caudal 21, (E) caudal 22, (F) caudal 23, (G) cdudal 24, (H) caudal 29, (l) caudal 30, (J) caudal 31, (K) caudal 32, (L) caudal 33, and (M)
LKJ
M
-
rT
caudal 3,1. All scale bars: 10cm.
-
bone material. Centra range in length fuom 21.2 mm in number 18(?)to 140 mm in number 34(?). Discussion. Despite the ventral excavations of the centra being shallow and thus similar to Barosaurus, the specimen is identified as Diplodocas? based on the distinctly elongate centra. Bdrosaurws tends to have relatively shortened centra, and the ventral excavations of Diplodocus caudals can be quite variable in their depths (Curtice, pers. comm., 1997). Family indeterminate (Fig. 5.28-H) Referred specimens.
M\fC
1916, MN7C 1917,
M\fC
3828,
M\7C 3769, cervical centra; M\JfC 3738, dorsal centrum; all from Mygatt-Moore Quarry. Description. MIJfC 1976 is 104 mm long, 45-56 mm in diameter, and strongly opisthocoelous (Fig. 5.2B-D). The pleurocoels are asvmmetrical, the left with dual openings into a single chamber, the right with a deep anterior chamber and a relatively shallow posterior one. Most of the volume of the centrum) including the anterior ball, is holiow due to the ertensiveness of the pleurocoels. The length of the neural canal on both sides is bordered by the rugose pedicels for the unfused neural arches. Only the right parapophysis is preserved, and the ventral surface of the centrum is New Tuvenile Sauroood Material from Western Colorado
.
147
concave anteriorly, although not nearly to the same degree as in adults. M\fC 1917, M\7C 3769, and M\fC 3828 are all 65-70 mm long and 35-55 mm in diameter. Their relative lengths are shorter than MWC 1,91,6, and all are strongly opisthocoelous. Pleurocoels in each are deep, but not as elaborate as in MWC 1916, and parapophyses are preserved only in M\7C 1917 and M'WC 3828 (Fig. 5.2E-H). M\7C 3738 is 100 mm long and 65*90 mm diameter. It is moderately opisthocoelous and has pleurocoels that are simple but deep, nearly meeting along the centrum mid-line. The neural canal is wide (22 mm), as are the pedicels, which clearly preserve the rugose ridges characteristic of the unfused neurocentral sutures. The ventral surface of the centrum conrains two simple, anteriorly placed foramina. Discussion. \il/ithout preserved neural arches, neural spines, or ribs, cervical and anterior dorsal centra of sauropods can be extremely difficult to identify, so these juvenile specimens cannot be identified even as to family. There is considerable within-taxon variability in pleurocoel structure, and the relative lengths of the centra are similar in the Camarasauridae and some members of the Diplodocidae. M\X/C 1917, M\fC 3828, and MWC 3769 are par-
ticularly small among the Mygatt-Moore sauropod material and could be considered babies. These Mygatt-Moore Quarry specimens are similar in morphology and size to some of the Stovall Quarry 1 material from Oklahoma (OMNH 1242 and 1.249) identified as Camarasaurus by Carpenter and Mclntosh (1.994) and may belong to this genus. Discussion
In general, juvenile sauropods have been thought to be relatively rare in the Morrison Formation (Dodson 1990). Compared to their
likely proportions in standing populations, their fossil record
is
probably unrepresentative. However, the number of juvenile specimens that have been collected over the years is significant. A lack
of
publication on most of these specimens has perhaps led to an underappreciation of the extent of the juvenile record. There are more
than twenty localities in the Morrison Formation that now have yielded juvenile sauropod remains (defined here as elements <50'/' average adult size) in Colorado, Oklahoma, South Dakota, Utah,
and \il/yoming (Table 5.1). Based on an extensive MNI count, approximately 17"/. of the sauropod specimens in the Morrison Formation are juveniles, but
they account for 39"/" of the individuals at the quarries at which they are found (Table 5.2). Among the total juvenile sample, Camarasaurus accounts for 44"/", Diplodocus for 29o/o, Apatosaurus for 26oh, and Barosaurus for 1% (Fig.5.4). These relative abundances reasonably reflect those for adult MNI counts and estimates of biomass distributions among the taxa (Foster 2001). When measured by the percentage of localities with juvenile material at which each genus occurs, the relative abundances are similar to 143
.
John R. Foster
TABLE 5.1.
Morrison Formation Juvenile Sauropod Census Data, Summarized from Foster (1998)
County/State Genus Fremont, CO Camarasaurus
Quarry Marsh-Felch
Cactus Park, BYU
Mesa, CO
Dry Mesa Quarry
Mesa, CO
Juveniles Adults 2
4
Apatosaurus
1
3
Diplodocus
1
2 2
Bracbiosaurus Haplocanthosaurus
0 0
1
I
2
2
Apatosaurus
3
1
4
Cdmarasaurus
0
1
I
Diplodocus Apatosaurus
2
3
5
0 0
2
2
1
1
3
5
Supersaurtts Camarasaurus
Stovall Quarry
Cimarron, OK
1
ruller s JJ 1
Lawrence, SD
Dinosaur Nat'l Mon.
Uintah, UT
Bone Cabin Quarrl'
Albany. WY
Nail Quarry
Alban1', WY
Reed's Quarry
Albany','ifY
1
Reed's Quarry 3 Reed's Quarry 13
Alban1', Albany.,
\0Y !7Y
Sheep Creek Quarry C
Albanl', \7Y
Sheep Creek
Albany, \7Y
Quarry
Howe Quarry
E
Big Horn, rWY
Albany, $flY
3
Brachiosaurus
0
2 2
Apatosaurus
3
1
CAmarasaurus
1
1
4 2
Apatosaurus
1
1
2
Camarasaurus
0
1
1
t4
15
29
Apatctsaurus Barosaurus Camtlrasaurus Haplocanthctsaurus?
5 0
l1
16
5
5
6
t6
0
2
22 2
Camardsaurus
2
7
9
Bracbiosaurus Apatosaurus Diplctdocus
0
1
1
3
4
7
0
6
6
Apatosaurus
0
1
1
Diplodocus
1
0
1
Camarasaurus
1
1,
2
Diplodocus
2
Camarasaurus
2
4
6
Diplodocus
0
1
1
Camarasaurus
5
0
5
Camarasaurus
1
3
4
Diplodocus
0 0
1
1
Brachiosaurus?
I
1
Camarasaurus
1
1
2
Apatosaurus
0
1
1
Apatosaurus
I
2
3
Camarasaurus
1
0
1
Apatosaurus
0 0
1,
2
5
5
Barosaurus Camarasaurus
1
I
0
1
1
3
4
D ip
Reed's Quarry R
Total
2
I
o d o cus / B ar o
s
duru
s
Camarasaurus
2
2
Apatosattrus
I
I
4 2
Diplodocus
0
1
1
New Tuvenile Sauropod Material from Vestern Colorado
.
149
TABLE 5.1. (continued)
Monison Formation Juuenile Sauropod Census Data, Summarized from Foster (1998)
Quarry
County/State Genus
Little Houston Quarry
Crook, WY
Red Fork Powder River
Poison Creek Quarry
1
Johnson, V/Y
Johnson, \7Y
Johnson, WY
Total
Cantarasaurus
1
5
6
Apatosaurus
0 0
1
1
1
1
Apcttosaurus
0
1
1
Diplodocus
0
1
1
Camarasattrus
7
1
2
Apatosaurus
U
1
1
Diplodoas
1
1
Haplocanthosaurus?
0 0
1
1
Camarasdttrus
1
3
4
3
4 5
2
D ip
Sheridan College Quarry
Juveniles Aduits
I
o
d
ct
cu s / B Ar o
s
dur
Lts
Camardsdurus
1
Apatosaurus Diplodocus Haplocanth osaurus
1
3
4 2
0
2
Apatosaurus
1
5
\,
?I
Mygatt-Moore Quarry
Mesa, CO
Cantarasaurus
1
Kings View Quarry Sinbad Valley
Mesa, CO
Canurasaurus
1
0
1
Mesa(?), CO
Diplodocus?
1
0
1
77
152
229
Totals:
\1
TABLE 5.2. Occurrence Frequency for Morrison Formation Juvenile Sauropods Juvenile MNI Genus
(N:
77)
Number of Localities (22 sites)
Camarasaurus
a^ JA
19
Apatosaurus
20
10
Diplodocus
22
6
Barosaurus
1
1
Total number of sauropods (NINI) in Nlorrison Formafion, all quarries: .158 Total number of sauropods (NINI), quarries rvith juveniles: 229 Total number of juvenile sauropod specimens (MNI): 77 Percentage of juvenile sauropod specimens in Morrison Formation sample
(77l+ss):
17o/"
Juvenile/Adult specimen ratio, quarries with juvcnilcs, total sample \:7/ztrl: 0.31 Average individual juvenile/adult specimen ratio for 21 quarries rvith juveniles: 0.'10
150
.
John R. Foster
1%
I
Camarasaurus
tr Diplodocus ElApatosaurus E Barosaurus
Fig. \.4. Composition oI rht Morri s on F ormati on j uu eni le sauropod record, showing dominan ce o/ Camarasaurus followed 6y Diplodocus an d Apatosaurus, a patteln similar to that demonstrated by the sample of adub specimens. N = 77.
100% 90% 80%
(\
a no./^
tl
z
o
ov-/o
=I
50%
:
4oo/o
.9
o J o h
^^.,
20% Frg. .5.5. Frequency of occurrence of juuenile sduropod genera. Based on the number of sites at whicb the genus occurs diuided by
10% 0% Camarasaurus
Apatosaurus
Diplodocus
Barosaurus
the total number of sites witb iuuenile mdteridl. N = 22.
MNI counts. Camardsaulzs occurs at 860/" (19 of 22) of the localities with juvenile material, Apatosaurus at 45"/o, Diplodocus at 27o/o, and Barosaurus at 5% (Fig. 5.5). These abundances suggest that, although juvenile sauropods are underrepresented in the formation as a whole, their representation at certain quarries may accurately indicate the ecological associations of those based on straight
the sauropod faunas. Most quarries in the Morrison Formation are in either poorly drained floodplain mudstones or in sandstone units (Dodson et al.
New Juvenile Sauropod Material from'Western Colorado
.
151
1980). Quarry lithologies for juvenile sauropod sites are about
evenly split between these two types (at least seven sandstone quarries and seven mudstone quarries among the twenty-two known sites). Therefore, there does not appear to be any preferential bias for greater preservation of juveniles in any one lithology.
Juvenile sauropods were likely significantly more common in standing populations than is reflected in their overall fossil record, at least in part due to taphonomic bias against preservation of relatively smaller vertebrate elements. Limb elements of sauropods demonstrate only limited ontogenetic change in proportions (Curtice et al. 1997) (unlike theropods; Foster and Chure 1999), so it is unlikely that a significant number of juvenile elements have been overlooked due to misidentification; vertebral elements are only rarely misidentified as other adult taxa. Still, the sample of juvenile sauropod material from the Morrison Formation accounts for a respectable proportion of the overall record.
Acknowledgments.
I thank Jack Mclntosh and two
semi-
anonymous reviewers for comments that improved the manuscript. For access to collections used for this study I thank: Jeff Person and Rich Cifelli (OMNH); Kenneth Carpenter and Logan Ivy (Denver Museum of Nature & Science); Michael Brett-Surman (National Museum of Natural History); Ken Stadtman (Earth Science Museum, BYU); Dan Chure (Dinosaur National Monument); Charlotte Holton and Eugene Gaffney (American Museum of Natural History); Mary Ann Turner (Yaie Peabody Museum); Dave Berman (Carnegie Museum); Bruce Erickson (Science Museum of Minnesota); and Mike Flynn (Sheridan College). References Cited
Britt,
B. B., and B. G. Naylor. 1.994. An embryonic Camarasaurus (Dinosauria, Sauropoda) from the Upper Jurassic Morrison Formation (Dry Mesa Quarry, Colorado). In K. Carpenter, K. F. Hirsch, and J. R. Horner, eds., Dinosaur Eggs and Babies, 257-264. New York: Can.r-
bridge University Press. Carpenter, K., and J. Mclntosh. 1994. Upper Jurassic sauropod babies from the Morrison Formation. In K. Carpenter, K. F. Hirsch, and J. R. Horner, eds., Dinosaur Eggs and Babies, 265-278. New York: Cambridge University Press. Chiappe, L. M., L. Salgado, and R. A. Coria. 2001. Embryonic skulls of titanosaur sauropod dinosaurs. Science 293: 2444-2446. Curry, K. A. 1999. Ontogenetic histology of Apatosattrzs (Dinosauria: Sauropoda): New insights on growth rares and longevitl,. lcturnal of Vertebrate P aleontology 19 : 6 54-66 5. Curtice, B. D., and D. R. Vilhite. 1996. A re-evaluation of the Dry Mesa Dinosaur Quarr,v sauropod fauna with a description of juvenile sauropod elements. In A. C. Huffman,'$7. R. Lund, and L. H. Godwin, eds., Geology and Resources of the Paradox Basin, 325-338. Utah Geological Association Guidebook, no. 2-5. Salt Lake City: Utah Geological Association. Curtice, B. D., J. R. Foster, and D. R. I7ilhite. 1997 . A statistical analysis of
152
.
John R. Foster
sauropod limb element. Journal of Vertebrate Paleontology 3 supp., 1.7:411'. Dodson, P. 1990. Sauropod paleoecologl.. In D. B. Weishampel, P. Dodson, and H. Osm6lska, eds., The Dinosauria, 402-407. Berkeley: University of California Press. Dodson, P., A. K. Behrensmeyer, R. T. Bakker, and J. S. N{clntosh. 1980. Taphonomy and paleoecologv of the dinosaur beds of the Jurassic Morrison Formation. Paleobiology 6: 208-232. Foster, J. R. 1996a. Sauropod dinosaurs of the Morrison Formation (Upper Jurassic), Black Hills, South Dakota and 'Wyoming. Contributions to Geology, Uniuersity of Wyoming 31: 1-25.
1996b. Fossil vertebrate localities
in the Morrison Formation
(Upper Jurassic) of u.estern South Dakota. In NI. Morales, ed., Tbe Continental .lurassic, 255-264. Museum of Northern Arizona, Bulletin no. 60. Flagstaff: Museum of Northern Arizona. 1998. Aspects of vertebrate paleoecology, taphonomy, and biostratigraphy of the Morrison Formation (Upper Jurassic), Rocky Mountain region, western United States. Ph.D. diss., Universit.v of
Colorado, Boulder.
2001. Relative abundances of the sauropoda (Dinosauria, Saurischia) of the Morrison Formation and implications for Late Jurassic paleoecology of North America. Mesa Sctuthwest Museum Bulletin 8: 47-60. Foster, J. R., and D. J. Chure. 1999. Hindlimb proportion allometry in juvenile to adtlt Allosaurrs (Dinosauria, Theropoda). Journdl of Vertebrate Paleontology 3 supp., 19: 45A. Gilmore, C. \7. 1925. A nearly complete articulated skeleton of Camardsdurus, a saurischian dinosaur from the Dinosaur National Monument, Utah. Memoirs of the Carnegie Museum 10 347-384. Madsen, J. H., Jr., J. S. Mclntosh, and D. S. Berman. 1995. Skull and atlasaxis complex of the Upper Jurassic sauropod Camarasaurus Cope (Reptilia:Sar.rrischia). Bulletin of Carnegie Museunt of Natural History 31: 1 -1 1 5. Martin, y. 1994. Baby sauropods from the Sao I(hua Formation (Lower Cretaceous) in northeastern Thailand. Gaia L0: 147-153. Mclntosh, J. S. 1990. Species determination in sauropod dinosaurs rvith tentative suggestions for their classification. In K. Carpenter and P. J. Currie, eds., Dinosaur Systematics: Perspectiues and Approaches, 53-69. New York: Can.rbridge Universit,v Press. Peterson, O. A., and C. \f. Gilmore. 1902. Elosaurus paruus: a new genus and species of the Sauropoda. Cdrnegie Museum Annals 1: 490-499. Tidwell,'W D., B. B. Britt, and S. R. Ash. 1998. Preliminary floral analysis of the Mygatt-Moore Quarrv in the Jurassic Morrison Formarion, rvest-central Colorado. Modern Geolosy 22: 341-378.
New Juvenile Sauropod Material from Western Colorado
.
153
6. New Adult Specimens of Camaras*urus Lentus Highlight Ontogenetic Variation within the Species Thxpnrro Ixrlrnr, VrncrNrA Trnwnrr, AND Devro L. Thpxrpn
Abstract The recent discovery of two aduk Camardsaurus lentus skeletons from a single quarry in north-central Nfyoming provides new insights into the morphology, as well as the ontogenetic and individual variation, within this species. More importantly, these specimens provide characteristics useful for separating C. lentus and C. supremus. The specimens allow the first description in an adult C. lentus of the cervical/dorsal transition, which is crucial in species determination among Camarasaurzs. The massive, short, neural arches in anterior and mid-dorsais are diagnostic in C. lentus and differ from the very tall, slender arch in C. grandis. Moreover, Tshaped neural spines in anterior caudals are not present in C. lentus, but only in C. supremus and C. grandis. These new specimens also clarify the taxonomic status ol C. supremzzs, The new specimens display unusually large dorsal centra u'hen compared with the overall size of the vertebrae, and fewer aveolae in the dentary and maxilla in comparison with other described skulls. An extraordinary degree of rugosity on the articular surfaces of the limb elements, along with the presence of numerous entheses (ossified
ligaments) on the vertebral neural spines, provide strong evidence that one of these specimens represenrs a very old individual. This
study provides an opportunity for comparison with other specimens of C. lentus spanning a range of ontogenetic stages.
Introduction The medium-sized sauropod Camdrdsaurus is widely distributed throughout the Upper Jurassic Morrison Formation in North America. Four species are generally assigned to the genus: C. grandis, C. lentus, C. lewisi, and C. supremus. However, although hundreds of Camarasaurus bones have been found, species level identification of individual elements is still problematic due to several factors: (1) a significant degree of ontogenetic change between juvenile and adult vertebral elements, (2) a poor understanding of sexually dimorphic characters, (3) a wide degree of individual morphologic variation, and 14) a lack of accurate stratigraphic correla-
tion of the widely distributed Camarasaunzs localities. Mclntosh (1990) used the presence of elevated neural arch pedicles in anterior dorsal vertebrae to distingui sh C. grandls from all other species, and characterized C. lewisi by the bifurcate neural spines
found in the posterior dorsal vertebrae (Mclntosh et al. 1996b). Mclntosh (1,990\ stated that onlv the larger size of C. supremzs distinguishes it from C. lentus, while noting that C. supremus is known only from very large individuals. Unfortunatell', the holotypes of C. lentus and C. grandis are juvenile specimens, making comparisons with adult specimens problematic. In 1992, the field crew of the 'Wyoming Dinosaur Center (\fDC) in Thermopolis,'Wyoming found two large skeletons of Camarasaurus on the V/arm Springs Ranch, approximately 7 km southeast of the town of Thermopolis in Hot Springs County, 'Wyoming (Fig. 6.1). This area has been the focus of extensive dinosaur excavations and research projects; about eight genera of dinosaurs are recognized from seven major quarries. The Morrison Formation in this area has been well documented (Bjoraker and Naus 1996; Turner and Peterson 7999; Carson 2000). Unfortunateln no recognized regional isochronous marker beds exist, and stratigraphic correlation with other dinosaur localities is difficult. Although differences of opinion do exist, the stratigraphic placement by Turner and Peterson (1999) is likely the most accurate, They place the CamarasaurLts bones just below the TithonianKimmeridgian boundary. The majority of Camaraslurus bones were excavated from the Besides Sauropod (BS) Quarry (Fig. 6.1), adjacent to a previously excavated Apatosaurus found in the S (Sauropod) Quarry. No clear boundary separates these two quarries, and some Cdmarasaurus cranial elements and caudals were collected in the adjacent S Quarry. The two Camarasaurzzs skeletons are designated WDC A and WDC B. Most bones of WDC A tend to be distributed in the southwest region of the BS Quarry. Some caudals and a few limbs New Adult Specimens of Camarasdurus lentus Highlight Ontogenetic Variation
.
155
N
t
'\
SW Bs-Quarry
\s,
NE BS-Quarry
59
oBS-1
BS-259
6&
nl,^''n
ll cJ
ll
E
i'vJ
a\-'G
oo
BS-265 .271
198
2d,
//
,Fg
V. t
s-261 BS
.ffi
rp
$R5 /^ 6
'4'f^ ^a'
f
---------.1aws
I ^- o" c:^-T Z--r'
hn
Fig. 6.1. Portions of tbe Besides Sauropods (BS) and Sauropod (S) Quarr ies in Th ermop olis, rYyotning. Most elements of the small
e
r
Catnar asaurus Ientus
(\YDC A) ore concentrated in the south*-est (SW) of the BS Quarry, but some bones of the larger Camarasaurus (\YDC B) and Apatosaurus (NSMT 20375) are also ouerlapped in the area.
of the ApatosdLrus, along with some materials of \WDC B, are also known in the \X/DC A area. No'WDC A element has been recognized from the northeast Y+ of the BS Quarr,v, only elements of \fDC B. The quarries occur approximately r/zto,!/s from the base of the formation in a 15 m-thick sequence that C.Frs-on (2000) interprets as overbank, meandering stream, and lacustrine deposits, including caliche formed by seasonal drying and well-developed paleosols. This interpretation explains why the skeletons are weli preserved, but mostly disarticulated, as well as being overlapped in their distribution. No evidence of scavenging in the sauropods has been found.
The Camarasaurus skeletons are assigned to C. lentus based on the low, massive neural arches found throughout the anterior to middle dorsal vertebrae and in the absence of T-shaped neural spines in the anterior caudals. Despite the abundance of known Camarasaurers skeletons, these tu'o animals are significant for a number of reasons: (1) nfDC A preserves a fairly complete skeleton, including mosr portions of the presacral vertebrae; (2) the cervical/dorsal transition, which is rarely found in other individuals, is preserved in both specimens; (3) these adult examples of C. lentus provide useful comparisons with adult C. supremus; (4) \fDC A displays characteristics suggesting advanced age that are useful in studying ontogenetic variation; and (5) possible sexually dimorphic characters are found that may extend to other species of Camardsdurus as well.
Institutional abbreuiations. AMNH-American Museum of 156
.
Takehito Ikejiri, Virginia Tidrvell, and David L. Trexler
Natural History, New York; BHI-Black Hills Institute, Hill Cit.r'', South Dakota; BYU-Earth Science Museum, Brigham Young University, Provo, Utah; CM-Carnegie Nluseum of Natural History, Pittsburgh, Pennsylvania; DINO-Dinosaur National Monument, Jensen, Utah; GMNH-Gunma Museum of Natural History, Gunma, Japan; NSM-PV-National Science Museum, Tokyo, Japan; OMNH-Sam Noble Okiahoma Museum of Natural History, Norman, Oklahoma; SMA-sauriermuseum Aathal, Aathal, Switzerland; USNM-National Museum of Natural Historv (formerly United States National Museum), Washington, D.C.; UUVP-University of Utah Natural History, Salt Lake Cit,v, Utah; \7DC Bs-Wyoming Dinosaur Center, Thermopolis, Sfyoming; and YPM-Yale Peabody Museum, Yale Universitn Ner'v Haven, Connecticut.
Description Skull. The skull of Camarasaurrzs has been fullv described by Madsen et al. (1995), along with species level comparisons. They state that the large amount of variation found in Camarasaurus skulls is not taxonomically significant at the species level' Therefore, we will not describe each cranial element of the WDC specimens here, but instead will concentrate on those displaying a significant degree of variation. Those elements currently stored in the National Science Museum include both premaxillae, maxillae, dentaries, postorbital, articular( ?), ;ugal, right quadratojugal, and fragments. A fairly complete braincase (WDC BS-388)' two partial nasals (\fDC BS-15, 407), two right quadrates ('$fDC BS-405, 435), a frontal (no BS no.), and a partial right maxillary (WDC BS189) are at the'Wyoming Dinosaur Center. One right maxillary and one right quadrate are smaller, and they have been assigned to the smaller Camarasauras WDC A. On the braincase, the diameter of the occipital condyle is too large to articulate with the small Camarasdurus atlas recovered from the BS Quarrn suggesting the braincase belongs to \X/DC B. However, separating the rest of the craniai remains based on size is very difficult. The restored snout of Camarasaurus lentus is short anteroposteriorly, with a taller anterior margin than in other specimens. The \WDC jaws contain the fewest number of aveolae found to date in Camarasdurus, eight in the maxillae, ten in the right dentary, and eleven in the left. This is in sharp contrast with the juvenile dentary,
CM 11338 (C. lentus), which has 13. Table 6.1 illustrates the degree of variation in tooth number found in Camarasaurus, suggesting that tooth counts are not reliable for species level identification. 'WDC
A (\7DC BS-258) (Fig. Atlas.The well-preserved atlas of neuropophysis' Ata right and intercentrum has a complete 6.2 ) rugose attachment large are very but there missing, lantal ribs are Similar rugosities the centrum' of ventral surface surfaces on the such as OMNH individuals, in large and old found are commonly (Camarascturus not in a but sp.), 1174 iuvenile, CM 11338 (C. New Adult Specimens of Camarasaurus lentus Highlight Ontogenetic Variation
.
157
TABLE 6.1. Number of Aveolae in Camarasaurus Specimen
Species
\(/DC
C. lentus
cM
C. lentus
11338
USNM 13786 UUVP 3609 UUVP 3610
uuyP
11626
UUVP 1859 UUVP 1860
DINO 975 DINO 28 GMNH-PV YPM 1905
AMNH OMNH
5761 1169
BHI 6200 SMA
X:
101
OOO2
C. lentus C. lentus C. lenttts C. lentus C. lentus C. lentus C. lentus C. lentus
Maxillary 8 or 9? (L); 8
*"8-9
Dentafv (R)
11 (L); 12 (R) ,,,,
13
10
74
X
13
X
7I orl2
X
13
9
X X
9
X *10
,,
13
X
C. grandis
**10
C. grandis
X X
11
9
X
10
10 or 11
10
13
C. supremus C. supremus
c-tp. c.tp.
""14 " 1.2
missing element or data unar.ailable.
'r Data are from Nfadsen and Mclntosh (1995).
*'" Data are from Mclntosh et al. (1997).
lentus), or subadulrs, such as USNM 17863 (C.lentus). Both prezygapophyses are exrremely thin, and both ends of the dorso-medial margins are almost joined above the neural canal. Two pairs of unusual tiny processes are preserved on the WDC atlas (Fig. 6.2). One is on the anterior edge of the mid-process of the neuropophysis,
which is about 10 mm in the diameter (see ,,pr,' in Fig. 6.28, D), the end of the knob is directed almost dorsally. The other small, hooklike processes are on the lateral surface of the root of the neuropophyses (see "k" in Fig. 6.2A, C). This hooklike process is never found in juvenile or subadult C. lentus (e.g., CM11380, USNM 73786, YPM 1905), suggesring that this character is ontogenetic. The highly pneumatized intercentrum has a deep concavity on the artachment surface of the occipital condyle; the intercentrum has a very thick ventral margin. The posterior surface of the intercentrum is relatively flat and rugose. The overall height of the atlas is short, differing from a few atlantes from the Cleveland Lloyd Quarry, cenrral Utah (UUVP 2983 and UUVP 10070), which have dorsoventrally elongate vertebrae (Table 6.2). Axis. Two axes from rhe BS and S quarries are massive and have transversely wide centra. The two axes show morphological
158.
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
11
\/' \,i
nr Y'
ft
Fig. 6.2. Atlas of Canarasaurus lentus /WDC Ar \{DC BS-258) in (A) anterior, (B) posterior, (C) lateral, and (D) uentral uiews. Scale bar: l0 cm. Abhrerialions for bones: k = knob; nc = neural canal; nP = neuroqoPhYsis; Pr = process;
rf = rib facet.
TABLE 6.2. Comparative Measurements of Atlas in Camarasaurus
\TDC-A
(nrDC BS-258) OMNH 1174 UWP 2983 GMNH-PV 101 (C. supremtts\ (C. lentus) (C. grandis) (C. lentus)
Dimension
58
50
70
82
64
59
83
92
4I
84
70
98
77
92
86
104
JL
93
90
54
84
89
4.)
A. Total lateral centrum length
72
B. Total ventral centrum length C. Centrum anterior breadth D. Centrum anterior height E. Centrum posterior breadth F. Centrum posterior height rvithout neural canal G. Overall maximum height
\74
H. Breadth between neuropophyses
70
I. Centrum posterior height rvith neural canal
84
All
measurements
? ? 84
1.66
136
131
166
89
85
in mm.
New Adult Specimens of Camarasaurus lentus Highlight Ontogenetic Variation
.
159
TABLE 6.3. Comparative Measurements of Axes in Camarasaurus
Dimension
A. Total centrum length B. Centrum length without odontoid C. Cenrrurn anrerior heiphr
D. Centrun-r anterior
STDC-A (wDC BS-198) (C. Ientus)
\X/DC.B (v/DC BS-225) C. lentus)
UUVP 634I C. lentus)
162
210
190
193
r39
142
182
128
I4 )
95
97 114
90
83
87
76
118
92
111
92
breadth
UUVP 1555 (C. lentus)
YPM 1905 C,
E. Centrum posterior height
108
85
87
85
76
F. Centrum posterior
107
95
99
91
77
breadth
G. Overall maximum height
264
220
158
227
Least mid-centrum
52
77
-).-)
rvidth L Neural spine r,vidth
a.l
30
117
135
83
?
90
J. Breadth between dia-
138
138
151
130e
138
H.
pophyses e
-
all
estimated measurements
Fig. 6.3. Arls o/ Camarasaurus lentus /V/DC A: WDC BS-198) in (A) lateral, (B) dorsal, and (C) uentral uictt's; and IWDC B: WDC BS-225) in (D) lateral, (L',) dorsal, and (F) uentrdl uietus. Scttle bar: 10 cm.
differences (Table 6.3). For example, the pleurocoels of \X/DC A (WDC BS-198) (Fig. 6.3A-C) are much larger and more elongate than in'SfDC B (\7DC BS-225) (Fig. 6.3D-F). These pleurocoels are more complex in \fDC A than WDC B, being subdivided into small compartments by many tiny laminae. Many shallow fossae occupy the entire neural arch surface. The axis of \JfDC B is rela-
160
.
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
tively simple without any of the fossae and extra laminae, despite '$7DC A is narrower its more massive size. The neural spine of transversely and contrasts with the expanded spine in\fDC B. A long and well-developed ridge is placed medially on the ventral side of the centrum, occupying the posterior 2/z of the centrum, and the middle of the centrum is strongly constricted transversely. In contrast, WDC B exhibits a very flat, wide ventral surface and a shallow concavity on the dorsal neural spine, similar to that observed in YPM 1905 (C. grandis). Although the axis assigned to WDC A morphologically differs from'SfDC B, both axes resemble elements
from other Camarasaur,zs specimens. The narrow ventral edge of \flDC A is similar to C. lentus (DINO 288). whereas the numerous pleurocoels on the neural arch resemble UUVP 1'0896 (C. lentus?). shares a wide ventral margin with UUVP 10896 (C.
\7DC B lentus?).
Other ceruicals. Camarasaurus cervicals have been described by Osborn and Mook (L921), Gilmore (1925), and Mclntosh et al' (1,996a, b), and the adult C. lentus vertebrae from Thermopolis closely resemble these. Therefore, we only note variations in morphology between the two'SfDC specimens, and then compare the 'WDC A (\(/DC results with other species. The anterior cervicals of 85-206, 255) have large, complex pleurocoels and delicate spinoprezygapophyseal laminae, whereas those of \fDC B (\(/DC BS184, 185) have smaller, simpler pieurocoels and lack spinoprezygapophyseal laminae (Fig. 6.4). Of the five middie cervicals found (CV 5-8), four are assigned to WDC A (\fDC 85-268, 188, 255, 210) based on their large pieurocoels, accessory laminae found posteriorly on the lateroventral surface of the centrum, the large and shallow concavity on the ventral surface between the parapophyses, and traces of ossified ligaments (entheses) in the groove separating the metapophyses. Similar ossification is also observed in other mature Camdrasaurus (BYU 9047 and one of the individuals in AMNH 5751). Such entheses have not been found in juvenile or subadulr individuals. A total of four Camdrasaurzs posterior cervicals were recovered, and based on the size of the vertebrae and pleurocoel morphology, \fDC A includes CV 9-12 (XfDC BS-208, 555, 382, 193). In both specimens the entire neural arch of CV 11 and12 is strongly inclined anteriorly (about 60'from horizontal in lateral view); moreover, Figure 6.5 shows that both the diapophyses are extremely recurved ventrally (Fig. 6.58). The depression between the metapophyses of CV 11 and 12 is very narrow.'We suggest the cervical vertebrae are not useful to identify Camarasaurus species because of the relatively large morphological variation and lack of diagnostic characters. Dorsals. All of the anterior dorsals have very large centra (Fig. 6.6) relative to the overall size of each vertebrae, even proportionally larger than those in C. suprem lzs. Few Camarasaurlls specimens preserve a cervical/dorsal transition, but this region is well preserved in both \VDC specimens. The proximal dorsal (\7DC A: \fDC BS'$7DC B: \7DC BS-159.27L,346,347) neural 206,255,268, 188;
New Adult Specimens of Camarasdurus lentus Highlight Ontogenetic Variation
.
161
SPRL
Fig. 6.4. Anterior ceruicals of Camarasaurus lentus. /A) 1VlDC Ar V/DC 85-268) and (B) (WDC B: WDC BS-270). WDC A s h ow ing sp inopr e zytgdp op h1's e al lamina (SPRL), but lacking this lamina in \VDC B. Not to scale.
arches lack the strong anrerior inclination (- ZO") that is found in the posterior cervicals, and the diapophyses are directed horizontally, rather than laterovenrrally. The intrametapophyseal depression is also much wider than in the cervicals. several fact'rs were used to assign the ten dorsals to V/DC A, including the four middorsals (WDC B5-261,259,260,252): slightly more slender, anterior mid-dorsal centra; narrow posterior centrodiapophyseal laminae, characterized by a relatively short neural arch; and long, well-developed cenrroposrzygapophyseal laminae bracketing the neural canal (Fig. 6.6A). Conversely', the more massive vertebrae of \fDC B (Fig. 6.68) show a relativell' recurved ventral margin of the posterior centrodiapophyseal laminae dorsomedially, which makes the whole posterior centrodiapophyseal laminae broader than in
162
.
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
Fig. 6.5. Posterior ceruical of Camarasaurus lentus /WDC Ar BS 193) in (A) Iateral and (B) posterior uiews. Scale bar: 70 cm. Abbreuiations: tP = transuerse process,
\fDC A. The centropostzygapophyseal
laminae are also much
shorter, terminating above the neural canal. These
two different
dorsals may reflect sexual dimorphism because most dorsals of adult CamarAsdurus can be separated into either type. Three posterior dorsals (\fDC BS-184, 185,270) share a number of features in common and are assigned to'WDC A, including: entheses on the lateral surface of the neural spine, and well-developed rugosities on the entire anterior and posterior surface of the spines. Similar features are also found on dorsals in AMNH 5761' (C. supremus) and BYU 9047 (C. lewisi), and may indicate advanced age' The one posterior dorsal assigned to \X/DC B (\flDC BS-328) lacks these characteristics. In both specimens the degree of opisthocoely is very weak and the last dorsal approaches amphiplatyan. There is no hyposphene New Adult Specimens ol Camarasdurus lentus Highlight Ontogenetic Variation
.
163
pedl
Fig. 6.6. Anterior dorsals of Camarasaurus lentus /Al (WDC A: WDC BS-271) in anterior, lateral, and posterior uiett,s and (B)(WDC B: WDC BS-191) in anterior, Iataral. and posterior uiews. Scale bar: 10 cm. Note the narrou.t cpol and long pcdl in this
indiuidual
(see
posterior
uieu.,
).
Abbrettiations for bone: cpol = centro post zygo pop hyseal
Ia
m i nd :
cdl = p ostcentro diap ophy seal lamina.
p
on this element, and the transverse processes are directed dorsolaterally, rather than laterally as in the other posrerior dorsals. Sacral. One sacrum (\fDC BS-14) from the BS euarry is fairly complete; only the last two centra and the posterior ends of the ilia are missing. All the preserved centra are fuied, including sacrals s1 and 52. In juveniles and subadulrs rhese two centra often remain separate, whereas in marure individuals they tend to fuse. McIn_ tosh et al. (1996a) and Tidwell et al. (this volume) discuss variarion in the pattern of ossification between the centra and neural sDines in Camarasaurus. In WDC A, the neural spines of 52 and S.3 are completely fused, whereas only the lowermost portion of the spines of 53 and 54 are fused. The distal ends of neural spines 51 n"d SZ as well as 54 and 55 remain unfused. Sacrai vertebrae are less diagnostic in Camarasdurus than dorsals; however, Camarasaurus sacra seem to display significant ontogenetic and individual variation. Ontogenetically, there are probable indications of mature individuals, not only in the high degree of 164
.
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
Fig. 6.7. Sacral uertebrae r.tf Camarasaurus lentus /WDC A: \Y/DC BS-14) in (A) dorsal dnd (B) left lateral uieu,s. Arrows shou ossified ligaments (see A) and intercostal plates on lateral surface of the neural spines. Scale bar: 70 ctn.
the fusion but also in the rugose surfaces on rhe dorsal margin of the ilia, the top of the neural spine apices, and the dorsal surface of the ends of the sacral ribs. Jensen (1988) and Mclntosh et al. (1995b) mention the "strap-like ossified ligaments" conne*ing the sacral neural spines and sacral ribs in C.lewisi (BYU 9047). Similar entheses are also found in N7DC A (Fig.6.7). This sacrum has welldeveloped entheses attached to the lateral edge of one neural spine and the middle of a sacral rib, and, interestingly, one complete enthesis of 10 mm in diameter is preserved that fully connecrs the left side of the neural spine of 54 to 55 at the mid-shaft of the sacral rib. New Adult Specimens of Camarasdurus lentus Highlight Ontogenetic Variation
.
165
C
IlS. 6.8. Anterior caudals of (A) Camarasaurus lentus (\VDC A: BS 1r2). (B) (\\tDC B: BS 291), (C) C. grandis (YPM 1905), and (D) C. sr.rpremus /AMNH 5761) in posterior uiews. Scale bar: 70 on. C. lentus hds a gradudlly exp,uttled rteural spine. C. grandis ,lr,/ C. supremus haue a strong : .'trt,i(tion near the top of spines.
Mclntosh et al. (1996b) stated that the ligaments extend the condition inferred for the middle and posterior dorsals. In fact, in'WDC A, a few posterior dorsals and the first two caudals also show evtdence of entheses. Caudals. More than fifty caudal vertebrae were recovered at the BS Quarry, of which 18 anterior caudals can be separated into two morphs based on the size of the chevron facets. A distinguishing characteristic in the anterior caudals (\fDC BS-192, 7L3,263, 1,44,70,1,42,141, two uncatalogued) of \7DC B is the very iarge chevron facets. Specificallg the facet in the first several caudals occupies from half to two-thirds the width of the centrum; in contrast, the facet in N7DC A (\fDC BS-332, S-152, six uncatalogued) occupies about one-fourth of the centrum. Mclntosh et al. (1996a) discussed two different types of neural spine apices in anterior caudals of C. grandis.' transversely narrow (e.g., YPM 1905) and transversely wide (e.g., YPM 1904). They suggest the differences are attributed to sexual dimorphism. In contrast, the neural spine of C. lentus (Fig. 6.8A, B) gradually expands 166
.
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
Fig. 6.9. Cheurons
of
Camarasaurus lentus: (A) a proximal head oi cheuron fttsed to the anterior caudals (WDC BS263) and (B) flrst cheuron ('V/DC BS-224). Scale bar:10 cm.
and is easily distinguishable from the T-shaped neural spine of C. grandis and C. supremus.In addition, the spine of C. lentus is not as constricted as in C. grandis and C. supremus (Fig. 6.8C, D). Furthermore, the degree of expansion of the neural spine apex is not as great in C. lentus (Fig. 6.8A, B) as it is in C. sLtpremus and C. grandls. Therefore, we suggest the T-shaped neural spine is useful to distinguish massive-type (male?) C. supremus and C. grandis from C. lentus. In addition, these differences are more diagnostic in adults than juveniles. The size of the chevron facet seems to be consistenr in each animal, and in this case is probably due to ontogeny be'WDC cause two fused caudals ('WDC 85-263, nos. 3 and 4l) of A show a chevron head fused onto the centrum (Fig. 6.9). The remaining caudals cannot be assigned with certainty to either individual because they are too similar in size and shape. Numerous chevrons were widely scattered throughout the BS Quarry and it is New Adult Specimens ol Camarasaunrs lenttrs Highlight Ontogenetic Variation
.
167
difficult to assign them to specific positions or individuals. Horvever, one chevron (\7DC BS-224) (Fig.6.98) is very broad (123 mm) and rather short (236 mm), which is less than half the length of any other chevron from the quarry. The specimen is probably a first chevron. The distal rami are fused and anteroposteriorly compressed. A similar, distinctive first chevron is also reported for Camarasaurus by Maltese (2002); however, that specimen has unfused, divided distal ends. This difference is potentially due to sexual dimorphism, but further study is needed to confirm this hypothesis.
Pectoral girdle. One of the two sternal plates, \7DC BS-104, shows an expanded proximal portion similar to that found in other Camdrasaurzzs specimens, such as AMNH 261.,262, and 5761. (fig-
ured in Osborn and Mook 1921) and GMNH PV-101. It has a thick, rugose, anterior edge; a thin, smooth, concave lateral margin; and a rugose, thicker, convex medial margin where it would articulate to the other sternal plate (Fig. 6.10C). Cdmarasaurzs scapulae display a remarkable degree of variation, particularly in the shape of the distal end. Pagnac (1998)documents two distinct shapes of the distal end of the blade: (1) ventrally expanded and widely flared, commonly found in C. grandis and occasionally in C. lentus; and (2) ventrally flat or unexpanded, found in most scapulae of C. supremus and some juvenile C. lentus. Pagnac (1998) also found differences in the dorsal margin of the scapular (acromion) plate transition to the scapular blade: (1) perpendicular, (2) recun'ed, or (3) oblique angle. He suggests these differences are ontogenetic or due to sexual dimorphism. However, the very large scapuiacoracoids (nfDC BS-104; IfDC BS-179)from Thermopolis suggest that ontogeny may not be important. These scapulae have an erpanded distal end and a scapular plate-blade transition that is almost 90'(Fig.6.10A). The coracoids are fully fused to the scapulae and appear to be larger in proportion to the scapular plates of other Camarasaurus specimens. In the juvenile CM 11338, the coracoid is proportionately much smaller relative to the scapular plate, and thus may change ontogenetically. We believe that additional adult specimens are needed before committing ourselves to the large coracoid being a characteristic unique to the species.
Forelimbs. Although we consider the two scapulacoracoids to belong to one individual, we are not yet sure if the forelimb comes from the same animal because it was found elsewhere in the quarry. Based on differences and similarities of loinr surface rugosities, we are fairly confident that the radius and ulna are from rhe same animal, but not the humerus. This bone shows a higher degree of muscle scar development and more prominent rugosity development than the lower limb elements. The hyper-development of rugosities on the proximal and distal ends of the right humerus (\fDC BS156) (Fig. 6.10B) are sin-rilar to those described for the very large C. grandis specimen, GNMH PV-101 (Mclntosh et al. 7996a). The proximal breadth, least breadth, and distal breadth:length ratio for
168.
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
D
E
C
&
K ffi
Fig. 6.10. Appendicular skeleton
o/Camarasaurus lentus: fA) /e/r s cap ulct cora co id, late r d I u i e u /WDC A: \YDC BS-171)); (B) Ieft humerus, anterior uietu (VIDC BS155): (C) right sternal plate, external uiew (\Y/DC BS-108); (D) left radius (WDC BS-31.t); (E) ulna (\YDC BS-313/; (F) risht fetnur (WDC BS-13); (G) right tibid (WDC BS-217), medial uiew;
and (H) right fibula fWDC BS199), anterior ileL,. Not to scale.
the WDC humerus (Table 6.5) indicate that it is more gracile rhan the humerus of the type of C. lentus (YPM 1910). It is more robust than that of a large C. grandis (GNMH 101), but in contrasr, the proximal and distal breadth:length ratios closely resemble that of
tlre juvenile type of C. grandis (YPM 1901). Unfortunateln comparison with the very large C. supremus specimens is not possible due to the lack of forelimb material in those specimens. The right radius (\7DC BS-314) (Fig. 6.10D) has a ratio of least circumference:length 0.38 that is the same as in C. lewisi, and close to that in the holotype of C. grandis (YPM 1905) (0.37). The right ulna (\fDC BS-313) (Fig. 6.10E) has a least circumference:length ratio,
0.40, that is slightly more than tn C. lewisi, Cdmdrasourus sp. (AMNH 823), and the type of C. grandis (0.38). Peluic girdle. There is nothing about the peivis material that alNerv Adult Specimens o{ Camarasaurus lentus Highlight Ontogenetic Variation
.
169
lows it to be distinguished from other Camarasaurezs species. The material includes a large left pubis (N7DC BS-14) that resembles that of C. supremus. Two well-preserved ischia (\fDC BS-11; \fDC BS-9) have shafts that are posteriorly curved in the exaggerated manner typically found in Camarasaurus. Hindlimb. As with the pelvic material, there is nothing about the hindlimb elements that distinguishes them from other Camarasaurus specimens. Four femora (\7DC BS-207, WDC BS-13; uncatalogued, specimen at the NSM), have been recovered (Fig. 6.10F). The right tibia ('WDC BS-21.7) has a poorly developed cnemial crest (Fig. 6.10G) characteristic of Camardscturus, and in contrast with the larger cnemial crest found on Apatosauras (see Wilhite, this volume). The right fibula ('$(iDC BS-199) has the posterior deflection found in the proximal one-third (Fig. 6.10H) seen in several other specimens of Camarasaurus (CM 1 1 3 3 8, USNM 1.7 863 , GNMH 101, YPM 1910; also see \7ilhite, this volume). The development of rugosities on the proximal end is similar to that found on the tibia, suggesting that the two bones belong to the same animal.
Discussion
Distribution. Camarasaurus skeletons have been found in Upper Jurassic Morrison Formation sediments across a wide geographic area in western North America (Fig. 6.11). However, as discussed in Ikejiri (2002), the species are not evenly distributed, with some species overlapping in their geographic ranges. Stratrgraphically, C. supremus appears to be restricted to the top of the Morrison, whereas the other three species are found overlapping at lower levels of the Morrison. C. letuisi is only known from a single specimen recovered from the Dominguez-Jones Quarry of western Coiorado. C. supremus is found in south-central Colorado. In contrast, no C. lentus skeletons have been identified from these regions, suggesting a geographic separation between C. supremus and C. lentus. C. lentus remains have been identified from a wide area extending from northern Wyoming to eastern Utah. This range overlaps that of C. grandis, which has been identified from central'$7yoming, central Colorado, and New Mexico. Although several Camarasauras skeletons have been recovered from South
Dakota, none have been identified as to specles. Ontogeny. C. lentus is known from the juvenile holotype specimen (YPM 1910), as well as a nearly complete juvenile specimen (CM 11338), subadult (USNM 17863), and adult (CM 11393) individuals from the Carnegie Quarry in the Dinosaur National Monument. These specimens either have not been fully prepared or have not described, which has long hampered species-level taxonomy and limited our understanding of ontogenetic variation within the genus. Pending description of CM 11393 and USNM 17863, the two Thermopolis specimens provide the only opportunity for comparison of fully grown C. lentus with juveniles that are 30% to 1.70
.
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
i 1
I
i I
t--
I
MTr
---:.------'-"), 1
I xlx xl x I
C,
I
Ientus
i
Area
I I I
L_C.
v.---'K_
gEndis
C. supremus
Countt;2 = Beside Sduropr,td Quarrf in Thermopolis; 3 = Reed's Quarry 13, East Como
\---\
Bluff;1=
Reed's Quarry 1 and 3, 'V/est Como Bluff; .\ Dinosaur =
\
TX
National Monument in Verndl; 6 = Clcucland Llovd Quarrt in Emerl' County; 7 = DominguezJones Quarrf in Mesa County; B = Cope's Nipple and Lindsey's 1977 Quarry in Garden Park;9 = San Ysidro Camara> euru> Quaruy in Santloual Countt,' 1.0 = Stouall Pits in Kenton; and 11 = Grand Valley in Mesa County.
-l;-;;Js.* 40"/o aduh size (YPM 1910 and
Fig. 6.1 1. Ocarrences of Camarasaurus species in the Morrison Formation (Modifi ed from Turner and Peterson 7999; Ikeiiri 2002). Symbols = identified species. X = Camarasaurus sP. Abbreuiations for quarries: 1 = Hou,e Quarry in Big Horn
CM 11338). Our conclusions rein Table 6.4 and elaborated
garding ontogeny are summarized below.
The cranial skeleton shows few ontogenetic changes besides (CM 11338, USNM 17863) are already tightly fused (Madsen et al. 1995,11). The braincase is also fused and there is no significant difference from the suture pattern of the WDC specimen. The juvenile CM 11338 does show a taller anterior margin of the premaxillae than the subadult USNM 77863. However, the'WDC specimen also shows a size. The frontals and parietals of the juveniles
New Adult Specimens of Camarasattrus lentus Highlight Ontogenetic Variation
.
171
TABLE 6.4. List of Ontogenetic Characteristics and Four Representative Growth Stages in Camarasaurus lentus and Other Species in the Genus except Embrvo Stage Stage General
age.
Representative
I
Srrgc
Subadult
.jur enile
speci-
YP\,I
CM11338,
mens in Cdmarasau- 1910 rus lenttts
USNN.I 17863, 1
1901, OMNH specimens"" Pleurocoel complex- Sirnple, no iossae (in ity in cervicals all specirnens)
of
Other species tndrdsdLt/us
(rrqe
2
Ca- YPM baby
CNI
1393
Stro. 4
l
Adult \(/DC-B, Clt{
8492,
Verv old individurl \(/DC-A
71,069*
YPN1 190,{,
ONINH
190.5,
1173
Simple, no fossae all)
AMNH 5760, 5767*"*, GNINH
(in
101
and/or
Shallor.v rooms fossae (in all)
ANINH 5761*"*. BYU 9047 Nlanv fossae and
tinl' laminae
(ir.r
all)
11338)
Atlas knob and hook- Absent (CM like process ("see
Absent
(YP\I 1905,
Srnall IUUVP
usN\,r 17863, ON,INH GNINH-PV
text)
2983,
101)
Developed iBYU 90,+7,
\ilDC-A)
r173)
Over-grorvth bone on cervical neural
Absent (in
all)
Absent (in
all)
Absent (GMNH-P\/ 101), present (NfDC-B)
Absent (in
all)
Absent (in
all)
Absent (in
all)
Present (in all)
Absent (in
all)
Absent (in
all)
Absent (in
all)
Prcscnt (in all)
Present (in all)
spine
Ossified ligament on lateral neural spine
of posterior dorsals Over-gror.vth bone on cleft of bifurcated dorsal neural spines Tin.v laminae on
sal neural
arch
dor- No (YPl,l
Ossified ligamer.rts
in
sacrum
1901, CNI 11338, ON{NH spec-
No (USNN{ 17863, CM 11393, YPIvI
lmens)
1904,1905) No (USNM 17863, YPM 1904, 190s) Identical sutures (usN\,I 17863, CM
No (YPNI 1901, 1
Clvi
1338)
Neurocentral closure Opened (YPM in cen icals and dor- CM11338)
1901,
sa]s
1
closure in
rib
sacrum
Fused sacral
ribs;
closure Opened (CN'I 11338, caudals YPI,I 1910)
Neurocentral
closure
in mid-caudals ("rvith tall neural splnes
Cllosed (in
101)
all)
9047 }'es (\(rDt--A, BYU 9047) Closed (in all)
17863)
Fused
101,
(GNINH-PV 690)
AMNH
F'uscd {WDC-A,
BYU 90,+7)
s
Neurocentr:al
in anterior
No {GNINH'PV
\VDC-A, BYU
)
Fused (USNN.{
identical neurocentral closure
CNI 101)
8492, GX{NH-PV
1393, YPIVI 1904,
190.5
Neural arch and
No (\(DC-B,
Nearl,v closed (USNM Closed (in 17863, YPM 1904, 1905)
all)
Closed (in all)
(WDC-B, 101)
Visible (YPNI
1901, Closcd (USNNI 17863, OI,{NH YPM 1904, 1905)
Closed
CN'I 11338,
GNINH-PV
all)
Closed and no line (in all)
Ckrsed (\fDC-A,
BYU 9047)
specimens)
)
Rib closure in
ante-
Opened (in
rior caudals
Opened but visible tures (USNtrI
su-
17863,
suture
Closed (in all)
YPlvl 190.+, 1905) Limb articulated
sur-
faces
Pubic
foramen
Coracoid
772
.
foramen
Shallow rugosit,v only Shallorv pitted rugosity Relatrvely deeplv pitted Decply pirted on around external mar- on the nearlv entire ar- rugosity on thc entire the entire articular gin of articular sur- rrcular surface (in all) articular surface (in al1) surface (in all) face (in all) Opened
Opened
1905, 17863)
Closed (YPM 1910), Closed (YPM opcned (CNI 11338) USNI,{
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
Closed Closed (AMNH 5767)
Closed
5760,
Closed (S7DC-A)
Steoe
Coracoid-scapula closlrre Size of chevron
facets
I
(t:ue
Separate (YPM 1910)
Visual suture (USNNI
Small (in all)
Small (in all)
1
7863
Srr<'e
7
)
11
Completely fused (A\INH 5760, 5761)
Con-rpletely fused
N{odcrate (AI\,INH
Moderate (WDC-
.5760, .5761); Large
A); Large (BYU
(\VDC-B)
9047)
(\rDC-A)
* CM 8492 and 11069 are probabll'the same individual. ** OMNH baby CamarasaurLts a(e referred in Carpenter and N1clntosh (1990). :t** aMNH 5761 consists of ser,eral individuals (Nlclntosh 1998).
very tall, massive snout with a relativel,v short upper jaw (Fig. 5.12), suggesting this character may be due to individual variation rather than ontogeny in C. lentus. Finally, differences in the number of aveolae is due to individual variation because the juvenile 'WDC (CM 11338) has more aveolae than the large specimens. In the axial skeieton, small, hooklike processes are present on the lateral side at the base of the neuropophyses of the Thermopolis atlas (\7DC BS-258; Fig.6.2). These processes are not found in the smaller atlas of CM 11338; however, incipient hooks appear on the atlas of the subadult USNM 17863, suggesting they developed as the animal matured. Throughout the cervical vertebral series, pleurocoel size in the adult specimens appears to decrease in proportion to the total centrum length when compared u'ith that in the juvenile animals. Disproportionately large pleurocoels have been previously noted by Carpenter and Mclntosh (1994) in their review of baby Camarasaums material. In a related development, Britt and Naylor (1994) hypothesize that CamdrdsAurus neck length increases proportionally to total body length throughout ontogeny, a trend we confirmed for C. lentus. This occurs by continued elongation of the vertebrae throughout ontogeny. Neural spine morphology in the middle and posterior dorsal vertebrae differs greatly between the Thermopolis adults and the two juvenile animals. Juvenile dorsal neural spines tend to be almost square, showing little of the transverse expansion noted by Mclntosh et al. (1996a) rn the adult C. grandis and by us in the adult C. lentus. Juvenile spines are quite solidly built, smooth, and show few rugosities and only shallow, laterally directed fossae. In adult specimens, the spine is much wider transverseh', with well-developed entheses on the anterior and posterior surfaces. Portions of these entheses extend posteriorly from several spines in the Thermopolis specimens, indicating how the spines were joined in iife. Highly developed rugosities on the adult sacral vertebrae and the presence of entheses connecting the spines with sacral ribs also attest to increased calcification of soft tissue that is evident in these mature animals. Many anterior caudal vertebrae assigned to'SfDC A show enlarged chevron facets, whereas others assigned to WDC B do not. It is probable that the larger facets are accentuated by age, because such hyper-developed Nei.v Adult Specimens of Camarasaurus lentus Highlight Ontogenetic
Variation
.
173
Fig.6.12. Upper jaws of Camarasaurus lentus of (A) adult (NSMT uncatalogued = V|DC A?), (B) subadub |USNM 17863), and (C) jttuenile (CM 1'1338, front Gilmore 1925) in lateral uieus. Note the aduh (A) and juuenile /C) Camarasaurus show sborter max il lar ie s a nter op o st eri or ly and taller anterior margin ctf illary dorsou entrally th an the subadub (B). Abbreuiations for bones: m = maxillary; pm = premaxillary. G ray, cr:lor indicat es pr emax
missittg portion, Not to scale,
facets are not found on the juveniles (YPM 1910, CM 11338) or the subadult (USNM 17863).ln Camarasaurus, there is a typical order of neurocentral closure in the vertebral series (Table 6.4). A study of juvenile and subadult specimens indicates mid- and posterior caudals are fused first, followed by fusion of sacral vertebrae (Ikeiiri 2003). The appendicular skeleton of adult Camarasaurzs differs in several areas from that found in juveniles, beyond the expected development of rugose articular regions and muscle scars. These include: (1) proportions of the scapula and coracoid; (2) marked modification in the shape of the sternal plate; (3) modification of the fibular shaft; and (4) very slight changes in the overall robustness of the limbs. These points are elaborated upon below. Both coracoids in the S7DC specimens are unusually large in
174
.
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
c.a
Fig. 6.13. Sternal plates of Camarasaurus lentus (A) /CM 11338) and (B) (wDC wDC BS701) in external uiew. Scale bar: 70 cm. Abbreuiations for bones: a = dnterior end; c.a = coracoid attachment: p = posterior end; s.a = sternal attachment surface.
proportion to the scapular plate to which they are fused, compared with younger specimens. This difference is most clearly seen in comparisons with YPM 1910 and CM 11338, but it is also seen to a lesser degree in the subadult USNM 17863. The gradual increase in coracoid size in proportion to the scapular plate is probably ontogenetic in C. lentws. However, there are not many scapulocoracoids known for this species, and several scapulocoracoids of fully grown C. supremus (AMNH 5761') and Camarasattras sp. (CEU 1694, FMNH P6285,P6670) do not have large coracoids. This evidence indicates the variation in coracoid sizes may be due to individual variation. A clearer ontogenetic signai is seen in the sternal plate from juvenile to adult.In CM 11338 (Fig. 6.13A), the sternal plate is subcircular (283 mm in the greatest length and 200 mm in the greatest diameter transversely; see Gilmore 1925, 377). The adult sternal plate (\fDC BS-104) recovered in the BS Quarry (Figs. 6.138; 6.10C) is a long, narrow element (523 mm in the greatest length and 215 mm in the greatest diameter), more closely resembling the adult equivalent found in Diplodocus or Bra' chiosaurus. Such a marked difference in gross morphology between the adult and juvenile elements is unusual for sauropod dinosaurs. A small degree of ontogenetic variation is found in comparisons of the juvenile fibulae found in CM 11338, YPM 1910, and the subadult USNM 17863, with the adult fibula from the BS Quarry (\fDC BS-101). The three fibulae from the younger specimens shor,v a distinctive posterior deflection in the proximal one-third, and a strongly bowed shaft. The'$(DC fibula also displays a deflection (Fig. 6.14), although it is less pronounced than in the younger New Adult Specimens of Camarasaurus lentus Highlight Ontogenetic Variation
'
175
A
\
Fig. 6,14. Variation of a fibuldr ction lr Camarasaurus lentus,
defTe
(A) YPM 1910, (B) USNM 1786J, (C) WDC WDC BS-101, and (D) CM 11338 in anterior ttieus. Arrou,s indicate a position of posterior deflection ds in text. Not to scale.
TABLE 6.5. Ratio of humeri in Camarasaurus lentus
\rDC L
cM 11i93
(BS-1s6)
103
1
1
cM
USNM 17863
YPM 1910*
195
808
545
420
383
250
81
11338
GPB
450
438
LC
505
518
378
270
?
LBIL
0.17
0.16
0.18
0.77
0.1 9
CPB
:
greatest prorin'ral breadth;
L:
greatest lengrh;
l-B
:
least breadth; LC
:
least circumfercnce
animals, and the shaft is straighrer. Finally, a comparison of the robustness in limb eiements shows a significant degree of isometry as C.lentus grows from a juvenile to old age (Table 6.5). As noted by Wilhite (1999), Camardsdurlrs humeri rend to show only a slight change in the ratio of least breadth:total length. This ratio (0.19) is highest in the smallest (and presumably youngest) individual CM
11338. Least breadth:length progressively decreases in USNM 17853 (0.18), YPM 1910 (0.77), and \X/DC BS-156 (0.17), with the most gracile bones found in the largest adult C. lentus specimen studied, CM 11393 (0.16). Other limb elemenrs show only slight variation between the smallest juveniles and largest adults in the species. Similar findings have been reported for other sauropod taxa by Curtice et al. (7997) and Foster (1995). 176
.
Takehito Ikejiri, Virginia Tidwell, and David L. Trexler
Conclusions The two newly discovered \WDC Camarasaurzs provide important information about the adult C. lentws. The transition from the posterior cervicals to anterior dorsals is particularly significant for con-
sideration
of the taxonomy and morphological variation in
the
taxon. Vertebral morphology of these two specimens suggests there are few diagnostic characteristics suitabie to separate the adult C. lentus and C. supremus. The exception is the T-shaped neural spine found in anterior caudals in some C" supremus, and which is also seen in C. grandis. Detailed comparison of limb elements must await the recovery of foreiimb material for C. supremws andbetter hindlimb elements for C. lentus. Camarasaurzzs provides the largest sample size for an ontogenetic study (except for the embryo andlor hatching stages) in any sauropod taxon, and the series of specimens of C. lentus is of several growth stages. Hopefully, our study will illuminate future ontogenetic studies and aid in the understanding of character development in other sauropod taxa.
Acknowledgments.'We thank Burkhard Pohl (WDC) for the
permission to describe the two Cdmarasawrzs specimens. This prolect could have not been done without great help from the staff in
the'WDC, especially William'Wahl for access to the specimens, and 'Wilson, Ed excavation and preparation by Allen Nettles, David Cole, Frank Cole, Jessica Petty, Jessica Layman, Laura Vietti, and Teresa Palmer. Yukimitsu Tomida (NSM-VP) allowed Takehito Ikejiri to study the Camarasdurus cranial elements under his care. Special thanks to John S. Mclntosh (\Tesleyan Universitn Connecticut) and Ray lX/ilhite (Louisiana State University) for valuable discus'We also thank the curators and collection managers at the folsion. lowing institutions for access to specimens: American Museum of Natural Historn Black Hills Institute of Geological Research, Brigham Young University, Prehistoric Museum at the College of Central Eastern Utah, Carnegie Museum of Natural History, Denver Museum of Natural History, Gunma Museum of Nature History, University of Kansas Vertebrate Paleontology (Lawrence), New Mexico Museum of Natural History (Albuquerque), National Science Museum (Tokyo), Oklahoma Museum of Natural History, Sauriermuseum Aathal, National Museum
of Natural Historn
Utah Museum of Natural History, and Yale Peabody Museum. This study is a part of the rnaster's of science thesis of Takehito Ikejiri (detailed measurements of \X/DC A and WDC B may be requested), and Takehito Ikejiri thanks Richard J. Zakrzewski (Fort Hays State University, Kansas), for his encouragement and useful suggestions. Constructive comments on this manuscript by Kenneth Carpenter and John Foster are gratefully acknowledged. This project was partially supported by the Jurassic Foundation to Takehito Ikejiri and the \Testern Interior Paleontological Society to Vireinia Tidwell.
New Adult Specimens of Camarasaurus lentus Highlight Ontogenetic Yariation
.
177
References Cited
Bjoraker, C. A., and M. Naus. 1996. A summary of Morrison Formation (Jurassic: Kimmeridgian-Tithonian) geology and paleontology, with notice of a new dinosaur locality in the Bighorn Basin (USA). In C. E. Bowen, S. C. Kirkwood, and T. S. Miller, eds., Resources of the Big Horn Basin, 297-303. lTyoming Geological Association Guidebook series,
Britt,
no.47.
8., and
B. G. Naylor. 1,994. An embryonic Camarasaurus (Dinosauria, Sauropoda) from the Upper Jurassic Morrisor-r Formation (Dry Mesa Quarry, Colorado). In K. Carpenter, K. F. Hirsch, and J. R. Horner, eds., Dinctsaur Eggs and Babies, 256-264. Cambridge: CamB.
bridge University Press. Carpenter, K., and J. S. Mclntosh. 1994. Upper Jurassic sauropod babies
from the Morrison Formation. L.r K. Carpenter, K. F. Hirsch, and J. R. Horner, eds., Dinosaur Eggs and Babies, 265-278. Cambridge: Cambridge University Press.
Carson, C. J. 2000. The structural and stratigraphic framework of the 'lfarm Spring Ranch area, Hot Spring Countn lfyoming. Master's thesis, Oklahoma State University.. Curtice, B., J. Foster, and D. R. \filhite. 1997. A statisrical analysis of sauropod limb elements. Jottrnal of Vertebrate Paleontologl, 17(cy
4IA.
Allometric and taxonomic limb bone robustness variabiliry some sauropod dinosaurs. Journal of Vertebrate Paleontology
Foster, J. 1995.
in
15(3): 29A.
Gilmore,
C. 1925. A nearly
complete articulated skeleron
of
Cama-
rasdurus, a saurischian dinosaur from the Dinosaur National Monument. Memoirs of the Carnegie Museum 10: 347-384. Ikejiri, T. 2002. Biostratigraphic and geographic distribution of Catnarasaurus (Dinosauria, Sauropoda) from the Morrison Formation. Geological Society of Americd Abstracts with Programs 34(61: 425.
2003. Sequence of closure of neurocentral sutures in Camarasdurus (Sauropoda) and implications for phvlogeny in Reptilia. Journal of Vertebrate Paleontoktgy 23 (supp. 3): 65,{. Jensen, J. A. 1988. A fourth new sauropod dinosaur from the Upper Jurassic of the Colorado Plateau and sauropod bipedalism. Great Basin Naturalist 48(2): 121-14 5. Madsen, J. H., Jr., J. S. Mclntosh, and D. S. Berman. 1995. Skull and atlasaxis complex of the Upper Jurassic sauropod Camarasaurus Cope (Reptilia: Saurischia). Bulletin ctf the Cdrnegie Museum of Natural ntsrory Jt: l-ttJ. Maltese, 1,. ZOOZ. Discovery of a divided inirial chevron in Camarasaurus (Dinosauria, Sauropoda). Journal of Vertebrate Paleontology 22 (supp. 3): 83A.
Mclntosh, J. S. 1990. Species determination in sauropod dinosaurs. In K. Carpenter and P. J. Currie, eds., Dinosaur Systematics: Approaches and Perspectiues, 53-69. Cambridge: Cambridge University Press.
Mclntosh, J. S. 1998. New information about the Cope collection of sauropods from Garden Park, Colorado. Modern Geology 23: 481-506. Mclntosh, J.S., C.A. Miles, K. C. Cloward, and J. R. Parker. 1.996a. A new nearly complete skeleton of Camarasaurus. Bulletin of Gunma Museum of Natural History 1: 1-87. Mclntosh, J.S., \f.E. Miller, K. L. Stadtman, and D. D. Gillette. 1996b.
178 . Takehito Ikejiri, Virginia Tidweli, and David I-. Trexler
The osteology of Camarasaurus lewisi (Jensen 1988). Brigham Young (Jniuersity Geology Studies 4l: 73-115. Osborn. H. F.. and C. C. Ntook. 1921. CamardsdurLts, Arnphicoelias, and other sauropods of Cope. Memoirs of the American Museunt of Natural History 3: 247-387. Pagnac, D. C. 1998. Variation within the pectoral region and its implications concerning species level taxonom,v of the North American sauropod, Camarasaurus Cope. Master's thesis, South Dakota School of Mines and Technologl'.
Tidwell, V., K. L. Stadtman, and A. Shaw An unusual Canrdrasaurus
sacrum from the Dry Mesa Dinosaur Quarry. This volume. Turner, C. E., and F. Peterson. 1999. Biostratigraphy of dinosaurs in the 'Western Interior, USA. In Upper Jurassic Morrison Formation of the D. D. Gillette, ed., Vertebrate Paleontology in Utab, 77-11,4. Utah Geological Survey Miscellaneous Publication, no' 99-1. Salt Lake City: Utah Geological Survey. \fi1hite, R. L999. Ontogenetic variation in the appendicular skeleton of the genus Camardsaurus. Master's thesis, Brigham Young Universitl'. \filhite, R. Morphologic variation in the appendicular skeleton of sauropod dinosaurs. This volume.
New Adult Specimens of Camarasaurus lentus Highlight Ontogenetic Yariation
'
179
7. Age-Related Characteristics Found
in a Partial Pelvis of Camarasnurus VrncrNre Trowprr, KnNNnrn SreorMAN' AND ArrpN Ssew
Abstract Dry Mesa Quarry in western Colorado has produced a r.vide array of Late Jurassic sauropod specimens over the last thirty years. Although diplodocid specimens are predominate in this Brigham Young Universitv quarry, several elements of Camarasaurus have also been identified. One of these elemenrs, a complete sacrum, displays an unusual combination of six sacral vertebrae and lvidely flaring ilia. Although five sacral vertebrae are commonly found in this taxon, this specimen has incorporated a posterior dorsal into the sacrum. The vertebra is partially fused to the normal five sacrals and ilia. The neural spines of the first and second sacral vertebrae are completely fused, a feature previously found only in the holotype of C. lewisi. One additional feature is the wide flair of the ilia, which rivals that found in basal titanosaurs. In most Cdmdrdsaurus specimens, the preacetabular portion of the ilium is only moderately flared, to a degree intermediate between diplodocids and titanosaurs. This feature has been found in a few pelves belonging to C. grandis and C. lentus, frorn other quarries as well, raising the possibility of a sexual dimorphic, rather than taphonomic, cause. 180
Introduction
Dry Mesa Quarry in western Colorado has produced
elements
from at least thirteen individual sauropods, representing six different genera: Haplo canth oscturLts, Ap ato sattrus, D ip lodo cus, Sup er'Wilhite sdurus, Bracbiosaurus, and Camarasauras (Curtice and 1996). Previously, three pelves have been excavated and assigned to Supersaurus, Brdchiosaurus, and Camarasaurzs. Recentln a large, partial pelvis from this quarry was prepared at the Earth Science Museum of Brigham Young University (BYU 17465). It is identified as Camarasaaras because the low, very broad neural spines (all of a uniform height) preclude assignment to any diplodocid or to Hap' locdnthosaurzs, rvhereas the pubic peduncle of the ilium is too short for Brachiosaurzs. In lateral view, the ilia display a high degree of forward rotation in relationship to the fused sacral centra. This feature, most prominently displayed in C. lewisi, is also present to a lesser degree in C. lentus and C. grandis. Institutional abhreuiations. AMNH-American Museum of Natural History, New York; BYU-Brigham Young University, Provo, Utah; GMNH-Gunma Museum of Natural History, Gunma, Japan; and WDC-STyoming Dinosaur Center, Thermopolis, Wyoming.
Description An essentially complete sacrum (S1-S5) is found in BYU VP 77465, with a sixth vertebra (D12), plus the fused left and right ilia (Fig. 7.1). No other bones can be positively associated with the specimen at this tirne. The first centrum (D12) is large and opisthocoelous, and slightly compressed anteroposteriorly. but it retains a convex anterior articulation with the preceding vertebra. A small pleurocoeL is present dorsally on the left side of the centrum. As in other Camardsaurus specimens, the centra of dorsal 12 and sacral 1 appear to be strongly abutted, yet unfused. Generally, when the twelfth dorsal is added to the sacrum, the centrum does not fuse to the other sacrals, but remains free. Only in C. sp. AMNH 690 has complete central fusion occurred, yet the dorsal rib is not fused to the ilium. The neurai spines are mostly the same height, except for that of 55, which is taller and more massive than 54, as is the case in C. lewisi. The spine apices of D12 and S1 are heart-shaped, with a slight emargination visible both anteriorlv and dorsally. On S1-S5,
rugosities cover the apex and extend ventrally to form prominent pre- and postspinal rugosities that extend medially to the level of the prezygapophyses. Large, triangular metapophyseal spurs extend ventrally from the sides of each apex on the first five neural spines. The spines of S1-S3 are fully fused, whereas those of D1.2, 54, and 55 are completely separate (Fi1.7.2), The spine of 55 is very robust, closely resembling that in C. lewisi, and it is approximately the size of that of C1. The postzygapophyses of D1'2 and 54 are unfused to the succeeding prez.vgapophyses, whereas those joining 52 to 53 and 53 to 54 are completely fused.
Age-Related Characteristics Found in a Partial Pelvis of Camarasaurus
.
181
Fig.7.1. BYU 17155 CamarasaurLrs sacrum in dorsal
I = intercostdl plates. Note that all ribs remain in contact with uieu. il i u
m.
d esp
ite
p
red
(etdhular flair.
Scale bar: 10 cm.
D12
51
52 53 54 55
Fig.7.2. BYU 17165 Neural spines in left lateral uiew. I = intercostal plates. Note neural spine fusion between S1-SJ. Scale bar: 10 cm.
D 12 rib
- .ul
\
Fig.7.3. BYU 17165 Dorsal 72 rib ftrsed to ilium.
182
.
Virginia Tidwell, Kenneth Stadtman, and Allen Shaw
-\-
All of the ribs in D12-S5 are fully fused to both ilia. The ribs of D12 are of the normal, dorsal-rib style and are not modified into a broader sacral rib; the tips are completely fused to the vertebra at both the capitulum and taberculum, as well as to the medial surface of the ilia. There is a flat, broad, and rugose "pad" of bone on the dorsal surface of each sacral rib, except S1; this pad is most prominent on 52 and 53. The ilia are set at 1,7" relative to the axis of the vertebral column, and they have a relatively short pubic peduncle. Both are somewhat distorted due to taphonomic compression causing the acetabular region on the right side to be shortened anteroposteriorly. This shortening is accompanied by a lateral expansion of the anterior portion of the ilium, which causes the preacetabular portion of the ilial blade to flare widely. In spite of the distortion evident in the ilial blades, none of the sacral ribs, nor those of dorsal 12, have become separated from either the sacral vertebrae or the ilia. This suggests that the ilia were widely flared in life and that the taphonomic distortion rvas minimai in this specimen. Discus sion/Conclusion
In the past little has been done to document the range of variation within various sauropod groups, due mostly to the paucity of specimens. However, a relatively large number of individuals of Cama' rdsAurus have been described over the years, with additional specimens coming to light more recently. Certain features have been recognized as age-related, including large size, entheses on the neural spines, and highly rugose articular surfaces of the limbs. Specimens demonstrating such morphologies include AMNH 690, BYU 9047, and \7DC-BS 14. Ontogenetically, the dorsal and caudal vertebrae are incorporated into the sacrum, as they fuse to the two primary sacral vertebrae (Mclntosh et aI. 1,996a, 7996b). The recent addition of several new adult examples ol Camarasaurus show ad-
ditional variation among mature individuals (see Ikejiri et al., this volume). Table 7.7 presents several sectors where significant degrees of morphologic variation are found among mature individuals (see also Mclntosh et al. 7996a,1.996b), including BYU VP 17465 and other new specimens as well. These sectors mostly involve points of fusion between various elements lvithin the sacrum: a pattern of fusion in the vertebral centra and neural spines, a fusion of sacral ribs to the ilium, the presence or absence of "intercostal plates," and a degree of flare in the preacetabular blade of the ilium. A significant amount of variation is apparent within Camardsaurzs, most of which is not taxonomic, but rather reiates to the relative age of each individual. In most adult sacra, the neural spines of S2-S4 are fused, although this sequence is displaced forward in C. lewisi and BYU VP 17465 (S1-S3), or expanded to include the fifth sacral (AMNH 690). However, in the adult specimen GMNH 101, only S2-S3 are Age-Related Characteristics Found in a Partial Pelvis of Camarasaurus
.
183
TABLE 7.1. Variation in Camarasawrus Sacral Morphology
Number
Centra
of sacrals fusion
Specimens
Neural S2-5 51 Supraspine lateral pleuro- costal fusion fossa coel plates
Camarasaurus BYU 17465
6
?
5
s1-s5
S1-S3
BYU 9047
\rDC-BS
5
!
1-3 /,-4
GNMH AMNH AMNH
14
101
6
5761
4
690
6
? s2-s5 D12 &
2-3 2-4
?
Y
N X N
2-s
D12 rib
Metapophsupracostal
ligarnent
YY
N
NY NY XN XN NN
Y Y N
N N
Ilial flair
fuse to
\(/
Y
\x/
ilium
N
MN MY MN MY
S1_S5
UUVP 5309
5
Sahasaurus
6
Pieropolis tltanosaur
6
Y-
yes;
N : no; M :
s1-s5 s1-s6 s1-s6
moderate ilial flair;
1-3
Y
1-6
N N
1-6
N N N
N N N
N
w w
Y
W - rvide ilial flair; X : inforn.ration unavailable
fused (Mclntosh et al. 1996b), as is the case in younger individuals. Several large individuals (BYU 77465, GMNH 101, and AMNH
690) incorporate the rib from dorsal 12 into the anterior blade of the ilium. However, this is not universal among large individuals as seen by the old individual of C. lewisi (ByU 9047), a fully mature C. lentus (\7DC-BS 14), and the younger but larger C. supremus paratype (AMNH 576I). Documenting the number of fused centra within adult sacra is problematic, because several specimens are missing some or all of the centra (GMNH 101, \fDC-BS 14). Cen-
ranges include S2-S5 (AMNH 5761), S1-S5 (BYU 9047), and D12-55 (AMNH 690). Previously, the holotype of C. lewisi (BYU 9047) had the only sacrum known to exhibit "intercostal plates" on the dorsal surface of the sacral ribs, suggesting ro various aurhors that these plates represent a feature unique to this species (Jensen 1988; Mclntosh et al. 1996a). Similar, though slightly smaller plates have recently been found on a Cdmdrasaurus lenttts sacrum from Thermooolis. Wyoming (\7DC 14) (see Ikejiri et a1., this volume), and rhey are also present in BYU VP 1.7465. All of these sacra exhibit features suggestive of aged individuals: entheses (ossified interspinai ligaments) connecting the neural spines, highly rugose edges of articular surfaces, and large size. Although the specific identity of the Dry Mesa Cdmarasdurus is not known, it is unlikely to be C. lewisi because none of the posterior dorsals from the quarry can be referred to that species. Therefore the presence of "intercostal plates" on
tra fusion
184
.
Virginia Tidwell, Kenneth Stadtman. and Allen Shau'
the Thermopolis Cdmarasourus lentus and BYU VP 17465 precludes this feature from use as an autopomorphy for the species C. lewisi.\ife suggest that these plates are likely an individually variable ontogenetic feature, even though they are not found in the old individual AMNH 690. Alternativei,r', perhaps their presence is related to sexual dimorphism. Sir sacral vertebrae and a rvidely flaring ilium are often cited as synapomorphies of the Titanosauria, and are routinel)r found in the data sets of various authors (e.g., \(/ilson and Sereno 1998, Upchurch 1998, Salgado et al. 1997).In many cases the additional sacral vertebra is the last dorsal (dorso-sacral of Mclntosh, see this volume), whose dorsal rib often fuses to the ilium. In BYU VP 17465 there are simiiarities with the titanosaurs Saltdsaurus and the titanosaurid sauropods from Pieropolis, Brazil (Table 7.1). We interpret these similarities as a mixture of ontogeny (six fused sacral vertebrae, dorsal 12 rib fused to the ilium) and convergence (widely flaring ilium). This interpretation is based on the relatively large sample size of Carnarasaurrls sacra available for comparison. The broad range of morphologic variation found in Camardsaurus, documented here for the pelvis, provides a cautionary note for those rvorking with less well represented taxa' Even in a genus as well known as Camarasaurus, the effects of ontogeny and sexual dirnorphism are difficult to assess, highlighting the need to document significant examples of variation wherever they appear in the sauropod fossil record. As additional specimens are found, it becomes possible to record a greater range of variation within the genus, and to begin to investigate possible causes for this variation' Not only will this encourage taxonomic stabilitl-, it also provides a control group for character coding in phylogenetic analvsis. References Cited
Curtice, B., and D. R. \filhite . 1996. A re-evaluation of the Dry Mesa Dinosaur Quarrv sauropod fauna with a description of juvenile sauropod elements. In Geology and Resources of the Paradox Basin, 325-338. Utah Geological Association Guidebook, no. 25. Salt Lake City: Utah Geological Association. Ikejiri, T., V. Tidrvell, and D. Trexler. 2004. New adult specimens of Catndrdsaurlts lentus highlight ontogenetic variation within the species. This volume. Jensen, J. 1988. A fourth new sauropod dinosaur from the Upper Jurassic of the Colorado Plateau and sauropod bipedalism. Great Basin Natu-
ralist 48Q\: 121-145. N{clntosh, J.S., \tr E. Nfiller, K. L. Stadtman, and D. D. Gillette. 1996a. The osteology of Camarasaurus lewisi (Jensen 1,9881. Brigham Young
Uniucrsitl' Gcologl' Sttrdies 4 | : -l-l 15. Mclntosh, J.S., C.A. Miles, K. C. Cloward, and J. R. Parker. 1996b. A new nearlv complete skeletorr of Camarasattrrts. Bulletin of Gunma Museum of Ndtural History 1: 1-87. Salgado, L., R. Coria, and J. Cako. 7997. Evolutior.r of titanosaurid sauropods. I: Ph1'logenetic anall'sis based on the postcranial evidenceAme gh iniana 34( 1 ): 3-32. Age-Related Characteristics Found in a Partial Pelvis of Camarasaurus
'
185
Upchurch, P. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journdl of tbe Linnean Society I24: 43-103. \Wilson, J., and P. Sereno. 1998. Early evolurion and higher-level phylogeny of sauropod dinosaurs. Jottrnal of Vertebrate Paleontology 18, supp.
to no.2. Memoir 5: 1-68.
186
.
Mrginia Tidwell, Kenneth Stadtman, and Allen Shaw
8. Ontogenetic Variation and Isometric Growth in the Forelimb of the Early Cretaceous Sauropod Venenosaurws VrncrNre TInwpLL AND D. Rev WtrHIrp
Abstract The recent discovery in Utah of adult and juvenile skeletons of the titanosauriform sauropod Yenenosaurus dicrocei, co-occurring in a single bone bed, provides an opportunity to examine ontogenetic variation, which is poorly understood in sauropod dinosaurs. Several caudal vertebrae, a pneumatic dorsal rib head, a left ulna, and four metacarpals are common to both individuals. The similarity in overall morphology indicates that these two specimens are conspecific, whereas minor differences between the adult and iuvenile specimens highlight possible ontogenetic features. The adult and juvenile specimens have the same least circumference:length ratio of the ulna, as well as simiiar proportions of the manus relative to the ulna, indicating the taxon employs an isometric growth strat'$Thereas egy. this agrees with most recent studies of sauropod bone growth, it contrasts with other dinosaur groups in which iuveniles display allometric grou'th patterns.
187
Introduction The range of ontogenetic variation in sauropod dinosaurs is poorly understood, due to the paucity of well-preserved juvenile specimens and a lack of detailed description where those specimens are known. Confusion regarding the ontogenetic significance of morphologic characters compounds this problem. Although sauropod fossils are found on every continenr, the vast majorit,v of reported specimens are adults. Yet, a number of juveniles are known: Bellttsaurus (Dong 1990), Patagosattrus (Coria 7994), "Pleurocoelu.s" (Marsh 1888, and Lull 1911), Astrodon (Carpenter and Tidwell this volume), CamarAsdurus (Giimore 1925), Phuwiangosaurus (Martin et al. 19941, and Apatosaurus (Peterson and Gilmore 7902), with particularly
high numbers reported from the Morrison Formation of North America (Foster, this volume). However, detailed morphoiogic description of juvenile material has been published only for Cdmarlsaurus, Pleurocoelus, and Phutuiangosaurus. Comparisons to adult individuals at the generic level are even more rare and are restricted to Camardsaurus and Apatosaurus (Foster 1995; Wilhite and Curtice 1998; Carpenter and Mclntosh 1994;Ikejui et a1., this volume). ConsequentlS litrie is knor,vn abour onrogenetic variation within sauropod taxa, resulting in the porenrial for misidentification of specimens. RecentlS the Denver Museum of Natural History opened a dinosaur quarry in Lou.'er Cretaceous sediments in Eastern Utah, which contains adult and juvenile skeletal parts of the titanosauri-
form
Venenosdurus dicrocei (Tidwell et al. 2001). This cooccurrence provides a rare opportunity to study ontogenetic variation within a single sauropod taxon. Materials. The larger specimen (DMNH 40932) includes right metacarpals I, II, IV and V; the left metacarpal III; the left ulna; and a pneumatic dorsal rib head, in addition to other elements of the forelimb, pelvic girdle, and several caudal vertebrae. The smaller specimen (DMNH 40930) includes the right metacarpals II and III; left metacarpals II, IV, and V; the right ulna; and a dorsal rib head, in addition to a poorly preserved cervical centrum and several caudal centra.
Institutional abbreuiations. DMNH-Denver Museum of Narural History; CM-Carnegie Museum of Natural History; SMUSouthern Methodist University; and TMM-Texas Memorial Museum.
Description Ulna (Fig. 8.1A, B). The adult ulna is almost perfectly preserved, missing only the proximal end of the lateral process, whereas the juvenile ulna is almost complete. However, the ulnar shaft of the juvenile was shattered and shor,vs moderate distortion in the reconstructed mid-shaft region, causing the proximal end to bow medially. Nevertheless, the overall proportions of both ele188 . Virginia Tidwell and D. Ray Wilhite
Fig. 8.1. Venenosaurus right ulnae in proximttl, medial and distal uiews: (A) adult (B) juuenile lreuersedt. Abbreuiations: u = ole cranon ; d = p oster ior pf o cess. Scale bar: 10 cm.
ments are quite slender, with a small proximal end and gracile shaft. In the adult, the proximal end shows a small amount of rugosity, and a moderately developed olecranon, 'uvhereas the juvenile
ulna lacks rugosities and shows a poorly developed olecranon. In the proximai ends of both elements the elongate mediai wall terminates in a pronounced medial process, lvhich is also found in the adult forms of Ceddrosaurus, Isisaurus, and Saltasaurus (Tidwell et al. 7999; Jain and Bandyopadhyal' 1997; 'Wilson and Upchurch 2003). The rnedial wall almost forms a 90-degree angle with
the lateral wall, forming a radial notch between them, as in Cedarosaurus and Pletrocoelus. In proximal view, a welldeveloped process is seen on the posterolateral corner of both
ulnae, being more prominent on the luvenile ulna due to taphonomic deformation. A broad groove bordered by two ridges extends distally from mid-shaft along the anteromedial side of the shaft and aligns with a low ridge found on the lower-lateral side of the radius. Metacarpals (Fig. 8.2). The adult metacarpals form a tightly articulated column, with metacarpal I facing anteromedially, Ontogenetic Variation and Isometric Growth in the Forelimb ol Venenosaurus
.
189
ill .:.:-'
.r$u
1l'
'"':a...'
ill tt I
'1..
1.,
zL.
' '.
i
'
-'
A
Fig. 8.2. Proximal uiews of (A) adub Yenenosauts right metacdrpals l, il, lV, V, left III (reuersed) ; (B ) juuenile Venenosaurus right metacarpal Il, III, and left IV, V. Scale bar: 5 cm. (C) Pctsterior uietus of adub and juuenile Venenosaurus metacarpals Il-V. Note similarity in proportions between adub and juuenile elements. Scale bar: 70
ltil
\-, i
\l
B
V
rffi \,,
ill
cm.
