Tyrannosaurus rex. The Tyrant King

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TYRANIVOSAURUS REX, THE TYRANT KING

Life of the Past

James O. Farlow editor

TYRANNOSAURUS REX, THE TYRANT KING

Edited by Peter Larson and Kenneth Carpenter

Indiana Unit ersity Press B Io

omin gton

6 lndi an ap oli s

This book is a publication of lndiana University Press 601 North Morton Streel Bloomington, lN 47404-3797 USA

http: / / i u press. i nd ia n a.ed u Telep h o n e orders : 800 - 842- 679 6 Fax orders:

81

2-855-793

1

Orders by e-mail: [email protected] @

2008 by lndiana University

Press

All rights reserved No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and recording, or by any information storage and retrieval system, without permission in writing from the publisher. The Association of American tJniversity Presses' Resolution on Permissions constitutes the only exception to this prohibition The paper used in this publication meets the minimum requirements of American National Standard for lnformation Sciences-Permanence of Paper for Printed Library Mateild1 ANSI 239.48-1984.

Manufactured in the United States of Ameilca Library of Congress Cataloging-in-Publication Data Tyrannosaurus rex, the tyrant king / edited by Peter Larson and Kenneth Carpenter. (Life of the past) p cm.

-

lncludes index. ISBN-13: 978-0-253-35087-9 (cloth: alk. pape) 1. Tyrannosaurus rex-Research. L Larson, Peter L. Il. Carpenter, Kenneth, date QE862.S3T977 2008

567.912'9-dc22 2007045376

12345131211100908

CO NTE NTS

ix

SUPPLEMENTAL CD-ROM CONTENTS

xi

CONTRIBUTORS

xiii

PREFAC

E

xv

INSTITUTIONAL ABBREVIATIONS

'f

On" Hundred Years of Tyrannosaurus rex:The Skeletons

1

NEAI L. LARSON

A Z

Wyoming's Dynamosaurus imperiosus and Other Early Discoveries of Tyrannosaurus rex in the Rocky Mountain West

57

BRENT H. BREITHAUPT, ELIZABETH H, SOUTHWELL, AND NEFFRA

3

How Old ls T. rex? Challenges with the Dating of Terrestrial Strata Deposited during the Maastrichtian Stage of the Cretaceous Period

63

KIRK JOHNSON

+

A

Preliminary Account of the Tyrannosaurid Pete from the Lance Formation of Wyoming

67

KRAIG DERSTLER AND JOHN M. IVYERS

r)

Taphonomy of the Tyrannosaurus rex Peck's Rex from the Hell Creek Formation of Montana

75

KRAIG DERSTLER AND JOHN N/. N/YERS

A.

IVATTHEWS

O

Taphonomy and Environment of Deposition of a Juvenile Tvrannosaurid Skeleton from the Hell Creek Formation (Latest Maastrichtian) of Southeastern Montana

33

'.1

lF

1

a-ai- D IENDERSON

/

One Pretty AmazingT. rex

93

fvlARY NIGBY SCHWEITZER, JENNIFER L, WITTMEYER, AND JOHN R. HORNER

6

Variation and Sexual Dimorphism in Tyrannosaurus rex

103

_ Y A

131

10 167 4.1

PETER LARSON

Why Tyrannosaurus rex Had Puny Arms:An Integral Morphodynamic Solution to a Simple Puzzle in Theropod Paleobiology MARTIN LOCKLEY, REIJI KUKIHARA, AND LAURA MITCHELL

Looking Again at the Forelimb of Tyrannosaurus rex CHRISTINE LIPKIN AND KENNETH CARPENTER

||

Rex, Sit:

193

KENT

.l 't I

Z

205 |

5

233 ltA

l+ 245

.lr I

AND WlLLlAl\4 H. HARRlSON

)

255 vi

il

Digital Modeling of Tyrannosaurus rexat Rest

A. STEVENS,

PETER LARSON, ERIC D. WILL5,

AND ART ANDERSON

rex Speed Trap

PHILLIP L. MANNING

Atlas of the Skull Bones of Tvrannosaurus rex PETER LARSON

Palatal Kinesis of Tvrannosaurus rex HANS C, E, LARSSON

Reconstruction of the Jaw Musculature of Tyrannosaurus rex RALPH E, I\4OLNAR

Contents

lO

Vestigialism in a Dinosaur

283

WILLIAM L, ABLER

4a II

287

18 307

_ 19 355

_ 20 371 14

ZI

Tyrannosaurid Pathologies as Clues to Nature and Nurture in the Cretaceous BRUCE IV, ROTHSCHILD AND RALPH E. MOLNAR

The Extreme Lifestyles and Habits of the Gigantic Tyrannosaurid Superpredators of the Late Cretaceous of North America and Asia GREGORY S. PAUL

An Analysis of Predator-Prey Behavior in a Head-to-Head Encountlr between Tyrannosaurus rex and Triceratops JOHN HAPP

A Critical Reappraisal of the Obligate Scavenging Hypothesis for Tyrannosaurus rex and other Tyrant Dinosaurs THOIMAS R, HOLTZ

Tyrannosaurus rex: A Century of Celebrity

399

DONALD F. GLUT

429

IN DEX

vii

JR.

Contents

CONTRIBUTORS

William L. Abler, 1200 Warren Creek

Rd.,

Arcata, CA 95521, USA.

Art Anderson, Virtual Rd., Suite 16,

Surfaces lnc., 832 E Rand Mt. Prospect, lL 60056, USA.

Brent H. Breithaupt, Geological Museum, University

of Wyoming, Laramie, WY 82071,

USA.

Kenneth Carpenter, Department of Earth Sciencet Denver Museum

of

Nature and Science, 2001 Colorado Blvd., Denver, CO 80206, USA.

Kraig Derstler, Department of Earth and Environmental

Sciences,

University of New Orleans, New Orleans, LA 70148, USA.

Donald F. Glut,2805 N Keystone

lohn Happ, 3889 Chestnut

St., Burbank, CA 91504-1604, USA

Hill Rd., Harpers Ferry, WV 25425, USA.

William H. Harrison, Department of Geology and Environmental Geosciencet Northern lllinois University, Dekalb, lL 60115, USA Michael D. Henderson, Burpee Museum of Natural History, 737 N Main St., Rockford, lL 61103, USA.

Thomas R. Holtz Jr., Department of Geology, university of Maryland, College Park, MD 20742, USA. John R. Horner, Museum of the Rockies, Montana State University, Bozeman, MT 59717, USA

Kirk lohnson, Denver Museum of Nature and Science, 2001 Colorado Blvd., Denver, CO 80206, USA. Reiji Kukihara, Dinosaur Tracks Museum, University of Colorado at Denver, P.O. Box 173364, Denver, CO 80217, USA. Neal L. Larson, Black Hills lnstitute of Geological Research lnc., P.O. Box 643, Hill City, SD 57745, USA.

Peter Larson, Black Hills lnstitute of Geological Research lnc., P.O. Box 643, Hill City, SD 57745, USA. Hans C. E. Larsson, Redpath Museum, McGill University, 859 Sherbrooke St. W, Montreal, Quebec H3A 2K6, Canada. Christine Lipkin, University of Chicago, Chicago, lL 60637, USA.

Martin Lockley, Dinosaur

Tracks Museum,

Univertty of Colorado

at Denver, P.O. Box 173364, Denver, CO 80217, USA

Phillip L, Manning, Tne Manchester t,4useum, lJniversity of

r,1arc.:s::'. Ot'crs ?cad,

l',4anchester, M13 9PL UK.

Neffra A. Matthews, Geological Museum, lJniversity of Wyoming, Laramre, WY 82071, USA. Laura Mitchell, Dinosaur Tracks Museum, University of Colorado at Denver, P.O. Box 173364, Denver, CO 80217, USA. Ralph E. Molnar, Museum of Northern Arizona, 3101 N Fort Valley Rd., Flagstaff, AZ 86001, USA.

lohn M. Myers, Department of Geology,

108 Thompson Hall, Kansas State University, Manhattan, KS 66506, USA

Gregory S. Paul,3109 N Calvert

St., Side,

Baltimore MD 21218, USA

Bruce M. Rothschild, Arthritis Center of Northeast Ohio, 5500 Market, Youngstown, OH 44512, USA

Elizabeth H. Southwell, Geological Museum, University of Wyoming, Laramie, WY, 82071, USA.

Mary Higby Schweitzer, Department of Mailne, Earth and Atmospheric Sciencet North Carolina Stafe University, Raleigh NC 27695, USA. Kent

A. Stevens, Department of Computer and Information

Science, University of Oregon, Eugene, OR 97403, USA

Eric D. Wills, Department of Computer and lnformation \rionra I tnivar
lennifer L. Wittmeyer, North

Carolina Museum of Natural Science. Raleigh, NC 27695, USA.

xii

Contrtbutors

PREFACE

The archetvpal dinosaur, TyrannosaurlLs rex, celebratecl its l00th anniversarl' in 2005. This occasion was observed bv a conference, i00 Years of Ttrannosaurus rex: A S1'mposium, hosted at the Black Hills Institute of Geoiogical Research in Hill City, SD, June I0-11,2005. The symposiun brought together an international cast of dir-rosaur paleontologists who presented the results of their research to the general public. The paleontologists all agree, hou'ever, that the n'rost enjoyable and intellectuallv stirnr-rlating time was spent ir-r the basement storage room of the Black Hills Institr,rte, snrrounded by bones and casts of Tyrannosaurus. There, indiviclual bones could be examined during the many long hours of discr,rssion and debate abortTvrannosaurus. These debates undoubtedly had an influence on the chapters comprising the resulting volume. The editors, Peter Larson and Kennetl-r Carpenter, thank the authors for their cor-rtributions. To fill out this volume, a ferv additional cl-rapters were solicited, and lve thank these authors as w'ell.