IV
V
metacarpal III facing anrerolaterally, and metacarpal V facing posterolaterally (measurements in Table 8.1). The deeply rugose proximal end of each adult metacarpal has a distinct morphology,
which is also discernible in the corresponding juvenile element. However, in the juvenile specimens the proximal ends are somewhat more rounded. All of the metacarpals possess a gracile, elongate shaft. The distal condyles of meracarpals II-IV of the adult are small, asymmetrical, and separared by a shallow groove. This groove is missing from metacarpal V of the adult, which is relatively flat, but it is found distally on all juvenile metacarpals. The prorimal end of the adult metacarpal II is nearly recrangular, with a slight rounding of the anterior edge. The mediai side is slightly convex, articulating with the slightly concave lateral side of metacarpal I. A flat, broad, articular surface spans the posterior side, with distinct striations exrending ventrally almost to midshaft. They culminate in a broad, rugose surface of bone that forms a wide, tendoneous attachment point. Although the juvenile metacarpal II resembles the adult in most respects, neither striations nor rugose surfaces are found on the juvenile element.
190
.
Virginia Tidwell and D. Ray \Tilhite
TABLE 8.1. Measurements and Ratios of Appendicular Elements Common to Both Adult and Juvenile Specimens of Venenosaurws
Greatest Least Least Greatest Side Length proximal breadth breadth/L proximal/L Adult MC II Juv. MC II Juv. MC II Adult MC III Adult MC IV Jur'. MC IV Adult MC V Juv. MC V Adult ulna Juv. ulna
R
367
86
48
0.13
0.24
L
190
42
25
0.13
0.22
R
184
NA
L-)
0.13
NA
L
359
99
53
0.15
0.28
R
333
101
51
0.15
0.3
L
174
50
25
0.14
0.29
R
300
86
+a ^/
0.15
0.29
L
148
43
20
0.r4
0.29
R
765
265
88
0.1.2
0.35
L
427
113
51
0.1.2
0.33
The triangular proximal end of metacarpal III of the adult is broad in anterior view, whereas the lateral and medial articular surfaces are slightly narrower. A series of ridges extends ventrally aiong the medial articular surface, but is not found on the lateral articular surface. Similar ridges are found on the juvenile element. However, a strong mid-shaft rugosity found on the adult element is poorly developed on the juvenile. Proximally, metacarpal IV of the adult is triradiate, and bears a strongly concave lateral side. The posterior edge of the medial side extends down the shaft in a sharp ridge that terminates at midshaft. There is no mid-shaft rugosity on this element, unlike on metacarpals
II and III. The proximal end of the juvenile left
metacarpal IV is crescentric, although erosion has removed the anteromedial corner. Proximally, the lateral side is only moderately concave! in sharp contrast with the deep concavity of the adult. The nearly circular proximal end of the adult metacarpal V narrows to a sharp posterior ridge. This ridge extends ventrally in a sigmoid curve along the posterolateral surface, terminating at midshaft. This distinctive, teardrop-shaped proximal end and a similar ridge are found on the juvenile element. Although the shaft is
straight, the lateral side bows inward considerably on both the adult and juvenile bones. Dorsal ribs (Frg.8.3). The right dorsal rib of the adult consists of the head and proximal portion of the shaft; it measures 619 mm. Although the original shape of the rib has been distorted, a large fossa situated on the capitulum is well preserved. A smaller pneumatic cavity opens from this fossa into the proximal portion of the Ontoeenetic Variation and Isometric Growth in the Forelimb of Venenosaurus
.
1,91,
Fig. 8.3. Adult and juuenile Venenosaurus dorsal rib heads. Note large pneumdtic foramen on adub, and small fossa on juuenile rib. Scale bar: 5 cm.
capitulum. In the juvenile specimen, the right dorsal rib completely lacks the capitulum, and the robust tuberculum shows a small amount of weathering. The shaft is slightly distorted from crushing. Total preserved length is 161 mm. A small, circular fossa is located at the base of the tuberculum on the posterior side and measures 18 mm long and 12 mm high. This fossa is not connected to any internal cavities within the rib head. Discussion Table 8.1 demonstrates the remarkable similarity in the proportions of the appendicular elements between the adult and juvenile Venenosaurus. The least breadth:length ratios of the adult and ;uvenile are identical in the MC II and again in the ulna, and only slight differences are found in MC IV and in MC V. For all forelimb elements measured, the greatest proximal breadth:length ratio is slightly greater in the adult. This differs from the finding of \X/ilhite
(1999) in which the juvenile elemenrs of Camarasdurus were shown to be slightly more robust than in the adult. Wilhite (1999) demonstrated that various limb ratios could be used to illustrate isometric growth in the appendicular skeleton of Camardssurus. Isometric growth has also been reported in a limited study of
the hurnerus of Apatosaurus (Carpenter and Mclntosh 1994). These studies indicate that isometric growth is common in the appendicular skeletons of some sauropods. It seems clear that sauropod dinosaurs employed a different growth strategy than simple allometry. 192
.
Virginia Tidwell and D. Ray S7ilhite
In contrast, most large mammals grow
allometrically
TABLE 8.2. Growth Patterns in Dinosaur Limbs Grow-th Pattern
Reference
a^.^--.^U4r Prrrru
a,,u ^-,1
Mclntosh 1994 \Tilhite 1999 Foster 1995
Isonretric growth tn Apatosaurlls humerlls. Isometric gror.vth in Camarasaurzs limbs. Juvenile limbs are onl,v slightly more robust than adults.
Notes onl,v slight allometry in some sauropod limbs.
Britt and Naylor
srowth in axial skeleton of Camara-
1994
)f;::"'.
Martin 1994 Smith 1999 (-.r^".t"r | 994
Significant allonletric growth in limbs of the sauropod P hua,idtlgo s cturus. Allometric gro\\'-th in Allosaurus lirnbs. Allometric growth in Dryosaurus skull and limbs.
Horner et al. 2000
Allometric growth
ir.r
hadrosaur limbs.
(relative proportions of various elements change throughout ontogeny), because body size increases as a cubic function, whereas bone diameter increases as a squared function (\X/alker and Liem 19941. \il/alker and Liem, however, acknowledge two other means by which an organism may compensate for changes in mass. One is by changing the nature of the bones by becoming denser, and the other is by changing the fundamental design of the bones. Curry (1999) demonstrates that in at least one sauropod, Apatosaurus, bone structure was remodeled as the animal matured. Curry proposes that one reason for this might have been to compensate for increased loading of the bones as the animal grew This brief study of nvo individuals of Venenoscturus stands in contrast to reports of isometric grolvth in the sauropod Pbuwiangoscturus (Table 8.2). Martin (1994) reports that juvenile femora of Pbwwiangosaurus are more elongate than the femora of adult individuais, whereas juvenile humeri are much more expanded at the proximal and distal ends, suggesting allometric growth in the limbs of this genus. The published figures for the adult (Martin et al. 1999, fig. 12) and early juvenile PhuwiangosAurus (Martin 1994, fig. 7) appear to support Martin's suggestion, provided these elements are indeed all referable to that taxon. Britt and Naylor (1994) postulate allometric growth in the skull, neck, and tail of the juvenile Camardsaurzs CM 11338, although no mention is made of limb proportions. A number of authors have reported changing limb proportions throughout ontogeny among hadrosaurs (Horner et al. 2000), ornithopods (Carpenter 1994), aod theropods (Smith 7999).
Dorsal ribs displaying pneumatic fossa are found in Brachiosaurus. an Early Cretaceous brachiosaur from Texas SMU Ontogenetic Variatron and Isometric Growth in the Forelimb of Venenosaurus
. I93
61732 (Gomani et aI. 1999); Astrodon (Carpenter and Tidwell, this volume); and Alamosdurus (TMM 47547), in addition to VenenosAurus. All of these taxa fall within the titanosauriform clade, as defined by Salgado et aL. (7997), although recently a pneumatrc rib has also been reported in the diplodocid Supersaurus (Lovelace 2003). The location of fossae on dorsal ribs appears to be variable, occurring on either the tuberculum (Brachictsaurus brancai). the capitulum (Venenosaurals, DMNH 40930), or near the junction of these two processes (Brachiosaurus ahithorax, Venenosaurus DMNH 40932, the Texas brachiosaur SMU 61732, and Alamosaurus) . The Venenosaunt s specimens suggest that the development of fully pneumatic fossa in the rib heads may be ontogenetic, be-
cause the fossa found on the juvenile Venenoscturus ls not connected to any internal cavities. It is likely that these inrernal structures are developed over time as the pneumatic diverticula reshape the surrounding bone, as suggested by Britt (1993). However, it is possible that the degree of pneumatic deveiopment is related to the placement of the ribs along the dorsal column, as suggested by Wilson and Sereno (1998).If true, the lack of pneumaticity in the juvenile rib may be attributed to a more posterior placement as compared with the adult rib.
Conclusion The two Venenosaurus specimens display several similarities in the ulna and metacarpals that strongly suggest they are conspecific: (r7 a prominent medial process on the ulna; (2) a paired ventral ridge ertending dorvn the shaft of the ulna; (3) a distinct morphology of each metacarpal proximal end in both specimens, particularly MC V; (4) clearly marked striations (tendoneous scars) on MC III; and (5) small distai condyles on MC II-V. These individuals also demonstrate several ontogenetic characters. The larger specimen is considered an adult, although probably not old, because of: (1) solid fusion of the caudal neuro-cenrral suture; (2) well-developed striations and rugose processes (ligament, tendon, and muscle scars); and (3) the presence of pneumatic foramen in the dorsal rib. The juvenile specimen displays significant morphological differences that we interpret as age-related characteristics: (1) poor development of the olecranon; (2) lack of rugosities on the articular ends of the ulna and metacarpals; (3) a lack of posterior process (well-developed iigament and tendon attachment sites) on the metacarpals; (4) an unfused caudal neuro-cenrral suture, and (5) a size only 40"/" of the larger specimen. Nfe have documented the isometric narure of iimb develooment rn Venenosaurus, which supports other ontogenetic srudies of sauropod forelimb proportions. Why sauropod forelimbs should diverge from the allometric growth strategy common to other dinosaurs (e.g., Smith 1.999,Horner et aI.2000) is unclear, but perhaps future research can shed additional light on this subject. Although previous studies have focused on Late Jurassic taxa, 191 . Virginia Tidwell and D. Ray Wilhite
Venenosaurus is from the Early Cretaceous, sauropod evolution is poorly understood.
a period in which
References Cited
Britt, B. B. 1993. Pneumatic postcranial bones in dinosaurs and other archosaurs. Ph.D diss., University of Calgary, Alberta. B. B., and B. G. Naylor. 1,994. An embryonic Camarasaurus (Dinosauria, Sauropoda) from tl.re Upper Jurassic Morrison Formation
Britt,
(Dry Mesa Quarry, Colorado). In K. Carpenter, K. Hirsch, and J. Horner, eds., Dinosaur Eggs and Babies, 256-264. Neu' York: Cam-
bridge University Press. Carpenteq K. 1994. Baby Dryosaurus lrom the Upper Jurassic Morrison Formation of Dinosaur National Monument. In K. Carpenter, K. Hirsch, and J. R. Horner, eds., Dinosdur Eggs and Babies, 288-297, New York: Cambridge Universit,v Press. Carpenter, K., and J. Mclntosh. 1994. Sauropod babies from the Morrison Formation. In K. Carpenter, K. Hirsch, and J. Horner, eds., Dinosaur Eggs and Babies, 265-278. New York: Carnbridge Universit,v Press. Coria, R. A,. 1994. On a monospecific assemblage of sauropod dinosaurs from Patagonia: Implications for gregarious behavior. Gaia 10
209-213.
Curry, K. A. 1999. Ontogenetic histology of Apatosaunzs (Dinosauria: Sauropoda): New insights on growth rates and longevitl'. Journal of Vertebrate Paleontology 19 (4): 654-665.
DongZ. 1990. Sauropoda from the Kelameili Region of the Junggar Basin, Xinjiang Autonomous Region. Vertebrdta PalAsiatica 28: 43-58. Foster, J. 2004. New juvenile sauropod dinosaur material from western Colorado, and the record of juvenile sauropods from the Late Jurassic age
Morrison Formation. This volume.
Foster, J. R. 1995. Allometric and taxonomic limb bone robustness variability in some sauropod dinosaurs. Journal of Vertebrate Paleontol-
ogy 15(3): 29A.
\7. 1925. A nearlv complete articulated skeleton of Camardsdurus, a dinosaur from the Dinosaur National Monument, Utah.
Gilmore, C.
Memoirs Cdrnegie Museum I0: 347-384. Gomani, E. M., L. L. Jacobs, and D. A. \fir-rkler. 1999. Comparison of the African titanosaurian Mdlatuisaurus, with a North American Early Cretaceous sauropod. In Y. Tomida, T. H. Rich, and P. Vickers-Rich, eds., Proceedings of the Seccnd Gondwanan Dinosaur Symposium, 223-233. National Science Museum Monographs, no. 15. Tokyo: National Science Museum. Horner, J. R., A. de Ricqles, and K. Padian. 2000. Long bone histology of the hadrosaurid dinosaur Maiasaura peeblesorum: Growth dynamics and physiology based on an ontogenetic series of skeletal elements. Journal of Vertebrate Paleontology 20: 175-129. Ikejiri, T., V. Tidwell, and D. Trexler. 2004. Ontogenetic variation in Camdrctsdurus lentus. This volume. Jain, S. L., and S. Bandyopadhyay. 1997. New Titanosaurid (Dinosauria: Sauropoda) from the Late Cretaceous of Central India. Journal of Vertebrate Paleontology 17 : 114-136. Lovelace, D.2003. Evidence for costal pneumaticity in a diplodocid dinosaur (Seismosaurus uiuanae). Jowrnal of Vertebrate Paleontology.
2313\:,734. Ontoeenetic Variation and Isometric Growth in the Forelimb o{ Venenosaurus
.
195
Lull, R. S. 1911. The Reptilia of the Arundel Formation. Maryland Geoo gi ca I Suru ey, L ou er Cr eta ce o tt s : 17 7-21. 1.. I
Marsh, O. C. 1888. Notice of a new genus of Sauropoda and other neu. dinosaurs from the Potomac Formation. American Journal of Science 35. series 3:89-92.
Martin, V. 1,994. Bab,v sauropods from the Sao Khua Formation
(Lor,ver
Cretaceous) in Northeastern Thailand. Gaia 70: 147-153.
Martin, V., V. Suteethorn, and E. Buffetaut. 1999. Description of the type and referred material of P htnuiangct saurus s irindh r.trnae ly'rartin, Bttffetaut and Suteethorn, L994, a sauropod from the Lolr,er Cretaceous of Thailand. Oryctos 2: 39-91.. Powell, J.E. 7992. Osteologia de Saltasaurus loricatus (Sauropoda-Titanosauridae) del Cretacico Superior del Noroeste Argentino. In J. L. Sanz and A. D. Buscalioni, Los Dinosdurios j, su entorno biotico,
165-230. Actas del segundo Curso de Paleontologia en Cuenca. Cuenca: Instituto "Juan de Valdes."
Salgado, L., R. Coria, and J. Calvo. L997. Evolution of titanosaurid sauropods. Vol. 1: Phylogenetic analysis based on the postcranial evidence. Ameghinidna 34 3-32. Smith, D. K. f999. Patterns of size-related variatior.r within Allosaurus. Journal ctf Vertebrate Paleontology 7912): 403-404. Tidwell, V., K. Carpenter, and B. Brooks. 1999. New sauropod fi'om the Lower Cretaceous of Utah, USA. Oryctos 2: 21,-37. Tidwell, V., K. Carpenter, and S. Meyer.2001. A new Titanosauriform (Sauropoda) from the Poison Strip Member of the Cedar Mountain Formation (Lower Cretaceous), Utah. In D. Tanke and K. Carpenter, eds., Meso;oic Yertebrate Life, 137-165. Bloomington: h.rdiana Uni-
versity Press.
\7alker, \7. F., and K. F. Liem. 1994. Functiondl Andtomj, of the Vertebrates: An Euolutionary Perspectiue. 2nd ed. New York: Saunders College Publishing.
lfilhite, D. R. 1999. Ontogenetic variation in the appendicr-rlar skeleton of the genus CarnarasAtrrus. Master's thesis, Brigham Young Universitl.. D. R., and B. Curtice. 1998. Ontogenetic variarion in sauropod dinosaurs. Journal of Vertebrate Paleontologl, 18(3): 86A. \filson, J., and P. Sereno. 1998. Early evolution and higher-leve1 phylogenv of sauropod dinosaurs. Journal of Vertebrate Paleontologl, 1 8, supp. to no. 2, memoir 5: 1-68.
'lfilhite,
196
.
Virginia Tidwell and D. Ray \Tilhite
Part Three Body Parts: Morphology and Biomechanics
9. Neuroanatomy and Dentition of CamarasAurus lentus SeNren CuerrnnJEE AND ZHoNc ZnBNc
Abstract
A
of Camdrasaurus lentus from the Upper Morrison Formation of Dinosaur National Monument Jurassic provides critical information about its neuroanatomn tooth morphology, and tooth replacement pattern. The braincase is coossified to the frontals and parietals, and shows the pattern of the disarticulated skull
cranial foramina. The endocast reveals the primitive architecture of the brain, which is short, narroq and deep, with prominent cerebral and pontine flexures. Tooth morphology and wear indicate that Camarasaurus consumed coarse, fibrous plant material. The tooth replacement pattern is from the back to the front as in other reptiles.
Introduction Camarasaurus was the most common sauropod in North America, and it is represented by several complete and partial skeletons from the Upper Jurassic Morrison Formation of Col-
orado, Utah, Wyoming, Montana, and New Mexico (Mclntosh
199
i,
,\ 1 [,i a1 ,Hr ..j+
1.,,
qJ
po
Sq
'i:"t'
'.' 1: ;._.t-
l
j,,_.l.,,,.;,1.
,..... *-.,-i**-"'l' ,,rti-'' \6 '
,
i' : 1 . l.l*
:k' an
l"--""
.:* * -_...-
.
'\",.1 *"'t4-i"!'"":--'4-'r.-.."t'':Lr',,,, .* -:r..... :..r,.;.. :....r!r13{*;!rr-,. :, ';,
_
.-q:€:t".'
'-
G f:s, c).1. Restoration of tbe skull ,- C:imarasaurus lentus /DINO
)t :rt ltterdl (A), dorsal (B), ond :.,::,tl (C) t,ieus. The lower jatu - Carnarasaurus lentus
l.
IDINO
:,i ltterttl (D), medidl
1E1,
.:, .:.i! r iew of the conjoined :r :, i.ttt,s (F), and uentral weu, - :, . tu u luwcr jau s tC t. Fr,r .i,',iIL.t i.ttio|ts, see chapter i??rjtilix. Heaut, bdr = -i cnt.
1990).It is a medium-sized sauropod (-18 m long), u'ith a short, high skull, short neck, high shoulders, compact body, and a short tail. Although many specimens of Camarasaurus are in ercellent condition, our knowledge of rhe detailed anatomy of the skull, especially the braincase, is limited. White (1958) described a braincase (DINO 28) of Cdmarasaurus lentus (Marsh) from the Dinosaur National Monument in Utah, but his description was brief and the material needed further preparation for detailed anaiysis. Recently, Madsen et al. (1995) provided a comprehensive description of the skull of Cdmdrasaurus.The presenr study is based on a disarticulated skuil of Camarasdurus lentus (DINO 28). rvhich is virtually complete and excellently preserved (Zheng7996); it is refigured here as a reference (Fig. 9.1). It provides three-dimensional anatomical information of the neuroanatomy, dental morphology, and tooth replacement phenomenon in great detail.
Institutiondl abbreuiations. CM-Carnegie Museum of Nat-
ural History; DINO-Dinosaur National Monument, 200 .
Sankar Chatterjee andZhongZheng
Utah;
TTUP-Paleontology Division, Museum of Texas Tech University; and YPM-Yale Peabodv Museum. Neuroanatomy of Camarasaurus Braincase. The first detaiied description of the braincase of Camarasaurus was provided by White (1958) on the basis of DINO 28, which is used here again after further preparation. Most of the previous study remains valid; therefore, the focus of the description will be those regions not visible in the earlier description, as well as amendments of his interpretations of the otic capsule. Madsen et al. (1995\ also discussed the braincase of Camarasaurus based on other material.
The basioccipital (Fig. 9.2C) forms the ventral floor of the braincase. It is the major part of the occipital condyle and is overlaid by the two exoccipitals on the side of the foramen magnum. In DINO 28, the condyle extends considerably backward, about 50 mm behind the foramen magnum. In occipital view, the basioccipital has a typical hemispherical condyle, from which two basal tubera are directed ventrally. The ends of the basioccipital tubera are truncated and pitted, indicating the presence of a cartilaginous extension. A median notch separates these tubera. In Shunosaurus, oll the other hand, this division is not clear-cut, and the two tubera are almost conjoined. Fon'vard of the condyle, the basioccipital is constricted to a neck and then flares again. A basioccipital recess is present rostral to the tubera.
D
Fig. 9.2. The braincase of Camarasaurus lentus iiz occipital (A), Iateral (B), caudouentral (C), and rostrouentral uiews (D). For abbreuiations, see chaPter appendix. Scale bar: 5 cm.
Neuroanatomy and Dentition ol Camarasaurus lentus
.
201
In lateral aspect, the basioccipital is completely hidden by
a
large wall of the crista prooric and forms part of the lor.ver margin
of the metotic fenestra. Further forward, it is strongly clasped by the basisphenoid. As in other sauropods, the otic region shows two distinctive fenestrae; the rostral one is the fenestra ovalis for the reception of the footplate of the stapes. The caudal fenestra is the
metotic foramen through which nerves IX-XI and the caudal branch of the jugular vein are transmitted. Both foramina are closed off dorsally by the opisthotic. Farther rostral to the fenestra ovalis, the exit for the facialis (VII) nerve is seen in the prootic. The basisphenoid and parasphenoid 1Fig. 9.2P., C) are intimately fused and very difficult to delineate. This compound bone is triradiate, wirh the two basipterygoid processes directed ventrolaterally, and the parasphenoid rosrrum is directed rostrally. The basisphenoid is attached ro rhe basioccipital by a transverse suture. The two basipterygoid processes are stronglv built and inserted into the pterygoids. In the rostral aspect, trvo distinct ridges extend from the ventral part of the parasphenoid rostrum to the tip of the basipterygoid processes. These t-uvo ridges form a smooth platform between the two pterygoid processes. Lateralln the basisphenoidparasphenoid complex is overlapped considerably by the prooric. At the confluence of the basisphenoid and parasphenoid rostrum, a large depression on the lateral surface of the braincase is the site for the attachment of the rectus muscle of the eye. The parasphenoid rostrum forms a rvide vertical blade and inserts into the interpterygoid vacuity. At the base of the rostrum, a vertical wall, the dorsum sella, extends from the basisphenoid on either side of the pituirary fossa to articulate lvith the orbitosphenoid. The dorsum sella is pierced by the opening for cranial nerve VI. Medial to it, the cranial opening for the internal carotid artery is visible. The pituirary cavity is not exposed as in Shunosaurus; instead it is rostrally covered by the dorsum sella. The exoccipital-opisthotic bones are completel)' fused together (Fig. 9.2A.). The two exoccipitals cover rhe dorsolateral porrion of the condyle and nearly meet along the midline. Each bone shows the opening for the exit of cranial nerve XII (hypoglossal). The opisthotic extends outward and dolvnward to form the paroccipital process that abuts against the squamosal. Here, the postemporal fenestra is located at the juncture of the paroccipital process and squamosal. The fenestra is about 8 mm long and 15 mm wide. In Iateral aspect, the opisthotic is bounded rostrally by the prooric ro participate in the formation of the otic capsule. The prootic (Fig. 9.28) forms the central part of the lateral wall of the braincase. It is bounded by the opisthotic and supraoccipital caudally, the basioccipital and basisphenoid ventrally, the laterosphenoid rostrally, and the parietal dorsally. The prootic forms the caudal margin of the trigeminal foramen (V), which is closed off rostrally by the laterosphenoid. Two shallow channels from the trigeminal foramen are directed dorsally and ventrally; the dorsal channel marks the passage for the maxillary branch of the trigemi-
202
.
Sankar Chatterjee andZhongZheng
nal nerve, and the ventral channel marks the
passage
for
the
mandibular branch. Below the trigeminal foramen, a large lamina of the prootic bone overlaps the basisphenoid-parasphenoid complex. The caudal margin of the prootic is extensive and forms the crista prootic. Viewed medialln the prootic is pierced by the two openings of the facialis nerve (VII). Further ventrally, the lateral opening for the internal carotid artery is seen. The caudal edge is sharp and forms the rostral border of the fenestra ovalis; this ridge extends continuously along the opisthotic to the paroccipital pfocess.
The laterosphenoid (Fig. 9.2B, D) forms the rostral and lateral part of the side wall of the braincase. It is rostral to the prootic and dorsal to the basisphenoid. Dorsal to the trigeminal foramen, it ertends to the medial wall of the supratemporal fenestra. The lateral wall of the laterosphenoid is curved outward and erpanded transversely to form the crista antotica. The lateral end of this process fits into a groove of the postorbital. In Shttnosaurus, this process is well developed. The iateral process is wrapped by the frontal dorsolaterally and the orbitosphenoid rostrally. The orbitosphenoid (Fig. 9.2B, C) forms the rostral wall of the braincase. It is a triangular, plate-like bone that meets at the midline to form a projecting ridge. Dorsal to this symphysis, a Vshaped notch forms the lower margin of the olfactory bulb. The rostral surface of the orbitosphenoid is relatively smooth. It is perforated by the foramen for the optic (II) nerve at the center of the bone. Caudoventralil', there is a iongitudinal groove in the lateral wall of the orbitosphenoid that continues further ventrally to the laterosphenoid. The surface of the groove is very smooth and is marked by the two foramina at the opposite ends. The dorsal foramen represents the exit for the occulomotor (III) nerve, the ventral for the abducens (VI). Further ventrally, the orbitosphenoid articulates with the dorsum sella of the basisphenoid and forms the rostroventrai wall of the pituitary fossa.
The supraoccipital (Fig. 9.2A) forms the caudal roof of the braincase and borders the upper margin of the foramen magnum. The dorsal surface forms a hanging ledge behind the parietal. A distinct median ridge extends along the crest of the supraoccipital and almost disappears at the rim of the foramen magnum. Laterally, the supraoccipital projects like wings; each wing articulates firmly with the opisthotic. Dorsally and rostrallS the supraoccipital is overlaid by the parietal. Endocast. Latex rubber was used to make the endocast of Camarasaurus lentus (DINO 2B). A thin outer shell of the endocast was made so that it could be pulled easily from the endocranial cavity (Chatterjee and Zheog2002). The resulting endocast is relatively short, large, and very deep, and shows prominent cerebraL and pontine flexures (Fig.9.3). The interpreted brain is about 12 cm long, 4 cm wide, and 7 cm high excluding the ventral pituitary body, which projects caudoventrally. The paired olfactory tracts are narrow and enter forward of the cerebrum. The cerebrum has a Neuroanatomy and Dentition of Camarasaurus lentus
.
203
A
X
Fig.9.3. Endocast of Camarasaurus lentus /DINO 28J. (A) lateral uiew; (B) uentral uew. For abbreuiations, see chapter appendix. Heauy $ay = j ,;s.
large dorsal swelling above the level of the olfactory bulbs. A pineal organ is probably present in the front of the swelling because it cor-
responds to the location of the parietal foramen. Hopson (19791 suggested that this swelling of the endocast in sauropods may be an artifact, partly filled in life, or it may have been a space occupied by the dorsal venous sinus. In some forms, this unossified zone penetrates the cranial roof to form a fontanelle, but in others it is covered dorsally by bone. DINO 28 appears to be an adult individual and lacks such a fontanelle. The cerebral region is short, deep, and swollen in appearance. It forms the widest part of the endocast. A vertical ridge that may indicate the boundary between the optrc lobe and the cerebrum marks its caudal part. A pair of optic nerves (II) lies below the level of the cerebrum. The trochlear nerve (IV) rs clearly visible above the optic nerve, whereas the occulomotor nerve (III) emerges further caudally. Sankar Chatterjee and Zhong Zheng
The diencephalon portion is just behind the cerebral region and rostral to the optic lobe. It is relatively large in reptiles, with the prominent flexure forming the highest peak of the endocast. Dorsally this part of the parietal is very thin and could be easily damaged to produce an artificial foramen. Behind this region, the endocast slopes caudally and constricts transversely. The pituitary body is relatively long and oriented caudoventrally. The internal carotid artery enters along the caudal portion of the pituitary. Further rostrodorsally the small abducens nerve (VI) enters the pituitary fossa. The optic lobes are located behind the cerebrum and below the diencephalon. It forms a nearly vertical wall without any swelling. Here three projections may indicate separate branches of the middle cerebral vein: the vena cerabralis medius, which extends downward and outward; the vena cerebralis medius secunda, which is the rostral branch; and the vena capitis dorsalis, which is the dorsocaudal branch (Galton 1985). The cerebellum of Camarasaurrzs is not well marked. It slopes
gradually backward with a prominent dorsal ridge. However, it does not show a dorsal sr,velling as is common in birds and mammals.
The medulla oblongata is relatively short, but extremely broad transversely, in comparison to Shunoszurus. The cranial nerves (V-XII) are located in the ventrolateral side. Rostralln the trigeminal nerve (V) is the most prominent, represented by a massive root, which extends ventrolaterally. Directly behind it lies the small facial nerve (VII). Ventrally there are two branches of the abducens nerve (VI) that run rostrally to enter into the pituitary fossa. The inner ear is partially preserved in Camarasaurus. The semicircular canals are filled with matrix but their courses can be reconstructed from the endocast. The rostral vertical canal appears to be larger than the caudal. Below the canalicular system, a short lagena is visible. A large ganglion is visible in the metotic region for several cranial nerves, stich as glossopharyngeal (IX), vagus (X), and accessory (XI). The hypoglossal nerve (XII) emerges from the caudal portion of the medulla.
Dentition Tooth morphology. In Camarasaurus the crowns are massive, expanded transversely but relatively short. The teeth are homodont, larger in size rostrally', and becoming small caudally (Fig. 9.1). As in other neosauropods, the tooth crowns lack denticles (Wilson and Sereno 1998), which are present only in the lower teeth of Shunosaurus and Omeisaurus among basal sauropods (Chatterjee and Zheng 2002). The dental arcade is parabolic and the occlusal margin is uneven tn Camarasaurus (Figs. 9.1',9.4). To accommodate the curvature, the premaxiilary teeth are obliquely set in the alveoli so that the rostral edge is more medially directed, and the caudai edge is more laterally directed. The maxillary teeth are imNeuroanatomy and Dentition ol Camarasaurus lentus
.
205
A
root'
l\
i-Jf
tuo'"tu,ar]l '.
.].linqual watl
t)
'"t"'o"ntu' ' ,t''
o'o'" ,.'.i,r:.,'\
replacing tooth
Fig. 9.4. Dentition of Camarasaurus lentus (DINO 28). (A) Diagrammatic cross section o/ a tooth in alueolus shouing the relatiue depth of the lingual and Iabial walls; (B) lhgual uiew of the left maxilla shou.ting tootb utear facets, replacing teeth and interdental plates.
ffi ,AY't
.--,i9 10
12
'I l
ll caLrdal ncar
{dcet
g
r;/
ro rostral wear facei
'2
Roslral
clusal vrear iacel
planted parallel to the alveolar margin in regular fashion. In DINO 28, the teeth are so closely spaced that the rosrral edge of one rooth overlaps the caudal edge of the preceding tooth, as in Plateosdurus (Galton 1984) in medial view. This is very different from the condition of Shunosaurus, where the teeth are widely spaced with a sufficient gap between them (Chatterjee and Zheng 2002). There are four teeth in the premaxilla and ten in rhe maxilla making a total of fourteen, which gradually decrease in size from front to back. The tooth formula is: pm 4 + m10 / d12-where pm is the premaxillary tooth, m is the maxillary toorh, and d is the dentary tooth. Lrke ShwnosaurLts, the lower teeth of Camdrasaurus rnrerdigitate with upper teeth in a shearing fashion. There are only two teeth preserved in the right-lower jaw and a single tooth in the left one; all of them are replacement teeth. They do not reach the chewing level and they lack wear facets. In one tooth, the crown is exposed and the root is implanted in the alveolus complerely. The crown is gently tapering to a point and is triangular in lateral view. There is a pronounced middle ridge on the medial surface that extends from the apex of the tooth to the base of crorvn. There is a prominent constriction between the crown and the root. The root is massive and relatively short, unlike the condition rn Shunosdurus, with a circular cross section. The ratio of the exposed part of the tooth to the crown is about 1:1.2 on a\rerage, and there rs no constriction between the root and crown. The tooth crown is typically spatulate rvith rugose enamel on both sides. The implantation is typically thecodont (Fig. 9.aB) where the linguai wall is strengthened by a series of overlapping interdental plates. Each tooth has a distinctive, enamel-covered crown and a deep root. Howeveq the root is not fuily set in the alveolus; instead it is exposed fairly beyond the alveolar margin in lingual aspect. This exposed portion of the root is very extensive in Sbunosaurus (Chatterjee and Zheng 2002). However, unlike the condition of
206
.
Sankar Chatterjee and Zhong Zheng
Shunosaurus, the bases of tooth roots are never exposed rn Camarasaurus. There are different stages of wear on the maxillary teeth. These wear facets are essentiall,v vertical aiong the rostral and caudal ridge of the crown, indicating that the jalv motion was orthal. The jaw articulation is offset and lies r,vell below the line of the tooth row. Upper and lower tooth rows interdigitate and shear past each
other in such a fashion that each lower tooth fits between two upper teeth along their lingual surface, like a garden shear, indicating a modest degree of oral processing of coarser plant material. These shearing teeth were very effectjve in cutting hard branches, stems, seeds, and foliages of contemporarv floras, such as conifers, ginkgoes, cycads, ferns, and horsetails. Unlike the condition of Shunosaurus, the lvear facets in Carnardsdums are more restricted to the crown tips. The general sequence of wear in the maxillary teeth is: occlusal -+ rostral -> caudal facet. 'White (1958) Tooth Replacement Pattern. briefly discussed the tooth repiacement pattern in Camarasdzrurs. DINO 28 includes the left premaxilla and marilla rvith intact tooth rows, providing an opportunity to study the replacement pattern in detail. Because of crown-to-crown occlusion, various wear facets are present throughout the tooth rows. The morphology and wear facets of the tooth series from front to back are described here (Fig.9.a). There are four teeth in the premaxilla. Since the interdental plates are intact in CAmtrasaurus, the size and location of replacement teeth are not clearly visible as rn Shunosattrus. The first premaxillary tooth is a replacement tooth; it has erupted but not reached the occlusal level. Its crown lies below the labial margin. The crown in mediai aspect is roughly triangular with a pointed apex. From this shape, we can determine the degree and nature of wear in the following tooth series. The second tooth is fully erupted, with extensive wear. The occlusal facet is small and relatively flat. The rostral facet is moderate near the top of the crown. The caudal facet is extremely excavated with a nearly horizontai surface. The third tooth is shorter than the preceding one; it has just reached the occlusal level and the crown tip has suffered wear. The fourth functional tooth is missing, but was present in life. The replacement tooth can be observed in the caudal section that articulates with the rnaxilla. This replacement tooth is far beneath the interdental plate of the premaxilla and is impossible to see medially. The crown, compietely formed, is the same length as in the functional tooth during its initial development. The replacing tooth generally migrates to the position of the old tooth during its development. Caudally of the four premaxiilary teeth, there are ten teeth in the maxilla that show a gradual reduction of height caudally. The fifth tooth (first maxillary tooth) crown is young, with a little occlusal wearing. The sixth tooth is fully erupted and has a long root. Crown wear is so extensive that it has produced a horizontal platform. The seventh tooth is also fully functional, but the wear is not Neuroanatonrv and Dentition of Camarasdurus lentus
.
207
TABLE 9.1. Tooth morphology and measurements oI Camarasaurus
Tooth
Occlusal
facet
Rostral
facet
Caudal
facet
'Wear
stages
T
no
no
no
R3
2
yes
yes
,ves
F3
3
yes
no
no
F2
+
no
no
no
R1, F4
5
yes
no
no
F2
6
yes
r'la
nla
F5
7
yes
yes
)'es
F3
8
yes
nla
nla
F5
9
yes
no
no
F4
10
no
no
no
F1
11
yes yes
nla nla
F4
12
nla nla
13
no
11C)
F1
74
no
no
no no
F3
R2
extensive. The occlusal facet is small and the rostral moderate. The caudal facet is deeply truncated to produce a pointed tip on the
crown. The eighth tooth is probably the oldest tooth in the series and shows an extensive wear facet that forms a horizontal surface. Rostral and caudal facets have lost their identity and all are merged into a single platform. The wear surface has reached the maxrmum area. The ninth tooth is also fully functional, with a long root. The wear facets in the crown have just begun to merge. The caudal facet is sharply truncated. The tenth tooth is young with an intact crown and lacks wear. The eleventh tooth is functional, with a prominent facet on the occlusal surface. This facet is obliaue forward and more outward than those on other teeth. Rostral and caudal facets can not be identified. The twelfth tooth is smaller than the preceding with a narroq elongate occlusal facet. As in the eleventh, there are no rostral or caudal facets. The thirteenth tooth is a new replacement tooth and lacks a wear facet. The fourteenth tooth is also a replacement tooth and occupied its position after the loss of the old tooth. The tooth replacement pattern (Table 9.1) is inferred from the degree of wear and the relative height of the root. Five stages of
functional teeth (F1-F5) and three stages of replacement teeth (R1-R3) are recognized on the left maxilla, based on the tooth exposure, tooth size, length and relative position in the alveoli, and wear facet. In order of increasing age, the stages are: R1, small incipient tooth showing the tip of the crown. R2, fully erupted crown.
208
.
Sankar Chatterjee andZhongZheng
1234567A91011121314 F5
\
F4
\
F3
\
F2
\
F1
\
R3
R2
\
\
\
\
\
\ \
\
RI
Fi1.9.5, Z-spdcing diagram for Camarasaurus lentus (DINO 2B). (See Table 9.1 for rau' data.)
R3, the crown has reached the labial margin of the maxiila and is completely exposed. Similarlv. for functional teeth:
tooth is young but fully developed, with a long crown and long root, but it lacks a wear facet. F2, the crown tip is beginning to show a wear facet. F3, a wear facet is present not only on the occlusal, but also on the rostral or caudal side; however) the crown apex is still triangular. F4, the wear facet is expanded so that the apex of the crown becomes rounded. F5, three facets are merged to form a horizontal wearing F1, the
surface. Based on these stages, the Z-spacing was measured (Table 9.1).
Camarasaurzs shows a fairly well organized replacement pattern. The Z-spacing varies between 2.0 and 3.0 (Fig. 9.5). These values indicate that the replacement waves moved from back to front (Osborn 1972). The individual Zahmethen have a consistent slope. This slope becomes steep in the lower part, but the angle abruptly decreases in the last two stages. The Zahnreihen slope varies from 1 to 4 in Cantarasaurzls. In most reptiles, the Z-spacing lies in the range of 1.56 to 2.80 (DeMar 1972). The tooth replacement pattern of Camarasaarzs provides the fol lowing information:
1. The replacement series (odd and even) are from the back to front; the replacement wave direction is independent of the tooth nrorphology and tooth number, but relies on the Z-spacrng. 2. The average Z-spacing is 2.5 in Camarasdurus; the individual or u'hole Zahnreihen are highly organized. The slope between them is of slight variatron. 3. The number of tooth-wear facets strongly suggests the upper and lower teeth must occlude in alternate fashion and that the occlusion is orthal. 4. In his Camarasaunrs stud-v. \7hite (1958) observed anomalies and suggested that the replacement pattern in the odd series of Neuroanatomv and Dentition of Camarasaurus lentus
.
209
maxillary teeth is from back to front, whereas in the even series, it is from front to back. However, Z-spacing analysis gives a better picture. Using the same measurement data (see White L958, 491, table) but on the Z-spacing mapping, the replacement pattern in both series becomes back to front, as in most reptiles. Following Osborn's equation (1,972\, the average Z-spacing in Camarasaurus is 2.5 (Z = 2.5), and counting alternatively (R = 2), the replacement
wavelength should equal five teeth. This analysis contradicts White's observation. 'lfhite (1958) estimated a replacemenr wave of three, with each wave length corresponding to rwo or three teeth.
Acknowledgments. \X/e thank Kenneth Carpenter and Virginia Tidwell for inviting us to conrribute rhis paper and also for edito-
rial
assistance. This paper resulted
in part from Zhong
Zheng's
Ph.D. thesis research, conducted under the supervision of S. Chatterjee at the Museum of Texas Tech University. V/e thank Dan
Chure
of Dinosaur National Monument for the opportunity
ro
study the beautiful skull of Camarasaurus lentus. We thank Mike Nickell and Jeff Martz for the drawings. The research was supported by Texas Tech University. Appendix: Abbreviations for Figures
Braincase angular aof: antorbital fenestra ar: articular bo: basioccipital bpt: basipterygoid process bs: basisphenoid bt: basisphenoid rubera ch: choana d: dentary ec: ectopterygoid en: external naris eo: exoccipital eov: foramen for external occipital vein f: frontal fm: magnum fenestra ic: internal carotid artery idp: interdental plate j: jugal l: lacrimal ls: laterosphenoid t*r. t-.^-^l .--^oral fenestra m: maxilla n: nasal o: orbit op: opisthotic os: orbitosphenoid p: parietal Skull and an:
210 . Sankar Chatterjee andZhongZheng
popr: paroccipital pl: palatine pm: premaxilla po: postorbital ppf: post palatine fenestra pra: prearticular
prf: prefrontal pro: prootic ps: parasphenoid psf: postfrontal pt: pterygoid ptf: post temporal fenestra ptr: pterygoid ramus q: quadrate qj: quadratojugal sa: surangular snf: subnasal fenestra soc: supraoccipital sp: splenial sq: squamosal sym: symphysis
utf: upper temporal fenestra v: vo[ler Endocast cel: cerebellum cer: cerebral die: diencephalon fo: fenestra ovalis
lnt
e:
internal ear region
u, Lvr ] rr ar ^l'.r. vrr4r ^lf^-'^-".-^^+
L
op l: optic lobe pf: parietal fenestra pit: pituitary body vcm: vena cerabralis medius Cranial Nerues
IV trochlear V trigeminal \/1. ^-hth"l-i.
I: olfactory II: optic
VI: abducens VII: facial IX: glossopharyngeal X: vagus XI: spinal accessory
III: occulomotor
XII: hypoglossal
References Cited
Chatterjee, S., and Z. Zheng. 2002. Cranial anatomy of Shunosaurus, a basal sauropod dinosaur from the Middlle Jurassic of China. Zoological Journal of the Linnean Society 1,36: 1,45-1,69. DeMar, R. 1.972. Evolutionary implications of Zahnreihen. Euolution 26:
435+50. P. M. 1984. Cranial anatomy of the prosauropod dinosaur Pldteosdurus from the Knollenmergel (Middle Keuper, Upper Triassic) of
Galton,
Germany. I. Two complete skulls from Trossingen'Wurtt, with comments on the diet. Geologica et Pdlaeontologica 1,8:139-171. 1985. Cranial anatomy of the prosauropod dinosaur Plateosaurus from the Knollenmergel (Middle Keuper, Upper Triassic) of Germany. II. A1l the cranial material and details of soft-part anatomy. Geologica et P alaeontologica 19 : 119-1 59. Hopson, I. A,. 1979. Paleoneurolog.v. In C. Gans, ed., Biology of the Reptilia. Yol. 9A,39-146. London: Academic Press. Madsen, J.H., J. S. Mclntosh, and D. S. Berman. 1995. Skull and atlasaxis complex of the Upper Jurassic sauropod Camarasaurus Cope (Reptilia: Saurischia). Bulletin of the Carnegie Museum of Natural
History 31: 1-115. Mclntosh, J. S. 1990. Sauropoda. In D. B. 'Weishampel, P. Dodson, and H. Osm61ska, eds., The Dinosauria, 345-401. Berkeley: University of California Press. Osborn, J.W. 1972. New approach to Zahnreihen. Nature 225:343-346. 'S7hite, T. E. 1958. The braincase of Camarasaurus lentus (Marsh). Journdl of Paleontolology 32: 477494. \filson, J. A., and P. C. Sereno. 1998. Early evolution and higher phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology, Memoir 5: 1-68. Zheng, Z. I996. Cranial anatomy of Shunosaurus and Camarasaurus (Dinosauria: Sauropoda) and the phylogeny of the Sauropoda. Ph.D. dissertation, Texas Tech University.
Neuroanatomv ar-rd Dentition of Camarasaurus lentus
.
271,
L0. Neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs KpNr A. SrpvpNS AND J.
MrcHerr
PenRrsH
Abstract The extreme elongation of sauropod necks, some of which were 9 m long, has been used to suggest that they engaged in highly specialized feeding. This common hypothesis of brorvsing on high vegetation is examined by reconstructing the curvature of the necks of representative sauropods in the undeflected, or neutral, pose. The cervical columns of the sauropods Apdtosaurus, Brachiosaurus, Camarasaurus, Cetiosaurus, Dicrdeoscturus, Diplodocus, and Euhelopus were found to be straighr exrensions of their dorsal vertebral columns. None presented the osteological specializations for a more erect neutral pose, such as seen in the base of the giraffe and avian neck. Hence, the elevation of the head, cantilevered far anterior to the shoulders, was determined primarily bv the length of the neck and its slope at the base. All sauropods examined held their heads at or below the height of the shoulder in neutral posrure. Furthermore, most of the sauropod necks studied curved downward cranially. The ventral inclination of the skulls relative to the cervical column in diplodocids and nemegtosaurids may have been a further adaptation for downward feeding at ground level or for
grasping aquatic vegetation ar or near the surface of the r,vater. Previous studies of sauropod dentition have made a distinction between taxa rvith a full batter,v of spatulate teeth, which presumably employed some oral processing and specialized on more resistant forage, and those with a reduced battery of peg-like teeth, which may have fed predominately on softer plants or possibly were used to strip branches. The current knou.ledge ofJurassic floras suggests that the most abundant potential forage for sauropods would be found within the lor,v- to medium-browsing range thar is predicted by our cervical reconstructions.
Introduction Sauropod dinosaurs represent the extremes of both gigantism and neck elongation in the history of terrestrial vertebrares. Neck lengths were extreme in both absolute and relative measures. The necks of the Jurassic sauropods Barosdurus and Brachioslurus were about 9 m long, well over twice the length of their dorsal columns. Even the relatively short-necked Camarasaunzs, r,vith a cervical column about 3.5 m long, had a neck substantially longer than its trunk. Because of their elongate necks, massive bulk, abundance, and diversity, the feeding habits of the sauropod dinosaurs of the Jurassic period have been a subject of inquiry and dispute since relatively complete fossils of this clade were first discovered over a hundred years ago. Analysis of the functional morphology and paleoecology of sauropods has led to a dir.ersity of interpretations of their feeding habits. Sauropods have been interpreted as high browsers, low browsers, aquatic, terrestrial, bipedal, and tripodal, and they have even been restored with elephant-style proboscises. Furthermore, differences in neck length, body shape, cranial anatomlr, and dental morphology indicate significant morphological (and inferred behavioral) variation among the Sauropoda. Here rve will review various lines of evidence relating to feeding in sauropods and reconsider them in light of our own studies on neck pose, mobilit,v, and inferred feeding envelopes in Jurassic sauropods. Sauropods varied considerablv in body plan and size, resulting in a range of head heights across the different taxa, when feeding in a neutral, quadrupedai stance. Reconstructions have often differed in the depiction of a sauropod taxon in neutral pose, both in the placement of the eiements of the appendicular skeleton and the curvature of the axial skeleton. More precise determination of neurral feeding height would permit sorring sauropod raxa into a vertical range of feeding niches, follor,ved with an analysis of extrernes of neck mobi|ty and postural repertoire for more specialized forms of feeding. Dentition morphology and microwear provide additional indirect evidence of feeding preferences (e.g., Barrett 2000; Barrett and Upchurch 1994; Calvo 1994; Fiorillo 7991,1998). Evidence regarding the vegetation consumed by different sauropod taxa can then be correlated with their specific range of feeding heights.
Institutional abbreuiations. CMNH-Carneeie Museum of Neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs
.
213
Natural History, Pittsburgh, Pennsylvania; DINO-Dinosaur National Monument, Jensen, Utah; and LCM-Leicester Civic Museum, Leicester, United Kingdom.
Neutral Pose and Intrinsic Curvature along the Axial Skeleton Careful analysis of the undeflected state of sauropod necks is of central importance to understanding their feeding habits. Of all aspects of sauropod biology, perhaps the greatest divergence of opinion has concerned the curvature of the neck. The early reconstructions of most sauropods depicted the necks as cantilevered ahead of the animal, generally descending at the base due to the arch of the back (e.g., Holland 1906; Gilmore 1925,1936;Hatcher 1901; Osborn and Mook 1,927). Only a few sauropod taxa were initially reconstructed as having giraffe-like necks, with sharp upward curvature at the base (Wiman 1929;Janensch 1950b, pls. 6-8). Over the decades since their initial descriptions, however, there has been a general trend toward depicting sauropods as having ascending necks, some with necks much more steeply curved than originally depicted. For instance, Opisthocoelicdudia, a taxon for which the neck is unknown, has been rendered with a swanlike neck by default (Paul 2000,406) contrary to the original description that concluded the neck would have been horizontal or downward-curving (Borsuk-Bialynicka 1977, fig. 19). Paul (2000, 92) suggests that some sauropod necks had thick intervertebral discs, effectively wedged between successive centra, which induced an upward curve at their base. Sauropod necks, however, were strongly opisthocoelous, with central articulations that closely resemble the mammalian opisthocoelous biomechanical design, consisting of condyles that insert deeply in cotyles of matching curvature, leaving little room for cartilage. In modern quadrupeds with opisthocoelous cervicals, such as the horse, gtaffe, and rhino, the central
condyle and cotyle are separated by only a few millimeters. In avians, heterocoely is similarly associated with very precisely matching articular facets and tight intervertebral separations. Across a large range of extant vertebrates, while substantial intervertebral separations are associated with platycoelous vertebrae, vertebrae with nonplanar central articular geometry generally have little intervening cartilage (pers. obs.), and thus little room for conjecture regarding their undeflected state. Neutral deflection. The neutral state of deflection between successive vertebrae is defined geometrically by the alignment of the zygapophyses and by nulling the deflection at the central articula-
tion (Stevens and Parrish 1999). The pre- and postzvgapophyses, if present, are generally centered within their range of dorsoventral travel when the two vertebrae are in the undeflected state. Simultaneously, the central facets will be in a neutral or undeflected state. For platycoelous vertebrae, the two planar articular surfaces are parallel when undeflected, a state particularly easy to verify in lat214
.
Kent A. Stevens and
T.
Michaei Parrish
eral view. Determining the neutral position for opisthocoelous vertebrae requires closer scrutiny of the margins of the central articulation. The synovial capsule surrounding the condyle-cotyle pair at
the centrum generally exhibits circumferential attachment
scars
surrounding the condyle and cotyle. These ridges are parallel when the joint is undeflected, and especially apparent when viewing osreological mounts of extant vertebrates in lateral aspect. Note that
the gap across these margins at the centrum is necessarily wider than the actual intervertebral separation deep within the ball and socket in order to accommodate the displacement of the cotyle during mediolateral and dorsoventral deflection.
The intrinsic curvature of the vertebral column for a given taxon can be determined by placing successive elements in neutral deflection. This procedure can be performed using photographs or engravings in lateral view (see below), provided the illustrations are of verified dimensional accuracy. Whereas two-dimensional analysis is sufficient to establish the neutral pose along a vertebral column, a three-dimensional reconstruction is required to estimate the range of motion and curvature achievable (Stevens and Parrish 1996, 1999; Stevens 2002; Stevens and Parrish in press; Stevens in prep.). There is consistency between the geometrically defined neutral posture and the pose habitually held by the behaving animal, determined by direct manipulation of the cervical vertebral columns of a variety of extant vertebrates. For example, the neutral pose reveals the sigmoid curvature characteristic of avian and equine necks, the catenary shape of the camel's neck, and the sharp upturn at the base of the otherwise straight giraffe neck (see Fig. 10.1). The giraffe neck is particularly relevant ro the reconstruction of some sauropod necks, owing to the historical and persisting interpretation of some sauropods as giraffe analogues, especially as regards the presumed upturn at the base of the neck. The adult giraffe neck is sharply angled at its base while held in the undeflected, neutral position (Stevens and Parrish in press, fig. 1).This elevation arises not from deflection at the intervertebral joints, but from keystone-shaped cervicothoracic vertebrae, the most wedge-shaped being C7 in giraffe.'With no known exception, the curvature characteristic of the axial skeleton of a given vertebrate arises, not from chronic flexion out of the neutral position, but from the morphology of the vertebrae in the undeflected state.
Neutral Posture of the Presacral Axial Skeleton For a number of well-preserved sauropods, the original descriptions provided accurate illustrations of the vertebrae, often as steel engravings based on photographs taken of the prepared vertebrae prior to mounting. The individual lateral views provide a valuable resource for reconstructing the neutral posture of their axial skeletons (Stevens in prep.). For example, Figure 10.2 shows a digital composite of the individual steel engravings of the presacrals of DlNeck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs
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215
Fig. 1 0.1 . Extant uertebrates tend to l:abitLtally hold their necks in d neiltrdl stdte of deflection. The characteristic cdtendr,y shape of Il e c.tntcl neck tA1 and tbe ot ian sigtnoid neck (domestic turkey, B) is tntluced by ker*stone-shaped t' e rte br ae. Keystone- sh ap ed centra are also found in non-auian theropod dinosaurs, but haue not
bte,t,th sert'ed i n
s,t u
ropod
s.
216 . Kent A. Stevens and J. Michael Parrish
:l ,l , ,l
crdeosaurus hansemanni (from Janensch 1,929a, pl. 1). The individual images were adjusted for scale, then rotated and translated into neutral deflection using the layering option in PhotoshoprN{. The opacity of each layer was decreased to make the vertebrae partially transparent. The composite image thus reveals the insertion of the
central condyle within cotyle, and the centering and superposition of the zygapophyses. The dorsal column of Dicraeosaurus is distinctly arched, but the cervicodorsal transition is straight, as we have found in other sauropods. The neck is gently curved ventrally, a droop also observed in digital composites of the diplodocids Apatosaurus louisae (Fig. 10.5) and Diplodocus carnegii (Stevens in prep.) and in some other sauropods including Brachiosaurus brancai (see below) and Cetiosaurus (Fig. 10.3A). This technique, using illustrations of the original material, can be used to revise the interpretation of the seemingly giraffe-like sauropods. For instance, Euhelopus zdanskyi (lX/iman L929; Fig. 10.3B) was depicted with a neck ascending at about 38' from the horizontal; in subsequent reconstructions this slope increased to about 65' (Mclntosh et aL.7997,Fig.20.9; Paul 2000, appendix A). The remarkable linearity in the neck from C1 to C16 (\fiman 7929, pl.3) in fact extends through the cervicodorsal region when
Fig. 1 0.2. Dicraeosaurus hansemanni presacral uertebral column reconstruction in neutral pctsition, a composite of the p r e s a cr a I u erte b r d e indiu idual ly figured in Janensch (1929, pl.1). lnset: superposition uf compusite onto reconstruction in Janensch (192e, p1. 1 6).
Neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs
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217
":""dplrlr *"}9"'
/-\tr-4sj - /t)a1i-_
Fig.
1
0.3. Digital reconst/uctions
of tbe neutral pose of the necks of tbree sauropods ftrom Steuens tin
prep.). (A) Cetiosaurus /lCM C468.1968) is shoun in neurdl
pose by compositing the ceruical u er t e b r ae indiu idually illustr ate d b1, John Martin. (B) Euhelopus zdanskyi (from'V{iman 1929, pl. 3), with C1.7 and D1 rotated
digitally to remoue the postmortem " death pose" dor siflex ion. /C/ Brachiosaurus brancai specimen SII neutral pose composite of ceruicals C3-D2 (from Janensch 1950a, figs. 32-19). The original ,ndterial shows none of the giraffe-like keystone shape depicted in Mclntosb et al. (1997, fr7. 20.16) eleuated neck in neutral positiun
shuwn) (sec Steuens 2002. fig. 70.2; Steuens and Parrish in press).
218
.
Kent A. Stevens and
T.
care is taken to remove the postmortem dorsiflexion "death pose" posterior to C17, as shown in Figure 10.3B (Stevens and Parrish in press; Stevens in prep.). Eubelopus was apparently a low browser, not a "Juraffe." Death-pose dorsiflexion was also responsible for the swanneck pose of the juvenrle Camarasdurus lentus (Gilmore 1,925, pl.
14). The postzygapophyses are in fact displaced posteriorly far from the neutral position, with many completely out of articulation (Parrish and Stevens 1998). The posterior cervicals and anterior dorsals show no evidence of the wedge shape needed to induce curvature (Osborn and Mook 1921, pI. 68, DINO 28; CM 11338; CM 11069). Despite the popular depiction of Camarasaurus with a sharply upturned neck, the original reconstruction (Fig. 10.4) showing the cervicodorsal transition as horizontal and linear is consistent with recent mounts of actual fossil material (e.g., at the 'Wyoming Dinosaur Center and "Annabelle" at the Natural History Museum, University of Kansas). Similarly, Brachiosaurus brancai was originally illustrated (and mounted) with a giraffe-like ascending neck (Janensch 1950b, pls. 6-8), by providing the last few cervical vertebrae and the first dorsal vertebra with distinctly wedge-shaped centra (Stevens 2002, figs. 2-3). Some subsequent reconstructions in fact depict the neck as nearly vertical (Mclntosh et al. 1.997, fig.20.16; Paul 1988, 2000, appendix A), and arguments have been presented in support of this dramatic interpretation (Christian and Heinrich 1998; but cf. Czerkas and Czerkas 1991. \32: Martin et al. 1998). The neuMichael Parrish
tral pose of the neck can be reconstructed in Figure 10.3C (from Stevens in prep.) by compositing the original steel engravings from Janensch (7950a, figs. 32-49) in neutral deflection between each successive pair of vertebrae. The result is a very gentle, downward-
curving neck extending from a straight cervicodorsal transition. The centra at the base of the neck show no evidence to suggest this sauropod had a giraffe-like elevated neck. In particular, the centra of the vertebrae from C10 to D2, which were found articulated within a single block, are spool-shaped, not wedge-shaped, and their resulting neutral pose is straight, not ascending (Stevens in prep.). Again, as in some other sauropods, the anterior cervicals of Brachiosaurus cLtve downward in neutral position. This droop is likely important in orienting the head ventrally in support of downward feeding (see below).
Fig. 10.4. Original Camarasaurus reconstruction from Osborn and Mook (1921 , fig. 28) showing an
entially str aigh t c eru ico dor s al transition, t,ith no trace of the
ess
gir affe-
li
ke,
ne ck- ele u atio n
adaptation figured in more recent p opular re constructions,
Skeletal Reconstructions The acetabulum can be regarded as the fulcrum about which the
axial skeleton would pivot, according to differing estimations of glenoid and acetabular height and the placement of the pectoral girdles upon the ribcage. Amongst sauropod taxa limle variation is apparent in the basic design of the hindlimbs, and reconstrucrions for a standing posture differ only marginally. Sauropod forelimbs show more variability across reconstructions in the articulation of the digitigrade manus, the degrees of elbow flexion (Christian et al. 1999), and the orientation of insertion of the humerus into the glenoid fossa. For a given neck reconstruction, the two factors having the greatest effect on head height are the degree of arch to the back and the placement of the pectoral girdles. A digital model of ApAtosdurus, created using DinoMorphr\{, will illustrate. The neck is held constant in neutral deflection based on the composite in Figure 10.5, whereas the arch to the back and the placement of the pectoral girdles is varied. The low arch condition is consistent with that in Gilmore (7936, pl. 3a) and Vilson and Sereno (1998, foldout 1). The high arch condition and pectoral girdle orientation approximates that in Mclntosh et al. (1997, fig.20.12) and Paul (2000, appendix A). Neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs
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219
lt
Fig. 10.5. The presacral uertebral column of Apatosaurus louisae
rirotn Cl to D9) in neutral ion, re constructed by ,l i g it a I ly comp o siting indiu idual
p os it
i
I I
tr str ations
pl. 21-25).
from
G
ilmor e
(
19 3 6,
The similarly posed DuroMorphrM model will be used
:,) tllustrdte abernatiue trunk :,tierpretdtions (also see Fig.
.'.61.
Feeding enuelopes and inferred browsing heights. A "feeding envelope" is the range of head positions that can be reached by a tetrapod standing in one place and simply moving its neck relative to its body. Such an envelope might be estimated from the range of motion along the neck (Martin 1987, fig. 3; Stevens and Parrish 1,999). The assumption of this approach is that the undeflecred or neutral pose approximates the center of the feeding envelope for eacn taxon. Martin (1,987) estimated a curved feeding envelope for Cetiosaurws approximately 4.5 m wide by 3.5 m above ground level, based on a reconstruction in which the base of the neck slopes slightly downward at the shoulder. In an earlier study of ours (Stevens and Parrish 1999), the longer necks of Apatosaurws and Diplodocus were estimated to sweep through a lateral arc about 8 m wide, and surprisingly, to permit reaching dor,vnward below ground level, an adaptation perhaps related to aquatic feeding. Fig-
ure 10.7 shows the range of dorsoventral deflection for Ap-
atosdurus and Diplodocws. The dorsal flexibility of Apatosaurus, 6 m, was somewhat greater than that of Diplodocus, 4 m) attributable primarily to the larger zygapophyses at the base of the neck of Apatosaurus. Both were capable of low to moderately high browstnq
Figure 10.8 shows Brachiosdwrws brdncai (SII specimen) mod-
eled from quantitative data in Janensch (1929b, 1935-1936, 1950a, 1950b), with the neck in the neutral pose shown in Figure 10.3C. While the range of dorsoventral movements cannot be estimated due to the lack of preservation of the neutral arches, the head would reach over 9 m above ground level with a modest dorsiflexion of approximately 3" per joint, and could reach ground
.
Kent A. Stevens and J. Michael Parrish
Art
t $-lJ**{#
i,t
rl
,J$i
level (without requiring a giraffe-like splay of the forelimbs to drink) by ventriflexion of slightly less than 8' per joint proximally' It is not necessary to postulate osteological adaptations, such as wedge-shaped centra, for Brachiosaurus to have reached remarkable heights and to achieve a huge feeding envelope, even if it had negligible ability to elevate the neck above its neutral pose (for muscular or cardiovascular reasons). Sauropod Dentition The study of feeding modes in sauropods extends beyond the esti'We will now briefly review inferences mation of cervical positions. skull structure' plant distribudentition, drawn from studies of
Fig. 10.6. DinoMorPhrv re
constru ct i ons illu str ating th e
uariation in head height resulling front ttuo interpretations of tbe body plan o/ Apltosaurus louisae. The neck is held constant in the neutrdl position shown in Figure 10.5. The low dorsal arch condition corresponds to the neutral pose (Fig. 10.5). The higb dorsal arch dnd steePel Placement of tbe pectoral girdles lsee insetst correspctnds to that in Mclntosh et al. (1997, fig. 12; also see Paul
2000).
Neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs
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221
t
{
4" .,,1,r
ltliiUil
Fig. 10.7. DinoMorpbr\ models
o/Apatosaurus loursae (A) and Diplodocus carnegii (B) presaoal axial skeletons in neutral pose plus lou-contrast auerlay of the extremes of dorsal dnd uentrdl flexion (Steuens and Parrish 1999).
tions, and previous analyses of neck posirions and discuss how our models impact previously proposed models of sauropod feeding. The basal members of all dinosaur lineages for which an her-
bivorous diet is generally inferred (Sauropodomorpha and Ornithischia) share the same basic tooth-form, consisting of a leaflike shape featuring an expanded crown and a serrated row of denticles occurring along the ridge dividing the labial and lingual surfaces of
the tooth. In Sauropodomorpha, the leaf-shaped form predominates in prosauropods, particularly if one acceprs Barrerr's (1999, 2000) reassignment to the Sauropoda of the blunt teeth originally designated by Simmons (1965) as belonging to the prosauropod Yunnanosaurus.Yates and Kitching's recent (2003) analysis of Triassic sauropodomorphs has placed several taxa formerly consid222 . Kent A.
Stevens and T. Michaei Parrish
#
s
of a monophyletic Prosauropoda inside of the sauropod lineage, including Melanorosaurus (but see Galton et al', this volered part
ume) and Anchisaurus.
The taxonomic reassessment of Anchisaurus, which is the most basal sauropod in Yates and Kitching s (2003) phylogeny, is significant because, unlike the other Triassic and Lower Jurassic sauropods, Anchisaurus is well represented by dental and cranial material. The teeth of Anchisdurus are leaf-shaped, serrated, and recurved medially (Galton 7976). Dentition among other basal sauropods is represented by isolated teeth of the Early Jurassic genera Barapaslsaurus and Kotasaurus (Yadagiri 1988). Both possess
Fig. 10.8. DinoMorPhr\t model Brachiosaurus brancar with ceruical uertebral column in neutral pose (see Fig. 10.3, C).
of
coarse denticles and exhibit the expanded spoon-shaped and lingually concave crown pattern that is characteristic of most nondiplodocid sauropods. Similar teeth are present in members of the Chinese sauropod clade Euhelopodidae, although some variation occurs in the size and distributions of denticles, which are absent altogether in Euhelopu.s. No sauropod teeth are serrated, other than those of Barapasawrus, Kotlsaurus, euhelopodids, and some unworn examples of the Tendaguru Brachiosaurzs. The teeth of the Middle Jurassic sauropod Patagosaurus are similar in shape to those of Euhelopodidae (Bonaparte 1986). Camarasaurus teeth are well known, and are similar in basic shape to those in Patagosaurus and euhelopidids, although the expansion of the crowns relative to the tooth base is less pronounced, as is the concavity of the lingual surface of the teeth (Madsen et al. 1995). The teeth of Brachiosaurus share the general spatulate configuration with Vulcanodon, Euhelopodidae, and Camarasarurus (Janensch 1935-1,936). Denticles are reported in some unworn Brachiosaurus teeth (Janensch 1935-1936) but are not visible in worn teeth. In contrast to those of Camarasaurus, the crowns of Brachiosaurus teeth exhibit minimal expansion relative to the base. The teeth of Diplodocidae and Titanosauridae are both nearly circular in diameter, without any expansion of the crowns' In both families, the crowns taper gently to a point in the unworn condiNeck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs
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223
tion, but form planar occlusal surfaces when worn (Holland 1924; Barrett and Upchurch 1994; Curry Rogers and Forster 2001). Dental macroweAr.'Wear facets are absent in the teeth of An_ chisaurus, Bardpasdurus and Kolasaurus, but a varietv of wear facets are apparent in other sauropods for which dentition rs known. In the euhelopodids Omeisaurus and Shunosaurus, srepshaped wear facets occur on the cranial and caudal margins of the teeth, which appear to be the result of significant tooth-tooth wear (Upchurch and Barrer, 2000), with the greatest amount of wear on the cranial facet. No such wear is apparent in the skull of Mamenchisaurus sinocanadorzru (Russell and Zheng 1993). Step-like tooth wear is also evident in Patagosawrzs (Bonaparte 19g6i. Sig_ nificant concave wear facets are also visible o.t .ith.. side of the apices of the teeth rn Camarasaurus (Madsen et al. 1995), although here the amount of wear is more symmetrical than in patagosdurus and the euhelopodids.
In Brachiosaurus, small amounts of wear are observed, but generally on the lingual and labial sides of the crown rather than on the cranial and caudal margins. As in diplodocines and titanosaurs, this has been interpreted as evidence of tooth-to-tooth occlusron, rather than interdigitation of upper and lower teeth. In titanosaurs and diplodocines, this type of occlusion produces high-angle wear facets that resemble the point of a chisel (Fiorillo 1998; Curry Rogers and Forster 2001; Upchurch and Barrett 2000). Dental microwear. In studies of the teeth of mammals, and par_ ticularly those of fossil primates, dental microwear has been studied via scanning elecrron microscopy as a method of inferring diet in extinct vertebrates. The logic behind this approach is that different food types will create differenr, and distinctive, striations on the enamel of herbivore teeth that may be indicative of diet. This approach has been applied to sauropods by Fiorillo (1991,799g), Calvo (1994) and Barrett and Upchurch (1994, IggS), although studies to date have focused only on the teeth of camarasaurus (Fiorillo 1991, 1998), Diplodoczs (Fiorillo 199I, 1999; Calvo 1994; Upchurch and Barret 2000), and the titanosaurid Rabeto_
sdurus (Upchurch and Barrett 2000). All studies of diplodocid teeth showed labiolingual scratches across the wear facets, whereas the studies of camarasaurus indicated both pits and scratches in adult teeth (calvo 1994; Fiorlllo 1998; Upchurch and Barrett 2000). Fiorillo (199I) interpreted the absence of pits in juvenile camarasawrzs teeth as evidenie for ontongenetic switching of diets. Upchurch and Barrett's (2000) study of one Rapetosauru.s tooth indicated both coarse scrarches and prtting on the wear surface.
Cranial Characters Plesiomorphicalll',
the skulls of sauropods resemble those of
prosauropods such as Plateosauru.s (Huene 1926;Galton 1984). In the most basal sauropods for which relatively complete skulls are
.
Kent A. Stevens and J. Michael Parrish
known-for example, Ancbisdurus, Shunosaurus, and Omeisdurus (the latter two of which are either basal Euhelopodidae [in Upchurch 19981 or basal Sauropoda ['Wilson 2002] in the two most recent, comprehensive phvlogenetic analyses of sauropods)-the skull is essentially convex in anterodorsal profile, with a modest snout.
lnclination of tbe skull. Because of its presence in Euhelopodidae, Camarasaurus, Brachiosauridae, and sauropod outgroups, the plesiomorphic pattern for sauropod cranial inclination appears to be one with the tooth row positioned horizontally relative to the long aris of the brain cavity extending from the foramen magnum into the braincase. In Diplodocidae, Nemegtosauridae, and the Titanosauridae for which cranial material is known, the tooth row is inclined cranioventrally relative to this axis, such that the head would naturally tilt dorvnward in a neutral position (here defined as the situation where the long axis of the brainstem cavity and the neural canal of the atlas/aris are horizontal). Fiorillo (1998) noted these differences when comparing Camarasaurzs with Diplodocus, interpreting the nearly 90' angulation of the head relative to the neck in Diplodocus as an indication that it might have had a more erect vertical neck than that of Camarasaurzs. Howet'er, the alternate interpretation, that the head was directed more ventrally in Diplodocus to facilitate low browsing' seerns equally plausible. The diplodocids Apatosaurus and Diplodocus had sufficient neck flexibility ventrally to reach far below ground level (Stevens and Parrish 1,999), a capability consistent with lacustrine feeding. Taken in conjunction with the presence of prognathous, peglike cropping or sieving dentition, dorsally placed nostrils, and a ventrally trending neutral position for tl-re cervical column, the dor,vnward curvature of the head could have sen'ed as a means of grazing on or under the surface of the water while maintaining visual and olfactory vigilance. The absence of these features in Cdmarasaurus and Bracbiosaurus would be consistent with a more generalized feeding envelope for these genera.
Configuration of dentition and role of iaws in food processing' The basal arrangement of dentition in Sauropoda is not dissimilar from the condition that is plesiomorphic for Sauropodomorpha and Dinosauria, consisting of an essentially isodont array of teeth that projected from most of the ventral surfaces of the maxillae and premaxillae without any diastema. The teeth are either mildly prognathous or essentially perpendicular to the long axis of the tooth row, and the plane defined by the bases of the teeth is parallel to that of the horizontal long axis of the braincase. The cranial end of the dentarf is convex upward in Anchisaurzs (Galton 1976), Plateosdurus (Gaiton 1984), and Diplodocidae (Hatcher 1901), so the possibility exists that the everted lower jarv is a piesiomorphic feature for Sauropoda and reversed in lineages such as the Euhelopodidae and Titanosauroidea.
In
Omeisaurus, Mdntenchisaurus, and within the Diplodo-
coidea and Titanosauroidea, the dentition is restricted to the front Neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs
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of the jaws and, particularly within the Diplodocinae, the teeth are strongly prognathous, such that the teeth could have served only to
collect a mouthful of vegetation by nipping, raking, or sieving, rather than to facilitate extensive oral processing of the fodder. By comparison, the condition in the remaining sauropods, with expanded crowns, interdigitation of the teeth, and a more extensive dental battery, would potentially have facilitated more masticarion.
History of Inferences of the Use of Sauropod Necks in Feeding The notion that sauropods used their necks to achieve a significant lateral sweep can be traced back to Hay (1908). The concept of sauropods as low browsers has persisted for some taxa over the years. The idea of sauropods-as-molluscivores was first proposed by Holland (1,924), who believed that the blunt, prognathous den-
tition of Diplodocus could have been utilized to crack
open
unionid bivalves. Haas (1963), in his study of diplodocid jaw musculature, inferred Diplodocus was an aquatic filter feeder, specializing on floating crustaceans and/or mollusks. Both visualized the long neck as an adaptation for sweeping the head through a broad lateral arc without moving the body'. Alexander (1985) restored the
neck of Diplodocus in an essentially horizontal orientation, contending that the cervical musculature would have been insufficient to allow the neck to be raised significantly, and suggesting that a Iarge nuchal ligament would have been instrumental in maintaining the neck in a horizontal orientation. Martin (1987) manually articulated the neck of the Leicester specimen of Cetiosaurlrs, and concluded that the neurral position for its neck was near horizontal, with a slight downward curvature (see also figure 10.3A). Martin envisioned the neck of Cetiosaurzs as primarily an adaptation fa-
cilitating alateral sweep of the head. Dodson (1990) cited the broad, vertical feeding ranges made possible by the elongate necks of sauropods, and suggested that neck length and mobility might facilitate niche partitioning of different genera. Barrett and Upchurch (1994) proposed that Diplodocus might have served as both a high browser and a low browser, stripping vegetation in the high browse by pulling stems through its tooth comb. They cite the different types of wear observed on upper and lower teeth as evidence for these two types of feeding, and suggested that propalinal scratches on the teeth might be an artifact of branch stripping during high browsing. They held that the greatest amount of mobility in the cervical vertebrar column of Diplodocus was in the most cranial vertebrae, and that this flexibility close to the head facilitated their branch stripping mechanism. In a subsequenr review of sauropod feeding mechanisms, Upchurch and Barrett (2000) suggested that vulcanodontids, most euhelopodids, brachiosaurs, cetiosaurs, Camdraslurus, and Brachiosaurus were high browsers, whereas Shunosauru.s and the Dicraeosauridae were low browsers. 226
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Kent A. Stevens and
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Michael Parrish
Martin et al. (1998) proposed that sauropod necks were held essentially horizontally, and suggested that the cervical ribs served as a ventral compressive member that, along with the dorsal nuchal ligament, would have held the neck as a segmented, flexible horizontal beam. They identified Dicraeosaurus and Apatosaurws as taxa that were predominately dorsally braced, and Euhelopodidae (sensu Upchurch 1998), Brachiosaurus, and Camarasaurus as taxa that were braced more ventrally. Jurassic Plant Communities and Implications for Sauropod Feeding Globally, Jurassic floras are dominated by herbaceous piants and small trees, most significantly bennettitalean cycadeoids (tree ferns), ferns, horsetails, cycads, and ginkgoes (Behrensmeyer et al. 1992; Coe et al. 1987). The Morrison Formation of the western United States and the Tendaguru Formation of Tanzania represent the two major accumulations of Late Jurassic sauropod fossils. The Jurassic climates of both regions have been interpreted as strongly seasonal (Russell et al. 1980; Dodson et al. 1980; J. T. Parrish et al. in press). Paleoclimate modeling based on biome distributions (Rees et al. 7999) interpreted both regions as "winterwet." The more thoroughly studied of the two formations, the Morrison has most recently been interpreted as savanna-like, dominated by herbaceous vegetation and traversed by large, everflowing rivers along which the greatest concentrations of trees would have occurred (J. T. Parrish et al. in press), although some other recent studies interpret the Morrison as a whole as more humid (e.g., Tid-
well et al. 1998). Inferred sawropod diets. Because of the massive bulk of sauropods, most studies have assumed that their primary food source would be both highly nutritious and abundant (Weaver 1983; Farlow 1987). 'Weaver (1983) measured the caloric densities of extant members of plant groups that were abundant in the Late Jurassic, and reported a range of wet weights of 0.97-2.89 kcaUg for the various herbaceous and arborescent groups, with the highest values yielded for cycads and conifers, somewhat lower values for ferns and ginkgoes, and the lowest values for horsetails. On the basis of her analysis, 'Weaver concluded that endothermy in Brachiosaurus was unlikely because the relatively low caloric content of Jurassic plants and the sauropod's small mouth relative to body size would preclude sufficiently rapid intake to maintain an elevated endothermic metabolism.
Krassilov (1981) suggested a diet of ferns and horsetails for Diplodocids and cycads and shrubs for camarasaurids, hypothesizing that the retraction of the nares in diplodocids was an adaptation for breathing while obtaining forage underwater. Dodson (1990), utilizing arguments of their abundance in Jurassic landscapes, cited ferns as the most likely candidate for a predominant sauropod food source, but also noted that these giant herbivores Neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs
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were not likely to have been specialists in particular plant types. Fiorilio (1998) suggested that micror,vear patterns favored an inrerpretation of Diplodocas specializing on cycads, whlIe Camdrasaurus might have specialized on ginkgoes. Chin and Kirkland (1998) described what appear to be herbivorous dinosaur coprolites from the Mygatt-Moore Quarry of the Morrison Formation. Although determination of the taxonomic identity of the dinosaurs producing the coprolites is problematic, they do include significant components (ranging from 8To to 52"/") of organic matte! the identifiable components of which include woody tissue (5-147"), cuticle (0-8%), and seeds (0-6%). Taxa represented include cycadophytes, ferns, and conifers. J. T. Parrish et ai. (in press) cite the presence of significant detrital matter in these coprolites as evidence for low browsing, although both the taxonomic uncertainty of the dinosaurs involved and the possibility of taphonomic disturbance of the coprolites makes direct inference of sauropod diets from these structures highly speculative. Combining the current state of knowledge of the paleoecology
of the Morrison Formation and Tendaguru with our reconstructions of the feeding envelopes of Late Jurassic sauropods leads to
the foliowing conclusions: 1. At least in the Morrison, the greatesr abundance of trees were found along the riparian corridors, and herbaceous floras dominated elsewhere. 2. Feeding envelopes of the principal Late Jurassic sauropods overlapped broadly', with dipiodocids, euhelopodids, and dicraeosaurids clearly earmarked as low browsers with the potential for a broad lateral sweep of their necks. Camdrasaurus and Brdchiosaurus both had straight necks that appear to have pointed slightly downward in the neutral position, but the fleribility of the neck in Cdmarasaunts and the height of the base of the neck in Brachiosaunzs indicate that these taxa would have been capable of high as well as low browsing. 3. Studies of craniai morphology, gross toorh shape, and den-
tal microwear indicate that the
narrow-toothed sauropods
(diplodocids, nemegtosaurs, and at least some titanosaurs and euhelopodids) predominately fed by cropping relatively soft vegetation and/or by straining planktonic plants and animals. The broadtoothed forms (Cantarasaurus, Brachiosaurus, and potentially vulcanodontids and cetiosaurs) apparently fed on more durable plant material, including cycads and perhaps conifers. 4. The vertical feeding envelopes of Jurassic sauropods overlapped broadly, suggesting that feeding height alone rvas not a predominant mode of niche parritioning among the abundant and speciose sauropods of the Morrison and Tendaguru.
Conclusions Varying patterns of dentai morphology, cranial anatomy, cervical design, and appendicular specialization indicate that sauropods
228
.
Kent A. Stevens and I. Michael Parrish
similarly differed in their modes of feeding. Reconstructions of the neutral position of the vertebral column for six well-known Jurassic and Cretaceous sauropods (Apatosaurws, Brachiosdurus, Camarasaurus, Dicraeosaurus, Diplodocus, and Euhelopus) indicate that all of these taxa had necks that were inclined slightlv downward in
the undeflected position. Morphological evidence for the nearvertical inclination of sauropod necks favored by some contemporary restorations of sauropods (such as rrapezoidal-shaped cranial dorsals or caudal cervicals, indicators of thick intervertebral discs or other adaptations to create neck elevation) were not observed in any taxa analyzed for this study. Acknowledgments. For access
to material, the authors are
grateful to Dave Berman, Mike Brett-Surman, Don Burge, Kenneth Carpente! Mary Dawson, Jim Madsen, Mark Norell, Ken Stadtman, and David Unwin. The authors are grateful to many of their colleagues, including Paul Barrett, David Berman, Matt Bonnan, Kenneth Carpenter, Peter Dodson, John Hutchinson, Jack McIntosh, Kevin Padian, Greg Paul, Paul Sereno, Paul Upchurch, Matt Wedel, Jeff \X/ilson, and Fred Ziegler for fruitful discussions on sauropod anatomy, phylogeny, and paleoecology. Judy Parrish, A1Iister Rees, Bob Spicer, and Fred Ziegler provided helpful perspectives on Jurassic and Cretaceous floras and paleoclimates. Matt 'Wedel provided a meticulous and helpful review. Philip Platt very kindly provided access to the dimensional drawings he has painstakingly compiled of Apatosaurus louisae and assisted us on issues of the reconstruction of the appendicuiar skeleton. Thanks to John Martin for the illustrations of the cervicals of Cetiosaurus. Eric Wills assisted in the software development for the DinoMorphrM project. Matt Bonnan, Phil Senter, and David Allen assisted in dissections, research, and specimen analysis. This research was supported by NSF Grant G1A-62082, as well as by Northern Illinois University and the University of Oregon.
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1525: 1753-17-58.
232 . Kent A.
Stevens
and
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Michael Parrish
of London,
Series
B, Biological Sciences 270, no.
1"
1. Neck Posture of Sauropods
Determined Using Radiological Imaging to Reveal ThreeDimensional Structure of Cervical Vertebrae Devro S. BennAN AND Bnucp M. RotrscHrlD
Abstract Two types of sauropod cervical cenrra are distinguished based not only on external features, but also on internal features revealed through a modified method of computerized tomographic X-rays, with three-dimensional reconstructions. Using external morphology the two types of cervical cenrra are: (1) a robust type that is short relative to its width, does not become strongly waisted or narrower at its midlength, and lacks prominent ridge-like buttresses; and (2) a gracile type that is long relative to its widrh, becomes strongly waisted or narrower lateraliy and ventrally toward its midlength, and possesses prominent, ridge-like buttresses. Of the seven different sauropods whose cervical centra were studied, those of Camarasaurus and an unidentified titanosaurid exhibit the robust-type morphology, whereas those of Diplodocus, Ap at
o s auru
s, H ap I o c anth
o
s
auru s,
B dr o
s
auru
s, and
B r a cb io
s
duru s
exhibit the gracile-type morphology. Three-dimensional, radiological images of the cervical centra of Diplodocus and Camarasaurus reveal that the robust and gracile types of centra each possess a distinct structural design based on the distribution parterns and relaL-) -)
tive abundances of the compact and cancellous bone. Functional stress analyses of the structural designs of the gracile and robust centra types are proposed based on an analogy of the neck as a cantilevered beam. On this basis we conclude that the robust-type cen-
trum supported a neck held in a vertical, or near-vertical, pose, whereas the gracile-type centrum supported a neck held in a horizontal, or near-horizontal, pose.
Introduction Essential to a full understanding of the functional design of skeletal
elements is a detailed knowledge of the three-dimensional structure, which includes the distributions, patterns, and relative abundances of the different types of bone. \7ith the advent of newer and more refined radiological instruments and the accessibility of those instruments to a wider range of researchers, such data is now more easily realized. This sort of approach was important in providing a possible functional and behavioral explanation for the fusion of caudal vertebrae in certain Jurassic sauropod dinosaurs, which was the result of ossification of ligaments laterally spanning consecutive
centra (Rothschild and Berman 1991). The goal of the present paper is to explore the potential of three-dimensional, radiological imaging in identifying major stress patterns of skeletal bone as a function of the distribution patterns and relative abundances of the two basic types of bone, compact (or laminar) and cancellous (or trabecular).
For any major, supportive skeletal element in which strong gravitational or mechanical forces must be overcome) structural design can usually be explained in terms of maximum strength attained with a minimum cost in weight (Alexander et aL. 1979). 'With this simple principle as a guide to the structural design of a bone, the much denser, heavier, and stronger compact bone should be present in relatively greater amounts only where resistance to
concentrated mechanical forces is most critical. The effect of mechanical stress on the distribution patterns and relative abundances of compact and cancellous bone in a limb bone, such as a femur, has become the standard textbook example, because of the ease by which the phenomenon can be demonstrated using histologic sec-
tions and routine X-rays (Rockoff et al. 1969; Mow and Hayes 1991; Einhornl9961' Carter and Hayes 1997). Undoubtedly, other skeletal elements have been excluded (e.g., cervical vertebrae) from this sort of investigation because of their complex structure. A major challenge has been the mathematical complerities of trying to describe vertebral structure (Hannson et al. 1.987;. Panjabi et al. 1991). A new technique of determining the major distribution patterns and relative abundances of compact and cancellous bone in an element is introduced here, which employs an advanced technique in radiological imaging that produces three-dimensional images. This was accomplished using computerized axial tomography
(CT), which permits the application of post-scanning density win-
234
.
David S. Berman and Bruce M. Rothschild
dows (ranges of sensitivity). An important advantage of this technique is that it eliminates confusion with pleurocoels, which have been well described (Longman 1933; Janensch 1.947,1950; Wedel 2003). Radiological imaging, therefore, provides an indirect means of studying the mechanical stress forces in elements having com-
plex morphologies without physically altering (e.g., sectioning) tnem.
In order to explore the potential of radiological imaging in identifying the major patterns of structural stresses in skeletal elements, the centra of cervical vertebrae of sauropod dinosaurs were selected for two important reasons. First, it is presumed that the long, heavy necks of the sauropods undoubtedly sublected the cervical vertebrae to considerabie gravitational force. If it is also accepted that the cervical centra were subjected primarily to a single, one-dimensional force, the downward bending of the neck due to gravitation, this should manifest itself in an obvious emphasis of compact bone distributed in a precise pattern. Admittedly, the nuchal ligament undoubtedly played an important role in supporting the neck, but only to lessen the magnitude without altering the primary direction of the gravitational force (Francots 7975; Wedel and Sanders 1999). and therefore need not be considered further as affecting the stress analysis presented here. In addition, muscles attaching to the cervical ribs are discounted as contributing to neck support. Ratheq as suggested by }Tedel and Sanders (1999), the principal muscle attaching to the ribs of sauropods was probably homologous to the M. longus colli ventralis in birds and therefore provided for lateral movements of the neck. The second reason for using sauropod cervical vertebrae in this study was the hope of offering an additional line of evidence in resolving the long, historical, and continuing speculation or debate regarding sauropod neck posture (Coombs 19751'Martin1987; Paul 1988, 1998; Chatterjee and Zheng 7997; Frey and Martin 1997; Chrrstian and Heinrich 1998; Martin et al. 1998; Wedel2003). Materials and Methods The characterization of mid-cervical sauropod vertebrae using gross, external features (Table 11.1) was based on examination of the following list of specimens, with the total number of vertebrae examined included parenthetically Apatosaarrzs, AMNH 460, CM 3390, FMNH7163, (78); Barosaurus, CM 1198 and 11984, (5); Brachiosauras, FMNH p25107, (3). Although the cervical verrebrae of FMNH p25707, the holotype of B. altithorax, are entirely plaster, they were considered suitable for this study with regard to external morphology, because they were accurately modeled after
the holotype of
Bracbiosaurus brancai at the Museum fiir Naturkunde der Humboldt Universitdt, Germany; Camarasaurus, AMNH 5761,BYU 9047 and 5604, CM 17069 and 11338, KU 729776, USNM 15492,I7DC BS1, YPM 1905 and 1910, (25); Diplodocus, AMNH 223 and 608, CM 94, DMNH 1494, USMN Neck Posture of Sauropods Determined Using Radiological Imaging
. l,lJ
Table 11.1 Correlation between Gracile and Robust Proportions with Presence or Absence of Buttressing (Transverse Central Buttress) in Sauropod Cervical Vertebrae
vertebrae Centrurrr morphotr-pe eramined #
Taxon Apatosaurus
Buttressing
18
gracile
presenr
5
gracile
present
Brachiosaurus
3
gracile
presenr
Camarasaurus
25
robust
absent
l.)
gracile
present
Barosaurus
Diplodocus Haplocanth osaurus
A
gracile
present
titanosaurid
3
robust
absent
'$7DC
BB1, (13); Haplocdnthosaurus, CM 572, CMNH 10380, USNM 405612, (4); unidentified titanosaurid, SB 655 and 10865,
(uncatalogued), (3). Cervical vertebrae 7 andS of CamarasaurusBYLJ 6504,8 and9 of Diplodocas CM 94, aod 7 of Haplocdnthosdurus CMNH 879 and of titanosaurid SB were subjected to computerized axial tomographic (CT) X-rays, using S-mm-thick slices and employing human thorax protocol to produce not only cross-sectionai scans, but also three-dimensional reconstructions (using General Electric, Sytec-i 3000 at Southwoods X-ray, Youngstown, Ohio). Contrast and density (windows) of the resulting images were adjusted so as to record only the major deposits of the denser compact bone, thus excluding the cancellous bone. However, in the absence of significant amounts of compact bone, sensitivity was increased to reveal the distribution pattern and relative abundance of the cancellous bone.