We also tl-rar-rk the n'ranv indil'iduals of the Black Hills Institute of Geological Research, the N,1[an-rn-roth Site of Hot Springs, the Hill City Public Schools, the fourney Museum, the Kirby Science Center, and numerous businesses and the local residents for their assistance in makirre the svmposium possible

'fhanks to Robert Sloan, editor at Indiana Universitv

Press

for his

support of tl-ris volume, and to James O. Farlorv, editor of the Life of the Past series for the press. N{arion Zenker (BHI) and Deborah Longhofer {DMNS) provided clerical sr-rpport.

I

NSTITUTIONAL ABB REVIATIONS

AMNH BHI BMNH BMR CM

American Museum of Natural History, New York, NY Black Hills Institute of Geological Research, Hill City, SD Natural History Museum, London, England Burpee Museum

of

Carnegie Museum

CMNH

Cleveland Museum

DMNH

Denver Museum

FMNH

Field Museum

IVPP LACM LDP LL

of

Natural History, Rockford, lL

of

Natural History, Pittsburg, PA

of

of

Natural History, Cleveland, OH

Nature & Science, Denver, CO

Natural History, Chicago lL

Institute of Vertebrate Paleontology and Palaeoanthropology, Beiiing, China Natural History Museum

of

Los

Angeles County,

Los

Angeles, CA

Lance Dinosaur Project, New Orleans, LA The Manchester Museum, Manchester, England

MMS

The Science Museum of Minnesota, St. PauL MN

MOR

Museum of the Rockies, Montana State University, Bozeman, MT

NCSM NMMNH

PIN

North Carolina Sfate Museum of Natural Sciencet Raleigh, NC New Mexico Museum of Natural History, Albuquerque, NM Paleontological lnstitute, Russian Academy of Sciences, Moscow, Russra

RMM

Red

ROM

Royal Ontario Museum, Toronto, Ontario, Canada

RSM

Royal Saskatchewan

Mountian Museum, Birmingham, AL

Museum, Regina, Saskatchewan, Canada

RTMP

Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada

SDSM

Museum of Geology, South Dakota School of Mines and Technology, Rapid City, SD

SUP TCM UCMP

Shenandoah University, Winchester, VA The Children's Museum, Indianapolis, IN University of Cailfornb, Museum of Paleontology, Berkeley, CA

tiCRC

.' :- :-_:: ;csea.cn Collection, Chicago, IL UN,lNH Uta^ './-t:-- :-'..:..a Htstory, l.)niversity of utah, Salt Lake City, UT -S','.' ',i:.-. '.luseum of Natural History, Smithsonian 's :-itan, Washington, DC -- , P UWGM

Universtt,i

University of Utah Vertebrate paleontology, Salt Lake City, UT University of Wisconsin Geology Museum, Madison, Wl

YPM

Yale Peabody Museum

ZPAL

lnstitute of Palaeabiology of the Polish Acadamy of Sciences, warsaw, poland

xvi

lnstitutional Abbreviations

of

Natural History, New Haven, CT

TYRANNOSAURUS REX, THE TYRANT KING

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ONE HUNDRED YEARS OF TYRANNOSAURUS REX: THE SKELETONS Neal L. Larson

In

1905, Henry Fairfield Osborn, of tl-re American Museum of Naturai Historl', published the narne Tyrannosaurus rex for a large theropod discovered bv Barnum Broi,vn rvithin the Upper Maastrichtian Hell Creek

lntroduction

Formation of N{or-rtana. Later,Dynamosdurus imperiosus Osborn 1905 and 2 cervical vertebrae described as Manosportdylus gigas (Cope I892) were inciuded in the species (Osborn l9l6). The most comple te T. rex skeleton,

AMNH

5027, was aiso excavated by Barnum Browrr from the Hell Creek Formation of Montar-ra in 1908. Because there were so few specimens, most people belier,'ed thatT. rex \4ras rare.

A dinosaur renaissance beginnir-ig in the

1960s ir-rspired many paleontologists to seek out nelv and more complete specimens. Since 1965, 42 skeletons (5% to 80% complete b1' bone cor-rnt) of T. rex have been excavated from the \\'estern Interior of North America. To date, T. rex has been

found in the uppermost cretaceous terrestrial rocks fron-r central Alberta to sor-rthern Ner'v Mexico, ard from north-central South Dakota to central Utah. These skeletons, along lvith innurnerable numbers of bones and teeth, have been discovered, excar,'ated, displaved, and written about rn numerous scientific and popular books and publications.

The discoverl,' of the Trrannosaurus specimen knou,n as Sue and its subsequent publicitv (Glut 2000; Fiffer 2000; Larson and Donna' 2002)

rll.ors of Sue's value lured dozens of anrateur paleontologists and untrair-red fortune hunters into the field. Although nost knelv r-rothing about collecting or caring for fossils once thel,were discovered, people u'ere looking for dinosar-rrs in areas that no one had e'er searched. within tl-re last l5 years, most exposures of the Hell creek and reignited this renaissar-rce. The

Lance Formations have been explored, resulting in many nerv specimens ofTyrannosaurus a.d other dinosaurs being discovered. These new Tyrcnnosaurus specinens hal'e l'ielded more information about T. rex than was once thotight possible, as evider-rced by this volume. Much has norv been learned about the respiratorl', digestive, ar-rd reproductive systems, feedirrg habits, range? sex, lifesir'les, ir-ijuries, and diseases of tl-re tyrant-lizard king. These neiv specimens have provided data on arn and jarv strength, speed, ar-rd grow,tl-r rate, and findings have bolstered the finding of a close relationship of bird and theropods. Because of these neu discor.eries, the once-rare T, rex is now one of the rnost abundant large theropods in many museum collections. An ar-rnotated catalog of these specirne.s is presented below.

One Hundrec /?ars offytannosaurus rex

1.1 . Site map for Tyrannosaurus rex discoveries. See text and Table 1.1 for number

Figure

identification.

Tyrannosaurus rex Specimens

Brief descriptiorrs follow each of the more coniplete Tyrannosaurus rex specirnens recovered to date. Each listed specirnen has a minimum of l0 associated skeletal bones frorn several parts of ihe bodv or a fairll, con-rplete skull. The list exciudes specinens consisting of onlv a braincase and/or a few skull bones, or on11'foot bones, or onli' caLrdal bones, as r'vell as the countless specimens of T. rex teeth and isolated bones. Altl-rough there rna1, be some omissions, the total number of skeletons is particularly impressive rvhen considering that rnost of tl-rese specinens have been found in the last l5 I'ears. Considering tl-re r,r'ide geographic range of the specimens, and assuming there is onlv one North American species, the paleogeographic rar-rge of T rex was imn'iense-possiblv larger than that of most other large

theropods (Fig. l.l).

Altliough some authors have consideredNanotyrannus lancensis (Bakker et al. 1988) s,"-nonymor-rs rvith T. rex (Calr 1999; Carr and Williarnson 2004; Hoitz 2004; Glut 1997, 2000, 2001, 2006), others (Bakker etal. 1988; Cr-rrrie 2003; Larson this volurne) do not agree. Tooth count, bone shape, and foramen placernent and size, along with manv other skeletal differences, seem to clearh' separate the 2 genera. Because there is so r-nr.tch evidence separating Nanotyrannus from T. rex, I have exclucled Nanotvrannus from the follou'ing list of T. rex specimen s. AtLhlysodon molnari Pavl, 1988 (=Stlgivenator molnarl Olshevsk'',, Ford, and Yamamoto, 1995), was excluded for similar reasons. The follou'ing Tyrannosaurus rex skeletons har''e been assigned a percentage of completeness on the basis of the number of bones four-rd rvith each skeleion. Tl-re totai nurnber of bones ir-i a skeleton of T. rex is approxirnatelt

300 (Appendix). A11 identifiable bones, u'hether complete or incomplete, are counted as bones in the totals. For uanl' skeletclr-rs, some bones r'r"ere fragmented or eroded, and others rvere fragrnented before br,rrial. In most tttstances, if the incomplete bones can be positivelr,identified, thev are treated as complete bones for the prlrpose of calculating the percer-rtage of completeness for each skeletor-r. Ever,v effort was made to ai'oid inflating the count (for instance, rib heads u'ere counted but rib shafts i.r,ere not, unless the1, coulcl be proved to be from separate ribs alreadr,counted). The completeness of a skeletor-r u'as then derived bl dividing the nun-rber of bones found lvith each specimen by the total number of bones in a skeleton. I atterrpted to locate and list all Tyrannosauru.s specimens collected fronr the upper Maastrichiian terrestrial rocks of North Arnerica. A11 specirnens are listed, whether they are in private hands or pubiic institutions. Anv errors or omissions are solely'my responsibilitr'. All knorvn ir-istitutions, repositories, ancl privaie collectors that ma1'haveTyrannosduruE rex skeletal elements rrr

their collections were contacted for data, and most \\,ere cooperative. The following specimens are listed chronologically'and alphabeticall,v b1'their catalog number and/or their nickname or moniker. The vear of excavation is given ratl-rer than the year of discovery becattse some of them were not excavated

until many

Neal L. Larson

decades after they r'r'ere initiall,v found (Table 1.1).

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1900-1909

The years 1900 through 1909 markecl the dan n of our understanding of Tyrannosaurus rer. This decade includes the initial discoverl'and description of Tyrannosaurus rer Osborn 1905. Four incornplete skeletons of T rex were unearthed durir-ig tl-ris tirne, ancl each one u'or-rld contribute tremenclouslv to the knorvledge of this magr-rificent dinosaur (Osborn 1905, 1906, 1912, 1916). Nearly 60 years rvould pass before any other skeletons rvere collected, and it would be nearly, $Q more years before ideas of holr' they lived, acted, and u,alked lvould change.

BMNH W994 (OriginallyAMNH

5866)

(Holotype of Dynamosaurus imperiosus Osborn 1905) DISCovERED: The year 1900, Barnr-rm Brorvn, a professional collector

employ'ed bv A\,INH.

LocArIoN:

Seven

Mile Creek, \Veston Count,v, WY (Fig. l.l, site I).