Institwtional abbreuiations. AMNH-American Museum of Natural History, New York, New York; BYU-Brigham Young University, Provo, Utah; CM-Carnegie Museum of Natural History, Pittsburgh, Pennsylvania; CMNH-Cleveland Museum of Natural History, Cleveland, Ohio; DMNH-Denver Museum of Science & Nature, Denver, Colorado; FMNH-Field Museum of Natural History, Chicago, Illinois; KU-University of Kansas Museum of Natural History, Lawrence, Kansas; SB-State University of New York at Stony Brook, New York; USNM-National Museum of Natural Historn'Washington, D.C.; WDC-Wyoming Dinosaur Center, Thermopolis, Wyoming; and YPM-Peabody Museum, Yaie University, New Haven, Connecticut.
Description of Sauropod Cervicals
A twofold approach was taken to reveal the basic, structural designs of the cervical centra in sauropod dinosaurs that may be in236
.
David S. Berman and Bruce M. Rothschild
dicative of neck posture: (1) mid-cervical centra were categorized on the basis of their gross external morphology, particularly overall shape and proportions, and the presence or absence of prominent buttresses or laminae. It should be pointed out that the term "buttress" is used here in a biomechanical sense to describe what'Wilson (1999) referred to as laminae, which has precedence in usage (Phillips 7871,, 255); and (2) examples of centra exhibiting contrasting external morphologies were subjected to CT X-rays with three-dimensional reconstruction capability to determine whether they also exhibit contrasting internal morphologies in the distribution patterns and relative abundances of compact and cancellous bone. On the basis of the three-dimensional structure of a cervical centrum, a functional stress analysis is proposed to suggest whether the neck was heid in a nearly horizontal or vertical position. Thus, it is hoped that the external morphology of a sauropod cervicai centrum could be used as indirect evidence of neck posture' Using gross external morphology, two morphotypes of sauropod cervical centra, robust and gracile, are recognized as exhibiting three contrasting sets of features (Figs. 11.1, 11.2). The robust-type centra are characterized as (1) being relatively short, with a posterior transverse width that ranges from about 60'/" to 90'/, of the
centrum length, (2) lacking prominent midlength waisting or narrowing, and (3) lacking well-developed, ridgelike buttresses. In contrast, the gracile-type centra are characterized as (1) being relatively long, with a posterior transverse width that ranges from about 25"/" to 42o/" of the centrum iength, (2) exhibiting prominent
midlength waisting or narrowing iaterally and ventrally, and (3) possessing well-developed, ridgelike buttresses. A survey of numerous specimens of seven different sauropods (Table 11.1) reveals 100o% association of the features of robust-type cervical centra in Camarasaurus and an unidentified titanosaurid from Madagascar, on the one hand, and those of gracile-type centra in Diplodocus, Ap at o s auru s, H ap I o canth o s aur u s, B ar o s duru s, and B r a ch i o s lur us, on the other. In Camarasaurzzs the eighth cervical centrum is easily distinguished from the other cervical centra in being not only noticeably ionger in absolute size, but also relative to its transverse width (Fig. 11.28) (Osborn and Mook 1921). However, the width-
to-length percentage of the eighth centrum falls well short of the range of values recorded for the gracile-type centrum. In order to determine whether robust and gracile-type cervical centra can be characterized by significant differences in internal structure, CT images of vertebral centra were subjected to threedimensional reconstructions rvith the density and contrast adlusted so as to record only the distribution pattern and relative abundances of the more opaque compact bone. The CT image of the robust centra \e.g., Camarasaurus) revealed no significant structural features of compact bone. Readjustment of the image, however, to a wider density window revealed a diffuse distribution of the less opaque cancellous bone throughout the centrum interior (Fig. 1,1,.2A, B). This is in marked contrast with images of a Diplodocus Neck Posture of Sauropods Determined Using Radiological Imaging
'
237
Fig. 11.1. Lateral uietus of (A) mid-ceruical ueftebra
of
Diplodocus carnegri CM 91 (anterior to right and with rib missing) and (B) ceruicals 7 and 8 of Camarasaurus lentus CM 11059 (anterior to left dnd rib of ant eri ormo st u er t e br a mi s sing). Note absence of transuerse central bwttress (TCB) in Camarasaurus centrd.
centrum (Fig. 11.2C), which exhibited a pattern of four distinct areas of concentrated compact bone. Two of these areas consist of bands extending the length of the centrum along its dorsolateral and midventral surfaces. The dorsolateral bands are much broader anterior to the base of the neural arch, whereas the midventral band erhibits a pronounced broadening posteriorly to include the entire ventral surface of the centrum. The second area of compact bone concentration forms a prominent, ridgelike buttress that extends posteroventrally across the anterior half of the lateral surface of the centrum and is referred to here as the transverse central but'lTilson tress (see also fig. 39, and Sereno 1998). Lastly, circumferential bands of compact bone are present at the ends of the centrum. Collectively, the bands and buttresses of compact bone of the
238
.
David S. Berman and Bruce M. Rothschild
Fig. 11.2. Computerized axial omo gr ap h ic cr o s s - s e ctio nal s cans of mid-ceruical uertebrae of sauropods: 1At transuerse section through centrum (dorsal toward top of p,tgat: rBt threedimensional r e construction of centrum in lateral uietu (anteilor to left) of Camarasaurus BYU 6504 tuith sensitiuity adjusted to reueal cancellous bone (white areas) ; (C) three-dimensional reconstructions of mainly centrum in oblique lateral uiew (anterior to Ieft) of ceruical uertebrae of Diplodocus carnegii CM 94 ruith sensitit/ity adiusted to reueal comPdct bone. Abbreuiation: TCB = transuerse central buttress, t
Neck Posture of Sauropods Determined Using Radiological Imaging . 2J9
centrum are arranged so as to define partially a hollow, hourglassshaped structure.
Analysis and Discussion The hypothesis being tested here contends that rhe magnitude of the mechanical stresses and their orientation to the cervical centrum should be observable in the distribution parterns and relative abundances of the compact and cancellous bone. The structure of the centrum is assumed to minimize the mass of bone utilized without sacrificing its ability to withstand the srresses encountered under normal movements of the neck. Paramount to this analysis is an understanding of the exrremely important differences in the structural properties between compact and cancellous bone, which are related primarily to porosity. Compact bone is essentially solid, with very low porosity limited to Haversian canals, canaliculi, capillaries, and erosion sites, whereas cancellous bone can be characterized as exhibiting large spaces or cavities that are interconnected by fenestra. Differences in porosity are related apparently to strikingly different physical properties between compacr and cancellous bone, with the former being denser, stiffer, heavier, and, most importantly, stronger. Both types of bone, however, are typicalry found directly associated, but difference in porosity allows them to be very easily discernible to the naked eye, and the transition from one to the other occurs usuaily over a very short distance. Governed by the widely accepted axiom that dictates that the mass of any element is maintained at the minimum required for it to perform properly within the range of its normal structural demands, extreme differences in structural demands should be observable in noticeable differences in the distribution patterns and relative abundances of the compact and cancellous bone (Mow and Hayes
1997; Einhorn 1996). That is, the question being posed here rs whether the cervical centra of sauropods exhibiting distinctively different structural designs that use greatly differing proportions of compact and cancellous bone can be correlated with distinctly different neck postures of horizontal versus vertical. Assuming that the two centra morphotypes, gracile and robust, reflect contrasting neck postures, then an analysis of the probable, primary, mechanical srress forces rhat acted on them should provide an explanation for their structural differences. That is, if rhe ielarive magnitudes of the stress forces a sauropod centrum was subjected to are directly related to neck orientation, then the centrum structure would be expected to provide a basis for determining whether neck
posture was predominately horizontal or vertical. Cervical vertebrae in forms such as birds, deer, or giraffes fail as modern anaIogues in such an analysis, because their necks are not as massive as those of sauropods and would produce a scaling artifact that would likely negate their value as a model (McMahon 1975; Alexander et aL.1979; Alexander et al. 1985; Alexander 1989; Hokkanen 1986; Biewener 1989; Bertram and Biewener f990).
240 . David
S. Berman and Bruce
M. Rothschild
tiirection of-fS
direction of TS ctuvertecl t0 CS alnus TCB
dilection of CS i I
neck anchored at shoulder girdle
I
Iig. 1 1.3. Diagrantmatic draning of the neck dnd head of a longneck sauropctd held irt a ltorizontal posc to illuslrate its analogy to d cantileuered beam supported at the shoulder girdle dnd *bjected tr-t a grauitational loadtng lorct cnncen!ratcd at its free or distal end. The centrd dre considered the principal elements of the beam (neural arches and ribs omitted), tuhich are of the gr d c il e m orp
glar itati onal loacling tblce
A rather simple analysis of the forces acting on the neck, or its cervical centra, is performed here that assumes a few generalizations: (1) the neck is compared to a cantilevered beam that is anchored or supported at the shoulder girdle; (2) the principal loading force on the neck is gravitational and acts along the entire length of the column, but the loading effect is regarded as if concentrated at the distal (cephalic) end of the neck; (3) the centra are considered the principal elements forming the cantilevered beam, and the influence of the neural arches in counteracting the stress forces is not considered significant enough to otherwise alter the basic structural requirements of the centra (Francois 1975; Stevens and Parrish 1999): and (4) each vertebral unit, or centrum, can be
h
otyp e
(r e latiu
e
I.t
Iong compttred to didmeteL narrow tou'ard midlength, and possesslng a lateral tr.tnsuerse central buttress ITCBI). Ottlines of the cenlrn corrcspond l, n1o1u, deposits of comPdct bone and where tensile or tension and compressictn stresses due tct grauitatktnal lodding are concentrdted. Tensile stress (TS) is directed Llnteriorly along dorsal surfaces rtf centra and comltression st/ess (CS) is directed posleriorlt' along uenlral surfacr's. Portion,'I the tcnsile s!rt'ss is redirected b1- the transuerse central buttress (TCB) as contpression stress.
analyzed as if subjected to the same stress forces as the whole of the
neck, That is, each centrum can be viewed as a separate' cantilevered beam anchored at its posterior end to the preceding centrum. Following these generalizations, two types of structural design of the centra in sauropods can be hypothesized that would
meet the stress demands anticipated if the necks were held either at or near a horizontal or verticai posture. In the standard analysis of a cantilever beam that is held horizontally and loaded at its free end, two equal and opposite principal stress forces are described as passing through the length of the
beam (Fig. 11.3). Tensile or tension forces are transmitted anteriorly along the dorsal surface of the beam and compression forces are transmitted posteriorly along the ventral surface of the beam. The stress forces are typically visualized as lines or trajectories that gradually become more closely spaced toward the dorsal and ventral margins of the beam to indicate areas of greatest stress. Therefore, the greater the magnitude of the loading, the greater is the
number and peripheral concentration of the stress lines. On the other hand, increased spacing of the tensile and compression stress Iines toward the center of the beam indicates a drop in the magnitude of the stresses to a theoretical zero in a neutral zone' If this theoretical pattern of stress lines is used to predict the distribution patterns and relative abundances of compact and cancellous bone Neck Posture of Sauropods Determined Using Radiological Imaging
'
241
in a cervical centrum loaded as a cantilevered beam, then the more tightly placed lines of stress at the dorsal and ventral margins of the bone, where the greatest tension and compression stresses are concentrated, is where compact bone would be expected to be present
in relatively substantial
amounrs. Internalln where the lines of
stress become fewer and more wideiy spaced, cancellous bone, bone marrow, or simply voids would be expected. However, cancellous bone is always intimately associated with the compact bone and therefore with loaded surfaces where stresses are reasonably constant. In this situation the cancellous bone generally lies internal to the compact bone and has the appearance of very porous, compact bone with interconnecting holes between an array of little struts or beams referred to as trabeculae. The trabeculae of cancellous bone functions structurally by their orientation to direct stresses outward to the compact bone (Hansson et al. 1987; Mow and Hayes 1991; Einhorn 1996). The above theoretical distribution pattern of compact bone
of the Diplodocus midof Figure 77.2C. Most importantly, it is what would be expected if the neck were held at or near a horizontal matches that exhibited by the CT X-rays
cervical centrum
pose and had to resisr strong gravitational loading (Martin et al. 1998). The pronounced deposits of compact bone along the dorsolateral and midventral surfaces of the centrum would have ct-runtered strong tensile and compression stresses, respectively. The compact bone of the prominent, transverse centfal buttress can also be explained as having played an important role in helping to support the neck. Because the buttress is oriented posteroventrally and unites the dorsolateral and midventral bands of compact bone, a significant portion of the tensile stress directed anteriorly along the dorsal surface of the neck would have been redirected posteroventrally as compression stress to the ventral surface of the column. The advantage of this strategy becomes obvious when comparing the ability of bone ro resisr compression and tensile forces. Bone, as
is the case in most materials, can withstand a much greater compression force than tensile or rension force. This is especially true of bone tissue, in which the compression strength (the maximum compression force it can sustain before breaking) exceeds tensile strength by approximately twice (Pugh et aL. 1.975; Currey 1984, 2002). This functional explanation of the rransverse cenrral buttress also accounts for the more extensive development of compacr bone on the dorsolateral surfaces of the centrum anterior to the base of the neural arch and on the ventral surface of the oosterior half of the centrum. Both areas lie on the trajectory pnih of th. redirected compression stresses passing through the transverse central buttress.
Significant deposits of compact bone enclosing the margins of the anterior and posterior rims of the centra are also considered as areas indicative of major structural stresses. In contrast to gravitational loading, however, these stresses are probably due mainly to compression or tensile forces exerted by the pull of stretched liga-
212
.
Davtd S. Berman and Bruce M. Rothschild
ments spanning vertebrae and contracted muscles during lateral flexion of the neck. It could be argued that the significance of the robust or gracile character of cervical vertebrae relates simply to airlrespiratory sac cavities (pleurocoels) (Wedel 2003), but an alternative explanation can be offered. The development of gracile vertebrae could repre-
sent an anatomical modification
to
lessen the osseous,
or
bone
weight, of the neck. However, given the relatively small mass of the neck, as compared to that of the entire bodS its reduction would have minimal effect if the animal's neck were held at or near a vertical pose. Neck mass would have a greater impact, however, if the neck were held horizontally. A longer neck places the moment arm farther from the body (Fig. 11.3), which magnifies the effect of the neck weight. Increasing the graciie structure of cervical vertebrae significantly reduces the torque of the moment arm and, therefore, the amount of cervical muscle activity necessary for maintaining a
horizontal neck posture.
If the neck of a sauropod were held in a vertical or, more realisticalln in a near-vertical pose, gravitational loading of the neck would be predominately axial, with the overwhelmingly dominant stress being compression. Under these conditions compression forces would be most effectively countered if distributed uniformly over the entire cross-sectional area of the centrum and if acted on the lighter cancellous bone as the structural material of the centrum (Hansson 7987). Tensile stress due to bending would be essentially nonexistent or negligible, and the necessity for compact bone would be minimal and mainly to resist the pull of ligaments and muscles. This is the pattern revealed by CT X-rays of the Cama-
rasaurus mid-cervical centrum (Fig. 11.2A, B) when adjusted to a sensitivity suf6ciently high enough to record cancellous bone. The differences in the distribution patterns and relative abundances of the compact and cancellous bone that distinguish the robust- and gracile-type centra also provide an explanation for the
prominent and diminished midlength waisting or narrowing of their centra. According to Frost (1'964), when a centrum is loaded in axial compression there is a potential for outward bulging deformation of the outer walls due to pressure exerted by the fluid-like marrow (including fat, blood-forming tissue, and blood) contained in internal spaces, a phenomenon he referred to as the internal hydraulic effect. This can be observed indirectly in vertebral compression fractures prior to the reparative remodeling that usually restores the compact bone margins (Recker 1993; Keller et al. 2003). degree of influence of the internal hyexpected between robust- and gracile-type would be draulic effect is the robust type found in Camarasaurus of centra. If the centrum core of cancellous bone larger cross-sectional and has a relatively hydraulic effect internal the spaces, with small, marrow-filled
A strong difference in the
would be minimal. In this instance, according to Frost (1964), the cancellous bone provides the necessary resistance to the compression loading of the centrum, and outward bulging would not be a Neck Posture of Sauropods Determined Using Radiological Imaging
'
243
problem. On the other hand, if the centrum is of the gracile type found in Diplodocus, rvith a relatively narrow width and a muchreduced core of cancelious bone, the internal hydraulic effect due to compressional loading, despite the probable presence of relatively small, marrow-filied spaces, may have been potentially great enough to cause an outward bulging of its outer walls. If, howevcr, the outer walls of the centrum are waisted, any internal, outwardly directed pressure could be more effectively countered, as it must first act to reverse the curvature of the outer wails. This would result in the internal pressure of the centrum being redirected by the compact bone of the outer walls of the centrum anteriorly and pos-
teriorly as compression force (Frost 1964). Vertebral pneumaticiry (pleurocoels) would not affect the response to the internal h1'draulic pressurer as they are self-contained systems (\X/edel 2003). The above discussion, therefore, suggests that when cervical centra are loaded primarily in compression, as in the case of vertical neck posture in sauropods, the greater their internal content of cancellous or spongy bone and the lesser need for waisting, whereas the reverse would be expected in centra of necks held in a horizontal pose.
Based on the above observations, the contrasting features of the distribution patterns and relative abundances of the compact and cancellous bone in the cervical centra of Diplodocus and Camtrasdurus, as revealed by CT X-rays, suggest correlations between gracile and robust-type centra with horizontal and vertical neck postures, respectively. This also provides corroborarive evidence for the widely accepted interpretations of horizontal neck
posture tn Apatosaurus, Barosaurus, and Haplocanthosaurus, and vertical neck posture in Camardsdurus and titanosaurids (Frey and
Martin 1997; Marrin et al. 1998; Stevens and Parrish 1999). An unexpected implication of this study, however, is that the gracile nature of Brdchiosaurus cervical vertebrae suggesrs a horizontal, rather than the widely portrayed, near-vertical neck posture (Christian and Heinrich 1998). The recently described (Zimmer 7997) initial results of investigations of neck posture in sauropod dinosaurs by K. A. Stevens and M. Parrish (1999; this volume) make the same conclusions as those given above, but based on different morphological data and analyticai techniques. Measurements on the range of movements at the articulation contacts between successive cervical vertebrae, particularly between pre- and postzygapophyseal facets, were processed in a three-dimensional, graph-
ics computer program to determine not only the range of
movements of the necks in several sauropods, but also their neutral, undeflected postures. The results of their study indicate that Apatosaurus and Diplodocus, on the one hand, and Brachiosaurus, on the other, held their necks at about the horizontal and 20o above (suggesting ground feeding or low browsing), respectiveiy, whereas Camarasdurzs held its neck nearly vertically (suggesting high browsing). These results were reaffirmed subsequently by Steven and Parrish (19991 for Apatosaurus and Diplodocus in a more de-
.
Drr-id
S.
Berman and Bruce M. Rothschild
tailed account of the same research. The phylogenetic significance of this variation is, however, beyond the scope of the present discussion, but has been addressed in studies by Salgado et aI. (7997), \Tilson and Sereno (1998), Upchurch (1.998), and Wilson (2002). Inasmuch as the resistance of a cantilevered beam to bending varies inversely as the square of its length, there is a particularly interesting relationship between relative neck length and probable
neck posture among the sauropods considered here. Those sauropods with proportionally the longest necks relative to trunk srze, Apatosaurus, Barosaurus, Brachiosaurus, and Diplodocus, with neck lengths of approximately 6 m, 9 m, 8.5 m, and 8 m, respectively (Gilmore 1936; Zimmer 1.997), apparently held their necks in a near-horizontal pose, whereas the one prominent, relatively short-necked example, Camarasaurzs, is assumed to have held its 3-4-m-long neck in a near-vertical pose (Zimmer 1977). This comparison further explains the strong differences noted in the structural designs betlveen the cervical centra in forms believed to have held their necks at or near horizontal and vertical poses. Acknowledgments. \7e are grateful to Kenneth Carpenter, Larry D. Martin, Mark Norrell, Burkhard Pohl, Robert Purdy, Bill Simpson, Mary Ann Turner, Ken Stadtman, Scott Sampson, and the 'Sfilliams late Mike who qraciouslv allowed us access to their collections.
References Cited
Alexander, R. M. 1989. Mechanics of fossil vertebrates. Journal of the Geological Society 146: 47-52. Alexander, R. M., A. S. Jayes, G. M. Maloiy, and E. M. Vathuta. 1979. Allometry of the limb bones from shrews (Sorex) to elephants (Loxodonta). Jcturnal of Zoology 189: 305-314. Alexander, R.M., J.F. A. Hall-Martin, and D. A. Russell. 1985. Long bone circumference and weight in mammals, birds and dinosaurs.
Journal of Zoology A207: 53-61.
Bertram, J. E., and A. A. Biewener. L990. Differential scaling of the long bones in the terrestrial Carnivora and other mammals. Journal of Morph ology 204: 1 57 -1,69. Bieweneq A. A. 1989. Scaling body support in mammals: Limb posture and muscle mechanics. Science 250: 45-48. Carter, D. R., and \7. C. Hayes. 1997.The compressive behaviour of bone as a two-pl-rase porous structure. Journal of Bone and Joint Surgery
954:954-962.
Chatterjee, S., and Z. Zheng. 1997. The feeding strategies in sauropods. Journal of Vertebrate Paleontology 77: 37 A. Christian, A., and W.-D. Heinrich. 1998. The neck posture of Brachiosaurus brancai. Mitteilung aus dem Museum fiir Naturkunde zu Berlin, Geowissenschaftenliche Reibe 1: 73-80. Coombs, !7. P., Jr. 1975. Sauropod habirs and habitats. Palaeogeography, Pdlaeoclimatology, Paleoecology 17 : 1,-33. 1984. Mechanicdl Adaptation of Bones. Princeton, N.J.: Princeton
University
Press.
Currey, J. 2002. Bones. Princeton, N.J.: Princeton University Press. Neck Posture of Sauropods Determined Using Radiological Imaging
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24J
Einhorn, T. A. 1996. Biomechanics of bone. In L. Bilezikian, L. Raisz, and G. Rodman, eds., Principles of Bone Biology,25-37. San Diego: Academic Press. Francois, F.J.1975. Ligament insertions into the human lumbar vertebral body. Acta Anatomica 91 467480. Frey, E., and J. G. Martin. 1997. Long necks of sauropods. In Dinosdurs, 406409. San Diego: Academic Press. Frost, H. M. 1964. The Laws of Bone Structure. Springfield, Ill.: Charles C. Thomas. Gilmore, C. Vi. 1936. Osteology of Apatosaurus, with special references to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 1.1:175-300.
Hannson, T. H., T. S. Keller, and M. M. Panjabi. 1987. A study of the compressive properties of lumbar vertebral trabeculae: Effects of tissue characteristics. Spine 12: 56-62. Hokkanen, J. E. 1986. The size of the largest land animal. Journal of Theoretical Biology 118: 491499. Janensch, W. 1947. Pneumatizitat bei Wirbein von Sauropoden und anderen Saurischier. Palaeontogrdphica, supp. 7: 1-725. 1950. Die Wirbelsiiule van Brachiosaurus brancai. Palaeontograpbica,supp. 7: 27 -93. Keller, T. S., D. E. Harrison, C. J. Colloca, D. D. Harrison, and T. J. Janik. 2003. Prediction of osteoporotic spinal deformity. Spine 28: 455462. Longman, H. A. 1933. A new dinosaur from the Queensland Cretaceous. Memoirs of the Q.ueensland Museum 13: 133-144.
Martin, J. 1987. Mobility and feeding of Cetiosaurrs (Saurischia; Sauropoda): \fhy the long neck? In P. J. Currie and E. H. Koster, eds.,
Fourth Symposium of Terrestrial Mesozoic Ecosystems, Short Paper, 154-I59. Drumheller, Alberta, Canada: Royal Tyrrell Museum of Paleontology.
Martin, J., J.V. Martin-Rolland, and E. Frey. 1998. Not cranes or masts, but beams: The biomechanics of sauropod necks. Oryctos 1: 113-120. McMahon, T. A.
197 5. Allometry and Biomechanics; Limb bones in adult ungulates. American Naturalist I09: 547-563.
Mow, V. C., and Sf. C. Hayes. L99L. Basic Orthopaedic Biomechanics. New York: Raven Press. Osborn, H. F., and C. C. Mook. L921. Camardsdurus, Amphicoelias, and other sauropods of Cope. Memoirs of the American Museum of Natural History 20: 181-190. Panjabi, M. M., K. Takata, V. Goel, D. Federico, T. Oxland, J. Duranceau, and M. Krag. 1991. Thoracic human vertebrae: Quantitative threedimensional anatomy. Spine 1,6: 888-901. Paul, G. S. 1988. The brachiosaur giants of the Morrison and Tendaguru with a description of a new Subgenus, Giraffititan, and a comparison of the world's largest dinosa:urs. Hunteria 2: 1-14. 1998. Limb design, function and running performance in ostrichmimics and tyrannosaurs. Gaia 15:257-270. Phillips, J. 1877. Geology of Oxford and tbe Valley of the Thames. Oxford: Clarendon Press. Pugh, J.'W., R. M. Rose, and E. L. Radin. 1975. Buckling studies of single human trabeculae. Journal of Biomechanics 8: 1'99-201. Recker, R. R. 1993. Architecture and vertebral fracture. Calcific Tissue International 53: 5139-142.
246 . David
S. Berman and Bruce
M. Rothschild
Rockoff, S. D., E. Sweet, and J. Bleustein. 1969.The relative contribution of trabecular and cortical bone to the strength of human lumbar vertebrae. Calcific Tissue Research 3: 163-17 5. Rothschild, B. M., and D. S Berman. 1991. Fusion of caudal vertebrae in Late Jurassic sauropods. Journal of Vertebrate Paleontolctgy 11: 29-36. Salgado, L., R. A. Coria, and J. O. Calvo. 1997. Evolution of titanosaurid sauropods. I: Phylogenetic analysis based on the postcranial evidence.
Ameghininiana 34t 3-32. Stevens, K. A., and J. M. Parrish. 1999. Neck posrure and feeding habits of two Jurassic sauropod dinosaurs. Science 284:798-300. Upchurch, P. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of the Linnean Society 724 43-103. 'Wedel, M. J. 2003. The evolution of vertebral pneumaticity in sauropod dinosaurs. Journal of Vertebrate Paleontology 23: 344-357. 'Wedel, M. J., and R. K. Sanders. \999. Comparative anatomy and functional morphology of the cervical series in Aves and Sauropoda. /ozrnal of Vertebrate Paleontology 19: 83A. J. A. 1999. A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs. Journal of Vertebrate Paleontolr,tgy
'$?ilson,
19:639-653.
2002. Sauropod dinosaur phylogeny: Critique and cladistic analyZoological Journal of the Linnean Society 136:21,7-276. 'Wilson, J. A., and P. C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Memoir 5. Journal of Vertebrate Paleontology (supp. to no. 2): 1-68. ZimmeqC. f997. Dinosaurs in motion. Discouer 18(11): 96-109. sis.
Neck Posture of Sauropods Determined Using Radiologicallmaging
. 2!/
12. Evolution of the Hyposphene-Hypantrum Complex within Sauropoda SpeesrrAN Appsrecuie
Abstract The hyposphene-hypantrum accessory articulation complex is present in several archosauromorphs (e.g., rauisuchids). However, because it is absent in early dinosauriomorphs (e.g., Marasuchus) and ornithischians, it can be regarded as a saurischian synapomorphy, and thus plesiomorphic for sauropods. The shape of this complex within Sauropoda is extremely variable and its homologies far from clear. The rhomboidal primitive configuration remains present in
Diplodocoidea. In Macronaria, conversely, the hyposphenehypantrum complex is sharply different, as it is in some basal titanosaurs (e.g., Andesaurus delgadoi and Phuwiangosaurus sirindbornae) that bear hollow rhomboidal hyposphenes. In basal Macronaria, the hyposphene is ventrally widened, and rn Brachiosaurus brancai and other basal titanosauriforms there are both ventrally widened and bifid hyposphenes. Several Late Cretaceous sauropod lineages have independently
lost the hyposphene-hypantrum complex in the dorsal vertebrae (e.g., rebbachisaurids in Diplodocoidea and titanosaurs in Macronaria). In the titanosaur lineage, the lost hyposphene-hypantrum is replaced 248
with a new accessory structure deveioped from a bifid hyposphene plus the medial centropostzygapophyseal laminae. Advanced titanosaurs are characterized by the absence of a hyposphenehypantrum complex; a light, camellate vertebraeq a skeleton much replaced with cartilage; and a wide anterior blade on the ilium for muscies. These adaptations allowed them to develop a relatively free and rapid locomotion, even by heavily armored forms. The titanosaur specializations are predictable in the context of growing angiosperm importance and the relatively low ornithischian diversity in South America, and perhaps throughout the Gondwanan terrestrial ecosystems during the Late Cretaceous period.
Introduction Accessory articulations are fairly common in reptile dorsal verte-
brae (e.g., hyposphene-hypantrum and
zygosphene-zygantrum
complexes). The hyposphene-hypantrum articulation involves a "positive" structure, the hyposphene, on the posterior side of the vertebra below the postzygapophyses, and a "negative" structure, the hypantrum, betr,veen the prezygapophyses of the next vertebra where the hyposphene fits. This complex is rather common in unrelated archosauromorph lineages (e.g., rauisuchids), especially large forms, and is thought to give rigidity to the vertebrae: dorsals and proximai caudals in sauropods and caudals in theropods (Powell 2003). Because the hyposphene-hypantrum complex is absent in early Dinosauromorpha (e.g., Marasucbus) and ornithischians, Gauthier (1986) postulated that it was a saurischian synapomorphy, and thus plesiomorphic for sauropods. The hyposphene-hypantrum complex is present in prosauropods, such as Lessemsaurus sauropoides (Bonaparte 1999), and also in eusauropods, such as Omeisaurws tianfuensls (He et al.
1988), Patagosaurus fariasi (Bonaparte 1986), Bdrapasaurus
tagorei (Jain et al. 1997), Shunosaurus lii (Zhang 1988), Diplodoci-
dae (Hatcher 1901; Janensch 7929), Mamenchisaurus (Young
19 541, Lapparentosurus (Bonaparte 1,999), Camarasauridae (Osborn and Mook 7927), Brdchiosaurus brancai (Janensch 1950a), Phuwiangosaurtts sirindhornae (Martin et al. 1994), and Andesaurus delgadoi (Calvo and Bonaparte 1991). Its presence has also been reported for the titanosaurs Epachthosaurus sciuttoi (Martinez et al. 1991) and Argentinosdurus hwinculensis (Bonaparte and Coria 1.993). The shape of the complex within Sauropoda is extremely variable and its homologies are far from being resolved. However, there is an independent trend in Late Cretaceous lineages of sauropods toward the loss of hyposphenehypantrum articulations as seen in rebbachisaurid diplodocoids
and titanosaur macronarlans.
Institutional abbreuiations. BYU-Brigham Young University; MACN-Museo Argentino de Ciencias Naturales "B. Rivadavia," Argentina; MLP-Museo de La Plata, La Plata, Argentina; and MPEF-Museo Paleontol6gico "E. Feruglio," Trelew, Argentina. Evolution of the Hyposphene-Hypantrum Complex
.
249
Materials and Methods Specimens examined. Material examined included numerous specimens of titanosaurs and the cast of Diplodocus cdrnegii housed
in the Museo de La Plata, Patagosdurus fariasi (MACN 250-326), Chubutisaurus insignis (MACN 18222), cf , Epachthosdurus (UNPPV-920), Andesaurus delgadoi (MUCPV-132), and Neuquensaurus australis, and various specimens at Brigham Young University. Specimens from the literature include diplodocoids (e.g., Apatosaurus excelsus, A. louisae, Barosaurus lentus), basal macronarians (e.g., CamardsAurus supremus) and titanosauriformes (e.g., Brachiosaurus, Venen o s dur u s, Atld s aur u s, and P h uw i an go s dur u s s ir in dh o rnae) . The phylogenetic framework used is based on Salgado et al. (1997), \X/ilson and Sereno (1998), \7ilson (2002), Wilson and Upchurch (2003), and Salgado (2003). Lamindr homologies.In order to understand the homologies of laminae and structures related to the hyposphene-hypantrum compler, it is necessary to refer to'Wilson (1999). He analyzed, correlated, and discussed the nomenclature of sauropod vertebral laminae as used by different authors. This nomenclature is very useful for describing and comparing these complex structures, which not only vary among closely related taxa, but aiso for their position on the vertebrae in a series and ontogenetic stage. Furthermore, lamina development can also vary on each side of the vertebra (e.g., I'Jeuquensaurtts australis, Salgado et al. submitted). The hyposphene involves several laminae in its structure. The posterior centrodiapophyseal lamina laterally frames the region, extending from the dorsal edge of the centrum, to the postzygapophyses dorsally. The laminae are here described, characterized and typified in the complex in order to avoid future confusion. I propose to use "type" laminae when referring to taxa that typify a structure. 'Sfithin a phylogenetic context, the use of "lamellotypes" will be useful in order to avoid wrong comparisons, especially because laminae are used as characters of high phylogenetic value. They are: C e ntr op o st zy gap op h y s e al I amin a e (\X/ilson 79 9 9) . This consists of paired laminae developed between the postzygapophyses and the dorsal edge of the centrum. \flilson (1999) stated that these laminae originate far from the midline in anterior dorsal vertebrae, whereas in posterior dorsals, with a well-developed hyposphene, they originate in the middle. However, anterior dorsals of A. louisae show where the centropostzygapophyseal lamina meers the posterior centrodiapophyseal laminae, a poorly preserved lamina in the position of the centropostzygapophyseal lamina. Furthermore, almost all dorsals of A. excelsus shor,v the centropostzygapophyseal lamina in their normal placement and another pair of laminae in the position of \il/ilson's centropostzygapophyseal laminae. The same occurs in Brdchiosaurus brancai, B. altithorax, the titanosaur Ampelosdurus atacis (see Le Loeuff, this volume), and in Argentinosaurus huincwlensis. Clearly, there exists an additional distinctive lamina. The centropostzvgapophyseal laminae are therefore redefined
250 .
Sebastidn Apesteguia
to lateral extent of the postzygapophyses articular surface to the dorsal edge of the centrum, but not close to the neural canal. The "lamellotlrpe" of this lamina is present in the ninth dorsal of A. louisae (Fig. 12.1). The centropostzygapophyseal iamina is differentiated from another lamina with a relatively close location, the medial centropostzygapophyseal lamina (described below). The centropostzygapophyseal lamina forms the main pillars in posterior dorsals of A. excelszs and A. louisae, but not in the most anterior vertebrae, where the medial centropostzygapophyseal lamina has such a function. The centropostzygapophyseal iamina are the main infrapostzygapophyseal pillars in Haplocanthosaurus (Hatcher 1906), Brachiosaurus brancai, and Brachioslurus dltithorax; however, they are absent in titanosaurs, where they are replaced by the medial centropostzygapophyseal laminae. The basal titanosaurs have both laminae, as seen in AntpelosaLtrus, Maldwisaurus, and Argentinosaurus (Fig. 12.2K-M). Medial centropostzygapophyseal laminae (new). Paired laminae that are developed between the medial-most part of the postzygapophyses and the dorsal edge of the centrum, closely bounding the neural canal. The "lamellotype" of this lamina is present in the first dorsal of A. excelsus (scheme in Fig. 12.2).The medial centropostzygapophyseal lamina forms the main pillars in the anterior dorsals of A. excelsus, A. louisae, Diplodocus carnegii, Barosaurus, and Tendaguria (Bonaparte et al. 2000). In the titanosaur lineage, mid-dorsals of Phuwidngosdurus sirindhornae bear well-developed medial centropostzygapophyseal laminae, which are also the main as paired laminae, developed from the mid-
infrapostzygapophyseal pillars
in
derived titanosaurs, such
as
Isisdurus colberti, Saltdsaurus loricatus, and Opisthocoelicaudia. \fhere the hyposphene is not well developed, as in the third dorsal of A. excelsus (scheme in Fig. 12.2), these laminae exist but have a separate origin at the medial-most ends of postzygapophyses. In specimens where the hyposphene is developed, these laminae could be called the centrohyposphenal laminae, but this probably corresponds to the medial centropostzygapophyseal laminae (Fig. 12.3). The oniy reason to suggest that the medial centropostzygapophyseal lamina and the centrohyposphenal lamina could be different in origin is the presence of a poorly developed centrohyposphenal in the eighth dorsal of A. excelszs, in addition to the presence of the medial centropostzygapophyseal lamina. In the fourth dorsal of A. excelsus is also seen an incipient development of medial centropostzygapophyseal lamina under the hyposphene, The centrohyposphenal lamina (i.e., medial centropostzygapophyseal lamina, where the hyposphene is present) is clear in the ninth 'Where dorsal of A. excelsus. the hyposphene is present, in posterior dorsals, the medial centropostzygapophyseal laminae arise from their base as parallel, tail pillars that bound the neural canal, acting as paired laminae developed between the ventrolateral margins of the hyposphene and the dorsal edge of the centrum, directly boundine the neural canal. Evolution of the Hyposphene-Hvpantrum Complex
.
25
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Fig. 12.1. Primitiue sauropod and Diplodocoid dctrsal uertebrae in posterior uieu. (A) Close-up o/r/:e Apatosaurus lotisae seuenth dorsal uertebra shouing the hyposphene zone and rclated laminae (frotn Gilmore 19.J6). (B-C) Jut,enile and adub o/ Patagosaurus fariasi showing the ontogenetic euolution of th e byposphene in non-neosauropod saurop ods. (D) Barapasaurus tagorei (from Jain et al. 1977). (E/ Apatosaurus louisae seuenth dorsal uertebra. lF) Apatosaurus louisae ninth dorsal uertebra. (G) Haplocanthosaurus pnscus thirteenth dorsal uertebra hnodified front Dalla Vecchia 1998). (H) Dicraeosaurus sattleri posterior dorsal (from Janensch 1929). I-K: Rebbachisaur posterior dorsal uertebrae: 0/Histriasaurusboscarollii (modifiedfromDallaVecchialggS);(J)Rebbachisaurusgarasbae QnodifiedfrontBondpdrte 1999); (K) "Rebbachisaurus" tessonei (from Dalla Vecchia 1998); (.1) dnd (K) Iack hyposphene. Abbreuiatktns: cpr.tl = centropostzigdpophyseal lamina; mcpol = medial centropostzigdpophyseal lamina; tpol = intrdpostzigdpophyseal lamina.
252 .
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Fig. 12.2. Sketches shcnuing the distribution of laminae that surrotntd the bypospbene in sauropod dorsal uertebrae. Numbers cctrrespond utith position. (A) Apatosaurus excelsus (modified from Gilmore 193 5) . (B) Apatosaurus louisae (modified front Cilmore 1936). (C) Diplodocus carnegii (modilied from Hatcher 1901). (D)Barosaurus lentus (modified from Lull 7911)), dorsals 1,1, 5, and 9 respectiuelt. (E) The rebbachisaurs Histriasaurus boscarollliand "Rebbachisaurus"tessonei (modifiedfromDallaYecchial99S;CaluoandSalgadol995),mid-posteriordorsals.(F) Camarasaurus grandis (modified from Osborn dnd Mook 1927), anterior, mid, and posterior dorsals respectiuely. (G) Haplocanthosaurus priscus (tnodified from Hatcher 1906), tuo posterior dorsals. (H) Brachiosaurus brancai (modified from Janensch 1950), dorsals 4, 6, 7, and B respectiuely. /1) Eucamerotus foxi (modilied from Hulke 1880), posterior dorsal uertebra. l/ Brachiosaurus altithorar (modified from Riggs 190'1), dorsals 6 and 12 respectiuely. (K) The titdnosaurs Phuwiangosaurus sirindhornae, Andesaurus delgadoi, and Malawisaurus dixeyi respectiuely (modified from Martin et d. 1999; Cdluo and Bondpdrte 1991; and Jacobs et al. 1993), posterior dorsals. lL/ Argentinosaurus huinculensis (modified from Bondparte and Coria 1993), anterir.r and mid dorsals respectiuely. (M) The deriued titanosaurs Ampelosaurus atacis, Isisaurus colberti, Opisthocoelicaudia skarzynskn, and Saltasaurus loricatus (modified frotn Le Loeuff 1995; ldin and Bandl'opddhyal' 1997; and Powell 2003), posterior dorsals. Tbe shape and size and relatiue height of postq'gdpophyses utere not considered.
The medial centropostzygapophyseal lamina most commonly reaches the centrum at the outer borders of the neural canal, but in
'Wilson's
some cases has an oblique development and reaches (1999) centropostzygapophyseal lamina base. This feature unites Brachiosaurus altithorax and Eucamerotus foxi, but it is also present in the last dorsal of A, excelsus.ln Camarasaurus grandis they are the main connection between the postzygapophyses and the centrum via the hyposphene. The medial centropostzygapophyseal Evolution of the Hyposphene-Hypantrum Complex
.
253
A
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i '',;'-..---)) -rV-'-!
ig. 1 2. 3. Camarasaurus supremus (from C)sborn and Mook 1921), dorsal uertebrae m posterior uien. (A-B) Third and fourth dorsal uertebrae. (C) Closeup of tbe byposphene region of the sixth, seuenth, and eightb uertebrae showing ( e nt ro p os ! 4, go p o p h y sea I I am i n a and medial F
entr op o stzy gdp op b y s e al lamm a. (D-F) Sixth, seuenth, and eighth
c
dor sal uertchro e. A bbreui ations:
ol = centrop o stzigapop lamina; mcpol = medial cp
c
entr op o stzy gdp op
2.5.1
.
h yse
hy seal
al lamtna.
Sebasti6n Apesteguia
lamina is especially well developed under the hyposphene in Diplodocus carnegii, Supersaurus, Cdmarasaurus supremus ante-
rior and mid-dorsal vertebrae, the complete
series of B. brancai, and at least the mid-dorsals of B. altitholarc. Considering that the basal rebbachisaur Histriasdurus has well-developed medial centropostzygapophyseal laminae and no other marked laminae (Dalla Vecchia 1998), the probably homologous laminae present in "Rebbachisaurus" tessonei, which lacks a hyposphene, are also medial centropostzygapophyseal laminae.
Intrapostzygapophyseal lamina (Osborn and Mook L921,). This is developed as an unpaired vertical ridge between the junction of the postzygapophyses and the dorsal edge of the neural canal. As shown by its development in the third dorsal of A. excelszs, it may be paired in origin, but it is commonly fused into a single structure. The "lamellotype" of the intrapostzygapophyseal lamina is present in the second dorsal of A. excelszs. Upchurch (I998) considered this single median lamina a Diplodocoidea character (#107) that supported and buttressed the hyposphene from below on dorsal neural arches of Barosaurzs and DiOlodocus. Thrs
lamina can be present with or without a hyposphene.
'!(here
a hyposphene is absent, the intrapostzygapophyseal lamina is developed between both the medial centropostzygapophyseal laminae, as in the first dorsals of A. louisae, A. ajax, Barosaurus, and Diplodocus carnegii. \fhen a hyposphene is present, the intrapostzygapophyseal lamina is absent or remains as an addition to the base of the hyposphene giving it a rhomboidal shape. \Tithout the intrapostzygapophyseal iamina, the hvposphene is a broadbased triangie. In some cases, this lamina is only developed above the hyposphene and creates the impression that the hyposphene actually hangs from it. Further studies are necessary to determine whether or not the epihyposphenal part of the intrapostzygapophyseal lamina is a different and independently derived lamina. This review of vertebral lamina demonstrates that hyposphenes are the result of the hypertrophy of the intrapostzygapophyseal lamina pius the addition of the medial centropostzygapophyseal lamina.
The Hyposphene-Hypantrum Complex in Phylogeny
Prior to the development of extensive cladistic analyses of titanosaurs, Bonaparte and Coria (1993) erected the family Andesauridae based on several plesiomorphic features, including the presence of hyposphene-hypantrum. This clade, now considered paraphyletic, included Andesaurus and Argentinosaurus (Bonaparte and Coria 1993). However, Andesdurus has a typical hyposphene, which differs from the supposed hyposphenal structure present in Argentinosaurus and the paraplastotype of Epachthosdurus. The cladistic analysis by Salgado et aI. (1.997) resulted in an unresolved polytomy including Epachthosaurus sciuttoi, Malawisaurus dixeyi and derived saltasaurids. Although Epachthosaurus bears procoelous anterior caudal vertebrae, it also has welldeveloped hvposphenes. Conversely, Malawisaurzzs has some procoelous and some amphyplathian anterior caudal vertebrae and no hyposphenes on the few recovered dorsal vertebrae. Salgado et al. (7997) and Saigado and Martinez (1993) recognized that the Argentinosaurlls structures are not real hyposphenes (contra Bonaparte and Coria 1993), and they coded them as different from
in Epachthosdurus. There is no hyposphenehypantrum complex in derived titanosaurs, such as Opisthocoelicaudia skarzynskii (Borsuk-Bialynicka 7977, 71) and saltasaurines (Powell 2003). The loss of the hyposphene-hypantrum complex in posterior dorsal vertebrae was noted by Salgado et al. (1.997) for Titanosauridae and by Sanz et al. (1999) for Eutitanosauria. Upchurch \1999) considered the loss in both mid- and posterior dorsal vertebrae as synapomorphic for his node "Q." A rhomboidal hyposphene is characteristic of prosauropods and most sauropods. It remains relatively similar in primitive eusauropods (e.g., Patagosaurus fariasi, Bonaparte 1986) and in derived Diplodocoidea (e.g., Diplodocus cdrnegil, Hatcher 7901; Apthose present
Evolution of the Hyposphene-Hypantrum Complex
.
255
cttoslurus louisae, Gilmore 1936). Ontogenetically, dorsal vertebrae of Patagosaurus fariasi show a progressive change \Fig. 12.28, C). The juvenile form shows a small rhomboidal hyposphene that ends ventrally in a short intrapostzygapophyseal lamina hanging over the neural canal. The hyposphene bears two concave ventrolateral faces, which surround a par of fossa and are externally limited by curved ridges. The adult form exhibits an elongate rhomboidal hyposphene with a concave ventrolateral face that is reduced or absent. Although both hyposphenes exhibit a slightly different shape, both can be described as a rhomboidal configuration. Diplodocids commonly exhibit a rhomboidal hyposphene (Fig. 12.2),which is clearly seen in Diplodocus. However, there are sev-
eral variations, especially in the anterior dorsals of
some
diplodocids (e.g., Apatosaurus excelszs,. fourth and fifth dorsal vertebrae, YPM 1980), rvhere the hyposphenes can be hollowed, massive, basally widened, or slightly bifurcated ("whale tail-shaped"). In A. excelsus, the hyposphene margin matches the opposite postzygapophyseal articular surface. This species has hyposphenes developed between dorsals four and nine. Although in the fourth and seventh dorsals, the hyposphene is rhomboidal, the fifth and sixth dorsals bear relatively wide hyposphenes due to the lack of intrapostzygapophyseal laminae. The eighth dorsal has a wide, ercavated hyposphene similar to those of macronarians. The ninth dorsal is small and hangs from an intrapostzygapophyseal lamina. In A. louisae, the hyposphene is alrvays rhomboidal, suggesting a major difference with A. excelsus.In the ninth dorsal, however, rhe hyposphene is small and hanging from a lamina. Diplodocus, Barosaurus, and Histriasaurus also have rhomboidal hyposphenes, hanging from the intrapostzl'gapophyseal lamina. Diplodocid hyposphenes can be opened ventrally (e.g., A. excelsus, eighth dorsal) or closed ventrally with a horizontal ridge (e.g., A. excelsus, sixth dorsal).
Histridsaurus boscarollir, a European diplodocoid, is represented by an isolated vertebra (\7N-V6) characterized by the pres-
ence
of a
hyposphene-hypantrum complex (Fig 12.2I), lvell-
developed outer spinopostzygapophyseal laminae laterally limiting the spine, and highly inclined and long diapophyses. Dalla Vecchia (1,998) considered this taxon a rebbachisaurid, but the presence of
a hyposphene-hypantrum in the dorsal vertebra suggesrs that this taxon is a basal form of a more inclusive group (Gallina and Apesteguia
in
press). Neither Rebbachisaurus garasbae, from the
Albian of Morocco, Africa (Lavocat 1954), nor "Rebbachisaurus" tessonei, from the early Cenomanian of Argentina, bear a hyposphene-hypantrum. Furthermore, Bonaparte (1999) characterized the "Rebbachisaurid" type of dorsal vertebra by the ab, sence of a hyposphene. Other non-diplodocid diplodocoids, such as Dicraeosaurzs (Janensch 1929), bear rhomboidal hyposphenes. \Tilson (2002) concludes that Haplocantbosaurus (Fig. 12.2G) is a basal Diplodocoidea, but the results of Majority Rule Consen-
256
.
Sebastidn Apesreguia
sus are not clear, and the phylogenetic position of this taxon is still uncertain between the basal branches of Diplodocoidea and Macronaria. Haplocanthosrurus, described by Hatcher (1906), has
very long, medial, centropostzygapophyseal laminae. These laminae reach a very reduced rhomboidal hyposphene that hangs from the contact of the subhorizontal postzygapophyses. This feature resembles the condition seen in Cdmardsdurus and Diplodocus, and is different from Apatosaurus. Haplocanthosaurus has both rhomboidal and basally wide hyposphenes.
In Macronaria, the hyposphene-hypantrum complex is different from that of most diplodocoids. As remarked by Bonaparte (1999), Camarasaurus grandis has characteristic, double-spined, anterior dorsal vertebrae that exhibit excavated, ventrally widened hyposphenes (YPM 1901 and 1902) supported by two strong ridges, the medial centropostzygapophyseal laminae that are columnar in shape (Fig. 12.3). They are especially well developed in HaplocanthosdLtrLts, Brachiosaurus, and titanosaurs (Fig. 12.1K-M), and are also present in Diplodoczs (Bonaparre 1999). The lateral margins of the hyposphene in Camarasaurzzs differ from Apatosaurus in that they are narrower and do not mirror the postzygapophyses of the following vertebra. In basal Macronaria (r.e., Camarasaurus), the hyposphene is ventrally wide. However, in Cdrnarasaurus grandis, the single-spined, posterior dorsal vertebrae exhibit wide rhomboidal hyposphenes (e.g., YPM 1901 and 1902).
ln
Brachiosaurus brancai and other basal titanosauriforms there are both ventrally wide and bifid hyposphenes, the latter especially evident in the fourth and seventh dorsals. This is also seen in the Sozorasaurus anterior dorsal vertebrae (Ratkevich 1,998), where the hyposphene bears a wide convex base. The hyposphenes are much better developed in B. altithorax (Riggs 1904) than in B. brancai (Janensch 1950). At the sixth dorsal of both
(Fig.0.a)
species of Brachiosaurus, the medial centropostzygapophyseal lam-
inae are well developed, but the centropostzygapophyseal lamina is only developed in the B. brancai and the hyposphene is proportionally larger in B. dltithorax. Comparing the last dorsals, the laminae
development is rather similar, but B. altithorax shows a large hyposphene and B. brancai does not (see Fig. 12.1). They are similar to the posterior dorsals of the titanosauriform Eucamerotus foxi (= Ornithopsis, Seeley, in Hulke 1880, pl. IV fig. 7). The hyposphene complex in Eucamerotus (Fig. 1,2.6C) looks different from that of diplodocoids. The hyposphene is not rhomboidal, but it is basally wide as in basal macronarians. Furthermore, on each side, the hyposphene base is continuous with a ventrolateral medial centropostzygapophyseal lamina, which meets the centropostzygapophyseal lamina before reaching the centrum (Fig. 12.6C, modified from
Hulke 18 80, pl. lY, frg. 7). The highly pneumatic titanosauriform posterior dorsal neural arch from Istria, Croatia (MPCM-V3), which is described by Dalla Vecchia (7998), bears a strong non-bifid hyposphene, hanging from Evolution of the Hyposphene-Hypantrum Complex
.
257
poz hcc
mcpol
Fig. 12.1. Brachiosaurus brancar (from Janensch 1950), dorsal uerlebrae in posterior uiew: tA-B) anterior dorsals; (C) close-up of the hypospbene region; (D) poslerior dorsal. Abbreuiatictrts: c = centrum; hy = hyposphene; hcc = hyposphenal concauity; mcpol = me dial centrop o stzl gdp op hy s eal lamina; nc = neurdl canal; poz = p ostzygap op hysls; spol = s p i n o P o s t zy ga p o p h1'se al lam i na.
the contact of the postzygapophyses (Dalla Vecchia 1998, fig. 118). The postzygapophyses bear a very wide articular surface, as is ryp-
ical of most titanosaurs. The hyposphene is rhomboidal and dorsoventrally elongate, although the distal portion is strongly
weathered (Dalla Vecchia 1998). Dalla Vecchia (1998) suggested that MPCMV3 and Eucamerotus foxi could actually be closer to titanosaurs than to Brachiosaurus brancai.
The Hyposphene-Hypantrum Complex within Titanosauria The hyposphene and hypantrum in some basal titanosaurs are apparently derived from the bifid structure initially seen in Bracbiosaurus brancdi. A bifid hyposphene-hypantrum articulation is also present in the posterior dorsals of a new taxon from the Aptian of Neuqu6n (Bonaparte et al. submitted). This feature could be diagnostic for Titanosauriformes, but Camarasdurus already has a ventraliy widened hyposphene, and advanced Titanosauriformes,
258 .
Sebastidn Apesteguia
t DtD db& basal
eusauropod
basal
macronaraan
Patagosaurus Camarasaurus
W ww@w basal
iilanosauriform Brachiosaurus
basal
litanosaur Andesaurus
-
basal
saltasaurid
eutitanosaurs
Argentinosaurus Epachthosaurus Neuquensaurus
o'oou"
such as Andesaurws and Phuwiangosaurus, bear apparently plesiomorphic rhomboidal hyposphenes.
The family Andesauridae, including Andesaurus, Argentinoslurus, and Epachthosaurus, supposedly share the hyposphenehypantrum accessory articulation, a character not seen in other titanosaurs, plus other features in the pleurocoels of the centra. Although Andesawrus (MUCPv 132) bears hyposphenes, this is not true for Argentinosaurws, where the presacral vertebrae (PVPH 1' Fig.1,2.6D, E), only show a system of hyposphenal bars formed by hypertrophy of the medial centropostzygapophyseal laminae (Bonaparte 1999). These structures originated from the strong lateroventral expansions of typical sauropod hyposphenes (e.g., Patagosaurws Bonaparte 1986; Bonaparte and Coria 1993). This bifid structure, or "hyposphenal bars," of basal eutitanosaurs are formed by both medial centropostzygapophyseal laminae, variably reinforced but always doubled, descending from the center point where postzygapophyses split, leaving a gap between them. As expected, the external walls of the medial centropostzygapophyseal laminae would fit in a hypantrum, the central cavity between both prezvgapophyses (Fig. 12.7C).If these hyposphenal bars formed by
Fig. 12.5. Cladogram shouing the different euolutionary paths of tbe hypospbenes and related lammae
(modified from Osborn and Mook 1921; Bonaparte and Coria 19 9 3 ). P hylogenetic analy sis consistent with Salgado et al. (1997) and.V/ilson (2002), among others.
medial centropostzygapophyseal laminae actually represent the Iateral borders of the complete but hollowed, primitive hyposphenes seen in Phuwiangosaurus or Andesaurus, this would mean a functional continuity among basal titanosaurs and derived saltasaurids. The hypertrophy of the Argentinos*urus "hyposphenal bars" may correlate to the increase of body size and provide a more solid, but not rigid, intervertebral connection (Bonaparte and Coria 1993). The paraplastotype of Epachthoslurus sciuttoi shows hyposphenal bars that resemble those seen in Argentinosaurus. However, they are not present in the holotype specimen, and the paraplastotype should be considered the type of another species. In those titanosaurs that have lost the hyposphenes, the medial centropostzygapophyseal laminae remain present but less developed than in ArEvolution of the Hyposphene-Hypantrum Complex
.
259
;.
') 1
._+_-
mcpol
//I Fig. 12.6. Titanosaur dorsal uertebrae in posterior uiew: (A) Phuwiangosaurus sirindhornae (from Martin et al. 1999); (B) Andesaurus delgadoi (fron Salgado 2001); (C) Eucamerotus foxi (modified from Hulke 1880); (D-E)Argentinosaurus huinculensis (modified from Bonapdrte and Coria 1993); (F) Saltasaurus loricatus (modified from Powell 2003); (G) neural arch of a basal titanosaur from the Aptian of Centdl Patagonid (from Apesteguia dnd Gimdnez in prep.); (H) Mendozasaurus neguyelap (from Gonzdlez Riga 2003); [l Opisthocoelicaudia skarzynskii (from Salgado 2001). Abhreuiations: mcpol = medial c e
260
.
Sebasti6n Apesteguia
n f ro
po st 4' 8d p
up
b\'sea I lam
in
a.
,1 r:
\ .i
.,i{ t,{
t:
l'
Fig. 12.7. Sauropod dorsal uertebrae in anterior uiew showing
h1'pantra: 1A/ Dicraeosaurus sattlerr (from .lanensch 1929; pl. V,
fig.
4t1 1Bl
Aplro:aurus loui>ae
(frctm Gilmore 1936; pl. XXV, fi1. 6/; /C/ Apatosaurus ercelsus (from Cilmore 1936; pl. XXXII, fis. 8); (D)Amphicoelias altus (from Osbom and Mook 1922; pl. 119, fiS.a); (E) Barosaurus lentus (from Lull 1c)19; pl. IV fi4. a); (F) Camarasaurus supremus (from Osborn and Mook 1922; pl. LXXI, fis. e); G) Camarasaurus grandis (from Ostrom dnd Mclntosh 1966; fig. 23). Abbreuiations: hylta = bt-pdtttrum.
gentinosauras. From the ventrolateral ends of the hyposphene originate thin, medial centropostzygapophyseal laminae, or ,,infrahyposphenal laminae," extending ventrally. Similar laminae can be observed in a basal titanosaur (Fig. 12.6G) from Chubut (Apesteguia and Gim6nez 2001). Salgado et aL (1997) defined the Titanosauridae as the clade including the most recent common ancestor of Epachthosawrus sciutEvolution of the Hyposphene-Hypantrum Complex
.
261
toi, Maldwisaurus dixeyi, Argentinosaurus huinatlensis, the titanosaur DGM
*B' from Periopolis,
Opisthocoelicaudia skarzyn-
skii, Aeolosaurus rionegrinus, Alamosaurus saniuanensis, and Saltasaurinae and all of its descendants. Within this clade, the basal
forms are known to have some kind of accessory structure on the dorsal vertebrae that were once mistaken as hyposphenes. As said before, true hyposphenes are not present within this group of derived titanosaurs, the Eutitanosauria (Sanz et aL 1999). The disappearance of hyposphenes from the titanosaur lineage could be related to other processes, such as the dorsoventral shortening of the neural arch (Tidwell, pers. comm.). Discussion Bonaparte and Coria (1993) questioned if the condition in Argentinoscturus has phylogenetic implications, if it is associated with amphiplatyan caudals, if it is associated with the early development of procoelous caudals, or if it was just a functional solution to the extreme body size. The presence of a true hyposphene-hypantrum complex does correlate with those taxa having amphiplatyan caudals (e.g., Andesaurus), because they are both plesiomorphic features for eutitanosaurs, as are broad teeth and phalanges in the manus. On the other hand, those titanosaurs with dorsal vertebrae lacking hyposphenes have procoelous caudals. In derived and chronostratigraphically late eutitanosaurs, such as Argyrosaurws, traces of posteroventral bony edges probably represent remnants of the structure that originated from the medial centropostzygapophyseal laminae. True hyposphenes are not present, however, within derived titanosaurs (except perhaps Ampelosaurus and Epacbthosauras), since loss of the hvposphene-hypantrum compler is characteristic of the group. Several Late Cretaceous sauropod lineages have independently lost the hyposphene-hypantrum articulation in the dorsal vertebrae (e.g., rebbachisaurids in the Diplodocoidea and titanosaurs in the Macronaria). This loss is accompanied by other convergent features that are plesiomorphic to several diverse clades (e.g., narrowcrowned teeth restricted to the anterior region of the snout, narial
retraction, square symphysis). The loss of the hyposphenehypantrum complex would have provided both unrelated taxa a higher mobility of the back. An explanation for these shared features is outside this work; however, the abundance of these convergences in unrelated taxa is remarkable.
Basal titanosaurs, such as Andesaurus and Phuwiangoslurus,
still bear the plesion-rorphic rhomboidal hyposphenes, whereas
a
new taxon from the Aptian sediments of Neuqu6n Province (Bona-
parte et al. submitted) shows
a bifid hyposphene, plus
well-
developed medial centropostzygapophyseal laminae or "infrahyposphenal ridges." The relative development of the hyposphenal bars seems to be related to the vertebral shape. Riggs (1904) noted that there was a relationship between the 'n'
e (ehacti4n
'Ane.rer 'r ''' 'JUIX
height of the neural spines, the breadth of the zygapophyses, and the hyposphene structur e. In Camardsaurus, the postzygapoph.vses are moderately broad, but are nowhere placed far apart, whereas
the hyposphene is relatively large. In Brdchiosaurus, the
zygapophyses are reduced and crowded together near rhe midline. The hyposphene-hypantrum complex is well developed, prevenring
'Within
any lateral displacement of the body. the Titanosauria, rhe vertebrae are rather wide and low, and accordingly they have more widely separated prezygapophyses when compared to the tall vertebrae in other clades. This becomes evident when comparing diplodocoid sauropod dorsal vertebrae with Opisthocoelicaudia and Argentinosdurus. In Saltasaurrs, posrzygapophyses are wider and closer to the midline (as in Apatosaurus), but they lack hvposphenes. Although Brachiosauras has relatively wide posterior dorsal vertebrae, these have very reduced, cup-like postzygapophyses. The neural arch MPEF-PV 1133 (Fig. 12.6G), belonging to a basal titanosaur (Apesteguia and Gim6nez 2001), shows a complicated arrangement formed by a pendant structure, with a constrained base and a rather flattened, basally erpanded hyposphene, which bears a smaller additional structure at the end. From the lateral margins of the hyposphene, two hyposphenal ridges (medial centropostzygapophyseal laminae) are developed lateroventrally to meet each other around the neural channel. Straight, tall, and parallel columns reach the postzygapophyses at the middle (centropostzygapophyseal laminae). The meeting of both extrahyposphenal columns close a small, peri-hyposphenal fossa.
Life without Restrictions: Paleobiological Significance of Hyposphene-Hypantrum Loss Although the hyposphene-hypantrum complex was presenr in primitive sauropods, this probably allowed them to acquire a large body size by stabilizing the vertebral column. However loss of the hyposphene-hypantrum complex occurred independently in the Late Cretaceous rebbachisaurid diplodocoids and titanosaur macronarians, and reached its maximum loss in saltasaurines. The Ioss allowed greater flexibility of the vertebral column (V/ilson and Carrano 1999). Basal titanosaurs such as Argentinosdurus and Epachthosaurzs developed a new kind of accessory structure, probably from the remains of the bifid hyposphene plus a part of the medial centropostzygapophyseal laminae, forming strong "hyposphenal ridges." In advanced eutitanosaurs, no hyposphenehypantrum complex is present. In addition, they developed light camellate vertebrae, a skeleton rvith articulations vastly replaced by cartilage and other calcified tissues, and r,vide iliac blades for locomotor muscles. These adaptations allowed them to have a relatively free and rapid locomotion, despite bearing dorsal scutes. Even in the tail, there is a trend toward the reduction of caudal accessory articulations, especially in titanosaurs. This loss results in
a
greater mobility
of the tail and
supporrs the use
of
the
Evolution of the Hyposphene-Hvpantrum Compler
.
263
"whiplash" tail as a weapon in derived titanosaurs. This suggestion was presented by \X/ilson et al. (7999), based on the development of a procoelic anterior to the mid-caudal vertebrae; the rod-shaped, biconvex distal vertebrae; and the biconvex last sacral (Salgado et al. submitted), rvhich allowed maximum mobility of the tail. Furthermore, increasing the lateral projection of the iliac blades would have also allowed improved control of the tail. All of these specializations in titanosaurs are better understood by considering the growing importance of angiosperms in the Late Cretaceous, and the relatively low ornithischian diversity in the South American and perhaps Gondwanan terrestrial ecosystems during this time. Acknowledgments. My thanks to Leo Salgado for advice and friendly "sauropod talks"; Jos6 F. Bonaparte for encouragement to follow the "wide gauge" of sauropod evolution; Pablo A. Gallina for hearing and restraining an easily flying mind; Fernando E. Novas for support and trust at my beginnings on sauropod studies; Virginia Tidwell for encouraging me to publish; Kristy Curry and Ray Rogers for very useful talks and friendship; Jaime Powell for access to Lillo Institute specimens; and Pablo Puerta for giving me the chance to study an Aptian sauropod from Chubut. To Virginia Tidwell and Kenneth Carpenter, thanks for their help, especially with the writing style of this chapter. Thanks also to Eva L6pez for help in illustration processing, and to the Jurassic Foundation and PaleoGenesis for field support. References Cited
Apesteguia, S., and O. Gim6nez. 2001. A titanosaur (Sauropoda) from the Gorro Frigio Formation (Aptian, Lower Cretaceous), Chubut Province, Argentina. Ameghiniana 37(4\ Suplemento: 4R. Bonaparte, J. F. 1986. Les Dinosaures (Carnosaures, Ailosaurid6s, Sauropodes, C6tiosaurid6s) du Jurassique Moyen de Cerro C6ndor (Chubut. Argentina). Annales de Pal1ontologie 72: 325-386. 1999. Evoluci6n de las v6rtebras presacras en Sauropodomorpha. Amegh iniana 36(2): fi 5-187. Bonaparte, J. F., and R. A. Coria. l993.Un nuevo y gigantesco saur6podo titanosaurio de la Formaci6n Rio Limay (Albiense-Cenomaniense) de la Provincia del Neuqu6n, Argentina. Ameghiniana 30:271,-282. Bonaparte, J. F., \(/.-D. Heinrich, and R. !7i1d. 2000. Revierv ol lanenschia \7i1d, with the description of a new sauropod from the Tendaguru beds of Tanzania and a discussion on the systematic value of procoelous caudal vertebrae in the sauropoda. Paleontograpbica A.256:
25-76. Borsuk-Bialynicka, M. 1977. A new camarasaurid sauropod Opisthocoelicaudia skarzynskii, gen. n., sp. n. from the Upper Cretaceous of Mongoha. Pdleontologia Polonica 37: L-64. Calvo, J. O., and J. F. Bonaparte. 1,99I. Andesaurus delgadoi gen. et sp. nor,-. (Saurischia-Sauropoda), dinosaurio Titanosauridae de la Formaci6n Rio Limay (Albiano-Cenomaniano), Neuqu6n, Argentina. Ame ghiniana 28: 303-3 1 0. Calvo, J. O., and L. Salgado. 1995. Rebbachisaurus tessoneisp.nov. a new
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Sebastidn Apesteguia
Sauropoda from the Albian-Cenomanian of Argentina: New evidence on the origin of Diplodocidae. GAIA 11: 13-33. Dalla Vecchia, F. 1998. Remains of Sauropoda (Reptilia, Saurischia) in the Lo-"ver Cretaceous (Upper Hauterivian-Lou,er Barremian ) Limestones of SW Istria (Croatia). Geologia Crc,tdtica 51(2): 105-134. Gauthier, J. A. 1986. Saurischiar.r monoph,vly ar.rd the origin of birds. In K. Padian, eds., The Origin of Birds and the Euolution of Flight, 1-55. N{ernoirs of the California Academy of Sciences, no. 8. San Francisco:
California Academ,v of Sciences. Cilmore, Charles. 1936. Osteologv of Apatctsaunts with special reference to specimens in the Carnegie N1useum. Memoirs of the Cdrnegie Mu-
seumll:175-300.
Gonz6lez Riga, B. l. 2003. A new titanosaur (Dinosauria, Sauropoda) from the Upper Cretaceous of Mendoza Province, Argentina. Azeghiniana 40(2): I 5 5-772. Hatcher, J. B. 1901. Diplodocus Marsh: Its osteologv. taxonomy and prob-
a restoration of the skeleton. Memoirs of the Carnegie Museurn 1: 1,-63. Hatcher, l. B. 1906. Osteolog,v of Hapktcanthosaurus, rvith a description of a new species, and remarks on the probable habits of the Sauropoda and the age and origin of the Atlantosaurus beds. Memoirs of the Carnegie Museum 2(7): 1-7 5. able habits, with
He X., Li K., Cai K., and Gao Y. 1988. The Middle Jurassic Dinosaur Fauna from Dashampu, Zigong, Sicbudn.Yol. 4: Sauropod Dinosaurs (2), Omeisaurus tianfuensis. Chengdu: Sichuan Scientific and Technological Publishing House. Hulke, J. 1880. Supplementar,v note on the vertebra of Ornithopsls (See-
ley) = Eucdmerolas (Hulkel. Quarterly Journdl of the Geolctgical Society 36: 31-34. rWinkler, $7. R. Downs, and E. Gomani. 1993. New Jacobs, L. L., D. A. material of an Early Cretaceous titanosaur from Malawi. Palaeontology J6t3):521-ii4. Jain, S. L., and S. Bandyopadhya,v. 1997. New titanosaurid (Dinosauria: Sauropoda) from the Late Cretaceous of Central India. lournal of Vertebrate Paleontolctgy 17 : 114-136. Jain, S. L., T. S. Kuttl', T. Roychowdhury', and S. Chatterjee. 1977. Some characteristics of Barapasattrus tagorei, a sauropod from the Lower Jurassic of Deccan, lndia. In IV International Gonduana Symposium, Calcuttd, India, 204-216. Delhi: Hindusran Publishing Co. 'W. 1929. Die Wirbelsauleder Gattung Dicraeosaurtts. PalaeonJanensch, tographica, supp. 7(2): 37-133. 1950. Die Wirbelsaule von Bracbiosaurus brancai. Palaeontogrdphicct,supp. 7(3): 27-93 (Stuttgart). Lavocat, R. 1954. Sur les dinosauriens du Continental intercalaire des Kem-Kern de la Daoura. Comptes Rendus de la Dix-Neuuiime Sessiort, Congris G1ologique International, Alger. ASGA 21:65-68. Le Loeuff, J. 1995. Ampelosaurtts atacis (nov. gen, nov. sp.), un nouveau Titanosauridae (Dinosauria, Sauropoda) du Cr6tac6 Sup6rieur de la Haute Vallde de I'Aude (France). Comptes Rendus de I'Academie des Sciences de Paris, serie I,321: 693-699. Lull, R. S. 1919. The sauropod dinosaur Barctsaurtts Marsh. Memoirs of the Connecticut Academy of Arts and Sciences 6: I-42. Martin, V., E. Buffetaut, and V. Suteethorn.1994. A new genus of sauropod dinosaur from the Sao Khua Formation (Late Jurassic or Early
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Cretaceous) of northeastern Thailand. Comptes Rendus de I'Academie des Sciences de Paris 319, s6rie II: 1085-1092. Martin, V., V. Suteethorn, and E. Buffetaut. 1999. Description of the type and referred material of Phuwiangosaurus sirindhornae, a sauropod from the Lower Cretaceous of Thailand. Oryctos 2: 39-91,. Martinez, R., O. Gim6nez, J. Rodriguez, and M. Luna. 7991. Un titanosaurio articulado de1 g6nero Epachthosauras de la Formaci6n Bajo Barreal, Cret6cico del Chubut. Ameghiniana 26(3-41:246. Osborn, H. F., and C. C. Mook. 1,921,. Camarasaurus, Amphicoelias, and other sauropods of Cope. Memoirs of the American Museurn of Natural Histort, 3: 24--387. Ostrom, J. O., and J. S. Mclntosh. 1966. Marsh's Dinosaurs: The Collections from Como Bluff. New Haven, Conn.: Yale University Press. Powell, J. E. 2003. Revision of South American titanosaurid dinosaurs:
Palaeobiological, palaeobiogeographical and phylogenetic aspects. Records of the Queen Victoria Museum 111 (Launceston). Ratkevich, R. 1998. A new Cretaceous brachiosaurid dinosaur frorn southern Arizona. Journal of the Arizona-Neudda Academy, of Science
31(1):71-81.
Riggs, E. S. 1904. Structure and relationships of the opithocoelian dinosaurs. Part 2; The Brachiosauridae. Field Columbian Museum of' Geology 2:229-248.
Salgado,
L. 2003. Paleobiologia y
Evoluci6n de los saur6podos Ti-
tanosauridae. Thesis, Universidad Nacional de La Plata. Salgado, L., and R. Martinez. 1993. Relaciones filogen6ticas de los titanos6uridos basales Andesaurus delgadoiy Epachthosaurussp. Amegbiniana 30(3 ): 339. Salgado, L., R. A. Coria, andJ. O. Calvo. 1997. Evolution of titanosaurid sauropods. I: Phylogenetic analysis based on the postcranial evidence. Ameghiniana 34 3-32. Sanz, J. L., J. E. Powell, J. Le Loeuff, R. Martinez, and X. Pereda Suberbiola. 1,999. Sauropod remains from the Upper Cretaceous of Lafro (Northcentral Spain): Titanosaur Phvlogenetic Relationships. Estudios del Museo de Ciencias Naturales de Alaua 14 (Ndm. Esp. 1): 23 5-25
5.
Upchurch, P. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of tbe Linnean Society 124 43-703. 1999. The phylogenetic relationships of the Nemegtosauridae. Journal of Vertebrate Paleontology 19 706-1,25. 'Wiison, J. A. 1999. A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs. Journal of Yertebrate Paleontolctgl' 19(4\: 639-653. 2002. Sauropod dinosaur phylogeny: Critique and cladistic analysis. Zoological Journal of the Linnedn Society 136 277-276.
\filson,
J. A., and M. T. Carrano. 1999. Titanosaurs and the origin of "wide-gauge" trackways: A biomechanical and systematic perspecrive on sauropod locomotion. Paleobir.tlogy 25(2): 252-267. Vilson, J. A., R. N. Martinez, and O. Alcober. 1999. Distal tail segment of a titanosaur (Dinosauria) from the Upper Cretaceous of Mendoza, Argentina. Jottrnal of Vertebrate Paleontology 19(31: 59I-594. Wilson, J. A., and P. C. Sereno. I998. Early evolution and higher-level phylogeny of sauropod dinosaurs: Memoir 5. Journal of Vertebrate Paleontology 18 (supp., no.2): 1-68. rWilson, A., and P. Upchurch. 2003. A revision of Titanosaurzs Lydekker J.
266 . Sebastiln
Apesteguia
(Dinosauria-Sauropoda), the first dinosaur genus with a "Gondwanan" distribution. lournal of Systematic Palaeontology 1(3):
125-160. Young, C. C. 1954. On a new sauropod from Yiping, Szechuan, China. Scientia sinicd 3: 491-503. Zhang Y. 1988. The Middle Jurassic dinosaur fauna from Dashampu, Zigong, Sichuan. Journal of the Chengdu College of Geology, supp. 2:
r-12.
Evolution of the Hyposphene-Hypantrum Complex
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267
"1.3.
Yariation in the Appendicular Skeleton of North American Sauropod Dinosaurs:
Taxonomic Implications D. Rev \Trrnrrn
Abstract Morphological variation in the appendicular skeleton (exclusive of the manus and pes) of North American Upper Jurassic Morrison sauropods was examined in detail in order to determine the range of variation, and to identify taxonomically significant characters within the appendicular skeleton. A clear understanding of morphology and morphological variation within raxa is essential for both phylogenetic and morphometric analvses. The scapulocoracoid, humerus, ischium, and femur were found to be the best elements for taxonomic identification at the generic level, but given good preservation any appendicular element may be identifiable at some significant taxonomic level. Aithough a clear understanding of morphological variation is essenrial to assessing the value of morphological characters, very little is known about variation in all but three tara examined (Apatosaurus, Diplodocus, and Camarasaurus) and care should be taken when using morphological characters of the appendicular skeleton to identify taxa.
268
Introduction Historically, sauropods have been classified and described based primarily on axial elements (Mclntosh 1.990a, 1990b), but recent cladistic analyses have focused much more on the appendicular skeleton (Upchurch 1995;'Wilson and Sereno 1998). However, no comprehensive comparison of morphological diversity in the sauropod appendicular skeleton exists. This study is a first step toward a comprehensive guide to sauropod appendicular material. This paper describes in detail the morphology of the sauropod appendicular skeleton, as well as the morphological differences among the most common North American sauropod genera. Specifically, I will focus on the fauna of the Upper Jurassic Morrison Formation of western North America because the Morrison sauropod assemblage is the most diverse and plentiful currently known. One major difficulty in identifying disarticulated sauropod specimens is the presence of large, multigeneric bonebeds. One such bonebed is represented by the Dry Mesa Quarry in 'uvestern Colorado, in which as many as eight genera of saurpods are present (Curtice and'Wilhite 7996). 'Within the deposit almost every bone is disarticulated and unassociated. Initial studies of the Dry Mesa Quarry by the author revealed the necessity of a "guide" for the identification of isolated iimb bones, since isolated elements are virtually useless if they cannot be assigned to at least the generic level. Understanding morphological variation in individual sauropod appendicular elements is also important for studies of ontogenetic variation, functional morpholog"v, and phylogeny because few associated or complete sauropod skeletons exist. Studies of ontogenetic variation in sauropod limbs would lack significant sample sizes if only articulated or associated skeletons were required (Wilhite 1999). Wilhite (2003b) relied heavily on well-preserved, undistorted limb bones that rvere digitized to examine functional anatomy of the appendicular skeleton. The project would have been impractical without the use of isolated, weil-preserved elements to complement missing elements in associated or articulated specimens. Phylogenetic analyses would be greatly improved if characters based on individual specimens could be documented in isolated elements as well. Therefore, an understanding of variation within individual elements aliows the use of isolated elements to increase sample sizes and improve the overall quality of a given proj-
Institutional abbreuiations. AMNH-American Museum of Natural History, New York, New York; BYU-Brigham Young University Earth Science Museum, Provo, Utah; CM-Carnegie Museum of Natural History, Pittsburgh, Pennsylvania; DNM-Dinosaur National Monumenr, Jensen, Utah; FMNH-Field Museum of Natural History, Chicago, Illinois; KUVP-University of Kansas, Lawrence, Kansas; M\7C-Museum of 'Western Colorado,
Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
269
Fruita, Colorado; SDSM-South Dakota School of Mines, Rapid CitS South Dakota; UUVP-University of Utah, Salt Lake CitS 'Wyoming, Utah; UW-University of Laramie, Wyoming; WDCWyoming Dinosaur Center, Thermopolis,'Sfyoming; YPM-Yale Peabody Museum, New Haven, Connecticut.
Materials and Methods Genera examined include Camarasaurus (Cope 7877), Apatosdurus (Marsh 7877), Diplodocus (Marsh 1878), Barosaurus (Marsh 1890), Brachiosaurus (Riggs 1903a), and Haplocanthosaurws (Hatcher 1903a). Unfortunately, reasonable sample sizes of individual elements (N > 10) are only available for three of these genera: Cdmarasaurus, Apatosaurus, and Diplodocus. Sufficient data for Brachiosaurzs is available from African specirnens; however, the amount of morphological variation between the African species, B. branchi (Janensch 1,974), and its North American counterpart, B. altithorax (Riggs 1903a), is not clear, and I have chosen not to attribute the characters of B. branchi to B. altithorax. Currently, manuscripts on both Bdrosaurus (Mclntosh, this volume) and Haplocanthosaurus (Bilbey and Hall, in prep.) are in preparation that will add much to our understanding of the morphology of these two genera. A recently discovered species of Apatosattrus, A.
ydhnahpin (Filla and Redman 1994), from the Lower Morrison Formation of Wyoming, will be cited frequently as an example of interspecific variation. The following sections focus on the six major limb elements (humerus, radius, ulna, femur, tibia, and fibula) and the six girdle elements (sternal, scapula, coracoid, ilium, ischium, and pubis). Each section begins with a general description of an element. Muscle scars were named based on dissections of numerous specimens of Alligator mississippiensls. The specific explanations and rationale for the naming of various muscle scars, as lvell as detailed descriptions of the corresponding structures in Alligator, can be found in Wilhite (2003b). Next, morphological differences among genera are described in detail. Many elements are defined based on robustness relative to other taxa. The measurements used to define relative robustness in each taxon can be found in \X/ilhite (2003b). Except where noted, it is impossible to distinguish appendicular material at the species level. The importance of each element as a taxonomic indicator based on the morphological differences nored in this study is also assessed. Approximately one hundred elements from twelve different institutions were digitized using an Immersion Microscribe threedimensional digitizer. Criteria used to select individual bones for digitizing and digitizing methods are given in Y/ilhite (2003a). Dig, itized elements rvere assembled by Arthur Andersen of Virtual Surfaces and articulated using Discreet's 3D Studio Max modeling software. Observations and measurements of over five hundred additional limb elements were also collected (see Wilhite 2003b).
270.
D.Ray\(ilhite
Measurements and observations were made of any appendicular element for which length could be determined. Additional measurements of the forelimb and hindlimb bones included: greatest proximal breadth, least breadth, greatest distal breadth, and least circumference. These measurements were made according to the guidelines presented in'Vfilhite (1,999).
Carpenter and Mclntosh (1994) noted that juvenile Apdtosdurus humeri were proportionally similar to adult specimens. Wilhite (1999) demonstrated that limb elements in Camarasdurus exhibit isometric growth patterns. Further measurement of numerous limb elements of Apatosaurus and Diplodocus weli supports an interpretation of isometric growth in these taxa ('Wilhite 2003b), and morphological differences within and across taxa are unrelated to size. Therefore, figures were generated and scaled to the same length using three-dimensional models of digitized elements (see \X/ilhite 2003a for digitizing technique). The advantage of using digitized elements is that bones can be placed in a precise orientation that is easily duplicated. Digitally generated figures also can be scaled and transformed so that all views are of the same size and side.
The Pectoral Girdle Sternal. The sternal in sauropods is a medial paired element situated between the coracoids (Fig. 13.1).It is generally broadly flattened with a dorsoventrally expanded anterior end (Fig. 13.1B).
Anterior
Anterior
Fig. 1 3.1 . Digitized Camarasaurus (VrDC BS-104) left sternal (length = 527 mm): (A) dorsal uietu; (B) lnteral uieu : tC) uenlral uiet,.
Anterior
Lateral
Medial
I I I
__J B Posterior
Posterior
Posterior
Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
271
Anterior
j],,t::.:rt::.)1:::,.::t:::,,:.:.:.:,:tt"l
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Posterior
The anterior, posterior, and medial borders of the sternal are rugose and imbedded in cartilage in life. The lateral border of the sternal, however; is smooth and may have had a thin, but dense, cartilage covering, forming a tight joint with the coracoid. There is some debate as to the actual orientation of the sternal plates and their position relative to the coracoid. Filla and Redman (1994, fig. 10) illustrate a cartilaginous presternum, which is shown as three quarters of the length of the ossified sternals in a \Tyoming apatosaur. This restoration is in keeping with the hypothesis of Bakker (1987, fig. 13) that the scapulacoracoid was mobile in quadrupedal dinosaurs, increasing the arc of rotation of the forelimb. However, the true ex-
tent of the cartilaginous presternum is unknown. Figure
13.2
shows a pair of articulated sternals from Dinosaur National Monument with the orientation assumed here in the descriptions of the various genera that follow. The sternal plates of diplodocids and camarasaurids are distinct from one another. In general, the diplodocid sternal is relatively short and massive, whereas the camarasaurid sternal is elongate and gracile (Fig. 13.3).'S7ithin the diplodocids, the sternum of
Apatosaurus is more robust than that of Diplodoctts (Fig. 13.3A-D); however, the shape of the sternals is variable within genera. This may be due to the cartilaginous nature of the majority of the sternum, with the observed variation represenring different levels of ossification throughout ontogeny. The morphology of a juvenlle Diplodoczzs sternal in the collections of the Brigham Young University Earth Science Museum, BYU 681*12534 (Fig. 13.48) differs greatly from that of an adult Diplodocus in the collections
272.
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re
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Posterior Anterior
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Fig. 13.3. Digitized sduropod right sternals (not to scale). Apatosaurus (BYU 681-4600) in (A) uentral uietu and (B) Iateral uiew, Drplodocts (AMNH61 5 ) in (C) uentral uietu and (D) lateral uie*', and Camarasaurus /WDC BS-104) in (E) uentral uieu and (F) lateral uiew.
of the American Museum of Natural History, AMNH 615 (Fig. 13.4A). Similar ontogenetic differences are observed between the juvenile Camarasauras, CM11338, and the adult specimen, \7DCBS 104.
Coracoid. In sauropods, the coracoid is a square to oval element whose posterior margin is joined to the scapula (Fig. 13.5). The dorsal and anterior borders of the coracoid are thin, but the element thickens posteroventrally. This posteroventral surface forms the anterior portion of the glenoid fossa, and a coracoid foramen is usually located near the element's posterior edge. In all Morrison genera, the coracoid foramen has a closed posterior border in adult specimens, but juvenile Apatosaurus specimens from the Cactus Park Quarry in northeastern Utah show that the posterior border of the coracoid foramen was not closed early in ontogeny in at least one taxon. Fusion of the coracoid to the scapula is related to ontogeny, and none of the juvenile Apatosaurzs scapulae from Cactus Park have fused scapulocoracoids. The coracoids probably articulated with the sternals based on the curvature of the lateral margins of the sternals (Wilhite 2003b). The anterior edge of the coracoid is curved medially, and the anterior edges of the coracoids probably lay close to one another in life, with the pectoral girdle wrapped around the front of the thorax.
The coracoid of Apatosaurus lFig. 13.6) is the most distinct morphologically of the common Morrison genera, featuring a squared anterodorsal margin, compared to the coracoid of Camdrasaurus, which has a rounded anterodorsal margin. The most notable feature of the Diplodocus coracoid (Fie. 13.7A) is the low Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
273
Medial
Anterior
A.
Posterior
Lateral 20 cm
Medial
Anterior
Posterior
B. Fig. 1 3.1. Photograph oi right sternals o/ Diplodocus in uentral uiew: (A) 615: iB) BYU 681-12531.
271
.
D. Ray Wilhite
AMNH
,,
ct'
ol A.
B.
:
Not preserved ,Flg. /3.-i. Digitized rigbt coracoid
o/Camarasaurus /KUVP 129714) in (A) lateral, (B) posterior, dnd (C) tnedial uiews (length = 255
mnl. Abbreuiations: cf = coracoid foratnen, gl = glenoid fossd.
A 20 cm
Anterior
B. 20 cm
Fig. 13.6. Photograph of Apatosaurus right coracoid (BYU 681-4599) in (A) ldteral and (B) medial uietus. Abbreuiations: cf = coracoid foramen, gl = glenoid fossa.
Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs . 275
\
glenoid
Fig. 13.7. Digitized sauropod rigbt coracoids in lateral uiew shotuing uariation in the angle of the scapular suture. (A)
Diplodocus (DNM 1028); (B) Apatosaurus (BYU 681 -4.t99) ; /C/ Camarasaurus l.KUVP 12e71 4).
Not Preserved
angle of the scapular articulation (-50') compared to the higher angle observed in Apatosaurus (Fig. 13.78) (-70') and the verrical
articulation observed in Camarasaurus \Fig. 13.7C).
Scapula. The scapula in sauropods is a massive element with a broad proximal end and a long scapular blade (Fig. 13.8). The distal end of the scapula is variably expanded. All sauropod scapulae have a prominent acromion ridge lying approximately perpendicular to the long axis of the scapula. The acromion ridge divides a large anterior fossa from a much smaller posterior fossa. The anteroventral surface of the scapula is laterally expanded to form the posterior surface of the glenoid fossa. The scapular portion of the glenoid fossa accounts for about two-thirds of the glenoid's total surface area. The cranial edge of the scapula articulates with the caudal edge of the coracoid. The scapula and coracoid fuse during ontogeny (\Tilhite 2003b). The life position of the scapula has been a source of much debate. Some authors have reconstructed the scapula as lying nearly vertical (> 60') against the ribs in sauropods (Riggs 1903b; Osborn and Mook 1919,7921 Hallett 1987). This arrangement leads to a posteriorly facing glenoid, which seems poorly suited for articulation with the almost vertically oriented humerus found in articulated specimens (Gilmore 1925; Bonnan 2001) (Fig. 13.9A). In
276
.
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Fig. 13.8. Digitized sauropod ight scapulae in lateral uiett. (A) Diplodocus (DNM 1028); (B) Apatosaurus (BYU 68 1 -1 061 8) ; f C) Camarasaurus (KU\zP 12971,4) (not to scale). Abbreuiations: af = anterin, fnsso. al = Ltcrotnion ridge, cs = corttcoid sttture, gf = glenoid fossa, pf posterior fossa, sb = scapular blade.
many restorations, the distal end of the scapula sits near the dorsal margin of the neural spines. This orientation leaves little room for the cartilagenous suprascapula indicated by the rugose distal ends of sauropod scapulae. The scapula was almost certainlv oriented more horizontally relative to the ribs (Fig. 13.98). Perhaps the best evidence of this more horizontal orientation is the articulated juvenrle Camarasaurus skeleton. CM 11338 (Gilmore 1925) from Dinosaur National Monument, Utah. The right scapula of CM 11338 appears to be only slightly displaced from its life position and lies -30' from horizontal. More recentln Parrish and Stevens (2002) have shown that apparent modifications in the ribs indicate a subhorizontal orientation for the scapula as well. While this is not definitive evidence, it is consistent with a near-horizontal orientation Variation in the Aooendicular Skeleton of North American Sauroood Dinosaurs
.
277
/ scapula _ q
@"Ph
,
glenoid fossa
- Fig. 13.9. Articulated digitized Camarasaurus (AMNH 664) (bwmerus length = 773 mm) Ieft forelimbs in lateral uieu. (A)
Articulated forelimb with scapula at -50" from horizontal. (B) Articulated forelimb with scapula at -28' from horizontal.
- -
humerusradius
A.
of the scapula in sauropods. Figure 13.9B represents the orientation assumed here for the scapula, with reference to the humerus, in the descriptions of the various genera that follow Scapula morphology is distinctive in sauropods. Apatosaurus scapulae can be distinguished from those of all known Morrison sauropods by the lack of a distally expanded scapular blade (Fig. 13.88) (Mclntosh 1990b). The distal end of the scapular blade in all other diplodocids (and all other known Morrison sauropods) is considerably expanded (Mclntosh 1,990b). The recently described Apatosawrus yahnahpin (Filla and Redman 7994), however, demonstrated that basal apatosaurs also had an expanded scapular blade. Diplodocids can be distinguished from Camarasaurus and Brachiosaunzs by the angle created by the scapular blade and the
acromion ridge (Mclntosh 1990b). In diplodocids the angle is acute, whereas in Camarasdurus and Brachiosaurus this angle is nearly 90' (Mclntosh 1990b). The anterior fossa in Diplodocus is the Iongest (anteroposteriorly), relative ro rhe length of the scapula, of any of the known Morrison genera (with the possible exception of Barosaunzs) (Fig. 13.8A). Camdrasaurzzs has a relatively massive scapula with a short blade and a much-expanded distal end (Fig. 13.8C) . Brachiosdurus has a scapula morphology similar to that of Camarasaurus; however, the scapular shaft is longer, with a thinner "waist" in the scapular blade just caudal to the acromion ridge. The described scapula of Haplocanthosaurus (Hatcher 1903b) resembles that of Camarasauras with the exception that the distal end of the scapular blade is equally expanded 278
.
D. Ray \Tilhite
dorsally and ventrally whereas tn Cdmarasaurus the blade is prima-
rily expanded dorsally. Forelimb Humerus. The humerus in sauropods is expanded both proximally and distally, with weak development of the distal condyles (Fig. 13.10). The head of the humerus is composed of an anteroposteriorly thickened central portion, which thins laterally and mediallS thus forming a raised triangular area on the caudal face of the humeral head (Fig. 13.108, D, F). This raised area articulates within the anteroposteriorly expanded glenoid fossa. The most prominent feature of the humerus is the large, laterally placed deltopectoral crest (Fig. 13.10A, C, E). The humerus is oriented so that the deltopectoral crest faces craniomedially. The distal end of the sauropod humerus is narrower than its proximal end, but the extent of narrowing varies among tara (Fig. 13. 10). The poorly defined distal condyles of the humerus are divided anteriorly by two small longitudinal intercondylar ridges (Fig. 13.10A, C, E) and posteriorly by a broad shallow anconeal (olecranon) fossa (Fig. 13.10B, D, F). The distal condyles of the humerus articulate with the lateral and medial processes of the ulna, with the radius lying directly beiow the intercondylar ridges on the humerus (Bonnan 2003:'S7ilhite 2003b).
The four key characters that help separate Apatosaurus, Diplodocus, and Camarasaurus humeri are overall robustness, proportion of the distal condyles, orientation of the anconeal fossa, and symmetry of the humeral shaft. ApatosAurus humeri are the
mc
C
"4*j4;
. .*te--6 €
-hh
1'
AF G
4drii E;
qP \#'-""" Ff,WX BAHi
*lc t ,.f .i" f
='€!,,'
:4&,8,,', lr
dnn
Fig. 13.10. Digitized sauropod left bumeri (not to scale). Apatosaurus (AMNH 6111) in (A) anterior uiew and (B) posterior uiew; Dtplodocus lBYU
68 l-4-42) in 1C) anterior uiew and (D) posterior uieu; and Camarasaurus (M\YC 2812) in (E) anterior uiew and (F) posterior
uiew. Abbreuiations: af = anconeal fossa, dpc = deltapectoral crest, hh = humeral head, ir =
intracondl,lar ridges, lc = Iateral condyle, mc = medial condyle.
Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
279
Anterior Posterior
Flg. 13.11. Digitized left radius of Drplodocus (BYU 681 -1726) It,tgth = {t,l mntt tn 1At posterior, lBt prctximal, (C) anterbr, and tDt rnedial uiews. Abbreuiation: uls = ulnd ligdment scdr.
most robust (Fig. 13.10A, B), whereas those of Diplodocus are the
most gracile of the three taxa (Fig. 13.10C, D). Cdmardsdurus humeri are intermediate between Apdtosaurus and Diplodocus (Fig. 13.10E). The anconeal fossa divides the distal condyles into subequal portions in diplodocids (Fig. 13.10A-D), but in Camarlsaurus the medial condyle is considerably larger than the lateral condyle (Fig. 13 . 108, F). In diplodocids, the shaft of the humerus is virtually straight in anterior vieq forming an hourglass shape (Fig. 13.1OA-D). Alternatively, Camarasaurzs exhibits a distinct bend in the medial shaft (Fig. 13.10E, F) due to the medially offset humeral head. Apatosaurus is both more robust than Diplodocus andhas a more prominent deltopectoral crest (Fig. 13.10A, C). The humerus of Brachiosaurus can be distinguished from all other North American Jurassic sauropods by its overall gracility alone (least breadth:length = 0.12) (Wilhite 2003). Radius. The sauropod radius is a relatively straight element (Fig. 13.11). The proximal end is triangular in shape, and the posteroprorimal border is contoured to fit into the anterior fossa of the ulna (Fig. 13.118). The radial shaft is gently borved in medial or lateral view so that the posterior aspect is slightly concave (Fig. 13.11D). The distal end of the radius has a distinct ulnar ligament scar on the posteromedial surface where the radius articulates with the ulna (Hatcher 1902; Gilmore 7936; Bonnan 2001) (Fig. 13.11A). Typicallg the distal end of the radius is rectangular in shape.
The radius is a very difficult element to diagnose at the generic level; however, some general trends can be noted. The radius of Apatosdurus (Fig. 13.12A, B) is the most robust of the three primary
280
.
D. Ray \Tilhite
-l
I I
Late
Medial
l .l
Latera
| ,,tJ
__.t
I
__l
l I
I
t
Med ra I
I
I I
_1,.
F
taxa, whereas the radius of Diplodocas (Fig. 73.12C, D) is the most gracile. Unfortunately', the robustness of the radius tn Cdmardsaurus (Fig. 13.12E, F) falls in between that of Apatosaurus and Diplodocus and, indeed, falls within the morphospace of both tara. Morphologically, all three taxa are very similar. The feature that has been considered to be the most useful character for distinguishing Camdrasawrus from the other taxa is its bowed radial shaft (\Wilson and Sereno 1998). However, this character is based on the diagenetically altered radius of YPM 1901 (Fig. 13.13A). Examination of numerous Camarasaurus radt, including P 25182 (Fig. 13.138), has demonstrated that they are no more bowed than the radii of any other North American Jurassic taxon (Wilhite 2003b; Bonnan 2001) (Fig. 13.12). Ulna. The ulna in sauropods is a robust element (Fig. 13.14). The proximal end is triradiate (Fig. 13.148) and composed of three
Fig. 13.12. Digitized sauropod left
radii (not to scale). Apatosaurus (BYU 681-1711) in (A) antertor uicw ond 1St posterinr uieu: Diplodocus (BYU 681-1726) in (C) anterior uiett,and (D) posterior uie*,; and Camarasaurus /AMNH ttt,l) itr ,E) anteriur Iietu and (F) posterior uiews. Abbreuidtion: trls = ulnar Iigament scar.
Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
281
Fig.13.13. Photograph of (A) YPM 1901, Camarasaurus /e/t radius in posterior uiew and (B) F
MNH
25 1
82, Camarasaurus
right radius in posterior uiew. Scale bar: 20 cm. Abbreuiation:
uls = ulnar ligament scar.
^a dl
rl0 ' I
,,r!riu:ll'lll:liii'lllllll!11tr,,,..
/' pp
/
I
B.
mp
Fig. 13.14. Digitized left ulna of Apatosaurus (BYU 681-471 9) (length = 510 mm) in (A) anterior, (B) proximal, (C) distal, and @) p
ostelior uiews. Ab br euiations
:
mp = medial process. a[= anlerior fossa, lp = lateral process, pp = posterior process, rls = radial ligament scar,
282
.
D. Ray\Tilhite
lp
/
mP
t:
processes (lateral, mediai, and posterior). The medial process is the longest of the three and articulates with the humerus so that it is
oriented anteromedially (Fig. 13.14B). The lateral process is usu-
ally thicker than the medial process and shorter overall (Fig. 13.148). The proximal end of the radius articulates in the anterior fossa (Fig. 13.14A, B) created by the lateral and medial processes of the ulna, so that proximally the radius is oriented cranial to the ulna (Bonnan 2001, 2003). The term "posterior process" is used here instead of the more common term "olecranon process" (i.e., Wilson and Sereno 1998), because the ulnae in ali North American Jurassic sauropods lack an olecranon process projecting dorsal to the articular surface of the ulna. The posterior process is the portion of the ulna posterior to the humerus. This process is triangular in shape and is angled caudoventrally in all the taxa discussed here (Fig. 13.14B, D). A prominent dorsal ridge, dividing the articular portion of the ulna (sloping cranioventrally) from the posterior process (sloping caudoventrally), is visible in lateral view (Fig. 13.15C, F, I). This ridge is analogous to the anconeal process of mammals and marks the caudal extent of the antebrachial joint so that the posterior process is not included in the antebrachial joint.
pp
Fig. 13.15. Digitized sauropod rigbt ulnae (not to scale). Apatosaurus (BYU 681-4719) in (A) anterior uiew, (B) proximal uieu, and (C) lateral uiew; Camarasaurus (AMNH 661) in
(D) d?Tteriol uiea (E) proximal uiew, and (F) lateral uieut; and Diplodocus (BYU 681-1726) in (G) anterior uiew (H) proximal uiew, and (I) Iateral uiew. Abbreuiations: IP = Iateral pr()cess, mP = medial ptocess, pp = posterior process, rls = radial ligament scar.
The ulnar shaft decreases in size below the ulnar Drocesses to the Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
283
pp?
qpp
Lateral
j
Fig. 13.16. Digitized right iliunt of Carnarasaurus lDNM I 253/ (length = .\50 mm) in (A) lateral, (B) dorsal, (C) dnterior, and (D) u entral uiew s. Ab br euiat ion s : acet = acetdbulttm, ip = ischiatic pedtrncle, ppd = pubic peduncle, ppp = prcacctobular process.
t
Lateral
c.
-\
'1
'ppd
\,'
acet'
D.
distalend of the ulna (Fig. 13.14C). A radial ligament scar located on the lateral surface of the distal end of the ulna indicates the distal articulation surface with the radius and corresponds with the ulnar ligament scar on the radius rvhen the two bones are articuIated (Fig. 13.14A). The shaft of the ulna has a triangular cross section and the distal end appears triangular when viewed from below (Fig. 13.14C). The main characters of the ulna that aid in taxonomic identification include overall robustness, orientation of the posterior process, size of the medial and lateral processes relative to one another, and development of the dorsal ridge. As with all other foreIimb elen-rents, the ulna of Apatosaurus is the most robust of all known Jurassic taxa (Fig. 13.16A-C). The ulnae of Cantarasaurus and Diplodocus are indistinguishable from one anorher based on robustness. Camdrasdwrzzs differs from all known diplodocids
in having a
posterolaterally directed posrerior process (Fig. 13.15D-F). In Diplodocus and Apatosdurus, the posterior process
without a lateral component. In Camarasaurus, the medial process is noticeably longer than the lateral process (Fig. 13.15H). ln Diplodoczs, both processes are nearly equal in length is directed caudally
(Fig. 13.15H). The dorsal ridge in Camarasaurzs is somewhat more prominent than in diplodocids (Fig. 13.15I). There are no described ulnae from North American Jurassic brachiosaurs, Haplo284
.
D. Ray \Tilhite
cdnthosaurus. For a description Mclntosh (this volume).
of the ulna in
Barr.tscturus, see
Peluic Girdle
Ilium. The ilium in sauropods is expanded both dorsallv and anteriorly, and has a prominent, preacetabular blade (Fig. 13.16). The pubic peduncle is elongate and gracile relative to the size of the ilium (Fig. 13.16A), and it is mediolaterally expanded (Fig. 13.16C, D). The ischiatic peduncle is poorly developed as a smail, rounded process at the posterior margin of the acetabulum (Fig. 13.16A). The ventral surface of the ilium forms the dorsal half of the acetabulum. The ventral surface of the ilium (dorsal surface of the acetabulum) is expanded medially to form a widened {lange (Fig.
13.16D). The dorsal border of the ilium is rounded and forms
a
gentle curve rvhich varies in height among taxa (Fig. 13.16A). In dorsal view, the preacetabular blade of the ilium curves iaterall;', creating a sacral profile that is wide anteriorly and narrow posteriorly (Fig. 13.168). A variable number of longitudinal ridges mark the sacral rib attachment points on the medial side of the ilium. The outer edges of the ilium are relatively thick, but the bone thins toward the center. Areas between the sacral rib attachments are only a few millimeters thick, and many ilia lack much of this surface due to poor preservation. Sauropod ilia differ generically primarily in the relative length of the pubic peduncle, relative height of the ilium, and the shape of the preacetabular process. The ilium of Camarasaurzs is the most distinctive of all the w'ell-known genera from the Morrison Formation. Based on personal observations, the pubic peduncle tn Camarasaurus is the longest of the known North American Jurassic sauropod taxa, with the exception of Brachiosaurus (Fig. 13.17C) (Mclntosh 1,990b\. The ilium ol Brachioscturus can be distinguished from that of Camarasaurus, however, by its erpanded preacetabular process and the high angle of its iliac blade (Mclntosh 1990b). Camarasaurus lha can also be distinguished from diplodocid and Haplocdnthosdurus ilia by the height of the iliac blade when measured from the dorsal border of the ilium to the dorsal border of the acetabulum (Hatcher 1903a). ln Haplocantbosaurus, the ilium is very low and the dorsal surface is almost straight (Hatcher 1903a). In diplodocids, the iiium is intermediate in height between that of Camarasdurus and Haplocanthosdurus (Fig. 13.17A, B). The preacetabular process in Camarasaurus rs
"hooked" ventrolaterally, while most diplodocid ilia have
a
straight, ventral, preacetabular border (Fig. 13.17). Ischium. The ischium in sauropods is posterior to the pubis and is directed caudally to caudoventrally. The proximal end of the ischium is composed of a dorsoventrally elongate iliac process thar articulates with the ischiatic peduncle of the ilium (Fig. 13'18). Just anterior to the iliac process, the anterior surface of the ischium flares laterally to form the posteroventral quarter of the acetabulum (Fig. 13.18A, C, E). The anterior surface of the ischium conVariation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
285
ppp
ppp
l t
,*l\
A.?
\
/
'-'"-.-\
9pp Fig. 13.17. Digitized sauropod right ilia in lateral uieu (not tct scale). (A) Apatosaurus /CM 21716); /B) Diplodocus /DNM
1018 ; (C) Camarasaurus /DNM 2; I . Ahbreuiatiuns: dce! = acetabulum, ip = ischiatic petluncle, ppd = pubic peduncle; PpP = predcetabular process.
tlooo
I
., vip
\/
!cet'
sists of an expanded flange that articulates with the posterior surface of the pubis, Posteriorly the ischium narrows to articulate with
its mates at the distal end, along the ventromedial distal articular surface (Fig. 13.18A, C, E).The distal end of the ischium is variably expanded dorsoventrally (Fig. 13.18A, C, E). Key features of the ischium include fusion of the distal ends of the ischia, expansion of the distal ends of the ischia, orientation of the ischial shaft, morphology of the cranial border of the ischium, and the angle of articulation of the distal ends of the ischia. In all diplodocids examined, the distal ends of the ischia are fused in adult individuals; however, the ischia are unfused in adult specimens of Camarasaurzs. \While the sample size is very small (-5), it would appear that fused ischia are common in Haplocanthosaurus (Mclntosh, pers. comm.). Diplodocid ischia have expanded distal ends (Fig. 13.18A, C), whereas in Camarasaurus, Haplocanthosaurus, and Brachiosdltrus, the distal end of the ischium is not expanded (Fig. 13.18F). The shaft of the ischium in diplodocids is directed caudoventrally (Fig. 13.18A, C), whereas jn CamarasAurus and Haplocanthosaurus the ischial shaft is rotated 90. relative to the prorimal end and directed posteriorly nearly parallel to the body axis (Fig. 13.18E). Diplodocid ischia are morphologically similar, and both Apatosaurus and Diplodocus have a hook-shaped process on the anteroventral margin of the pubic symphysis (Fig. 13.18A, C). The distal ischia of Apatosaurus and Diplodocws fuse at different angles, with that of Diplodocrzs fusing at an obtuse angle (-100'; Fig. 13.18D) and that of Apatosaurzs fusing at an
.
D. Ray \Tilhite
acet-
,,
ilF..r
right
A
B
sym
drt
acet \
,ilP't-
-z*
t .r(
oi)
right
':t,. :':tlr):
ilp
I
das
acet
,.ilp..-
1"/
t
a
right
pal
E
ohs
Fig. 13.18. Digitized sauropod ischia (not to scale). Apatosaurus (BYU 681-10687) (A) m right medial uiew and (B) articulated in posterior erler-a, Diplodocus /DNM 1227) (C) in right medial uiew and (D) articulated in posterior uiew; and Camarasaurus (UUVP 13.t0 [cast]) (E) in right medial uiew and (F) articulated in posterior uiew. Abbreuiations: acet = acetabulum, das = distal articular surface, ilp = i1io" peduncle, pa = pubic articular surface, sym = ischial symphasts.
Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
'
287
acute angle (.'80'; Fig. 13.188). The distal ischia of both Camar.tsaurus and Haplocantbosaurus meet in a symphysis along the medial edge of the distal shaft (Fig. 13.18F). In one diplodocid taxon, Seismosaurus, the distal end of the ischium is hook-shaped (Gillette 7991). Although this feature is cited as a generic charaiter (Giliette 1997), it seems more likely to be an ontogenetic effect due to the ossification of the prepubic cartilage in that individual because the outline of the original distal end of the ischium is evident in the figures of the bone (see Gillette 1991,\. Pwbis. The pubis in sauropods is located anterior to the ischium and is directed anteroventrally in all known sauropod genera. The prorimal end of the pubis is expanded mediolaterally and articuiates with the pubic peduncle of the ilium (Fig. 13.19).In diplodocids, the anterior margin of the pubis has a noticeable ambiens process (Fig. 13.19A, C). The posterodorsal border of the pubis forms the anteroventral quarter of the acetabulum. The obturator foramen is incorporated into the caudodorsal margin of the pubis (Fig. 13.194, C, E). Based on personal observations, the posterior margin of the obturator foramen is usually open in young individuals, but it is always closed in adults. The posterior margin of the proximal end of the pubis forms the arricular surface with the ischium (Fig. 13.19A, C, E). The shaft of the pubis is mediolaterally compressed and is much more massive than the ischial shaft. A flange of bone beginning below the articular surface with the ischium wraps around the shaft ventrolaterally to form an enclosed pubic "apron" (Fig. 13.198, D, F). The distal end of the pubis is greatly expanded relative to the pubic shaft with a roughly triangular cross section. A large, trianguIar, articular surface is present on the medial side of the distal end for articulation of the pubes (Fig. 13.19A, C, E). The main characteristics of the pubis useful for taxonomic differentiation include the presence or absence of an ambiens process, the shape of the ambiens process if present, and the relative size of the obturator foramen. Diplodocids are the only North American Jurassic sauropods that have an ambiens process (Fig. 13.19A., C) (Mclntosh 1990b). Diplodocus pubes have a hook-iike ambiens process and Apatosdurus has a rounded ambiens process. Haplocanthosdurus and Camarasaurus show no indication of an ambiens process on the pubis (Figs. 13.19E, 13.20). Haplocdnthoslurus, however, has a very large obturator foramen that distinguishes it
from Camarasaurus and diplodocids (Fig. 13.20).
Hindlimb Femur. The femur in sauropods is a massive, anteroposteriorly compressed bone (see beiolv for the exception; Fig. 13.21). The proximal end of the femur has a poorly defined head but iacks an anterior trochanter. A poorly developed fourth trochanter is located about one-third of the way down the femoral shaft on the posteromedial margin (Fig. 13.21B, C). The femoral shaft narrows beiow the fourth trochanter, reaching its narrowest point about two-thirds of the way down the femur. The distal end of the femur
288 . D. Ray \filhite
lPr I
of
I
amb/
ras
\/
-das p
lP'.
/o
{
amb'
ras
rrr.if
v
,.
.-\/
19
of
.-tipi.-.
Fig. 13.19. Digitized sauroPod pubes (not to scale). Apatosaurus (CM 563) (A) in righnnedial uiew artd tBt articulated in puslerior
rlear; Diplodoe u' iBYU o8ll)ql5' rCt in right medial uiew and rD) articttlated in posterior uieu; and Camarasaurus /UUVP 4939 [castl) (E) in right medial uiew and (F) articulated in ster i or uiew. Abbr euiations: anrb = ambiens process, das = distal articular sur[acc, ias = ischial art icrrlar surftcc. tp = ischiatic peduncle, of = obturator
p o
foramen.
is expanded mediolaterally and the distal condyles are expanded posteriorly (Fig. 13.21B). The lateral (fibular) condyle is the largest and has an intracondylar groove, which separates the lateral condyle into posterior and lateral subcondyles (Fig. 13.21C). The medial (tibial) condyle is smaller than the lateral condyle and lacks an intracondylar groove (Fig. 13.21C). The medial and lateral
Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
'
289
ras
Anterior
Posterior
Fig. 13.20. Photograph of left ub is of Haplocanthosaurus priscus (CM 10380) in lateral uieu. Abbreuiatioft: ids = ilial
p
articular surface.
20 cm
condyles are separated anteriorly by a weak intercondylar groove and posteriorly by a deep intercondylar groove (Fig. 13.21C). The diagnostic aspects of the femur include the shape of the femoral head, the robustness of the shaft, and the shape and relationship of the distal condyles. The two most difficult femora to tell apart among the common Jurassic taxa are those of Apatosaurus and Camarasdurus. Camarasaurzs has a more distinct femoral head than Apatosaurus (Bonnan 2001), and the distal condyles are perpendicular to the femoral shaft (Fig. 13.22G-I).
190
.
D. Ray Wilhire
fh
fh
1\
I
Posterior
Anterior
intra
ntc Apatosaurus lacks a distinct femoral head, and the medial (tib-
ial) condyle is longer than the lateral (fibular) condyle (Fig. 13.22A-C). An elongate tibial condyle is, in fact, characteristic of all known North American diplodocids (Foster, pers. comm.). The femur of Diplodocus is gracile relative to that of Apatosaurus and Camarasaunzs, but is very difficult to distinguish from that of Barosaurus (Fig. 13.22D-F). Wilson and Sereno (1998) contend that one diplodocid taxon, Amphicoelias, is characterized by having a circular femoral cross-section. However, my analyses of femora from the Dry Mesa Quarry of western Colorado shows that, in at least one quarry, approximately half of the Diplodocus femora have a circular or sub-circular cross-section. The most likely explanation for this observed ratio is sexual dimorphism, because there is no other evidence that more than one species of Diplodocus is present based on vertebral morphology, and no known Amphicoelia.s elements have been identified from the site
inter
"q
Fig. 13.21. Digitized right femur o/Diplodocus (BYU 681-17A14) tlength = 9SS mm) in tAt an7rrlor. (B) lateral, and (C) posterior uiews. Abbreuiations: fc = ltbular condyle, fh = femoral head, ft = fourth trochanter, inter = intercundylar groouc, inlra = intracondylar grooue, tc = tibial condyle.
(Curtice and \Tilhite 1,996). Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
291
:$ Fig. 13.22. Digitized sauropod right femora (not to scale). Apatosaurus (BYU 601-17103) in (A) anterior uiew, (B) ldteral uiea', and (C) posterior uieu; Diplodocus (BYU 681-17011) in (D) anterior uietu, (E) lateral uietu, dnd (F) posterior uiew; and
C.
D.
f
fb
lm:
/\
tc
tc
J-
Catnarasaurus ( cast of YP M 5723) in (C) anterior uie4 (H) lateral uieu, and (1) posterior uieu. Abbreuiatbns: fc = fibular ,;nnd1le. fh = fentural heod. Tt = fourth trochanter, tc = tibial condyle.
Tibia. The tibia in sauropods is quite massive relative to the fibula and articulates with the medial condyle and medial portion of the lateral condyle of the femur (Bonnan 2001) (Fig. 73.23). The proximai end of the tibia is broad and flat, tapering distally to a laterally compressed shaft. A prominent cnemial crest exrends from the proximomedial border of the tibia, beginning just distal to the proximal articular surface and ending about one-quarter of the way down the shaft (Fig. 1,3.23A, C, D, R G, I). The shaft of the tibia maintains a relatively constant width from the base of the cnemial crest to a point about three-quarters of the way dovvn the tibia, where the distal end starts to flare anteriorly as well as laterally. The distal end of the tibia consists of an anterior and a posterior process divided by a relatively broad lateral groove (Fig. 13.23B, E, H). The posterior process is the longer of the two, and the anterior process has a significant cranial expansion. The shape of the distal end of the tibia closely mirrors that of the dorsal surface of the astragalus with which it articulates. The best taxonomic indicators of the tibia include the size of the cnemial crest relative to the width of the proximal end of the tibia, the curvature of the shaft, overall robustness, and the shape of the distal end. The cnemial crest in diplodocids is proportionally larger than in Cdmarasaurus and Haplocantbosdurus (Fig. 1 3.23A, 'Within C, D, F). the diplodocids, Apatosawrws has the largest cnemial crest of all the North American taxa. In lateral view. the ante-
.
D. Ray Wilhite
ut' ;Medial--1
pp-red
lrd l
B
ial
ap
LiLateral--l
icc 1-Medial-i
ppiw: E I'i f"o
ap
L- Lateral-l
D.
I ap
Lateral
F. pp
pp'
t)..
Fig. 13.23. Digitized sduropod right tibiae (not to scale).
pp'
Apatosaurus (CM 556) in (A) lateral uiew, (B) distal t,iew, dntl (C) anterior llez,; Diplodocus (BYU 581-1718) in (D) Iaterdl t,iett', (E) distal uien, and (F) antetior uiet,; and Camarasaurus tYl\4 i6tr// in rC/ lttcral uicu. rHt distol t'iert', and tl) .trrteri,'r t'icw. Abl,reuiottoils: 0P =.til teriut process, cc = cnemiol crest, lg = lateral grooue, pp = posterior process.
Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
293
rior margin of the tibia in Apatosaurars forms a long shallow bow due to the large cnemial crest (Fig. 13.23A). ln Cdmarasaurus, the anterior margin of the tibial shaft is straighter below the small cnemial crest (Fig. 13.23G). Diplodocus and Baroscturus tlbiae can be distinguished from Camardsaurus and Apatosaurus by the gracile nature of the tibial shaft (Fig. 13.23D). Whereas Camarasdurus and Apatosaurus tibiae have very similar robustness, their distal ends are expanded mediolaterally and craniocaudallS respectively (Fig. 13.23B, H). Fibula. The fibula in sauropods is a long, slender element and is always longer than the corresponding tibia (Fig. 13.2a). The proximal end of the fibula is expanded craniocaudally, with the most prominent feature being a large, triangular, tibial ligament scar on the medial side extending from the proximoposterior border diagonally to the anterior border of the fibula, between one-fifth and one-third of the way dou.n the shaft (Fig. 13.24C, R I). In lateral or medial view, the posterior edge of the fibular head is relatively straight, but the anterior edge expands noticeably. Below the wellwidened head, the shaft of the fibula narro\vs until the slightly expanded distal end.
The most noticeable feature of the fibular shaft is the prominent muscle scar for the insertion of M. iliofibularis located just short of halfway down the lateral side (Wilhite 2003b; for alternate interpretation see Bonnan 2001) (Fig. 13.24A, B, D, E, G, H). Below this scar, the anterior edge of the fibula is very narrow compared to the posterior edge. The distal end of the fibula is expanded siightly anteroposteriorly with a large medial expansion forming an astragalar process (FiS. 13.248, E, H) that fits into the fibular fossa on the astragaius. The distinguishing characters of the fibula include the shape of the proximal end, the nature of the transverse ligament scar, and overall robustness. As with the tibia, the robustness of the fibula in Cama-
rlsdurus and Apatosaurus is very similar. ln Camarasaurus the proximal end of the fibula is anteriorly divergent from the main shaft of the fibula (Fig. 13.24G-I). In diplodocids there is no noticeable diver-
of the proximal end of the fibula from the shaft (Fig. !3.244-F). One exception to this character ts Camarasaurus grandis (YPM 1901 and YPM 1905 from Como Bluff,'Wyoming), in which the prorimal end of the fibula does not diverge from the shaft. Another feature that may help distinguish Camarasaurus and Apatosaurus is the nature of the transverse ligament scar on the medial side of the fibula. In Camarasaurus, the anterodistal portion of the ligament scar forms a medial prominence (Fig. 13.24H, I), whereas in Apdtosaurus, there is no prominence (Fig. 13.248, C). In addition, the transverse ligament scar of Camarasaurus extends farther down gence
the medial shaft of the fibula (about one-third of the way; Fig. 73.241) than it does in Apatosaurus (about one-fifth of the way; Fig. 13.24C). Diplodocus fibulae are most easily identified by the extremely gracile
fibula shaft (Fig. 1.3.24D-F). Otherwise the features of Diolodocus fibula are verv similar to those seen in A,atosaurus.
.
D. Ray Wilhite
the
tlt) - '( ,.-'"{
Late ral I
__l
c tls
-
Later al I
I
I
Fig. 13.21. Digitized sauropod right fibulae (not to scale). Apatosaurus (BYU 681-12801) in (A) Iateral uieu, (B) posterior
mp_
:I t:l
uieu\ and (C) medial uieu,; Diplodocus IMV/C No #) in (D) lateral uiew, (E) posterior uiew, and 1F) medial uiew; and Camardsaurus (KUVP 573) in (G) lateral uiew, tHt postcriur uicu'. and (I) medial uiew. Abbreuiations: ap -- astragalar process,
if
=
M. iliofibularis
insertion scdr, mp = medial prominence.
Discussion The utility of any element as a taxonomic indicator is at least partially related to its preservation potential. Flat bones such as the scapula, coracoid, ilium, and sternals are frequently distorted during the diagenesis of the rocks in which they are found. Also, they are very thin in places and these areas are frequently preserved poorlv. Appendicular elements with excellent preservational potential include the humerus, radius, femur, and tibia. These bones are all relatively short and robust compared to the other appendicular Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
.
295
elements, rvith few thin processes. The remaining appendicular elements (ulna, pubis, ischium, and fibula) are frequently well preserved, but each has peculiarities that limit its preservation potential. The sauropod ulna has medial and lateral processes that are relativeiy thin and at approximate right angles to one another. These processes are easily deformed by sediment compaction. The pubis is a massive element, but the posterior border is thin and many times is not preserved. The ischium is a long, thin (relative to its width) bone rn'ith a thin anterior edge susceptible to diagenetic effects, such as warping, and poor preservation. The fibula is very long and thin relative to the other appendicular elements, and it is very common to see fibulae with the shaft bent in several places due to diagenetic alteration of the bone after burial. Knowing these po-
tential preservational problems and the taxonomically significant morphological features of each bone, it is possible to consider the usefulness of each element as a generic identifier. Sternals are of litle taxonomic significance below the level of family. The probable cartilaginous nature of the majority of the sauropod sternum (based on the rugose borders) suggests that ossification of the sternal plates varied with age. Juvenile sauropod sternal plates differ in shape from those of adults and appear to have been almost totaily surrounded by cartilage, since they are rugose even on the lateral margin (Fig. 13.a). Also, individual variation within genera is not well documented. The utility of the coracoid for taxonomic identification is limited because considerable variation can be observed within genera. Also, many characteristics of the coracoid are based on relative differences between taxa and are difficult to assess in single specimens; however, the quadrilateral coracoid ol Apatosauras is unique, allowing most apatosaur coracoids to be identified with confidence even in the absence of other elements. Filla and Redman (1994), however, have shown that at least one Apatosaurus species, A. yahnabpin, from the lower third 'Sfyoming, had an oval coracoid with of the Morrison Formation of rounded margins, a discovery that calls into question the generic identification of isolated coracoids that do not exhibit the typical Ap ato s aur u s morpholo gy.
Scapulae are very useful for taxonomic identification. Even partial scapulae can, in many cases, be identified to genus; however, uncommon taxa such as Swpersaurus and Seismosaurus are verv likely to be identified as more common Morrison taxa, such as Diplodocus and Barosaurzs, which they closely resemble. Filla and Redman (1994) documented such a case by pointing out that the scapula of A. yahnahpin was originally identified as a cetiosaur based on its morphology, aithough subsequent material clearly demonstrated the scapula belonged to an apatosaur. Humeri are excellent elements for generic identifications; however, the identification of incomplete diplodocid specimens can be difficult because taxonomic affinities are based on robustness and no single portion of the humerus is diagnostic. In addition, A. yahnahpin has a gracile humerus like that of Camarasaurus (Ieast
296 . D. Ray\(ilhite
breadth:length = 0.16) so robustness alone will not help separate diplodocid and Camarasaurus humeri. Nonetheless, as more specimens are described and prepared, it may prove possible to separate some species based on robustness. For instance, Apatosaurus louisae from Dinosaur National Monument is much more robust than any other Apatosaurus species thus far known (Mclntosh 1990a). Based on morphological features and measurements, the radius is not useful for differentiating sauropods at even rhe family level, and identifications should be based on other, more diagnostic elements. However, within a given quarry it is sometimes possible to distinguish between genera based on robustness alone, as can be '!flilhite seen in radii from Dinosaur National Monument (see 2003b). The ulna is of some use as a taxonomic indicator. Overali robustness is the key to distinguishing between Apatosaurus and Diplodocus; however, there are definite morphological differences between Camarasaurus and diplodocids. Given well-preserved material, it is possible to assign at least family-level identifications to isolated elements. Given the presence of all the key features noted above, many can be identified at the generic level as well. The ilium is a moderate to poor taxonomic indicator in most cases due to the poor preservation of most specimens, which hinders identification of many specimens beyond the level of sauropod. \Well-preserved ilia, however, may be easily identified to family based on the suite of characters given above. The ischium is very useful as a taxonomic indicator because of the taxonomic significance of the ischium's shape. Even partially preserved ischia can almost always be identified to family. If the distal ends are present, Diplodocus and Apatosaurws ischia can be distinguished by the angle at which the ischia join; however, there are not enough specimens of most of the rarer sauropods (i.e., Sezpersaurus) to truly assess morphological variation of the ischia in those taxa. The pubis is a relatively poor element for raxonomic identification. Unless the proximal end is well preserved, it is virtually impossible to assign even a family identification to many pubes.'Wellpreserved elements, however, can often be identified to genus. The femur is a very reliable taxonomic indicator; however, Camardsaurus and Apatosaurus femurs are easily confused and, when possible, these taxa should be identified based on a suite of femoral characters. Because identification of many femora relies on the morphology of the prorimal and distal ends, it is important to make sure that these surfaces are relativel)' complete and uneroded if identification is to be attempted. The tibia is a fairly diagnostic element for taxonomic differentiation; however, based on the tibiae examined in this study, it is still unclear how to separate Diplodocus and Barosaurus tlbiae. Also, if the cnemial crest is broken or poorly preserved, the differences between Apatosaurus and Camarasaurus trbiae can be very
Variation in the Appendicular Skeleton of North An-rerican Sauropod Dinosaurs
.
297
difficult to discern because tibial robustness overlaps ('Wilhite 2003b). As with most other limb elements, identifications should be based on more than one feature of that element. Fibulae can be used as taxonomic indicators but should not be relied on for a positive generic identification. As mentioned above for other elements, it will always be difficult to tell Diplodocus from Barosaurus. I have observed that fibulae are easily distorted during diagenesis and it is often difficult to distinguish the subtle features that differentiate genera; however, given well-preserved material, fibulae can frequently be identified to genus with confidence based on overall robustness (Apatosaurus vs. Diplodocus) or morphological features (Camarasaurus vs. diplodocids). Conclusions The two key factors that influence the usefulness of a given appendicular element as a taxonomic indicator are preservation potential
and the presence of taxonomically significant morphological features. Based on observations of over five hundred individual appen-
dicular elements, the best appendicular elements for taxonomic identification of North American Jurassic sauropods at the generic level appear to be the scapulocoracoid, humerus, femur, and ischium. Given good preservation, however, any appendicular element may be identifiable at the genus level. The most important aspect of sauropod research involving appendicular material is to observe and measure enough material to determine the range of 'While variation. it may be said that variation within the appendicular skeleton of Diplodocus, ApatosaLtrus, and Camarasaurws is well understood, numerous taxa known only from a single specimen or small numbers of specimens remain enigmatic. The detailed morphological descriptions given above are intended to be a first step in understanding the range of qualitative morphological variations in the appendicular skeletons of sauropods. Acknowledgments. I would like to thank the Jurassic Foundation, the Louisiana State University chapter of Sigma Xi, and the Louisiana State University Museum of Natural Science for their support of this project. I am also grateful to Art Andersen of Virtual Surfaces for the use of the Microscribe digitizer as well as for editing of data for the project. This research represents a portion of my dissertation work and I am most grateful to my advisor, Judith Schiebout, for keeping me focused on the task at hand. I would also like to thank the rest of my dissertation committee: John 'Wrenn, Laurie Anderson, Barbara Dutroq Paul Farnsworth, and Dan Hillmann for their support. I am also grateful to Ken Carpenter, Virginia Tidwell, and Matt Bonnan for their insightful and constructive reviews of this manuscript, which have greatly improved its content. Thanks also go to the collection managers and curators of the many institutions r,vhere I have worked over the years, including:
Dan Chure, Dinosaur National Monument; Ken 298
.
D. Ray Wilhite
Stadtman,
Brigham Young University Earth Science Museum; Don Burge, College of Eastern Utah; Burkhard Pohl,'lfyoming Dinosaur Center; David Brown, Tate Geological Museum; John Foster and Rod Sheetz, Museum of 'Western Colorado; Larry Martin and Dave Burnam, University of Kansas; Ken Carpenter and Virginia Tidwell, Denver Museum of Natural History; Pete Reeser, New Mexico Museum of Natural History; Jack Horner and David Vericchio, Montana State University; Peter Dodson, Matt Lamana, and Josh Smith, Philadelphia Academy of Natural Science; David Berman and Betty Hill, Carnegie Museum; Mike Brett-Surman, National Museum of Natural History; Mark Norell, American Museum of Natural History; Vicki Yarborough, Yale Peabody Museum; Bill Simpson, Field Museum of Natural Historn Chicago; and Matt Wedel, Sam Noble Oklahoma Museum of Natural History.
Finally,
I would like to thank my mentor and friend, Jack
Mclntosh, for nurturing my initial interest in sauropods and for al-
ways being willing
to
discuss perplexing aspects
of
sauropod
anatomy. References Cited
Bakker, R. T. 1987. The return of the dancing dinosaurs. In S. J. Czerkas and E. C. Olson, eds., Dinosaurs Past and Present. Vol. 1, 39-69. Los Angeles: Natural History Museum of Los Angeles County in association with University of 'Sfashington Press. Bonnan, M. 2001. The evolution and functional morphology of sauropod dinosaur locomotion. Ph.D. dissertation, Northern Illinois University. 2003. The evolution of manus shape in sauropod dinosaurs: Implications for functional morphology, forelimb orientation, and phylogeny. Journal of Vertebrate Paleontology 23(3): 595-613. Carpenter, K., and J. S. Mclntosh. 1994. Upper Jurassic sauropod babies
from the Morrison Formation. In K. Carpenter, K. F. Hirsch, and J. R. Horneq eds., Dinosaur Eggs and Babies, 265-278. New York: Cam-
bridge University Press. Cope, E.D. 1877. On a gigantic saurian from the Dakota epoch of Colorado. Paleontology Bulletin 25 5-10. Curtice, B. D., and R. Wilhite. 1996. A re-evaluarion of the Dry Mesa Quarry sauropod fauna with a description of new juvenile sauropod elements. In Geology and Resources of the Paradox Basin: IJtah GeoIogical Association, 1996 Field Symposium,325-338. Utah Geological Association Guidebook, no. 25. Salt Lake City: Utah Geological Association. Filla, J., and P. D. Redman. I994. Apatosaurus yahnahpfu: Preliminary description of a new species of diplodocid sauropod from the Late Jurassic Morrison Formation of southern Wyoming, the first sauropod dinosaur found with a complete set of "belly ribs." In The Dinosaurs of 'W1,oming, 159-178. Wyoming Geological Association 44th Annual Field Conference GuidebooA. Casper: Wyoming Geological Associa-
tlon. Gillette, D. 1991. Seismosaurus halli (n. gen., n. sp.) a new sauropod dinosaur from the Morrison Formation (Upper Jurassic-Lower Cretaceous) of New Mexico, U.S.A. Jottrnal of Vertebrate Paleontology 1L: 417-433. Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
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A nearly complete articulated skeleton of CamarasdLtrus, a saurischian dinosaur from the Dinosaur National Monument. Memoirs of the Carnegie Museum 10:347-384. 1936. Osteology of Apatosdurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum I1:
Gilmore, C. \7. 1925.
75-300. M. 1987. Bringing dinosaurs to life. In S.J. Czerkas and E. C. Olson, eds., Dinosattrs Past and Present. Yol. 1,97-71.3. Los Angeles: Natural History Museum of Los Angeles County in association with 'Washington Press. University of Hatcher, J. B. 1902. Structure of the forelin.rb and manus o{ Brontosaurus. Annals of the Carnegie Museum 1.: 356-376. 1903a. A new sauropod dinosaur from the Jurassic of Colorado. Proceedings of the Biological Society (\Tashington) 1'6: 1'-2. 1903b. Osteology ol Haplc,tcanthosanrus, with description of a new species, and remarks on the probable habits of the Sauropoda and the age and origin of the Atlantosaurus beds. Memoirs of the Carnegie Museum 2: 7-7. 'Wirbeltierfauna der TendaguruJanensch, W. 1914. Ubersicht irber die 1
Hallett,
Schichten, nebst einel Kurzen Charakterisierung der neu aufgefirhrten
Arten von Sauropoden. Archiu fiir Biontologle 3: 81-1 10. Marsh, O. C. 1,877. Notice of some new dinosaurian reptiles from the Jurassic Formation. American lournal of Science, ser. 3, 14: 514-576. 1878. Principal characters of American Jurassic dinosaurs. Part I American Journal of Science, ser. 3, 16: 41'1'41'6. 1881. The sternum in dinosaurian reptiles. American lournal of Science, ser. 3, 19: 395-396. 1890. Description of new dinosaurian reptiles. American Journal of Science, ser. 3, 39: 81-86. Mclntosh, J. S. 1990a. Species determination in sauropod dinosaurs with tentative suggestions for their classification. In K. Carpenter, and P. J. Currie, eds., Dinosaur Systematics: Approaches and Perspectiues, 53-69. New York: Cambridge University Press. 'Weishampel, P. Dodson, and H. Os1990b. Sauropoda. In D. B. m6lska, eds., The Dinosauria, 345-401. Berkeley: University of California Press. Osborn. H. F.. and C. C. Mook. 1919. Reconstruction of the skeleton of tlre sauropod dinosaur Camarasaurus Cope (Morosaurus Marsh). Proceedings of the National Academy of Sciences 6: 15. 1,921,. Camarasaurus, Amphicoelias, and other sauropods of Cope. Memoirs of the American Museum of Natural History 3: 246-387. Parrish, M., and K. Stevens. 2002. Rib angulation, scapular position, and body profiles in sauropod dinosaurs. Journal of Vertebrate Pdleontology 22(3A): 95A. Riggs, E. S. 1903a. Brachiosaurus abithordx, the largest known dinosaur. American lournal of Science, ser. 4, 15: 299-306. 1903b. Structure and Relationshil2s of Opisthocoelian Dinosaurs. Part I: Apatos avus Marsb. Field Columbian Museum Geology Series, no.2. Chicago: n.p. Upchurch, P. I995. The evolutionary history of sauropod dinosaurs. Pi:i/o-
sophical Transactions 36s-390.
300
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D. Ray $Tilhite
of the Royal
Society
of London B,
349:
Wilhite, R. 1999. Ontogenetic variation in the appendicular skeleton of the genus Camarasaurus. Master's thesis, Brigham Young University.
2003a. Digitizing iarge fossil skeletal elements for threedimensional applications. Palaeontologia Electronica 5(2\. http:ll
palaeo-electro nica.or gl 20 02-2lscan/issue2-02.htm.
in
2003b. Biomechanical reconstruction of the appendicular skeleton
three North American Jurassic sauropods. Ph.D. dissertation,
Louisiana State Universitl.. http://etd02.1nx390.lsu.edu/docs/available/ etd-0408 103-003549/. 'Wilson, J. A., and P. C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Journal of Vertebrate Paleontology, memoir 5, 18(2, supp.): 1-68.
Variation in the Appendicular Skeleton of North American Sauropod Dinosaurs
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1-4.
First Articulated Manus of Diplodocus carnegii Mercornr W. Bpoprr Jn. eNo Devro L. Tnpxrpn
Abstract Though Diplodocws carnegii is one of the more familiar Jurassic sauropods, the manus of this animal is known only from isolated elements. In existing mounts, the manus has been created by substi-
tution from the remains of other taxa. In 1997, the articulated manus of a single, subadult Diplodocus cf. carnegii (V'DC-FSO01A) was recovered from a Morrison Formation location (FS Quarry) in northern '$7yoming. This includes five
metacarpals, one phalanx, and an ungual; all are short and of gracile proportions. Also present were two articulated pes, and many bones of the appendicular and axial skeleton. After careful comparison with corollaries from Sauropoda known to be extant within that time
frame and area, alI \7DC-FS001A elements are interpreted as Diplodocidae. Diplodocus hayi, the only previously recognized member of this group with a reasonably intact and articulated distal forelimb, is too robust to account for the N7DC-FSOO1A manus. Since nothing in the observed anatomical features of 'ff/DC-FS001A is in unquestioned agreement with a corresponding D. longus hoiotype (YPM 1920) model, but does agree with the known D. carnegii mate302
rial, the manus is referred to D. carnegif providing the first objective information on the structure and arrangement of this assemblage for
D. carnegii.
Introduction From the first discovery (D. longus), by Benjamin Mudge and 'Wendell Williston in 1877, the various species of Samuel 'With the Diplodocidae have enjoyed a large amount of publicity. rush to describe new taxa of dinosaurs, the "bone wars" of the late nineteenth century (particularly the competition between Cope and Marsh) resulted in some errors of description. Some of the initial information regarding the type specimen Diplodocws longws has proved to be incorrect (Mclntosh and Carpenter 7998). For example, the manus found in loose association with other bones of the type Diplodoczs (Marsh 1896) was dismissed as not definitively part of the D. longus specimen (Mclntosh and Carpenter 1998). Since that time, other species of Diplodocus have been recovered. Diplodocus carnegii is known from several reasonably complete 'Western Interior of the United States but, until skeletons from the recently, none were found with an articulated manus (Mclntosh 1990a\. Diplodocus lacustris, diagnosed from only a few skeletal elements, also was found to be missing the manus (Marsh 1884; Mclntosh 1990a). Holland (1,924) described Diplodocus hayi, the only specimen shown conclusively to be in the family Diplodocidae and also to have a fairly complete, articulated manus. The manus of Apatosaurus has been recovered, but that animal is more distantly related (Marsh 1883; Mclntosh 1990a). With sauropods in general, metapodial elements are often lacking upon recovery.
Good manus preservation exists for other North American sauropods of the Western Interior. Several camarasaurids, including
BYIJ 9047, GMNH-PV 101, and holotype YPM 1910, have produced complete, or almost complete, maniis. Several brachiosaurid skeletons (Janensch 1961; Tidwell 2001) have also been recovered with relatively intact, articulated manus. No manus is currently known for Haplocantbasaurus (Hatcher 1903a; Mclntosh and Carpenter 1998) or Barosaurus (Lull1919 although see Mclntosh this volume). In the course of this study, various taxa of Sauropoda, including those from other continents, were examined and compared. This was done by means of actual bones, where practicable, and
with published descriptions supplemented, in some instances, with good color photographs taken from many angles. These include: Camarasaurzs AMNH 711; YPM 1901,4633, L9L0;BYU 9047; GMNH-PV 101; a Camarasaurus lentws from WDC described in this volume; Barosaurus YPM 429, 479; Haplocanthasawrus CM 572,879; Apatosaurus YPM 1980; Tate 001; CM 563,3018; brachiosaurid DMNH 39045 Brachiosaurus brancai (from Janensch 1,961); Tornieria robusta (from Janensch 1961): titanosauriformes DMNH 40932; Diplodocws HMNS 175; CM 84, 94, 307, 662; NMMNH 3690; USNM 10865; YPM 1920; and DMNH 1494. First Articulated Manus of Diplodocus carnegii
.
303
Fig. 14.1. Reconstructed natural position of manus (\X{DCFS001A) in proximal uiew, with carpal in place, and anteriur uieu. tuithout carpal.
The metacarpals of specimen \fDC-FS001A (Fig. 14.1), recovered from the FS Quarry, are not as elongate as those of camasaurids or brachiosaurids studied. Diplodocws hayi metacarpals 'WDC-FS001A, appear much more robust than those of having relatively expanded prorimal ends, and width:height ratios more like those of apatosaurids. Apatosaurs, in turn, have width: height:breadth ratios of their corresponding bones indicating a robustness greater than that in all other sauropods considered here for which good manus exist. Measurements of the \X/DC-FS001A manus elements may be found in Tables 1,4.1, 74.2, and 14.3. Along with the manus, several articulated mid-caudal vertebrae (FS 20,746,1.47,748,150A, 150B), and other associated cau-
dal vertebrae have been recovered from the FS Quarry. \7hen viewed laterally, the articulated caudals show a general elongate appearance, with deep latero-medial excavation, and a relatively flat area along the ventral surface punctuated by a significant cranial-caudal groove (Fig. 14.2). There is also strong lateral constriction. One caudal in this series, FS 181, shows a complete neural spine, with pre- and postzygopopheses intact (the other caudals also have fairly complete neural spines, but with some damage). 304
.
Malcolm \7. Bedell
Tr.
and David L. Trexler
TABLE 14.1. Dimensions (in mm) of the Right Manus of Diplodocus carnegii
(wDC-FS001A)
il
III
146
208
198
191
153
63
71
72
731.r
83
Metacarpal Greatest
Proximal
length breadth
852'
Prorimai depth
33
47
25
2r
21
Distal breadth
65
76
65
551r
71
602)
30 Least circumference 130
Distal
depth
37
26
24
.)L
139
104
112
125
I rX/ithout fragment.
2lWith fragrnenr in approrimare po'itiorr.
TABLE 14.2. Dimensions (in mm) of the Carpal oI Diplodocus carnegii (WDC-FS001A)
Transverse breadth
96
Anteroposterior diarneter
64
Thickness
.t1
TABLE 14.3. Dimensions (in mm) of the Phalanges ol Diplodocus carnegii (wDC-FS001A)
Greatest length Proximal breadth
Distal breadth
Phalanr I-2 tungualt 105 (distal end missing) 66
Phalanx [-
| {proximalt 69 34
I7
This caudal neural spine clearly angles toward the posterior of the tail, and slightly beyond the posterior rim of the centrum. No caudal vertebra has erect neural spines. Taken together, these characters are diagnostic for Diplodocus carnegii (Giimore 1932 Holland 1906; Hatcher 1.901,7903b). Also, none of the vertebrae in this series display the extreme, anteroposterior reduction of the centrum seen in haplocanthasaurs (Hatcher 1903a, 1903b). First Articulated Manus of Diqlodocus carnegii
.
305
Fig. 14.2. Articulated mid-caudal uertebrae t\v/ DC-1500 I A1 in sittt. offering a left lateral uiew, caudals to right being more distal. Note ektngation of centra and neural spines (where exposed on the three most distal caudals) leaning distally.
Three double-beamed chevrons were locared near the caudals.
One of these (FS 168), completely prepared, shows a gracility of appearance not seen in similar chevrons of the apatosaurs. A partially prepared cervical vertebra (FS 56) has a measured ratio of three to one (510 rnm to 170 mm) of the length of the centrum to its diameter. This would indicate a ratio not compatible with those of the centra of barosaurs (Lull 1,91,9). FS 56 also appears to resemble very closely cervical #9 or #10 in Hatcher's 1901 Diplodocus morphology (both attributed to Diplodocus carnegii). A complete scapulocoracoid is articulated, but unfused (FS 182, 186). The scapula has an expanded proximal plate, with a ridge separating the inferior and superior fossae, forming an acute angle with the shaft. This was seen as a Diplodocus character by Osborn and Mook (1921), and Mclntosh (1990a). Lack of fusion is viewed as an indication of subaduir status (Tidwell, pers. comm.). It is of a correct size to belong ro this animal (Vz to 2/z that of observed adults), and is very closely associated with a humerus (FS 151), as as the articulated caudals. As with FS 56, the outline and interior features of this bone are indistinguishable (with the exception of its being unfused to rhe coracoid) from the Hatcher description (1901) attributed to Diplodocus carnegii. A left humerus, FS 151, still in siru, directly covers a section of the articulated caudals. \fell exposed, its dimensions match perfectly the fully prepared right humerus (FS 221), and both are r/z to 2/s the size of adult diplodocids. There is a strong angulation of the bisecting planes (nearly 45') passing through the greatest diameter of each end. This torque, in turn, throws the deltoid crest far under the main axis of the bone. Gilmore (1932) thought this angulation to be a diplodocid character; easily distinguished from the much
well
306
.
Malcolm'i7. Bedell Ir. and David L. Trexler
i
,;"i
:
::.t
r*,'f.ii
*"
't*
Fig. 14.3. Complete right pes WD C-F 5001 A), witb arti culated astrdgalus in upper right, partially exposed in situ, frorn only known photogrdph (35mm), circa 19c)7. (
straighter appearance of apatosaurids (holotype YPM 1980), or camarasaurids (Mclntosh et aI. 1996b). A radius (FS 185) and an ulna (FS 194) were found in perfect articulation with each other, and with FS 151. They are very slender, and short, as with other diplodocids. Two compiete pes were also recovered from the FS site. One pes was found articulated with an astragulus, and was less than a meter from the manus (Fig. 1a.3). There was no calcaneum. The
astragulus
is much more gracile than those of examined
ap-
atosaurids and camarasaurids, with a very short medial projection. 'Whereas this is diagnostic to the genus Diplodocus, the diagnostic utility of these features to species level is not assumed (Wilhite, pers. comm.). Overall, the metatarsals are very gracile and thin, with a small latero-distal process on the plantar edge of metatarsal I partially damaged by pathology (Rothchild, pers. comm.) on one pes, but more evident on the second. Some workers consider this to First Articulated Manus ol Diplodocus carnegii
.
307
be a diagnostic dipiodocid feature (Averionov et al. 2002; McIntosh et al.7992:164).The longest metatarsals are III and IV, with
a
phalangeal formula of 2-3-3-2-1, all listed characters of Dipiodocidae (Mclntosh 1990a). Institutional abbreuidtions. AMNH-American Museum of
Natural History, New York, New York; BYU-Brigham Young University, Provo, Utah; CM-Carnegie Museum of Natural History, Pittsburgh, Pennsylvania; DMNH-Denver Museum of Nature and Science, Denver, Colorado; GMNH-Gunma Museum of Natural HistorS Tomioka, Gunma, Japan; HMNS-Housron Mrrseum of Natural Science, Houston, Texas; NMMNH-New Mexico Museum of Natural History, Albuquerque, New Mexicc.,; Tate-Tate Geological Museum, Casper, Wyoming; USNM-National Museum of Natural History, Smithsonian, 'Washington, D.C.; WDC-Big Horn Basin Foundation/Wyoming Dinosaur Center, Thermopolis, Wyoming; and YPM-Yale Peabody Mrrseum. New Haven. Connecticut.
Geology and History The specimen was discovered at the FS Quarry, located approximately 3 miles southeast of the town of Thermopolis, Wyoming, on the \farm Springs Ranch. The quarry is on the Thermopolis Anticline, and within the Morrison Formation (Fig. 1a.a). In this localit1', the Morrison Formation is bounded above by the unconformity of the cliff-forming Pryor Conglomerate Member (Ostrom 1970) of the Cloverly Formation (Lower Cretaceous), and overlies the marine Sundance Formation (Upper Jurassic). No formal subdivision has been applied to the Morrison of the Big Horn Basin in this area, r,vhich here is 63 meters thick (Carson 1999). This is informally divided into three generalized units: a lorver calcareous mudstone unit; a middle, fine-grained, quartzose sandstone unit; and an upper calcareous mudstone, or "carbonate mud" (Jennings 2002) unit, with sandstones interbedded (Bjoraker and Naus 1996). Subsequent studies by Cleaves and Carson (Carson 1999), Houck (pers. comm.), and Turner (pers. comm.) suggest that the paleoenvironment at the time of deposition was likely dry and monsoonal. Paleotopography would have been characterized by anastomosing streams and scattered small lakes, whose levels change when crevasse splays allow recharging of stream water during the monsoon (Jennings 2002). The bone-bearing stratum of the FS Quarry is a calcareous, nodular mudstone (Carson 1999),hmestone (Houck, pers. comm.), or "carbonate mud" (Jennings 2002). Houck (pers. comm.) interprets this environment as "probable la-
custrine." Other workers offer "para-lacustrine origin" (Jennings 2002), referring to a possible epherneral nature for the water body. Recent petrographic work utilizing X-ray diffraction, thin-probe chemicai analysis, and SEM on thin sections (Jennings in press) has confirmed a lacustrine interpretation. Ostracodes are clearly visible in the thin sections.
.108. Malcolm \7. Bedell
Tr.
and David L. Trexler
Geologic Section Warm Springs Ranch (neaf FS Quarry) Carson.
1
999
Geologic Sectlon Detail including FS Quarry (rt.) Houck, K., 2001 (unpublished)
tlu
fl Conglomerale [-- sandstone fl CalcareousSandstone El
F_!
section
Yot]*|.. scare (n)
f
50
I
L0
SilIStOne
Mudstone
e Bones r." Concretions
Gray siltstone, 1/4" beds: blocky fracture Gray fine sandstone, weathers tan, in 4" beds. Some layers splintery; some more nodular and €lcareous Gray siltstone,
FS Quarry
Section Detail
Dark gray mudstone, hard, massive, non-calcareous
Houck, K., 2001 (unpublished)
Bone-bearing beds at
FS
bl6ky in beds, 1/4" thick
Gray flne sandstone, weathers tani slightly cal€reous, massive
Dark gray, llne sandstone, nonralcareous
lI
L
Sandy limestone, nodular, fubbly, with mottles and small nodules, as below Gray, tine cal€reous sandstone to sandy limestone, quartzose with small nodules 1/4" to 1/8", & white mottles
Fig. 11.4. (A) V/arm Springs Ranch geologic section, from a location near FS Quarry. (B) Ce,tlogic Sertion Detatl. shnwing
position. (C) Quarrl, Detail, taith bonebearing beds from tuhich elements
FS site stratigraphic FS
of WDC-FS001A were recouered, including the right manus.
Although several researchers have studied the geology of this area, until recently none had noted the dinosaur bones here (Bjoraker and Naus 1996; Ostrom 1970). Darton (1906) mentions dinosaur bones in the region, but not in the Thermopolis area. Oil and gas geologists (Horn 7963) had also failed to notice the bones. In 1993, Dr. Burkhard Pohl became aware of the potential for dinosaur remains on the'Warm Springs Ranch. \7hile investigating this potential, several important discoveries were made. To date, over fifty fossil-bearing locaiities have been identified on the ranch. Research on these sites has been conducted with the supervision of the Big Horn Basin Foundation/$Tyoming Dinosaur Center since 1995. The FS Quarry was discovered by Ty Naus in 1993. 'Work was not attempted vntrl 1.997 due to the dangerous 30o slopes lit'WDC tered with large boulders. Since that year, staff and volunteers from the'Western Interior Paleontological Society (WIPS), and other organizations, have begun excavations and research at this site. Nearly a hundred bones were recovered during the 1997 seaFirst Articulated Manus of Diplodocus carnegii
.
309
Fig. 11.5. Quarry Map of the Loot Site showing distribution of bones witb manus assemhlage ntdgnified by a factor of 3 in blown-up
image (in box). Otber assemblages, as tuell ds indiuidual elements refeted to in text .lre labeled. Grid in .S tn squares.
son (Fig. 14.5), including articulated podal elements of two pes and
one manus. Logistics prevented further work at the quarry until 1999. Since then, work has continued, with the exception of the year 2000 field season (May-October) only.
Specimen Description The right manus (Fig. 1a.6) was discovered as an articulated group of five metacarpals (FS 45, 46,47,85,44), one phalanx (FS 42), and one carpal (FS 43). Closely associated, but not in direct articuIation, was an element tentatively identified as the digit one ungual phalanx (FS 220). Other phalanges are absent. The manus is be-
lieved mesaxonic, with metacarpal III being the longest, and III, and IV. Metacarpal II (Fig. 14.7), however, is in fact longer than metacarpal III (Table 14.1), but it is thought missing material at the distal end of metacarpal III would make it slightly longer than metacarpal II. The manus was originaily articulated but somewhat collapsed from a digitigrade living posture, though the metacarpals were still touching at both proximal and distal ends. Metacarpal V is slightly shifted from its natural position. A reconstruction of the manus with some of these distortions removed is shown in Figure 14.1. Its pose is presumed to be digitigrade because all previous analogues (Upchurch 1995, 1998) of articulated sauropod manus have been recovered in positions suggesting a semicircular, columnar arrangement of the metacarpals. As well, a recent functional morphological study of sauropod manus (Bonnan 2003) supports this. U-shaped manus trackways have also been found (Farlow et al. 1989; Lockley metacarpals V and I shorter than II,
1997\.
Metacarpal I (FS 45) is not as elongate as that of any camarasaurid metacarpals (Mclntosh, et al. 1996a; Mclntosh et al.
310 . Malcolm \7. Bedell Ir. and David L. Trexler
Fig. 14.6. WDC-FS001A manus, in situ (from phcttograpbs, uith cdsts of dctudl bones) demonstrating articulation of fiue metacarpals, anterior uiew (left to
right, V-l1, single phalanx (l-1, below and dttdched to metctcdrpal l), single carpal (aboue, and resting on metacarpals ll and I), and the closely associated, but dis ar ti cula t e d un gual p h a lanx placed near the lower right of phaldnx I-1.
.m
qffi
#w
Hffi E* X
W w
K
=*
.ffi:*i w
xsw
tr
W W
ffi
$
& 'r
Fig. 11.7. Metacarpals (\X/DCFS00 I At photographed
'ffi,'
digitally
in (A) anterior, (B) posterior, and Y lll ail r.. -ur...-*-.-l
(C) laterdl uieus; in order I-V, left to right, u'ith the only rrrorrrr, phaldnx left attached to metdcarpal l. Scale in cm.
First Articulated Manus of Diplodocus carnegii
. 3I1
Ant.
Post,
"":
&
Ycnt.
'-"w l\{etl.
'-"w Fig. 14.8. tA) Carpal (WDLFS001A) in (top to bottom) anterior, posterior, medial, and proximal uiews. (B) Manual ungual (WDC-FS})LA) in (top to bottom) dorsal, uentral, medial, and proximal uiews. (C) Metacarpals (WD C-F5001 A) I-V (top to bottom) in proximal uiews. Scale in cm. Dotted lines represent missing material.
'-'ffi l{} cm
r--I::I::r'--r1996b; Ostrom and Mclntosh 1999). Brachiosaurids (Janensch 1961; Tidwell et al. 2001) are distinctly more elongate, whereas apatosaurs were much more robust (Marsh 1883; Hatcher 1902; Ostrom and Mclntosh 7999;Fllla and Redman 1994). Diplodocus bayi (Holland, 1924) is also considerably more robust than this specimen.
The proximal end of FS 45 (Fig. 1a.8) is rugose, and slightly crescent-shaped, with a convex anterior edge, a concave interior edge, and anteroposterior elongation. Some bone is apparently miss-
ing from the posterior proximal end of metacarpal I, although not 312
.
Malcolm !7. Bedell Ir. and David L. Trexler
enough to alter this interpretation of its shape (see Fig. 14.7).Upon examination by Rothchild (pers. comm.), this was not thought to be the result of pathology. The bone may have been lost before permineralization was accomplished. There appears to be more of a "twist" between the proximal and distal ends of metacarpal I than is ordi-
narily noticed in camarasaurids (Ostrom and Mclntosh 1999). An angle of 38" is described by the intersection of the long axis of the proximal end of metacarpal I and a mediolaterai line parallel to the distal end of the bone, in proximal view. The lateral surface of the shaft of metacarpal I is fairly straight, with a slight bulge in the middle, whereas the medial surface is slightly concave. The medial surface of the shaft exhibits a central concavity, roughly one-third of the
distance from the proximal end. On the anterior surface of the distal end is a distinct articular surface for phalanx I-1, rising toward the medial side and culminating in an abrupt bulge. This articular surface angles downward and outward toward metacarpal II, forming a laterodistal process. The bulge at the apex of the anterodistal articular surface forms a ridge, rising through the middle of the anterior surface to the highest point on the crescent of the proximal end. Posteriorly, there is also a bulge at the middle of the laterodistal process, extending up the middle of this face of the bone, and terminating in a cavity formed partially by the bone missing near the proximal margin. This concavity most likely provided an attachment surface for a ligament located at the center of the metacarpal arcade. On the lower anterodistal articular surface of metacarpal I, both closely appressed to it and attached by matrix, is proximal phalanx I-1 (FS 42). This phalanx is badly distorted, and appears to have been somewhat crushed anteroposteriorly. There is an articular surface for the ungual on the anterior side of FS 42, but it is not well defined. Metacarpal II is the most robust of the group, and the longest. The shaft of this element is nearly as wide mediolaterally as it is deep anteroposteriorly throughout its length. It is believed to have been originally shorter than metacarpal III, but this cannor be veri-
fied yet. The rugose proximal surface is subtriangular in shape, with some missing one medial proximal margin. The surface of this element is damaged, and small pieces are missing from the medial side. If restored, the medial side would be an almost straight surface, with a slight middle bulge. There is a striated rugosity along the proximal upper-half of this surface reminiscent of the C. lentus holotype (YPM 1910). Laterally, metacarpal II has a smooth, nearly flat surface. One corner of the proximal surface lies lower than the others. This lower portion borders the anterodorsal border of the lateral metacarpal surface. There is also a subtle middle bulge on this lateral surface.
Most distal, anterior articular surfaces in sauropods examined are more pronounced than the posterior surfaces. The anterior articular surface here is correspondingly higher as well, but seems to form a very thin, laterodistal edge, which, in turn, extends downward and away from the center of the distal condyle. Vierved distally, metacarpal II exhibits a great deal of anteroposterior elongaFirst Articulated Manus of Diplodocus carnegii
.
3L3
tion. There are at least two marks, which appear on the lowerdistal anterior edge of metacarpal II. These marks extend across the distal surface to the medial edge, and rnay be toorh marks. In any case, they appear postdepositional. Middle lateromedial bulging of the anterior shaft surface of metacarpal II is exaggerared somewhat by bone missing at both the upper lateral and lower medial edges. The entire anterior surface, however, is concave between the proximal and distal ends. Posterior surfaces are smooth, rvith a small bulge about one-third of the distance from the proximal to the distal margins. Overall, this surface is straight, lvith a flaring at each end, viewed mediallv. toward the proximal and distal articulating surfaces. Metacarpal III, the second longest of the group, also suffers from missing bone fragments and eroded surfaces. A large quantity of bone is missing from along the upper anterior surface adjoining the anterior edge of this element. The proximal surface is rugose and subtriangular in contour. The shaft is elongare, though not nearly as much as in examined camarasaurid and brachiosaurid specimens (Mclntosh et al. 7996b; Janensch 1961; Ostrom and Mclntosh 1999; DMNH40932). Because of the missing bone, the anterior surface looks more rugose than it was origrnally. The anterodistal end exhibits a very high articular surface. This articular surface obviously provided a well-defined joint face for articulation with a phalanx. No such phalanx, however, was discovered in the quarry. The medial edge of the anterior surface is relatively straight, and the lateral edge markedly concave, whereas the lateral edge of the proximal end continues to a laterally protruding point. There is a proximal-distal groove extending across the middle of the anterior surface, from the apex of the anterodistal articular surface to the area of the missing bone. In lateral view, the edge of this groove thickens distoproximally to a point about
two-thirds of the distance from the distal end into a kind of
process. Due to missing portions of the distal and proximal ends of the shaft, an accurate determination of this feature is difficult. A
groove is also present on the posrerior shaft, bisecting a bulge rn the middle of the shaft (viewed medialiy), and with slight concavities between this bulge and both the prorimal and distal ends of the bone. Metacarpal IV has a smooth, slightly concave anrerior surface, and there is some evidence of crushing of the lower mediodistal
edge. The prorimal end is missing a significant portion of bone from its posterior side. Restoration of this area would likely show a lateromediaily elongated crescent, rvith the anterior edge describing
a concavity. As with
metacarpal
III, the proximal
surface
is
rounded on the medial side when viewed anteriorly, and becomes a laterally protruding point on its lateral edge. This area is slightly damaged. \fere the missing secrion present, this laterally protruding point would be even more pronounced. On the medial edge, a triangular piece of bone juts from the otherwise rounded surface. This fragment matches perfectly the area missing from the upper
314 . Malcolm
S7. Bedell Jr.
and David L. Trexler
lateral edge of metacarpal III. The fragment was left attached to metacarpal IV during preparation, since it provides a "key" to the original in situ articulation. The posterior surface of the shaft bulges out distinctly toward the middle, in either lateral or medial views. In these views, metacarpal IV is quite slender throughout its length. A jagged, 11-mm protuberance of bone on the anterodistal surface close to lateral edge may be a preparation relic. In general, the distal end has a narrow and subrectangular aspect (viewed distally), and the articular surface for the missing proximal phalanx is damaged.
Metacarpal
V
has an anteroposteriorly expanded proximal
surface, its greatest width exceeding that of the distal face by a ratio of 1.17 to 1.00. If a line is taken through the long axis of the proximal and distal ends, there is a "twist," forming an angle of 28". This feature becomes even more apparent in the upper medial edge of the proximal surface, where it bends toward the anterior f ace ol the bone. This anterior face is smooth and slightly concave when seen mediolaterally. There is some bone missing on the lower anteromedial face, and a very minor offset may be due to a preparation error. Posteriorly, the surface is smooth from the proximal to distal ends, with the exception of a transverse groove extending from the mediodistal to the lateroproximal corners of the bone. The proximal end is rugose, and it tapers smoothly on the posterior edge. It appears, in proximal view, as a rather thin wedge, somewhat wider laterally than medially. A distal view of metacarpal V reveals a much more robust, elliptical shape, with a smoother surface and a distinctly high articular surface on the anterior edge for the probable placement of the missing proximal phalanr. As with metacarpal II, there are grooves present that may be postdepositional in nature. The medial surface of metacarpal V is a thin edge
bending anteriorly at the proximal end. The lateral edge of metacarpal V is much thicker than the medial edge, smooth, and gradually curves toward the posterior surface.
A carpal found in articulation with the proximal ends of
metacarpals I and II (Figs. 14.2, 14.4) is rhomboidai and slightly rugose when proximally viewed, with pronounced medial tapering from a flat surface. Viewed distally, the same general shape is observed with an emarginate medial edge. This emargination is likely due to postmortem bone loss. This distal surface erhibits a more even surface than the proximal, with no obvious protuberances.
The anterior aspect is wedge-shaped, with the lateral edge wider (by approximately a 2:1 ratio) than the medial edge. There is some bone absent from this lateral edge. A thin medial surface gradually increases to the much thicker lateral surface. Proximal tapering is visible on the lateral edge. Also, the lateral edge shows grooves sim-
ilar to those described for metacarpals II and V. The only manual unguai recovered from the quarry thus far was discovered in close association rvith the other bones of the articulated manus. This ungual appears to be of the correct size and shape to belong to the manus. It is a right ungual phalanx (I-2). There is a First Articulated Manus o{ Diplodocus carnegii
.
315
sharp-edged anterior surface, lateromedial hook-shape, broader proximal surface, and, at the expanded proximal end, a rounded depression for ligament attachment to the proximal phalanx. There is bone absent from the anteroproximal and posteroproximal edges, and the entire medial surface is generally smooth. Tapering from proximal to distal edges is pronounced, and the tip of this claw core (roughly the bottom-fourth portion of the bone) is missing.
Discussion and Conclusions These bones represent the first report of articulated metacarpals from this species of dinosaur. Additionally, WDS-FS001A is identified as a subadult because the manus and all other associated skele-
tal elements recovered to date are of a size and morphology consistent with the interpretation of a single subadult animal present in the quarry. For example, the humeri and the articulated radius/ulna are only about one-half to two-thirds the size of the Diplodocus
DMNH 7494, identified
as an adult. The scapulocorato 2/s adult size, was found unfused, but articulated. This lack of fusion is an accepted character of immaturity in specimen
coid, also
Vz
sauropods.
Regarding the placement of the bones as to anrerior and poste-
rior surfaces, particularly in their natural articulation, several factors were considered. These include: (1) proximal end shapes and how they fit together because of ground distortion or missing bone and (2) shaft surfaces definitively shaped to suggest ligament attachment on a posterior surface. The obvious osteological keys were not always present. Some postmortem distortion may have occurred. Also, much bone is missing from several elements of the manus, enough to significantly distort some views (see Fig. 14.7). The placement of the articulated carpal, especially regarding the shape of the proximal end of metacarpal I, was considered important. How the ungual phalanx could properly articulate with the proximal phalanx was yet another consideration, though the ungual was only closely associated with the rest of the manus. In any instance, where the articulation was ambiguous, the in situ articulation was used
as the defining factor. Observations of unusual features include that the "twist" between the proximal and distal ends of metacarpal I is greater than is present in camarasaurids (Ostrom and Mclntosh 1999). The 28'
angle formed between the proximal and distal long axis of metacarpal V is also something unnoticed in other sauropod taxa. Marks present on metacarapals II and V, and the carpal, may be tooth marks and are likely not part of the original metacarpal structure. If so, this might explain the missing phalanges (Fiorillo 1997).It is thought that metacarpals II, III, IV and V each had a single phalanx, despite their lack of recovery in WDC-FS001, due to the presence of corresponding articular surfaces at the distal ends of each bone, as well as the prevalence of this arrangement in the Sauropoda.
316 . Malcolm W. Bedell
Tr.
and David L. Trexler
There are three accepted species of Diplodocus D. longus, D. carnegii, and D. hayi (Mclntosh 1990a). The holotype of Diplodocus longus is now thought to consist of eight caudal vertebrae with one chevron, with other bones assigned by Marsh described as questionable (Mclntosh and Carpenter 1998). Entire specimens tentatively labeled D. longus show enough differences with this holotype to possibly constitute a different species, or were tentatively attributed in the first place (Gilmore 1.932; Mclntosh and Carpenter 1998). At least one of these (DMNH 7494) is a composite skeleton. There are five skeletons and two skulls, as well as "hundreds of postcranial elements" recognized for D. carnegii (Mclntosh 1990a). As can be seen from the previous descriptions and introductory remarks, the FS specimen cannot be easily separated taxonomically from Diplodocws carnegii. Many of the \X/DCFS001 elements have no accepted D. longus counterparts, though they do closely resemble those available from D. carnegii specimens, and differ from the few available D. hayi bones. However, the taxonomic classification within the genus Diplodocus itself is problematic (Gilmore 1932; Mclntosh and Carpenter 1998; McIntosh 1990b). Unfortunately, the paucity of diagnostic material available for D. longus prevents an accurate assessment of interspecific versus intraspecific variation between the two taxa. Since the FS specimen cannot be taxonomically separated from D. carnegii, and a resolution of tbe D. carnegii-D. longus issue is beyond the scope of this paper, rve have identified the FS specimen as D. carnegii.
Acknowledgments. \7hen a project approaches its seventh yeat the difficulty in affording all deserving parties proper gratitude becomes overwhelming. From Mr. Ake Sawa of Japan, who, with his cheerful group of Japanese volunteers, courageously helped to reopen a dangerous quarry under the guidance of geologist Bill Stein, to the raft of Florida Atlantic University graduate students who labored in 105" heat for months without ever seeing a bone, dozens of people have made invaluable contributions to the
fieldwork. Here,
I would particularly like to thank the Greater
Denver Gem and Mineral Council and Joanne Passmore for financial support; the'Western Interior Paleontological Society Big Horn Basin Foundation, and the Schiele Museum of Gastonia, North Carolina, for volunteers and equipment; as well as Karen Houck, Christine Turner, and Debra Jennings for their geological acumen; and also Carla Smith, who first noticed the manus. Gratefully acknowledged for both their assistance and inspiration are Jack Mclntosh, Robert Bakker, Jim Kirkland, and Lou Taylor. Thanks to Ray \X/ilhite, Matt Bonnan, and Bruce Rothchild for their expert technical opinions; Judy Peterson for her accuracy and artistic talent; Rich Barclay for his computer-drawing skills; John Rising for excellent photography; and Ray Jones for his specially shielded scintillometer. Appreciation is due to the Denver Museum of Nature and Science for specimen access and, especially, Virginia Tidwell and KenFirst Articulated Manus of Diplodocus carnegii
.
31,7
neth Carpenter, who, along with an anonymous South American reviewer, provided extremely insightful critiques of this paper's early iterations. Houston's Museum of Natural Science was notably helpful, as was the Morrison Museum of Natural History. I would also like to thank Susan Passmore for continued advocacy of this effort over the years as well as technical expertise with the 69ures, and Burkhard Pohl, without r,vhose multitude of encouragements and support none of this could have happened. And finally, Shirley Bedell, who will never see the end result she helped nurrure. References Cited
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Basin, 297-426. \7,voming Geological Association Guidebook, no. 47. Casper: lfyoming Geological Association. Bonnan, M. F. 2003. The evolution of manus shape in sauropod dinosaurs: Implications for functional morphology, forelimb orientation, and phylogen.v. lourndl of Vertebrate Paleontology 23(3): 595-613. Carson, C. 1999. Stratigraphy at the Warm Springs Ranch. Master's thesis, Oklahoma Stare Universirv. Darton, N. H. 1906. Geology of the Bighorn Mountains. United States Geological Survey Professional Paper, no. 51. 'Washington, D.C.: GPO. Farlow, J.O., J.G. Pittman, and J. M. Hawthorne. 1989. Brontopodus birdi, Lower Cretaceous sauropod footprints from the U.S. Gulf Coastal Plain. In D. D. Gillette and M. G. Lockley, eds., Dinosaur Tracks and Traces, 372-394. New York: Cambridge University Press. P. D. Redman. L994. Apatosaurus yahnahpln: Preliminary description of a new species of diplodocid sauropod from the late Juras'$fyoming, sic Morrison Formation of southern the first sauropod dinosaur found with a complete set of "be1ly ribs." In Gerald E. Nelson, 'lfyoming Geological Ased., The Dinosaurs of Vlyoming, 159-178.
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9:379403. Horn, G. H. 1963. Geolog,v of the east Thermopolis area, Hot Springs and 'lfashakie Counties, 'lfyoming. United States Geological Sun,e,v, Oil and Gas Investigations Map OM-213. Washington, D.C.: GPO. 'W. 1961. Die Gliedmassen und Gliedmassenguortel der SauJanensch, ropoden der Tendaguru-Schichton. P aleontograph ica, supp. 7, 3: 1 80235. Jennings, D. S. 2002. Detailed sedimentary and taphonomic analysis of a dinosaur quarr\., Hot Springs Ranch, !(yoming. Journal of Vertebrate Paleontology 22 (supp. to 3): 71A. Locklev. M. L. 1991. Tracking Dinctsaurs: A New Look at an Ancient World. Neu, York: Cambridge University Press. Lull, R. S. 1919. The sauropod dinosaur Barosaurus Marsh redescriptions of the t,vpe specimens in the Peabody Museum, Yale University. Memoirs of the Connecticut Academy of Arts and Sciences 6: 542 Marsh, O. C. 1883. Principal characters of American Jurassic dinosaurs. Part 6: Restoration of Brontosaurtrs. American .[ourndl of Science, ser.
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ser.
3,27: 161-167.
1896. The dinosaurs of North America. United States Geological Suruel, Annual Report 16:135-244. Mclntosh, J. S. 1990a. Sauropoda. In D. \Teishampel, P. Dodson, and H. Osm6lska, eds., The Dinosaurid, 345-401 . Berkelev and Los Angeles: Universitl' of California Press.
1990b. Species determir.ration in sauropod dinosaurs. In K. Carpenter and P. J. Currie, eds., Dinosaur Systematics: Approaches and Perspectiues, 53-69. Cambridge: Cambridge University Press. Mclntosh, J. S., \)tr P. Coombs, Jr., and D. A. Russell. f992. A new diplodocid sauropod (Dinosauria) from \ff/yoming, USA. lournal of Vertebrate Paleontology 12: 1 58-167. Mclntosh, J.S., \7.E. Miller, K. L. Stadtman, and D. D. Gillette. 1996a. The osteologl' of Camdrasaurus leuisi (Jensen, 1988). BYU Geologl'
JtttAtes+li /J-lIJ. Mclntosh, J.S., C.A. Miles, K. C. Cloward, and J. R. Parker. 1996b. A new nearl,v complete skeleton o{ Camarasdunts. Bulletin of Gunma Museum of Natural History 1: 1-87. Mclntosh, J. S., and K. Carpenter. 1998. The holotype of Diplodocus longus, with comments on other specimens of the genus. Modern Geology 23: 85-1 10. Osborn, H. F., and C. C. Mook. 7921,. Camardscturus, Amphicoelias, and other Sauropctds of Cctpe. Memoirs of the American Museum of Natural Histor1., new series, vol. 3, part 3. New York: American Museum of Natural History. Ostrom, J.H. f970. Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and
First Articulated Manus of Diplodocus carnegii
.
31.9
Montana. Peabodl, Museum of Natural History Bulletin
35
162-
164.
Ostrom, J. H., and J. S. Mclntosh. 1999. Marsh's Dinosaurs: The Collections from Como Bluff. New Haven, Conn.: Yale University Press. Tidwell, V., K. Carpenter, and S. Meyer. 2001. New Titanosauriform (Sauropoda) from the Poison Strip Member of the Cedar Mountain Formation (Lower Cretaceous), Utah. In D. H. Tanke and K. Carpenter, eds., Mesozoic Vertebrate Lfe, 139-166. Bloomington: Indiana University Press. Upchurch, P. I995. The evolutionary history of sauropod dinosaurs. p/:l/osophical Transactions of the Royal Society of London, series B, 349: 365-390. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of tbe Linnean Society 124:43-1,03.
320 . Malcolm \fl. Bedell Tr. and David L. Trexler
L
5. Evolution of the Titanosaur Metacarpus SeeesrrAN Appsrecuie
Abstract The manus in the neosauropods trended toward a tubular configuration very early in their evolution. Although basal titanosauriforms show a trend toward lengthening of the metacarpals and reduction of the phalanges, titanosaurs went further. Their metacarpais all assumed a similar shape, became long and robust, and they completely
lost their digits. The metacarpals were vertically arranged into a completely tubular structure, and were connected to each other by their proximal and distal epiphyses. This graviportal adaptation was enhanced by enlarging metacarpal V so that it was subequal to metacarpal I, and modifying the distal ends of all metacarpals so that
they were square, widened laterally, profusely pitted, and flat. In some titanosaurs, metacarpal I is bowed and retains an asymmetrical, short first phalanx and ungual, which is lost in derived species. This bowing occurs in Andesaurus and Argyrosaurus, and might be a synapomorphic character for Titanosauria, which was reversed in more derived forms. If true, the persistence of a large ungual in the digit I of some species and the bowed metacarpal could be related to each other both phylogenetically and functionally. .)-L 1
The eiongate metacarpal V faced metacarpal I on the posterior side of the manus, thereby forming a tubular arrangement. Intermetacarpal contacts developed flanges distally on metacarpals II and III. In proximal view, meracarpal I varies, from a D-shape to flat outlines; the second and third metacarpals are robust and wedge-shaped; the fourth metacarpal is biconcave and squareshaped; and the fifth metacarpal is a twisted, clepsydra-like bone
with flat epiphyses.
The titanosaur carpus resembles that of basal titanosauriforms and seems not to be homologous to that of diplodocoids. It comprises both proximal and distal elements. A number of features make titanosaurs unique among Sauropoda, including redevelopment of the olecranon, lateral expansion of the ilia. bowed opisthocoelous dorsals, loss of hyposphene-hypantrum articulations, reduction of the forelimbs, enlargement of the sacrum, and the presence of osteoderrns, and some of these features might be relatec to the nest-excavation by advanced titanosaur sauropods.