FoRMATIoN: Lance Forrnation. EXCAVATED:

American I\4useurl erpedition r-rnder Barnun-r Brorvn, 1900.

REPosIToRY: Natural History Museunr, London, England, UK. AceuISITIoN: Purchased frorn the American N{useurn of Natural Histor,v, 1960. DESCRIBED: Osborn (1905, 1906); New'man (1970); Carpenter (1990);

Glut

(1997).

ofboth palatines and both dentaries. T'he postcranial skeleton has all l0 cervical vertebrae, plus 9 left and 4 right cervical ribs. The first 5 dorsal and the 5 sacral vertebrae are also preseni, along rviih the right ilir-rn, the left ischiurr,

sKELETAL REN{AINS: The skull consists

and the right femur. CoN{PLETENEsS: Forty bones, or I}% of a skeleton bi'bone count.

oN DISpLAy? Yes, according to Phillip Manning (persor-ral communication 2005); some parts, the dentar,u-, and maybe another bone or til'o, are displaved at the Natural Historv I\'{useum, London, England, UK. coN,IluEN'I's: Th.isTyrannosdurus rex specimen had the first articr,rlated neck ri'ith cervical ribs. It q'as discovered with numerous scutes of rvhat is norv knorvn to be from an Ank,-losaurus (Carpenter 2004). The species was s-vnonvmized r,vith Tl,rarLnosaurus rex b-v Osborn (1906) in his second contribrrtion onTyrannosaurus.

cM

9380

(Originally AMNH 973) (Holotype of Tyrannosaurus rex Osborn 1905) DISCovERED: The vear 1902, Barnun'i Brown, a professional collector

emploved by AMNH. LocATIoN: Frorn Quarry'No. I, near )ordan, Carfield Countl', NrIT (Os-

born 1905) (Fig. I.l, site 2). FoRNIATtoN: Hell Creek Formation, 220 feet above tire Bearpaw Shale.

Neal L. Larson

tl-tt

,

[.xcA\ATED: American N{uscum erpedition, under Bamum Bronn,

1902-r905. REposIroRy: Carnegie N{useum of Natural Historr, Pittsburg, P-\. ACQLTtsITION: Purchased frorn the American Nluseum of Natural His-

ton',

1941.

DESCRIBED: Osborn (190i, 1906, 1912, 1916);Carpenter (1990); Gltrt

(1ee7) sKELETAL RE\,IAINS: The partial skeleton cottsists of the right tnaxilla,

both lacrimals, left scpran'iosal and ectopterr goicl. both dentaries, ancl the left surangular. It also has I cervical. dorsals, and 5 sacral iertcbrae; 3 gastralia; right scapula and lelt hr-itrertts; both ilia, pubes, and ischia; the left fenur and part oi thc right tibial ancl 3 metatarsals (N{clnbsh 1981).

Figure 1 .2. CMNH 9380, skeleton on display. Photo by Peter Larson.

Figure

'1

.3.

AMNH

1,,ffi

5027, skeleton on display Photo courtesy

iffi

AMNH library.

w

Co\'IPLETENEss: 'l'hirtv-four bones, or lI% of a skeleton by bone count. oN DISpLAy? \Vas on clisplav at the Carnegie Nluseum of Natural Histon,, Pittsburg, PA, since the earlv 1940s. In 2005, the skeleton n'as disrnantlecl, br-rt it is scheduled to be fresl-rl1.'restored, remounted, ancl back on displal'sometime late 2007.

coll\IENTS: The American N4useurr of Natural Historl' sold the skeleton soon rfter tire beginning of World \nVar II. It has often been stated that it ri'as necessarv to ensure that aTl,rannosdurus rex rvor-ild survive in the er.'ent of a bombing. Because the skeletal pose had not been reclone sir-rce it r.vent on clisplay' in the 1940s, the Carnegie NIuseurn of Naturai Historv is r-rorv in the process of conserving and renrour-iting the original skeleton.

Neal L. Larson

cM

1400

DISCovERED: The year 1902, Olaf Peterson, a professional collector ern-

ployed by Carnegie Museum.

LocArIoN: Snyder Creek, Niobrara County, WY (Fig. l.l, site

3).

FoRMATIoN: Lance Fornattott. EXCAVATED: Olaf Peterson and Carnegie Museum expedition, i902. REposrroRy: Carnegie Museum of Natr,rral History, Pittsburg, PA.

Mclntosh

DESCRIBED: Partially described

b1,'

sKELETAL REMAINS: Mclntosh

(l98l) noted that CN{ 1400 contains the

(1981).

left maxilla, premaxilla, and pter,vgoid, the nasals, and the braincase. The postcranial skeleton consists of2 cervical ribs, I dorsal vertebrae, I dorsal rib, 3 chevrons, the left ischir-rrn, ancl both pubes (incornplete). coMPLETENEss: Th'enty-nine bones, or l0% of a skeleton bv bone count. ON DISPLAY? NO.

coMMENTS: Because the Carnegie was in possession of this large tl-reropod specimen, it encouraged Osborn (1905) to publish onTyrannosdurus rex earlier than he originall,v ir-rtended (http://paleo.arnnh.orgl pro

jects/t-rex/index.htrnl).

AMNH

5027

DISCovERED: The year 1908, Barnum Brotl,tl, a professional collector

emploved by

AMNH.

LocArIoN: Near Dry Creek, McCone County, MT (Fig. Ll, site 4). FoRMATIoN: Hell Creek Fort.nation, 220 feet abo.",e the Bearpat' Shale. EXCAVA:I'ED: American Museum field creu'under Barnun-r Brot'n, 1908. REPosIToRY: American Museum of Natural History, Ne"r,York. DESCRIBED: Osborn (1912, 1916). sKELETAL REMAINS: The specimen boasts the first cornplete skull, all

of

the cervical, dorsal, and sacral vertebrae, ph-rs l8 caudal vertebrae and 7 chevrons; 9 cervical ribs fron-r the right side; 20 dorsal ribs; both ilia, iscl-ria, and pubes. COMPLETENESS: A total 0f I43 bones, or 48%, of a skeleton bv bone count. oN DISPLAY? Yes, at the American Museunr of Natural Historl', Nerv York. coMNIENTS: This specimen of Tyrannosourus rex r.vas the classic one, the best T. rex skeleton on view, anyrvhere r-rntii Sue and Stan \\'ere prepared in 2000 and 1995, respectivel,u-. The skull and much of tl-re skeleton were articlrlated, but the skeletor-r lacked legs, feet, fore-

limbs, and the distalend of the tail. With l4J bones, this u'as the most completeT. rex skeleton until 1990 n'ith the excavation of MOR 5t5 (146 bone$ and a T. rex named Sue (219 bones). In 1996, the skeleton, which had beet-r mounted in an upright position, u'as remounted into a more natural pose. There are casts of the skull and of the skeleton in r-r.rttseum coilections throtrghoLrt the u'orld.

Onc

Hrtre..' ..;.c

nfTvrannosaurus rex

Figure 1.4. MOR 008, cast of skull. Photo by Ed Gerken.

1

91

0-1 959

Wars, mmors of i,r,ars, and the Great Depression kept manv paleontologists out of the field and in the lab frorn the 1910s tl-irough the 1950s. Although there n'as onlr'' some dinosaur collecting fron [Jpper Cretaceous formations

undertaken during this period in the United States, tl-rere rvas substantial coilecting in Car-rada. Solre paleontologists, such as the Sternberg familv ancl Barnum Btolvn, did ertcnsive collecting in Alberta, helping to build tl-re collections and displar,s in the n-rajor rnLlselll-ns of Canada, Europe, and the Unitecl States. It u,as also dr-rring this time that Rov Chapmar-r Andreu's discovered an entirely nen' Late Cretaceotrs clinosaur fauna in N4ongoha, n'hich rvould later include tl-re ,,\sian tvrannosanrid ,Tarbosaurus.

1960-1979

Beginning

ir-r the rnid 1960s, neu'clinosaur finds once agair-r began to iure more people into tlie fielcl, ar-rcl manl' amateurs u,ould make imporiant discoveries. Nen'discoveries in Ntlontana rvould begin to establish the Museurn of the Rockies and Los Ar-rgeles Cour-rtv N{useum as major repositories for dinosaurs. For tl-re first tirre, non-East Coast nuseurns u,ould possess original specirnens of the tvrant-lizard king. Disco."'eries of Deinonl,chiis ancl tlie resr-rltar-rt revolutionar,v concepts about dinosaurs b-v fohn Ostrom (Yale LJnir,ersit-v) u,ould help to change the way \ve looked at dinosaurs. Mar-rt'n-rodern researchers n'ould use Ostrorn's

Neal L. Larson

brilliant research

as a springboard to presenlTtrarutosaurus and other dinos:tlrs as active,',r'arm-blooded, birdlike animals instead of cold-blooded, lizarcllike creatures (e.g., Bakker 1986; Paul this volurne).

MOR 008

In 1967, bv Dr. Williarn N4acN4annis, an archeologist from Nlontana State Universitv (Larson and Donnan 2002). LocAr'IoN: Carfield Countr,, N'lT (Fig. l.l, site 5). FoRN{ArtoN: Hell Creek Formation. EXCA\ATED: A teanr from the Nlluseurr of the Rockies, 1967. REPoSIToRY: Vluseurn of the Rockies, Bozeman, MT. DESCRIBED: Partial description in N4olnar (1991). sKELETAL REN{AINS: The skull is rnissing or-r}y the left premaxilla, the riglrt pllrtirre. the riglrtepipterrgoid. arrd tlre torner. Tlre louer jau is missing the splenials, the coronoids, the right dentary, and the left DISCo\IERLD:

prearticrrlar.

\r

atlas is al'o preseut.