Introduction The appendicular structure of most vertebrates is different between the manus and the pes. This is particularly true of bipeds, where the manus developed specialized functions (e.g., prehensility, manipulation, digging). In quadrupeds, however, the fore- and hindlimbs are more similar. Descended from bipedal ancestors (Bakker 1977; Bonaparte 1982), quadruped dinosaurs have secondary modifications for quadrupedal locomotion, thus departing from the original archosaurian bauplan. In bipedal basal theropods and facultative bipedal prosauropods, the primitive saurischian manus has short metacarpals that are no more than 40o/" of the radius length (Sereno 1993). The manus, not significantly different in srructure from the pes, is composed of sprawling metacarpals that allowed it to resist multidirectional stress under moderate weight. In non-neosauropod sauropods, the pes and manus also are not well differentiated (Fig. 15.1C), although this has changed in neosauropods. To give context to these differences, the sauropod pes is described first. The pes apparently arose from a sprarvling prosauropod-iike autopodiai, as evidenced by tracks (Fig. 15.1A) and skeletons (Fig. 15.1B). However, the sauropod pes differs from that in prosauropods in that it is semi-plantigrade. The pes also resembled that of ertant elephants in possessing a large cushioning pad that made the pes a large, semicircular, stabilizing device (Bonnan 1999;'this volume). The ungual phalanges are twisted laterally in a manner similar to that of tortoises for traction (see Bonnan this volume). The weight-induced spread of the feet is prevented by well-developed posterior flanges on the metararsals (e.g., Patagosaurus). The astragalus is the only functional rarsal, allowing pes mobility in Apatosaurus, but it is slightly reduced in Camarasaurus (Bonnan 1999). Expanded articular facets and loose-fitting articulations show that the pes was able to walk on uneven terrain, with
322 .
Sebastidn Apesteguia
A
B
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#'
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j; [i(r ,,ir'' " ?t' Ylt-
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D
ii
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tdJ)
Jffiq
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,4-* - f-\
@
i,k f-S
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Fig. 15.1. A: Pes (top) and rnanus b ottr,tm ) of diu er s e q uadr ttp e da I tetrapods. (A) Prosaurctpod tracks (from Thulborn 1990). (B) lvlassospondylu s atrt op o dia (fr om Thulborn 1990). (C) Cetiosaurus leed:i rBMNH Rl0-81 manus in dorsal uietu. D-G: Mammalia (
H
autopodia (from Marsh 1876, 1893 ): (D) Brontotherium; /E/ Coryphodon; fF) Dinoceras; (C)
f#
K
r-*\ 1\
'd,V
Elephas. H-N: Sauropod dinosaur atiopodid. H, J, L, M:
Apatosaurus (from Gilmore 1936): (H) Pes in dorsal uieu,; 0) metdcarpals in proximal uiew; (L) tnonus ds found; (M) ftranus as reconstrLtcted with no tttbular arrdngenlent. l, K, N; Janenschia (from Bonaparte et dl.2000; Jdnensch 1961): (I) Pes in dorsdl uiew; (K) metdcdrpdls in prr:ximal uieu': (N) nldnus .ts reconstructed. Figttres were re-scaled dnd reuersed fur ease of comparison.
the claws as anti-slip devices (Bonnan 1999). The sauropod pes,
with its non-uniform metatarsal length and asymmetrical entaxonic structure, is not comparable to that of ungulate or subungulate mammals. Even in derivative sauropods, such as Titanosauriformes, the pes underwent no major changes during their phylogenetic history despite major changes in the hip, development of a wider gait (Wilson and Carrano 1999), and rotation of the tibiae (Salgado et al.7997). Evolution of the Titanosaur Metacarpus
.
323
In contrast to the pes, the manus followed a very different trend. The sauropod metacarpus looks more similar to that of the hippopotamus, rhinoceros, or Brontotherium (Fig. 15.1D) rhan it does to that of the more plantigrade elephant manus (Coombs 197 5). Only in the abbreviated phalangeal segment does the sauropod manus resemble that of the eiephant (Bakker 7971). Other differences can be found in the loss and/or fusion of carpals, which are flat and wide in sauropods, and in loss of the olecranon on the ulna so that the forelimb is more graviportal. Because the radius and ulna are interlocked proximally in sauropods, pronarion of the manus was achieved by the medial position of the radius with respect to the ulna (Huene 7929; Bonnan 1999) and may have led to the development of the tubular arrangement of the manus (Bonnan 2003). Early in sauropod evolution, the radius migrated medially to form part of a columnar forearm, differing from the crossed radius and ulna seen in other tetrapods (Hatcher 1902). Because digit I migrated with the radius, the sauropod manus acquired a unique U-shape in cross-section (Bonnan 7999), formed by long metacarpals rearranged vertically (Figs. 15.1J, K; 15.3). The analysis of Bonnan (2003) concluded that several features of the forelimb considered independently in phylogenetic analyses constitute an integrated functional suite, which probably evolved together; and the presence of one feature strongly suggests the presence of others.
These features include obligatory quadrupedal posture with columnar limbs (Wilson and Sereno 1998); proximal end of the ulna tri-radiate, with deep radial fossa (\Tilson and Sereno 1998); distal condyle of radius subrectangular, with a flat posterior margin for ulna (\X/iison and Sereno 1998); and the proximai end of the metacarpals are subtriangular, so that the articulated manus is Ushaped in proximal view (Mclntosh 1990; Upchurch 7995,1998;
\Tilson and Sereno 1998). Although Bonnan (2003) may be correct in a broad view, the small individual changes in the forelimb anatomy and their functional consequences resulted in important differences along the sauropod lineages. These differences will be analyzed here within the context of the metacarpus, with oniy occasional mention of the implication to the whole forelimb. I will show the distinct features present in the titanosaur manus, and consider the carpus, metacarpus, and phalanges in a phylogenetic context. The absence of manual phalanges in titanosaurs, mainly based on negative evidence, is discussed, as weli as the possible of claws. The relationships of these features and the acquirement of graviportalism and large body size are evaluated.
presence
Institutional abbreuiations. MACN-Museo Argentino
de
Ciencias Naturales "Bernardino Rivadavia." Buenos Aires. Argentina; MLP-Museo de La Plata, La Plata, Argentina; MPCAMuseo Provincial "Carlos Ameghino," Cipolletti, Argentina;
MPCF-Museo Provincial "Carmen Funes." Plaza Huincul. Neuqu6n, Argentina; MUCPV-Museo de la Universidad del Co-
mahue, Neuqu6n, Argentina; UNP-Universidad Nacionai de la
324
.
Sebasti6n Apesteguia
Patagonia "San Juan Bosco," Comodoro Rivadavia, Chubut, Argentrna.
Materials and Methods Known articulated or closely associated metacarpi include part of the right and left metacarpi of Chubutisaurus insignls (MACN 18222), the left manus of Argyrosaurus superbzzs (MLP 77-V-291), the right of Antarctosdurus tuichmannianus (MACN 6804a), the left of Laplatasaurus (MACN 6804b), the right and left of Epachthosaurzs (UNP-PV-920), the right of Aeolosaurus rionegrinzs (MJG-R1), and an isolated but articulated right titanosaur metacarpus (MPCA 110-51). Poorly preserved but associated metacarpals include the first and fifth metacarpals of Andesaurus delgadoi (MUCPV-132), the second and third metacarpals of a new basal titanosaur species from the Aptian of Neuqu6n (MCF-PVPH-
233), a poorly preserved metacarpus from the Turonian of Neuqu6n (MCF-PVPH-638), and the single metacarpal of Aeolosaurus sp. (MPCA-27774). Materials assigned by Huene to Neuqttensaurus australis also consisted of isolated elements. For outgroup comparison, examples from the literature r,vere used, including Cetiosaurus /eedsl (BMNH R3078), diplodocoids (e.g., Ap(ltosaLrrus excelsus, CM 563), basal macronarians (i.e., CantaraslLrrus supremus, AMNH 711) and titanosauriformes (e.g., Brachiosaurws, Venenosdurus, Atlasaurus and Alamosaurus). The phylogenetic framework used is based on Salgado et a|. (7997), Sfilson and Sereno (1998), 'Wilson (2002), Wilson and Upchurch (2003), and Salgado (2003).
Considering that every metacarpal has a different position within the metacarpus, and in order to follow a consistent description, the metacarpals are considered to be parallel. Thus, for a given metacarpal, the proximal and distal ends refer to the ends that face the carpal and phalanges respectively, even when the latter elements are absent. The anterior and posterior sides in the tubular structure of the sauropod manus are equivalent to the outer and inner (palmar) sides. The terms "medial" and "iateral" are considered in the same way and refer to the complete forelimb position. No comparative methods were used, such as the Extant Phylogenetic Bracket; that will be done somewhere else. Reconstructions of the metacarpal structure were made from my own observations. Titanosaur Manus Carpus. Because of its block shape (Wilson and Sereno 1,998, ch. 42) and reduced number (Mclntosh 1990; Upchurch 1998; \7ilson and Sereno 1998, ch. 79), the identification of the carpal bones in sauropods is problematic. The studies of Osborn (1904) and
Hatcher 11902) show the carpals are not always homologous. In Apatosaurus, the carpal has two proximal facets for the radius and ulna, and it is only loosely placed above metacarpals II-IV (Osborn 1904; Fig. 15.2A). In Camarasaurus, on the other hand, the larger Evolution of
tl-re
Titanosaur Metacarous
.
325
-U
H ffir$ LJ
"_u Fig. 15.2. Sauropod left wrist in dorsal uiew. /A/ Apatosaurus excelsus (CM 563). (B) Camarasaurus supremus (AMNH 711). (C) Atlasaurr-rs imelakei. /D) Argyrosaurus superbus (MLP 77V-29-1). Not to scdle.
{rl
frdnn\\
!
U
frdnnt1
of two carpals fit closely to metacarpals I and II. This placement identifies it as a distal carpal. However, the smaller carpal between the ulna and metacarpal V makes its identification problematic (Fig. 15.2B). Other macronarians with carpals are the basal titanosauriform Atlasaurus (Monbaron et al. 7999) and the advanced titanosaur Argyrosaurws (Lydekker 1893). In the former (Fig. 15.2C), as in Camarasauras, there are also two carpals, and the position of the larger carpai over metacarpals I and II is similar to that of Camardsaurus (actualln there is a "step" in the carpal because metapodials range in height). The smaller carpal is closely associated to metacarpal III, thus is different from that of Camdrdslurus. Two carpals were described in titanosaurs early in the twentieth century (Huene 7929), but successive authors have ignored this information and proposed that "no carpals are known in titanosaurs, and it is possibie that they were not ossified" (Borsuk-Bialynicka 1977); "titanosaurs appear to have eliminated any ossification of the carpus, as evidenced by the lack of carpals in
that preserve all of the other bones of the forelimb" (Wilson and Sereno 1998). Two carpals are present in the well-preserved left forelimb of
specimens
Argyrosdurus (Fig. 15.2D). Unfortunateln the humerus and metacarpals remained in situ, but the ulna, radius, and carpals twisted prior to burial. The smaller carpal (the ulnar of Huene 7929) rs still attached to the distal end of the ulna and was probably associared with metacarpal V. The larger carpal (composite radial of Huene 1929) is attached to the proximal ends of 326
.
Sebasti6n Apesteguia
III-V, but this was the result of the twisting of the forearm, and should be associated with metacarpals I and II or I-III, as well as the radius. Porvell (2003) mentioned the existence of a carpal in the distal ulnar side of the radius, but I do not know if he is referring to a previously unidentified carpal. The close association between the smallest carpal and the ulna suggest that this carpal is the ulnar, a proximal carpal, whereas the larger carpal, closely associated to the metacarpals, represents the fusion of smaller, distal carpals. Tubular mlnus and metacarpal enlargement. The metacarpals of most sauropods are arranged in a half-cylinder (Fig. 15.3B-L) or 270" arc ('Sfilson and Sereno 1998). This U-shape was acquired early in the sauropod evolution and is related to weight support metacarpals
(Christiansen 1997). This unique organization prevents the metacarpals from splaying apart distally and is a graviportal adaptation that is well documented in the ichnological record as an
open half-moon track (Fig. 15.3A; Lockley 1991). However, two additional and probably related changes took place: lengthening of the manus and loss of the digits. In the early sauropod Vtrlcanodon, the longest metacarpal is about 32'/. the length of the radius, and this low value is also seen in the Dipiodocoidea (Gilmore 1936). The manus, already differentiated from the pes, was too short to be considered as a separate segment in the forelimb, but served as a wide, supporting base for the forelimb. Within the Macronaria, the metacarpals are twice the length of the metatarsals and are almost half the length of the radius (47% in Camarasaurus). Macronaria metacarpals are long and robust (Fig. 15.3C), but they do not achieve the substantial enlargement seen in titanosaurs, nor is there
a reduction in the digits. Titanosauriformes exhibit the
largest
metacarpal:radius ratio (see Table 15.1). Furthermore, most of the basal titanosauriform metacarpals not only are proportionally long and slender but also are not yet as robust as those of advanced titanosaurs (compare Figs. 15.3D, E, F, and 15.3I-K). The small, complete metacarpus MACN 6804b of Laplatasaurus (Fig.15.4G) is formed by five remarkably slender metacarpals that are heterogenous. The metacarpals are as slender as those of Bracbiosaurus, AtIasaurus, and other basal titanosauriforms (Fig. 15.3D, E, F), suggesting that this taxon could be a relatively basal titanosaur despite its young stratigraphic position (Lower Campanian). In most of the crown-group Titanosauria, the metacarpals are very long and secondarily robust (Fig. 15.3J, K, L, M), except in the very derived saltasaurines and Opisthocoelicaudia, where the metacarpals apparently became secondarily short (Fig. 15.3J, K). Oueruiew of the manus. Some degree of tubular arrangement of the metacarpal was already present in early eusauropods (e.g., Omeisaurus) as an open arc (Bonnan 2003). Some neosauropod groups still retain this primitive open arc, as evidenced by an
unidentified Late Cretaceous ichnotaxon having a 1:3 to 1:4 heteropody (Fig. 15.3A). This track may have been made by a basal diplodocoid \e.g., "Rebbachisaurus"). Other neosauropods show F,volution of the Titanosaur Metacarpus
.
327
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TABLE 15.1. Longest Metacarpal:Radius Lengths Ratio Longest metacarpal:radius length ratio
Taxon " Rebb ach
isaurus
"
te ss
onei
0.36
s b rancai Cb ubutisaurus insignis
0.51
cl. Epachtbosdurus sp.
0.56
Alamosau rus
0.51
B r d ch i os a urtt
sa n j
ua
0.54
rtc n si s
Aeolosaurus sp. Ae olo
saurus r ione grinus ( MJG-R1
O p isth
o
coelica
udia s karzy ns k ii
0.53 )
0.53 0.46
an advanced reorganization of the metacarpus, with metacarpals I and V opposed to each other in proximal view. This advanced organization is seen in both diplodocoids (e.g., Apatosaurus) and macronarians (e.g., Cantarasaurtts, BrachiosaLtrLts, titanosaurs). Diplodocoid neosauropods (e.g., Apatosaurus excelsus) show short, heterogeneous metacarpals (Gilmore 1936) that only contact each other proximally. The heterogeneity of the metacarpals are as-
sociated with numerous, well-developed phalanges. The basal macronarian Cdmardsdurus and basal titanosauriforms show a major length difference between the longest metacarpals (II and III) and the outer ones, metacarpals I, IV, and especially V. This difference is associated with the retention of digits between the metacarpals and ground (Bonnan 2003, fig. 2b). Macronarians show less difference between the fore- and hindlimbs than the heteropody seen in diplodocoids. These differences are apparent in tracks assigned to different ichnotaxa (Lockley et al. 1994). The Parabrontopodidae are narrow-gauged tracks, with the center of the manus prints placed farther from the trackway midline rhan are
the centers of pes prints. They are mainly represented by Breuipdropus (Dutuit and Ouazzou 1980), and are widely distributed in Jurassic strata. The Brontopodidae, on the other hand, mainly represented by Brontopodus, is a wide-gauge ichnotaxon that is common in Lower Cretaceous strata and has also been reported from the Upper Cretaceous (Leonardi 1984). The assignment of parabrontopodid tracks to the diplodocoids, and the assignment of brontopodid tracks to macronarians, is far from certain, but the stratigraphic distribution suggests this possibility. V/hat about the manus of titanosaurs? ril/ould they have produced a half-moon track similar to that of diplodocoids or a semicircular one, as reported by Calvo (1991) as Sauropodichnus, comparable to Breuiparopus as discussed by Farlow et at. (1989). Calvo (pers. comm.) has suggested that Sauropodichnus could be subtracks of the hind-feet, not semicircular manus prints. However, osteological
Fig. 15.3. (opposite page) (A) \Mell- p r e se r ued sa w ro p od foot p r i nt from Cenomanian outcrops of Patagonia shouing a high heteropody and metacarpals I and V not opposing. B-J: Sauropod tndnus on proximal (top) and
anterior (bottom) uieuts in tbe
framet'ork of a cladogram consistent wtth Wilson (2002) analy sis. fBl Apatosaurus (Gilmore 1936); (C)
Camarasaurus (Osborn 1904); /D/ Brachiosaurus (from Janensch 1922); (E) Atlasaurus fron Monbaron et al. 1999); (F) Venenosaurus drcr ocei ( fr o m
Tidwell et a\.2001); (G) Chubutisaurus insignis; /H/ cf. Epachthosaurus (Powell 1990); (I) Alamosaurus sanjuanensis (modified from Gilmore 1916); (J) Opisthocoelicaudia skarzynskii ( m o difi e d fr o m B or su k-B i alyni c ka 1977 ). (K) Neuquensaurus australis tfrom Huene 1929, after the skeleton displayed in the MLP; with the metacarpal III reconstructed). (L) Sch eme showing the titanosaur nonp h alan ge d m etd c ttrp al str u ctur e. tMt Stottchcnge ruins. (Nt Lirst manual ungual phalange of Camarasaurus on lateral and medial uiew (flom Ostrom and Mclntosh 1966). (O) First manual ungual phalange o/ Brachiosaurus brancai in lateral uiew (from lanensch 1929). (P) First manual ungual of Janenschra in ldteral uiew (from .lanensch 1929). Figures were re-scaled and reuersed for ease of compdnson.
Evolution of the Titanosaur Metacarous
.
329
TABLE 15.2. Metacarpal Measurements and Robustness Index (RI) as Determined by Minimum Circumference
(mc)/Length (L)
Taxon
McI LmcRI
Mc II NIc III LmcRiLmcRILmcRI
Apatosaurus louisae
27
28.5
29.3
24.5
23.5 49
Br ach io saurus
brancai SII
Nlc lV
lt-)c
60
63.5
59..5
57
Br ach iosaurus brancai R
37
40
39..5
36.5
ubutisaurus insignis
43
Cb
n-
25
Aptian of Cerro Leon, Neuqu6n
^-
(MCF-PVPH-233) Andesaurus delgadoi (MUCPv-1 32)
+.)
Janenschia robusta
2.5
Ant ar cto s durus
w i ch
mannianus
38
Cf. Laplatasaurus
25
Venenosaurus dicrocei
Cf.
Ep
29
Aeolosaurus rionegrirurs (MJG R1
19 11
0.5
0.4
17
0.6
4l
Alamosaurus sanj uanensis )
27
Opisth ocoelicaudia skarzynskii lleft) 29
0.5
47
0.5
42
RI
3i
22
0.5
0.4 37
28.1
13
achth o sazrzs (UNP-PV-920)
21
25 20
NIc V
17
.5
0.6
25.6
24.9
23.8
37.5 18 0..5 34 1.6 0.5 30 12 0.4 28 10.2 0.4 27 14 0.5 24 12 35.8 15 0.4 36 15.5 0.4 33.3 14.7 0.4 30.1 14.2 30 15.5 0..5 29 16 0.6 27 15.s 0.6 27 16.5 1A 40.9 39 35.7 25 18.5 0.7.11 18 0.6 30 16.5 0.6 29 18 L.1 ..'l 29 27.5 24.5
0.5 0.5 0.5 0.6
evidence indicates that the titanosaur manus was tubular and orob-
ably encased a complete, semicircular pad. Possible ichnological evidence has been reported from the Upper Cretaceous El Molino Formation, Bolivia and the Loncoche Formation, Mendoza (Fig. 1s.6A). The evolution of the manus from the long, slender, and relatively heterogeneous Brachiosaurzs metacarpals, to the advanced robust and homogeneous Late Cretaceous titanosaur metacarpals, mainly involves metacarpal V and the loss of the digits (Table 15.2). This loss of digits is not based on negative evidence, but rather on the presence of deformed lumps of bone at the end of metacarpal IV that have been interpreted as remnanrs of a phalange (Gimenez 1992). Other changes are seen in the size and proportions of the diaphysis (e.g., stoutness, straighrness, rela-
tive length of individual metacarpals, facet
shapes, lateral processes). The metacarpals of diplodocoids and basal macronarians have a slight, lateral curve and proxirnally have large, intermetacarpal articular surfaces, but none distally. This demonstrates that these metacarpals were closely articulated proximally, but were slightly separated distally and united in a crescentic pad. In basal macronarians an increase in the diaphysis length is seen, and the metacarpals are rearranged in a more tubular structure. However, the distal ends remain free and articulate with phalanges. Some basal titanosauriforms, such as At-
330
.
Sebastidn Apesteguia
,I
y',t
cT
-.
Fig. 15.4. A-B: Metacarpals of an indet erminat e titano s aur MCF -
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-..*,
ry re m w
PVPH-638: (A) distal half shotuing the lateral flange and the llat distal end; (B) proximal half shotuing the limited and short proximal contact surface and the proximal end. C-G: Metacarpal lV in titanosaurs. (C) MPCA 11051 in posterior, Iateral, and anterior uieus; (D) Chubutisaurus in medial, lateral, proximal, anterior, and posterior uiews, (E) MCF-PVPH-638. (F) Antarctosaurus wichmannianus rn medial, lateral, proximal, and anterior uiews. (G) Cf. Laplatasaurus in medial and lateral uieus, Figures uere rescaled and reuersed for ease of comparison. Scale bar: 50 mm. Abbreuiations: c{ = tontact t'atet: 11 = lateral flange.
lasaurus, Venenosaurus, and Brachiosaurtts, exhibit long, straight, and slender metacarpals (Fig. 15.3D, E, F), with reduced intrametacarpal contact proximally, and a slight distal contact.
Both basal and advanced titanosaurs (e.g., Chubutisaurws) show long, but robust, metacarpals with both proximal and distal intermetacarpal contacts that are l/a of the metacarpal length (Fig. 15.3G-I). Restricted contact surfaces preserved in some specimens, as in a titanosaur (Fig. 15.aB) from the Turonian of Sierra del Portezuelo (MCF-PVPH-638; Apesteguia, in preparation) , Alamosdurus (Gilmore 19461, and cf. Epachthosaulzs, show that the distal intermetacarpal contacts were mostly restricted to the epiphysial region. The distal contacts of the titanosaur metacarpus forms a structure much more closed or tubular than in other neosauropods (Fig. 15.3L), with the metacarpals being in slight contact in both the proximal and distal regions. Lateral flanges on the metacarpals (described below) are also developed in some species of Titanosauria, such as Chubutisaurus.
Evolution of the Titanosaur Metacarous
.
331
Another change during the transition from basal macronarians to titanosaurs is the flattening or slightly convex distal metacarpal trochlea. This change, associated by some authors ro the loss of digits (Gim6nez 1992; Salgado et al. 1997), also occurs in the possible brachiosaurid Venenosaurus (Tidwell et al. 2001, 150). Metacarpals. In titanosaurs, meracarpal I is highly variable. In several neosauropods, such as Apdtosdurus louisae (Gilmore 1936), Camarasaurzs sp. (KUVP 129713; Bonnan 2003, fig. 2a), and basal Titanosauriformes (e.g., Brachiosaurus brancai, Janenschia robusta), the proximal end is a massive D-shape, with the long, straight edge in articulation with metacarpal II. In titanosaurs, some taxa retain this primitive shape (cf. Laplatasaurus, .lanenschia, Alamosaurus, Opisthocoelicaudia; see Fig. 15.5S, T). Other taxa (Argyrosaurus superbus, Andesaurus delgadoi, MCFPVPH-638, and MPCA 11051) show a compressed proximal end. The basal titanosaur Chubutisaurzs (MPCA 11051) and the possible brachiosaurid Venenosdurus (Tidwell et al. 2001) show an intermediate stage, with the proximai region divided in two portions: a thicker posterior region that projects into the central part of the metacarpus, and a narrower, curved part with a concave surface to articulate rvith metacarpal IL The medial surface is convex, resulting in a colonnade aspect. The diaphysis of metacarpal I of titanosaurs is slightly flattened, showing two ridges, the anterior sharper than the posterior. The medial side of the shaft is slightly concave and the lateral slightly convex. Proximally, a convex facer (especially in Chubutisaurus) faces the external side and tapers to a small wedge (curved in basal titanosaurs, straight in derived forms) that medially covers part of the anterior side of metacarpal II. This covering surface is concave both in primitive and derived forms, but in cf . Laplatasaurus is poorly developed and is only slightly concave. The posterior or palmar side of metacarpal I is flat in all taxa. In Cbubutisdttrzs the entire metacarpal is not as anteroposteriorlv compressed as in more derived forms. This feature is perhaps linked to the reduction of the proximal end of metacarpal I in the lineage. Two ridges extend down the diapophysis to the distal articular condyle, one from the posterolateral corner and the other from the anterolateral corner. As in most neosauropods, metacarpals II and III are the most massive of the elements, and they form robust triangular wedges in proximal view, with the apex on the palmar side. In diplodocoids, the proximal end of metacarpai II is a large, rounded pentagon; it is a trapezoid in some basal titanosauriforms and a weli-developed triangle in advanced titanosaurs. This triangle has a convex medial side, which articulates with the concave surface of metacarpal I, and a flat lateral side. The diaphysis has two ridges that give the shaft a squared cross-section. They extend from the prorimal corners and extend along the palmar side to end together near the lateral condyle. The anterior face of the second metacarpal is not as convex as the third, but flat. The distal region of the diaphysis has a medial flange that slightly covers the distal region of the first
332
.
Sebastidn Apesteguia
'l'lnr ;tt-:, 'r . ii{ \..,'-.... l-.:-i .i:
A
L
,,
w
->' I[ -L-
,filJ
.(,lll [l
M
%
ffi o
r,1\S \{*y
R
S
,i:3 /"':a::) '-'-.
A:--.''
it", f\,...,)'
I
., l,/'.
\aN/
- ' - 'ttit"' Fig. 15.-1. A-E: Neosauropod first metacarpal in anterior uieu, in the context of a cladogram. Proximal and distal uiews were ddded tuhen auaildble. /Aj Apatosaurus excelsus (from Ostrom and Mclntosh 1956); (B)Camarasaurus supremus; /C/ Austrosaurus mckillopr (from Coombs artd Molnar 1981); (D)Phurviangosaurus sirindhornae (from Martin et dl. 1999); (E) Chubutisaurus insignis. F dnd H: Two titanosauriform sauropods with strdight first metacarpal. (F) Brachiosaurus; (H) C/. Epachthosaurlrs (with hypctthethical reduced phalanges added in gray; only one uas found). G and I: Two titdnosattrifrtrm sauropods uith bowed first metacarpal. /G/ Janenschia (frorn Janensch 1961); (I) Argvrosaurus (tL,ith btpothetical reduced phalanges addetl in gray). J-O: Titanosaurs uith botued metacarpals. J-K: Bowed second metdcdrpdl. (.J) MCI-PVPH-233, new taxon from tbe Aptian of Neuquin (Bondpdrte et al. submitted); (KJ Antarctosaurus. l-O: Boued first metacarpal. (L) MCF-PVPH-638, neu taxon from the Turonian of Neuqudn (Apesteguia irt prep.); (M/ Andesaurus; (NJ MPCA 110.51; (O)Argr.rosaurus, drticuldted metdcarpus showing the botued first metacdrpdl. P-T: Titanosaur metacarpals in 1)roximdl uiew in the context of a generalized cladogram. P, Q, and R are re;tresented as unresolued becduse they are not commonly included together in comprehensiue analyses. (P) Argyrosaurus; (Q) MPCA 11051 (R) C/. Epachthosaurus; /S/ Alamosaurusl /T/ Opisthocoelicaudia. First metacarpdl is shown in grdJ'to check the reuersal chttnge in shape. Figtres uere re-scaled and reuersed for ease of comparison.
Evolution of the Titanosaur Metacarous
.
333
metacarpal in Chubutisdurus, Epachtbosaurus, and the specimen from the Portezuelo Formation (Fig. 15.4A, B, D). Metacarpal III is triangular in proximal view, with a straight or concave edge on the anterior side. The posterior or palmar side has two surfaces for metacarpals II and IV that meet to form a strong ridge, which in turn meets a medial ridge. Near the distal epiphysis, the ridge borders a strong concavity having a lateral "step," afrer which the ridge is vertically oriented toward the condyle (Chubwtisdurus). The distal region of the diaphysis has a medial flange that slightly covers the distai region of metacarpal IV in Chubutisaurus and EltachthosAurus.
Metacarpal IV is the most characteristic of the metacarpals, being subrectangular with its two longer sides concave for the proximal ends of metacarpals III and V. There are prominent ridges at the margins of both sides. The anteromedial ridge has rough muscular attachments. Both lateral and medial sides of the diaphysis are concave, and the distal portion has a medial flange that slightly covers the fifth metacarpal in Chubwtisaurus, Epachtbosaurus, and advanced titanosaurs.
Metacarpal V is variable in sauropods, and in titanosaurs it commonly has a proximally flat outline, with ridges delineating the two flat sides (Fig. 15.6G-I). The external side bears a ridge at the middle that extends along the twisted diaphysis, ending near the lateral condyle. The twisting of the shaft gives it a clepsydralike shape, with rather flat epiphyses (e.g., Andesaurus) attached to the posterolateral border of the manus. In contrast to many tetrapods and non-sauropod dinosaurs, metacarpal V is an important part of the manus, and shows no reduction in size. In most sauropods, this metacarpal is slightly shorter than others, whereas in titanosaurs, it is the same size. Bowed metacarpal 1. The first digit of basal titanosauriforms still retains a large ungual phalanx. In form, metacarpal I is not significantly different from that of other neosauropods. However, /anenschia has a slightly bowed metacarpal that is associated with an asymmetrical, short first phalanx and ungual. The bow is such that the claw is almost in contact with the metacarpal (Fig. 15.5G). Within the Titanosauria, most taxa have metacarpals that are the same length. However, Upchurch (1994) noted that metacarpal I in Opisthocoelicdudia and Alamosaurus (Fig. 15.5I, J; 15.6F) is the longest. In addition, their diaphysis is straight, as it is in Epachthosdurus (Figs. 15.3H; 15.5H; 15.6E) and derivative saltasaurines (Fig. 15.3K). In the basal titanosaur Andesaurus delgadoi (Fig.
15.5M), metacarpal
I is bowed
anteriorly, breaking the tubular
structure of the metacarpus (Fig. 15.3J-O). This "banana-shaped" metacarpal is also present in huge, robust, derived titanosaurs, such as an unnamed taxon from the Turonian of Neuqu6n (Fig. 15.5L; Apesteguia in prep.) and in Argyrosaurtts superbus Lydekker 1893 (Fig. 15.50). The presence of the bowed metacarpal, strongly asymmetrical first phalanx, and ungual in several titanosaurs suggests that the bowed metacarpal in Janenscbia (Fig. 15.5G) is not
334
.
Sebasti6n Apesteguia
B
@
Fig. 15.6. (A) Upper Campanian tracksite in outcrops of the Lonco ch e F ormation (Mendoza, Argentina). B-C: Titanosaur third metacarpals. (BJ Chuburi>aurus lr proximal and postero-lateral uiew; (C) MPCA 11051 in proximal and anterior uiews. D-F: Tftanosauriforrn metdcdrpus in posterior uiew to check the large size oI lifth meta(arpal dnd ils close spatial relation with tbc first.
al.
(D/ Janenschia; /E/ Cf, Epachthosaurus. /F,) Opisthocoelicaudia. G-I: Titanosaur fifth metacarpals. (G) Andesaurus in lateral and medial uiews; (H) MPCA 11051 in anterior, medial, and proximal uicws: rlt C/. Epachthorauru: irr lateral uieu, Figures tuere re-scaled and reuersed for ease of compdrtson.
taphonomic and may have arisen to maintain the claw. The retention of the ungual on the first digit in some titanosaurs could be related both phylogenetically and functionally to the bowed metacarpal (Fig. 15.5I). Once aquired, the bowed metacarpal may have persisted long after loss of the digits. Given the scoring of tl-ris feature within basal Titanosauria and some advanced titanosaurs, it may be a synapomorphic character for Titanosauria that was later reversed rn Epachthosdurus, Opisthocoelicaudia, and Alamosdurus.
As a side note, in a new taxon from the Aptian of Neuqu6n (Fig. 15.5J; Bonaparte et al. submitted), as well as in Antarctosdurus (Fig. 15.5K), bowing occurs in metacarpal II (metacarpal I Evolution of the Titanosaur Metacarpus
.
335
is unknown for the Neuqu6n taxon and it is straight in Antarctosaurus).
Phalanx loss and grauiportalism. Sauropods were graviportal animals, as evidenced by the column-like aspect of their limb bones. Flowever, the primitive sauropod metacarpus had not attained maximum graviportal development because it still retained digits. This development was only achieved when titanosaurs acquired enlarged, homogeneous metacarpals and lost the digits. The macronarran manus, typified by Camarasdurus, is tall and somewhat tubular. However, the metacarpals are heterogeneous in size and still retain phalanges (Fig. 15.3C). In basal titanosauriforms (Gim6nez 1992; Salgado et al. 1997), the manus shows a loss of phalanges, including a reduction of the manual claw I to less than 30% radius length in B. brancai (Fig. 15.3D). Further refinement is seen in basal Titanosauria where the metacarpals shor,v homogenization and a shallow development of the distal articular surfaces for phalanges (Fig. 15.5D, E, J, M). This modification is evident in Andesaurus delgadoi (Calvo and Bonaparte 1,991.), Phuwiangosdurus sirindhornae (Martin et aL 1994), Chubutisaurus insignis
(Del Corro 1975; Salgado 1993), and an Aptian form from
Neuqu6n (Bonaparte et ai. submitted). Metacarpal I of the putative titanosauriform Austrosaurus (Coombs and Molnar 1981) shows a well-developed, biconvex distal end that is similar to that of Camarasaurus and Apatosdurus (Fig. 15.5A-C). Basal titanosaurs probably still retained a poorly developed rorv of phalanges, as evidenced by a rudimentary phalanx found with metacarpal IV rn cf . Epachtosaurus (Gim6nez 1,992), and possibly a reduced first-digit claw. In contrast, the loss of the phalanges in advanced titanosaurs resulted in modification of the distal ends of the metacarpals so that they were rectangular, being wider than anteroposteriorly long, profusely sculptured, and not biconvex (Gim6nez 1992;Fig.15.5H; Salgado et aL.1997). The discovery of Rdpetosaurus krausei (Curry and Forster 2001) was at first thought to show the retention of relatively well developed manual phalanxes, but these were not found in articulation rvith the manus
and are now thought to be pedal phalanges (K. Curry,
pers.
comm.).
Titanosaur manudl clawsl The claws present in the nontitanosaurid autopodium, as well as in the pes, differ from the hoof-like unguals of large terrestrial herbivorous dinosaurs (Ceratopsia, Ankylosauria, Stegosauridae, Hadrosauridae), and also from the hooves of most large terrestrial mammalian herbivores (e.g., elephants). The claws more closely resemble those in some large herbivorous mammals (ground sloths, chalicotheres, homalodontheres), and very large predatory reptiles (carnosaurs) with cursorial behavior (Coombs 7975). The purpose of rhe claws in sauropods is unclear (Riggs 7904), although Coombs (1975) remarked, "if the pes structure of these animals indicates anything, it indicates specialization for terrestrial locomotion" (1-33). The trend toward loss of the phalanges raises the question as to 336 . Sebastiin
Apesteguia
whether titanosaurs lost all of them, including the claw of digit L The flat distai end of metacarpal I in all specimens (Fig. 15.5D, E), as well as the homogeneous size of all titanosaur metacarpals, seem to support this hypothesis. However, large, isolated, putative first manual claws were collected in Campanian outcrops of northern Patagonia (e.g., MLP-Av 2099; MACN 6804). If correctly rdentified, these would provide evidence for manual claws in derived titanosaurs or the survival of basal titanosaurs until Campanian times. However, considering that the titanosaur manus and pes is still not well known, it is possible that these claws mav be from the pes (Salgado, pers. comm.). The known titanosaur unguals found in articulation show that the first manual and pedal claws are clearly different. However, the other pedal claws are harder to separate from the manus claw. At this time, I cannot state for certain if all advanced titanosaurs lacked a manus claw. Phylogenetic significance of the manus. Although the discovery of articuiated but isolated anatomicai units, like forelimbs, positioned far from the rest of the skeleton, is rather common (Hunt et al. 1,994), their taxonomic placement can be difficult. Particular examples include the forehmb of Argyrosaurus superbus and the various Indian titanosaurs remains. Because these taxa are almost always excluded from phylogenetic analyses (Hunt et a\. 1994; Jacobs et al. 1993), they remain only partially studied. Most researchers (e.g., Porvell 2003; Upchurch 1995; Salgado et a|. L997; Wilson and Sereno 1998) obtained about 1'5'/. ol their cladistic characters from the appendicular girdie and forelimb (Table 15.3). Chatterjee and Rudra (1996) postulated that convergence could be most numerous in skeletal parts closely associated with feeding and locomotion and that such elements might be less informative phylogenetically (Bonaparte, pers. comm.). However, the number of characters of the metacarpus is underrepresented because of inadequate metacarpal description. The most important of these features are given in Table 15.3 and elaborated below Discussion The terrestrial behavior of sauropods is well established (e.g., Riggs 1904; Coombs 1975; Bakker 1977). The changes that occurred in sauropod phylogeny were mainly caused by allometric differences
(Long and McNamara 1997), and in titanosaur evoiution also included changes in locomotion. These changes include wide spacing of the limbs (wide-gauge tracks) and displacement of the center of mass (Christiansen \997) frrst seen in basal titanosauriforms. Studies of sauropod iocomotion involve biomechanics and comparative morphology with extant tetrapods. However, modification of the manus in titanosaurus into a long tubular structure, coupled with enlargement of metacarpals and loss of phalanges, has no modern analog.
The evolution of the limbs in sauropods is marked by an elongation of the forelimbs in basal titanosauriforms. For example, Evolution of the Titanosaur Metacarpus
.
337
TABLE 15.3. Characters from the Manus Used in Sauropod Phylogeny Character
Taxon
Reference
Bowed metacarpals
Sauropodomorpha Sauropodomorpha
Salgado et aL L997
Metacarpals longer than
metatarsals
Eusauropoda
Salgado et aL.1997 \ililson and Sereno 1998
Eusauropoda
Wilson and Sereno 1998
Manualnon-ungualphalanges,shape: Eusauropoda
\(/ilson and Sereno 1998
Carpal bones, block-shaped Manual digits II and III: phalangeal number reduction to 2-2-2-2-2 long or broad Manuai phalanx I-1, shape:
wedged
Metacarpal shape, spreading or
bound
(half-length of intermetacarpal articulations) (80); with subparallel shafts and expanded articular surfaces
Omeisauridae + (Jobaria Neosauropoda) Jctbaria
Metacarpal proxin.ral ends subtriangular, Jobaria composite proximal articular surface U-
+
\Tilson and Sereno 1998
f Neosauropoda
!(ilson and Sereno
* Neosauropoda
Mclntosh 1990; Upchurch lq95; Wilson and Serencr
shaped (81)
1998
1.998
Metacarpals, shape of proximal surface in articulation: 90' or 270"
Number of carpal bones, 2 or less Long metacarpals Length of longer metacarpal 45 percent or more than the radius (93) Metacarpal I subequal in length to metacarpal IV (94) Length of longer metacarpal 45 or more than the radius (93)
Wilson and Sereno 1998
Neosauropoda Ca mara sa
Salgado et aL.1997
uromorpha
*
Salgado et al. 1.997; Wilson and Sereno 1998
I
\X/ilson and Sereno 1998
t
Titanosauriformes
Salgado et al. 1,997; \X/ilson and Sereno 1998
Titanosauriformes
rWilson and Sereno 1998
Titanosauriformes
\Tilson 2002
Macronaria; Camarasaunts Tiranosa uriformes
Macronaria; Camarasaurtts Titanosauriformes
percent
Distal condyle of metacarpal I undivided, phalangeal articular surface re-
Macronaria; Camarasaurus
duced (98)
Metacarpalswithdistalendperpendicular to axis
Metacarpals with distal end almost flat Titanosauridae First metacarpal longer than the second Titanosauridae metacarpal
closed
Robust, long metacarpals. Actually this is a common reversal feature for most
Grm€nez
\992
Titanosauridae
\X/ilson and Sereno 1998 Powell 2003
Titanosauridae
von Huene 1929
Advanced titanosaurs
Powell 2003 lor Aeolosau-
Titanosauria Metacarpals of variable length Metacarpals folming a tall, ver,v tube
Gim€nez 1,992
rus
advanced titanosaurs (e.g. Chtrbutisau-
rus, Argyrosaurus) Carpus unossified
Opisthocoelicaudinae
Upchurch 1998
Nlanual phalanges unossified
Opisthocoelicaudinae
Gim6nez 1992; Salgado
and Coria 1993
the humerus:femur ratio in more primitive sauropods, the diplodocoids, is 0.6-0.7, and it is only 0.75 in the macronarian Camardsaurus supremus. In contrast, it is 0.8-1.0 Brachiosaurus brdncai, 1.01 in B. altithorax, and 0.8-0.99 rn Lappdrentosaurus maddgascariensis. This humeral elongation is accompanied by elongation of the lower arms and the metacarpus, with the metacarpal length up to 40o/o of the radius. This elongate forelimb is also seen in basal titanosaurs (Salgado et a\.7997; Bonaparte et al. submitted), such as a new taxon from the Aptian of Neuqu6n (humerus:femur = 0.9). Later titanosaurs, however, underwent a reduction of humerus length (e.g.,0.72 in Opisthocoel' icaudia), with a further reduction of metacarpal length in saltasaurines. Despite these secondary reductions in length, some of the basal titanosauriform characters remained. These include the angled sacrum (Brachiosaurws and derivative saltasaurines; Salgado et al. in press) and the laterally angled ilia (present in some basal macronarians, e.g., Camarasawrus lewisi; see also Tidwell et al. this volume). These peculiarities of the pelvis, coupled with the loss of the hyposphene and hypantrun-r (see Apesteguia this volume), probably allowed greater range of motion in advanced titanosaurs. In the columnar forelimb of titanosauriforms, the metacarpus became part of the column. This is in contrast to elephants and other graviportal synapsids in which the metacarpals only form the
expanded base
to the forelimb
column. The addition
of
the
metacarpus segment allows for longer steps in a manner analogous
to that of the extant Giraffa and the long-limbed
swamp fox
Cbrysocyon. However, the cylindrical arrangement of the manus reduced the surface contact and may have increased the distance from ground radiating heat as in the elephant (Loxodonta africana) from semiarid regions (F. Novas, pers. comm.). This reduced surface contact might imply some loss of stability. Track evidence
(Pittman and Gillette 1989)
for
neosauropods shows that
metacarpals I and V were somewhat movabie to accommodate irregular ground, but in titanosaurs, slight movement may have only been possible for metacarpal I as evidenced by the tight articulation of the manus in Argyrosaurus (Huene 1929).
The heavily furrowed distal end of the metacarpals in ti-
tanosaurs indicates the presence of a cushioning tissue. This material may not have been thick cartilage because of the limitations of nutrient defusion (Christiansen 1997 Bonnan 2003). Specimens of Antarctosaurus and cf. Ldplatasaurus have produced a material that was different from the encasing matrix. Its distribution resembles the calcified tissues in extant tetrapods (pers. obs.). Although the nature and properties of this substance are not known, its poor preservation defines it as non-ossified, and probably a soft tissue, which could have acted as a cushioning tissue. The stresses of locomotion would have caused some elastic deformation on the metacarpals. Because several works treated this aspect in detail (Alexander et. al. 1'979; Alexander 1985; Biewener Evolution of the Titanosaur Metacarpus
.
339
1990; Christiansen 1997), the peak stresses in the diaphysis of the will not be evaluated here. However, it is clear that the tubuIar arrangement of metacarpals in titanosaurs, connected only at their proximal and distal ends, has a major biomechanical implication. In many ways, the circular arrangement resembles Stonehenge (Fig. 15.3M) or the Sun Gate at Tiawanaku (Bolivia). The arrangement in titanosaurs allows the bones to support a larger mass and, most importantly, the sudden load of the body with each step. At that single moment, with the srress on the forelimb at its maximum, one-quarter of the total body weight suddenly pushes down through the humerus, radius-ulna, carpals (partially carrilaginous?), and metacarpals to the ground. The poorly ossified wrist would have distributed the mass of the body evenly through the metacarpals (Fig. 15.3L). Lacking digits, rhe mass would be transbones
rnitted directly through the basal cushioning pad and into the ground. This particular "stonehenge structure" of the manus is Iikely to have allowed titanosaur sauropods to reach the largest recorded size for terrestrial animals (Argentinasattrus, Bonaparte and Coria I993). \Thereas the large titanosaurs had long, robust metacarpals, the crown group, the Saltasaurinae, were smallbodied taxa that shortened their metacarpals. Contparatiue anatomy and behauior. Most sauropods lack an ossified olecranon process on the ulna (\il/ilson and Sereno 1998), although Bonnan (2003) suggested the presence of a cartilaginous one. This absence is probably related ro the columnar, graviportal limbs and allowed little motion at the elbow. The reacquisition of a relatively rvell-developed olecranon process characterizes some advanced titanosaurs (Powell 2003), and also characterizes cursorial and fossorial mammals that dig (e.g., armadiilos). Titanosaurs also have well-developed opisthocoel dorsal vertebrae, increased back mobility through the loss of the hyposphene-hypantrum articuiation, shortening of the forelimbs, and angled pelvis. These features allow the titanosaur back to have some degree of dorsoventrai flexure (Sfilson and Carrano 1,999) so that it could produce a mammalian-like curved back, as in armadillos. By assuming this position, the center of gravity is shifted posteriorly to free the forelimbs from most of the body weight and allowing them to be used in digging. Furthermore, the wide gauge of the hindlimbs improved stability, and the presence of osteoderms may have served as counterbalance (Powell 2003). Not surprisingln titanosaurs are the only sauropods known with hadrosaurid-like nesting colonies, with the eggs laid in excavated pits (Garrido et aI.2001). The adaptations given above differ from other sauropods and would have permitted them to dig their own nesrs in a manner similar to that of hadrosaurid dinosaurs. However, only a combined study of osteology, ichnology, and biomechanics will clarify aspecrs of the posture and movement capabilities in titanosaurs. In addition, it will shed insight into whether they excavated using only the metacarpals or whether they had the help of a first metacarpal clarv, which would be conveniently facing backward.
340 .
Sebastidn Apesteguia
Conclusions Although they were as graviportal as other sauropods, ritanosaurs developed special features in rheir limbs. The titanosaur carpus is similar to that seen in some basal titanosauriforms (e.g., Atla-
saurus\
but apparently not fully
homologous
to that
oI
diplodocoids (e.g., Apatosaurws). However, their long, homogeneous metacarpals were unlike any known graviportal tetrapod in being vertically arranged into a tubular structure. The trend that led to the lengthening of the manus and the loss of the digits were perhaps related to each other, and the whole process was probably much more complex than first appears. Those changes developed throughout the entire evolutionary history of the titanosauriforms and can be traced from the long, slender, and relatively heterogeneous metacarpals in Brachiosduruzs to the robust, homogeneous metacarpals in Late Cretaceous titanosaurs. This evolution is marked by enlargement of metacarpal V to be subequal to metacarpal I; the reduction and loss of digits and development of flat, distal, metacarpal trochlea; the reduction of proximal intermetacarpal contacts; the appearance of flanges on the distal portion of the metacarpals; and the bowing of metacarpal I in some taxa, possibly related to the retention of an asymmetrical, short first phalanx and ungual (lost in more derived taxa). The loss of digits re-
sulted
in a
columnar, eugraviportal forelimb
by adding the
metacarpus as a segment distally. Connection of the proximal and distal epiphyses allowed the shaft to have some freedom of motion, thereby reducing the peak stress in the bone diaphysis. The changes in the manus are associated with other changes in the skeleton, including reduction of forelimb length, the developrnent of an olecranon, arching of the back by the development of opisthocoelous vertebrae, loss of hyposphene-hypantrum articulations, enlargement of the sacrum processes, lateral expansion of the ilia, and the appearance of osteoderms. These features may be related to nestdigging by these sauropods. Acknowledgments. I thank Fernando E. Novas, who realized need the to better understand the forelimb in titanosaurs for function and taxonomy (e.g., Argyroslurus and Antarctosaurus), and for collecting the material from Portezuelo. To Jos6 F. Bonaparte, who prodded me by insisting that there was nothing to gain in the study of metacarpals because the major information was in the vertebral anatomy (I suspect he did it rvith such an intention!). To Leo Salgado for support and commenrs, especially about the angle metacarpus position in Camarasaurus. To him and Carlos Mufroz for allowing me to study the unpublished metacarpus housed in the MPCA. To Pablo Gallina for useful discussions. To Matthew Bonnan for review comments that improved the focus of the study. To Virginia Tidwell and Kenneth Carpenter for their editorial help. To Jorge A. Gonz6Iez and Gabriel Lio for their skillful drawings and to Eva L6pez for illustrations. To the Jurassic Foundation and PaleoGenesis for fieldtrip support. A cast of Epachthosaurus was made Evolution of the Titanosaur Metacarpus
.
341
available by the "Egidio Feruglio" Museum; a 1:1 model of Chubutisaurus was made by PaleoGenesis, and a 1:4 modeled metacarpus of the latter was kindly made available by Gabriel Lio. References Cited
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Salgado,
L.
1.993. Comments
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Salgado, L., R. A. Coria, and J. O. Calvo. 1997. Evolution of titanosaurid sauropods. I: Phylogenetic analvsis based on the postcranial evidence.
Ameghiniana 34:3-32. Sereno, P. C. 1993. The pectoral girdle and forelimb of the basal theropod Herrerasaun.rs ischigualastensis. Journal of Vertebrate Paleontology, 13(41: 425-450.
Sinclair, n7. J., and M. S. Farr. 1932. Aues of the Santa Cruz Beds. F.eports/Princeton University Expeditions ro Patagonia, 1 8 96-1 899, vol. 7, pt. 2. Princeton, N.J.: Princeton University Press. Thulborn, T. 1990. Dinosattr Tracks. Nerv York: Chapman and Hall.
Tidwell, V., K. Carpenter, and S. Mever. 2001. New Tiranosauriform (Sauropoda) from the Poison Strip Member of the Cedar Mountain Formation (Lower Cretaceous), Utah. In D. H. Tanke and K. Carpenteq eds., Mesozoic Vertebrate Life, 139-165. Bloomington: Indiana Universitv Press.
Upchurch, P. 1994. Manus claw function in sauropod dinosaurs. GA/A
I0:161-171. 1995. The evolutionar,v history of sauropod dinosaurs. Philosophical Trdnsactions of the Royal Society of London 349: 365-390. I 998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of the Linnean Society 124 43-fC3. V/ilson. J. A. 2002. Sauropod dinosaur phvlogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136:217-276. \)filson, J. A., and M. T. Carrano. 1,999. Titanosaurs and the origin of "wide-gauge" tracku'ays: A biomechanical and sysremaric perspecrive on sauropod locomotion. Paleobiology 25(2): 252-267. Sfilson, J. A., and P. C. Sereno. 1998. Early evolurion and higher-level phylogen,v of sauropod dinosaurs. Memoir 5. Journal of Vertebrate Paleontology 18 (supp. to no. 2): 1-68. !7ilson, J. A., and P. Upchurch. 2003. A revision of Titanosaurzs Lydekker (Dinosauria-Sauropoda), the first dinosaur genus with a "Gondwanan" distribution. lourndl of Sl,stematic Palaeontologl, 1(3): 125-160. Worthl', T. H., A. J. Anderson, and R. E. Molnar. 1999. Nlegafaunal expression in a land without mammals: Tl.re first fossil faunas from terrestrial deposits tn Fiji. Senckenber giana biologica 7 9 (2): 237-242.
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345
L6. Pes Anatomy in Sauropod
Dinosaurs: Implications for Functional Morphology, Evolution, and Phylogeny MerrHew F. BoNNAN
Abstract The anatomy and evolutionar,v history of the sauropod tarsus and pes remain largely unexamined despite their manageable size. Sauropod pedes possess several unique features: an asymmetrical pes, extreme reduction of the tarsus, large pedal claws, and expanded phalangeal articular surfaces. A review of tarsal and pedal anatomy in sauropods and their outgroups suggests that several characteristics of sauropod tarsi and pedes were acquired earlier than recent phylogenetic analyses suggest. These changes in pes morphology were not always directly correlated with graviportal
constraints. The pedes of most sauropods assumed a semiplantigrade configuration correlated rvith astragalus reorientation. This foot posture may have facilitated plantarflexion by changing the insertion angle through which plantarflexors acted on the pes and/or a plantar aponeurosis. Ossified distal tarsals have never been reported for any sauropod; they rnay have fused to the prorimal surfaces of the metatarsals or remained as small cartilaginous elements. The metatarsals may have articulated directiy with the astragalus and calcaneum in most sauropods. Proximally, eusauro-
346
pod metatarsals form a broad arch; those of neosauropods form a more linear arrangement; and, based on outgroup comparison, the medial portion of the anterior face of metatarsal V probably articulated posteriorly with metatarsal IV. Diplodocids have iow, lateral ridges on the anterior faces of metatarsals I-III. The broad articular surfaces, offset flexor tubercles, ventrolateral orientation of the pedal claws, and trackway evidence suggest flexion and rotation of the claws occurred during contact r,vith the substrate. Overall, tarsus and pes morphology remained conservative during sauropod evolution, with anterolateral orientation of the pes and increased phalangeal mobility the only significant trends arising after basal sauropods.
Introduction Among known terrestrial vertebrates, the success of sauropod dinosaurs as giants remains unparalleled both in terms of their evolutionary longevity and global distribution (Dodson 1990; Mclntosh et a|. 1997). An expansive fossil record and the broad geographic distributions of several neosauropod taxa (e.g., Apatosaurus, Diplodocus, Camarasaurus, Brachiosaurus\ suggest that many sauropods were significantly mobile animals for their size. However, despite its implications for paleoecology and paleobiology, sauropod locomotion remains poorly understood. The size, mass, and fragility of many sauropod appendicular elements have led, un-
derstandabln
to indirect evaluations of
sauropod locomotion.
Comparison of convergent limb characteristics with those of extant graviportal taxa (i.e., elephants) (e.g., Bakker 1971; Jensen 1988; Alexander 1989; McGowan 7991,), statistical analysis of limb elements (e.9., Coombs 1978; Foster 1995; Curtice et al. 1997;lWrlhite arrd Curtice 1.998; Carrano 1999; Bonnan 2004), and estimations of mass with scale models or bone cross-sections (Colbert 1962; Anderson et al. 1985; Alexander 1989; Paul 1997) are examples of several different approaches traditionally used to constrain sauropod locomotion. Surprisingiy, whereas the size of sauropod limbs present considerable challenges to understanding locomotion, the anaromy and functional morphology of sauropod feet are rarely considered in any evaluation of sauropod locomotion despite the manageable size of these elements. Moreover, because of well,known trackways (e.g., Farlow et aL. 1989; Farlow 1992; Santos et al. 1994; Lockley and Hunt 7995), the feet represent the only osteological compo-
nents of sauropod hindlimbs for which the living orientation is known. Furthermore, the most recent and comprehensive sauropod phylogenetic hypotheses utilize several foot-related synapomorphies (Upchurch 1998; Wilson and Sereno 1998; \Wilson 2002). 'Within this context, deciphering the anatomy of sauropod feet is significant both for inferring and constraining the limits of sauropod locomotion, and for evaluating proposed synapomorphies and their functional origins. Pes
Anatomv in Sauroood Dinosaurs
.
347
Fig. 16.1. Sauropod manus and pes dndtotlt\,. Proximdl (A, C) and
anterior (8, D) uieus of the manus (A, B) and pes (C, D)
of
saurop od s. (AJ Camarasaurus (KUVP 1297 1 5) artiulated manus; (B) stylized diagratn r,tf Camarasaurus mantrs; (C) and
(D/ Apatosaurus (CM
8c))
drticLrldted pes. Scale bars: 70 cm.
Abbreuiations: Lt = LTstragdlus; rottrnn nutnerols = digit idcntitl'. See Ligure 16.2 for illnstrations of sauropod cdlcanea.
The manus and pes of sauropods are both unique structures (Fig. 16.1). The manus of most known sauropods consists of a digitigrade colonnade of five metacarpals arranged in a semicircle, with short, reduced phalanges and, usually, a single pollex claw (Coombs 1975; Upchrrch 1994; lviclntosh et aI. 1.997). The evolution and functional morphology of the sauropod manus is considered in detail by Bonnan (2003). In contrast, the sauropod pes is a remarkably different structure: it is asymmetrical, has phalanges with well-developed articular surfaces, typicaily bears three large claws, retains only two ossified tarsals, was semi-plantigrade in posture, and possessed a large, cushioning plantar pad (Mclntosh et a|.7997; Bonnan 2001). This unusual morphology differs considerably from the pedes of other dinosaurs and graviportal vertebrates, posing numerous questions. \Whereas other graviportal vertebrates typically possess digitigrade or semi-digitigrade, symmetrical pedes, why was the pes semi-piantigrade and asymmetrical in sauropods? What possible functional roles did the apparently mobile pedal claws serve in such huge animals? In the apparent ab-
sence
or
significant reduction
of
ossified distal tarsals, did
sauropods actually possess a tarsometartarsal joint in which the proximal tarsals articulated directly with the metatarsals? The anatomy of the sauropod tarsus and pes is reviewed, and osteological data are presented, rvhich suggest that their unique shape and functional morphology resulted from the acquisition of a graviportal posture constrained by the inherited morphology of the
348
.
Matthew
F. Bonnan
saurischian hindlimb. Furthermore, osteological data and functional inferences presented here suggest several of the tarsal and
pedal synapomorphies, which have been assigned to eusauropods and neosauropods previousll', were present in the most basal sauropod taxa instead. Ultimately, sauropod tarsal and pedal anatomv and functional morphology suggest most of their unique shape was acquired early and rvas generalh' conserved throughout sauropod evolution. Institutional ab br euiations. AMNH-American Museum of Natural History, New York, Ner'v York; BYU-Brigham Young University, Provo, Utah; CEU-College of Eastern Utah, Price, Utah; CMCarnegie Museum of Natural Historl', Pittsburgh, Pennsylvania; DNM-Dinosaur National Monument, Jensen, Utah; FMNH-Field Museum of Natural History, Chicago, Illinois; HMNS-Houston Museum of Natural Science, Houston, Texas; KWP-Universitv of
Kansas Vertebrate Paleontology Museum, Lalvrence, Kansas; MNB-Museum firr Naturkunde, Berlin, Germany; M'$7C-Museum of Western Colorado, Fruita, Colorado; NMNH-National Museum of Natural History, 'Washington, D'C.; OMNH-Oklahoma Museum of Natural History, Norman, Oklahoma; SMNSStaatliches Museum fiir Naturkunde, Stuttgart, Germany; TAfETate Geological Museum, Casper, Wyoming; UC-University of Chicago, Chicago, Illinois; UMNH-Utah Museum of Natural History, Salt Lake Citv. Utah; YPM-Ya1e Peabody Museum, New Haven, Connecticut.
Materials and Methods Materidls and manipulation. The tarsus and pes of several neosauropods were examined at the seventeen collections listed above. Apatosaurus, Barosaurus africdnus, Diplodocus, and Camardsaurus comprise a majority of the observational and articular data presented here, because their postcrania are numerous in collections, their phylogenetic relationships are clear, and these taxa represent two major branches of the Neosauropoda: Apatosaurus, Barosaurus, Diplodoarc: Diplodocoidea (Upchurch 1998;'lfilson and Sereno 1998; Vilson 2002) and Macronaria (Camarasaurus ['Wilson and Sereno 1998]). The tarsi and/or pedes of additional taxa were examined to provide a broader functional perspective and to frame the functional hypotheses presented here in a phylogenetic framework (see below): Alligator, Herrerasauras (basal dinosaur/ theropod), Allosaurus (theropod), Columba liuia (bird), Plateosaurus (prosauropod), Barosaurus lentus (diplodocid), Drcrdeoslurus (diplodocoid), and Brachiosaurus brdncai (macronarian). Other sauropod tarsi and pedes described here (Antetonitrws, Vulcanodon, Orneisaurus, Opisthocoelicaudia) are based on their descriptions in the literature (Yates and Kitching 20031'Raath 1972; Cooper 1984; He et al. 1988; Borsuk-Bialynicka 1977). Finally, the tarsus and pes of the African elephant (Loxodonta africana) and the
Pes
Anatomv in Sauropod Dinosaurs
.
349
Indian elephant (Elephas maximus) were examined as well because these mammals have typically been used as analogs for sauropods (e.g., Bakker 1986; Paul 1987; Jensen 1988). Examination involved articulation (phvsical bone-to-bone con-
t-act) and manipulation of tarsal and pedal elements. For the pes, all
five metatarsals could be articulated and arranged by stabilizing each element in a sandbox (sometimes with sandbags), or by propping them up with clay. Once arranged, the astragalus and calcaneum (if presenr) were articulated with the proximal ends of the metatarsals to determine their orientation and relationship. In certain instances, the astragalus was articulated with the distal crus. Phalanges and unguals r,vere articulated with their appropriate metatarsals and manipulated bv hand to determine their ranges of motion. The astragalus and calcaneum of known sauropods are typically very rugose and pitted on most of their surfaces (Bonnan 2000,2001), which suggesrs that at least a thin layer of hyaline cartilage was present, which covered these bones almost entirely (see Bonnan I2003 | for furrher discussion on inrerprering sauiopod "epiphyses"). It is possible, as Christiansen (1997) suggests for sauropod limb elements, that fibrocartilaginous menisci were present on the distal articular surfaces of these bones. SurprisinglS although the proximal ends of the metatarsals are typically roughened, their distal ends, and the articular surfaces of the phalanges and unguals, are smooth and well preserved. V/hereas cartilage was certainly present between these joints, the smooth and well-formed articular surfaces of these bones allow a more precise estimation of their movements not tvpically possible with other sauropod long bones. Thus, despite the absence of hyaline cartilage morphology data, the inferred range of motion presented here for sauropod phalanges and unguals is more constrained than is typically possible for sauropod appendicular elements (see Bonnan [2003] for a more detailed consideration of sauropod joint cartilage in the foreIimb).
Constraining soft tissue inferences. The anatomical data and functional hypotheses were evaluated within the context of the three most recent and comprehensive sauropod systematic studies by Upchurch (1998), V/ilson and Sereno (1998), and Wilson (2002). In these phylogenies, Prosauropoda and Theropoda constitute consecutive monophyletic ourgroups, and were used to infer ancestral foot posture and orientation in the Sauropoda (Upchurch 1998; Wilson and Sereno 1998; \X/ilson2002\. Based on a number of cranial and postcranial characters, Sereno (I993,1999) has suggested that HerrerdsAurus is a primitive theropod. For simplicity, Herrerdsaurars will be treated as a model of an idealized earlv saurischian dinosaur here because of its completeness, early occurrence, and morphology. Although the monophyly of prosauropoda is debated (Galton 1990a; Benton 1997; Yan Heerden 1997; Sereno 1997, 7999; Yates 2003), it is generally recognized that prosauropods and sauropods are closely related. Therefore, prosauropod monophyly was assumed in the present study to sim350
.
Matthew F. Bonnan
comparisons. Bipedalism in basal dinosaurs, theropods, and prosauropods is strongly substantiated (Novas 1996; Sereno L993,1997, 1999; Sereno and Arcucci 7993,1994; Benton 7997), and this study follor.vs Upchurch (1998) and'$Tilson
plify outgroup
and Sereno (1998) in assuming quadrupedalism rvas acquired sec-
ondarily in sauropods. The success of inferring function from fossil vertebrates rs ultimately tied to the interpretation of bone morphology in light of known or probable soft tissue parameters. Functional inferences reported here follow the Extant Phylogenetic Bracket (EPB) approach (\il/itmer 1995) where possible, rooting soft tissue comparisons in an established, phylogenetic framework of extant outgroup taxa (e.g., crocodilians and aves [\Jfitmer 1995; Sereno 19991). Dissections of Alligator mississippiensis and Columba /lula specimens were performed to confirm the gross correlations between landmarks and soft tissues (see Bonnan 2001). Furthermore, dissection of the hindlimb and pes of a female African elephant (Loxodonta africana) was also performed to examine the musculature of a large terrestrial vertebrate and to search out convergent patterns owing to the constraints of graviportal locomotion' Detailed discussions of the musculoskeletai systems of these taxa are beyond the scope of the present study, and for more detailed considerations of their functional anatomy, see Reese (1915), Eales (1928), Sikes 11977), Mariappa (1986), Gatesy (7991,1997,1999), Proctor and Lynch
(1993), Shoshani (7996), Bonnan (2001), Ramsay and Henry (2001), and'lfilhite (2003). Occasional reference to the anatomy of L. africdna will be made throughout the tert. Unfortunately, the unusual morphology and limited number of identifiable landmarks in sauropod tarsi and pedes provide few opportunities for direct functional inferences (the Level I inference of \Titmer [1995h i.e., a 1:1 correlation between bony landmarks and soft tissues). Moreover, functional inferences drawn from EPB associations are at ieast two levels removed from the osteology (as per the inference pyramid [\Titmer 1'995]), and for simpiicity, gross muscle function is being inferred without a detailed consideration of other soft tissue parameters (e.g., cartilage, ligaments, etc'). As with all complex systems, however, simplifying the number of variables under consideration can be beneficial for inferring functional morphology provided that certain assumptions and limitations are acknowledged a priori and respected throughout the analysis' Therefore, this study makes the follor,ving functional assumptions. Firstln I assume that sauropod hindlimbs were loaded verticalln followed a parasagittal arc of movement during locomotion, and that long-axis rotation and abduction of the hindlimb was very restricted, based on simple biornechanical principles, the shapes of their articular surfaces, and comparisons with other graviportal vertebrates (see Bonnan [2001, 2003, 20041). Secondln homologs of the maior muscles responsible for effecting dorsiflexion, plantarflexion, inversion, and eversion of the pes in the outgroup taxa were assumed to be present in sauropods as well (e'g., M. gastroPes
Anatomy in Sauropod Dinosaurs
.
351
cnemius functioned ir-r sauropods to plantarflex the pes just as in outgroup taxa). Moreover, in the absence of data to the contrarl., it is assumed that n-ruscles affecting movements of the pes were inserted in regions sirnilar to those observed in extant outgroup taxa. Thirdll', the actions of most muscles on the pes are assumed to have been restricted mostly to extension or flexion, primitivel1,, in a parasagittal plane (e.g., in theropods and prosauropods). Therefore, modifications in the shape and orientation of the pes presurxably led to alterations of its primitively hinge-like function. Finally,, because the hindlimb bones were loaded vertically and restricted largely to a parasagittal plane of movement, and because the joint surfaces of the distal ends of the metatarsals and the phalanges are relatively well defined, missing data on joint cartilage morphology and other related soft tissues lviil not affect the generalized interpretations of the column- and hinge-like movements reported here (see Bonnan [2003] for a more detailed consideration of this issue in the sauropod forelimb and Bonnan [2004] for the forelimb and hindlimb). Thus, the functional inferences presented in the discussion are constrained by these four assumptions.
Osteology of the Tarsus and
Pes
Reuiew of tarsal and peddl osteology. The osteology of the tarsi and pedes of basal dinosaurs, theropods, and prosauropods are little removed from more basal ornithodirans in their basic form and inferred function. As is typical of other ornithodirans, saurischian
dinosaurs retain an advanced mesotarsal (AM) ankle, wherein a hinge-like joint is present between the astragalus and calcaneum proximally', and several smaller rarsals distally (Benton 1990, 1997). A peg on the medial edge of the calcaneum articulates with a socket on the lateral edge of rhe astragalus (see Fig. 16,2, Herrerdsdurus, Plateosdurus), and their combined distal articular surfaces form a smoorh, convex, roller-like surface (distal roller) against which the distal tarsals are articulated. ln Heruerdsaltrus, theropods, and prosauropods, the astragalus is incorporared into the crus via an ascending process that keys with the distal end of the tibia anteriorly (Benton 1990,7997; Novas 1989,7993; Currie 1997). The distal tarsals are usuall,v disc-shaped or flattened nubbins of bone atop the metararsals (Cooper 1981; Galton I990a; Molnar et a|. 1990; Novas 1989, 79931. The number of distal tarsals present never exceeds three elements in most saurischians: two are reported in articulation r,vith metatarsals III and ly rn Herrerdscturus (Novas 1993), most rheropods are reported to have had three (Molnar et al. 7990), and two or fewer distal tarsals are usually present in prosauropods (Cooper 1981; Galton 1990a). The pes is digitigrade and syrnmetrical, and digits II-IV form a functionally tridactyl arrangement (Benton 7990, 1997; Sereno 1999) (Figs. 16.3,16.4). Typically, unguals are retained on the first four digits. The articular ginglymi on the distal ends of the metatarsals, the articular surfaces of the phalanges, and the proxi-
352 . Matthew
F. Bonnan
Apatosaurus
/
',
A'l'(1
Diplodocus
/ \*- r lt.----"t *
Vulcanodon
,/ --y il.-t ./':\i v \
Camarasaurus
't--' (-/ ,' ' -',i-t )3
Opisthocoelicaudia /R
/
/\\
r^]
Macronaria Neosauropoda Eusaufopoda Sauropoda Sauropodomorpha Saurischia
mal surfaces of the unguals are usually smooth with deep, central articular grooves. A raised articular ridge on the proximal end of the successive phalanx articulates with the groove on the preceding phalanx or metatarsal. These smooth and grooved articular surfaces allow a considerable amount of digit flexion (pers. obs.: Herrerasdurus, Allosaurus, Plateosaurws), and such flexibility must have aided plantarflexion during the push-off at the termination of the support phase. This basic ornithodiran foot morphology probably allowed the pes to dorsiflex and plantarflex in a parasagittal plane, while simultaneously restricting its ability to evert' invert, 'li7ith some modification pronate, or supinate (Benton 1990,1.997). (e.g., fusion of the proximal and distal tarsals with the tibia and metatarsus, respectively), this functional suite of tarsal and pedal characteristics is paralleled in the feet of birds (see figures in George and Berger ft9661and Proctor and Lynch 11,9931). Sauropods. \With few exceptions' the basic anatomical morphology of the tarsus and pes are conserved in all sauropod taxa. The sauropod tarsus comprises but two ossified bones: a large, blocky astragalus and a small, globular calcaneum, the articular surfaces of which are highly rugose and pitted (Figs. 16.1)' Proximally, the astragalus is typically sub-triangular in outline, being widest laterally. Medially, the astragalus narrows to a blunted point that flattens proximodistally towards the medial apex. In contrast to other saurischians, the ascending process of the astragalus is directed weakly dorsally but strongly posteriorly, so that the apex of the ascending process terminates superior to the proximal articular surface, rather than anterior (Raath 1972; Coopet 1'984; Mclntosh
Fig. 16.2. Euolution of the sauropod tarsus. Basic sauroPod phylogenl' sh owing Proximal uie*'s of rePr e s entati u e sauriscbian and sauropod tdrsi. In each didgram, anterior is down and posterior is uP, the astragalus is left, and the calcaneum (uthen present) is rigbt. Phylogeny based on data from UPchurcb (191)8) and'Wilson dnd Sereno (1998); Iine dratuirtgs by author or modified from Nouas (1c)89, Herrerasaurus and Plateosaurus), Cooper (1981, Vulcanodon/, He et al. (1988, Omeisaurus/, B onnan (2000, Diplodocts and Camarasaurus), and B or suk' Bia\tnicka (1977, Opisthocoelica udia). Astr aga lws o/Diplodocus is tibed further anteriorly than in normal orientdtion. Astragalus of Apatosaurus is tberefore prouided for comparison.
1990; Upchurch 1998 [for Neosauropoda]; \Tilson and Sereno 7998 lfor Neosauropoda]; Bonnan 2001). Thus, the ascending process of the astragalus keys "beneath" the distal articular surface of the tibia and not anterior to it as in most saurischians. This articulation reorients the distal roller so that it faces much more anteriorly than in all other saurischians ('S7ilson and Sereno 1998). A Pes
Anatomy in Sauropod Dinosaurs
'
353
exg
u
lp
exg
A
Fig. 16.3. Saurischian pes dnatomy. /A) Herrerasaurrls pes in anterior uietu (modified front Nouas 1993); lBl Plateosaurus rCast: YPM 2- lt pes in anterior uiew. Abbrct'iations as per ligure 16,1 except: exg = extensor grooue; lp = Iigatnent pits; ng = nutrient grooue, See Figure 16.5 for illustrations of saurischian tdrst.
shallow, gently concave, raised ridge extends anteroposteriorly from the posterior base of the ascending process to th; posterior border of the asrragalus, dividing the proximal articulai surface into tibial and fibular facets. A series of large pits (2 cm; pers. obs.) and foramina are usually present on the medial facet near the anteroposterior ridge. Distally, a low but distinct ridge crosses the distal roller mediolaterally, and divrdes the roiler surface into a convex anterior portion and a steep posterior and dorsally angled porrion. The angle of the posterior portion of the astragalus varies, but it can be greater than 30" to rhe ventrai surface of the distal roller (Bonnan 2001). $7hen viewed from the lateral side in articulation with the tibia, the distal articular surface of the astraqarus forms a convex arc which extends from the anterior porrion of the tibia to approximately just past its center. Thereafter, the distal articular surface cants approximately 30o posterodorsally and becomes a relatively flattened surface that extends to the termination of the astragalus posteriorly. \il/ilson and Sereno (1998, 49) suggest that the ascending process of the astragalus in vulcantdon. omeisaurus, and Mamei-
chisaurus
did not extend to the posterior border as in
neo-
sauropods. However, this definition is based on viewins the astragalus from a particular angle, and Wilson and Sereno-[99g.49) note rhat rhe ascending process of the astragalus in vulcanodon appears to extend to rhe posterior border because it is tipped port.iiorly in available figures. Although the ascending proi.r, of -o.. basal sauropods does not extend as far posteriorly as in the astragali of neosauropods (compare Cooper [1984, fig. ZSI with Wilson and Sereno 11998, fig. 331; or see Fig. 16.2),there is a distinct dif-
354 . Matthew
F. Bonnan
nFn
fl--LI-' 'ft
\t,,1
lll ii tV
{]ta
./^----ffi\ ) | //--z:^: V---'r
qth
c-a\:7l)
,€J-?ou Opisthocoelicaudia
2
ODta. Neosauropoda Eusauropoda
ference between the morphology of the ascending process of a basal sauropod such as Vulcanodoa (Raath L972, fig.9; Cooper 1984, figs. 23-25) and that of prosauropods (Cooper 1981; Galton 1990a; and see Fig. L6.2). Furthermore, the figured articulation of the astragalus with the crus in Vulcanodon (Cooper 7984, figs. 23, 24) suggests it assumed an orientation nearly identical to that observed in eusauropods.
The caicaneum is a small, fist-sized bone that articulated with the lateral edge of the distal fibuia and occupied the space between the fibula and pes (Mclntosh 1990; Bonnan 2000). The proximal surface of the calcaneum usually retains a smooth fibular facet, whereas the distal articular surface is a pitted, convex surface with a mediolateral ridge similar to that observed in the astragalus (Bonnan 2000). Several sauropod genera have been reported with ossified calcanea, including dipiodocids (Vulcanodon, Bdrapds
altr!'t
s,
Sh un o s awr u
s,
N eu qu ens aurw s, Euh
Fig. 15.4. Euolution of the B asic saurop od p hylo geny sh ouing proximal and anterior uiews of repre s entdtiL,e sauris ch ian and saur op od metatdrsi. P hylogenY based on data from UPchurch (1998) and.Wilson and Sereno ('1998): line draruings by author
saur op od metatar sus.
or modifed from Nouas (1993, Herrerasaurus/, Coop er 11 9 8 4, Vulcanodon), He et al. (1988, Omeisaurus), Jensen (1988, dnteior uiew of Camarasaurus), and B orsuk-B ialynicka ( 1 977, Opisthocoelicaudia/.
D ip I o d o cu s, Cam ar d s Auru s, B r a ch i o s duru s, s, M am e n ch i s auru s, and Ant ar ct o s duru s
el op u
[although the latter is questionable]) (Mclntosh 1990; Bonnan 2000). The caicaneum of Vulcanodon is similar to the calcanea of prosauropods, except for a unique, dorsally extending process that arises from the posterior border of the fibular facet (Cooper 1984). The proximal articular surface of the calcaneum is usually pentagonal in outline, and a smooth facet that is shallowly conver and canted gently ventromedially occupies most of the surface (Bonnan 2000). The medial edge of the calcaneum is rugose, pitted, and flattened, and it is articuiated with the lateral edge of the astragalus. As with the astragalus, a low but distinct mediolateral ridge crosses the middle of the distal articular surface, dividing the anterior half into a convex, roller-like surface and the posterior half into a steep surface that cants approximately 30' to 45o dorsoventrally (Bonnan 2000). Bonnan (2000) found that proper articulation and alignment of the calcaneum can be achieved by aligning the mediolateral ridge of the calcaneum with that of the astragalus' In natural articulation, the convex anterior half of the distal articular surface Pes
Anatomv in Sauropod Dinosaurs
.
355
appears to have been oriented more ventrally than that observed
for the astragalus. Ossified distal tarsals are unknown and unreported for any sauropod dinosaur (Mclntosh et al. 1997; Wilson and Sereno 1998), including early saurop ods (Antetonitrus, Vulcanodon, Barapasaurus) and derived titanosaurid sauropods (opistb ocoericaudia, Saltasaurus) (Bonnan 2000; Yates and Kitching 2003). The reduction in the number of distal tarsals from three in theropods to two or fewer in prosauropods suggests the role of distal tarsals in locomotion was de-emphasized in sauropods. If the lack of ossified distai tarsals in sauropod pedes reflects a biological process instead of taphonomy, it is possible that the distal tarsals were fused onto the metatarsals or proximal tarsals, eliminated completely, or retained as small, unossified elements. Assuming the absence of ossified distal tarsals indeed signals their actual functional absence from the pes; a direct articulation between the metatarsals and the astragalus/calcaneum would represent a derived, non-infratarsal mesotarsal joint (see beiow). In all sauropods, the pes is distinctly asymmetrical, but this is mostly due to differences in the length and orientations of the phaIanges. Surprisingly, when viewing sauropod metatarsals to the exclusion of the phalanges, a subdued but similar gross configurarion with other saurischian pedes is observed: metararsals II-IV are the longest elements, whereas metatarsals I and V are shorter and subequal in length (Fig.16.4). The major difference lies in the robustness of the metatarsals, which usually grade from the very short and robust metatarsal I to the relatively thin and gracile metatarsal IV. Metatarsal V is shorter than metatarsal IV, but is qualitatively more robust than meratarsal IV proximally (Bonnan 2001). Metatarsal V is also distinctly larger than in prosauropods, and is usually paddleshaped: its proximal end is greatly expanded, and its distal end narrows to a "handle," even in basal sauropods such as Antetonitrus (Yates and Kitching 2003). The sub-oval, triangular, and quadrilateral shapes of the proximal ends of the metatarsals create a sentle arch when articulated in basal (e.g., Vulcanodonl and. eura.,tpod (e.g., Omeisaurus) taxa. In contrast, the more rectangular, proximal, articular surfaces observed in neosauropod taxa ..."t. u r.'or. linear configuration in articulation (e.g., Apatosaurus, CAmarlsAurus, Opisthocoelicaudia). In all sauropods examined, the proximal articular surfaces of metatarsals I-III are rugose, pitted, and have gently convex articular surfaces both anteroposteriorly and mediolaterally, presenting weakly spherical surfaces to the astragalus. Metatarsal I typically has a strongly mediolaterally concavoconvex articular surface that, when articulated with the medial apex of the astragalus, canrs its shaft medially. The proximal,lateral faces of metatarsals I and II contain deeo triangular notches thar allow merararsals I-III ro arriculate tighrly at their proximal ends, forming a "bridge-like" structure. As the distal roller of the astragalus faces anteroventrally, articulation of the first three metatarsals with the distal roller clearly demonstrates
356 . Matthew
F. Bonnan
that the pes was not digitigrade but instead semi-plantigrade in neutral orientation ('Wrlson and Sereno 1998). Metatarsals IV and V articulated loosely with the calcaneum, the metatarsal "bridge," and with one another. Their proximal articular surfaces are much less developed than those of metararsals I-III, and the,v are relatively flattened or only shallowly convex mediolaterally. The triangular proximal articular surface of metatarsal IV articulates medially with metatarsal III, but articulates anterior to metatarsal V. A common error observed in articulated sauropod pedes is to place metatarsal V directly lateral to metatarsal IV, such that it hangs in space past the lateral edge of the distal fibula (e.g., most skeletal mounts in the United States). Based on known sauropod pes prints (Langston 1974; Farlow et al. 1989; Gallup 7989; Farlow 1992; Santos et al. 1994; Lockley and Hunt 1995), these two meratarsals appear to have been fully embedded within a heavy pad. The anterior faces of the metatarsals are relatively smooth, al-
though a low ridge on the distal lateral edge of the first three metatarsals is present in the diplodocids Apatoslnrus, Diplodocus, Barosaurus lentus, and B. africdnus (Upchurch 1995; pers. obs.).
The ridges arise near the center of the shaft and extend venrrolaterally to their termination a few millimeters above the distal articular surface. Metatarsal II has the strongest) most developed ridge, and this ridge is especially prominent in specimens of Apdtctsaurus. These ridges have not been observed or reported in other nondiplodocid sauropod taxa, although Yates (pers. comm.) has observed a dorsal scar on metatarsal llI of Antetonitrus. Furthermore, metatarsal I in ail knou,'n diplodocids has a laterally directed tab or process arising from the posterior distal articular surface that has been recognized by previous researchers (Mclntosh 1990; tJpchurch 199 5 , 1998; Wilson and Sereno 199E t . In the basal sauropod taxa Antetonitrus and Vulcanodon, metatarsals I-III have distinct ligament pits on their distal ends (Raath I972;Cooper 7984; Yates, pers. comm.), and the proximal phalanges of digits I-III in Vulcanodon retain the smoorh, cup-like articular surfaces and the symmetrical, divided ginglymi typical of prosauropods (Raath 1972; Cooper 7984).In contrasr, known eusauropods lack ligament pits and symmetrical, distinctly divided ginglymi. Instead, the ginglymi of the first three metatarsals are asymmetrical and beveled medially, such that the medioventral angulation of phalanges I-1, il-1, and III-1 results from their articulation with their respective metatarsals. The ginglymi of metatarsals I-III are relatively smooth and wide, have deep fleror grooves that wrap posteriorlS and have surfaces extending medially onro the anterior faces of the metatarsals to form asymmetrical articular "lips." This articular morphology allows one to slide the prorirnal phalanges dorsomedially and venrrolaterallv when articulated. The flexor grooves appear to be deep enough to have constrained lateral and medial deviations of flexor rendons, and they may have maintained the proper angle of their insertion on rhe phalanges and unguals (see below). Pes
Anatomv in Sauropod Dinosaurs
.
357
The phalangeal formula for most sauropods is apparently 2-34-2(3?)-1. The phalanges of digits IV and Y inVulcanodonwere not recovered, but the formula of digits I*III is 2-3-4 (Cooper 7984). Two phalanges and unguals were recovered for Antetonitrus (Yates and Kitching 2003). The phalanges of most sauropods are compressed longitudinally, are usually broader than long, and, for digits I-III, asymmetrically oriented such that their ginglymi are directed anterolaterally lMclntosh 19901 Wilson and Sereno 1998). The phalanges of digits I-III are wedge-shaped when viewed dorsally and compressed mediolaterally so that the medial portions of the phalanges are relatively undistorted, whereas the lateral portions in many cases are reduced to a thin flange (Upchurch 1998; Bonnan 2001). In digits II and III, the phalanx that articulates with the claw can be very small and button-like. Ungual I in Antetonltrzzs is somewhat asymmetrical but not very recurved (Yates and Kitching 2003), whereas this ungual is recurved in Vulcanodon (Cooper 1984; \Wilson and Sereno 1998). All eusauropod unguals are recurved, somewhat sickle-shaped (Wilson and Sereno 1998), and curved laterally, with relatively smooth, convex medial surfaces and concave lateral surfaces (Langston 1974;Farlow et al. 1989). The proximal articular surfaces of the claws are beveled such that their articulation with the terminal phalanges orients them laterally. The proximal, ventral surface of the claws possess what appear to be flexor tubercles, but these are much weaker than those usually observed in theropods or prosauropods (pers. obs.). Distinct nutrient grooves can be observed on sauropod claws, and the tips of the claws are usually dull. The sharpness of the living ungual sheaths is difficult to ascertain, although in pes tracks where claw prints are preserved (e.g., Farlow et al. 1989; Santos et aL. 1994) the distal ends of the claws appear to terminate in dull points.
Sauropod Pes tackway Features and Functional Implications The following description is based on the Brontopodus birdi tracks at AMNH and at Glenrose, Texas, and the published descriptions of sauropod pes tracks by Fariow et al. (1,989), Pittman (1989),
Pittman and Gillette (1989), Lockley (1987, 1997\, Santos et al. (1,994), and Lockley and Hunt (1,995). Following the medial border of the print anteroposteriorly, digits I-III are visible as separate, laterally directed claw prints that are deeply impressed (Fig. 16.5A). Digit I is always the most deeply impressed, followed by digit II and digit III laterally. Continuing posteriorly along the medial border of the pes print, the imprint of the metatarsus (and tarsus?) is oval in shape and forms a gently convex region that is the shallowest region of the footprint. A small but distinct notch or emargination is present at the posterior termination of the metatarsus region, which may demarcate the beginning of the plantar pad. Just posterior to the emargination, the depth of the print increases dramatically. The depth of the plantar pad imprint remains relatively con-
358 . Matthew
F. Bonnan
A
6\
'ri I
ill IV
\,
B
il
\r {r\
ill
e -lv \
Fig. 16.5. Orientation of the pes in sauropod tracku,ays. (A) Brontopodus btrdi showing lateral
/s\ \e \
outuard turn of the pes from tbe lratkwal': and tB' Earl)' .lurtssit tr a c kw a.t s fr otn P o rtu gal, showing a more anteriorly oriented pes. A modified from Farlou et al. (1989); B modified from Santos et dl. (1991). Abbreuiations: m = manus; p =
V
Pes.
stant, becoming slightly shaliower as the print terminates posteriorly. These observations strongly suggest that the pad and the anterior, medial side of the foot absorbed and distributed most of the weight transferred through the hindlimb. The pes is oriented strongly anterolaterally in many trackways, such that digit I lies anterior (e.g., Farlow et aI. 1989; Pittman 1989; Pittman and Gillette 1989 Lockley 1991; Farlow 1992). A Middle Jurassic sauropod track site described by Santos et al. (1994) has imprints of pedes that are oriented more anteriorly (Fig. Pes
Anatomy in Sauropod Dinosaurs
.