Co\'IPLETENESS: Fortv-sir bones, or 15% of a skeleton by bone count.

oN DISILAv? A cast of the skull is on display at the Black Hilis Museun-r of NaturalHistorl', Hill Citv, SD. coM\{E\rs: T}re specimen consists of only an articulated skull and the atlas of a ven'large (Sue size), robust adult. It was on display at the Nluscurn of the Rockies until 1990. wher-r it was moved to the collections. Portions of this skull rvere molded and cast to supplernent the r-nissir-rg portions of \{OR 555 (a gracile Tyrannosaurus rex).

LACM 23844 DiscovERED: 'l'he vear 1966, Harlet,Garbani, plumber and arnateur paleontologist (Dingus 2004). LocA'r'IoN: L. D. Engdahl Ranch, Garfield Cour-ri1', MT (Glut 2002) (F-ig. 1.1, site 6). FoR\,tA'f IoN: Hell Creek Forn-ratior-r.

LACN{ field crerv, 1967-1969 (Glut 2002). REPoSIToRY: Natural Historr' \4useun of Los Angeles Count\', Los Angeles, CA. DESCRIBED: Partial clescription of the skr-rll in Nlolnar (1991); see also EXCA\,ArED: J. R. N,{cDonald and

N,Iolnar (this volun-re). sKELETAL RENIAINS: 'l'he skull consists of the right prernaxilla, maxilla, postorbital, squarrosal, and ptervgoid; both jugals, both iacrirnals, the left quaclrate ancl cpraclratojugal; nasals; frontals and the occipital; both surangulars, dentaries, articulars, and angulars; the left spienial; and

prearticrrlar.'fhe postcranial skeleton consists of2 cervical, 7 dorsal, ar-rd

4 caudal vertebrac; 5 ribs; 10 chevrons; the right scapula, fentur, both ischia, left tibia, 4 netatarsals, and l0 pes

arrcl astragalus; and

pl-ralanges. tr'{ani'of the bones are incomplete rClut 2002). CoN.IPLETENESS:

Seventr.four bones, or 25% ofa skeleton by bone count.

Onp

Ht

tr

nf Tvr:n1653g1'95

g'px

1

1

'i'.'

Figure 1.5. LACM 23844, skull. Photo by Dick Meier, courtesy Natural History Museum of I

n< A nnolo< Cnt tntrt

li;l

oN DISPLAY? Yes, at the Natural History Museum of Los Arrgeles Countv, Los Ar-rgeles, CA. coMMENrs: The skull and partial skeieton lvere disarticr,rlated and provided the first detail for rnanv of the bones (Molnar i991). The specimen rvas excavated over the span of severai field seasons. The rancher assisted bv bullclozing the overburden a\vay (Dingus 2004). There are several casts of this skr,rll on displav throughout the r,vorld.

LACM 23845 (Holotype of Albertosaurus megrdgracilis Paul 19BB and of Dinotyrannus megragrdcilis Olsheysky et al. 1995) DtscovERED: The year 1969, Harle1'Garbani, plumber and arnateur paleontologist (Dingus 200'1). LocArIoN: L. D. E,ngdahl Ranch, Carfield Countl', MT (GlLrt 2002)

(Fig.

l.l,

site 7).

FoRx,IATIoN: Heil Creek Formatiorl. 12

Neal L. Larson

EXCAvATED: Harlev Carbar-ri and the

t,AC\l field creri', 1967 (Dingus

2004). RtjPosIToRY: Natural Histon' Mnsenm of Los .\ngeles Countr", Los Angeles, CA. DESCRIBED: N{olnar (1980); Paul (1988); Olsherskv et al. (1995); L:rrsou

and Donnan (2002); Carr and Williamson (2004). sKELETAL RE\'IAINS: 'l'he skull consists of the right

marilla, right lacri-

mal, frontals, nasals, p:rrietals, both dentaries, right coronoid, and right surangular. The postcranial skeleton has the rigl-rt scapula, coracoid, and ulna; both iscliia; the right fernur, tibia, and astragalus; a nearlr conrplete right foot (missing metatarsals I and IV and tl-re piialanges from the first toe); and there are also 2 phalanges fron tl-re left foot (R. Farrar, personal comrrunication 2005). co\lPLETENESS: Thirt\.seven bones, or 12% ofa skeleton bv bone cotrnt. ON DISPLAY? No.

'l'his specin-ren is a juvenileTt-rdnnosdttrus rex (P. Larsor-r, pcrsonai cornnrunication 2005; Carr and Willianrson 2004). It u'as discoverecl about 2 feet abor''e LACN{ 27844, in scrap piles that u'ere created il,hile bullclozirtg the overburclcn alr'av from the lou'er T rex. Bccause of bulldozing, niuch of the skeleton r'r'as fragnrentarr'(Diir-

CoN{},,ttiNTS:

gtrs 2004).

Sevcral ncn and inrportant skeletons u'ere founcl cluring this decacle. The frlstTyrannosdurus skeletons fronr South Dakota, Nen'Nlexico, and A1berta irrcreasecl the knonr-t range of T. rex bt'hundrecls of miles in all directions. (X,Ianospondt'lus gigas Cope, 1892, n'as collected frorn South Dakota, but that specirnen consisted of onh' 2 cervical vertebrae.) Tori'ard the e nd of this decade. one of the Alberta T. rer skeletons n'or,rld become the first originai T rex skeletons to tour the n'orlcl.

The 1980s

SDSM 12047 (Mud Butte T. rex) DISCovERED: 'I'he vear 1980, Jcnnings Floden, rancher and al.rateur fossil collector (Larson ancl Donnan 2002).

Loc:\TIoN: fennings F'loclen Ranch, near Zeona, Btrtte Countr', SD (Fig. 1.1, site 8).

oRuATIoN: Hel1 Creek Forrration. EXC.l.vAIED: Phil Bjork, Jennings Floden, ancl neigl'rbors 1981; Floden ancl neighbors I981. REPosIToRy: N'lusenrrr of Geologr', South Dakota School of Mines and 'l'echnologr', Rapid Citr,. DESCRIBED: Partial clescripiior-r bv Bjork (1982); Carpertter (1990). sKh,Lli'rAl RENIAINS: Ne:rrlr'cornplete skull, ntissing ortli'the prernaxil1ae. The lon'er jan'has both dentaries, thc right :rngular. and the right coronoid. The postcranial skeleton ir-rclLrcles parts of J ribs ancl F

One

ltu'c'=:

.a's of Tyrannosaurus

rex

l3

F

gure 1 6. SDSM 12047,

s<,i on drsplay

'.'-t..-

:'a:a c.

as

of Geology. Peter Larson.

has a conrplete section

oftail fron the i5th to the l4th cauclal (in-

cluding chevrons). CoNIPLETENESS: Eight1.61e bones, or 27% of a skeleton b1' bone cour-rt. ox nlspley? Yes, the skull is on display' in the N{user-rrr of Geologl',

Rapid Citl', SD.

initial digging in 1981, the Sor-rth Dakota School of Nlines hacl found the skull, some.n'ertebrae, and sorre ribs. Floden beliei,'ccl that more of the skeleton li,as still in the grourld and recruited neighbors to reopen tlie dig. 'fhev unco."'ered the skull n'ithin a ferv clavs. T\,1,o 1,ears later, thev discovered articulated tail vertebrac ar-rcl the seconcl lolr'er iar,',' (Smith-Hill 1983). Associated rl,ith tl-re skeleton n'ere elements frorn a gar (Lepisosteus'),2 turtles (inclucling a baenid), 2 crococliles (Branchycharnpsa and Leidyosuclrus1, CharnpsosdurLLs, ancl the teeth frorn the iheropod Nanotyrannus (Bjork 1982). The skull and skeleton are currentlv being preparecl, ar-rd a description of the specir-nen is also plannecl.

coNINIENTs: After the

RTMP.8l.12.t (Huxlet: T. rex) DISCovF,RED: 'I'he 1,'ear 1946, Charles

\,{. Sternberg,

a profession:rl

paleontologist. LoC.\rIoN: Near tl-re tou'n of Huxlev, along the Red Deer River, Alberta

(Fig.

1.1, site 9).

FORNIATIoN: Scollard Forrnation.

Neal L. Larson

EXCAVATED:

Phii Currie rvith the Provincial \luseum of Alberta. Ed-

monton, in l9BL REposIToRy: Royal T1''rrell Museum of Palaeontologr, Drr-rmheller,

Alberta. ACeuISITIoN: Transferred from the Provincial \luseurn of Alberta ir-i Edmonton. DESCRIBED: Partial description by Cr-rrrie (1991). sKELETAL REMAINS: From the skr,rll, onlr" a righi postorbital exists. The postcranial skeleton consists of B anterior caudals, 5 anterior chevrons, part of the sacrr,rm, 7 anterior dorsal vertebrae, I rib, both ilia, left ischium, left pubis, both femora, both tibiae, both fibulae, right astragalus and calcaneum, the 2 right tarsals, I netatarsal, and 7 pes phalanges from the right foot (A. Neuman, rvritten commttnication February 1994). CoMPLETENESs: Forty-nine bones, or 16% ofa skeleton by bone count. oN DISpLAy? Yes, at the Royal lvrrell Museum of Palaeontologv, Drumheller, Alberta. coMMENrs: Sternberg found the specimen halfu'av dou,n a steep cutbank or-r the Red Deer River in Alberta. He believed that the specimen was mostly gone, so he clid not atternpt to excavate it. Cr,rrrie, while investigating some of Sternberg's earlier finds, detennined that itlvor,rld be worth excavating to see rvhether there rvas more of the skeleton (Currie l99l). At 52' north latitude, this is the norti-rern-

mostTvrannulurus

rex.

One

Hurc'::

=a's ofTyranrosaurus rex

Figure 1 .7 Huxley-rex, RTMP 81.6.1, mixture of real bones and cast, with oilginal pelvis in foreground. Photo hv Pofar I ar
15

Figure

1

.8. Black Beauty

RTMP Bl .6.1, cast skull. Ph^f^ h\/ tsd ( -arkan

RTMP 8I.6.I (Black Beauty; Cowlet T. rex) DISCovERED: T'he y'6a1 1980, Jeff Baker, a l-righ school student (Currie 1993).

LocATIoN: Ncar the confluence of tl-re Cron'snest and Willoli'Rir,'ers (Crou'snest Pass) in southr.r'estern Alberta (Fig. I.l, site l0). FoRIIATIoN: Willoq' Creek Formation. EXCA\ArED: Phil Currie rvith tl-re Provir-rci:rl Nlluseum of Alberta. Edrnonton, in 1981. REPoSIToRY: Royal T1,'rre1l Nluseum of Palaeontologl', Drurnheller, Alberta AcQUISIIIoN: Transferred frorn the Provincial Nrluseurl of Alberta in Edrnonton. DESCRIBED: Partial description b1, Carpenter (1990) and Currie (1991). SKELETAL REMAINS: Accorclir-rg to Ctrrrie (1993), tlie specimen consists of a r-rearll' con.rplete skull but onh' partial lon'er jau's (it has both dentaries, tlie left splenial, and the right angular). It also has 5 cervical and 7 dorsal vertebrae; 2 cervical ancl B clorsal ribs; a right humenls; a nlanus phalange; both femora; both tibiae; the left fibr-rla,

Neal L. Larson

calcaneun, and astragalus; 4 metatarsals; and 5 pes phalanges (A. Neum:rn, n'ritten coinrnunication Februarr 1994). Co\{PLETENEss: Eigl-rti-fir,'e bones, or 28% of a skeleton b1' bone count. oN DISII,AI? Yes, the skull is on clisplav at the Roval lvrrell Mr-rser-im of Palaeontologv, Drun-r1-reller, Alberta. The skeleton has been part of an international trar.'eling exhibit. cox,INIENrs: Black Beautv got its name from its beautifully coiored black bones. It n,as discovered w'hen Jeff Baker took a break fron-r fishing and n'ent ri alking in the hills. This u,ould be the first T. rex to receir,e :r nicknarne. but it r.r'oulcl not be the last. It fras an articulated skrill sholving minor distortion. It becarne the first Tyrannosaurus rex skeleton to go on tour, spending considerable time traveling across Canacla ancl Japan. This specirnen is the rvesternmost Tyrannosaurus rer, found at 114' i,r'est longitude.

MOR 009 (Hager rcx) DISCovERED:'l'he i'ear 19EI, N{ick Hager, forrner director of the N{useum of the Rockies (Larson and Donnan 2002). LocA'rIoN: Garfield Cotrntr', NiT (Fig. l.l, site Il). I,'oR\iA'f IoN: Hcll Creek Fomration. EXCA\A'I'ED: \,luscun-r of the Rockies field crerl,, 1981. REposIToRy: \'lusenm of the Rockies, Bozeman, NIT. sKELE'IAL RENTATNS: 'l'he skeleton consists of the right dentarv, parts of 4 ribs, 22 cauclal vertebrae, and 7 che','rons; the right ilia, both ischia, ancl botl-r pubes; both fernora (left incon-rplete), tibiae (incomplete), the right fibula ancl astragalus; and 4 metatarsals and 7 pes phalar-rges (P. l,arson, personal comrrnnication 2005). coNrPLErENEss: Fiftl-eight bones, or 19% ofa skeleton by bone count. ON DISPLAY? No.

CoNIuENrs: There is a good possibilitl that n.rore of the specimen rer-nains uncollectecl (N,{ick Hagar to P Larson, personal communica-

tion 2005).

NMMNH P-IOI3-I DISCOVERIID: 'l'he r,ear 1982, D. Staton and J. l,aPoint, amateurs. LoCA'l'IoN: 'l'he east side of Elephant Butte Reservoir, near Truth or

Conscquences, NNI (Fig. I.1, site l2). F'oR\,IAt'IoN: tlall Lake N{ember of the \'{cRae Forrnation. EXcA\A't'LtD: Cillette ancl staff fror-n tl-re Neri' \{exico Nlluseurn of Natural Histori' 1983; Tom Williarnson, September 2003. REposIToRy: Nen' N,lerico \'{useuni of Natural Historr', Albuqr-rerque,

NNI.

Wil\\/illianson (200-ltr and Williamson and

DESCRIBED: Partial clescription bv Gillette et al. r1986); Carr and

lian.rson (2000); Carr and

Carr (2005).

One

Hunire:

/ears ofTyrannosaurus

rex

17

SKELETAL RE\tAINS: The specirnen consists of a left dentarv, an incomplete palatir-re (originalli, identified as an articular), a right prearticu-

lar, some incomplete teetl-r, and a nearlv complete chevron (Gillette et al. 1986); a right squamosal and postorbital; an articular, splenial, and at least 2 cl-revrons; and some tooth fragrnents (Ton-r Williamson, personal communication 2005). coMpLETENEss: Ten bones, ot )% of a skeleton by bone count. oN DISpLAy? Yes, the loli,er iau' is on displav at the New Mexico NIuseum of Natural Historv, Albuqr,rerque, NM. CoMMENTS: ThisTtrannos(llLrus rex extendecl tl-re known range in the northern Creat Plains south IJ00 km nearly to the Mexican border. The specin-ren rvas found in an area that is normalll'subrnerged beneatl-r the Elephant Butte Reservoir. It r,"'as discovered I,vhile D. Staton and J. LaPoint u'ere taking a break frorn a saiiboat outing (Gillette ei ai. 1986). T'he lon' level of the reservoir in 2003 gave Wiiliamson the opportunitv to return to the site and collect more bones sorre 20 vears after its irritial excavation. 'l'his specimen is the southernmostT. rex at lJ" north latitude.

The 1990s

The

1990s became the decade for the rnost incredible'fyrannosaurLLs rex discoveries, with nearly til'ice as many' specimens found and excavated than in all of the -vears before. With the J n-rost conplete T. rex skeletons excavated ir-r the first 2 ,vears, rvl-ro could have expecied that there would be so manv more specimens found? And rvho could have anticipated all of the ptiblicitl,and controversies that some of these dinosaurs would generate (e.g., Dal'ies 1997; Donnan and Cotrnter 2000; Glut 2000, 2002; Fiffer 2000; Larson and Dor-rnan 2002)?

MOR

555

(Wankel rex; Devil rex) DISCovERED:

'fhe l'ear I988, Cathl'Wankel, novice.

LoCATIoN: From tl-re sor,rth side of Fort Peck Lake, NlcCor-re Countr,, MT (Fig. 1.1, site l3).

FoR\{ArIoN: Hell Cieek Fornation. EXCAVATED: Pat Leiggi ar-id N{useum of the Rockies field crew, REPoSI'I'oRY: Museum of the Rockies, Bozernan,

1990.

M'f.

DESCRIBED: Partial description bv Horner ancl Lessern (]993); described bv Carpenter ar-rcl Smith (2001).

forelinb

SKELETAL REN,{AINS: The skull cotrsists of a conplete braincase, right dentarr; left maxilla, nasals, vorner, both squarnosals, both postorbitals,

both cluadrates and quadratojugals, both jugals, both lacrimals, botl'r pten'goids, and both epiptervgoids. The skeleton consists of both scapulae ar-rcl coracoids, the left arm ancl most of the left hand (rnissing onlr' 3 bones), conplete legs and left foot (minus I phalange), plus the right II, III, and V rretatarsals. Also collected vn'ere a cornplete pelvic girclle (including the sacmn), nearh'all of the dorsal and cervical vert8

Neal L. Larson

*.

tebrae (rnissing onli'tl-re atlas), the first 14 caudal vertebrae pltrs 1 additional, 6 cl-revrons,'[ dorsal ribs, and 5 ceri'ical ribs. coNIPLETENESS: Fourteen bones, or 49% of a skeleton bv bone cotrnt. ox orspr-,qv? Yes, a portion of the skeleton u'ent on displav in 2005 at the

N{useum of the Rockies, Bozemar-r, NIT.

rnanv othe rs. A bronze casting of this clinosaur mav also be vie"r''ecl outside the \,,luseun of the Rockies, Bozeman, N'lT.

FN,{NH PRzOBI

BHI 2033)

DISCovERED: T'he vear 1990, Susan l{endrickson, arnateur archeologist

and paleontologist. LocA'rroN: Nlaurice Williams Ranch, north of the tou'n of Iraith, Ziebach Cor-u.rtr', SD (fig. 1.1, site 14). I.oR\IA't'IoN: Hcil Creek F'orrration, about I5 feet aboi'e the contact lr'ith the For Hills F-omation (P Larson, personal cotrmttnication 2006). EXCA\ArED: Black Hills Institute fielcl cren from Ai-rgust 14 to September

I,

1990.

REposITORy: Field l,Iuser,rm of Natural Historr. Chicago, IL. .\CQLTISITIoN: Sothebr"s Auctiorr, 1997. DESCRIBED: A full description of tlie skull and skeleton u,as publishecl bv Brochu (2003); it ri'as also partially'describe d br Larson (i994, 2000); c)np H'1.

": ' a.r. ofTvrannosaurus rex

ils:::

Figure 1.9. MOR 555, cast of skeleton. Photo by Ed Gerken.

co\'lxtENrs: This clinosar-ir n'as discor''ered n'hile Catht'\\/ar-rkel u'as hiking on a butte in thc Hell Creek Formation on the south sicle of Fort Peck Lake ul-rile tl're rest of her fanilv u'as fishing (Homer and Lesserr 1993). Some resin casts of tiris skeletor-r rt.rav be seen at the Dallas N{Lrsetrn of Natural Historl', Houston N,lluseurn of Nattrre ar-rcl Science, tJniversitl of California Nftiseum of Paleontologl, N{useunr of the Rockies, and Black Hills \,{usettm of Natural [{istort', among

(Sue, formerltt

,

19

F g-'e 1 1a Sue FMNH PP.2ABi during excava-

lian tA.); skull during preparation with Terry Wentz (B), on display at the Field Museum (C). Photos. (A, C)Peter Larson; (B) Ed Gerken.