359
16.58). Since many of the known sauropod trackways are Late Jurassic and Early Cretaceous in age, perhaps the lateral, outward
turn of the pes occurred in the neosauropod forms, with more primitive eusauropods retaining a pes orientation closer to those of other saurischian dinosaurs. The claw prints in many sauropod pes tracks make distinct and separate markings.'With the pes oriented anterolaterally', the first claw print is usually anterior and slightly lateral, and is somewhat separate from the other claw prints (e.g., Pittman and Gillette 1989; Farlow et al. 1989). This would be predicted from the osteology described above and the functional morphology described below, where metatarsal I can apparently abduct to some extent from the other digits. Claws II and III are oriented such that, with the pes directed anterolaterally, they are turned ei-
ther directly laterally or almost posterolaterally (Pittman 1989; Pittman and Gillette 1,989). The medial faces of claws I,II, and III are impressed ventrally into the substrate. Occasionalll', a small, button-like impression of the distal end of digit IV is also present' and in a few trackways a small, distinct claw mark is present (Farlor,v et al. 1989: Farlow 7992).In the Middle Jurassic sauropod tracks reported by Santos et al. (1994), claw I faces anteromedially, claw II faces slightly anterolateralln and prints of claws III and I\/ face anterolaterally. Furthermore, the claw impressions in these Middle Jurassic tracks appear to be mostly imprints of the ventral surfaces of the clarvs, rather than those of the medial faces. Langston (1974), Galiup (1.989), and Farlow et al. (1989) had interpreted many of the Early Cretaceous trackways as belonging to a brachiosaurid sauropod. In contrast, \Tilson and Carrano (1999) have recently challenged this interpretation of the B. birdt and other "wide gauge" tracks. Instead, they note the wider stance presumably adopted by titanosaurid sauropods, and suggest that sauropods such as Alamosaurus or Opisthocoelicaudia are more
appropriate models of "wide-gauge" track-makers (Wilson and Carrano 1999). Regardless of which sauropod made the Brontopodus birdi tracks, the features described for these tracks are similar to those of Late Jurassic age in other parts of North America (Lockley 7987, L991). Although many Late Jurassic sauropod tracksites (Lockley 1.987, 1991.) typically do not have well-defined claw impressions, sauropod genera examined in the present study have laterally directed and mobile pedal claws that rotate their medial faces ventrally when flexed (see below). The strong anterolateral rotation of known neosauropod pes prints indicates a functional change from the more anteriorly directed pedes of earlier eusauropods. This change in orientation may be tied into the semiplantigrade nature of the pes and the functional, historical constraints of the saurischian pes (see below).
Functional Morphology Tarsus reorientation dnd metatarsus functional euolution. The reorientation of the distal roller of the astragalus in sauropods ori-
360 . Mattherv F. Bonnan
ents the digits such that they assume a semi-plantigrade posture, an
arrangement that wouid have loaded rhe metatarsals ar an angle of
45'. The term "semi-digitigrade" (\Tilson and Sereno 1998) has also been used to describe this posture in sauropod pedes. However, because the metatarsals as r,vell as the phaapproximately
langes appear to have plaled a significanr role in supporr and propulsion in sauropods, the term "semi-plantigrade" is used here.
The foreshortened meratarsus and large plantar pad (as observed in trackrvays) of sauropods are features that ma,v have alleviated the tensile stress that was presumablv produced by the semiplantigrade orientation of the pes. Metatarsals I-III in sauropods are the mosr robusr elements in the pes, and, after the plantar pad, make the deepesr impressions in sauropod pedal footprints (e.g., Farlow et al. 1989; pers. obs.). This suggests that they absorbed
a large proporrion of the body weight during locomotion, Metatarsals I and II in eusauropods are very robust, short, and wide mediolaterally and anteroposteriorly, and the overall morphology of metatarsal I is almost cube-like in anterior vierv. Such morphology is ideal for resisting buckling (Vogel 1988; McGo.,van 1999). The developmenr of an elastic plantar pad probably acted to alleviate the weight transmitted through the pes, as well as to support the pes posteriorly and unite the metatarsals into a cohesive functional unit as in elephants (pers. obs.). In mosr pes prints, the plantar pad is sub-triangular in shape and is clearly differentiated from the metatarsus portion (Farlow et al. 1989; Pittman 1989; Santos et a\. 1994; Lockley and Hunt I995). The very deep impression of the plantar pad compared to the rest of the pes imprint suggests that the pes functioned as though it were plantigrade. Perhaps the plantar pad functioned as a heel by conracting the substrate first and/or absorbing the shock of the decelerating hindlimb. Observations of the flexibility and resilience of elephant plantar pads suggest the sauropod plantar pad had a similar elasticity (McGowan 7991) and could absorb a great deal of compressive and tensile stress. As in elephants (Ramsay and Henry 2001), the pliability of the plantar pad probably made the sauropod pes a more flexible and supple structure than might be predicted from its osteology alone.
Although the semi-plantigrade condition of the pes in sauropods has been recognized as an early developmental feature oI the sauropod lineage (Upchurch 1998; Wilson and Sereno 1998 [Eusauropoda]), its functional significance has never been addressed. Even u'ith large piantar pads, elephants still retain vertically oriented metatarsals (Shoshanr 7996; Ramsay and Henry 2001). Cooper (1984) suggested that the pes of Vulcanodon assumed a semi-plantigrade configuration as a consequence of graviportal constraints: in essence, the pes assumed a posture most efficient at disrributing weight. It is tempting to view the reorientation of the sauropod metatarsus in terms of graviportal constraints only. Undoubtedll', the semi-plantigrade arrangement of the metatarsals and phalanges allowed the pes to distribute tensile and Pes
Anatomy in Sauropod Dinosaurs
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Fig. 16.5. Diagram of stylized postural changes in sauroPod hindlimbs and their inferred effect on M. gdstrocnemius function. (A) Typ ical s aur i s ch ian h ind lim b showing digitigrade Pes and eleuated metatdrsus with inferred M. gastrocnemius angle of ins ertion. (B ) H yp oth etical sdurop o d h indlimb r etainin g primitiuely digitigrade pes and el e u ate d metatdr sus tu itb inf err e d changes to M. gdstrocfiemius angle of insertion. (C) TyPical sarrropod hindlimb showing semiplantigrade pes and subhorizontal metatarsus with inferred changes to M. gdstrocnemius angle of insertion. Note that in B, the inferred angle of M. gastrocnemius insertion is signifi cantly re du ce d comP ar e d with A c;r C. The semi-Plantigrade postule of sauroPod Pedes may therefore haue arisen, in Part, to rL'tain an appropriale insertiott angle for M. gastrocnemiws and other plantdrflexors.
lcompressive stresses, but this might have been a secondary consequence of other competing functional needs. If the pes of Vulcanodon was semi-plantigrade, this feature occurred prior to the achievement of very large size in sauropods. Therefore, the evolution of this pes morphology may not have been driven by rveightbearing selection factors alone. The reorientation of the pes may have resulted, in part, as a
"solution" to the problem of plantarflexion within the historical constraints of the saurischian pes and tarsus. In becoming graviportal, the hindlimbs of sauropods became columnar in orientation, and the metatarsus and phalanges became very short (Upchurch 1998; Wilson and Sereno 1998).If the pes had remained digitigrade with a vertical metatarsus as in other saurischians, the tendons of M. gastrocnemius and other plantarflexors would have inserted into the pes (or a plantar aponeurosis) in parallel with their origins, an arrangement that would compromise their mechanical advantage (Fig. 16.6). Elephants overcome this potential loss of function through the retention of a lever-like calcaneal tuber into which the major plantarflexors of the pes insert (Eales 1928; Mariappa1.986; Shoshani L996;pers. obs.), although pedal movement is still relatively restricted. Steindler (1935, as cited in Schaeffer 1941) noted that at angles of insertion lower than 30', the plantarflexors have a more stabilizing than rotary effect on the pes during locomotion in various lepidosaurs and archosaurs. Based on these observations, the digitigrade pes and elevated metatarsus of basal dinosaurs, theropods, prosauropods, and birds probably served to increase the insertion angle of the plantarflexors (see Fig. 16.6). An increased angle of plantarflexor insertion would, in turn, increase the propulsive con-
362 . Matthew
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tribution of the pes in locomotion. By comparison with the primitive saurischian condition, reorienting the pes into a semiplantigrade orientation in sauropod dinosaurs probably caused the tendons of various plantarflexors to wrap around the smooth and angled posterior portion of the astragalus before inserting into its plantar surface (and plantar aponeurosis?). This redirection, in turn, would act to increase the plantarflexor angle of insertion and hence increase the propulsive contribution of the pes to locomotion (see Fig. 16.6). Observation of the muscle-plantar pad interface in elephants shows that there are no muscular insertions into the plantar pad, and it is assumed that pedal musculature was similarly constrained in sauropods Articulation and function of the metatarsdls at the ankle. As noted previously, no ossified distai tarsals are known for any sauropod, suggesting that metatarsals I-III articulated directly with the distal roller of the astragalus. If the sauropod ankle formed a noninfratarsal metatarsorarsal joint, the morphology of the metatarsals suggests that a significant degree of movement was possible at the ankle in sauropods. The following observations are based largely on the pedes of Apatosaurus, Diplodocus, and Camarasaurus. The proximal articular surfaces of meratarsals I-III articulate simultaneously with the distal roller of the astragalus when their distal ends splay apart from one another by approximately 10-20 (Fig.16.7).If the metatarsals are held rigidly together with both the proximal anc distal ends in mutual conract, either metatarsal I or metatarsal III does not articulate with the distal roller of the astragalus. Furthermore, the proximal articular surfaces of metatarsals I and II, and metatarsals II and III, articulate with one another such that slight mediolateral flexion can occur between them. The proximal articular surface of meratarsal II slopes gently medially. A deep, triangular notch on the proximal, lateral side of metatarsal I forms a convex lip that allows metatarsal I to articulate a few centimeters above the proximal articular surface of metatarsal II. Because the articulation between these metatarsals is convex on convex, this allows metatarsal I to roll dorsomedially in flexion against metatarsal II. The lateral edge of the proximal articular surface of metatarsal II articulates with a triangular notch on the medial face ofmetatarsal III. The notch is smooth and concave along the medial border of the proximal articular surface of metatarsal III. Although it does not articulate above metatarsal II, the concave, medial notch of metatarsal III articulates against the convex lateral border of the proximal articular surface in metatarsal II, producing the slight dorsolateral flexion of metatarsal III. The mediolateral concavoconvex proximal articular surface of metatarsal I allows it to articulate with the medial apex of the astragalus when flexed dorsomedially against metatarsal II. The concave proximal portion of metatarsal I articulates snugly against rhe medial apex of the astragalus while the lateral convex portion remains in contact with, and rolls against, the distal roller. Together, the proximal articular surfaces of metatarsals I-III can roll and Pes
Anatomy in Sauropod Dinosaurs
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Fig. 1 6.7. The metdtdrsdl " bridge" in sauropods. (A) Metatorsals I-lll in articulation u,ith the dstragalus lz Apatosaurus excelsus (CM 89); note how metatarsal I does not drticLtldte uith the distal roller of tbe asnagalus. (B) Met(tarsdls I-III splal,ed in order to articulate a,ith tbe distal roller of the astragalus. Metatarsal II drtd lhe dstragalus in la!crol uiett tuith metdtdlsal II in inferred (C)
maxinutm dorsiflexion and rnax im trm
p
lartt arfl
ex
i
1D1
on.
slide slightly medially and laterally against the distal roller, allorving a limited form of inversion and eversion, respectively. This motion is small, perhaps allowing the pes to shift 5' medially or lateralln and was probably further constrained by soft tissues. In articulation with the distal roller, the combined proximal articular surfaces of metatarsals I-III are capable of rocking dorsoventralln a motion that can be equated roughly to dorsiflexion and plantarflexion. The ventral extent of this rocking motion (or marimum plantarflexion) is constrained in part by the mediolateral ridge of the astragalus. As the metatarsal "bridge" rolls ventrally, the posterior edges of the proximal ends of metatarsals I-III articulate against the mediolateral ridge. Since the posterior half of the distal roller angles sharply dorsally, the metatarsal "bridge" cannot roll
further ventrally u'ithout disarticulating. The mediolateral ridge may also demarcate the anterior extent of the plantar pad. Ligaments, tendons, the plantar pad, and any plantar aponeuroses may have limited dorsiflexion and plantarflexion of the pes. As described previously, metatarsal IV articulates with metatarsal V such that the former is superimposed over the anteromedial portion of the latter, suggesting that both bones functioned as a single unit during locomotion. The combined proximal articu364 . Matthew
F. Bonnan
lar surfaces of metatarsals IV and V articulate against the distal roller-like surface of the calcaneum, allowing them to plantarfler and dorsiflex with the rest of the pes. Their relatively flat surfaces (see above) would have fr,rrther limited the inversion or eversion of the pes described previousl,v, but they may have been capable of sliding slightly across the distal roller of the calcaneum. The relatively large size of metatarsal V and its paddle-like shape is an unusual development among dinosaurs. Other large graviportai dinosaurs reduced or eliminated metatarsal V, supporting most of their rveight on three central digits (Dodson and Currie 1990, neoceratopsians; Galton 1990b, thyreophorans). The retention of a rather large metatarsal V, and its strong connection to the metatarsus, indicates that the proximal base may have acted as an insertion shelf for pedal evertors and plantarflexors in sauropods (see below).
Although not recovered or reported for a1l known sauropod taxa, functional and phylogenetic precedents support the presence of an ossified calcaneum in all sauropod taxa (Bonnan 2000). Functionaily, an ossified calcaneum wouid form a stable and reiatively incompressible space between the fibula and metatarsals IV and V. If a large block of cartilaginous tissue occupied the region between the fibula and metatarsus, it may have been easily damaged or ruptured (Bonnan 2000) because thick sections of cartilage do not distribute compressionai forces rvell (Currey 1984). Phylogenetically. an ossified calcaneum is known for many sauropod taxa in all higher sauropod clades (Sauropoda, Eusauropoda, Neosauropoda) (Bonnan 2000). Thus, disregarding functional considerations, the presence of an ossified calcaneum in most sauropods was probably tied as much to historical constraints as to functional limitations (Bonnan 2000). Locomotor implicdtions of sauropod pes orientdtion. The anterolateral orientation of the pes in neosauropods and perhaps some eusauropods may have conferred several functional advantages. The retention of sizable clalvs on at least the first three digits in most sauropod pedes suggests the outturning of the pes may have allowed the claws to act as traction devices, preventing the backward slip of the foot during support and propulsion. Moreover, an eramination of the phalanges in several neosauropods (Apatosaurtts, Diplodocus, and Cdmdrasauras) reveals the potential for significant claw flexion and rotation. The distal articular ginglymi of metatarsals I-III in examined neosauropods are directed laterally. Furthermore, the proximal phalanges that articulate with the distal articular ginglymi of the metatarsals are beveled mediolaterallg increasing the overali laterai orientation of the distal phalanges and the claws. The wide and smooth proximal articular surfaces of the proximal phalanges affords them a loose articulation with the metatarsals that allows them to extend and flex, as
well as to slide medially and laterally to a slight degree. In metatarsals I-III, the uneven, medial expansion of the distal articular ginglymi onto their anterior faces allows phalanges I-1, il-1, and Pes
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III-1 to extend dorsomedially. The loose articulations of the proximal phalanges with meratarsals I-III allow them ro rotare gently medially as they are flexed. Phalanx I-1 narrows ventrally such that both its proximal and distal articular surfaces pinch together, forming a ventrally projecting lip. This extends the scope of the distal articular surface of phalanx I-1, and would have increased the amount of flexion available ro claw I. The loose articulation of claw I with phalanx I-1 allows it to rotate laterally so thar at the end of maximum flexion. its smooth. medial face is oriented anteroventrally. Similar ranges of articulation and rotation are observed in digits II and III; see Bonnan (2001) for a more detailed analysis of these movements in Apatosaurus, Diplodocus, and Camarasaurus.
The amount of flexion, mediolateral sliding, and rotation of the phalanges in the pedes of sauropods is remarkable given their size, but was such a motion possible in the living pes? On each of the claws, a small flexor tubercle is present into which short plantar flexors (..g., M. flexor digitorum communis brevis, etc.) presumably were inserted. The flexor tubercles are asymmetrical, and are present medially on the proximal ends of the claws. This morphology suggests that if such flerors pulled on the medral sides of the proximal articular surfaces of the claws, they would induce a lateral rotation that would cause the claws to orient their medial faces ventrally during flexion (Fig. 16.8). Finally, deep flexor grooves occur on the posterior faces of the distal ends of metatarsals I-III. These grooves are directed anterolaterally, as are the articular gingIymi. The grooves appear deep enough to have limited the lateral and medial deviations of the short flexor tendons, and lvould have maintained the proper angle of the brevis flexors on the phalanges and unguals. If metatarsals I-III and their phalanges are articulated and viewed ventrally, a line of flexor travel can be drawn from the base of each metatarsal through the flexor groove to the claw, demonstrating how the brevis flexors could have inserted on the medial sides of the claws (Fig. 16.8). Metatarsals IV and V have relatively reduced articular surfaces and small phalanges. Typically, metatarsal IV retains two phalanges, but may retain a very small claw in some forms. The reduced articular ginglymus of metatarsal IV and the reduced articular surfaces of phalanges IV,1 and IV-2 suggest very little movement was possible in this digit. The distal articular ginglymus of metatarsal V is so reduced that there is almost no mobility between it and the small, nubbin-iike phalanr V1 that is sometimes present. Gallup (1,989) suggests that the apparently large range
of mo-
tion in sauropod claws served scratch-digging and, specificall5
nest-building habits. He based this suggestion largely on gross similarities in the arrangement of rhe forelimbs of aardvarks and armadillos, digging animals that have foreshortened forelimb elements and large claws (Hildebrand 1995). Although a somewhat similar morphology is observed in sauropod pedes (foreshortened metatarsus and phalanges, large claws), the claws do not appear to
366 . Matthew
F. Bonnan
A
Fig. 16.8. Effect of medially displaced flexor tubercles on sawropod claws. (A) Proximal ends of pedal claws l-lll of Apatosaurus excelsus (CM 89) with arrows denoting the position of the llexor tubercles. (B) Ventral uietu of articulated digits I-III, u'ith large Arrows representing the
path of the breuis flexors onto the flexor tubercles of clau,s I-lil.
have penetrated the soil in parallel with the feet as they do in digging mammals. Instead, as described above, the claws apparently flexed and twisted into the substrate perpendicular to the direction of locomotion. Such a functional arrangement of the claws seems better suited to provide traction and perhaps prevent the miring of the animal rather than primarily acting as digging devices. Thus, the suggestion by Gallup (1989) that sauropods were scratchdiggers is considered unlikely. Improved plantarflexion may be another functional advantage
derived from an anterolateral pes orientation. As sauropods retain a large metatarsal V, this element would become the most posterior element in the pes. As discussed previously, the semi-plantigrade posture of the pes may have resulted as a compromise solution to maintaining the mechanical advantage of the plantarflexors. Retaining a prominent metatarsal V that is both posterior and conPes
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joined strongly with metatarsal IV affords a "pseudocalcaneum" for attaching both plantarflexor musculature and pedal pronators. In birds, the plantar aponeurosis is reduced in size and functionai significance because most of the musculature of the foot consists of long flexor and extensor tendons from the leg (George and Berger 1,966;Proctor and Lynch I993). As described previously, the morphology and posture of other saurischian dinosaurs resemble those of birds, which suggest they also lacked an extensive plantar aponeurosis and intrinsic foot musculature. If the plantar aponeurosis had become reduced during the early bipedal ancesrry of sauropod dinosaurs, a srrong, bony attachment for anchoring plantarflexor musculature may have become necessary to augment the push-off of the pes at the end of the support phase. In addition, a pes with a strongl)r outturned anterolateral orientation would requrre strong pronators to correct potenrial rollover or inversion problems caused by the new pedal configuration. Eversion of the pes during plantarflexion assures that the angled posterior region would lift up from the sediment during the beginning of the pushoff, rather than having the posterior portion of the pes drag obliquely into the sediment during plantarflexion, causing unnecessary and possibly dangerous inversion or rollover. Bonnan (200 l) provides a more detailed consideration of metatarsal V as a "pseudocalcaneum" and a more detailed functional analysis of this functional problem is in prepararion. Metatarsus shape and metatarsal ridges. Two other fearures typical of many sauropod pedes deserve brief menrion here (a more detailed consideration of these features is planned). First, the articulated metatarsus of basal sauropods and eusauropods forms a gentle arch when viewed proximally, whereas those of neosauropods have a more linear arrangement (see Fig. 16.4). The arched morphology of the metatarsus in basal sauropods and eusauropods is reminiscent of arched or bow-like structures observed in other tetrapods (dorsally arched vertebral columns, plantar arch of humans and other mammals, etc.). Such structures provide addi-
tional resistance and flexibility when loaded, and in some cases release stored kinetic energy when unloaded (Hildebrand 1995). The difference in proximal meratarsus shapes betrveen basal/eusauropods and neosauropods may further reflect changes in foot posture and weight-bearing between these tara. As noted previousiy, some Middle Jurassic trackways (Santos et al. I994) suggesr basal sauropods or eusauropods possessed a more anteriorly directed pes. At present, it is unclear why neosauropod taxa would lose an arched arrangement of the metatarsus. Perhaps in an anterolateral orientation, distribution of compression or shear is better accomplished through a linear, blocklike arrangement of the metatarsals, but this suggestion is presently speculative. Second, the diplodocids Apatosaurus, Diplodocus, and Barosaurus have low but prominent lateral ridges on the anterior faces of their metatarsals I-III (Upchurch 1995 pers. obs.) (Fig. 16.9). These ridges may have been formed by strong pedal extensors. In
368 . Matthew
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exdl
Fig. 16.9. Metdtdrsal ridges in
exhal
dip lodo cid sauropods. U p ch ur ch
exdl
exhal
I
D
(1995) noted the presence of a dorsolateral ridge on metatarsdl II of Barosaurus ard Diplodocus, artd Bctnnart (2001) notes the presence of such ridges ort metdtarsals 1-III lz Apatosaurus, Barosaurus, ard Diplodocus. Tbese ridges ntat' be mttscle scars related to powerful dorsiflexors. /Al Apatosaurus ercelsus (CM 89) arti culttted tnetdtursus ut anterodistal uieu shouing ridges. (B/ Diplodocus ha"vi (HMNS 17.t) drticuldted pes in dnterodorsal uieu shoa,ing ridges. Abbreuiations: exdl = extensor digitorum contmunis; exhal = extensor hallucis.
l.l t
1---------
{z a-{ -___.: _\
-t-.\
J"
,-.^-/^\
**{ \,
=i
Fig. 1 6.1 0. Presence oi laterodistal tab on metdtarsal I of diplodocids. Anterior uiett' oi the left first nrctatarsals o/ /A/ Cetiosaurus. (B/ Euhelopus, /Cf Camarasaurus, /D) Cetiosauriscus, /E/ Apatosaurr-rs, /.f.) Diplodocus, and (G) Baro.ruru'. Nnte lhat o disti,tct, pointed laterodistal tab has fonned on the distal articular surfate (indicated by arrous) only irr tbL diploducids rD-Gt. Littc dratuirtgs tru;dified lrom Mchttosh (1ee0).
Alligator mississippiensls and other crocodylians, Mm. tibialis anterior, extensor digitorum communis, and extensor hallucis insert on the lateral side of the anterior faces of the first three meratarsals (Reese 1915; pers. obs.). These three muscles or their homologs may be responsible for the lateral ridges observed on metatarsals I-III in diplodocids, and might indicate more powerful dorsiflexion in these sauropods (see Bonnan [2001] for more details). Furthermore, all known diplodocids (Apdtosaurus, Barosaurus, Cetiosauriscus, Diplodocus) also possess a posterior and laterally projecting tab on metatarsal I that is absent in other sauropods (Mclntosh 1990, fig. 1.6.191' pers. obs.) (Fig. 16.10). Upchurch Pes
Anatomf in Sauropod Dinosaurs
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(1998) suggested that this process was also presenr in taxa of Brachiosauridae , Shunosaurws, and Omeisaurus. Although a small laterodistal projection is present in these taxa, it is not well developed nor does it flare laterally to a point as observed in the diplodocids.
Therefore, the condition described here is regarded as a distinct diplodocid character because it is consistently pronounced only in these taxa, and it is very subdued in other non-diplodocid sauropods. However, functionally it may represent the extreme of a particular musculoskeletal mechanism present in all sauropod taxa rhar may have acted ro adducr merararsal I (see Bonnan 1)OOtl for
more details).
Phylogenetic and Evolutionary Implications of Sauropod Pes Anatomy
In recent sauropod phylogenies, several tarsal and pedal features were suggested and utilized as synapomorphies in the clades Sauropoda, Eusauropoda, and Neosauropoda (Upchurch 1998, twelve characters; Wilson and Sereno 1998, nineteen characters; Wilson 2002, twenty-three characters). Based on the inferred functional morphology of the sauropod tarsus and pes described above, the assignment and significance of these synapomorphies are briefly evaluated and discussed here. Several characters in Wilson and Sereno (1998) and Sfilson (2002) are based on differences in the length or area of particular pedal elements, and the functional anc phylogenetic implications of these characters will not be considerec here because their utility lies mostly with taxonomic identification and partitioning. Instead, the discussion will focus on rhose characters with clear functional and evolutionary implications for the Sauropoda in a broader conrexr {see Tabie 16. l). Most of rhe synapomorphies proposed by Upchurch (1998), Y/ilson and Sereno (7998), and 'Sfilson (2002) are limited to eusauropod and neosauropod taxa. However, the preceding examination of the sauropod tarsus and pes suggests many of their proposed characters have a wider distribution among the Sauropoda and that several synapomorphies actually are part of a single, functional suite. To facilitate comparison with the phylogenetic analysis of Upchurch (7998), Neosauropoda has been simplified from the more complex distribution presented in \ililson and Sereno (1998) and Wilson (2002). Several synapomorphies define monophyletic groupings of Neosauropoda plus additional eusauropods in the phylogenetic analyses of Wilson and Sereno (1998) and 'Wilson (2002). Here, all such synapomorphies are grouped under Neosauropoda (see Table 16.1). To avoid misinterpreration and to acknowledge this simplification, "Neosauropoda" or "neosauropods" rvill be used throughout the remainder of the discussion. Proposed synapomorphies for the sauropod astragalus are mostly restricted to the "Neosauropoda," with a single character state recognized within basal sauropods (see Table 16.1). Most of the synapomorphies are concerned with the ascending process of
370 . Matthew
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TABLE 16.1. Selected Synapomorphies from Upchurch (1998) and Wilson and Sereno (1998) for the Tarsus and Pes in Sauropods
Clade
Synapomorphy
Authors
Sauropoda
Astragalus, foramina absent from base of ascending process Distal tarsals (3, 4) absent or fail to ossify
Wilson and Sereno
I ungual enlarged I ungual deep and narrow (sickle-shaped) Eusauropoda Metatarsal I minimum shaft width greater than that of metatarsals II-IV; metatarsal I is short and very robust Pedal digit Pedal digit
Spreading metatarsus configuratton
Neosauropoda
Upchurch 'Wilson and Sereno 'lTilson and Sereno
'lfilson and Sereno Upchurch V/ilson and Sereno 'STilson
and Sereno
Loss or extreme reduction of collateral ligament pits on pedal
Upchurch
phalanges Pedal digits II-III with sickle-shaped unguals Pedal digit IV has three phalanges or fewer Pedal digit IV ungual rudirnentary or absent
'Wilson and Sereno Upchurch
Wilson and Sereno
Posterior fossa of astragalus divided by vertical crest Ventral surface of astragalus is transversely convex Anteromedial corner of astragalus is truncated; narrows toward its medial edge Ascending process of astragalus extends to posterior margin of the astragalus Proximal phalanges narrow toward their lateral and palmar (plantar?) margins Pedal unguals asymmetrical (canted ventrolaterally in articulation)
\Wilson and Sereno Upchurch Upchurch 'Vfilson and Sereno 'Wilson and Sereno Upchurch 'Wilson and Sereno
the astragalus, but all are probably related features of a single phenomenon. As described previously, the astragalus was reoriented in sauropods such that its distal roller was oriented anteroventrally instead of directly ventrally. This was accomplished, in part, by redirecting the ascending process of the astragalus posteriorly such that it keyed beneath the distal end of the tibia. Thus, the absence of foramina from the base of the ascending process, division of the posterior fossa by a vertical crest, and the posterior extension of the ascending process ('sfilson and Sereno 1998; Wilson2002) are probably related features of a single character. The vertical crest that divides the posterior fossa is a buttress-like feature that fuses with the ascending process posteriorly. Such a feature may have de-
veloped in concert lvith the posteriorly redirected ascending process in sauropods, because it is conspicuously absent in other saurischians that possess a more vertical and anterior ascending process. Furthermore, the development of the buttress-like crest would probably act to obliterate foramina from the base of the ascending process. Again, since this vertical crest is absent in other saurischians, its appearance in sauropods would suggest that it overgrew or displaced the original foramina. Therefore, these three Pes
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features probably represent a singular developmental event and not
independent svnapomorphies. Moreover, most of the astragalus synapomorphies proposed for "Neosauropoda" actually occur in more basal sauropods. As noted above, the astragalus of Vulcanodon does have an ascending process that extends posteriorly and a vertical crest that divides the
posterior fossa, although these features are not as prominent as in other sauropods. In addition, the anteromedial corner of the astragalus
in
Vttlcanodon does narrow toward its medial end (Cooper
7984, fig.25). The major differences between the astragalus of a basal sauropod like Vulcanodon and neosauropods appear to be the truncated, trianguiar outline of the medial apex of the astragalus and a more transversely convex, distal roller in the latter group. Such differences may underlie changes in the orientation of the pes or rts flexibility at the ankle. However, it appears that most of the proposed astragalus synapomorphies appeared in basal sauropods and are related to a change in astragalus orientation early during sauropod evolution. The absence of ossified distal tarsals is supported solely on negative evidence: no distal tarsals have ever been reported or recovered for any described sauropod. As suggested previously for the sauropod calcaneum (Bonnan 2000), this character stare should be withheld from sauropod phylogenetic analyses. As with sauropod calcanea (Bonnan 2000), if ossified distal tarsals were indeed present in sauropods, such elements might be rarely preserved and could be easily overlooked or misidentified during collection and curation. Furthermore, as described previously, the morphology of the metatarsals and the distal ends of the astragalus and calcaneum support a h,vpothesis that predicts the former articulated directly u'ith the latter, forming a unique tarsometatarsal ankle-joint in sauropods. Although it might be suggested that the presence of a tarsometatarsal ankle should replace the absence of ossified distal tarsals as a synapomorphg the present data strongiy suggest rhat characters related to the function of the ankle or to the presence or absence of its elements be removed from phylogenetic consideratlons.
Many of the proposed synapomorphies concerning the metatarsals and phalanges appear to be tied to foot posture and pes asymmetry. The development of a craniocaudally foreshorrened, robust, cube-like first metatarsal (Upchurch 1998; Wilson and Sereno 1998) and a spreading metatarsus configuration (\X/ilson and Sereno 1998) appear to have occurred simultaneously in the evolution of sauropods.In Antetonitrus, the first metatarsal is relatively short with an elliptical cross-secrion, but it is relatively longer than those of eusauropods (Yates and Kitching 2003). It is difficult
to ascertain from available figures whether the first metatarsal of Vulcdnodon was robust and cube-like (Raath 1972, fig.9) or more elongate (Cooper 7984, frg. 27), or whether the metatarsus was spreading or bound. However, these features certainly appear in all
described eusauropods, and this suggesrs that the adoption
.
Matthew F. Bonnan
of
a
semi-plantigrade foot posture was acquired early during sauropod evolution. If what is observed in the morphologv of the Vulcanodon astragalus has any bearing on the posture of the foot, it might be tentatively suggested that the pes of this sauropod was also semi-plantigrade. As suggested by trackway evidence, metatarsal I appears to have absorbed and distributed a significant proportion of the weight-bearing stress channeled through the foot, and the presence of its cube-like morphology in most or all known sauropods suggests that the asvmmetrical loading of the pes may have occurred earlier than current phylogenies imply. Enlargement, mediolateral compression, and development of a sickle-like curvature characterize the first pedal ungual in most known sauropods, including basal forms such as Vulcanodon lWtlson and Sereno 1998), as well as the morphology of claws II and III in eusauropods (\Wilson and Sereno 7998). This morphology may have enhanced the abilitv of the pes to gain traction on various substrates: their recurved shapes suggest an ability to grip, whereas their tall and deep bodies may have allowed them to "shovel" blade-like into sediment. Without knowledge of the number oI phalanges and the presence of claws on digits IV and V of Vtilcanodon (Cooper 1984) or Antetonitras (Yates and Kitching 2003), it is difficult to know whether such basal sauropods still favored their three inner digits during locomotion or whether the pes was already being loaded asymmetrically. The flatter and broader claws of the second and third digits in this Yulcanodon tentatively support a more symmetrical weight distribution through the foot. Extreme reduction or loss of collateral ligament pits on the phalanges (Upchurch 1998) appears to be a definitive eusauropod character that correlates well with observations suggesting the phalanges and unguals could slide and rotate mediolaterally in these dinosaurs (see above). The inferred absence of strong ligaments holding the phalanges together would presumably allow sliding and rotational movements to occur between the phalanges. Reduction in the number of phalanges on digit IV (Upchurch 1998) and the absence or rudimentary morphology of the ungual on digit IV (Wilson and Sereno 1998) are synapomorphies of eusauropods that correlate with the asymmetrical structure of the pes: because the pes was apparently loaded asymmetrically, the innermost claws would be more effective in providing traction, whereas claws on the outermost digits would presumably be less effective. These two synapomorphies are likely interlinked: reduction in the number of phalanges on the fourth digit and reduction or loss of the fourth digit unguai probably occurred simultaneously. Therefore, it is suggested that both of these synapomorphies be considered a single character. Narrowing of the proximal phalanges later-
ally and toward their plantar margins (Upchurch 19981, and the asymmetrical canting of the pedal unguals (Wilson and Sereno 1998), appear to be interlinked neosauropod synapomorphies. Both features are necessary to cant the claws ventrolaterally, and both features probably evolved in concert. The asymmetrical orienPes
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tation of the phalanges and claws in neosauropods may be correlated with a more anterolateral orientation of the pes (see above). Again, such a morphology may have aided the claws in providing traction to the foot by allowing them to dig into the substrate perpendicular to the direction of travel. This overview of sauropod tarsal and pedal anatomy suggests most of the diagnostic characteristics of these giant herbivores were acquired early during their evolution and were retained relatively unmodified into derived groups. A significant change in foot posture occurred in the basal sauropods as the astragalus reoriented itself through posterior deflection of the ascending process. Reorientation of the astragaius would in turn have effected the orientation of the digits, and the sauropod pes changed from an ancestral digi-
tigrade posture to a semi-plantigrade, spreading arrangement. \Thether this change occurred in basal sauropods or later in eusauropods is presently unclear, but the similarity and orientation of the astragalus in Vulcanodon compared to those of eusauropods tentatively suggests a semi-plantigrade, spreading pes posture is a synapomorphy of all sauropods. Distal tarsals were possibly further reduced, lost, fused to adjacent eiements, or retained in cartilage. It is possible that the metatarsals articulated directly with the astragalus and calcaneum, forming a unique tarsometatarsal ankle joint. The first ungual became enlarged, deep, narrow, and sickleshaped, and its morphology indicates an asymmetrical loading of the pes in the earliest sauropods. Subsequent changes in later sauropods involved the development of enhanced phalangeal movement (eusauropods), a more asymmetrical pes (eusauropods), a less arched proximal metatarsus (neosauropods), and acquisition of an anterolaterally oriented foot (neosauropods). Unlike elephants, phalangeal movement appears to have increased in eusauropods, and may be correlated with an increased role and involvement of these elements during locomotion. Extreme reduction of ligament pits on the phalanges suggest "improved" sliding and rotational movements of these elements in eusauropods that correlate with the broad and asymmetrical morphology of their articular surfaces. There appears to have been a change from a more anteriorly directed pes in eusauropods to an anterolaterally oriented pes in neosauropods, and the more linear arrangement of the metatarsals in the latter taxon may be correlated with such a change. In the absence of a rigorous cladistic analysis, it is tentatively suggested that the prorimal arching of the metatarsus may be a synapomorphy of eusauropods that was subsequently modified in neosauropods.
Summary and Conclusions The sauropod tarsus and pes were shaped by the adoption of a graviportal posture and subsequent changes of the ankle and foot in basal sauropods from the digitigrade pedes of their bipedal saurischian ancestors. The development of a semi-plantigrade foot
j-4 .
Matthew F. Bonnan
posture may have first afforded greater mechanical advantage to plantarflexors on a shortened pes while secondarily acting to distribute weight over a larger surface area. Sauropods may have early developed a unique tarsometatarsal ankle in which the metatarsals articulated directly with the astragalus and calcaneum, perhaps conferring mechanical safety by restricting the pes to largely parasagittal movements. The asymmetrical pedes of eusauropods and neosauropods may have functioned to improve traction and plantarflexion, and phalangeal mobility appears to have increased in Eusauropoda perhaps to enhance claw participation during locomotion. Diplodocids have prominent ridges on their first three metatarsals and a laterodistal process on their first metatarsal, which may be muscle scars related to increased dorsiflexion of the pes and adduction of the first digit, respectiveiy. Several synapomorphies proposed for eusauropods and neosauropods actually may have been present in basal sauropods, especially several related to the redirected ascending process of the astragalus. Overall, the shape and function of the sauropod tarsus and pes was probably acquired early during their evolution with subsequently modest changes to a generally conserved morphology. Acknowledgments. A portion of the work presented here is derived from a dissertation on sauropod locomotion completed under J. Michael Parrish at Northern lllinois University (NIU). I wish to extend my thanks to J. M. Parrish and the members of my disserta-
tion committee for their help and discussions in the initial stages of this research: N. Blackstone, D. Gebo,'W. Hammer, and V. Naples. Special thanks go to D. Chure (DNM) who inspired my initial interest in the functional morphology of sauropod feet, and to J. S. Mclntosh for stimulating discussions on sauropod limbs and feet over the past few years. I thank my reviewers, K. Carpenter, V. Tid'lfilhite, well, and R. for constructive comments that improved the
quality of this manuscript. For their hospitaiity during this research, I would like to thank D. and J. Gillette, L. D. Martin, R. Schoch, D. Unwin, and M. and V. \X/edel. B. Curtice and J. S. McIntosh kindly provided the author with Chinese literature. C. Potter, J. Ososky, V. Naples, and the staff of the Smithsonian Zoo generously arranged for the dissection of the female elephant, and V. Naples, D. Domning, and B. Beatty were of great assistance during the dissection. Finally, I extend m1' sincerest appreciation for the hospitality and assistance of curators and staff at all museums I have visited. especially for help with some very heavy bones: Eugene Gaffney and staff (AMNH); Ken Stadtman (BYU); Don Burge, Iohn Bird, Duane Miller, and staff (CEU); David Berman, Betty Hill, and staff (CM); Dan Chure (DNM); William Simpson, Bill StanleS and staff
(FMNH); staff (HMNS); Larry Martin and staff (KUVP); David Unwin and staff (MNB); Brooks Britt and Rod Scheetz (M\fC); Mike K. Brett-Surman, Bob Purdy, Ralph Chapman, and staff (NMNH); Richard Cifelli, Matt'Wedel, and staff (OMNH); Rainer Schoch (SMNS); Bill'Wahl and staff (TATE); Paui Sereno and staff Pes
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(UC); David and Janet Gillette (UMNH); and Christine Chandler, Mary Ann Turner, and staff (YPM). This research was supported by the American Museum of Natural History Theodore Roosevelt Memorial Grant, a Sigma Xi Grant-in-Aid-of-Research, J. Kirkland and the Dinamation International Society, a Dissertation Completion Fellowship at NIU, and a University Research Council grant from'Western Illinois University. References Cited
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Matthew F. Bonnan
17. Sauropod Stress Fractures ulues to Actlvltv
as
la.
Bnucn M. RoTHSCHTLD AND RerpH E. MorNen
Abstract The fossil skeletal record provides not only evidence of structure but also clues to activity and lifestyle. The picturesque, tripodal stance of the Barosaurws skeleton at the American Museum of Natural History in New York stimulated testing of the hypothesis that sauropods stood on their hind legs. Assuming a tripodal stance would exert extreme forces on thoracic and lumbar vertebrae, whereas resuming a normal posture from a tripodal stance would potentially exert extreme forces on thoracic and lumber vertebrae, the metacarpals, and the manus phalanges, unless counterbalancing allowed an exquisitely slow, controlled descent. Evidence of these excess forces would be stress fractures and tendon calcifications, which leave very characteristic alterations in bone appearance. The thoracic and lumbar vertebrae, phalanges, and metapo-
dials of sauropods were therefore examined macroscopically for these definitive surface abnormalities. Stress fractures were found
in 5"/. of sauropod metatarsals available for study. No alterations were found in the manus of any sauropod dinosaurs, nor were stress fractures found in vertebrae. Pes localization is compatible 381
with gait-derived stresses, not with descent from a tripod position, thereby falsifying that hypothesis, but suggesring significant migration habits.
Introduction Sauropod activity levels have been a source of great interesr, extending from earl,v notation of tail injuries to rhe picturesque, tripodal sauropod mount (Fig. 17.1) in the rotunda at the American Museum of Natural History (Coombs 1975; Moodre 7923; Myhrvold and Currie 1997).Illustrating the feasibility of the latter is an interesting exercise, but that hypothesis is untested. Assuming a tripodal stance would exert extreme forces on thoracic and lumbar vertebrae (Resnick 2002). The resumption of normal posture from a tripodal stance would potentialiy exert extreme forces on thoracic and iumbar vertebrae, metacarpals, and manus phalanges. One way of assessing these excessive forces is to look for evidence (i.e., stress fracture or tendon calcification) in the vertebrae, pes, and manus of sauropods, thereby testing the stance hypothesis. Bal-
let dancers develop pedal-stress fractures related to landing "en pointe," rather than when assuming the "pointe" position (Quirk 1994; Resnick 2002; Rothschild 1988; Thomasen 1982;'$Tashington 1978). In testing the tripodal stance hypothesis, the presence of such injuries indicates that the stance was adopted, and the absence of these injuries indicates that this stance was not adopted. This mode of testing is pursued (rather than assuming that the tripodal posture was adopted but that, for some unknown reasons, it never resulted in injury). However, given experience with proboscidea (Rothschild et al. submitted) and scaling (Alexander 1989; Alexander et al. 1979; Anderson et al. 1985; Bertram and Biewener 1990; Biewener 1989; Campbell and Marcus 1992; Hokkanen 1986; McMahon 1975), sauropods would be expected to have a higher frequency of stress fracrures if they engaged in tripodal stance than
if they did not. Previous rvork (e.g., Bakker 1971; Horvel|7974; Jensen 1988) sought to demonstrate rhe feasibility of the tripodal stance, with the assumption that if the stance was biomechanically possible, it must have been adopted. However, none of these studies undertook biomechanical stress-load analysis. The musculoskeletal sysrem does permit animals to porenrially do things they would never actually do. For example, it is biomechanically possible for human beings to swim, but not all actually learn how to do so. It is the study of paleopathologies that allorvs us to ascertain what the creatures actually did, rather than what they were capable of doing. Bones exhibit the results of a lifetime of stresses and injuries, at least those which occurred subsequent to juvenile bone remodeling. For example, stress fractures in ceratopsian phalanges are related
to repetitive activity (Rothschild 1988; Rothschild and Tanke 1992; Rothschild et aI.2001). In contrast to acute fractures caused
i82 .
Bruce M. Rothschild and Raloh E. Molnar
Fig. 17.1. Lateral uiew of the lj' ntotmted Barosaurus a/ the American Mttsettnt of Natural tr ip o dd I
H i st or.t. St r e s s fr actur e s, euidenced b1, focal eleudted areas, are prediclcd fur lhis rel]elitirc stdTtce.
by sudden injurl', exposure to periods of strenuous activity may result in stress (fatigue) fractures (Daffner 1.978;Hardey 1943; Morris and Blickenstaff 1.967; Orova et al. 1978; Rothschild 1982, 1988; van Hall 1982). The result is a focal elevated zone or "bump" marring the bone surface. Such a distortion was first noted on the fourth left proximal phalanx of a cast of the Chinese sauropod Nurosaurus qagdnensls (Fig. 17.2), from the Qagannur Formation, Inner Mongolia, southeast of Ehrenhot. Its location and shape suggested a stress fracture, rather than a defect in the cast. This discovery led to a systematic survey of sauropod phalanges, metapodials, and vertebrae.
Institutiondl dbbreuiations. AMNH-American Museum of Natural History, New York, New York; BYU-Brigham Young University Museum, Provo, Utah; CM-Carnegie Museum of Natural HistorS Pittsburgh, Pennsylvania; DINO-Dinosaur National
DM-The Dinosaur Museum, Blanding, Utah; FHSM-Fort Hays Museum of Natural History, Fort Hays, Kansas; GMNH-Gunma Museum of Natural History, Gunma, Monument, Utah;
Japan; KUVP-University of Kansas, Lawrence, Kansas;
LACM-
County Museum of Natural History, Los Angeles, California; PALEON-\Tyoming Dinosaur International Society, Laramie, Vyoming; RMFM-Richmond Marine Fossils Museum, RichSauropod Stress Fractures as Clues to
Activity .
383
Fig. 17.2. Anterior-oblique uieu of Nurosaurus qaganensis /oot
with
stress
fracture (arrou).
mond, Queensland, Australia; RTMP-Royal Tyrrell Museum, Drumheller, Alberta, Canada; SDSM-South Dakota School of Mines, Rapid City, South Dakota; UMNH-Utah Museum of Natural History, Salt Lake City, Utah; USNM-National Museum of Natural History, Washington D.C.; UT-University of Texas, Austin, Texas; WDC-'$Tyoming Dinosaur Center, Thermopolis, Wyoming; and YPM-Yale Peabody Museum, New Haven, Connecticut.
Methods Thoracic and lumbar vertebrae (especially the pars interarticularis), phalanges, and metapodials of sauropods were examined macroscopically for surface abnormalities in the collections listed above (Table 17.1). Femora were not examined in this analysis, although occasional femoral stress fractures are reported in ballet dancers (Resnick 2002). The weight of these large bones made them difficult to manipulate to assess all surfaces, and statistically significant complete specimens were not available. Stress fractures were recognized macroscopically as focal elevated areas. Absence of filigree or aero, candylike new bone formation distinguishes them from bone infection or osteomyelitis (Resnick 2002; Rothschild and Martin 1993).In those elements where surface abnormalities were found, stress fractures were recognized radiologically as oblique, radiolucent, knife-slice-like clefts, with smudged (indistinct) periosteal overgrowth forming a distinctive surface bump (Resnick 2002; Rothschild and Martin 1993). Other pathologies can be ruled out because they differ in their appearance or position. Osteoarthritis is recognized by osteo-
384
.
Bruce
M. Rothschild and Ralph E. Molnar
Table
'1.7.1.
Sauropodomorphs Examined for Stress Fractures and Exostoses
vertebrae
Amargosatrus Apatosdurus Barosaurus
0
50
Manus
Pes
dorsal metatarsals U
It
phrlanges
metaca rpa ls
phalanges
10
18
0
39
7
1J+
8
4
5
0
30
Brachiosaurus
10
19
0
0
25
Camdrasaurus
6I
,)L
19
23
411
Cetiosaurus
U
0
0
6
15
Diplodocus
53
56
-)L
+/
Haplocanth osaurus Massospondylus
3
0
0
0
9
0
0
0
0
Morosaurus
0
0
0
1
23
Nurctsaurus
8
18
8
8
8
JLO
45
Sauropod indet.
95
0
50
0
85
Plateosaurtrs
99
33
16
33
94
phytes, or overgrowths of bone, at the joint (articular) margins (Altman et al. 7990, 799I, 1986; Resnick 2002; Rothschild and Martin 1993), as opposed to tendon calcifications and exostoses, which are diaphyseal in location. The term "exostosis" describes a spicule of bone. Whereas it may represent a residual bone "splinter," it is neither a fracture callus nor infection-related. If the splinter of bone contained cartilage from the original fracture, that cartilage may grow to produce a "head" on the exostosis (\fang and Rothschild 1992) and is referred to as an osteochondroma. Vertebral centra osteophytes identify spondylosis deformans, an apparent physiologic phenomenon that is not specifically relatable to pathoiogy or disability (Resnick 2002; Rothschild in press; Rothschild and Martin 7993). Tendon calcification and stress fractures demonstrate repetitive stress applied to a specific bone region (Resnick 2002). A focal elevated zone, diagnostic of stress fractures, was found only in metatarsals. Their occurrence was analyzed rn,ith Chisquare statistics to determine the significance of their apparent absence in the manus and vertebra as well as the susceptibility of sauropods rather than prosauropods to stress fractures.
Results The only forefoot pathology observed in a sauropod was a partial greenstick fracture that was not a stress fracture (Metacarpal II, KU 1,2971,3). A spicule had formed when bone was peeled off during Sauropod Stress Fractures as Clues to
Activity . J$J
TABLE 17.2.
Distribution among Sauropods of
Stress Fracture/
Tendon Calcification Taxon
Metatarsal
Phalanx
Apatosaurus
I, IV IV
IV
Barosaurus
il
Brachiosaurus Camarasaurus
IV I, II
Diplodoats
il
Nurosdurus Unidentified
IV
I,V
the fracture. Neither stress fractures, osteophytes, nor tendon calcr-
fications (spinal process excepted) were found in the manus elements or dorsal vertebrae of any sauropod. The Chi-square results for metacarpals and manus phalanges are 5.565 (p < 0.025), and for vertebrae are 38.83 (p < 0.00001). In contrast to these results, three varieties of pes pathology were found: tendon calcifications, stress fractures, and osteoarthritis.
Tendon calcificdtions. Tendon calcification-exostoses, which reflect calcification of a muscle insertion, are known in Apatosaurus metatarsal I ("Bertha," PALEON 001) and metatarsal V (CM 21782). A similar lesion is known on merararsal II in Bdrosaurus (DINO 874). Stress fractrtres. Focal elevated areas (Table 17.2) are present in several specimens of Apatosaurus: PALEON 001 (Fig. 17.3) rn metatarsal IV and adjacent phalanx, BYU 4647 in metatarsal V (Frg.1,7.4), BYU 10023 in merararsal I, and BYU 12581 in a proximal phalanx. ln Camardsaurus it is known in metatarsal II of KU 729713 and GMNH-PV 101 (Mclntosh et a1.1996; Fig. 17.5); in metatarsal lI of Diplodocus BYIJ 10041; in metararsal ly of BrdchiosaurusKU 129724; in metatarsals V of unidentified sauropods: BYU 12214 and BYU 71415; and in metatarsal I of ANSp 21122 and UT 41425. A similar bump is visible on the fourth phalanx of I'trurosaurus qaganensis (Frg. 77.2; Table 17.1). These pathologies are in contrast with normal metatarsals of the tripodally mounted Baroscturus (Fig. 1 7.5). The stress fracture samples (74 of 380) occur in meratarsals I, II, IV, and V. Only one example of a pedal phalangeal srress fracture was noted (BYU 12581). Hindfoot stress fractures were pres, ent rn Apatosaurus, Barosaurus, Diplodocus, Brachiosaurus, Camdrasdurus, and Nurosaurus. Farlure to recognize the phenomena in other genera is not statistically significant, and is related to the rarity of pedal elements. The pattern of stress fractures shows no discernible frequency differences among the genera. Though
386.
Bruce
M. Rothschild and Ralph E. Molnar
Fig. 17..3, Apatosaurus "Bertha" (PALEON 0 0 7 ). P o sterior-oblique uiew of proximal phaldnx reuedling linear raised areas (arrows), from stress fractures.
Fig. 17.1. Anterior uietu of Apatosaurus (BYU'+617). Midshaft bump from stress
fracture is Prominent.
Sauropod Stress Fractures as Clues to
Activity . l$/
t.ll ',i;12:,,L
;i',:":,
Fig. 17.5 . Anterior uieu of the
foot of Barosaurus ln AMNH rotunda.
Fig. 17.6. Anterior uiew of proximal articular surface of the fourth proximal pbalanx of Apatosaurus "Bertha." Rim of new bone dt superiol aspect
identifies dn osteopb),te osteoarthritis.
of
prosauropods were unaffected, statistical significance was not achieved (Chi-square =2.929, p > 0.08). Osteoarthritis. The proximal arricular surface of the fourth proximal phalanx on Apatosaurzs (PALEO 001) is rimmed at its proximal end by new bone (Fig. 17.6), forming an osteophyte. A
388
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Bruce
M. Rothschild and Ralph E. Molnar
similar osteophyte is observed at the same location in the adjacent fifth phalanx. Osteophytes are also present in hindfoot proximal phalanges
IV III, and II of Camarasaurzs (KU 729716).
Discussion The greenstick fracture in metacarpal II (KU 729713) represents the only forefoot pathology seen, and represenrs an acute injury (Resnick 2002). Such fractures occur when the elastic modulus of immature bone is exceeded, implying that the individual was immature at the time of the injury. This contrasts with the repetitionrelated stress fractures discussed below. In contrast, the appearance of focal elevated areas on sauropod metatarsals and foot phalanges is pathognomonic (characteristic and unequivocally diagnostic) for stress fractures (Daffner 1978; Kroening and Shelton 1963; Morris and Blickenstaff 1967: Rothschild 1982: Rothschild and Martin 1993; \Wilson and Katz, 1969). These lesions are easily distinguished from osteomyelitis (bone infection), because no bone destruction has occurred (Daffner 1978; Rothschild 1982, 1988; Resnick 2002; Rothschild and Martin 1993\. These lesions also lack the sclerotic perimeter seen in benign bone tumors, such as osteoid osreoma, which do not manifest surface reaction anyway. No perturbation of bony architecture is identifiable as is evidenced for a primary malignant bone tumor (Daffner 1978; Resnick 2002; Rothschild and Martin 1993). Such tumors are usually associated with spiculated or thin laminated periosteal reaction and were not seen in the examined sauropods. Metabolic disorders, such as hyperparathyroidism and hyperthyroidism, typically have subperiosteal reaction and also were not seen. Stress fractures in humans are related to periods of unconditioned strenuous activiry or repetitive srress force (Morris and Blickenstaff 1967; Resnick 2002; Rothschild 1982, 1988; Rothschild and Martin 1993). with feet and back vertebrae most com-
monly affected in ballet dancers (Daffner 1978; Kroening and Shelton 1963; Morris and Blickenstaff 1967; Rothschild 1982; Rothschild and Martin 1993; Wilson and Katz 1969). Reports of stress fractures exclusive of humans are rare, Nevertheless, some have been documented in racehorses, racing greyhounds, and ceratopsians, where locaiization to metatarsal V is compatible with gait, not with descent from a tripod position (Devas 1967; Morris
and Blickenstaff 1967; Rothschild 1988; Rothschild and Martin 1993\.
The absence of stress fractures in the forefeet is intriguing. Sauropod forefeet have reduced phalanges suggesring semidigitigrade feet analogous to modern Elaphas. That is exactly the posture in humans that produces stress fractures in ballet dancers (Hamilton et al. 1996; Quirk 1994; Resnick 2002; Thomasen 1982; \X/ashington 7978). Therefore, its absence in the sauropod manus is incompatible with descents from a tripod position. Articular alterations in the fourth proximal phalanx of ApSauropod Stress Fractures as Clues to
Activity .
389
cttoslurus (PALEO 001) and in middle phalanges from a Camardslurus (KU specimen) are pathognomonic for osteoarthritis (Resnick 2002; Rothschild and Martin 1993). This condition is extremely rare in dinosaurs (Rothschild and Martin 1993) and has not previously been reported in sauropods. The association of osteoarthritis with a stress fracture in a sauropod suggests altered foot biomechanics related to the stress fracture and. therefore. is a secondary osteoarthritis. The stress fracture would have changed mechanical forces across the foot, the circumstance apparently necessary for development of osteoarthritis (Rothschild and Martin 1993). However, osteophytes in the pes in another Camardsaurus IKU 1.29716) are not associated with stress fractures. These osteophytes are unique in sauropod feet and indicate osteoarthritis (Altman et al. 7986,1990,1991), which is not reiated to weight but to activity.
Conclusions The articulating joints of sauropods had a sufficient range of motion to allow a tripodal stance, but the paleopathologic record does not support this hypothesis. Manus stress fractures are predicted as the sauropods descended from a tripodai stance, but the evidence is absent in the large sample size. Pedal-stress fractures, however, are common, occurring in 5"/. of the sample. This percentage suggests that the hindfoot provided much of the propulsive thrust, a perspective confirmed by the unique occurrence of osteoarthritis in that location. Acknowledgments. Appreciation is expressed to Robert Bakker, Gordon Bell, David Berman, Dan Chure, Stephen Czerkas, Gene Gaffney, David Gillette, Greg Liggett, Larry Martin, Scott Moses, Nancy Rufenacht, Bukhard Pohl, Robert Purdy, Kenneth Stadtman, J. D. Ster,vart, Darren Tanke, Mary Ann Turner,'!(iilliam Wahl, and Richard Zakrzewski for assistance in accessing the colIections they curate, and to Kenneth Carpenter and anonymous reviewers for their cogent comments. References Cited
Alexander, R. M. 1989. Mechanics of fossil vertebrates. Journal of the Geological Society 146: 41,-52. Alexander, R. M., A. S. Jayes, G. M. Maloiy, and E. M. 'War.huta. 1.979. Allometry of the lirnb bones from shrews (Sorex) to elephants (Loxodonta\. Journal of Zoobgy 189: 305-314. Altman, R., G. Alarcon, D. Appelrouth, D. Bloch, D. Borenstein, K. Brandt, C. Brown, T. D. Cooke, \7. Daniels, D. Feldman, R. Gray, R. Greenu,ald, M. Hochberg, D. Howell, R. Ike, P. Kapila, D. Kaplan, \7. Koopman, S. Longlev, D. J. McShane, T. Medsger, B. Nlichel, W. Murphf', T. Osial, R. Ramsey-Goldman, B. Rothschild, and F. \folfe. 1990. Criteria for classification and reporting of osteoarthritis of the hand. Arthritis and Rheumatism 33:1601-1610. Altman, R., G. Alarcon, D. Appelrouth, D. Bloch, D. Borenstein, K.
390 .
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Brandt, C. Brown, T. D. Cooke, W. Daniels, D. Feldman, R. Grar., R. Greenwald, M. Hochberg, D. Hou.ell, R. Ike, P. Kapila, D. Kaplan, \f. Koopman, S. Longlel', D. J. McShane, T. Medsger, B. Michel, \il/. NIurphy, T. Osial, R. Ramsei'-Goldman, B. Rothschild, and F. \folfe. 1991. Criteria for classification and reportrng of osteoarthritis of the hip. Arthritis and Rheumdtism 34 505-514. Altman, R., E. Asch, D. Bloch, G. Bole, D. Borenstein, K. Brandt, 'W. Christ1., T. D. Cooke, R. Greenwald, iv{. Hochberg, D. Howell, D. Kaplan, \7. Koopman, S. Longlel', H. Mankin, D. J. McShane, T. Medsger Jr., R. Meenan, \7. Mikkelsen, R. Moskowitz, \7. Murph.v, B. Rothschild, M. Segal, L. Sokoloff, and F. \7olfe. 1986. Criteria for classification and reporting of osteoarthritis: Classification of osteoarthritis of the knee. Arthritis and Rheumatism 29: 7039-1049. Anderson, J. F., A. Hall-Martin, and D. A. Russell. 1985. Long bone circumference and weight in mammals, birds and dinosaurs. .lournal of Zoology A207: 53-61. Bakker, R. T. 1971 . Brontosaurs. ln McGraw-Hill Yearbook of Science and Te c h no I o
gy,
17 9
-7
8 1,.
New York: McGrarn-Hill.
Bertram, J. E., and A. A. Bier,vener. 1990. Differer.rtial scaling of the long bones in the terrestrial Carnivora and other rnammals. Iournal of Morphology 204: 1 57-169. Biewener, A. A. 1989. Scaling body support in mammals: Lirnb posture and muscle mechanics. Science 250: 4.5-48. Campbell, K. E., Jr., and L. Marcus. 1992. The relationship of hindlimb bone dimensions to body weight in birds. Science Series-Natural History Museum of Los Angeles Cotmty 36:39541,2. '$7. P., Jr. 1975. Sauropod habits and habitats. Paleogeographl,, Coombs, Paleoclimatology, Paleoecology 17 : 7-33. Daffneq R. H. 1978. Stress fractures: Current concepts. Skeletal Radiologl,
2:221.-229. Devas, M. B. 1967. Shin splints or stress fractures of the metacarpal bone in horses, and shin soreness, or stress fractures of the tibia in man. Journal of Bone Joint Surgery 49B: 310-313. Hartley, B. J. 1943. "Stress" or "fatigue" fractures of bone. British JournaL
of Radiology
1,6:
225-262.
Hokkanen, J.E. 1986. The size of the largest land animal. Jottrnal of Theoretical Biology I18: 49I-499. Howell, A.B. I974. Speed in Animals. New York: Hafner. Jensen, J. A. 1988. A fourth new sauropod dinosaur from the Upper Jurassic of the Colorado Plateau and sauropod bipedalism. Great Basin Naturalist 48: 121-145. Kroening, P. M., and M. L. Shelton. 7963. Stress fractures. American Journal of Roentgenology 89: 1281-1286. Mclntosh, J. S., C.A. Miles, K. C. Cloward, and I. R. Parker. 1996. A new nearly complete skeleton of Camarasattrus. Btilletin of the Gunma Museum of Natural History I: 1-87. McMahon, T. A. 1975. Allometry and biomechanics: Limb bones in adult ungulates. American Naturist 109: 547-563. Moodie, R. L. 1923. Paleopathology: An Introduction to the Study of Ancient Euidences of Disedse. Urbana: Universit,v of Illinois Press. Morris, J. M., and L. D. Blickenstaff . 1,967. Fatigue Fractures: A Clinical Sradl Springfield, I1l.: Charles C. Thomas. Myhrvold, N. P., and P.J. Currie. 1997. Supersonic sauropods? Tail dynamics in the diplodocids. Palectbiology 23 393-409.
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Orova, S., K. Puranen, and L. Ala-Ketola. 1978. Stress fractures caused b_v physical exercise. Acta Ortbopaedica Scandinauia 49: 19-27. Quirk, R. 1994. Common foot and ankle injuries in dance. Orthopaedic Clinics of North America 25: 123-133. Resnick, D. 2002. Diagnosis of Bone and Joint Disorders. Philadelphia: Saunders.
Rothschild, B. M. 1982. Rheumatologl,: A Primary Care ApproacD. New York: Yorke Medical Press. 1988. Stress fracture in a ceratopsian phalanx. .lournal of Paleontology o2:302-303.
In press. Spondylosis deformans. In F. Talavera ,
ed,.,
Orthctpedic
://www. emedicine.com. ;ew Rothschild, B. M., and L. D. Martin. 1993. Paleopathologlt: Disease in the Fossil Record London: CRC Press. Rothschild, B. M., and D. Tanke. 1992. Palaeopathology: Insigl.rts to lifestvle and health in prehistori'. Geosciences Canada 19 73-82. Rothschild, B. M., D. Tanke, and T. Ford.2001. Theropod stress tracrures and tendon avulsions as a clue to activity. In D. Tanke and K. CarpenStr r ge ry. ;owhttp
ter, eds., Mesozoic Vertebrate Life, 331-336. Bloomington: Indiana Universitv Press. Rothschild, B. M., M. Helbling II, and T. Laub. Submitted. Hyperdisease in the late Pleistocene: Validation of an early 20th century hypothesis. Annals of the Carnegie Museum. Thomasen, E. 1982. Diseases and Injuries of Ballet Dancers. Arhus, Denmark: Universiretsforlaget I Arthus. van Hall, M. E. 1982. Stress fractures of the grear toe sesamoids. American .lournal of Sports Medicine 70: 122-128. '!fang, X.-N{., and B. M. Rothschild. 1992. Multiple hereditarv osteochondroma in Oligocene Hesperocyon (Carnivora: Canidae). Journal of Vertebrate P aleontology 12: 387 -394. \(/ashington, E.L. 1978. Musculoskeletal injuries in theatrical dancers: Site frequencv and severity. American .Journal of Sports Medicine 6: 7
5-98.
'Wilson,
E. S., and F. N. Katz. 1969. Stress fracrures: An analysis of 250 consecutive cases. Radiolosy 92: 481-489.
392 .
Bruce
M. Rothschild and Raloh E. Molnar
Part Four Global Record of Sauropods
L8. Between Gondwana and Laurasia: Cretaceous Sauropods in an
Intraoceanic Carbonate Platform Faero M. Derre Vpccure
Abstract During Cretaceous times some carbonate platforms were present in the Tethyan Ocean betr,veen the Afro-Arabian continent of Gondwana and the southern margin of Laurasia. These platforms were shallow marine banks surrounded by deep sea basins, such as the present-day Great Bahama Bank, and it has been assumed that dinosaurs could not live there. However, dinosaur evidence has been recently discovered in three of these platforms, known as periAdriatic carbonate platforms. The Adriatic-Dinaric Platform (Italy, Slovenia, and Croatia) has yielded sauropod footprints from the Hauterivian, sauropod bones and a footprint from the upper Hauterivian-lower Barremian, and sauropod footprints from the upper Albian and upper Cenomanian. The presence of those large terrestrial animals suggests that a part of the carbonate platform had to be emergent and able to support the dinosaurs with food and fresh water. This occurrence in the upper Hauterivian-lower Barremian of a sauropod association characteristic of Early Cretaceous times,
with prevailing Titanosauriformes and rarer Diplodocoidea, points against a separation of the platform from continental areas, as is 395
often shown in paleogeographical reconstructions. The Gondwanan affinity of benthic foraminifers and some paleogeographical constraints suggest a Late Jurassic-earliest Cretaceous connection with the Afro-Arabian continent. The small size of late Albian and late Cenomanian sauropods, as well as other dinosaurs living on the platform after the Barremian, could be related to the definitive isolation from the continent) caused by the opening of the Eastern Mediterranean oceanic basin between Afro-Arabia and the olatform during the Aptian. The small sauropods could be iniular dwarfs, similar to those from the Maastrichtian of Transylvania and other Late Cretaceous sites of the European Archipelago. From the late Santonian on, plant-eating dinosaurs are represented by hadrosaurians, whereas no sauropod remains are found to date. These hadrosaurians were also unusually small and oossiblv insular dwarfs. Introduction The systematic study of dinosaur sites on the Istrian Peninsula (northwest Croatia) by a team from the Museo Paleontologico of Monfalcone (Italy), and recent discoveries in Italy and Slovenia, have surprisingly shown that the Mesozoic carbonate platform outcroppings there contain relatively abundant and diversified dinosaur evidence (Fig. 18.1). The fossil record of Cretaceous sauropods is not as rich as in other regions of the world. It has a limited phylogenetic significance, but important paleoenvironmental and paleogeographic implications. Limited information from the small size of the sample could affect interpretation, so caution is due. However, as Norman (1985, 124) says, "to attempt to answer these questions [about the biogeographic pattern of hadrosaurs], we need to propose new rheories. These theories can be 'tested' by further investigation of the fossils in order to try to either 'prove' or 'disprove' rhem. In this way we hope gradually to get closer to the real explanation." The hypotheses presented below are based on the available data that need confirmation and can be considered as a basis for further research.
Institutional abbreuiations. MPCM-Museo Paleontologico Cittadino, Monfalcone, Italy; and Nos lG-Institute of Geology, Zagreb, Croatia. MPCM-V (Museo Paleontologico Cittadino di Monfalcone, vertebrate collection) is a provisional number given to the specimens under preparation at the museum, which were returned to the authorities of the Municipality of BaleA/alle, Croaria, who did not number them. \X/N-V means "vertebrate remain without number" and refers to the bones under the care of the Municipality of Bale/Valle, which had no official number when studied. Terminology. The terms "continent" and "continental" are used in the geographical meaning of "wide emergent area," as opposed to "island," a smaller emergent area. An island is "emergent land completely surrounded by sea (or water in general) and with 396 . Fabio M. Dalla
Vecchia
Fig. 18.1. Dinosaur sites of the Adriatic-Dinaric Carbonate Platform. (1) Fantazija Quarry near Rouinij/Rouignct, Berriasian (lsauropod footprints). (2) Cape Gustinja, early Hauteriuian (sauropod and large theropod footprints). (3) Sarone, Cansiglio Plateau, late Hauteriuian-earh,Barremian (sauropod and large theropod footprints). (4) Bale/Valle, late Hauteriuidn-early Barremian (sauropod and rarer theropod bones). (5) Main Brijuni/Brioni lsland, late Barremian (large theropod footprints),late Albian (theropod and rare ornithopod footprints). (6) Mirna/Quieto riuer moutb, Iate Albian (theropod footprints). (7) Solaris site, Iate Albian (sauropod and theropod footprints), (8) PuntiTela/Puntesella, Iate Albian (tberopod footprints). (9) Lourecica/S. Lorenzo di Daila, Iate Cenomanian (theropod footprints). (10) Karigador/Carigador, Iate Cenomdnian (saurop od footpruus 1.
Between Gondwana and Laurasia
.
397
an extension decidedly more reduced than that of the smailest continent." There is not a rigorous separation between a "large island"
and a "small continent."
The Apulia microplate (or Promontory) is a large tectonic structure which should not be confused with the Apulia carbonate platform occurring on this microplate: the,v both take their names from the Latin word " Apulia," the name of the present-day Puglia region of southern Italy. The term "trackwa-y" indicates a sequence of footprints, and "track" refers to a single footprint. The Istrian Pensinsula is part of the Republic of Croatia, but it is bilingual (Croatian and Italian); therefore, two names are often reported for each locality. The carbonate plateau, which occurs partly in Slovenia and partly in Italy, is named "Carso" in Italian and "Kras" in Slovenian, often reported in the literature as "Karst." Paleogeographic Setting Tethys was a seaway, which, during its maximum longitudinal extent in the Cretaceous, ertended from Timor on the east to the Caribbean region on the west. It separated the Laurasiatic/Eurasiatic Plate from the Afro-Arabian one. The centrai-western section of Tethys was a zone where wide carbonate platforms developed during Mesozoic times. Some of the platforms were later fused to the southern European margin by the coilision of the Afro-Arabian
Plate against the Eurasiatic Plate and the consequent Alpine orogeny. Three main Cretaceous platforms occur in the periAdriatic region of Italy, Slovenia, and Croatia: the Apulia Platform, the Lazio-Abruzzi-Campania Platform (or Apennine carbonate platform), and the Adriatic-Dinaric Platform (Eberli et a|. 1993; Dercourt et al. 1993, 2000) (Fig. 18.2). The Lazto-AbruzziCampania Platform may have been divided into two platforms: the Lazio-Abruzzi Platform and the Apennine Platform (Yilmaz et al. 7996). D'Argenio (1974) includes outcrops in Sicily (Panormide, Iblei Mounts) and in the Hellenides (Greece) among the periAdriatic platforms. Those piatforms were areas of nearly exclusive carbonate sedimentation from the Late Triassic to the end of the Cretaceous (Zappaterra 1,990). The Adriatic-Dinaric Platform has the most abundant evidence of dinosaurs. It crops out mainly in northeastern Italy, Slovenia,
Croatia, western Bosnia, and western Montenegro (Fig. 18.2). It was a north-south elongated structure and during the JurassicCretaceous -'vas bordered to the west, north, and east by deep marine, basinal areas (e.g., Ionian Basin, Adriatic Basin, Belluno Trough, Tolmin Trough, Bosnian Basin, etc.) (see Cati et al. 1989; Zappaterra 1990). The paleogeographic-paleoenvironmental maps of Dercourt et alr. (1993; 2000) show the Cretaceous AdriaticDinaric Platform (parts of which are labeled there as "Karst Platform," "Dalmatia," and "Friuli") as the northern part of a larger,
398 . Fabio M. Dalla Vecchia
EUROPE
narrow, elongated, and shallow marine paleogeographic unit with carbonate sedimentation only. This unit includes on the southeast the present regions of Gavrovo and Tripolitza (in Greece) and areas now found in Turkey (Fig 18.3). The peri-Adriatic platforms originated as separate geographic units during the Early Jurassic rifting and breakup of a wide pericontinental carbonate platform extending along both the northern
(Laurasiatic) and southern (Gondwanan) margins of western Tethys. According to Bulot et al. (2000), during the early Hauterivian the carbonate platforms were isolated by deep sea from the Afro-Arabian continent and from the emergent areas of western Europe (a wide land extended from the Iberian Massif to the Bohemian Massif through the London-Brabant Massif). According this paleogeographic reconstruction, the northern termination of the Adriatic-Dinaric Platform (present-day northeastern Italy and Istria) was isolated in the middle of the Tethys between the two continental masses. Horvever, the dinosaur record suggests a land connection between the platform and a continent (Fig. 18.3A). The early Aptian paleogeographic maps of Masse (2000) and Masse et al. (2000) show that the Eastern Mediterranean oceanic basin formed between the Afro-Arabian continent and the Apulia and Adriatic-Dinaric Platforms (Fig. 18.3B). The situation persisted
Fig. 18.2. The current position th e p er i- Adr
iatic
of
car b on dte
platforms along the southern margin of Europe. Abbreuidtions: A = Apulidn Carbonate Platfctrm;
AD - Adriatic-Dinaric Cdrbctnate Platform: LAC = Lazio-AhruzziCamp ania C a r b on ate
P
I
atfor
m;
platforms of Sicily. Based on D'Argenio Sic = carbonate
(1974), redratun and modified.
during the late Cenomanian (Philip et al. 2000a) and the late Maastrichtian (Philip et al. 2000b), when the Adriatic-Dinaric Platform
moved closer
to a relatively large, deveioping,
Austro-Tran-
svlvanian island. but still remained seDarate from it. Between Gondwana and Laurasia
.
399
Fig. 18.3. (A) Simplified paleogeographic ffidp of centr.ll-western Tethys based on the early Titbonian (141-139 myal map b)'Thierly (2000), modified and redratan. According to dinosaur distribution, it is a plausible reconstruction of the geogrdphicltosition of the platforms during Cretaceous pre-Aptian times. Dinosaurs from northern Africa could colonize the emergent pdrts of the Adriatic-Dinaric Platform along the route euidenced by arrous. (B) Central-western Tethys during the early Aptian (114-112 mya) based on Masse (2000) modified and redrawn. Oceanic fractures dre leported for the Eastern Mediterranean Ocean and its eastern continuation, the Piedmont-Ligurian Ocean, and the Central Atlantic. Light gray = land; gray = epicontinentdl sea; dark grd.y = ocednic basins. Asterisk indicates the position of lstria. Abbreuiations: A = Apulia Carbonate Platform; AD = Adriatic-Dinaric Carbonate Platfornt; AM = Armorican Massif;
BM=BohemianMassif;Cl=Centrallran;E=Egypt;ET=EastentTaurtts(Turkey);G=Gaurouo;IM=Ibenan
Meseta; LAC = Lazio-Abruzzi-Campania Carbonate Platfonn; Me = Menderes (Turkej'); TN = Terranoua; US =
Ukrainian Shield.
400 . Fabio M. Dalla
Vecchia
According to Eberli et aL. (1993, 216-217), the peri-Adriatic platforms are "analogous to rhe Bahamas archipelago, not only in their carbonate facies, platform size and shape, and rate of subsidence.... but also in the internal architecture"; they "were situated in the equatorial belt, between 10'and 30'north paleolatitude" during the Early Cretaceous and "migrated during the Late Cretaceous northward across 30' north. . . . Humid intervals are indicated by extensive bauxite horizons, particularly in the middle Cretaceous (Aptian-Cenomanian)." These extensive bauxite horizons indicate local emersion of the Apennine and Apulia platforms, whereas in the northern part of the Adriatic-Dinaric Platform only traces are found in the middle-upper Cenomanian. Sauropods of the Adriatic-Dinaric Platform The sauropodan record of the Adriatic-Dinaric Platform has been described in detail in several papers by me, which rhe reader should refer to for further information. Berriasian. Some sedimentary structures exposed in cross section on the quarry wall at the Fantazija Quarrn near Rovinij/Rovigno, Istria (northwestern Croatia), have been identified as sauropod footprints by Lockley et al. (1994,240) on the basis of Tisljar et al. (1983, fig.4), who, however, reported them as load casts. I have seen those structures in person and, in my opinion, their identification as sauropod footprints is questionable, because there is no organization in a trackway that can be recognized, nor is there any trace of pedal or manual structures or any other morphological feature of a sauropod footprint. Early Hauteriuian. More plausible sauropodan footprints are found in the Cape Gustinya localitn sourhwestern Istria (Dalla Vec chia et al. 2000b). The footprint-bearing secrion is dated to the early Hauterivian based on foraminifers and algae biostratigraphy. A11 footprints are still more or less filled in by the overlying layer, with some completely covered. The best-preserved specimens are triangular-elongated or kidney-shaped, resembling pedal and manuai sauropod prints, respectively. The pedal prints range in length from 40 to 50 cm, and oniy one is smaller (27 cm in length). One kidney-shaped footprint is 28 cm wide and 14 cm long. Another surface preserves numerous circular, oval, triangular, and semicircular depressions, often with clear expulsion rims all around, never organized in trackways. The t'uvo best pedal prints are 55 and 52 cm iong. Some "dinoturbated" levels, which could have been produced by sauropod activity, are also found in the site. Late Hauteriuian-Early Bdrremian. An isolated sauropodan manual print was found in a block of limestone from the the Calcare del Celiina Forrnation of the Cansiglio Plateau near Sarone (Pordenone Province, northeastern Italy) (Dalla Vecchia 1999a).Its age is late Hauterivian-early Barremian, based on the presence of the benthic foraminifer Cdmpanellula capuensis in the block itself as in the quarry section. The environment of deposition was a tidal Between Gondwana and Laurasia
.
401
C
lr lli
I
crn 2{.}
Fig. 18.4. Manual skeletons of sauropods and the sauropodan manual print from the ultper H aut eriu ian- I ow e r B arr em ian o f the Cansiglio Plateau, northeast Italy. (A) Camatasaurusl tuith a large ungual on digit I; Opisthocoelicaudia. (B) Brachiosaurus brancai, srll/ retaining proxinul phaldnges and a reduced, but functional, ungual on digit 1. (C) Opisthocoelicaudia, witbout phalanges dnd with flat distal metacarpals uith out condyles. (D) sauropodan manual print. I-V = digits and marks of digits l-V. A-C after Salgado et al. (1997), redraun; D after Dalla Vecchia
(1
999a).
402 . Fabio lvl. Dalla
Vecchia
I
tl cnr
cnr
flat in an inner carbonate platform setting. The present-day Cansiglio Plateau was the northern termination of the Adriatic-Dinaric Platform. The footprint of a large theropod is preserved close to the sauropod footprint (Dalla Vecchia and Venturini 1995), and both specimens are positive reliefs. The sauropod footprint is 30.5 cm Iong and 31 cm wide and with a low relief (2-2.5 cm). It is as long as it is wide and shaped like a double crescent, consistent with the morphology of undeformed sauropodan manual prints (Farlow et a|. 1989; Thulborn, 1990) (Fig. 18.4D). Prints of digits II-IV are rounded, as is one of the outer digits, presumably digit V. The print of the other digit, presumably digit I, is triangular and short, like the print that could have been impressed by digit I of Brachiosaurus brancai (Fig. 18.aB). However, the presence of another low, narrow, and elongated mark (dotted lines in Fig. 18.4D) could indicate that the ungual was actually larger, as in Camardsaurus and the diplodocoids (Fig. 18.4A). A deposit rich in dinosaur bones was discovered at the sea bottom along the coast of southwestern Isrria, in the locality Kolone/Colonne near the town of Bale/Valle (Boscarolli et al. 7993). The specimens are preserved in lacustrine limestone formed in an emergent carbonate platform setting (Tunis et al. 1994; Dini et al. 1998). The presence of Campanelluld capuensis just below the bone-bearing beds, and the micropaleontology of the overlaying section exposed in the nearby locality of Barbariga, suggest a Iate Hauterivian-early Barremian age for the bones (Tunis et al. 7994;Drni et ai. 1998). Only the remains exposed ar the sea bottom by marine erosion were collected, mainiy by the site discoverer, Dario Boscarolli. The sample is small, and most of the 200 recovered specimens are worn fragments of bone. The most complete, best-preserved bones are still inside the limestone at the sea bottom, awaiting collection. A tooth crown 12.5 mm long and an ungual phalanx less than 9 mm long, found by dissolving with formic acid the rocky matrix containing the holotype vertebra of the sauropod Histriasaurus boscarollii, represent small to medium-sized theropods (Dalla Vecchia 1998b; 2001.a,33). A yet undescribed caudal vertebra could belong to a large theropod. All other identifiable bones belong to
sauropods (some more or less complete cervical, dorsal, and caudal vertebrael many fragments of vertebrae; fragments of cervical ribs; an incomplete femur; an incomplete tibia; and man,v fragmentary large limb bones; Fig. 18.5). Unfortunately. most of the specimens
are incomplete, and the presacral vertebrae are often crushed. However, the preservation in limestone allowed us to completely free the bones from the matrix by a combination of mechanical and chemical methods. The bones were collected randomly on the sea bottom, therefore they were not part of a single skeleton and most probably represent different individuals, as testified by the different sizes and morphologies. In the overall shape and proportions, the pattern of pleurocoels, and the inner structure of the centrum, a 30-cm-long cervical centrum (MPCM-V2, Figs. 18.5C, 18.6D-E) shows some resemblance to the vertebrae from the Barremian Wessex Formation of southern England named "Chondrosteosdurus gigas" by Owen (1.876). According to Paul Upchurch (pers. comm., 1.998) Chondrosteosaurus gigas is most probably a titanosauriform (Brachiosaurus + Titanosauria). The internal structure is highly cellular,
with the condylar region showing a honeycomb-like pattern in cross section (Fig. 18.6F) that represents small, longitudinally elongated, tubular cells. All other parts of the centrum and the base of neural arch where the inner structure is visible are made of small irregular vacuities and thin bony septa (see Dalla Vecchia 1998a, fig. 4; 1.999b, figs. 1.2-1.6,20-21). This kind of cellular inner structure
is reported with different names in the literature: large cancelli (Owen 1876), large-celled cancellous tissue (Hulke 1.879), cavernous osseous tissue (Salgado et ai. 7997), camellate structure (Britt 1997), spongy bone ('S7ilson and Sereno 1998; Wilson2002), cancellous tissue (Sanz et aL. 1999), and pneumatic camellae (Wedel et al. 2000b). A complete cervical (\(/N-V1) has a tubular elongated centrum
35 cm long (length:height ratio = 7), with small pleurocoels, and a relatively low, laminar neural arch having a vertically oriented, short, and narrow undivided spine (Figs. 18.5A-B, 18.6A-C). ks overall morphology is reminiscent of the anterior cen'icals of Brachiosaurus brancai (Janensch 1950, fig. 1, 5,20-37, pl. 1, figs. 1-8). Cervical centra reaching a maximum of seven times as long as they are deep is a brachiosaurid synapomorphy according to V/ilson and Sereno (1998,21). The internal structure of WN-V1 is cellular, as seen where the centrum is damaged (see Dalla Vecchia 1999b, figs.2,4) and also in the posterior cross section of the preceding cervical centrum. Like MPCM-V2, the cells are elongated anteroposteriorly toward the condyle, but they seem to be less regular than in MPCM-V2. The extensive presence of small cells separated by thin bony septa is a feature common to all the more or less complete presacral centra and many fragments of centra found in the site, with the lone exception, as far as it can be seen, of the posterior dorsal of Histridsaurus boscarollii. Also, where the neural arch is preserved Between Gondwana and Laurasia
.
403
404 . Fabio M. Dalla
Vecchia
in those vertebrae, the laminae are not reduced. This combination of features corresponds to the definition of the camellate vertebral type by'Wedel et al. (2000b, 360). The taxonomic significance of the cellular tissue in rhe cenrra of presacral vertebrae has been considered in different wa-n*s in the last few years. It was once reputed to be a diagnostic character of titanosaurids (e.g., Poweil 1986; Astibia et al. 1990), then of unclear phylogenetic relevance (Salgado et al. 7997), and diagnostic of the clade Somphospondyli (Euhelopas + Titanosauria) by Wilson and Sereno (1998). It has been considered synapomorphic of Titanosauria (sensu Sanz et al. 1999.252). but it is also found irr Andesaurus, which Sanz et al. (1999) placed outside Titanosauria, thus, they suggest that the character "could eventually be diagnostic of a more inclusive clade than Titanosauria." The spongy presacral bone texture is considered a shared derived character of Titanosauriformes (Brachiosaurus + Somphospondvli) by Wilson (2002), but "presacral bone spongy" is also an independently evolved autapomorphy of Mamenchisaurus. Wedel et al. (2000a, 112-113) observed "pneumatic camellae" also in cotyles and condyles of the posterior cervicals of Diplodocus and conclude that "camellate internal structure is homoplastic in sauropods anc evolved in long-necked lineages as a means of reducing weight." The Istrian cervicals are small by sauropod standards and appear mature (the neural arch is fused to the centrum, the vertebra is well Flg. 18.-f. (opposite page) ossified), therefore they belong to relatively small-sized, non- Sauropod bones from tbe late juvenile individuals and their cellular strucrure is not strictll' related Ha u cri uidn-aa rll Barrun ia n si e to large size. Furthermore, dorsal centra are camellate in Ti- of Bale/Yalle, lstria. (A) \I/N-V7, tanosauriformes (sensu \7ilson 2002), and obviously this has no re- ceruical uertebra, left lateral uietu. fB) If/N-V/, right lateral uiew. (C) lation with neck elongation. According to \X/edel et al. (2000b), MPCM-V2, ceruical centunl, vertebrae of the semicamellate or camellate type are found in some rigbt lateral uieu. (D) Shaft Titanosauriformes (Brachiosauruzs has sernicamellate cervicals) fragments of ceruical ribs. (E) and, convergently, in the more primitive Mamenchisaurws. Thus MP CM-V 1, anterior dorsal Vedel et al. (2000b) consider semicamellate and camellate verte- uertebra, anterior uiew. (F) posterior uiew. (G) brae a peculiarity of Titanosauriformes and Mamenchisaurus. MPCM-VI, MPCM-V3, partial neural arch of Somphospondylian titanosauriforms have vertebrae of the sorn- a dorsal t'utcl,r,t, anlcriur t iew. phospondylous type, with a camellate internal strucrure, arch lam- (H) WN-V6, posterk:r dorsal inae reduced, and a neural spine with inflated appearance (rWedel et uertebra, holo4,yte of al. 2000b). Wilson (2002) also considers "reduced cervical arch Histriasaurus boscarollii, posterior (I) iamination" a synapomorphy of Somphospondyli. Thus, S7N-V1 anterior uiew. \I/N-V3, caudal uertebra, right belongs to a more basal titanosauriform than Somphospondyli. lateral uiew. (.1)Ncts-lc1, midSeveral rod-like fragments of the shafts of filiform cervical ribs caudal uertebra, right lateral uiew. (Fig. 18.5D) have been collected, and some segments up to over (K) IVN-V,1, mid-cattdal uertebra, one meter long are exposed on the sea floor (Dalla Vecchia 1998a; left lateral t,iew. (L) MPCM-V9, neural spine of a caudal uertehra, Boscarolli and Dalla Vecchia 1999\. Cervical ribs extendine backanterior uiew. (M) Nos-|G2, distal ward two times or more the centrum leneth are Dresenr in rhe neck part of a iemur, medial uieq tibial of Camardsaurus and in Brdcbic,sauius, Euhelopus, Mamen- cond1,le. (N) MP CM-V1 6, chisaurws, and Sauroposeidon. They are found also associated with pr()xit1ldl part oi a ?tibia, titanosaur bones in the Upper Cretaceous of Brazil (pers. obs.). On posterolateral uiew. The scale bdr is in certtineters. the other hand, according to Mclntosh (1990a,1990b1, short cervical ribs are a diagnostic feature of Diplodocidae, and following I
t
?
Betrveen Gondwana and Laurasia
.