Donnan ancl Connter (2000); Carpenter and Smith (2001); Larsorr and Dor-tnan (2002);and L:rrson and Rigbt'(2005). \vEB sI't'lt: http://u'u'lr,.fieldmuse urr.orglsue/ and http://lvr,r'r,r.bhigr.com/ pa ge s /i n foli n fo_su e. htm. SKI;LETAL REN,IAINS: A conpiete skull, 61 r,ertebrae (9 cerr,ical, 11 dorsal, 5 sacral, 36 cauclal),2i che',,rons, lJ cervical ribs, both proatlas, 19 dorsal ribs. It also has both scapulae and coracoids, the furcula. thc rigl'rt arn and nrost of the right hand, a cornplete peh,ic girclle, both legs, both calcar-iea ar-rd astragali, a tarsal, a nearll'corrplete right

foot (missing 2 bones), and a single pcs phalange frorn the left foot (Brochu 2003). CONTPLETENESS: A total of 2 19 bones, or 7)% of a skeleton bi' bo[re count. ox olspley? Yes, in 2000, Sue li,'ent on clisplav at the Irield Museum of Natural Historv, Chicago, IL. CoNIN{EN'I'S: 'l'he dinos:mr u'as named in honor of its discoverer, Sue Hendrickson. Tl-re skeleion'ur,as found along u,ith the rernair-rs of 3 other theropods (a partial iibia ald fibula from a\,rannosaurlts rex subadult, a frontal from a iu','er-rile T. rex, and a iacrin'ral from Nano-I'hescelosaurus, trrannus), several skeletal elements of stornach contents of FldmontosaurrLs, a turtle skull and scntes, crocodile teeth and p.rrtr. fish teeth and vertebrae, a r.aranid, abundant plants, and nolL-rsks.

No other dinosaur has provokecl so rnuch attention as a dinosaur groLrps, inclucling Black Hills Institute ancl the

naned Sue. Several Neal L. Larson

U.S. federal gol'ernrrent, laid claim to the bones {see Davies 1997; Dorrnan and Counter 2000; Larson and Donn:rn 2002; Fiffer 200[,. The Field Museurn of Natural Historr ir-i Chicago, aided by \Valt Disnev World, Ronald N{cDonald Hor:se. ancl other sources, ac-

quired Sue from Soihebv's Auction in 1991. The rights to the Sue tradernarked naffre \vere given to the Field \ltrseurr b-v BHI in 1999. On May 17, 2000, the Field Museum unr,eiied the prepared and mounted skeleton of Sue to the public. The Fieid N'luseum also developed 2 traveling exhibits around casts ofthe Sue skeleton.

BHI 2033 (Sue) and several other specirnens were used by Stephan Pickering in an r-rnpublished rlanuscript (Glut 1997) to establish a second species of Tyrannosaurus. Althougl'r there mav be reasot-is to erect a second Tyrannosaurus species from tl-re Late Maastrichtian of North American (Larson and Donnan 2002; Bakker, personal communication; Paul l9B8; Larson this',,olune), both Sue and Stan compare favorably rvith the type of T rex. As a side note, Pickering came to the BHI to str,rdy'some of the specirrens

usecl to fustifv the ner.r" species.

BHI3033 (Stan\ DISCovERED: The year 1987, Stan Sacrison, amateur paleontologist.

LocArIoN: The Niemi Rancl-r, near Buffaio, Harding Cottntv, SD (Fig.

i.l, site I5). FoRMATIoN: Hell Creek Forrnation, 16 m beneath the K-T boundarr.' (K. Johnson, written communication 2000). EXCAVATED: Black Hills Institute field creu'fron-i April 14 to NIay 7,1992; a few more skeletal elernents were collected in 1993 ar-rd 2003. REposIroRy: Black Hills h-rstitute of Geological Researcl-i, Hill Citv, SD. DESCRIBED: Partialll described in Donnan and Counter (1999); Larson (2000); Larson and Donnan (2002); Hurum and Sabath (2003); P. L.

Larson (this volurne); Larsson (this volun-re); Stevens et al. (this l'oh,rme).

wEB sIrE: http://wrvu,.bhigr.corn/pages/info/info-stan.htr-n. sKELETAL REMATNS: The skeietal elements collected r,vith Stan include: a

nearly complete skull (missing the rigl-rt articrrlar and the left coronoid); 59 vertebrae (9 cervicai, 14 dorsal, 5 sacral, 31 caudal); 24 cher. rons; 14 cervical ribs (including the proatlas); l2 dorsal ribs; a nearli.' complete pelvic girdle (the distal ends of both ischia and pubes $'ere weathered awav); left femora; both tibiae; the left fibula; both calcanea and astragali;

S

left metatarsals; ar-rd li pes phalar-rges.

coMPLETENESS: A total 0f 190 bones, or 67%

ofa skeleton bv bone

coLlnt.

oN DISpLAy? Yes, since 1996 at the Black Hills Institute of Geological Research,

Hill City, SD.

coN,IMENTS: Stan u,as the first of

nany Tyrannosaurtls

t"ex skeietons

found in Harding Countv, SD. It was nat.t-iecl in honor of Stan Sacrrsor-r, its discoverer. Soon after Stan founcl tl.ris clinosaur, he became discor-rraged because he was told that this skeleton u'as jttst another

One

Hunc'::

/ears offyrannosaurus rex

21

Figure 1.11. Stan BHI 3033, during excavation (A), disarticulated skull with Terry Wentz (B); on display at Black Hills lnsti-

tute, with Brenda Larson C). Photos: (A, B) Ed Gerken; (C) Larry Shaffer.

articnlated Triceratops. Tl're bor-res lav in the groi-rucl r-rrtil I992. when BHI bec:rme au'are of the skeleton and began excavation. Stan rvas found rvith Z r-ron-?] rex bones: atEdmontosaurus i.'ertebrae ar-rd an acid-etched'lriceratops tibia n'ith botl-r ends rnissing, bitten (Larson and Donnan 2002), ancl innumerable well-preservecl leaves

(fohnson 1996). Preparatior-r of this skeleton n'as conipleted in

Mal'

1995, and Stan r.r'ent on tour in Japan ur-rtil )une 1996 as part of the T rex \Vorlcl Tor-ir. Because Star-r's skull u'as disarticulated and so rvell preserved, it pror.,iclecl much nen informatioli on the osteologl'and rnechanics of tvrannosaurid skulls (Donnan ancl Cor,rnter 1999; Larson 2000; Larson and Donnan 2002; Hurtrrr and Sabath 2003; P. Larson

this volurne; Larsson tl-ris r.olume). Nlore than J5 cast Stan skeletons and 50 Star-r skulls are on displar,' in public and private institr-rtions worlclrvide, including: the Snithsonian hrstitr,rte, Washington, DC; Oxford Uni'n,ersitr; Oxford, Englancl, UK; North American N{useurn of Ancient Life, Lehi, U'll Kenosha Public \luseurn, Kenosha, WI; ancl National Science N{usetrm, Tokvo.

22

Neal L. Larson

Samson (Z-rex, NIr.

Z, Mr. Zed)

DISCovERED: The r,ear 1987, NIike Zimrnershied, landowner's son, amate ur.

LocA'lIoN: Donald Zimrnershied Ranch, near the )ump-off, Harding Countr', SD (F-ig. 1.1, site

16)

FoRNIATIoN: Hell Creek Fornration. EXc.\\ArED: Irred Nuss, Alar-r Deitrich, Steve and Stan Sacrison, 1992. REPost'foRY: Pri|ate, Grahan Lacey'. ACQuISITIoN: Purchasecl in 2004 frorn Fred Nr-rss :rnd Alan Deitrich for ar-r undisclosed arnourn. DESCRIBED: Partialh'describecl in Clut (2002); Larson and Donnan (2002) wLt B

strE : htip://ivri'lr'.carnegiemnh.orgiditil'/paleolab/samson/index.htrn.

sKELETAI, REuAINS: According to Dale Rr-rssell (personal communica-

tion

1997), the skeleton has a nearh'con-rplete skull, 9 cervical and 7

clorsal vertebrae, 2 cervical and 10 dorsal ribs, 17 caudals, at least 4

chevrols, both femora, lcft fibula, abr-rndant tibia pieces, 3 metatarsals, ancl

l0

pes phalanges.

co\{pr,ErENESS: A total of I2l bones, or 40% ofa skeleton by bone coulrt. oN DISPLAY? Yes, cr,rrrentlv at the Carnegie N{ttsettm Paleo Lab il,hile undergoi n g preparation. coN,I\IENTS: 'l'lre landon'ners knen' that this lr'as a of a Tyrannosaurus rex skeleton as earlr'as 1987. In I992, professional collectors Fred Nuss ancl .\lan Deitrich, fron Kansas, contracted ivith the landowr-rer and procccded to ercar,ate the skeleton. They named it"Z-rex" for the first lettcr of the landorr'ner's last nan-re. The skeletor-r and skr,rll u'ere

one H'tr

----

.a.< n/ Tvrannosaurus rex

Finrrro 1 'l 7 (:mcnn (Z-rex); anterior view

of skull block (A); side view of skull (B). Photos courtesy Dale Russell.

23

then transportecl to Kansas for storage. It was repeatedly'offered for sale over the next dozen vears. Z-rer becarne the first T. rex olfered for sale over the Internet and r'"as offered for sale in the Wall Street foun-ral on April 27,1999 (GlLrt 2002). The specin'ren r,r'as acquired by international businessman, Graham Lacev, r.vho changed its narne fron Z-rex to Sanrson and transported to the Carnegie Nltrseurn in Pittsburgh, ll'here it is currentlr, undergoing preparation. Sarnson's preparation can be observed in the Carnegie Museum Paleo Lab. N{ore inforn-ration on Samson carr be obtained from Glut (2002, p. 578).

DMNH

2827

DISCovERED: The vear 1992, Charlie Fickle and his dog, both an-rateurs.

LocArIoN: A housing developrnent, Littleton, CO (Fig.