405
C SPZL
ASPZ
PZ
ffPZlPzt:HL
10 cm
Fig. 18.6. Ceruical uertebrae, ldte Hauteriuian-edrly Barremian, Bale/Valle, Istria. (A) WN-VI, Ieft lateral uieu. (B) \YNY1, pattern of pleurocoels. (C) \VN-VI, posterior uiew. (D) MPCM-V2, rigbt lateral uiew. (E) MPCM-V2, dorsal uiew. (F) MPCM-V2, the "cellular" structure in the condylar region (the uertebra is upside down and shou,s the anterouentral uieu). A-E after Dalla Yecchid, 1998d, modified. Abbreuiations: APL = anterior pleurocoel; ASPZL = additional suprdpostzygdpophyseal lamina; CO = cond),le; DP = diapopbysls; HL = horizontal lamina ( = diaPoprezygapophysedl lamina, diapopostzlgdpophyseal lamina of Wilson 1999); IPDL = infrapostdiapophyseal lamina; IPZL = infrdpostzygdpophyseal lamina; ITPZ = intlapostzygapophyseal lamina; LPL = louer pleurocoel; NA = neural arch; NC = neural cdn.ll; NS = neurd.l spine; PL = pleurocoel; PP = parapophysls; PPL = posterior pleurocoel; PR -prezygapophysis; PZ = postzyg.tpoph.\sis; SPRL = supraprczygdpoPhysedl lamina ( = spinoprezygapophyseal lamina of 'Wilson 1999); SPZL suplapostzj'gapophyseal lamina ( spinopostztgdpopbyseal lamina of \Yilson 1999). = =
406 . Fabio M. Dalla
Vecchia
'Wilson
'Wilson and Sereno (1998) and (2002) cervical ribs shorter than the respective cenrra is the only synapomorphy of Diplodocoidea. In no cases are the Istrian remains associated to the corresponding vertebrae, but their filiform aspect resembles that of the long cervical ribs of Brachiosaurzzs (Janensch 1950) and probably they were longer than their respective centra. A very small vertebra preserves most of the centrum and part of the neural arch (Figs. 18.sE-R 18.7A-C) lacking a hypospenehypantrum complex, and was identified as a possible anterior dorsal (Dalla Vecchia 1998a). The centrum, only 80 mm wide and 55 mm high, has a cellular internal structure and a large lateral pleurocoel (see Dalla Vecchia I998a, fig. 8, and Dalla Vecchia I999b, figs. 31-33, 36-37). Small cavities are present in the postzygapophysis (Dalla Vecchia 1999b, fig.38) and a cellular structure is found also in the neural arch (Dalla Vecchia 1999b, figs. 31-33, 35-36). The latter is made of several extremely thin laminae (laminae definitions in figs. 7 and 9 are those in Dalla Vecchia 1998a, thus they differ partly from the subsequent laminae denomination by \Tilson 1999) and it is strongly crushed. The neural arch is very high: in the preserved part (the neural spine is missing) the distance between the base of the postzygapophysis and the top of the cenrrum is 1.83 times the centrum height. It has very long and parallel infrapostzygapophyseal laminae, and prespinal and postspinal laminae (actuallS the rib-like remnants of them). There is no evidence of immaturity: the neural arch is fused to the cenrrum and the vertebra is
well ossified. According to the sauropod phylogeny by \Tilson
(2002) it is a titanosauriform because of the "spongy bone." As far as I know, this vertebra differs from other sauropod dorsal vertebrae and possibly belongs ro a still-unknown taxon. If it is actually a sauropod (the only other alternative seems to be an aberrant theropod), it represents a rather smail-sized taxon. A partial neural arch of a dorsal vertebra (MPCM-V3). unfortunately poorly preserved, is 24 cm high (Figs. 18.5G, 18.7D-H). k
has a very laminar structure and presents the rib-like traces of prespinal and postspinal laminae, both reaching the basal part of the neural spine. The robust zygapophyses show the development of internal vacuities, which are also found in the ventral oart of the hyposphene and the core of the neural arch has a cellular inrernal structure (see Dalla Vecchia 1998a, fig. 11E-F). The base of the neural spine is narrow in both lateral and anteroposterior view, but it is partly crushed and weathered. The specimen probably belongs to a relatively large titanosauriform. The opisthocoelous and short centrum of a larse vertebra (probably an anterior dorsal; Dalla Vecchia 2001a) has a posrerior width of 34 cm (Fig. 18.8A-B). The strongly crushed neural arch is made of many thin laminae and struts (Fig. 18.8A-B), and the centrum has the cellular inner structure (see Dalla Vecchia 2001a, figs. 4, B-!0; Fig. 18.8C-D) suggesting it belongs to a large titanosauriform.
Between Gondwana and Laurasia
.
407
PRSPL ^^^,
LlPZL
lPRL
IPDRL'
PP. IPLLb SIPRL
2
ar,
5cm
C
Fig. 18.7. Dr:rsal uertebrae, late Hdrfteriuian-early Barremian, Bdle/Yalle, Istria. (A) MPCM-V1, anterior uietu. (B) ctf a posterior dorsal uertebra, anterior uiew. (E) MPCM-V3, posterior uieu,. (F) MPCM-V3, right lateral uieu,. (G) MPCM-V3, dorsal uieu. (H) MPCM-V3, uentral uiew. After Dalla Vecchid (1998a), modified. Abbreuiations: AS = dnterior strLtcture betu,een tbe prezygapophl'ses; Has = drticular sLrrface for the hl,posphene; HPN = h1'posphene; HYP = hypantrunt; IDL = infradiapophyseal lamind ( = posterior certtrodiapophy,seal lamina of \Yilson, 1999); IHPNL = infrab,posphenal lamina: IPDRI = infraprediapophyseal lamintt; IPPL = infrdparapoph)'sedl latnina; IPLLa = dnteri.)r infraparapctphyseal lamina; IPLLb = l)osterior infrdparapophyseal lamina; IPRL = infraprezygapophyseal lamind; LIPPL = ldteral infraparapophyseal lumind: I-IPZL = lateral infrapostzygapophl'seal lamina; PRL = prez),gdpoph),seal lamind; PRSPL = prespinal lantina; PSPL = postspinal lamina; SDL = suprddidpopbyseal lamina ( = spinodiapophyseal lamina of 'Wilson 19c)9); SIPRL = strbinfraPrezj,gapophyseal lamina. For other abbreuiatiorts, see Figure 18.6.
MPCM-VI, posterior uiew. (C) MPCM-V1, right lateral uiew. (D) MPCM-V3, partial neural drch
408 . Fabio M. Dalla
Vecchia
Another evidence of relatively large individuals in the sample is the distal end of a femur (Dalla Vecchia 7998a; Fig. 18.5M).
A nearly complete posterior dorsal vertebra (WN-V6, Figs. 18.5H, 18.9A-B) is the holotype of Histriascturus boscdrollii (Dalla Vecchia I99Ba). The specimen has been prepared in a way that only the posterior and right lateral sides are visible. The centrum, unlike the other presacrals from the site, does not seem to have a cellular structure. It has a posterior articular face that is not wider than it is high, and a large ovai pleurocoel occupies most of the centrum length (Dalla Vecchia 1999b, fig. a7). The neural arch is tall (the height of the only partiaily preserved neural arch is 2.85 times the dorsoventral centrum height) and laminar. The neural spine, although incomplete, appears to widen roward the apical parr and is made of a few laminae meeting perpendicularly to each other. There is a well-developed hyposphene. The pedicel of the neural
arch divides distally into two laminae. One, thicker and strut-like, corresponding to the centropostzygapophyseal lamina of \Tilson
Flg. 18.8. wN-VZ, large ?anterkr dorsal t,ertebra of d Titanosauriform sauropod, late H aut er i u i dn-edr 11, B a r r e nt i trn, Btle/Vallc, lstria. 1A1 Arrterior uieu'; note the irtner uacuities (bldckl; in u,hite is the original condl'lar surface, *'hereas the inclined lines indicdte tbe worn pdrt of the condyLtr su'face. (B) Posterior uietu. (C) Ventrdl uew; note the "cellttlar" strttcture of the cetirunl antl the collapsed condl,lar part. (D) Particular of the condylar snrface, shou.,ing the largest uacuities dnd the collapsed "cellular" strLrctlre of the crushed condt'Le. Abbreuidtiort: na =
neu'al drcb.
(1999), reaches the hyposphene, the other, sheet-like, extends along the ventroposterior margin of the transverse process toward the diapophysis and corresponds to the posterior centrodiapophyseal Betrveen Gondwana ar-rd Laurasia
.
409
D
$
y't; ISPZT
10 cm
Fig. 1 8.9. Histriasaurus
boscarollii, I ate H aut er iu ian-e ar ly B arremian, B ale/Valle, I stria. ( A) WN-V6, a posterior dorsal ue r I eh ra, h olotl'pe. ld t cropos! er ior uiew aftcr comPlcte PreParatiott. /B) !f/N-V6, posterior uiew. (C) Posterior dorsal uertebra of Rebbachisaurus garasbae, lalt'roposteriur uicw. tDl Posteriur uieu'. C and D are based ott photogrdphs and fig. 39A in Bon,:part e 1 l'ttt9 t. Ahhreuiatiorrs: ISPZL = inner | p rd p o st.\' ga p o p h1'sca I Ia m i n a = ne dial spi nop ostzy gaPoP hy seal lamina of \Yilson 1999);
s| 1
OSPZL = outer su p r.tp o stzy gd2 oP hy
se
al lamnn
( = lateral spinopostzygdpophyseal .Wilson 1999). For other lamina of ab br euiations, see F igures 18 .6-18 .7.
'Wilson (1999) (infradiapophyseal lamina of Dalla Veclamina of chia 1998a). Three laminae start from the postzygapophysis. The more robust and medial of the three (the spinopostzygodiapophyseal lamina of Wilson L999) is directed upward and medially, converging with that starting from the other postzygapophysis to form a relatively thin postspinal lamina' Thus a deep, axially elongated' and drop-shaped postspinous fossa (sezsz Wilson 7999) is created at the base of the neural spine. The most lateral and thinner of the three (horizontal lamina in Dalla Vecchia 1998a; postzygodiapophyseal lamina in Wilson 7999) extends along the transverse process. Between those two, directed upward and perpendicular to the supradiapophyseal lamina (spinodiapophyseal lamina of \7il\on 1999), is a lamina referred as the "outer suprapo\tzygapophyseal lamina" in Dalla Vecchia (1998a) and as the lateral spino'Wilson (1'999). The transverse postzygapophyseal lamina by Iamina making the core of the neural spine is probably an extension of the supradiapophyseal lamina (spinodiapophyseal lamina of Wilson 1999). All those laminae outline deep triangular depressions (fossae) in the neural arch. That vertebra resembles the posterior dorsal vertebrae of Gondwanan diplodocoids, with high and laminar neural spines and arches and inclined transverse processes (Dalla Vecchia 1998a). Histriasawrus boscarollil shares with the rebbachisaurid diplodocoid Rebbachisaurus gdrdsbae a relatively elongate posterior dorsal centrum with a wide oval pleurocoel, and a posterior articular face not wider than it is high; a tall neural arch, at least three
times the dorsoventral centrum height, and high below the zygapophyses; long transverse processes projecting dorsolaterallv
410 . Fabio M. Dalla Vecchia
about 45'; a light neurai spine made of thin laminae meering ar 90o to each other; thin, plate-like posterior centrodiapophyseal (IDL in
Fig. 18.9B-D) and spinodiapophyseal laminae (SDL in
Fig.
18.9B-D); spinopostzygapophyseal laminae that converge and fuse to form a postspinal lamina; deep triangular fossae at the base of the neural spine and in the lateral side of the neural arch below the transverse process; a neural spine wider transversely than anteroposteriorly, which broadens dorsally in anteroposrerior view, so that the width of the upper porrion is noticeably grearer than the width at the base of the spine (Fig. 18.9). The lateral margins of the spine in anteroposterior view are neither paraliel nor concave, but instead they are straight and slightly flaring upward (or converging ventrally). This corresponds to the "petaloid" shape of \Tilson (2002).In Rebbachiscturus gardsbae, and probably also in Histriclsdurus boscarollii (though the middle-distal part of the neural spine is not preserved), this flaring is gradually upward and does not occur iust at the top of the spine. Most of the features shared by Histriasaurus and Rebbdchisaurus underline an overall similarity and taken singularly are not unique shared features of the two taxa. The only rebbachisaurid character tn Histriasaurus accordtng ro the eight characters synapomorphic of the clade Rebbachisaurtdae (Rebbacbisdurus
+ Rayososaunrs + I,{igersaurus) in Nfilson (2002) is the "petalshaped" posterior dorsal neural spines. This feature needs to be confirmed by a complete spine. "Petaloid" posterior dorsal neural spines are also a synapomorphy of Dicraeosauridae (\Wilson 2002, 270, character 8). "Neural arch deep below zygapophyses" and "thin, plateJike posterior centrodiapophyseal and spinodiapophyseal laminae" are autapomorphic characters of Rebbachisaurus garasbae (\X/ilson 2002) that are shared by Histriasatrus boscarollii. It is nor possible to check the holotype of the Istrian raxon for the other six autapomorphic characters of Rebbachisaurus garasbae of \il/ilson (2002), due to its incomplete preservation and type of preparation. Thus, confirmation of a stricter affinity with Rebbacbisaurus needs to be based on material that is more comolete. There are three more or less incomplete anterior caudal vertebrae in the sample (Figs. 18.5I, 18.10A-D, E-F). Both articular faces of the centrum of the most complete specimen (Figs. 18.5I, 18.10A-D) are only slightly concave; the anterior is more concave than the posterior that is nearly flat. The posterior face in MPCMV15 is also nearly flat. The pleurapophyses (caudal ribs) are not wing-like and are lateroposteriorly directed in all specimens, as in the caudals of Brachiosaurus brancdl. The neural arch is displaced toward the anrerior half of rhe cenrrum in at leasr one soecimen {Figs. | 8.51. 18. l0A r. There are neirher pleurocoels nor a venrral sulcus in the centra.
There are also two mid-caudals (Figs. 18.5J-K, 18.10G-K) with moderately elongated, spool-like centra without a ventral sulcus, and with the neural arch displaced toward the anterior half of the centrum. The articular faces of the centrum are sliehtly conBetween Gondwana and Laurasia
.
411
G
o' n'-
-1.*
-
-.
!.\ \],.
1)
--
_{ =>
Fig.18.10. Cattdal uertebrae late H du t er iu ian-e ar
11' B
arr e nti an,
Bale/Valle, Istrid. (A) WN-VJ, anterior uertebra, right lateral uieu. (B) \{N-V.1, dorsal uieu,. (C)
WN-V3, anterior uieu. (D) \YN\'.3, posterior t,ieut. (E) MPCMV11, pdrtial anterior uertebra, anterior uieu,. (F) MPCM-VI1, left lateral uiew. (G) Nos-1Gl. mid- caudal uert eb ra, ri ght I ate ral t'icu. 1H) Nus-/C l. rnl(ri, )r uicu'. /I/ Nos-IC1, posterior uiew. (l) \VN-I,',1, mid-caudal, I eft lateral
uieu. (K) WN-V.1, dorsal uieu,. After Dalla Vecchia (1998a), ntodified. Abbreuiations: CD =
caudal rib (plettrdpopbysisl; lD = ldteral depression; LK = lateral knob. For other abbreuiations see ligures 18.6-18.7.
412 . Fabio M. Dalla
Vecchia
cave; the posterior face is more depressed than the anterior. These
of Brachiosdurus brancai (Janensch 1950, pls. II-III). The anterior displacement of the neural arch in
caudals aiso resemble those
mid-caudals is considered a synapomorph,v of Titanosauriformes by Salgado et al. (1997,13) and the presence of the neural arch on the anterior portion of the caudal vertebrae is suggested as a bra-
chiosaurid feature bv Upchurch (1995, 380); this feature is not considered b,v'lfilson (2002).
MPCM-V13
is the basal part of the neural spine (Fig.
18.11A-C) of a relativel,v small caudal vertebra. It is rectangular in cross section, narrow in laterai view and very narrow in anteroposterior view, with laminae at the base. It is most similar to rhe narrow, tall spines of diplodocoids rather than to the wide spines of the caudals of Brachiosaurus brancai (Janensch 1950, pls. I-III). k shows a lateral spinal lamina that could correspond to the "spinoprezygapoph,vseal laminal on iateral aspect of neural spine" in the
anterior caudals that is synapomorphic of Diplodocidae + Dicraeosauridae according to \flilson (2002, 270).
/;\
C
E
SPRL
2cm
An isolated spine of a caudal vertebra (Figs. 18.5L, 18.11D-E) is club-shaped in anteroposterior vierv, features anteroposterior or posteroanterior sloping, and has wide anterior and posterior entheses for the attachment of the intervertebral ligaments. The apical semicylindrical portion is fused to the shaft and the suture is still partly recognizable. Dalia Vecchia (1998a) noted the resemblance with the spines of some anterior caudals of camarasaurids. However, also titanosauriforms seem to have somewhat club-shaped spines in the caudal vertebrae (for example Venenosanrus dicrocei, Tidwell et al. 2001, fig. 11.3A-C; the titanosaur "Gigantosdurus
robustus," Bonaparte et al. 2000, pl. 6). Thus the Istrian spine could belong to the titanosauriform caudals described above. Unfortunately no spines are preserved in the caudals from the
Fig.18.11. Caudal neural spines, Intc H.t ttte r i u i n n-e.t rl1' Ba rrtnt ia n. Bale/Valle, Istria. (A) MPCMV13,left lateral uieu. (B) MPCMY1.3, snterior uiew. (C) MPCMY13, dorsal uiew. (D) MPCM-V9, dntefiof uieu,. (E) MPCM-V9, rigbt lateral uieu. After Dalla Veccbia ( 799 8 a ), ntodified. Abbreuiatir,tns: a = Llilterior; p = posterbr; LSL = Iaterttl spirul lamina; for other abbreuiations see
Figure 18.6.
Bale/Valle site.
Late Albidn Five late Albian sites with dinosaur footprints, and at least eight different footprint-bearing levels, are known in Istria (Dalla Vecchia et al. 2000a, 2002). Sauropod footprints are present
in two outcrops of the Solaris campground
near
Cervar/Cervera, probably representing the same level (Dalla Vecchia and Tarlao 2000). The footprint-bearing layer belongs to a section of inner platform carbonates and shows dozens of sauropod footprints (Dalla Vecchia et al. 2000a). Most of the footprints are not organized in tracklvays and pes-manus couples are practically absent (for a detailed description of the site, see Dalla Vecchia and Tarlao 2000). The only clearly recognizable trackway shows overprinting of the pes on the manus and is not wide-gauged (Fig. 18.12A). The largest manual print in the sample is 24 cm wide and the iargest pedal print is about 50 cm long, but most of the other footprints are smaller. There is great variability in the shape of the pedai prints (Fig. 18.13). Digital marks are usually very short and, unlike the Brontopodus pedal prints from the Albian of Texas (Farlow et al. 7989), the mark of digit I does not project more than that of the other digits nor does it show a prominent ungual mark. The better-preserved manual prints resemble the manual prints of Brr.tnBetween Gondwana and Laurasia
.
413
A
B
,ffi, YrVlr r+-//
C |
D
.t/-l\ \\ ) I
q
\v/
L
ffi^ \'4,{ |
"ffi
N
tA'./
yz
{ {i ,\q120 ;ll
,'"t
/\,,,\ n '^t""4 m?
ffiI \*'t'rl
i:'
,' lp \--\:d /''"'\m \*i\ l ^ ,A\ -
\t//
/;...
q
t.
\
1i ,'l
@
1m
D I,
d
!
lD
to 1rn
(t), V/ *Au \Yg! \MJ \-t
1m
Fig. 18.12. Sauropod trackways of the "middle" Cretaceous of Istria. 1A) Trackwar segment from the late Albittrt outcrop SOLll, Solaris site, Istria. (B) Segment of the long saurctpod trackwdy from the late Cenomanian site of Fenoliga, Istria. (C) Segment of the better-preserued sauropod trackway in the late Cenomanian site of Karigador/Carigador, lstria. (D) Brontopodus "wide gauge" tracks. A after Dalla Yecchia and Tarlao (2000), modified; C after Dalla Vecchia et al. (2001b); D after Farlout et dl. (1989), modified. Abbreuiations: m = mdnudl print, p pedal = print.
topodws birdii with digits arranged in a semicircular pattern, but show five separate digital marks, whereas the print of digits II-IV is single in Brontopodus. Furthermore, the distal termination of digits I, II, IV and V was rounded and of similar size, whereas digit III appears to be larger and its print is trapezoidal-rectangular in the Is-
414 . Fabio M. Dalla
Vecchia
l0 cm
trian manual prints (Fig. 18.1a). These features distinguish the Istrian ichnotaxon Titanosdurintanus nana from Brontopodus birdii (Dalla Vecchia and Tarlao 2000). The large, rounded to rectangular-shaped digital prints, mainly those of digit III, are reminiscent of the outline of the distal surface of the metacarpals (Fig. 1 8 . 1 5 ), although the possibility remains of the presence of terminal disk-like phalanges imbedded in a pad. As in the case of Brontopodus, the absence of a claw in digit I and of any evidence of a free, phalangeal portion of the digits provides some information about the taxonomical status of the trackmaker. Camarasaurus and Diplodocoids have a well-developed ungual on manual digit I, and a short phaiangeal portion in the toes (Fig. 18.4A) that could have been free or embedded in a pad together (Farlow 1992). Brachiosauras has a distinct ungual on digit I (Fig. 18.4B). Titanosaurs are considered to lack manual phalanges, and rested on the distal end of the metacarpals, which lack condyles and were distally expanded and flat (e.g., Gimenez 1992; 'lfilson and Sereno 1998; Figs 18.4C, 18.15; Salgado et al. 1997; and see Apesteguia this volume). The trackmaker of Titdnosaurimanus ndna rs here considered a titanosauriform more derived than Brachiosdurzs, possibly a titanosaurian. It could descend from the titanosauriforms iiving on the platform during late Hauterivian-early Barremian times, or it could be a titanosaurian that immigrated from the continent before Aptian times. It had a digit III
Fig. 18.13. Sattropod pedal prints (Titanosaurimanus nana) from tbe Albian Solaris site, Istria. (A) sl0p; (B) sep; (c) s1p; (D) s1lp; (E) S7p; (F) S13p (u.,ith the manual print S14m); (G) SSp. Late
Reuersed
with respect to the
originals because based on the moulds. After Dalla Vecchid dnd Tarlao (2000), mctdified. I-V = digit I-Y.
Between Gondwana and Laurasia
.
415
Fig.
1
8. I
1. Titanosaurimanus
nana, holottpe, manudl print S5m, Solaris site, Istrid. Pldstctt,t:,pe preserued at the MPCM,
Monfalcone, Itttly. Arro--s show the main directior.ts of rnud sLtbsi dence that slightll, narrou,etl
footltrint. l-V = iigtT 1-Y. II/IV and I/V are used because it is not possible to stdte tuhether the footprint is a left or right. After Ddlla Vecchia md the
Labels
Tarlao (2000), modifi ed.
Fig.
18.1
5. Metdcdrpus
attriblie(l
to the South American liI
attosdu ria n f pachro..t
urut
sctuttoi (Rubdn Martinez, pers.
comnt.), Uniuersitl, " San .l. Bosc o. " (.onr',dnro Riuadat io, Ar gentin d. Le ft, rtrtter i or uieu' ; rigbt, uertral/distal uieu. Scale
bar:10 cm.
416 . Fabio M. Dalla Vecchia
print characteristically broader than the other digital prints. This probably could be recognized in the manual skeleton, but unfortunateiy most of the published figures of sauropod forefeet show only the outline of the proximal end of metacarpals. '$fhere also the distal outline is reported, as in Magyaroslurus (Huene 1932, pl. 46, fig. 10c), metacarpal III is the same size as the others. This is also the case for EpachtosdurLts (Fig. 18.15). The linear measurements of the sample from the Solaris site are about half those in a sample of sauropod footprints from the Albian pericontinental carbonare platform of Texas (Fig. 18.16) and further comparison shows that the Istrian footprints have an unusuall)' small size for sauropodan standards (Dalla Vecchia and Tarlao 2000).
Lp Solaris ll N .26 M = 33.4
Lp Texas
N=13
Fig.18.16. Length (Lp) distribution in a sample of sauropod pedal prints from the late Albian oLttcrop SOLII, Solaris
M = 72.7
site ldark gray) and in a sample of sauropod pedal prints from the
Albitn oITcxas tlight gral). Measurentents are in centimeters.
M = tneatt ualuc: N = nutnber ol measurements. After Dalla Vecchia and Tarlao (2000), modilied.
Late Cenomanian. Four Cenomanian outcrops with dinosaur footprints are known in Istria (Dalla Vecchia et aI.2001). The footprint-bearing layers are found in tidal horizons inside stratigraphic sections dominated by mounds of rudist bivalves and beds with rudist shell fragments, and they are marked biosrratigraphically by a typical late Cenomanian foraminiferal association (Dalla Vecchia et al. 2001).
A long trackway of about forty consecutive pedal prints, with several footprints not clearly organized in trackwavs and poorly preserved, are exposed at the Fenoliga islet in southern Istria (Dalla Vecchia et al.2001). Pedal print lengths are 40 cm or less. Mezga and Bajraktarevic (1999) identified nine groups of footprints and attributed them to small sauropods. The main trackway shows a prevailing overprinting of the pes on the manus and a mediumgauge; digital prints and the actual manual shape are not recognizable because of poor preservation (Fig. 18.128). The Karigador/Carigador site preserves two sauropodan trackways and some isolated prints (Dalla Vecchia et aI.2001). All the pedal prints have lengths equal to or less than 40 cm. In no case can distinct digital marks be observed. The manual print is crescentshaped and deformed by the close pedal print (Fig. 18.17). The gauge is decidedly narrower (Fig. 18.12C) than in Brontopctdus (Fig. 18.12D). Some poorly preserved, small sauropod footprints are possibly present also in the Grakalovac site (Dalla Vecchia et aI.2001; A. Tarlao, pers. comm.).
Other Sites with Sauropod Evidence Ichnofossiis of quadrupedal dinosaurs, possibly including sauropods, are found also in the Apulia Platform. A quarry opened in shallow marine limestones of late Coniacian-early Santonian age near Altamura, in the Puglia region of southern Italy, revealed a thousand footprints of small-sized quadrupeds. Up to date, only a
Between Gondwana and Laurasia
.
417
Fig. 18.17. A manus-pes couple a small sauropod, late
of
Cenotnanian, Kari gador/Ca ri gador site,
I s
t
ria.
few trackways have been studied and attributed to a ,,five meter long . . . hadrosaurid" (Nicosia et al. 1999,237) with pedal prints only 25 cm long. Ar present, the site is important mainly because ir shows thar the very high number of quadrupedal trackmakers, unlikely to be crocodylomorphs or other non-dinosaur retrapods, were all of small size.
Paleoenvironmental and Paleogeographical Implications The first implication of the sauropod study is paleoenvironmental. The Adriatic-Dinaric Platform has been reconstructed as a shallow marine bank isolated in the central Tethys during the entire Cretaceous. bur this reconstruction is nor correct, or at least it is misIeading. Emergent areas had to be present to allow the dinosaurs to live, providing them with food and fresh water. Geologists have always considered a very short "life-span" and/or a relatively reduced surface for the emergent parts of the platform, because significative lithological bodies of "continental,' origin (i.e., fluviolacustrine or eolian) were not recognized in over 150 years of geological studies. A well-developed fluvial system and relative deposition could hardly exisr on an emergent carbonare platform because waters usually flow underground in caves originated by carbonate dissolution. Bauxite and brackish-lacustrine sedimentary bodies usually have a limited extent and a poor dating. Only a de-
418 . Fabio M. Dalla
Vecchia
tailed and extensive biostratigraphic study and the identification of stratigraphical gaps could allow recognition of the emersions of the platform and their extent. The second implication is paleogeographic and concerns the isolation of the platform. Titanosauriformes are the most common sauropods in the sample from the upper Hauterivian-lor,ver Barremian of Istria. Their basal status is suggested by the highly laminar neural arches of the presacral vertebrae, the presence of nonprocoelous caudals, and the overall similarity of the best-preserved cervical and caudals to those of Brachioscturus. A probabie diplodocoid (Histriasawrurs) is also present, but rarer. A sauropod association, dominated by basal Titanosauriformes (i.e., brachiosaurids), is typical for the Early Cretaceous of England (Owen 1875, 1876; Hulke 1879; Blows 1995; Naish and Martill 2001) and North America (Marsh 1888; Langston 1.974; Britt and Stadtman 1996 Britt et a|.1,997,1998; Winkler et al. 1997; Ratkevich 1998; Tidwell et al. 1999 2001,;'Wedel et al.2000a, b; Tidwell and Carpenter 2002). A sauropod association dominated by titanosauriforms and with non-diplodocid diplodocoids could not be present in the late Hauterivian-early Barremian of the AdriaticDinaric Platform, if the latter was completely separated from continenral areas by deep seas since Liassic rimes. A simjlar conclusion was reached by Barrett et al. (2002) about the supposed faunal isolation of eastern Asia during the Early Cretaceous. Short-term eustatic sea-level oscillations could not be responsible for connections between the closest continents and the platform in such a scenario, because those oscillations were only in the order of some tens of meters (Christie-Blick 1990). Probably they were not sufficient to expose the oceanic basin bottom or a deep (100-200 m) epicontinental sea and to permit connections with the closest lands. Only an emergent bridge or a shallow marine ridge exposed during lo'uv stands could allow the passage of sauropods. According to Haq et al. (1987), the greatest short-term eustatic sea-level fall of the Middle Jurassic-Late Cretaceous interval occurred during early Valanginian times, and a tectonically controlled regression is reported in Europe for the early Barremian (Jaquin and De Graciansky 1998). They could cause the formation of migration routes.
Did the Platform Connect with "European" Lands or with the Afro-Arabian Continent? The probable affinity of Histriasaurus with Gondwanan diplodocoids suggested a southern connection of the platform with Afro-Arabia (Dalla Vecchia 7998a). The recent recovery of a rebbachisaurid in the upper Barremian-Aptian of La Revilla-Ahedo (northwest Spain) (Fidel Torcida Fern6ndez-Baldor, pers. comm., January 12,2003) shows that rebbachisaurids were present also in the "European" emergent areas. Faunal interchanges between England and Afro-Arabia during earliest Cretaceous times are supposed by Martill and Naish (2001) on the basis of theropod and orBetween Gondwana and Laurasia
.
419
nithopod affinity, and also between Nonh America and England orr the base of sauropod affinity (Tidwell and Carpenter 2002;. the presence of a rebbachisaurid in Spain would confirm the possibility of migration betr,veen the western European landmass and AfroArabia during Berriasian-Barremian times. Supporr for a Gondwanan connection is the affinity of the Hauterivian-Barremian associations of shailow waters with benthic foraminifers between the Adriatic-Dinaric Platform and the peri-Afro-Arabian carbonare platforms, whereas the coeval associations of Sardinia, France, and Spain are different (Cherchi and Schroeder 1973). Furthermore, the Piedmont-Ligurian Ocean was present at least since the Late Jurassic between the peri-Adriatic platforms and the Iberian Block (see Fourcade et aL. 1993; Philip et aL. 1993; Fig. 18.34). Thus, the most probable connection was with the northern part of Afro-Arabia. The paleogeographic position of the peri-Adriatic platforms during the Hauterivian-Barremian was probably more similar to that during the Tithonian (Fig. 18.3A), rather than that of Buiot et al. (2000) for early Hauterivian times. The relatively deep epicontinental sea, which supposedly covered the margin of Afro-Arabia, probably had shallow rises that emerged during low stands, allowing a migration route between the emergent portion of the AdriaticDinaric Platform and the continent (Fig. 18.3A). Unfortunatel,v, we have a limited dinosaur record for the Late Jurassic to Aptian period in Norrhern Africa. Surprisingll,, Titanosauriformes are unknown in the supposed Neocomian sites of Niger, where the peculiar non-neosauropod Jobaria is common (Sereno et al. 7999). Sauropod remains from the same unit were described by de Lapparent (1960) as Rebbachisaurus tamesnensis, but according to Sereno et al. (1994) this attribution is unsubstantiated. The rebbachisaurid Nigersaurus was present in the same region during Aptian-Albian times, with "titanosaurians', represented by many isolated bones, including derived caudal vertebrae with spongy bone or internal cellular structure like those of Saltasdurus (Sereno et aI. 1.999,7344, 7346). Scattered sauropod bones, unfortunately still undescribed, are found in the early Albian of Tunisia (Benton et al. 2000). Bones attributed to .,ritanosaurs" are relatively common in the Cenomanian of Morocco (where Rebbdchisaurus garasbae is found) and Egypr (see Dalla Vecchia and Tarlao 2000 for a brief review; Smith et at.2001).
Insular Dwarfism?
A
change in the size of Adriatic-Dinaric platform dinosaurs occurred between the Hauterivian-Barremian and the AlbianMaastrichtian associations. The tridactyl footprints from the Hauterivian-Barremian, most probably all rheropodan, are large (length >25 cm) (Dalla Vecchia 1998b). Despite its small size, the bone sample shows a diversified association of smali to large sauropods and small to (possibly) large theropods. The large vertebra of Fig. 18.8 beiongs to an individual at least 17-18 m long, fol-
420 . Fabio M. Dalla
Vecchia
Iowing sauropodan length estimations based on single bones in Naish and Martill (2001). Aiso, the Haurerivian-early Barremian footprint sample from the Apulia platform, berween ihe Adriaric-
Dinaric Platform and Afro-Arabia (Fig. 18.3A), is represented mainly by large tridactyl footprints (prevailing footprint lengths are 30-35 cm), mostly theropodan (Gianolla et al. 2000).
In conrrast, all the late Albian and late Cenomanian sauropods, identified by footprints from different horizons and localities, are rather small for sauropod standards. The largest manual print in the Albian and cenomanian sample of Istria is smalrer than the manual print from the upper Hauterivian-lo,uver Barremian of northeast Italy. Although other ichno-associations in the world present small sauropodan footprints, they are always associated rvith prints of large individuals. The Albian-Cenomanian tridactyl footprint record of Istria shows the same pamern of size reduction, with most footprint lengths around 18-20 cm, and verv few specimens longer than 25 cm (Dalla Vecchia and Tarlao 2000). Also the single "iguanodontian" trackway, from the late Albian of
Istria, shows footprints only 28 cm long (Dalla Vecchia et al. 2002). The hadrosaurians from the upper Santonian of Italy are only half the length of hadrosaurids from North America and Asia and, since body mass is proportional to the cube of total length, they were much smaller. Teerh from rhe Maasrrichrian of th. Slovenian Kras are all of small size. Furthermore, rhe footprints of quadrupedal dinosaurs in the upper Coniacian-lower Santonian of
the Apulia Platform are also small.
Dalla Vecchia and Tarlao (2000) and Dalla Vecchia (20021 noted that this reduction of dinosaur size in the peri-Adriatic platforms occurred between the late Barremian and the beginning of the late Albian, coinciding with the Aptian opening of the Eastern Mediterranean ocean between the northern Afroarabian shelf anc the peri-Adriatic platforms (Fig. 18.38). This isolation and the reduction of the emergenr surface in the platform (Adriatic Island), because of eustasy or tectonics, might have resulted in dwarfism in the dinosaur population. There is a graded trend from giantism in the smaller species to dwarfism in the larger species in living insular mammals G.g., Lomolino 1985). Large herbivores characteristically are smaller than their relatives on the mainland (e.g., Roth 1990). This is observed for Pleistocene mammal faunas (e.g., Kotsakis 1985; Roth 1990). The insular faunas are also characterized by lower species diversity rhan the main[and, rerenrion of primitive features, fewer species of carnivores, and the absence or extreme rariry of iarge piedators (e.g., Kotsakis 1985; Roth 1990; Burness et aI.2001). The main cause of dwarfism in large herbivores seems to be the resource lim,
itations of an island (e.g., Lomolino 1985; Roth 1990). Also, the advantages of large size as defense against predation do not exist where predators are absent or small (Lomolino 1985). The concept of dwarf dinosaurs dares back to 1912 (Nopcsa 1974). The titanosaurian MagyarosctLtrus, the hadrosaurian Tel-
Between Gondwana and Laurasia
.
421
mAtosaurus, and a nodosaurid ankylosaurian (" StrwthiosAurus") from the Maastrichtian of the Hateg Basin, Transylvania, Romania, have been considered insular dwarfs because of their diminu'Weishampel
et al. tive size and primitivity (Nopcsa 1974, 1.91.5; 799t, 1993;Jianu and Weishampel 7999 Pereda Superbiola 1999; Mussel and \Teishampel 2000). Humeri attributed to Magyarosaurus are only 37-40 cm long (Huene 1932) and all the bones recently excavated near Sanpetru by the Museum of Deva belong to very small, adult individuals (pers. obs.).Telmatosaurus was around 5 meters long (more or less the same as the late Santonian hadrosaurians from Italy) and its estimated weight is 500 kg, about 10% the body mass of the Campanian-Maastrichtian 'Weishampel et al. hadrosaurids of North America according to (1991). Like the emergent parts of the Adriatic-Dinaric Platform and the Apulia Platform, Transylvania was part of an island of the Late Cretaceous European archipelago (Sfeishampel et al. 1991; Philip et al. 2000b; Dalla Vecchia 2002). Other hadrosaurians, ankylosaurians and sauropods from that archipelago, found in Austria, Germann Netherlands, Belgium, France, and Spain, are unusually small and have been considered as possible insular dwarfs (Wellnhofer 1994; Pereda Superbiola et aI. L995; Pereda Superbiola 7999 Dalla Vecchia 2003). Thus, the dinosaurs of the Adriatic Isiand show just the same trend as those of the other islands of the archipelago. Acknowledgrnents. I am grateful to Dario Boscarolli, Alceo Tarlao, Maurizio Tentor, Giorgio Tunis, and Sandro Venturini, with whom I have worked on the dinosaurs of Istria since 1993 and whose contribution has been fundamental to the discovery and study of the specimens mentioned in this paper. I thank Jos6 Bonaparte, Rub6n Martinez, Jorge Calvo, Leonardo Salgado, SebastiSn Apesteguia, and Rodolfo Coria for support and access to the collections under their care in Argentina; Alexander Kellner and Diogenes Campos for support in Brazil; Alexander Kellner for help at the American Museum of Natural History of New York; and Mary Dawson for her support at the Carnegie Museum, Pittsburgh. I thank Jim Fariow for useful advice and also the reviewers of the manuscript, Kenneth Carpenter and Virginia Tidwell. Part of this work is the result of my post-doctoral project at the Dipartimento di Geologia, Paleontologia e Geofisica, University of Padua during the years 1995-1997. References Cited
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2002. Sauropod dinosaur phylogeny: Critique and cladistic anal.vJournal of the Linnean Society 136:217-276. 'Wilson, J. A., and P. C. Sereno. 1998. Earlv evolution and higher level phvlogeny of sauropod dinosaurs. Society of Vertebrate Paleontology, Nlemoir 5: 1-68. 'Winkler, D., L. Jacobs, and P. A. Nlurry.. 1997. Jones Rancl.r: An Early Cretaceous sauropod bone-bed in Teras. Journal of Vertebrate Paleontctlogy 17 (supp. to 3): 85A. Yilmaz, P. O., I. O. Norton, D. A. Leary. and R..J. Chuchla. 1996. Tectonic evolution and paleogeography of Europe. In P. A. Ziegler and F. Horvath, eds., Strttcture and Prospects of Alpine Basins and Forelands, 47-60. M6moire Musee nationale de Histoire naturelle, Peri-Tethys Memoir, no. 2. Paris: Edirions du Museum. Zappatena, E. 1990. Carbonate paleogeographic sequences of the periAdriatic region. Bollettino della Societd Geologica Italiand 109: 5-20. sis. Zoological
Berrveen Gondrvana and Laurasia
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L9. Sauropods of Patasonia: Systematic Update and Notes on Global Sauropod Evolution LpoNenoo SercADo AND Rooorpo A. Conre
Abstract Patagonian sauropods are known from the Middle Jurassic through the Late Cretaceous. The Jurassic record consists of Amygddlodon patagonicus and the basal eusauropods Volkheimeria chubutensis and Patagoslurus fariasi. Early to mid-Cretaceous sauropods include diplodocoids represenre d by Amargasaurus cazaui, "Rebbacbisaurus" tessonei, and Rayososaurus agrioensis, and the first Patagonian titanosauriforms, Chubutisaurus insignis, Andesaurus delgadoi, and other species still under study. The first titanosaurians with procoelus caudal vertebrae appeared in the eariy Cenomanian. The South American titanosaurid radiation coincided with the extinction of the diplodocoids. The Patagonian titanosaurid record is continuous from the Cenomanian up to the end of the Cretaceous, and includes several different forms, like the gigantic Argentinosdurus huinculensis and the relatively small saltasaurines, which are possibly exclusive to the CampanianMaastrichtian of South American.
430
/lt)
/
16
2
4 5
10 12 17
Fig. 19.1. Majr:r sauropod localities in Patagonia. Lago Pellegrini-Cinco Sabos (1), Plaza Huincul Q), Bajdda del Agrio (3), La Amarga (4), El Choc6n (5), Salitral Moreno (6), General Roca
r{
r_\
t-,. Los Aldmitos tSt,lngcniero Iatubacci (')1. Pampo de Agnia 1101. Cerro Condor tl I t, Lstancia Fernindez 1 I 2 t. Cerro Barcino (13), Estancia "Ocho Hermanos" (14), Rio Senguer (15), Chos Malal (16), and Las Horquetas (17 ).
Introduction "Patag6n" is the name given to the aonikenk aborigines by the first Europeans exploring southern South America. Today, "Patagonia" refers to the land once inhabited by the "patagones." Convenrionally, Patagonia is the region south of the Rio Colorado, a territory
that actuaily comprises the provinces of Neuqu6n, Rio Negro, Chubut, Santa Cruz, and Tierra del Fuego (Fig. 19.1). In popular
culture, "Patagonia" is not associated with indigenous peoples, but with dinosaurs and other prehistoric creatures. Indeed, bones of enormous sauropods are common in Patagonia due in part to favorable, erosion-producing "badlands." The first report of sauroSauropods of Patagonia
.
431
pod bones were those dug up by soldiers, settlers, and farmers in the late nineteenth century (Coria and Salgado 2000). Soon afterward, there were scientific commissions organized by the Museo de La Plata, with subsequent research carried out by specially invited European professors R. Lydekker and F. von Huene. These men laid the basis of our current knowledge on the evolution of the sauropods in South America. Beginning in the 1980s there was renewed interest in Patagonian sauropods, with research by J. Bonaparte and J. Poweil from the Miguel Lillo Institute (San Miguel de Tucum6n, Argentina), and later by J. Bonaparte from the Museum Bernardino Rivadavia (Buenos Aires, Argentina). These researchers made successive trips to numerous sites in northern, central, and southern Patagonia (Bonaparte, 1986; Powell, 1.987,1990). Since
then, numerous erpeditions have collected sauropod remains, which we summarize in context with other taxa not found in Patagonia. After all, this region of South America was not isolated during the Mesozoic, so it is impossible to document the evolution of Patagonian faunas outside of the wider context of the global sauropod record. -We organize the chapter geochronologically, describing the diverse Jurassic and Cretaceous taxa and discussing their geological record and phylogenetic relationships. Notes on anatomy, systematics, and evolution of each group are added. Finally, we outline the rnajor features of sauropod evolution during the Cretaceous, the period that has produced the largest amount of sauropod fossils.
Institutional abbreuiations. MACN-Museo Argentino
de
Ciencias Naturales, Buenos Aires, Argentina; MCF-PVPH-Museo
"Carmen Funes," Paleontologia de Vertebrados, Plaza Huincul, Neuqu6n, Argentina; MCS-Museo de Cinco Saltos, Rio Negro, Argentina; MLP-Museo de La Plata, Buenos Aires, Argentina; MPCA, Museo Provincial "Carlos Ameghino," Cipolletti, Rio Negro, Argentina; MPEF-Pv-Museo Paleontol6gico "Egidio Feruglio," Paleontologia de Vertebrados, Trelerv, Chubut, Argentina; and PVl-Instituto "Miguel Lillo," Paleontologia de Vertebrados, Tucuman. Argentina. Jurassic Sauropods
The oldest record of a Patagonian sauropod is the holotype of Amygdalodon pdtagonicus from the Bajocian of Chubut Province, Central Patagonia (Cabrera, 1947; Casamiquela, 7963) (Fie. 79.2). This species, known from a few bones (MLP-46-VIII-27-712,MLP36-XI-10-3/9, and MLP-36-XI-10-312), which represent more than one individual (Rauhut, pers. comm. ,2002), is a probable basal eusauropod (sauropods more related to Sdltasauras than to Vulcdnodon, Wllson and Sereno 1998). Amygdalodon rvas traditionally
included in the "Cetiosauridae" (Mclntosh 1990), a family of sauropods whose monophyly has been repeatedly questioned (Upchurch 1995;'$Tilson and Sereno 1998). The absence of pleurocoels in the cervical and dorsal vertebrae reveals that Amygdalctdon is, in ,132
.
Leonardo Saleado and Rodolfo A. Coria
d
fact, a primitive eusauropod (\X/ilson and Sereno 1998), although the seeming lack of marginal denticles on its teeth suggests it is closer to the neosauropods. The Callovian sauropods include two species from the Cerro C6ndor (Chubut Province), Volkheimeria cbubutensis (southern Cerro C6ndor) and Patagosawrus fariasi (northern Cerro C6ndor) (Fig. 19.3). Both are found in the Caflad6n Asfalto Formation. Rauhut (2002) suggests that the material assigned to Patagosaurus
Fig. 19.2. Amygdalodon patagonicus. Holotype, MLP 3 6-Xl-1 0-3/2. (a) Ceruical centru?n, (b) and (c) dorsal centra, (d) and (e) caudal centra, (f) and (g) rib fragments. Scale bar: 10 cm.
fariasi may belong to more than one species. These sauropods were also initially assigned to the Cetiosauridae. Volkheimeria chubutensis,
which is the more primitive of the two, was considered by Bonaparte (1986) to be related to Lapparentosaurus madagascariezsls from the Jurassic of Madagascar based on the neural laminae of the dorsal vertebrae. Patagosaurus fariasi was considered by him as related to other cetiosaurids, such as Barapasaurus and Cetiosawrus. Rauhut (2002) has correctly pointed out that both of these species from Cerro C6n'$Tilson (2002) dor are basal eusauropods. stated that Patagosaurus is
a basal eusauropod that is more derived than Barapasaurus. .N1though the teeth figured by Bonaparte (1986, figs. 33 and 34) lack marginal denticles on their crowns, they are clearly present in an in situ tooth in the dentary (MACN-CH933, Bonaparte 1986), and in a new dentary that is most probably referable to Patagosaurzs. On the other hand, denticles are absent on the marillary teeth of MACNCH-934 (Rauhut, pers. comm.,2002). The absence of denticles on some teeth may be due to wear because these teeth all show strong apical wear of the labial margins (Bonaparte, 1986, frg.34; Rauhut, pers. comm., 2002). The proximal end of the Patagosaurus trbia is transversely compressed as in other non-neosauropod sauropods (\Wilson and Sereno 1998,48), except Joban z (\Tilson 2002). Sauropods of Patagonia
.
433
iil(ry l
Fig.
19.3 . Patagosaurus
fariasi.
Mounted cdst dt the Museo Argentino de Ciencias Naturales " B ernar dino Riua ddu id, " Buenos Aires,
The holotype
of
Tehuelchesaurus benitezi (Fig. 19.4) was
found in the Caflad6n Calcdreo Formation at Estancia Ferndndez (Kimmeridgian-Tithonian, Rauhut, pers. comm. 2002), a locality northwest of Cerro C6ndor. This species might be related to Omeisaurus tianfuensis from the Middle Jurassic of China (Rich et al. 1999). However, Rauhut (20021 considers T. benitezi as the sister taxon of the Titanosauriformes as defined by Wilson and Sereno (1998). In fact, the opisthocoelous condition of the dorsal vertebrae suggests an affiliation with the Camarasauromorpha as defined by Salgado et al. (1997).
A fragmentary knee (distal end of a femur and proximal
tibia and fibula) of a juveniie sauropod has been collected from the Tordillo Formation (Kimmeridgian) in Chos Malal, Neuqu6n Province, northern Patagonia. Based on the transverse narrowness of the proximal end of the tibia, Garcia et al. (2003) concluded that this fossil belongs to a basal eusauropod. The presence of a basal eusauropod in the Late Jurassic of Patagonia, coupled with the record of the neosauropod sister group (lobaria) in the Neocomian of Niger (Sereno et al. 1999), strongly suggests that non-neosauropod dinosaurs survived in Gondwana, together with more derived groups, after the extincends of the
434 . Leonardo
Saleado and Rodolfo A. Coria
ig. 1 9.1. Tehuelchesaurus benitezi. Holot r-p e, MPEF-P u1 125. Dorsdl uertebrae in left lateral uiew. Scdle har: 10 on. F
tion of these sauropods in other regions (Canudo and Salgado in press ).
Cretaceous Sauropods The Cretaceous has the best record of Patagonian sauropods. Until recently, most sauropod bones were known from uppermost Cretaceous formations. However, in the last few years, a number of new specimens were collected in Lower and mid-Cretaceous strata in northern and central Patagonia. These specimens have substantially modified our view of the evolution of these enormous animals (Sciutto and Martinez 1994; Calvo and Salgado 1995). Patagonian Cretaceous sauropods belong to two major groups, the Diplodocoidea and the Titanosauriformes. The latter clade consists of a series of nested subgroups, the Titanosauria, Titanosauridae, and Saltasaurinae, which are discussed below. The phylogenetic relationships of the Titanosauriformes are debated in Salgado et al. (1,997), Wilson and Sereno (1998), Currn Rogers, and Forster (2001), and'il/ilson (2002). Diplodocoids. \Tilson and Sereno (1998) consider the Diplodocoidea as all neosauropods more closely related to Diplodocus than to Saltasaurus.In the Hauterivian-Barremian, the only sauropod recorded in Patagonia is the diplodocoid Amargasaurus cazaui, a bizarre member of the Dicraeosauridae (Salgado and Bonaparte 1991) (Fig. 19.5). This 1O-meter-long dinosaur, found in Neuqu6n Province, is closely related to Dicraeosaurws sattleri from the Upper Jurassic of East Africa (Salgado 1999).If Amdrgasaurus cazaui is phylogenetically closer to Dicraeosaurus sattleri than it is to Dicraeosaurus hansemtnni, also from East Africa, Dicraeosaurus is paraphyletic and D. sattleri should be replaced, potentially by Amargasaurus sattleri.In fact, none of the ten autapomor'Sfilson (2002, 273) can be phies of Dicraeosaur;as presented by verified in Amdrg.dsdurus cdzaui. Sauropods of Patagonia
.
435
Fig. 19.5. Amargasaurus cazaui. Skeletal restortttion. Scale bar: 1 meter.
The most noticeable feature of the postcranium of Amargasaurus cazaui is the exceptional length of the cervical and anterior dorsal neural spines that are, as in other derived diplodocoids, deeply bifurcated. These spines could have functioned as defensive weapons (Salgado 1999). The cervical and dorsal centra have shal-
low or no pleurocoels, as in other dicraeosaurids. The most
un-
usual feature of the skull is the persistence in the adult stage of the parietal and postparietal fenestrae. Both openings are possibly derived characters common to all dicraeosaurids (Janensch 7929 Salgado and Calvo 1992). As in other dicraeosaurids, the basipterygoid processes, which ordinarily connect the braincase with the roof of the mouth, are extremely long and somewhat divergent. In turn, the supratemporal fenestrae are reduced, as also occurs in rebbachisaurids and titanosaurians (Calvo and Salgado 1995: Salgado and Calvo 7997\,. Besides dicraeosaurids, Early and mid-Cretaceous sauropods include the Rebbachisauridae, a group of basal diplodocoids. The Patagonian rebbachisaurids include Rayososaurus agrioensis from the Aptian (Bonaparte 1996) and "Rebbachisaurws" tessonei front the Cenomanian (Calvo and Salgado 1995) of Neuqu6n province. The Rebbachisauridae are the sister group of the clade comprised by Dicraeosauridae and Diplodocidae (Sereno et al. 1999). Unlike diplodocids and dicraeosaurids, rebbachisaurids have plesiomorphically undivided presacral neural spines. One of rhe most conspicuous synapomophies of the group is the wide erpansion of the posterior blade of the scapula (Wilson 2002), as can be seen in the Patagonian species Rayososaurus agrioensis and " Rebbachisaurus" tessonei (\X/ilson 2002). In the skull, rebbachisaurids have slender, peglike teeth, and they have basipterygoid processes anteriorly oriented as in other diplodocoids (Calvo and Salgado 1995; Sereno et a|. 7999 ; \filson 2002).
A probable rebbachisaurid caudal was reporred by Sciutto and Martinez (1994) from the Upper Cretaceous Bajo Barreal Forma-
436 . Leonardo
Salgado and Rodolfo A. Coria
tion in Las Horquetas near central Patagonia. The
transverse
processes of this anterior caudal are winglike, and the neural spine is formed by four laminae as in other diplodocoids.
Bdsal titanosauriforms. Diagnostic features of this group have been given by Salgado et al. (1997) and N7ilson (2002). The group is widely distributed throughout the world, and the oldest record is
from the Upper Jurassic. Salgado and Calvo (1997) claimed that many species previously assigned to the Brachiosauridae are actually basal titanosauriforms, comprising a series of successive sister taxa of the Upper Cretaceous Titanosauridae. These past misidentifications are due to characters previously considered as diagnostic of Brachiosauridae, which are actually applicable to other, more inclusive groups. Chubutisaurus insignis, a titanosaur-related sauropod from the Aptian of Chubut Province (central Patagonia), is one of these species (Fig. 19.5). Wedel et al. (2000) defined the Brachiosauridae by the elongation of the cervical vertebrae and ribs (although cervical vertebrae are not preserved in most basal titanosauriforms). They suggest that certain genera from the Early Cretaceous of North America, such as Cedarosawrus and Sonorasaurus, might belong to this lineage. The putative sister group of the Titanosauriformes, Tehwelchesattrus benitezl, is from the Upper
Fig. 19.6. Chubutisaurus insrgnrs.
Holotype. MACN-I 8222, Anterior caudal centrum in (A) posterior and (B) lateral uietus; mid-caudal centrum in (C)
posterior and (D) lateral uiews; mid-caudal centrum in (E)
posterior and (F) lateral uieuts; and mid-distal caudal centrum m (G) posterior and (H) lateral uiews. Scale bar: 10 cnt.
Sauropods of Patagoma
.
437
Jurassic of Chubut Province (Rich et aI. 1999; Rauhut 2002). All later Patagonian titanosauriforms are more closely related to the Titanosauria or are Titanosauria. Regarding the evolution of Titanosauriformes, Salgado et al.
(1997) argued that the protrusion on the lateral margin of the femur of the Titanosauriformes and the dorsal expansion of the preacetabular blade of the ilium could be biologically connected. The iliofemoralis muscle originates proximally on the preacetabular lobe of the ilium and distally it inserts on the lateral edge of the femur, below the greater trochanter (Borsuk-Bialynicka 1977, fig. 17). This association of a dorsally expanded preacetabular blade and lateral bulge of the femur suggests an increase in mass of that muscle. The increase of the iliofemoralis muscle may be a consequence of body mass redistribution resulting from the displacement of the center of gravity posteriorly (Salgado et aL. 1,997, fig. 9). This explanation for the lateral bulge is compatible with another explanation-that the bulge is the result of the medial deflection of the femoral diaphysis (\X/ilson and Carrano 1999). The development of a pubic peduncle of the ilium, which is perpendicular to the long axis of the sacrum in titanosauriforms, could be correlated to the posterior shift of the center of gravity and the lateral bulge of the femur (Salgado et al. 1997).If the titanosaunform femur is vertical, that is, arranged in its "resting phase," then the pubic peduncle of the ilium still retains its plesiomorphic anteroventral orientation. Instead, it is the long aris of the ilium and of the sacrum that has changed its orientation (Salgado et aL.1997, fig.9). The diverse modifications reported in the hip of titanosauriforms (and, to some extent, in their hindlimbs) could be related to the lengthening of the forelimbs and the concomitant anterodorsal inclination of the vertebral column (Salgado et alr.1.997, fig. 9). This lenorhino of rhe forelimb is seen in the humerus:femur ratio of basal titanosauriforms, which in Chubtttisaurus insignls is 0.86 and in Andesaurus delgadoi is 0.87. However, the lengthening of the forelimbs also occurs in the Camarasauromorpha, in which the metacarpals are long with respect to the length of the radius (Salgado et a|.7997). Thus, on the one hand, lengthening of the forelimb involves the humerus in titanosauriforms and the metacarpals in the Camarasauromorpha.In Camarasaurus there is ventral rotation of the ilia and the consequent posterodorsal inclination of the sacrum axis (Mclntosh et al. 1,996, plate 10, fig. c). These features may be a synapomorphy of the Camarasauromorpha instead of the Titanosauriformes as has been thought previously. Basal titdnosaurians. Sereno (1998) has defined the titanosaurians. Among the characters are the procoelous anterior caudal vertebrae. Powell (1986,242) conjectures that this condition offers biomechanical advantages related to occasional bipedal posture and the use of the tail as a third supporting point. However, he recognizes that procoely is advantageous only when compared to opisthocoely (Powell 1986,243). However, we note that the in the common ancestor of the titanosaurians (i.e.. all non-titanosaurian 438
.
Leonardo Salgado and Rodolfo A. Coria
titanosauriforms) the caudal vertebrae are amphiplatyan. Therefore, we do not agree with the supposed increase in biomechanical efficiency as the cause of the caudal procoely. It can only account for the greater efficiency of the procelous tail with reference to the opisthocoelous one, as Powell recognizes. Furthermore, Opisthocoelicdudia skarzynskii, whose caudal vertebrae are opisthocoelous, has modifications in the hip that Borsuk-Bialynicka (1,977) believes are for occasional bipedal posture. This means that occasional bipedalism may not necessarily require the attainment of caudal procoely. Titanosaurians are present on all continents except Antarctica. \Tilson and Sereno (1.998, fig. a9) place the origin of the group in the Upper Jurassic. Janenscbia robusta, from the Upper Jurassic of Tendaguru, Tanzania, is possibly a basal titanosaur (see Bonaparte et a1.2000 for an alrernative inrerpretation). The anrerior caudal vertebrae referred to Janenschid are procoelous (Mclntosh 1990) as in other titanosaurians, but the appendicular skeleton of the holotype specimen shows some plesiomorphic characters. For example, the distal end of the tibia is anteroposteriorly expanded (Janensch L9 61 , fig. 6, 21,2) and the referred metacarpals are short and robust (Janensch L961, fig. 2, 194; Bonaparte et al. 2000). It is possible therefore, that the materiai assigned to that taxon may be a mixture of different species. As stated above, many basal titanosaurians or species related to the Titanosauria, most of them from Lower Cretaceous strata, have been included within the Brachiosauridae (Mclntosh 1990). For example, Pleurocoelezs (see Tidwell et al. 2001; Carpenter and Tidwell. this volume) has teeth with wear facets inclined with respect to the labio-lingual axis, as in other titanosauriforms (Calvo 1994). However, in crown width, they present a condition intermediate between Brachiosaurus and Upper Cretaceous titanosaurids. The hoiotype ol Chubutisaurus insignis (MACN-18222) from the Aptian of Chubut Province (Corro 1975) (Fig. i9.6) is the oldest record of a titanosaurian-related sauropod in Patagonia. Recent discoveries corroborate that titanosaurians were well represented in Patagonia by that time (Apesteguia and Gim6nez 2001). Perhaps the recently described Agustinia ligabuei (Bonaparte 1999), as well as new discoveries from the Lohan Cura Formation (Aptian), also belong to this clade (Apesteguia, pers. comm. 2002a). Bdsal titanosaurids. The phylogeneric relationships of the Titanosauridae have been discussed by Salgado et al. (1997), Sanz et al. (1999), Smith et ai. (2001), and Curry, Rogers, and Forster (2001). In this group, the procoelous condition of the anterior caudals of basal titanosaurians has extended farther backward through the vertebral series. Additionally, this group of titanosaurians acquired a series of modifications in the cranial, axial, and appendicular skeleton. One modification is the lateral expansion o{ the ilia, which Wilson and Carrano (1999) hypothesized would have displaced outwardly the origin of femoral protractor muscles and the abdominal oblique muscles. Sauropods of Patagonia
.
439
One of the best-known basal titanosaurids comes from the Cenomanian of central Patagonia (Bajo Barreal Formation, Chubut Province). It is a nearly complete skeleton of Epachthosaurus sciuttoi (Martinez et al.2004); another specimen from northern Patagonia (Neuqu6n Province, upper Cenomanian) is also referable to Epachthosaurus (Calvo
1999 Sim6n and Calvo
20021.
Epacbthosaurus retains plesiomorphic characters that separate this taxon from the derived titanosaurids (Salgado and Martinez 1993). For instance, the hyposphene-hypantrum complex, which works as an accessory articulation in all saurischians, is lost in all titanosaurids except Epachthosawrws. Powell (7986, 301) and Apesteguia (this volume) believe the hyposphene-hypantrum complex gives the vertebral column greater rigidity and that its loss would increase the fleribility. As yet, the skull of a basai ti-
tanosaurian is unknown, but material recently found in the Bajo
ig. 1 9.7. Argentinosaurus huinculensis. Holotyp e, MCF PVPH-1. Postelior dorsal uertebra in lateral uieu. Scale bar: 50 cm. F
Barreal Formation will provide much insight into the cranial anatomy of basal titanosaurids (Martinez 1,998). Deriued titanosaurids. Titanosaurids with dorsal vertebrae lacking the hyposphene-hypantrum complex, and a prespinal lamina extending down to the base of the neural spine, first appear in the upper Cenomanian. Argentinosaurus huinculensis (Fig. 1'9.7) from Plaza Huincul, Neuqu6n Province, and Argyrosdurus superbus from southern Chubut, are huge titanosautids of possible Cenomanian age (however, new evidence suggests that the holotype
forelimb of Argyrosaurws superbus may be Campanian and a questionably referred specimen, PVL 4628, may be Cenomanian; Lamanna, pers. comm. 2003). Argentinosaurus is perhaps the largest sauropod and terrestrial animal ever found. The presence of accessory intervertebral articulations in the dorsal vertebrae (analogous to the hyposphene) and its hollow ribs may be adaptations
for its large size (Bonaparte and Coria 1993). Mazzetta (1999) has estimated the weight of Argentinosdurus as 120 tons. The Senonian (Coniacian-Maastrichtian) of Patagonia is characterized by the presence of numerous derived titanosaurids (Salgado et al. 7997). From the Anacleto Formation comes Antarctosaurus wichmannianus (General Roca, Rio Negro Province; Huene 1,929), Laplatasaurws araukaniczs (Cinco Saltos, Rio Negro Province; Huene 1.929; Powell 1986), l{euquensaurus australis (Cinco Saltos, Rio Negro Province), and Pellegrinisaurus powelli (Lago Pellegrini, Cinco Saltos, Rio Negro Province; Salgado 7996); lrleuquensaurus australis is also known from the Bajo de la Carpa Formation, Neuqu6n City, Neuqu6n Province (Salgado et al., submitted). The Allen Formation has produced Rocasdurus muniozi (Salitral Moreno, Rio Negro Province; Salgado and Azpilicueta 2000). Finalln the Angostura Colorada Formation has produced Aeolosaurus rionegrinus (Ingeniero Jacobacci, Rio Negro Province;
Powell 1986). The evolutionary changes in the skulls of derived titanosaurids include slender teeth and their confinement to the anterior extremity of the mandibles (Coria and Salgado 1999). The attenuation of
440 . Leonardo
Salgado and Rodolfo A. Coria
the teeth commenced with the rise of the titanosaurians, if not earlier (Salgado and Calvo 7997). The slenderness of the teeth and their terminal position in the jaws, also present in diplodocids, are linked to a particular chewing style (Calvo 1994) and to the adoption of a specific diet. The Saltasdurinae.Whrle all cladistic analyses agree on the existence of the Saltasaurinae, they differ in the taxa included in this subgroup (Salgado et aI. 1997,32; Wilson 2002,269). Currently, this clade includes the Patagonian species I'Jeuquensaurus australis (Figs. 19.8, 79.9), RocasAurus muniozi (Salgado and Azpilicueta 2000) (Fig. 19.10), and Sdltasdurus loricatus (from El Brete, Salta Province, northwestern Argentina; Bonaparte and Powell 1980).
g. 1 9.8. Neuquensaurus australis. Leit, skeletal restoration mounted at Museo de La Plata, Argentina; (A) MCS-5/28, right femur, (B)MCS-S, bttmerus, (C) MCS-6, tibia. Scale bar: 70 cm. Fi
lxleuquensaurus australis, one of the species identified by R. Lydekker in 1893, is the best-represented sauropod in the Upper Cretaceous of North Patagonia. Saltasaurines are characterized by the presence of caudal verte-
brae of camellate inner structure ("spongy texrure" of \Tilson 2002). Powell (1986) has pointed out that the bony tissue observed in the dorsal vertebrae of non-saltasaurine titanosaurids has extended caudally in saltasaurines. In Rocasaurus munioTi, the intricate system of inner spaces of the caudal vertebrae is connected with the exterior through small holes (which could be interpreted as true pleurocoels) piercing the ventral and lateral faces of the ver-
tebra (Salgado and Azpilicueta 2000). Although the relative development of cavernous bone has obvious taxonomic value, as discussed by Salgado and Azpilicueta (2000) for R. munioer, there is notable variation within a single taxon, including ontogenerically. Powell (1986,300) understood that the vertebral centra composed by "macrocells" were adaptive, in relation to the lightening of the axial skeleton. An alternative to this explanation is that the camellate texture of the vertebrae is not itself adaptive, but the result of some physiological process that required the mobilization of bony Sauropods of Patagonia
.
441
-
Fig. 19.9. Neuquensaurus australis, MCS-5 /22. P osterior dorsal uertebra in (A) anterior and (B) left lateral uiews. Scale bar: 10 cm.
Fig. 19.10. Rocasaurus muniozi. (A) MPCA-PV-.S6, ischium and Pubis; (B) MPCA-PV-S8, Postelior caudal in left lateral uiew; (C) MPCA-PV-46, holotype, posterior caudttl it right lateral uiew; (D) mid-caudal in uentrdl uiew; and (E) anterior caudal in uentral uiew. Scdle bar: 'l0 cm.
442 . Leonardo
calcium, particularly under situations in which that element cannot be taken directly from food (Salgado 2000). Saltasaurines are among the smallest sauropods (Salgado 2000; Apesteguia 2002a), and they are comparable to dicraeosaurids and Magyarosaurus from the latest Cretaceous of Rumania (Jianu and l7eishampel 7999). There are two aspects about the evolution of size that should be differentiated. One concerns the evolutionary mechanisms responsible for a phyletic decrease in size, and the other is the adaptive benefit for such a reduction. Small size could be positively selected for, or it could simplv be a secondary effect or a by-product of some other process. The evolutionar)' mechanism for size change can be defined in terms of heterochrony, and has been discussed by McKinney and McNamara (1997). In saltasaurines. it is possible that the reduced size is the result of natural
Salgado and Rodolfo A. Coria
selection pressures imposed by the presence of large predators. An-
other explanation for the decrease in size is ecological and associated with life in coastal environments (Apesteguia 2002b). Regardless, paedomorphosis resulted in insular dwarfism in saltasaurines, as it did in other d-uvarf sauropods in Europe, like Magyaroslurus and Ampelosaurus (Jianu and \Teishampel 1999).
Patagonian Sauropod Faunas throughout the Cretaceous Neocomian dinosaur faunas are poorly known in Patagonia (Fig. 19.11). Amargasaurus cazdui reveals the persistence of the dicraeosaurids. whose first representatives are from the Upper Jurassic of Africa (Salgado and Bonaparte 19971.In Lower Cretaceous faunas elsewhere in western Gondwana, Jurassic relicts are a recur-
rent component (Rauhut 7999; Sereno et al. 1999 Canudo and Salgado in press). By the end of the Early Creraceous, riranosauriforms were widely distributed in North America, South America, Eurasia, Australia, and Africa. In Europe, Africa, and South America, they lived along side rebbachisaurids and other basal diplodocoids (Salgado et a1. submitted). Titanosaurian-related sauropods (titanosauriforms more derived than Brachiosdurus, Gomani et aI. 7999,231) r,vere widespread by the end of the Early Cretaceous and were probably the only sauropods in North America and probably in Asia. In Patagonia, titanosaurian-related sauropods appeared in the Aptian (Chubutisaurus insignis fuom Chubut Province; Salgado 1993), whereas the first undoubted titanosaurian (Andesaurus delgadoi) is known from the lower Cenomanian (Calvo and Bonaparte I99 L). The Titanosauridae, with a profuse record in Patagonia, evolved from a group of basal titanosaurians, probably by the lowermost Cretaceous. In Patagonia, the oldest record of a procoelous caudal vertebra (the earliest indisputable titanosaurid) is Cenomanian (Calvo and Salgado 1998). The geographic origin of the Titanosauridae is a matter of debate. Traditionally, they were believed to have originated in Gondawana based on their abundant record in India, Madagascar, and, especially, South America (Powell 1986; Bonaparte and KielanJaworowska 1987). Le Loeuff (1991) considered titanosaurids as a central component of the "Eurogondwana" paleoprovince. Salgado and Calvo (1997), in contrast, suggested that the first titanosaurids lived in Europe, based on the record of Iwticosdurus ualdensis in the Barremian of the Isle of Wight. Sanz et aL. 17999) suggested that titanosaurians originated in "Neopangea," with a strictly Euroamerican lineage (represented lry luticosaurus) and another lineage repre-
sented
by Malawisaurus (these authors do not refer to
the
Titanosauridae but to the Titanosauria, although these two genera are interpreted here as members of Titanosauridae). According to these authors, titanosaurids would have reached Asia from Euramerica during the Barremian-Aptian. Titanosaurids (and ail other sauropods) apparently became extinct in Europe after the Cenomanian, and reentered from Africa in the Late Campanian (Le Loeuff Sauropods of Patagonia
.
443
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199 5; see Wilson and Sereno 1.998
a reply). The European extinction of the titanosaurids coincided
for
with
the extinction of North American sauropods (Lucas and Hunt 1989; Le Loeff 1991).In North America, the decline of the sauropods occurred before the Albian (Wedel et al. 2000). Inexplicably, the midCretaceous extinction of sauropods (by the Cenomanian-Turonian
boundary) in Patagonia seems to have affected basal diplodocoids and many, but not all, groups of titanosaurians. The many genera of derived titanosaurids in the Neuqu6n Basin are the only sauropods recorded above the level of the Huincul Formation (upper Cenomanian), and presumably they evolved from one or more species that survived the extinction. A similar situation occurred in the San Jorge Basin of central Patagonia, where an isolated diplodocoid specimen is recorded as late as the Turonian-Coniacian (Lamanna et al. 2001; Martinez et aI.2001).'We hypothesize that the regional extinction of all sauropods in Europe and North America by the middle of the Cretaceous, and the disappearance of diplodocoids and certain groups of titanosaurians in Patagonia at the same time, are different facets of a single or a series of events occurring on a global scale' The key to understanding this rather dramatic faunal turnover is probably linked to variations of the mid-Cretaceous floras and the decline of many plants that were integrated into the regular diets of these animals (Salgado 2000). The two major groups of sauropods that inhabited Patagonia in the mid-Cretaceous had different masticatory styles that most
likely correlated with different diets (see Calvo 1994). Diplodocoids have slender, cylindrical teeth that are restricted to the front of the snout, whereas basal titanosauriforms have compressed, cone-shaped, chisel-like teeth (Calvo 1999, fig. 10; Sim6n 2001; Sim6n and Calvo 2002). Thus, the mid-Cretaceous floral turnover would have affected the two sauropod groups in different rvays. In northern Patagonia, the youngest record of diplodocoids (upper Cenomanian) come from levels lower than those containing the oldest titanosaurids (Calvo and Salgado 1995). The latter obviously evolved from groups that were present in the mid-Cretaceous (Aptian-Cenomanian interval). Did these middle Cretaceous ancestors have cone-shaped, chisel-like teeth, as do the basal titanosaurids? In other words, did typical titanosaurids acquire a cylindrical dentition once the diplodocoids became extinct, or does the extinction of the diplodocoids predate the expansion and diversifi-
cation of titanosaurids with cylindrical dentition? The occurrence of slender-toothed titanosaurids in the Cenomanian of Africa agrees better with the second interpretation (Kellner and Mader
1997; Rauhst 7999). Upchurch (1995) has suggested that titanosaurids and diplodocoids survived into the Late Cretaceous by having slender teeth and a particular chewing style. However, as already discussed, the dominant group of sauropods with cylindrical teeth during the Lower Cretaceous was the Diplodocoidea (dicraeosaurids and rebbachisaurids). which did not survive into the Late Cretaceous. Sauropods of Patagonia
.
445
Wilson and Sereno (1998) claimed that the slender teeth in sauropods evolved long before the rise of the angiosperms. As they
note, diplodocids of the Late Jurassic already possessed slender teeth with subcircular wear facets perpendicular to the axis of the tooth (Salgado and Calvo 7997; \Wilson and Sereno 1998). \X/edel et al. (2000) claim that the spread of angiosperms is not a satisfactory causal explanation for the exrinction of North American sauropods in the middle Cretaceous. However, if titanosauriforms are considered alone, we see that replacement of taxa having compressed, cone-shaped teeth by forms with cylindrical teeth coincides roughly with the beginning of the rapid expansion of these
plants (Sues and Wing 1992). In Europe, the broad-toothed titanosaurid Ampelosaurus dtdcis (Le Loeuff et al. 7994; this volume) and the slender-toothed Lirainosaurus astibide (Sanz et al. 1999) arc present in the uppermost Cretaceous. Hence, in Europe, uniike in Patagonia, sauropods rvith different feeding styles are present at the end of the Cretaceous. It has yet to be established whether the broad teeth of Ampelosaurus represents the plesiomorphic condition as'Wilson and Sereno (1998) suppose, or; as seems more probable, that it represents a derived state that is autapomorphic of that genus. If rffilson and Sereno are correct, then Ampelosaurus could be a vicariant lineage rhat persisted in Europe from a broader Early or mid-Cretaceous fauna that included Europe, Africa, and Amenca. \il/hat caused the mid-Cretaceous turnover? Lucas and Hunr (1989) have explained the extinction of sauropods in North America as the result of climatic change produced by a regression of the sea that occurred in the late Albian. Extinction affecting both nonmarine and marine faunas at the Cenomanian-Turonian boundary has been recorded in southwestern Utah (Eaton et aL. 1997), and ir may be responsible for the extinction of the North American sauropods. In southern Patagonia, Archangelskv (2001) recorded that, near the beginning of the Aptian, a floral assemblage characterized by the disappearance of the Benettitales and most of the Cvcadales and Ginkgoales was replaced by gleicheniacean ferns. This change in flora cornposition was due to volcanic acrivity that produced environmental changes. \7e hypothesize that toward the end of the Lower Cretaceous and the beginning of the Upper Cretaceous, in Patagonia as well as in continents other than South America, there were successive changes in mean temperatures (with multiple causes) and a concomitant alteration in flora1 comoosition. This resulted in floral turnover that reverberated in rhe sauroood faunas, as weil as in other groups of dinosaurs (F. Novas, pers. comm. 2002). The extinction of the diplodocoids ar the end of the Cenomanian paved the way for the dominance of the titanosaurians, and the radiation of the angiosperms was ar least partiallv responsible for the expansion and diversificarion of titanosaurids with slender, peglike teeth. Derived titanosaurids are abundant in northern Patagonia, but they are scarce in central and southern Patagonia. We do not know
446 . Leonardo
Salgado and Rodolfo A. Coria
if this is due to unequal sampling, the
incompleteness of the fossil record, or ecological factors. Recent discoveries in Chubut (Sciutto and Martinez 7994, UNPSJB-Pv 581; Casal et al. 2002) and Santa Cruz provinces (Novas et al. 2002) seem to support the first alternative. In addition, the Saltasaurinae seem to be restricted, both spatially and chronologicall,v, to the uppermost (Campanian-Maastrichtian) Cretaceous of southern South America. They are found in Rio Negro, Neuqu6n, and the Salta provinces, north of 42" south latitude. Their absence south of 42" is interesting, and although it might be explained by the imperfection of the paleontological record, there is the possibility that the Norpatagonian High had established a barrier that impeded the saltasaurines (Salgado and Azpilicueta 2000). Ho'uvever, Curry Rogers (2002) reported on a probable saltasaurine from the Upper Cretaceous of Madagascar, which would suggest no barrier was present. In Patagonia, saltasaurines are never the exclusive, nor even the dominant, group of sauropods, since in most localities they are associated with other titanosaurids, such as Laplatasaurusu araukdnicus, AntarctosAurus wicbmannianus, Aeolosaurus sp. and Pellegrinisaurus powelli, ar'd other indeterminate species (Garcia and Salgado 2002).
Late Cretaceous Diplodocoids? Many authors (Jacobs et al. 7993; Upchurch 1995; Wilson and Sereno 1998; Sereno et al. 19991 have suggested that Antarctoscturus wichmannidnus, from the Anacleto Formation in Rio Negro Province, is not a titanosaurid, as historically regarded (Huene 1929; Bonaparte and Gasparini 1980; Powell 1986; Salgado and CaIvo 1.997), but is a diplodocoid. Sereno et al. (1999) more precisely suggested that some of the cranial materials of Antarctosdurus wichmannidnus, particularly the lower jaw, belong to a rebbachisaurid based on the lower jaw of Nigersaurus tdqueti. Antarctosaurus and diplodocoids do share characters of the skull including cylindrical, peglike teeth restricted to the anterior extremity of the snout, which \Tilson and Sereno (1998) accept as convergent, but which Jacobs et aL. (1993) do not. Furthermore, both taxa share a symphyseal margin set at a right angle, and a slender basipterygoid process. However, there are characters in the skull of Antarctosaurus that confirm its titanosaurian affinities, including the presence of semilunate paraoccipital processes (Wilson 2002) that are also seen in Saltasattrus loricdtus and Rapetosaurus krausei. It could be argued, then, that the lower jaw of Antarctosdurus wichmannianzs belongs to a rebbachisaurid and that the other parts of the skeleton, including the braincase, pertain to a true titanosaurid. However, the absence of diplodocoid postcranial remains in the Coniacian-Maastrichtian of Patagonia would argue against this alternative. Although no derived titanosaurid with a mandible can resolve this problem of Antarctctsdurus, a new titanosaurid specimen from Rinctin de los Sauces (northern Neuqu6n Province) has a skuli rvith slender, cylindrical teeth restricted to the Sauropods ofPatagonia
.
447
anterior ends of the jaws as in the dipiodocoids (Coria and Salgado 1999, in prep.). Furthermore, this skuil reveals that the degree of convergence in the skulls of titanosaurids and diplodocoids is greater than previously suspected (e.g., Salgado and Calvo 7997). For instance, the quadrate is clearly slanted forward and the infraremporal fenesrra is extended below the orbit as in diplodocoids. These features negate previous statements that the titanosaurid
skull was more similar to that of Brachiosaurws (Salgado and Calvo 1997). Further supporr for this hypothesis is seen with the
skulls of lJemegtosaurus and Quaesitosaurus from the Upper Cretaceous of Mongolia. Although Upchurch (1995, 1999) placed these two taxa within the Diplodocoidea, Salgado and Calvo
to be titanosaurians, and Wilson and Sereno (7998) placed rhem together with the titanosaurians u,ithin (1997) considered them
Macronaria. Elucidating the phylogenetic relationships of these three sauropods, Antarctosaurus, I'tremegtosaurus, and Quaesitoslurus, is crucial because, if they are true titanosaurians, this clade is the only group of posi-Cenomanian sauropods, with the probable exception of an isolated record in the TuronianConiacian of the Chubut Province. This would srrengthen the hypothesis that the mid-Cretaceous extinction would have affected all sauropods with the exceprion of derived titanosaurians. Acknowledgments. We thank S. Apesteguia, K. Carpenrer, O. Rauhut, M. Lamanna, and V. Tidrvell for sharing information and usefui comments. References Cited Apesteguia, S. 2002a. Successional structure in continental tetrapod faunas from Argenrina along the Creraceous. Boletim do 6,, simp6sict sobre o Cretdceo do Brasil/ 2. Simposict sctbre el Cretdcico de Amlrica del Sur, Sao Pedro, Brasil, 135-141. Rio Clar.o, SP, Brazil; DIVISA, Editora e artes grlficas Ltda.
2002b. Greater Gondwana and the Kawas sea coastal tetrapod fauna (Campanian-Maastrichtian). In Boletim do 6,, sintp6sio sobre o Cretdceo do Brasil/2" Simposio sobre el Cretdcicct de Am1rica del Sua 143-147. Rio Claro, SP, Brazil: DIVISA, Editora e artes grdficas Ltda. Apesteguia, S., and O. Gim6nez.2001. A tiranosaur (Sauropoda) from the
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Province, Argentina. Ameghiniana 37, supp. 4R; 4. Archangelsky, S. 2001. Evidences of an Earlv Creraceous floristic change in Patagonia, Argentina. In H6ctor A. Leanza, ed., V1I Internatk:nal Symposiutn on Mesrtzoic Terrestrial Ecosystems, 15-19. pub[caci6n Especial, no. 7. Buenos Aires: Asociaci6n Paleontol6gica Argentina. Bonaparte, J. F. 1986. Les Dinosaures (Carnosaures, Allosaurid6s, Sauropodes, C6tiosaurid6s) du Jurassique Moyen de Cerro C6r.rdor (Chubut, Argentina). Annales de Paldontologie 72: 32j-J86. 1996. Cretaceous Terrapods of Argentina. Miinchner Geowissenscbaftlicbe Abhandlungen, Geologie und Palaeontologie 30:
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Martinez, R. D., M. C. Lamanna, G. Casa1, M. Luna, P. Dodson, C. Tiedemann, and A. Koprovski. 2001. Dinosaurios de la Formaci6n Bajo Barreal, Cret6cico Superior Temprano del sur del Chubut. Ameghiniana38, supp. 12R: 12. Mazzetta, G.V. 1999. Mecdnica locomotora de dinosaurios saurisquios del Cretdcico Sudamericano. Ph.D. dissertation, Universidad de la Repiiblica Oriental del Uruguay. Mclntosh, J. S. 1990. Sauropoda. In D. lfeishampel, P. Dodson, and H. Osm6lska, eds., The Dinosauria, 345-401. Berkeley: University of California Press. Mclntosh, J.S., \7.E. Miller, K.L. Stadtman, and D.D. Gillette.1996. The osteology of Camarasaurus lewisi (Jensen, 1988). BYU Geolctgy Studies 41:73-11,5. McKinnen M. L., and K. J. McNamara. 1.991. Heterochrony: The Euolution of Ontogezy. New York: Plenum Press. Novas, F. E., E. Bellosi, and A. Ambrosio. 2002. Los "Estratos con Dinosaurios" de1 Lago Viedma y Rio La Leona (Cretdcico, Santa Cruz): Sedimentologia y contenido fosilifero. Actas del XV Congreso Geol6gico Argentino 1,: 596-602. Powell, J.E. 1986. Revisi6n de los titanosduridos de Am6rica del Sur. Ph.D. dissertation, Universidad Nacional de Tucumdn. 1987. The Late Cretaceous fauna of Los Alamitos, Patagonia, Argentina. Part 6. The titanosaurids. Reuista del Museo Argentino de Ciencias Nalurales
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1990. Epacbthosaurus sciuttoi (gen. et sp. nov.) un dinosaurio Saurop6do del Cretdcico de Patagonia (Provincia del Chubut, Argentina). Actas V Congreso Argentino de Paleontologia y Bioestratigrafia l: 123-128. Rauhut, O. \)f. M. 1999. A dinosaur fauna from the Late Cretaceous (Cenomanian) of northern Sudan. Paleontologia Africana 35: 61-84. 2002. Los dinosaurios de la Formaci6n Cafrad6n Asfalto. Ameghiniand 39(4\:15R-16R. Rich, T. H., P. Vickers-Rich, O. Gim6nez, R. Crineo, P. Puerta, and R. Yacca. 1,999. A new sauropod dinosaur from Chubut Province, Argentina. In Y. Tomida, T. H. Rich, and P. Vickers-Rich, eds., Proceedings of the Second Gondwanan Dinosaur Symposium, 61-84. Na-
tional Science A,{useum Monograph, no. 15. Tokyo: National Science Museum.
Salgado,
L. 1993. Comments on
Chubutisaurus insignis
Del Corro
(Saurischia; Sauropoda). Ameghiniana 30:26 5-270.
1996. Pellegrinisaurus pouelli nov.gen. et sp. (Sauropoda, Titanosauridae) from the Upper Cretaceous of Lago Pellegrini, norrhwestern Patagonia, Argentina. Ameghiniana 33: 355-365. 1999. The macroevolution of Diplodocimorpha (Dinosauria; Sauropoda): A developmental model. Ameghiniana 36: 203-216. 2000. Evoluci6n y paleobiologia de los saur6podos Titanosaundae. Ph.D. dissertation, Universidad Nacional de La Plata. Salgado, L., and C. Azpilicueta. 2000. Un nuevo saltasaurino (Sauropoda, Titanosauridae) de la Provincia de Rio Negro (Formaci6n Allen, Cretdcico Superior), Patagonia, Argentina. Ameghiniana 37: 259264. Salgado, L., and J. F. Bonaparte. 1991.. Un nuevo saur6podo Dicraeosaundae, Amargasdurus cazctul gen. et sp. nov. de la Formaci6n La
Amarga, Neocomiano de 1a Provincia del Neuqu6n, Argentina. : 333-34 6. Salgado, L., and J. O. Calvo. L992. Cranial osteologv of Amargasaurus cazaui Salgado y Bonaparte (Sauropoda, Dicraeosauridae) from the Ame gh iniana 28
Neocomian of Patagonia. Ameghiniana 29: 337-346. 1,997. Evolution of titanosaurid sauropods. II: The cranial evidence. Ame gh iniana 34 : 33-48. Salgado, L., R. A. Coria, and.f. O. Calvo. 1997. Evolution of tiranosaurid sauropods. I: Phylogenetic analysis based on the postcranial evidence. Ameghiniana 34: 3-32. Salgado, L., and R. D. Martinez. 1.993. Relaciones filogen6ticas de los titanosduridos basales Andesaurus delgadoi v Epachthosaurus sp.
Ameghiniana 30 339.
Sanz, J. L., J. E. Powell, J. Le Loeuff, R.
D. Martinez, and X. Pereda Suber-
biola. 1999. Sauropod remains from the Upper Cretaceous of Laiio (northcentral Spain): Titanosaur phylogenetic relationships. Estudios
del Museo de Ciencias Naturales de Alaua 14 (Niim. Esp. 1): 235-25-5. Sereno, P.C. 1998. A rationale for phylogenetic definitions, with applica-
tions to the higher-level taxonomy of Dinosauria . Neues Jahrbuch fiir Geologie und Paliiontologie Abhandlungen 2I0: 4i-83. Sereno, P. C., A. L. Beck, D. B. Dutheil, H.C.E. Larsson, G. H. Lyon, B. Moussa, R. \J7. Sadleir, C. A. Sidor, D. J. Varricchio, G. P. \filson, and J. A. Xfilson. 1999. Cretaceous sauropods from the Sahara and the uneven rate of skeleral evolution amons dinosaurs. Science 286 1.342-1347.
452 . Leonardo
Saleado and Rodolfo A. Coria
Sciutto, J. C., and R. D. Martinez. 1994. Un nuevo yacimiento fosilifero de la Formaci6n Bajo Barreal (Cret6cico Tardio) y su fauna de saur6podos. Ndturalia Patag6nica, Ciencias de la Tierra 2: 27-47. Sim6n, E.2001. A giant sauropod from the Upper Cretaceous of El Choc6n, Neuqu6n, Argentina. Ameghiniana 38, supp. 19R: 19. Sim6n, E., and J. O. Calvo. 2002. Un primitivo titanosaurio (Sauropoda) del Choc6n, Formaci6n Candeleros (Cenomaniano temprano), Neuqu6n, Argentina. Ameghiniana 39, supp. 77R: L7. Smith, J. B., M. C. Lamanna, K. J. Lacovara, P. Dodson, J. R. Smith, J. C. Poole, R. Giegengack, and Y. Attia. 2001. A giant sauropod dinosaur from an Upper Cretaceous mangrove deposits in Egypt. Science 292:
1704-1706. H.-D., and
Sues,
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L. 'Wing. 1,992. Mesozoic and Early Cenozoic terres-
ecosystems.
In
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K.
Behrensmeyer, J.
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DiMichele, R. Potts, H.-D. Sues, and S. L. 'Wing, eds., Terrestrial Ecosystems through Time, 32741,6. Chicago: University of Chicago Press.
Tidwell, V., K. Carpenteq and S. Meyer. 2001. New Titanosauriform (Sauropoda) from the Poison Strip Member of the Cedar Mountain Formation (Lower Cretaceous), Utah. In D. H. Tanke and K. Carpen-
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eds., Mesozoic Vertebrate Life, 139-165. Bloomington: Indiana University Press. Upchurch, P. 199 5 . The evolutionary history of sauropod dinosaurs. P/rilosophical Transactions of the Royal Society of London 349:365-390. Upchurch, P. 1999. The phylogenetic relationships of the Nemegtosauridae (Saurischia, Sauropoda). lournal of Vertebrate Paleontology 79:1.06-1.25. \fedel, M.J., R. L. Cifelli, and K. Sanders. 2000. Osteologn paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Paleontologica Polonica 45: 343-388. 'Wilson, J. A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Jotrrnal of tbe Linnean Society 136:2I7-276.
Wilson, J. A., and M. T. Carrano. 1,999. Titanosaurs and the origin of "wide-gauge" trackways: A biomechanical and systematic perspective on sauropod locomotion. Paleobiology 25: 252-267. Wilson, J. A., and P.C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Society of Vertebrare Paleontology Memoir, no. 5. Journal of Vertebrate Paleontology 18 (supp. to no. 2): 1-68.
Sauropods of Patagonia
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20. Observations on Cretaceous Sauropods from Austraha RerpH E. MoTNAR AND SrpvpN \7. SerrsBURY
Abstract The Cretaceous record of Australian sauropods from the Albian and Cenomanian of Queensland and New South \Wales includes possibly five taxa, most of which are titanosauriforms. Although some pertain to the Titanosauria, one seems to be a brachiosaurid. Furthermore, some evidence suggests that a non-titanosauriform was also present. No relict sauropod taxa can be presently substantiated in the eastern Australian Cretaceous.
Introduction Sauropod material was first collected in 1913 in Queensland, Australia, from Blackall in the east-central part of the state. Addi-
tional material was sporadically collected in the early 1930s to the late 7970s (Molnar 2000). This material was described by Longman (1933) and Coombs and Molnar (i981). Further sauropod material (not discussed here) has been recently found in central Queensland (Salisbury 2002). So far, all eastern Australian sauropod material (Table 20.1) derives from Albian and Cenomanian 4s4
TABLE 20.1. Australian Cretaceous Sauropod Material Discovered prior to Mid-2000 Specimen
Locality
Stratigraphic unit
Material
QM F6142
Stewart Ck., "Dunraven," near Hughenden, north-central
Toolebuc Fm., Albian
incomplete cervical
QM F13712 QM F40347
near Stewart Ck., "Dunraven"
Toolebuc Fm., Albian ?, Albian?
worn caudal centrum
Allaru Mudstone, Al-
at ieast 7 incomplete
bian
dorsals, rib fragments
unrecorded
6 proximal caudals, middle and 1 distal
Queensland
QM F2316
"Silver Hills," near Richmond, north-central Queensland "Clutha," near Maxwelron, north-central Queensland
QM F2470
unrecorded
QM F3390
"Alni," near \finton, central
QM F6737
QMF7291
QM F7880 QMF7292
l7inton Fm., terminal Aibia n- Cenoma
Queensland
n ia
n
"Lovelle Downs," near ITinton, central Queensland
t{/inton Fm., terminal
"Lovelle Downs"
\Tinton Fm., terminal
Al bian- Cenomani an
Al bia
n - Cenoma
nian
"Elderslie," near 'Winton, cen-
I(/inton Fm., terminal
tral Queensland
Albian- Cenoma n ia n 'Winton Fm., terminal Albian- Cenomania n
"Elderslie"
distal humerus
1
caudal centrum humerus, metacarpals, femur dorsal pieces and proximal and medial caudals, scapula, metacarpals, ischium dorsals, ulna?, meta-
carpal, femur coracoid, incomplete femur dorsal? pieces and proximal caudals, rib fragments, scapula, hu-
meri, ulnae, radii, 4
QM F10916
metacarpals
Chorregon, central Queensland
'$Tinton
Blackall, central Queensland
\Tinton Fm.?, termi-
Fm.?, termi-
nal Albian-
3 proximal and 1 distal caudals
Cenomanian?
QM
F311
incomplete humerus
nal AlbianCenomanian?
QM L380
"Bymount," near Surat, southeast Queensland
AM F66769 AM F66770
Lightning Ridge, northern New South Sflales Lightning Ridge ? (see text)
Griman Creek Fm., Albian Griman Creek Fm., Albian Griman Creek Fm.?,
incomplete ischium isolated tooth isolated tooth
Albian?
(not collected
)
Dampier Peninsula, near Broome, Western Australia
Broome Sandstone, Neocomian
trackways
Observations on Cretaceous Sauropods from Australia
.
455
Fig.20.1. Lateral uiew of one of th e
t'
ert e b ra e
o/ Austrosaurus
mckillopi (QM F2316) showing the btses of seueral laminae. (A) restotittiotl of dorsal, based on Lottgntut's specimen A (modified lirttn \Iolnar,2000). (B) Diagram ol t ettebra, to shou/ laminae. (C) \ e,'r.,pr-,r. leuersed for companson rt t:i 1. f hbret'ialions: acdl = ,7
1".', :' ) 1
Li;::i:-i:
ce
n tr o
,tCPl =
diap op hy seal
, ::.:r,ietl b), matrix; pcdl
=
=
didpop b),se,:tl i-r,'::ti.t tanterior end onlr- seen m c
entr
o
;:,!ebra on right); podl? l'',-.-.ible anterior end
!,'s t )'
go diap op
h y
se
of
=
al lamina;
p,.l I = prezy godiap op hy seal i.i ttt r n a ; sp dl = sp ino diap op hy seal
l:nrirta; x = unndmed ridge c otute cting uith anterior
b y s eal I amina. ing indicates br o ken bone, uertical batcbing indicates nntrtx. Scale bar: 5 cm.
t
o
etttr
Cr
o
s
be re-examined.
Institutional dbbreuiations. AM-Australian Museum, Sydney; DGM-Museum of the Divisio Geologia e Mineralogia, Departamento Nacional de ProduEio Mineral, Rio de Janeiro; and QMQueensland Museum, Brisbane.
dnterior
tet::,' ,L.trtPoPhyseal lamina; d p,;5;1,tia;l position of missing .i;;r' pl:r -si-s' P = pleurocoel,
I .-(:.ror
units (Dettmann et a|.7992). Previously, these specimens were referred to the Cetiosauridae (Longman 1933 Coombs and Molnar 1981). Recent work, however, indicates that most or all of this material pertains to titanosauriforms (Salgado 1993; Salgado and Calvo 7997; Molnar 2000). This contribution presents the results of work on this material subsequent to Coombs and Molnar (1981) and Molnar (2000), of particular significance in regard to the taxonomic conclusions reached in those papers. In addition, although no evidence was available to indicate that more than a single taxon was represented among the Queensland sauropod material previously studied, other material, new observations, and recent studies (e.g. \Tilson 2002) indicate that this issue needs to
diap op
s-h atch
Description
Albian material. Austrosaurws mckillopi is the only named sauropod from the eastern Australian Cretaceous (Longman 1933). It is represented mainly by incomplete dorsal vertebrae (QM F231,6) from the Allaru Mudstone, near Maxwelton, north-central Queensland. Longman's (1933) description mentioned three individual blocks, but in June 1933, after his publication, five large and more than ten small further pieces were received, thus at least eight vertebrae are known. One of these more recently discovered specimens, a dorsal vertebra (Fig.20.1) has the most complete laminae of this specimen. The incompleteness of the material makes identification of the laminae difficult as the nomenclature is based on the structures connected by the laminae (\Tilson 1,999). Furthermore, it
-\;pcdr a:\ 1\,
l\
456
.
Ralph E. Molnar and Steven 'i7. Salisbury
is unclear which end of the specimen is anterior. Longman's specimen A retains the ventral portions of three laminae (Longman 1933, pl. 15), which appear to be the anterior centroparapophyseal lamina (acpl) anteriorly, the anrerior centrodiapophyseal lamina (acdl) behind it (weathered to a low ridge), and the posterior centrodiapophyseal lamina (pcdl) angled into the posterior break (Fig. 20.1). These identifications, although plausible, are renrarive because the dorsal ends of the laminae are not preserved. These laminae seem to have been shallow, although the amount of weathering makes this impossible to confirm. Comparing the "new" vertebra with the laminar pattern of specimen A, and assuming that the identifications rhere are correct, suggests that the right side is seen in Figure 20.1, and the laminae present are the anterior and posterior centrodiapophyseal laminae, the prezygodiapophyseal lamina (prdl), and base of the spinodiapophyseal lamina (spdl) and possibly the anterior end of the postzygadiapophyseal lamina (podl). The posterior centrodiapophyseal lamina is represented only by its anterior termination at the (nolv lost) diapophysis. These observations support the phylogeneric placement of A. mckillopi as a member of the Titanosauria (Molnar 2000). Unidentifiable titanosaurid material includes QM F2470, consisting of six proximal caudals preserved as three pairs, rvith one middle and one distal caudal. The specimen came from an unrecorded locality probably in north-central Queensland (Molnar 2000). That six of the vertebrae were found as pairs indicates that this specimen was at least partially articulated when buried (Figs. 20.2,20.3,).In addition the chevrons remain in articulation. The general form of the vertebrae are shown in Figures 20.2 and 20.3. The neural arches are positioned anteriorly on rhe anterior caudals, and hence presumably also on the middle and posterior caudals. Neither laminae nor pleurocoels are present. The centra are amphicoelous and. in anrerior view. taper venrrally. The rario of rheir Iength to their height is about 0.6. At breaks, cancellous internal structure is revealed, but not the spongy bone found in eM F23I6 and QM F6737. The proximal articular facets of the chevrons are not joined by horizontal bars of bone. The middle caudal cenrrum is clearly depressed with dorsoventrally convex sides, the distal centrum less so. The ventral surfaces of the caudals are shallorviy ex, cavated, with each fossa bounded by a venrrolareral ridge on each side. Assuming rhese all represent a single individual, which is consistent with their relative sizes, the lengths of centra increase posteriorly. Molnar (2000) conciuded on rhe basis of the caudal vertebral character states that this specimen represents a titanosaurid. The analysis of Wilson (2002) would place this as probably a mem-
Lig. 20.2. Articulated anterior caudals of the titanosaurid indet.
(QM F2470), probably from near Ric b mond, nortb - central
Queertsland (see text), with cheuron. Scale bar: 5 cm.
ber of the Titanosauria from the presence of ventral longitudinal sulci on the anterior and middle caudals and the absence of forked chevrons.
QM F40347 is the distal part of a left humerus (Fig. 20.4), from the Toolebuc Formation, near Richmond, north-central Queensland. The radial condyle is prominent, but the ulnar condyle Observations on Cretaceous Saulopods from Australia
.
457
H
H Fig. 20.3. Associated dtfierior caudals of the titanosaurid indet.
(QM F2170) that are
less
displaced than those of Figure 20.7. Left, posterior uiew; right,
right latrrol uirw..\calc hnr: I cnt.
is not apparent anteriorly. Both condyles are prominent posteriorly,
with a well-developed olecranal fossa extending from the distal end. The bone flares distalll', so that the maximum width across the epicondyles is more than 1.5 times the transverse diameter at the break. The distal end is flat, presumably perpendicular to the long axis of the shaft. Although previous workers (Upchurch 1995, 1998; Salgado and Calvo 1.997; Salgado et al. 1997; 'Wilson and Sereno 1998) do not use humeral characters or only those of the 'S7ilson (2002) recognizes two from the distal end proximal region, of the humerus. One of the condyles is clearly anteriorly exposed in this specimen, and is a derived character state according to \Tilson
(2002), and the distal margin, at least in anterior and posterior vielvs, is flat. The latter character diagnoses sauropods, but the former, diagnoses an unnamed clade of the Titanosauria (including nemegtosaurids and saltasaurids).
Trvo teeth, one (AM F66769) certainly and one (AM F66770)
458 . Ralph
E. Molnar and Steven
!/.
Salisbury
Fig.20.1. The distal left humerus uI an indelcrnrtnatc litdnosaurian (QM F10347) found near Rich mond, north -c entral Quccnslarrd. !A, Ct onterior t'iL'u ; (8, D) posterioT ltist!; (E) distal uiew; (F) medial uiew. Scdle bar: 20 cm.
Fig.20.5. Sauropod teeth from the Griman Creek Fonnation dt Lightning Ridge, nrtrthern New South Wales. (A) Titanosauriform indet. (AM F66769) in mesiodistdl and lingual uiews; (B)
@ g
E E
x g
J"
T itanosaur iiorrn ( ) in det. ( AM F66770) in mesiodistal and Lingual uieus. Scale bar: I cm. ?
probably from the Griman Creek Formation (Albian) at Lightning Ridge, New South '$7ales, are ritanosauriform. AM F66770 rncludes the crown and upper part of the root, about two-thirds as long as the crown (Fig.20.5B). AMF66769 comprises the crown and upper part of the root, about as long as the crown (Fig. 20.5A). The tips of both are incomplete, presumably from wear. Both teeth are preserved in miiky, pale blue and nonprecious green opal
("potch")
as pseudomorphs.
Observations on Cretaceous Sauropods from Australia
.
459
Tlre upper half of the crown of AM F66770, in mesiodistal view, is flexed lingually at about 25o, and the labial margin of the crown is bulbous and more strongly curved than the lingual (Fig. 20.5B). This labial face is strongly convex, and the broad lingual face is concave with a slightly curved, strong central ridge. The labial face erhibits shallow grooves along the mesial and distal margins. The crown has an almost semicircular form in section. A distinct neck, marked lingually by a rvell-defined narrow groove, joins the crown to the cylindrical root. There is no indication of marginal denticles. A mesiodistal view shows 80% of the crown of
AM
F66769 is flexed lingually at about 20" (Fig. 20.5A). The crown is rounded polygonal in section, with a flattened, but narrow, lingual face. The neck is larger than the crown, but abruptly constricts to the faceted root. As in AM F66770, mar:ginal denticles are absent. In AM F66770 the wear facet at the tip, viewed mesiodistally, is inciined at about 45o to the labio-lingual axis. Salgado and CaIvo (1997) suggest that such wear is synapomorphic for the titanosauriforms. The crown of AM F66769, although narrow, is not "pencil-1ike" in the sense used to describe the teeth of Diplodocus. Applying the characters of Upchurch (1998), the "parallel-sided" form of the crown (K2) indicates that it derives from the radiation including Brdcbiosaurus, Lapparentosdurus, P huwian gosaurus, and the titanosaurians, in other words, the Titanosauriformes of Wilson and Sereno (1998).It is possible that both teeth (AMF66769 andF66770) derive from the same taxon, but there is no evidence to support this and, if so, this sauropod would have had an unusually wide range of variation in tooth form. A single, incomplete cervical vertebra (QM F6142) from the Toolebuc Formation, near Hughenden, in north-central Queensland, may represent a brachiosaurid titanosauriform (Fig. 20.6). The vertebra is represented only by its posterior portion. This specimen was mentioned by Coombs and Molnar (1981) and figured by Molnar (1991). The deepiy concave, dorsoventrally compressed, posterior, central articular face is ventrally and laterally flared. At the anterior break, the centrum is deeply excavated ventrally and edged with obliquely descending ridges. The spinopostzygapophyseal lamina is inclined at about 45" in lateral view (assuming the posterior, central articular face to be vertical). The postzygapophyseal facets are inclined at about 25' to the horizontal. The postzygapophyseal processes are separated by a deep fossa. The deep pleurocoel is divided by an almost horizontal lamina. The posterior end of the pleurocoel is beneath the postzygapophyseal facet.
Two character states of Upchurch (1998) are present, deep pleurocoels in cervical centra and cervical vertebrae with concave ventral surfaces. The infradiapophyseal lamina system is probably present on cranial and middle cervical vertebrae (Upchurch's infradiapophyseal lamina corresponds to Wilson's [1999] posterior centrodiapophyseal lamina). The presence of accessory oblique lamina in cervical pleurocoeis is unclear, because the lamina in QM F6742 460 . Ralph E. Molnar and Steven
S7.
Salisbury
Fig. 20.6. The posterior pdrt of the ceruical of a ?brttchiosaurid indet. (QM F61-+2), from near Hu gh end erq north - c erir al Qtteensland: (A) right lateral uiett'; ,B,lcft Itteral t icu': rCt pr6!svir'v
uieu; (D) tieu' ctf the anterior ltrtak. lrr D. tlsc cradle srrfporring the specimen can be seen beneath the centrum. Scale bar: 10 cm.
l_d is oriented quite differently from that figured by Upchurch (1998, fig. 8). However, a similar horizontal lamina is present in the last cervical of Brachiosaurus brancal (Janensch 1950, fig. 49). Three '!Tilson states of and Sereno (1998) are clearly or plausibly present: cervical centra opisthocoelous; mid-cervical neural arches deep, greater than centrum diameter; and cervical pleurocoels divided.
'Wilson
(2002) diagnoses the Titanosauria as having undivided cer-
vical pleurocoels, which indicates that this specimen does not derive from a titanosaurian because the centrum has complex pleurocoels divided by bony septa (83). Neither has this specimen the bifid neural spine characteristic of diplodocids and dicraeosaurids. This, combined with the results of Upchurch (1998), suggests that this cervical represents a brachiosaurid.
Late Albian-Cenomdnian mdterial. Several specimens, almost
all described and figured b.v Coombs and Molnar (1981),
have
been recovered from the'Winton Formation near \il/inton. central
Observations on Cretaceous Saurooods fron-r Australia
.
461
Queensland. These have been generall,v attributed to Austrosaurus sp. QM F3390, consisting of a humerus and femur, both represented by proximal and distal ends not sharing a contacr, and the proximal ends of three metacarpals (Coombs and Molnar 1981, pls. 3 and 6). The articular surfaces, especially those of the proxrmal part of the humerus, are probably the best preserved of the Queensland sauropod material. The form of the prorimal end of the humerus is not matched by any of those figured by Mclntosh (1990, fig. 16.10). The well-developed internal tuberosity, or proximomediai corner, is characteristic of sornphospondyls (Wilson 2002). The proximal bulge of the lateral margin of the femur is considered by Salgado et a|. (1997; \filson 2002) as indicaring a member of the Titanosauriformes. Several specimens are ritanosaurian, but also represent a single taxon or closely related taxa. A series of incomplete dorsais, proxrmal and middle caudals, pieces of ribs, an incomplere scapula, and the proximal part of an ischium are from one individual (QM F6737). Oddln although anterior parts of the dorsal centra were collected, there is no indication of any posterior portions. Three roughly discoid pieces of bone are taken to represent anterior portions of dorsal centra. These pieces have a shallowly convex arricular surface forming one side of the "disk," the orher being a broken surface. This break shows evidence of pleurocoels (character 8 of Salgado et aL. 1997; character 68 of Wilson and Sereno 1998), between rvhich is spongv bone (Fig. 20.7) (character 102 of ril/ilson and Sereno 1998). The conver articular faces and the pleurocoels are taken to indicate that these pieces represent parts of opistho-
coelous dorsal centra (characters 1 and 9 of Salgado et al. 1997\. Opisthocoelous dorsals are also knorvn for QM F2316. QM F6737 and QM F10916 have centrum length divided by centrum height approximately 0.5-0.6 (character C27 of Upchurch 1998). More imporrantll', rhe ventral surfaces of cranial caudal centra of eM F6737 and QM F2470 are mildly excavated, with the excavarion bounded by a venrrolateral ridge on each side (character Q5 of Upchurch 1998). The centra of middle caudals display a dorsoventrally compressed transverse cross-section (character p1 of Upchurch 1998), and the neural arches are positioned anteriorl.v in mid- and posterior caudal centra (character 1S of Salgado et al. 1997\. Two specimens were recovered from "Elderslie" (Coombs and Moinar 1981). QMF7292 is the most complete of the eueensland Cretaceous sauropod specimens, including pieces of ribs, seventeen middle and distal caudals, an incomplete scapula, substantial parts of both humeri, both radii and both uinae, and four metacarpals (Coombs and Molnar 1981, pls. 7-4,6). The characters indicate a titanosaurian (\Tilson 2002). Expansion of the distal end of the radius to twice the midshaft diameter characterizes a clade within the Titanosauria. The second specimen from "Elderslie," QM F7880, is substantially less complete than QM F72792.It consists onlr. of an incom-
462
.
Ralph E. Molnar and Steven \X/. Salisbury
xrl
t6
\1
t*'**-s
#.* \B
-.,-t
r)r), n rr rJ t0
*t r,
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r b{J{ r
nryAq
Fig. 20.7. Anterior part of a dorsal centrutn of an indeterminate titanosaurid (QM F5737), from "Louelle Dotuns," nctr Winton, cortral Qtteensltnd, together u,ith the same pdrt of Austrosaurus mckitlopi (QM F2316, holot.^,,pe). Aboue, right lttcrtl uicws: beloru. I,re'ken [aces, seen from behind. In the lateral uiews, the arrous mark the anterior margins of the pleurocoels. In the posterior uiews, tbe curued drrows mark the right pleurocoels, and the broad arroa,s indicate the positictn of the nettral canol ,fillcd with tnatrix in QM I-2316). ln QM F6737 the surficial bone remains, btx in QM F2llo tt bds hccn Iost. leauing only the calcdreous fill of the interndl cduities. The spctng; internal structure of the centrum rntt\ be seen in hoth specimens, Scole bar: 5 cm.
plete femoral head and an incomplete coracoid. Although the femoral head is uninformative, the coracoid is elongate. An elongate coracoid, about twice the length of the scapular contact surface, is characteristic of a clade u'ithin the Titanosauria (Wilson 2002).
QM F10916 is from Chorregon, central Queensland, and is most probabl,v frorn the \Tinton Formation. Three incomplete proximal caudals, and one more distal caudal, make up this specimen (Fig. 20.8). A1l the centra are amphicoelous and show some degree of constriction. The ventral surfaces of the anterior elements bear longitudinal sulci, bounded by prominent ridges, and are probabll' Tiranosauria. Other sdtrropod materia/. A specimen from "Lovelle Downs," QMF7291, consists of a metacarpal, distal femur; and unidentified fragments (Coombs and Molnar 1981, pls.5 and 6), one of which was suggested by Coombs and Molnar (1981, pl.5C, D) to possibly be the proximal end of an ulna. The distal surface of metacarpal I has two condyles. The preserved part of the femur of this specimen appears comparable in form to the distal part of that of Q\,I F3390, but is about one-third larger. Thus this specimen is one of the larger of the Queensland sauropods. The existence of two condyles, on the phalangeal articular face of metacarpal I, suggests that this specimen is not a titanosauriform (Wilson2002). Observations on Cretaceous Sauropods from Australia
.
463
Fig. 20.8. A distal caudal of a titanosauridn indet. (QM F10916), from near Chorreg,ttt, central Q.ueensland, in presumed left lateral (left1 and dr,;rsal (right) uietus. Scale bar: 70 cm,
l-t Conclusions Is more than a single taxon represented bv the eastern Australian Cretaceous sauropod material? The transverse processes of the proximai caudal are substantially deeper in QM F7292 than in
QM F2470, QM F6737, or QM F70976. Furthermore, the centra of QM F7292 are noticeably broader than those of the other three specimens. This may be merely due to different verrebrae being preserved in these four specimens, bur it could also indicate taxonomic difference. In QM F2470 and QM F6737 the lengths of the caudals increase posteriorly, but in QM F7292 they decrease posteriorly. The evidence is incomplete, but the difference in trends in lengths of the caudal centra, matched by the difference in proximal caudal form in the same specimens, suggest that at least two sauropod taxa are represented in the Winton material. There appear to have been nvo sauropod taxa during the pre-XTinton time (Albian), Azstrosdurus and a possible Brachiosauridae, and probably three dur'Winton ing the tirne, two of them titanosaurians. The argument of Moinar (2000) and the evidence presented here shows that Australia can no longer be regarded as the only Gondwanan continent without titanosaurids, and that there is no evidence for relict, plesiomorphic sauropods in the Australian Cretaceous. But Australia does seem to lack any advanced titanosaurids with procoelous caudals, at least through the Cenomanian. Acknctwledgments. \We particularly appreciate assistance during various aspects of this project by Graham Anderson (Lightning Ridge), Laurie Beirne (Queensland Museum), Sandy Swift (Northern Arizona University), Tony Thulborn (Monash University), Mary \7ade (then at the Queensland Museum), and Zhou X.-T. (Academia Sinica). References Cited
Coombs,
'W.
P., Jr., and R. E. Molnar. 1981. Sauropoda (Reptilia,
from the Cretaceous of Queensland. Memoirs of the Queensland Museum 20: 351-373. Dettmann, M. E., R. E. Molnar, J. G. Douglas, D. Burger, C. Fielding, H. T. Clifford, J. Francis, P. Jell, T. Rich, \,{. Sfade, P. V. Rich, N. Pledge, A. I(emp, and A. Rozef elds. L992. Australian Cretaceous terSaurischia)
464 . Ralph E. Molnar and
Steven
\7. Salisburv
restrial faunas and floras: Biostratigraphic and biogeographic implications. Cretdceous Research 13: 207 -262. Janensch, !7. 1950. Die \Tirbelsdule von Brachiosdurus brancai. Palaeontographica, supp. 7(3) 2:27-93. Longman, H. A. 1933. A new dinosaur from rhe Queensland Cretaceous. Memoirs of the Queensland Museum 1,0: 131,-144. Mclntosh, J. S. 1990. Sauropoda. In D. B. Veishampel, P. Dodson, and H. Osm6iska, eds., The Dinosauria, 345-401. Berkeley: University of
California
Press.
Molnar, R. E. 1991. Fossil reptiles in Australia. In P. Vickers-Rich, J. M. Monaghan, R. F. Baird, T. H. Rich, E. M. Thompson, and C. 'Williams, eds., Vertebrate Pdlaeontology of Australasia, 605-702. Melbourne: Pioneer Design Studio and Monash University Publications Committee.
2000. A reassessment of the phylogenetic position of Cretaceous sauropod dinosaurs from Queensland, Australia. In H. A. Leanza, ed., VII International Symposium on Mesozoic Terrestrial Ecosystems, 139-144. Asociacion Paleontologica Argentina Publicacion Especial, no. 7. Buenos Aires: Asociacion Paleontologica Argentina. Salgado,
L. 1993. Comments of
Chubutisaurtts insignis
Del Corro
(Saurischia, Sauropoda). Ameghiniana 30: 265-270. Salgado, L., and J. O. Calvo, 1997. Evolution of titanosaurid sauropods. II: The cranial evidence. Ameghiniana 34:33-48. Salgado, L., R. A. Coria, and J. O. Calvo. L997. Evolution of titanosaurid sauropods. I: Phylogenetic analysis based on the postcranial evidence.
Ameghiniana 34:3-32. Salisbury, S. 2002. Clash of the titans. Nature Australia 27(7): 44-51,.
Upchurch, P. L99 5 . The evolutionary history of sauropod dinosaurs. Pbllosophical Transactions of the Royal Society, London 349 365-390. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of the Linnean Society 724 43-703. 'Wilson, J. A. 1999. A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs. Journal of Vertebrate Palectntoktgy
19 639-653.
2002. Sauropod dinosaur phylogeny: Critique and cladistic analyJournal ofthe Linnean Society 136 215-275. 'Wilson, A., and P. C. Sereno 1,998. Early Euolution and Higher-Leuel J. Phylogeny of Sauropod Dinosaurs. Society of Vertebrate Paleontology Memoir, no. 5. Chicago: Society of Vertebrate Paieontology. sis. Zoological
Observations on Cretaceous Sauropods from Austraiia
.
465
2t. Late Cretaceous (Maastrichtian) Nests, Eggr, and Dung Mass (Coprolites) of Sauropods (Titanosaurs) from India D. M. MoHeeEy
Abstract Late Cretaceous dinosaurs from India are represented by at least twenty species of sauropods, theropods and, ornithopods. The dinosaur fauna is dominated by a titanosaurid and abelisaurid as'Well-preserved
dinosaur nesting sites, clutches, and eggs are abundant in the dinosaur skeleton bearing Upper Cretaceous Lameta sediments in central and western India. No dinosaur eggs are so far known from the pre-Cretaceous sediments in India. A majority of the Indian Late Cretaceous eggs have been assigned to oofamily Megaloolithidae, believed to be of titanosaurs. At least eight Megaloolithus oospecies have been established, Nesting and social behavior of the titanosaurs is inferred from eggs, nests, and nesting sites. Evidence suggests community nesting along the riverbank with the eggs buried in the river sand. Recently, weil-preserved, large-sized (diameter up to 100 mm) coprolites containing undigested plant tissues, pollen grains, spores, and other ingested organic matter have been found. The coprolites occur in association with skeletal remains of Titanosaurus indicus, T. blandfordl, and pelomedusid turtles. Based on the large semblage.
466
size of the coprolites, their association with titanosaur skeletal remains, and the occurrence of prolific plant tissues in the fecal mass, the coprolites of Type-A are assigned to titanosaurs. The floral analysis of the coprolitic mass has provided insight into the dietary habit of the titanosaurs. The evidence suggests that titanosaurs preferred cropping the soft tissues of higher plants such as pteridophytes, gymnosperms, and angiosperms as their main solid diet. The study of the Indian sauropod eggs, nesrs, and coprolites has shown that the Indian Late Cretaceous ecosystem offered an ideal habitat for titanosaurs wherein they reached the acme of their breeding and nesting. The prolific occurrence of the skeletal remains, eggs, and dung mass of titanosaurs in the Maastrichtian ecosystem
of India and their total absence in the older sediments
suggests a sudden turnover during the Lameta time, and was a pre-
lude to their extinction just before the Cretaceous-Tertiary Boundary (KTB) with the advent of Deccan volcanic eruprion.
Introduction The earliest report of sauropod skeletal remains in India is by Hislop (1859). The material r,vas collected from the Upper Creraceous (Maastrichtian) Lameta Formation of Pisdura in central India (Fig. 21.1).ln contrast, the report of sauropod eggs is more recent, with the first discoveries in 1981 (Mohabey 1983) from the Lameta Formation of the Kheda area in Gujarat in western India (Fig. 21.1). The Late Cretaceous dinosaur fauna of India is represented by sauropods (titanosaurs), theropods (abelisaurids, allosaurids, coelurosaurs), and questionably identified ornithischians (sregosaur
Drauidosaurus blandfordi and Brachypodosaurus grauis\. Although Lydekker established the sauropod genus Titanosaurus in 1877 (Lydekker 7877,1879),little is known about the species because of the fragmentary narure of its skeletal remains. Most of the taxonomy of the Indian Titanosaurus species is based on vertebral systematics that form the diagnostic characteristics (Huene and Matley 1933). The named species are Titanosaurus indicus (Lydekker 1877), Titanosaurus blandfordi (Lydekker 1879), Antarctosdurus septentrionalis, Laplatasaurus madagascariensis (Huene and Matley 1933), and Isisaurus colberti (Jain and Bandyopadhya 1997; \X/ilson and Upchurch 2003). Not all of these species are considered valid (Jain and Bandyopadhyay 1997;Wllson and Upchurch 2003). Of all the sauropod specimens, the holotype of I. colberti represents the best species among the Indian titanosaurs described to date. Since the discovery of dinosaur eggs in India, a large number of dinosaur nesting sites with well-preserved eggs have been located in the Lameta Formation in western India (Mohabey 1984a, 1987; Srivastava et al. 1986; Mohabey and Mathur 1989) and central India (Sahni and Tripathi 1990; Mohabey 1990, 1996a; Khosla and Sahni 1995). Though the dinosaur skeletal remains are well documented from the pre-Cretaceous sediments in India, no eggs Late Cretaceous Nests, Eggs, and Dung Mass of Sauropods ftom India
.
467
/'
t,Joiaat..,
l
(.
\
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t@".9 ,) i,^ -' ' .{.0.,^g3 _ ,1.,-, \llobd1.dq Bhopor @- S4; -' ;|l )' " Ft"j'i't1-:"r".*g g^r*:l'--oo'*',, a.o=,
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e
Nesting sates (Megoloolilhido. eggs of f itonosours)
uctrctriroirot ti
{9
(Elongotoolithidoe eggs of obclisourids)
r\
A single
H
Cretoceouo titonosours skclcton sitas
- -./ Kollom.du a AriYolu' .O
?a )rir
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g
x Fig. 21.1. Geological map showing important dinosaur fossil Iocalities in lndia.
2OOKm
,:<
i.
i..
IOO
N€sling silcs egg (McAolooliihidoc)
Souropod coprolites
Pre-Creioceous dinosour skclclon sitcs
are known. A remarkable diversity is present among the eggshells
(Mohabey 1.998a, and references therein; 2001a). Based on their general morphology and histostructure, the eggshells have been parataxonomically assigned to eight oospecies of Megaloolithus (Megaloolithidae) and one to the oogenus Ellipsoolithus (Elongatoolithidae) (Mohabey 1991, 1996a, 1998a). The eggshells were also studied for their stable carbon and oxygen isotope composition to obtain information on ecology and food habits (Sarkar et aL 1991).
Recently, abundant coprolites have been found in the Lameta sediments of Pisdura (Mohabey 2001a,2001b). These coprolites have been attributed to titanosaurs based on their large size (up to
468
.
D. M. Mohabey
100 mm), the presence of abundant plant tissues, and their association with the skeletal remains of titanosaurs. Matley (1939) made the first-time collection of coprolites which he divided into four types, but he reported them devoid of any organic matter. Mohabey (2001b) reported prolific coprolitic mass of Matley's Type-A that was enriched in tissues of pteridophytes, gymnosperms, and angrosperms.
Geological Setting and Depositional Environment The dinosaur-bearing sediments of the Lameta Formation (also called the infra-trappeans) occur below the Deccan volcanic sequence. The Lameta Formation (Maastrichtian) rests unconformably over the Precambrian or Gondwana Supergroup of rocks and occupies over 5,000 square kilometers, mostly as detached outcrops in western and central India (Fig. 21.1). The sediments were deposited in different basins (Mohabey 1996b).In the Kheda area of Gujarat, the sediments were deposited during magnetochron (30N), whereas in the Jabalpur area in Madhya Pradesh and the Nand-Dongargaon area of Maharashtra, they were deposited during 29R (Hansen et al. 2001). These ages demonstrate that the Lameta sediments are diachronous, with older sediments deposited to the northwest and younger sediments to the south. The most important Lameta localities (Fig. 21.1), which have yielded dinosaur skeletal remains, eggs, and nests, are (1) the NandDongargaon basin in Maharashtra in central India, (2) the Kheda and Panchmahal areas of Gujarat in western India, (3) the Jabalpur and Bagh areas of Madhya Pradesh in central India, and (4) Ariyalur in southern India. 1.. Nand-Dongargaon localities (Fig. 21.1). The litho- and biofacies analysis of the Lameta sediments of the Nand-Dongargaon Basin indicates that the sediments were deposited in alluvial-limnic environments under semiarid conditions (Mohabey et al. 1993; Mohabey 1996b; Mohabey and Udhoji 1996). Different lithofacies representing channel, overbank, lacustrine, and palustrine environments have been identified. The biota represents terrestrial, semi-
aquatic, and aquatic communities, and is composed of dinosaurs, chelonians, crocodiles, fishes, gastropods, ostracodes, charophytes, gymnosperms, and angiosperms (Mohabey et al. 1993). The sauropods are represented by Titanosaurus indicus, T. blandfordi, l. colberti, Antarctosaurus septentrionalis, and Laplatosdurus madagascariensis (H:uene and Matley 1933; Jain and Bandyopadhyay 1997). The skeletons are reworked and in a mayority of cases occur in overbank red and green clay facies and occasionally as lag accumulations associated with paleosols (Mohabey et al. 1993; Mohabey 1996b). Coprolites occur in a thin, discrete, marly layer within the red overbank clays in a couple of localities, including Pisdura. Dinosaur nests and eggs are found in sandy calcrete facies and channel sandstones (Mohabey 1996a, 1998b, 1999,2000b). Rare eggshell fragments are found in the Late Cretaceous Nests, Eggs, and Dung Mass of Sauropods from
India . 469
Fig. 21.2. Nests of satrroltods in Lameta Fonnation of KhedaPdnchLultdhdls area, Gujarat. (A) Nest irom Rahioli showing eggs, Megaloolithus rahioliensis, disposed in :t circular fashion surrcsuttdlttg d single egg at the center. lB) )test irom Dlsu,idtrttgrt. shnu ing lu u eggs
oI
NI. dhoridungriens:.s and e ggsb ell debris ittsirle ;rnd outside the eggs. /C, Ne-(t fronr Garadu t,ith eggs and eggsl:ell dehris of \L. phens:rniensis. \.) specific pdttern of eggs presertt ln the nest. (D) Llrte,tr rou' of Megaloolithus rahioliensis eggs from Rahioli.
overbank clays (Jain and Sahni 1985; Vianey-Liaud et aL 1987; Mohabey 1990; Mohabey 2001a). 2. Kbeda-Panchmdhdls localities. These localities have the iargest number of Indian sauropod nesting sites (more than fifteen), and have the largest number of well-preserved nests and eggs (Fig. 21.2). The Lameta sediments were deposited in the Narmada rift zone (Acharn/a and Lahiri 1991'). The basal conglomerate is a major dinosaur bone-yielding horizon at Rahioli. It has produced abundant, well-preserved, semiarticulated, and disarticulated skeletal remains of titanosaurid and abelisaurid dinosaurs (Dwivedi et al. 7982; Mathur and Pant 7987; Mathur and Srivastava 1987; Mohabey 2001a). The conglomerate grades into a pebbly sandstone, bearing abelisaurid and titanosaurid skeletal remains at certain levels. The sandstone facies grades both vertically and laterally into a carbonate facies represented by calcretes and palustrine flat carbonates (Mohabey 1991, 1.998a; Srivastava et al. 1986; Mohabey and Mathur 1989). A malority of dinosaur nests and eggs occur in the sandy calcrete subfacies (Mohabey 7984a, 1,990,7991., 1998a).
3. The labalpur and Bagh dreds. Dinosaur bones from the Lameta Formation of Jabalpur (Fig. 21.1) are mostly known from the Bara Simla locality (Huene and Matley 1933). The skeletal remains are found at three stratigraphic levels (Matley 1921; Huene and Matley 1,933). The basal Carnosaur Bed at the contact between the lowermost Green Sandstone and Lower Limestone con-
470 . D. \1. Mohabey
tains bones of carnosaurs, together with coelurosaurs
and stegosaurs (Huene and Matley 1933). The middle ossiferous con-
glomerate, containing reworked and broken bones mostly of sauropods, is at the top of the Lower Limestone. The uppermost ossiferous Sauropod Bed, which contains reworked and- broken bones of more than one sauropod genus, occurs in the red and green sandy clays in the basal part of the Mottled Nodular Bed. The sauropod nests are found in the Lower Limestone. Tandon and coworkers in recent years (Tandon et aL 1995, 1998; Sahni et al. 1994 Tandon 2000) have given a very detailed anal,vsis of the sedimentary facies of the Lameta sediments. They demonstrate that these sediments are characteristic of a fluvial and semiarid, pedogenically modified fan-palustrine flat system. The drnosaur egg and nest-bearing facies show local variation and represent either subaerially exposed palusrrine flats or proximar fan surface deposits. Based on a sedimentary pulse partern represenring Milankovitch pulses, as shown by the magnetic susceptibility, and stable carbon isotope stratigraphy, Hansen et at. (1996; 2001) demonstrated that at chui Hill the Lameta sedimenrs on the top of Green Sand were deposited over a period of 400-450 ky. The Lameta Formation of the Bagh area overlies the sediments of the Bagh Formation (Turonian). The Lameta sediments are exposed over a distance of 400 km in the lower reaches of the Narmada Valley in western India, covering parts of Gujarat and Madhya Pradesh (Singh and Srivastava !981; Khosla and Sahni 1995; Kumar et al. 7999 Tandon 2000). The sediments occur persistently
as a thin shelf below the Deccan Traps in the area around JhalodDohad and Bagh (Gupta and Mukher ji 1938; Roy Chowdhari and Sastri 1956; Mohabey and Mathur 1989; Khosla and Sahni 1995; Mohabey 7996c; Roychowdhary et al. 1998). Only dinosaur eggs and clutches are known from the Lameta sediments and no skeletal remains are yet known. 4, Tbe Ariyalur area. A single occurrence of an egg (Mega_ loolithus) has been recorded (Kohring et al. 1996) from trre -"ri".r" Kallankurichi Formation (Maastrichtian) of the Ariyalur Group in the Tamilnadu state of southern India. The report is significant, as it constitutes the sole record of a dinosaur egg from the marine sediments in India. The egg was found in the bioturbated, bryozoa, and foraminifera-bearing marine limestone exposed in the Tancem Cement Factory (Fig. 21.1). The area has also yielded fragmentary skeletai remains of stegosaurs (Yadagiri and Ayyasaml tgSO) and
carnosaurian dinosaurs (Yadagiri and Ayyasamr I9g7) from the non-marine Kallamedu Formation (Campanian-Maastrichtian).
Nesting Sites, Nest Structure, and Nesting Behavior The dinosaur eggs, nests, and nesting sites occur exclusively in channel sandsrone facies and occasionally in emergent palustrine flat deposits. The egg-bearing sediments are often pedogenically modified and also calcretized (Mohabey 1990, 199I, 1996a. Late cretaceous Nests, Eggs, and Dung Mass of sauropods from
India .
471
1998a; Tandon et al. !995,1998; Sahni et aL.1.9941' Ghosh et al. 1,995\. Nesting sites consist of clutches having eggs belonging to a
single Megaloolithus oospecies implying a single species of sauropods laid the eggs. All of the nests are found at a single stratigraphic level. Each cluster of eggs occurs in a saucer-shaped depression measuring up to 50 cm deep and with a diameter up to 100 cm. In a majority of the nests, the eggs are found in a single layer having no well-defined pattern. In a few rare instances, clutches were found with eggs arranged in a circular pattern around a single, central egg (Fig. 21.2A). The eggs in the nests are preserved either as lower halves of eggs surrounded by eggshell debris (Fig. 21.2P., C), or as complete to near-complete (generally intact) eggs. In the partial eggs, shell fragments may occur inside the eggs or in the surrounding matrix. Such eggs may represent hatched eggs. A sizable number of compiete eggs are found in many nesting sites. A majority of eggs of M. megadermus, which represent the thickest (up to 6 mm) of all the oospecies, have been found complete. In such eggs, a network of cracks are present, possibly produced by post-burial loading and compaction. The eggs in a nest may be well separated. in conract or even superimposed tFig.21.2). The distance between adjoining nests may correspond to the size of the animals responsible for the nests, but this is speculative (Mohabey 1991, 1996a; Cousin et al. 1'994).In rare instances, eggs may be arranged in a linear row (Fig. 21 .2D) as seen with eggs of M. balasinorensis (Mohabey 1987) and M. pbensaniensis. ln a few clutches of M. khempurensis, the eggs are in an arcuate row. It is not always possible to demarcate the individual nest boundaries because the nests have been homogenized with the host sediments. The nests and nesting sites of Megaloolithas eggs provide strong evidence for community nesting and gregarious behavior of titanosaurid sauropods. The predominance of eggs and nests in the sandstone shorvs that these dinosaurs preferred to nest in the sands along the riverbank (Mohabey 1997, 7996b, I998a; Cousin et al. 1994). Based on the water vapor conductance of megaloolithid eggshells, \X/illiams et al. (1.984) and Vianey-Liaud et al. (7994) suggested that the nests needed an aerated and oxygenated microenvironment for incubation of the eggs. The coarse sand along riverbanks offered the most suitable sediments to the sauropods. Fine-grained sediments would generally have a tendency to block the pores of the eggshells and would inhibit the gaseous exchange between the developing embryo and the microenvironment of the nests. No evidence of any vegetable matter, such as leaf or wood fragments, are found that could have been possibly used for generating heat through fermentation for incubation of the eggs (Horner 1984), or even as a source of food for the young hatchlings inside the nests. The total absence of such piant matter cannot be preservation bias because wood fragments are generally well preserved in the Lameta sediments (Mohabey 1'996c).It is possible that solar energy was the main heat source for incubation. The lower halves of the hatched eggs are intact and do not show any evidence of tram-
472
.
D. M. Mohabey
pling. This evidence, togerher with the total absence of any plant remains inside the nests, suggest that the hatchlings did not stay in the nests and possibly migrated to safer places with their parents. In India, there is a total paucity of any hatchling or juvenile remains of sauropods except for a single, partial skeleton doubtfully identified as a juvenile sauropod from the Kheda area (see below). In Gujarat, clutches of elongatoolithid eggs, Ellipsoolithus l
Evidence of site-fidelity by sauropods is known from a single Iocality at Pavna in Maharashtra. There, clutches of Megaloolitbis matleyi are found at two different srratigraphic levels at the same site (Mohabey 1996a). However, a few nesting sites, like Phensani in Gujarat (Mohabey 7990, 1991, 1996a) and Kankradungra in the Jhalod area in Gujarat (Roychowdhary et al. 1998), provide evidence for successive nesting by different dinosaur taxa. Clutches of different oospecies, M. balasinorensis, M. megadermus, and M. khempurensis, occur at different stratigraphic levels. The selection of the same site over the years by the different species of sauropods might have been due to favorable local conditions (including vegetation and water) for breeding and nesting. The nesting season for the sauropods was possibly during the drier or summer season based on oxygen and carbon isotopes of the sauropod eggshells. The isotopes indicate that these egg-laying sauropods drank from water bodies having excessive evaporarion and consumed plants that utilized C4 photosynthetic pathways (Sarkar et al. 1991). The flora in the dinosaur-bearing sediments is represented by pteridophytes-like seed ferns, conifereles including Araucariacae, and angiosperm comprising smaller varieties of palms and dicots (Mohabey et al. 1993; Mohabey and Samant 2003).
Systematics and Classificarion of Indian Sauropod Eggshells The description of these eggshells have been presented elsewhere (Mohabey 1984a,1990,1991; Mohabey and Mathur 1989; Srivastava et al. 1986; Jain and Sahni 1985; Vianey-Liaud et al. 1.987; Sahni et al. 1994; Joshi 1995; Kohring et al. 1996) using the parataxonomy of Hirsch and Quinn (1,990), Hirsch (1994), Mikhailov (1991), and Mikhailov et al. (1,994). Khosla and Sahni (1995) established seven Megaloolithus oospecies for the eggshells from the Lameta Formation of the Jabalpur and Jhabua areas, and Late Cretaceous Nests, Eggs, and Dung Mass of Sauropods from
India .
473
Fig. 2 1.3. Line-draa'ing illustration of uarious Indian Late Cretaceous sauropoda and theropodd eggshells (after Mohabey 1998a,2001a). (A) Megaloolithus rahioliensis; (B) N{. phensaniensis; /C) M. khempurensis; (D/ M. dhoridungrierr>i.: rFt V. matlel i: (F/ NI. megadermus; fG) Megaloolithus balasinorensis; /H/ Megaloolithus problematica; (I)
lncerae sedis Sp h
erul itic)
(?
Dinosauroid
; 1/ Ellipsoolithus
khedaensis; /K) Trachoolithus oosp.
474
.
D. M. Mohabey
one oospecie s, Subtiliolith us kach
h cb
ensis, for fragmentary eggshells
from the Anjar inter-trappean bed. Howevet the validity of M. udlpurensis, M. padiyalensis, and M. dholiydersrs is questionable because the important diagnostic characteristics such as egg size and
shape
for
establishing the new species
is not known (Mohabey
1998a,2001a). Based on general morphology (including shape and size) and histostructure of the well-preserved eggs, Mohabey (7996a, 7998a) established eight new Megaloolithtts oospecies (Fig.
21.3A-H) and one new ootaxon Ellipsoolithus kbedaensis for Elongatoolithdae eggs (Fig. 21.3J). In addition, a Dinosauroid-Spherulitic Basic T1'pe of Hirsch and Quinn (7990) and Hirsch (1994) was recognized. More recently, a single nest with elongatoolithidae eggs having affinity to the oogenus Trachoolithus (Fig.21.3K) has been
collected from the Kheda area (Mohabev 2001a). Vianey-Liaud et ai. (2003) have attempted to establish a relationship between the Indian and European megaloolithid eggshells. Assigning eggs to dinosdttr taxa. The India dinosaur egg taxa
represent three oofamilies: Megaloolithidae, comprising one oogenus and eight oospecies; Elongatoolithidae, comprising two oogenus and two oospecies; and ?Spheroolithidae, based on incomplete eggs and eggshells (Mohabev 7996a). Based on the association of eggs and clutches lvith embryonic remains, hatchlings and associated parental bones as found in the Upper Cretaceous sediments of France, Spain, Mongolia, China, and Argentina, Megaloolithus eggs have been idenrj6ed as belonging to riranosaurs (Cousin et al. 1994; Grigorescu et al. 1994; Vianey-Liaud et ai. 1994;2003; Chiappe et al. 1998). Unfortunately, the present srate of knowledge does not permit assigning the various Megaloolitbus oospecies to individual sauropod species. Presentll', at least eight Megaloolithzs oospecies are known from India, but only rhree contemporaneo:us Titanosaurzs species and Isisaurus colberti are considered valid by Jain and Bandyopdhyay et al. (1997 but see \fil-
son and Upchurch 2003). Nfhether a single riranosaur species could be responsible for more than one oospecies of Megaloolithus cannot be ascertained at this stage.
Elongatoolithid eggshells have been assigned to theropods (Zhao 1979;Mikharlov 7991; Mikhailov et a|.1994). The Indian elongatoolithid eggshells are represented by two oogenera Ellipsoolithus and Trdchoolithus. These ootaxa have been tentatively assigned to abelisaurid theropods (Mohabey 7998a; Loyal er ai. 7999), whose skeletal remains are found in the elongatoolithid nest-bearing sediments. Recentln \Tilson et al. (2003) described a new species abelisaurid Rajasaurus ndrmadensis based on the cra-
nial and post-cranial remains found in the Lameta sediments at Rahioli of Guajrat. The prolific, semiarticulated skeletal remains of abelisaurids, which were found at Rahioli in the Kheda area in Gujarat (Dwivedi et al. 1982; Mathur and Srivastava 1987; Mohabey 1991; Chatterjee 1987; \X/ilson et al. 2003), are in the prox-
imity of nesting sites of M. rahioliensis and
Ellipsoolithus
khedaensis.
Eggshell Pathologies Reports of pathologic dinosaur eggshells in India are scarce. Mohabev (1984b) reported double-layered eggshells of Megaloolithus khempurensis (Mohabey 1998a) from a single clutch from a nesting site in the I(heda area. These eggshells have a lower normal layer 2.30 mm thick, and an upper abnormal layer 1.80 mm thick. Normally, M. khempurensis has a shell 2.36-2.50 mm thick (Fig. 21.4). Mohabey (1998a) reported anorher type of abnormal shell
showing a chaotic and interfered growth of shell units in the eggshells of Megaloolithus megaderms, the thickest (4.80 mm thick) among all the Indian dinosaur eggshells. Considering that
Late Cretaceous Nests, Eggs, and Dung Mass of Sauropods from
India .
475
4,'q ,ra
Fig. 21.4. (A) Pathologic eggshells h ou ing doub le- lay er ed sh ell
s
structur e lz Megaloolithus khempurensis eggs. Such pathologic eggshells are scdrce atnong the Indian dinosaur eggshells. (B) Normal eggshell structure as obserued in M, khempurensis. (C) Chaotic growth of shell units (both giant and dwarf-sized) and extra grouth centers obserued in tbe eggshells o/M. megadermts. The shell units
do not show normal growth and md)' repr e sent som e Path olo gi ( condition in the eggshells. Abbreuiations: Su -- shell uni4 I -interfered growth.
such pathologic eggshell occurrences are scarce, they do not appear to have any bearing on the evolution of eggshells and the extinction of Indian Cretaceous sauropods as has been suggested from the French megalooiithid eggs (Erben et aL.1979).
Purported Sauropod Hatchling Mohabey (1,987) gave a preliminary description of a purported sauropod hatchling nearly 40 cm long associated with a clutch of Megaloolithus dboridungriensis eggs (Mohabey 1998a). The specimen was in four blocks (GSllGCl2901-2904), representing a series of vertebrae, a humerus, a scapula, and an ilium. The vertebral column includes at least ten caudal vertebrae described as amphicoelous to slightly amphiplatyan and articulated by a zygosphenezygantrum arrangement. Jain (1989) opined that the specimen might represent a snake. The taxonomic identity of this important specimen (Lockley 1994; Carpenter and Alf 7994; Carpenter and Mclntosh 1994) is debated. It is delicate and fragile, but is presently being prepared for detailed description. Stable Isotope Analysis of Eggshells Stable isotopes of dinosaur eggshells are important for understand-
ing the palaeobiology of the egg-layer. The stable, carbon-and476
.
D. M. Mohabey
oxygen isotope analyses of a large number of Indian Megaloolithus eggshells from different localities was first attempted by Sarkar et al. (1991) to understand the dietary habit of the egg-layer, that is, the category of plant the titanosaurs consumed and the type and source of water they drank. Folinsbee et a|. (1,970) have shown that an approrimate linear relation exists between the A18O of water ingested by the egg-laying species and their corresponding eggshell carbonate. The Ar3C of the eggshell carbonate is similarly determined by the 13C/12C ratio of the diet consumed by the egg-laying animals. This, however, is modified by physico-chemical fractionation due to metabolism. Von Schirnding et al. (1.982) and Schaffner and Swart (1,991,) demonstrated that 13C/12C ratios in the eggshell carbonate are enriched by about 16To relative to that of the original food. Therefore, the A13C of the eggshell can be used to infer the nature of the diet of the animal and the existing vegetation. Based on the mode of photosynthesis involved, the plants can be categorized as C. and Co plants having a characteristic carbon isotope signature of A13C --26% and --13'h respectively (Smith and Epstein 1977). Sarkar et al. (199L) found that the eggshell A180 values, unlike A13C values, vary widely from -8% to +6.9"/". These values from a single clutch were fairly constant, indicating that the eggs were laid by a single individual. The spread in the A18O and A13C values is probably due to natural variability of the A18O values of the water source having high evaporation (Folinsbee et al. 1970). The A18O value of the egg-bearing host limestone is --8olo, showing that the eggs were deposited in a typical freshwater environment (Keith and 'Weber 1964). The range of A13C of for eggshells of sauropods and the associated limestone is given in Fig. 21.5. The range is quite narrow, having a mean value of -10.0% x 1.0%. Considering a metabolic enrichment of 76"/o, the A13C values of the sauropod eggshells indicate a diet of C, plant types having a A13C value of -26%. C, plants include gymnosperms (Araucariaceae, cycades) and angiosperms (including palm and dicot shrubs), which are documented from host sediments in the area (Mohabey et al. 1993) and the coprolitic mass of the sauropods (see below; also Mohabey 2001b; Mohabey and Samant 2003).
Sauropod Coprolites
In recent years there has been much speculation about the diet of sauropods. For any paleobiological interpretation, the study of their
droppings (coprolites/dung mass) is as important as the study of their skeletal remains, eggs, clutches, nesting sites, and trackways. It is possible to evaluate the interaction between the herbivorous vertebrates and contemporaneous plants by examining the undigested plant residues in the dung mass. This evidence has provided insight
into the preferred solid and liquid diet of these extinct herbivorous dinosaurs. Coprolites denote petrified fecal mass or droppings of the animals (Buckland 1829). Despite the fact that the dinosaurs domiLate Cretaceous Nests, Eggs, and Dung Mass of Sauropods
fromlndia . 477
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nated the Mesozoic system, the reports of coprolites attributed to dinosaurs are very few (Thulborn 1997; Chin 1997). The report of undigested plant remains in the coprolite rnass are even more scarce (Bradley 1946; Hantzschel et al. 1968; Chin and Gill 1996; Chin and Kirkland 7998; Thulborn 1.991). Microorganisms (Bradley 1946) and microflora (Waldman and Hopkins 1970) are reported from the coprolites from the Upper Cretaceous of Alberta, but they are assigned to some groups of reptiles other than dinosaurs. The first discovery of coprolites in India was made by S. Hislop in 1857 from the red clays of the Lameta secrion at Pisdura (Hislop 1859). Subsequently, Matley (1939) made a large collection of coprolites from this secrion and studied them systematically, subdividing them into four types based on size and shape. Of these, he referred the Type-A variety (Fig.21.6A) to titanosaurs on the basis of their large size and association with skeletons of titanosaurs (Matley 1939). However, whereas Matley described these droppings as free of any animal or plant tissues, Mohabey (see below; 1999,2000b, 2001b) reported similar Typ.-A coprolites to be enriched in a diversity of comminuted plant remains. These coprolites range from 70-100 mm in diameter, are ovoid to circular in cross section, have rounded segmented ends, and bear a smooth surface
with no ribbing. Coiling is also noticeabie in a few 478
.
D. M. Mohabey
specimens,
::.:,
Lig. 21.6. (A) Sattropod t:oltrolites rTylts-5, fi11 jtt,1 5ttr','tlls sttrl.tc,
-t
t ltt
::.',1;,:.,',.
4l:Li.,:..1
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::a,.7'.
' ril) slrttalut
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St
JtrJ
sl)t
'tt ilr\
coilin!: ond segmenttttion. Note rurnded and narrou end of ihe segnie nt and coiling irt the louer right s1tecirnetts. (B) T1'pa-A coptolite. cut tnd polished Icntgit
u
dirn I
se
ct i or
t
sh otLt
iug
prolific ltlant tissnes in the tlurtg nnss. Tlte plant tissues are t: c; rt ntin ut e tl on d yt en ni ne r al i : e d r
(silicified).
lvhile others show consrriction along the longitudinal axis. Boring, burror.vs 1-2 rnm in diameter, and scraltch marks are present on the outer surface of a fe-"v coprolite specimens, suggesting acti\.ity b), sonre insects that were possibly feeding upon the fecal mass. Insect legs and wings have also been obsen'ed in some specimens (Mohabey and Samant 2003) and such insecs m:1,v have been acciden-
taily ingested through a solid and/or liquid diet of the animals.
Other, scarabeine beetles may have been trapped while scavenging the fecal mass.
Assigning coprolites
to sauropods. Assigning dinosaur eggs
and dung mass to their producers has aiu.ar-s rentained challenging. For eggs and nests this is possible il'hen the ernbryonic renrains are I-ate Cretaceous Nests. Eggs, and Dr.rng NIass of Sauropods from
India . 479
found inside the eggs or the young hatchlings are found associated
with the nests. Similarly', the producers of the dung mass can at best be identified only when associated with the body cavity of the animals (Chin 7997). However, in the absence of such direct evidence, the coprolites and associated evidence can still provide irnportant clues to assigll the coprolites to their probable producers' In the present case, the size of the Type-A coprolites' which are up to 10 cm in diameter, limit the minimum size of the animal responsible for the defecation. A large animal can produce small droppings, but a small animal is not expected to produce large-sized droppings. Considering the potential dung-producing vertebrates in india during the Late Cretaceous, the most likely candidate are large reptiles, because the contemporary mammals where too small to produce the large-sized coprolites (Mohabe)' 1,998b; Mohabey and Udhoti 1996). Among reptiles, the dinosaurs are the most common as fossils, followed by pelomedusid turtles and crocodiles (Mohabey and Udholi 7996). Analysis of Type-A coprolites has revealecl that they consist exclusively of plant tissues (see belorv; Fig. 21.68), thereby strongly indicating an herbivorous diet of their producers. This precludes any chance of assigning them even remotely to pelomedusids or crocodiles because these reptiles are not exciusively herbivores. Among the herbivorous dinosaurs' titanosaurid sauropods emerge as the most probable producers of the coprolites of Type-A because of their large body size' Type-A .oorolites also have been found associared with skeletal remains of Tiianosaurws indicus in Pisdura (Huene and Matley 1933; Matley 1939; Mohabey et al. 1993; Mohabey 2001a). Coproiites are typically found in large numbers suggesting that
Fig.21.7. (opposite page) Varrtus tissues as obserued in cti antl polished sections ,.tf sauropod coprolites (T'Pe-A). (A) Llou'er patals and sePals. Notc utmminuted Petals antl disPersed prllen grains. (B) Apical shottt of on Lurgiosperm. (C) Apical shrtrtt of a pteridoPhyte. Note firte coniier needles. (D) Clttster ctf
plant
ouules, ds aell as Pall'nr.tnutrPhs possibll' released dfter the deb is cen c e. ( E ) C yn nosP ernt irontls sbou,ing leai and ndked seetls. (F) Transt,erse sectictn of
ttuo iern petloles, U-shaped, with t.'dsailttr bundles dt the center. Also nrte sonte seeds ctn the left side. (G) Fruit tuith a seed in the center. (H) (;)'fi1t1os7erm seeds ,rn d ot,ulifer ou s scale s.
480
.
D. NI. Mohrbcy
they were produced by a herd of the titanosaurs. The coprolites and titanosaurs occur in the overbank red clay deposits and indicate that these animals inhabited the flood plain areas (Mohabey et al. 1993; Mohabey 2001a, 2001b). Paleobotanic evidence indicates that vegetatiorl comprising of conifers, angiosperms, and pteridophytes grew in the vicinity of water bodies (Mohabey et aI. 1993; Sarkar et al. 1991). A well-developed lake sequence showing cyclical sedimentation represented by fine, laminated silici-clastics and carbonates. has been observed in the Lameta alluvial-limnic system in the area. Diatom-bearing (Centrales: Aulocosira and Pinnates), freshwater varves comprising millin-reter-sized light and dark seasonal couplets have beer.r identified in the lake sequence at least at three levels. The evidence suggests that a semi-arid, seasonal climate prevailed during the Late Cretaceous in India (Mohabey 2001b). Plant tissues and palynomorphs in coprolitic mass' WeIlpreserved comminuted plant remains comprising soft tissues of pteridophytes' g)rmnosperms' and angiosperms have been ob-
ie.ued in a large number of the Type-A coprolites (Fig' 21'68)' These plant tissues are found in association rvith fungi, algae including diatoms (Awlacosira)' and a few palvnomorphs (Mohabey and samant 2003). The comminured planr remains are present in varrous concentratlons (Figs. 2I.7,21.8). The plant tissues are sili-
Late Cretaceous Nests, Eggs, and Dung Mass of Sauropods from
India ' 481
13
Fig.21.8. Photographs of cut and polished sections of saurctpod coprolites (Type-A). Scale bar: L,000 mm. (A) A pteridophyte sp orMgium in longitwdinal sect i otr shuwitr g tncga spora ngia and microsporangia. (B) A couple of sporangia of some pteridop hytic ferns sh ouing structure of thin wall and annuli. Note a large number of spores inside and outside the sporartgiutn, Also note some cotti[er needles. rC) A sporangia shotuing dehiscence and liberated spores. Also note comminuted conifer leaues (left side of photograph). (D) Apical shoot of angiosperm, Note clusters of tender, serrated leaues. (E) Rachis and pinna-like structures, leaf debris, and palynomorphs. (F) Conifer needles and some fungal spores. (G) Fruit ulith ornamented wall and placentdl dttdchment u,ith seed and ornamental pericdrp. (H) A pear-sbaped (?) seed with distinct wall. (l) A dicot
frui with seeds.
1,
'' ...
';:rlli!!r:l
:Mffi:."':
:;,'i :;:-
cified and often stained brown, and mostly occur as irregular remains as can be expected after cropping and chewing. The diversity of plant tissues in the coprolites indicates a multiple source for the sauropod diet, consisting mainly of pteridophytes, gymnosperms, and angiosperms. Flard, woody tissues are either scarce or almost absent. The scarcity of the palynomorphs and their poor preservation can possibly be attributed to corrosion of the material in the alimentary canal of the animals ('$Taldman and Hopkin 1970). Animal dung is generally expected to be enriched in palynomorphs that normally occur in high concentrarion in open-water bodies and air. The palynomorphs include pteridophytic spores (Baretisporites and Equisetitriletes), gymnosperm pollen (Podocarpidites, Araucaricites, Balmeiopsis and Cycadopites), and angiosperm pollen (palm). In addition, the water fern Azolla is represented by massula, with microsporangia, fungal hyphae and spores, micorrhizal fungi, and
482
.
D. M. Mohabey
algae including freshwater diatoms lAulacosira) and frustules (Mohabey and Samant 2003). The evidence of the plant-bearing coprolites of Matley's TypeA are safely assignable to titanosaurs. The {loral analysis of corpro-
litic
masses strongly indicates that angiosperms, along with pteridophytes and conifers, formed a significant component of the titanosaurid diet. It also indicates that titanosaurs preferred cropping soft foliage of these plants as their solid diet. Based on the stable nitrogen isotope values A15N of 4"h w.r.t. air, the titanosaurs lacked the gut-fermentation process seen in modern, large herbivo-
rous mammals (Ghosh et al. 2003).
Conclusions Sauropod nesting sites, beiieved to be those of titanosaurids, occur in the Upper Cretaceous Lameta Formation in central and western India. A majority of eggs have been assigned to at least eight Megaloolithus oospecies. The distribution of the eggs suggests community nesting along the riverbank, with the eggs buried in the river sand. Large coprolites, 100 mm in diameter, also occur and are thought to belong to titanosaurs. Angiosperms form a significant component of the floral content of the coprolitic mass and indicate a strong and
well-established relationship between titanosaurs and angiosperms. The titanosaurs witnessed an acme of their breeding and nesting in the Late Cretaceous of India (Mohabey 1998a). However, these dinosaurs struggled to survive the initial onslaught caused by the Deccan volcanic activity that was initiated at least 1.3 million years before the Cretaceous-Tertiary Boundary (Venkteshan et al. 1993). The available radiometric and palaeomagnetic data from the Deccan lava pile suggest that the volcanism was episodic in nature and continued over an extended duration from 69 Ma to 63 Ma, between magnetochrons 31R and 28N (Sheth et al. 2001). The Iast dinosaurs in India apparently disappeared 300 ky before the Cretaceous-Tertiary boundary (Hansen et al. 2001), and Deccan volcanism is strongly favored as the most probable culprit responsible for the extinction of the dinosaurs. Acl<nowledgments. The author expresses his sincere thanks to the Director General, Geological Survey of India, for permitting
I owe my sincere thanks for fruitful discussion with Seva Dass, Deputy Director General, Central Region and Arun Sonakia, Director, Palaeontology Division, Nagpur. I am publishing of this paper.
indebted to Bandana Samant, Nagpur University Department of Geology, for her great help for palynological study of the coprolites and preparation of the manuscript. Review and comments offered by all the reviewers has immensely helped in improving the manuscript. I owe my thanks to Kenneth Carpenter, who went through the initial manuscript and made critical comments and suggestions. Shri Y. K. Somkunwar helped with the photography and Shaikh Naveed prepared the line drawings.
Late Cretaceous Nests, Eggs, and Dung Mass of Sauropods from
India .
483
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Late Cretaceous Nests, Eggs, and Dung Mass of Sauropods from
India . 489
INDEX
abelisaurids, 466, 467, 17 O, 47 3, 47 5 Aegyptosaurus, 84, 108 Aeolosdttrus, 84, 1 01, 705, 262, 325, 329, 330, 410,444,417
affinis, 41,43, 44,77
africana, 349, 35 i africanus, 38, 41, 63, 67, 71-73, 357 agrioensis,4-30, 436
7
5,
Agustinia, 439 ajax, 66, 25 5
)19-))) )): ))7 ))q )rl )r{
Alamosdurus, 84, 107, 108, 194, 262, 325, 329-335, 360 Alligator, 270, 349, 351, 369 allosaurids, 467 Allo saurtrs, 43, 142, 3.+9, 353 altithorax, 1.94, 23 5, 257, 253, 254, 257, 270, 339 a\ttrs, 67, 7 4, 7 9-82, 85, 103, 104, 261
Atnargasaurus, 38-5,,+30,
43
5, 436,
443,441 Ammosaurus,3, 6, 18, 21, 30 Ampelosaurtts, 115, 1 17, 118, 120722, 124-73 r, 1 33-1 36, 2s0, 251, 2.53, 262,443,4ao Amp h ico eli as, 67, 7 4, 267, 29 1 Amygdalodon, 130, 432, 433, 444 Anchisauria, 21, 22, 29, 30 .l Artchisaurus, 6, 15, 8, 21, 30, 31, 223-22.5 Anoesaurrdae, 1.) )! z)v Andesaurus, 81, 96, 107, 105, 1 06, 107, 248-250, 253, 25 5, 259, 260,262,321, 325, 330, 332334, 336, 430, 438, 443,444 angiosperms, 467 , 468, 477 , 480, 482, ,+83
Ankylosauria, 336
ankl'losaurian, 422 Antdrctostturus, 84, 101, 108, 1 19, 120, 325, 330, 331, 333, 335, 336, 339, 355, 440, 447, 448, 467, 169 Antetonitrus, 2, 4, 6, 1 6, 18, 21, 22, 24, 26, 349, 3s6, 357, 372, 37 3 Apatosatrrus,33, 39, 44, 48, 54, 57, 59, 61,-63,6s, 68,69,7 1,73,98, 141, 742, 141-116, 148, 151, 155, t 70, 181, 188, 192, r93, 212, 217, 237, 244, 24 5, 2 50-2s7, 261, 263, 268. 2-0-2-3. 2-s-284, 280-2e8, 303, 304, 306, 307, 322, 323, 325, 329, 330,332, 333, 336, 34r, 347, 349,353, 3s5, 357, 363-369,
385-388,390 Araucariacae, 473 Araucari cites, 47 3, 482 araukanicus, 440, 447 archosaurs, 362 Argentinosaurus, 84, 94, 249-2 5 1, 253, 255, 259-263, 340, 430,
440,444 Argyrosaurus, 84, I 08, 262, 32I, 325, 326, 332-334, 337, 339, 410, 444 (tstibidi, 125, 446 Astrodon, 78-85, 92, 9 5, 96, 101,
103-109, atdcis,
71
1
88, 194
5, 117, 120, 124, 734-136,
446
Atlantosauridae, 41 Atlasaurtts, 250, 325-327,330, 34 1
Aulacctsira,480, 483 australis, 250, 325, 440, 441 Austrosaurus, 333, 336,
15
6, 4 57,
462-464 Aualonia,35
Azolld,4B2 AO
I
Balmeiopsis,482 Barapasaurus, 6, 1 8, 21, 22, 30, 223, 224, 219, 252, .155, 3s6,,+33
303, 322, 325-327, 333, 336, 338, 339, 35s, 3s6, 363, 365, 385, 386, 389, 390,
Baretisporites, 482
415,438
balasinorensis, 472,
47 3
Bdrosaurus,38-75, 145-148, 1 51, 213, 233, 235, 237, 214,245, 250, 251, 253-25 6, 261, 27 0, 27 8, 28 5, 29 1, 291. 296-298, 303, 306, 349, 3.57, 368,369,381, 383, 385, 386,388
capensis,
30s,306,317
birdi, 360,414,415 blandfordi, 466, 46 r-, 169 Blikanasaurtrs, 2, 6, 23, )-5, 26, 28, 3 |
Ceratopsia,336
borealis,4,8,13
Cetiosauridae,
boscarollii, 253, 256, 402, 403, 409-
Cetiosaurisctrs, 69, 73, 369
4r1,
460,461 Brachiosauridae, 225, 439, 464 brachiosaurs, 1 0 5, 226, 284 Brachiosaurus,38, 39,48, 57, 61, 65, 72, 81, 81, 85, 90, 92, 98-102, 104-106,109, 145, 116, 175, 18 1, 193, 194, 212, 213, 2t7, 21. 8, 220, 22r, 223-229, 233, 23 5, 237, 244, 215, 248-257, 253, 2s4, 257, 258, 263, 27 0, 27 B, 280, 285, 286, 32s, 327, 329-333, 336, 339, 341, 347, 349, 35s, 385, 386, 402,403, 405, 407 , 41r, 112, 4rs, 419,
439,443,448,460, 16r 67 brancai, 217 , 21,8, 220, 235,248-251., 253, 254, 257, 258, 270, 303, 329, 332, 336, 339, 349, 402,
B ra
c h
yp o d
r-t s
atr r u s, 4
403,411,412 Breuiparctpus, 329 Brontopodidae, 329 Brontopodus, 329, 358-360, 11 3-11 5, 117 B rontoth eritmt, 323, 324
broutni,2,
5
camarasaurid, 227, 272, 30.1, 307, 310,
313,314,413 Camarasaurida e, 143, 148, 249
Camarasauromorpha, 338, 434, 438 Camarasaurus,3S, 39, 48, 57-59, 6163, 6s, 67, 71, 84, 85, 90, 92, 96, 99, 100, 101, 105, 141-116,148, 151, 1 54-177, 180-185, 188, 192, L93, 199-201, 203-210, 2t2, 213, 218, 2r9 , 223-229, 233, 23 5-239, 243, 244, 250, 253, 2s4, 257, 258, 261, 263, 268, 27 0, 27 t, 27 3, 27 s-29 8,
lndex
6,21
carnegii, 43, 45, 51, 66, 67, 71, 217, 250,251, 253-255, 302, 303, cazaui, 430, 13 5, 436, 443 Cedarosaurus, 79, 84, 9 5, 96, 99, 100108, 189,437
brachiosaurid, 79, 92, 303, 372, 314, 332, 350, 403, 412, 419, 4 54,
.
402,405,
Cdrnelotia, 4, 6, 2I, 22, 28, 29 Campanellula, 401,402
Bellusaurus,105, 188 benitezi, 434
492
329, 332, 347, 353, 366, 369,
4
32, 133,
45
6
cetiosaurs, 226, 228, 29 6 Cetiosaurus, 21,2, 217 , 218,220, 226, 323, 32s, 369, 385,433 chalicotheres, 336 charophvtes, 469 Ch
on dr
o
st e o s auru
s, 40 3
Chrl'soc1-on, 339
chttbutensis,430, 433 Cbubutisaurus, 84, 99, 105-108, 250, 325, 329-336, 430, 437-139,
443,441 coelurosaurs, 467,471 colberti, 84, 1 07, 253, 467 , 469 Coloradosaurus, 3 (olunfua, 349, 351
Coryphodon,323 croccrdiles, 469, 480
cromptoni,2 a.tllinguortbi, 2 C1-cadopites, 482 delgodoi, 248-250, 253, 260, 325, 332, 334, 336, 430,138,443 dholiyaensis, 471 dhoridungriensis, 47 0, 17 6 Dicraeosauridae, 228. 4 17, 112, 43 5, 436 dicraeosaurids, 136, 442, 443, 445, 467 Dicrdeosaurus, 18, 51, 63, 69,73,212, 217, 227, 229, 252, 25 6, 26 1, 319, 435 dicrocei, 79, 187, 1 88, 413
Dinoceras,323 Diplodocidae, 41, 43, 63,55, 7.S, 1,+8, 225, 249,302, 303, 40s, 136 diplodocids, 58, 61, 67, 69, 7 1, 73, 145, 180, 2r2, 221, 2,27, 228, 25 6, 272, 278, 280, 288, 291, 292, 296, 298, 306-308, 349, 369, 37A,
37
s,
411 ,
416
Diplodocoidea, 225, 248, 2 5 4-257, 262, 322, 32.7, 349, 39 5, 407, 135-437 , 445, 448
diplodocoids, 250, 252, 263, 325, 329, 330, 332, 347, 402, 470, 412, 419, 430, 436, 437, 443, 167 Diplodocus,3S-48, .50, 5i, 54, 57-59, 6 l-63, 6 5-69, 7 1_7 4, 9 6, 142, 146_1 5 1, 175, 18 1, 212, 217, 220, 233, 250, 274,
222, 224_226, 228, 229,
237-239, 242, 214, 251,
24 5 ,
3_257, 268, 27 0_ 277 , 279_281., 283, 281, 286-289, 291_298, 302_307, 312, 316, 317, 347,349, 353, 355, 357, 363, 365, 366,368, 369, 385, 386,405,435 25
dixeyi,253,255,262 Drauidosattus, 167 Efraasia,
3
E\ephas,323,3.50,389 Ellip soolithus, 468, 47 3-47 s Elongatoolithidae, 468, 17 3-47 5
Epachthosaurus, 84, 91, 10 S, 249, 250, 2s s, 2s9, 26 1_263, 325, 329_ 331, 333-336, 416, 440, 441 Equisetitriletes, 482 Eucanterotus,84, 95, 2.53, 257, 258, 260 Euhelopodidae , 223, 225, 227 euhelopcrdids, 224, 226, 228 Eu h elopus, 18, 212, 217, 218, 223,
229,3ss,369,40s Eusauropoda, 338, 361, 365, 370, 371, 375
eusauropods, 249, 25 5, 327, 346, 349, 355-358, 360, 361,368, 370, 372-37 5, 430, 432_434 LusRetosdurus, /-, J, 5- /
ruilranosaurla,
f-J
t,
hadrosaurian, 396, 421, 122 hadrosaurid, 340, ,+1 8, 421
Hadrosauridae,336 Hdnsennnni,435 Haplocantbctsaurus, 38, 39, 18, 57, 181, 233, 236, 237, 214, 251_ 253, 256, 257, 270, 278, 285, 286, 288, 290, 292,303, 385 hayi, 67, 63, 66, 302-304, 312, 317, 369 H errerasattus, 3.+9, 350, 352-35i Histriasaurus, 252-251, 256, 402, 403,
105,409-471,479 homalodontheres, 336 h uinculens is, 249, 2 5 3, 260, 430 Hypselosaurus, 1 5, 134 .1
imelakei,326 incerttts, 1, 8 indicus, 116, 131, 466, 167 , 469, 490 ingenipes, 2
ittsignis, 250, 430, 437, 138 Isanosaurus, 6, 21,22 Isisdurus, 84, 1A7, 189, 251, 253, 467, 469, 47 5
Iuticctsaurus,443 .lainosaurus, 85,90 .lanenschia, 72, 323, 329, 330, 332335, 439 Jobaria,338, 433, 434 johnsoni, 78-B 5, 92 kachhchensis, 174 khedaensis, 473-47 5
khempurensis, 47247 5 Kotasaurus, 6, 18, 21,, 22, 30, 223, 224 Rr4ilSCI, ++
L6 z
eutrtanosaurs, 259, 262 excelsus, 250, 251, 253, 254, 2SA, 261, 32s, 329, 333, 364, 367. 369
fariasi,249,250, 255, 256, 4.10, 433 foxi, 257, 258, 260 garasbae, 252.,256, 410,411, 420 gastropods, ,{69 Cigantosaurus, 38, 41, 63, 67, 72, 7 3, 413
gigas,403
Giraffa,339 Gondwanatitan, 84, 101 gracilis, 17 grandis, 71, 143, 144, 155, 1 61, 166170, 173, 177, 180, 1 8i, 253,
257,261,294 grauis, 167 gymnosperms, 467 , 469, 477, 480, 182 Gyposaurus, 6,27
lacustris, 303 Laplatasaurus, 84, 107 , 108, 325, 327, 330-.332, 339, 440, 447, 467, 469 L.lppdlentosltlus, 249, 339, 433, 450 lentus, 38, 40, 13, 47-49, 52, 56, 58, 60, 64-66, 69-71,74,1s4_l 58, 161, 166, 168, 169, 173, 17 5_ r77, 180,181, 184, 185, 199_ 201, 203, 218, 238, 2s0, 253,
261,303, 313,319 lepidosaurs, 362 Lessemsaurus, 4, 6,249
lewisi, 15 5, 163, 1 6 5, 1 69, 170, 790, 181,183-18.5,339 ligabtrei, 439
Lirainosattus, 34, 107, 120, 125, 135, 136,446 Iiuid, 319,357
Iongus,302,303,317 loricatus, 251, 253, 260, 441, 447 louisa e, 59, 220, 22I, 250-2.53, 255, 256,261,297, 330, 332
lndex
.
493
Loxodontd, 339, 349, 35 1 Ltfengosaurtrs, 3, 7 , 21 Macronaria,
Ornithopsis, 25T ostracocles, 469
218,250,257,2,62,327,
338,349
padil,alensis, 171
Parabrontopodidae,329
nracronarians,2,19,256,263,325, Pdralititan,84,107
339 167,469 Magl,arosaurus, 84, 120, 134, 416, 421,442,143 Malawisaurus,84, 105-108, 25i, 2.53, 255,262,413 326,329,332, 336,
madagascariensls, 339, 433,
Mamenchisaurus, 354, 355,
45,224,225,249,
405 Marasuchus,248,249
ptttagonicus, l30 Patagosaurus, 188, 223, 221,219,250, 252, 2.5 5, 256, 259, 322, 430,
133,411 Pellegrinisaurus, 140,447 pelomedusid,,{80 Pelorosaurtts, 106,I07
phensaniensis,470,172 Phua'iangosaurzs,84,105,107,108,
Mdssosportdylus,7,28,30,32,323,
188, 193,248-251,253,259, 260,262,333,336,460 Platcosdurauus, 2, 5,7 , 1 5, i 8-20, 23, 26,28
385 matle.ti, 173 maximus,3i} mckillotrti, 456,457 megadermtts,4r-2, 173,475 Megaloolithida e, 466, 468, 47 5
Plateosauria, 30
Plateosauridae,3,,{ .l
Plateosaurus, 2, 7 , 15, 1 6, 1 8, 9, 23,
483 25-28, 206, 224, 225, 319, 3 52Melanorosauridae,2-1,29,30 354,385 Melanorosaurus, 7,2, 4-7, 15-29, 31, Pleurocoelidae, 108 Pleurocoelus, TS-85, 92, 94, 103, 104, 32,223 MendoTasaurus,260 188, 189, 439 mississrppiensis,270,369 Podocarpidites, 482 powelli, 440,447 Morosaurus, 385 prisctts, 115, 13,+, 253 muniozi, 140,411 prosauropod,1,2,4,6,7,11,18,19, Mussaurus,3 Mymoorapehd, ll2 21,21-26,28, 31, 32, 322,323, Megaloolithus, 466, 468, 470-477 ,
355, 356, 358, 362 Prosauropoda, ,+, 3 I, 223, 350
475 nanus,78-82,84,85,104 nannadensis,475 neguyelap,260 nana,
proteles,T9 pteridophytes, 467,469,473, ,+80,
482,483
Nemegtosauridae, 22.5
nemegtosaurids,2l2,
458
Nemegtosaurus, 448 neosauropod, 205, 321, 322,
Quaesitosaurus, 148
327,329,
356, 360,368, 372-375,434,435 Neosauropoda, 338, 349, 353, 365, 370,371 Neuquensaurus, 8,+, 95, 102, 108, 250, 331-334, 347,349,354,
rahioliensis, 470, 475 Rajasaurus, 475 Rapetosaurus,34, 101, 107,108,221,
336,447 rauisuchids, 2.19 Rarosrtsaurus,411, 430, 436,414
325,329,355,140-412,444 readi,1,2,4, 5,22,23,32
447 B6
Nigersaurus, 420, Nurosaurus, 383-3
338
Omeisauridae, Omeisaurus, 205, 224, 225, 219, 327 349, 353-3s6,
370,434 Opistbocoelicaudia,211,2.51, 253,
rebbachisaurid , 249, 253, 256, 262, 263, 410, 411, 419, 420, 436, 443, 445, 417
,
255,260,262,263,327,329,
Rebbachisauridae,411,436 Rebbachisaurus, 252-254, 256, 32
.
Index
,
444
Riojasaurus,2-1,7,15, 16, 18-23,25-
330,332-335,339,349,3s3, 28 rionegrinus,262,325,410 355,356,360,402,139 robusta,72,303,139 Opisthocoelicaudinae, 338 ornithodirans, 352, 353 robustus, 61,72,113 Rctcasaurus,440-442 ornithopod,,{66 494
r-
329,110,4t1,420,430, 436,
saltasaurids, 2.59, 45 8 Saltasaurinae, 262, 310, 435, 441, 447 saltasarrrines, 25 5 , 263, 327 , 334, 339 ,
430,441,412
Saltdsdurtts, 8,+, 95, 105, 108, 185,
189, 2s1, 253, 260, 263, 432, 13 s , 441 , 444, 447 sartjuanensis,262
3
s6,
sattleri,435 Sdturnalid,2S Sauropodichnus, 329 sauropodomorpha, 1, 4, 29,222,338 sauropoides, .1, 249 Sauroposeiden, 7, 79, 84, 104, 109, ,+05
sciuttoi, 249 , 25 5 , 259 , 261, 440 isntosauru s, 288, 29 6 Sellosaurus, 3 s eptetttr ionalis, 467, 469 Sbunctsaurus, 7, 18, 21, 22, 30, Se
201-
203, 20 s-207, 221-226, 249, 355, 370 sinocanadorum, 224 sirindhornae, 248, 249, 251 Somphospondvli, 405 Sonorosaurus, 79, 257 , 437 Spheroolithidae, 475 Stegosauridae, 336
Stegosdurus, 142, 17 l Struthiosdurus, 422 Subtiliolithus, 474 superbtts, 32.5, 332, 334, 337, 440 Supersaurus, 73, 74, 98, 181, 794, 251,
264, 321, 321-32,7, 329_341, 5, 420, 137, 466_469, 17 s, 477,478,.+80, ,+8-l Titanosauria, 185, 263, 321, 327, 331, 334-336, 338, 403, 405, 435, 438, 439, 4 51, 4 57, 458, 467-463 titanosaurian, 41 5, 416, 420, 430, 436, 41
438-44 1, 443, 44 5448, 460162 titar.rosaurid, 9-5, 99, 101, 109, 115117, r20, 121, 131, 135, 185, 23 5-237, 244, 3 5 6, 360, 405, 430, 440, 44 r, 445-448, 4 s7, 464, 466, 470, 472, 480, .+83 Titanosauridae, 118, 120, 134, 135, 223, 22s, 255, 338, 43 5, 137,
439,443 titanosauriform,
9 5, 9 6, 98, 101, 104, 105, 107, 108, 187, 194, 248, 250, 2s7, 303, 321, 322, 326, 327, 329,330, 332-337, 339, 341, 403, 405, 407, 109, 413, 420, 430, 434, 437-439, 443, 415, 446, 4 51, 456, 4 s9, 460, 463 Titanosauriforrnes, 338, 39 5, 405, 412, 119, 435, 437 , 438, 462 Titanosaurimanus, 41 5, 4L6 Titanosauroidea, 225 Titanosaurtts, l lS, 1 16, 134, 456, 467,
169,47s,480 Tornieria, 72, 303 Trachoolithus, 47 4, Triceratops, 40
47 5
296,297 suf)retnus, 154-155, 161, 163, 167t70, 17 5, 177, 184,250,2s4,
26t, 325,333,
ualdensis,4l3 Venenosaurus, 79, 81, 9 6, 98, 100,
101, 106-108, 187-19.5, 2.50,
339
325,329-3i2,413 tagorei, 249
Yolkh eimeria, 430, 43 3, 444
tatnesnensis, 420 Tehttel ch esaurus, 43,{, 435, 437, 441
Vulcanodon, T, 1.8,21, 22,25,223, 327, 349, 353-358, 367, 362,
Telmatosaurus, 122
Tendagurid,25T tessctnei, 252-254,256, 430, 136 thabdnensis, 22, 23
ThecodontosaLrrus,2S tlreropod, 112, 1. 52, 322, 356, 358, 362, 402, 407 , 419, 120, 466, 467, 173, 47 5 thompsorti, T9 tianftrensis, 249, 434 titanosaur, 98, 99, 105, 107, 180, 22.1, 228, 248-2 5 1, 2.53, 2.55, 257-
372-374,430 vulcanodontids , 226, 228 walpurensis,4T4
ueiskopfae, T9 wichtnannianus, 119, 120, 325, 440, 447 hndhpin, 27 0, 27 8, 296 Yunnanosaurus, 222
ya
zdansk.ti,217
Index
.
495
As a research associate at the Denver Museum of Nature and
Sci-
VIRGINIA TID\(/ELL is primarily focused on gaining an understanding of the phylogenetic relationship of the Early Cretaceous sauropods of North America. ence,
KENNETH CARPENTER is the dinosaur paieontologist for the Denver Museum of Natural History and author of Eggs, Nes/s, and Baby Dinosaurs, editor of The Armored Dinosaurs, and coeditor of Mesozoic Vertebrate Life, aII published by Indiana University Press. He is also co-editor of Dinosaur S),stematics, Dinosaur Eggs and Babies, and The Upper Jurassic Morrison Formation.
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