1.1,

site l7).

F'oRN{ATIoN: Lolver part of the Denver Formation.

EXCA\ArED: Collected b1' the Denver Museum of Nature under the clirection of Kennetl-r Carpenter, 1992.

& Science

REPoSIToRY: Denver Museum of Nature & Science. Denver. CO. DESCRIBED: Carpenter and Yotrng (2002). SKELETAL REN{AINS: Carpenter and Young (2002) reported that the par-

tial skeleton consisted of a left femur, ilium, scapula, and coracoicl; right tibia. fibr-rla.

ar-rd

astragalrs; a distal caudal vertebrae, ribs, and

3 teeth. CoMPLHTENESs: Twelve bones, or 4% of a skeletor-r by bone count. oN DISPLAY? 1'es, some of tl-ris specin-ren can be seen at the Denver Museum of Nature & Science. CoMN,IENTS: TltisTyrannos(turus rex has the clistinction of being the onlv dinosaur discovered bv a dog (K. Johnson, personal communicatiorr

2005). It is also the onh'T rex found to date in Colorado (although teeth ivere previouslr,knor','n) and the onlv T rex with a street adclress (K. Carpenter, personal communication 2005). DN4NH 2827 r,ias scattereci before burial and li,as also danaged b;'earth-moving equipment before discoven, (Carper-rter and Young 2002).

Bowman DIScovERED: November I992, Dean Pearson, amateur. LocArIoN: Near Rhanle, Bon'man Courltv, ND (Fig. I.1, site lB). FoRMATIoN: Hell Creek Formation, JZ n-r belorv the K:l'boundary (Dean Pearson, notes r,r,itl-r specin-ren). E xCAVAT E D : Pioneer Tra il s Regional \,luseu rn, volunteers, 1992-199 4. REPoSIToRY: Pioneer Trails Regional Museurn, Bou'man, ND. SKELETAL RENIAINS: According to Dean Pearson (notes ivith specirnen),

there rvere 45 bones of the skeleton collected. They cor-rsisted of ribs, rertebrae, both pr-rbes, the distal encl of tl-re scapr-rla, and gastralia (Don Wilkening, personal communication 2005).

Neal L. Larson

!

t

'€ l

,:t!,. .#

,d"&

'l,h '

D

.s&"

H

E

Figure 1 .13 DMNH 2827, left scapula and coracord (A), left ilium in medial (B) and lateral (C) views, left femur rn anterior (D) and lateral (E) views; right tibia and astragalus tn anterior view (F); right fibula in lateral (G) and medial (H) vtev'ts.

=:rs of Tyrannosaurus rex

CoNIPLETENESS: Less than '15 bones (because sorrre are gastralia), or less

than

15%

ofa skeleton bv bone count.

ON DISPLAY? No. CoNT]{EN'fs: 'I'he nrtrseum has nei.'er given the specimen a collection or

an acquisition number. 'l'he bones are still in plaster jackets, and thev are also er-rcased in a liard concretion that makes preparatior-r difficult. Becanse of that, it is r-rot knon n when the specimen n,ill be preparecl (Don Wilkenir-rg, personal cominunication 2005).

BHI4IOO (D"ff,r) DISCovERED: The r,'ear 1993, Stan Sacrison, amateur paleontoiogist. LocArIoN: John, Bettr, and Darid Niemi Ranch, near Buffalo, Harding Cotrntl; SD, abor-rt a quarter n-rile from the Stan excavation site (Fig. I, site l9). F oRtIArIoN: I'lell Creek Forrration, estirrated to be about l6 rr beneath Figure 1 14. Duffy, BHI 41 00, dudng excavation. Pn^f^

nt/ Fd t-arvan

the KIT boundarr' (Johnson 1996). EXCA\ArED: Black Hills Instittrte field crerv, suinmers of 1991, 1994, 1996. and 2006.

Neal L. Larson

REpoSIroRy: Black Hills Institr:te of Geological Research, Hill Cit\', SD. DESCRIBED: Partiallt,described by Counter (1996), Larsor-r ancl Donnan (2002) sKELETAL REMAINS: Most of the skull and a portion of the skeleton n'as

recovered. The skr-rll consists of: both maxillas, right prerraxilla, nasals, both lacrin.rals, left postorbital, both qriadrates, boih 1ugals, left squamosal, both quadratojugals, left pterygoid, both palatines, left ectopterygoid, right epipterygoid, both dentaries, rigl-rt surangular, rigl-it prearticular, tlie right splenial, right coronoid, a partial braiiicase, and 49 loose, rooted teeth. The skeleton has both scapr,rlae ancl coracoids, I astragaius; the right ischium; 8 caudals; I3 dorsals and cervical vertebrae; 9 dorsal ribs; anC 6 chevrons. About 50 loose

teeth lvere found alor-rg u'ith the specimen. coMPLETENESs: Seventv-six bones, or 25% ofa skeleton by bone cottnt. oN DISpLAy? Yes, some portions are on dispiav at the Black Hills Institute of Geological Research, Hill Citv, SD, and a bronze cast of the left sicle of the skull is on the outside of their building. The skull bones L,,r rost of tlre skeletol rerrrains unnrenared. --^ -.^^--^l drL y'LP4r\u. coMMENrs: Duffv u'as named for atton-rey' Pat Duffi,, n,ho was tl-re defense attornev for BHI in the Sue case (see Larsot-t and Donnar-t 2004). The skull and partial skeleton of Duffy'u'ere disarticulated ar-rd scattered or,'er a large area. This prorrpted Black Hills Institute to use a Bobcat to assist u'itl-r tl-re discoverv of the bones. This grour.rd-penetrating Bobcat r,vas used to scrape thin layers of tl-re qllarry floor arvay'during mr,rltiple passes, u'hich ied to the discover-v of much of the specirnen. The final dir-nensior.rs of tl-re quarrv were approximately 55 feet br'70 feet. The Black Hills Institute originallv excavated durir-ig I99)-1996, then returned in 2006 and remo-,'ed the hills aronnd the specimen. Within 3 dat's, thel'had excavated 3 additional skull bor-res and several other unidentifiable bones.

UWGNI I8I DiscovERED: NIike Pallett, Universitv of Wisconsin geologv student, 1997.

LocArIoN: Near Ekalaka, Carter Countl', N,IT (Fig. Ll, site FoRMATIoN: Hell Creek Formation. EXCAVATED: University of Wisconsin lrield Crerv, 1993.

20).

REPoSIToRY: Unir,ersity of Wisconsir-r, Geologv N{user-rm, N1adison, sKELETAL REMAINS: A partial, fragrnentarv skull u,ith

I

WI.

associated verte-

brae. According to Ricl-rard Slaughter, director of the

UW

N,lluseurn

of

Geology', the follorving skull elernents are represented: left dentart',

right dentarv; right sr-rrangular, splenial, right narilla, left postorbital, right postorbital, right frontal (lvith attacl-recl prefrontal, parietal, and laierosphenoid), right jugal, right quadratojugal. rigl-it quadrate, and, tentativel); partial pterygoid, squamosal, and prearticular (not sided) coMPLETENESS: Tq,entv bones, or 7% of a ske le ton bv bone cottnt. ON DISPLAY? No,

27

Figure

1

CoN,tN{ENrs: "This specin-ren is reallv broken up,

.15. Scotty,

2523.8., during excavation (A); skull on display at the RSM Fossil Research Station (B). RSM

li,ith close to I00 small pieces that har,'e not been identifiecl to elerlient t,et" (R. Slaughter,

\\'ritten cornr.nnnication 2005).

Phafn< rnt trfacrt Rnttal

RSM 2523.8

Sas
(Scotty) DISCo\TERED: The r,ear 1991, Robert Gebhart, schoolteacher.

LocATroN: Near Eastend, southern Saskatchenar-r (Fig. 1.1, site 2l). FoRNIATIoN: Frenchntan Fornation. EXCA\ArED: Ro,val Saskatcher,""an N4useum field crer.v 1994 through 2001. REPoSIToRY: Royal Saskatcltervan N{useunt. SKELETAL REN,TATNS: l-he skull is nearlv complete.

It is n-rissing both palthe splenials, the coronoids, the left angtilar, and about a third of the teetl-r. N'lost of the skull bones are incomplete. The postcranial skeleton is less knori n because nrost of rt is still unprepared. There are more than 40 cervical, dorsal, and caudal (but no sacral) r'ertebrae, 16 dorsal ribs (at least), 1 scapula, I r-nanus phalange, and the right fernur, tibia, and fibula, along rvith both ilia, ischia, and pubes. There is also at least I netatarsal and several pes phalanges (Phil Currie, personal con']munication 2005). coN{pLErENEss: Abor,ri I20 + bones to clate. or at least 40% of a skeletorr bi'bone count. oN DISPLAv? Yes, the skull is on displav and severai portions ofthe skeleton can be seen undergoing preparation at the T. rex Discovery' Centre in Eastend, Saskatcheu,an. Col,IMENTS: This skeleton ri'as discoverecl bv Robert Gebhart as he accon-rpanied Tin'r Tokarvk and John Storer on a field trip for the Ror al Saskatchen'an lu{user:rr. The specimen li'as nicknarned Scottv after a bottle of spirits corrsumed in the field bv the discoverers. Preparation is trnderu'av at the T re.r Discoverv Centre in Eastend, Saskatche'"1'an (ovnned and operatecl bv the Roval Saskatcheu'an atir-res, tl're epiptervgoicls,

28

Neal L. Larson

Nlusetrrn). The skull and skeleton u ere clisarticulated and spread out over a l:rrge area (Clut 2003). Scottr is a large adtltTyrannosaurus re.x skeleton r",ith a femr-rr length of ll90 nrnr (P Cr-rrrie, personal corrrnunication 200i).'l'here are still rears of n'ork ahead to finish

prep:rration because of the hard encasing rock, so eventually more of

thc skeleton mav be discovered.

BHI6219 (007, Double-O-Sewn) DIScovERED: The vear 1994, Bill Garstka, professional collector. LocArIoN: Near \'Iarnrouth, Slope Countv, ND (Fig. 1.1, site 22). FoR\'lA'r'IoN: Heil Cieek Forrnation. EXcA\ArED: Collected bi Warfielcl Fossils field crer,v (led by Rick Heb-

and Bill Garstka) in 1994 and 1995. REposIToRy: The skull bones rvere sold to a private collecior in Nerv York, the foot bones to another collector, and the remaining portions rverc o'entualll,, purchased bv Black Hills Institute in 2005. clor-r

.\CQuISITIoN:'l'hror-rgl-r purchase. sKELETAL RENIAINS:'l'l-ie skull consists of both maxillae, both premaxil1:re, and parts of the dentarr'. Tl-re skeleton consisted of I vertebrae, I dorsal rib, I n'retatarsal, I pes phalange, the distal end of left l-runerus. lud plrts of a tibia and fibula (Rick Hebdon, personal com-

munication 2005). co\lPLllr'ttNEss: 'Iu'elve bones, or 7% of a skeleton bv bone count. ON DISPLAY? No.

co\'INIENTs: According to Rick Hebdon (personal communication 2005), rnost of tiie skeleton rvas fotrnd ileatliered out in an arrolio; the remainir-rg portions uere under a hard sar-rdstone ledge. Tl-re field crew j:rckhaniniered on the sanclstone leclge for 6 r.r'eeks in 1994 and came back ir-r 1995 and clvnal-ritecl the ledge. Not rnuch of the skeleton n.as found, but the hun'iems and a large fragnient of tooth indicate tlrat it is prob,ibl, l robrrst rrrorplrotr pe.

BHt 6249 (Stercn) DISCovuRED: 'f}'re vear I995, Steve Sacrison, an arnateur paleontologist. LocA'rtoN: John, Bettr', and David Niemi Ranch, near Buffalo, Harding

Countr', SD, about a qr-rarter mile south of the Duffi' excavation site

(Fig.

1.1, site

2l).

!'oRNrArroN: Hell Creek Fornation. estimated to be 6 to 10 m beneath the K-T boundarr (P Larson, personal communication 2005). EXcA\A'IED: Black Hills hrstitute field creri sunrrrie r of 1995. REposlroRy: Black Hills h-rstitute of Geoiogical Researcl-r, Hill Cit-v, SD. DESCRIBED: Partialh.'described bv Larson and Donnan (2002). .\ceuISI'f toN: Collectecl bv Black FIills Institute field cren'. sKuLtt'i'Al Ru\{AINS: Skeletal eiernents collected s ith Steven are a nearlv

One

Hu"::'=: ':a.s

ofTyrannosaurus rex

B : g-.e

1 16

egrgrsne/i

.:/

t.

Therapod

iAl found

Sie"/en, BHI 6249, Ph^t^<

cla
(At Ed Gerken.

complete right femr-rr, 6 dorsal r,ertebrae (mosth' incomplete), 5 dor*:L^ I -L^r."---, '-l Jdl I lUJt r yl rclldrr
LDP#977-2 (Pete) DISCovERED: The vear 1995, Rob Patchr,rs, a gradr-rate student fron'r Unir,'ersitv of Neu' Orleans.

LocArIoN: Suanson Ranch, Niobrara Countr,, WY (Fig.

1.1, site 24).

FoR\tA'rIoN: Lance Forrnation, abor-rt 800 feet belorv the KIT contact. EXC.\\'ArED: Lance Dinosaur Project field creil'in the summer of I995. REposIToRy: Stored at the University of Neu' Orleans, Neu, Orleans, LA. DESCRIBED: Derstler and Ml'ers (2005, this','olume). SKELETAL RETIAINS: According to Derstler ancl Mvers (2005), the skeletor-r contains 2 short strings of articulated cervical ar-rd dorsal verte-

Neal L. Larson

brae along with son-re ribs and gastralra tirai are heavilv iveathered. 'fhere are also parts or fragments oi the hrnd lirnbs, pelr,is, ribs, ar-rd vertebrae rveathered dor'vnslope from the specinen.

coMpLErENEss: Estimated to be bet$'een lt)l to Ii% of a skeleton bv bone cour-rt. ON DISPLAY? No. CoN,tN'IENrs: Pete was narned in honor of Rob s grandfather, Pete Patcl-ius, and for Pete Larsor-r. Pete is ur-rdergoing preparation at UNO but is not yet on pr-rblic displav. Hurricane Katrina (.\ugrist 2005) interrupted the rvork b1' putting the specimen off limits for more than 9 nlonths. As a result, neither the records r-ror the specinen cor-rld be worked on, investigated, or in'"'entoried (Derstler, personal communication 2005).

Barnum DISCovERED: The year 1995, Bruce Hamilton and Leon Theisen, profes-

sional collectors. Sever-r Mile Creek, north of the Cheyenne River, Niobrara Count,v, WY (Fig. l.l, site 25). FoRN.{ATIoN: Lance Formation. EXCAVATED: Collected b1'Japh Bol'ce and R I B Rockshop field crew in 1995 and 1996. REPosITORY: Siatus unknolvn. wEB sIrE : http://rvu'w.factmonster.com/spot/dino-bargaintrex.html. ACeuISITIoN: Undisclosed inr''estors pr-rrchased Barnum at a Bonhams and Butterfields auction in Mav 2004. sKELETAL RE\,IAINS: The skull consists of incomplete bones, includir-rg both n-raxillae, left jugal, left ectopten'goid, riglit squan-rosal, left der-rtari', surangular, ar-rd articuiar. Tl-re skeleton aiso has mostly incomplete bones consisting of I cervical, 4 dorsal, and J car-rdal verte-

LocArIoN: Near the headwaters of

brae; 9 dorsal ribs, sorne gastralia; 6 metatarsals, 3 pes phalanges; left iliurn, left ischium, both pubes (right incomplete), both femora (right incomplete), left tibia, fibula, astragaius, and calcaneum; par-

tial left scapula, left hurnerris, and nanus clarv. CoNIPLETENESS: Forty-seven bones, or 16%

ofa skeleton by bone count.

ON DISPLAY? No.

coMN,IENrs: Accordir-rg to Japh Boi'ce (personal commur-rication 2005), he named the skeleton in honor of Barnr-rm Brown, 'nl,ho had discor. ered the first T1'rannos durus rex bor-res (described as Dynamosdurus imperiosr-ts Osborn 1905) not far from this site. Bo,vce originally

claimed that this specimen was the rest of the holotvpe skeleton (BN{NH R7994, formerlr" AMNH 5866; see above), br-rt according to Carpenter (personal communication 2006), if that r"'ere true, there u'or-rld be I femurs for the type instead of ? According to faph Boyce, he sold the specimen to a group of investors knor,vn as Tyrex in 2000. Soon alter tfiis, 'l\'rex brought a case against Bovce, claiming lack of clear title. -\fier Boyce demonstrated a clear title, the specin'ren $'as auctrnned off for $90,000 bv

5t

d;,# !6'

"'.r.*fr'"

3, b:

-'.1 ,p,

gure 1.17. Fox, BHI R) lPft dcnfarv st ihe excavation, with fe<ar Tmith Phnfn

Bonhams and Btrtterfields, ;rn allction house, in N{:rr' 2004 to unknou'n in'u'estors (fapii Bovce, personal comrnunication 2005).

F

/11

bt

Ed Gerken.

BHI4I82 (Fox; Foxy Lady; County rex) DISCoVERED:

'fhe vear

1994, t,lor.d Fox, rancher.

LocArIoN: Land belor-rging to Hardir.rg Cor-rntr', located u,ithin the pasture of Llovd, Eunice, and Russeil Fox, near Redig, Short Pine Hills, Hardir-rg Countr', SD (Fig. Ll, site 26) FoR\,IA'f IoN: Hell Creek Formation. EXCA\ArED: Black Hills h-rstitute field creu', slulrrers of 1996, 1997, and 199E.

DESCRIBED: Partiallr, described b1' Larson and Donnan (2002).

REposIroRy: Black l-lills Institute of Ceological Researcl'r, Hill Citv, SD. sKELET'AL RENTATNS: The skull consists of the left postorbital, right qua-

right ectopterl.'goid, both dentaries, both surangulars, both articulars, both prearticulars, both angulars, both splenials, both coronoids, and 43 ioose, rootecl teeth. The postcranial skeleton u':rs for.rnd u.ith 2 cervical, I clorsal, ar-rcl J caudal vertebrae, 5 dorsal clrato ju ga1.

ribs. ancl 2 cervical ribs.

co\tPLLI E\Ess: 'lb

o\

clate, 29 bones, or I0% of a skeleton bv bone count. DISeLAI? Yes, the left dentan' is on displal'at the Black Hills N{u-

seLrnr of Natural Histori,, Flill Cit\', SD. Cou\tE\TS: Llovd For discol'ered aTl,rannosaurus rex,later namecl Fox, in hor-ror of Llovcl, in 1994 on a parccl of Harding Conntr'l;rnd. Black

Hills Institute of Ceological Research received permission fron'r the Neal L. Larson

corlntv commissioners to begin ercalatror in 1996 T'he specir.nen was u,iclelv scattereci; n-rore probabh'renrain. buriccl at the site. Portions

of

the skull and skeleton indicate that it i: a robLrst n-rorphot-vpe.

MOR

9BO

(Peck's Rex) DISCoVERhtD: 'l-he vear 1997, Lou Tren.rblar, bioiogr teacher.

LocA'l'IoN: \'lcCor-re Cour-ttl, N{T (fig. FoR\IATIoN: l{ell Creek Formation.

Ll.

site l7).

Collectcd frorn 1997 through 2004 by'several clifferent grollps, including different parties led br J. Keith Rigbv, Nate N'lurphr', and Kraig Derstier (see Derstler and M\,ers this r,olurne). REPosI'roRY: \{use um of the Rockies, Bozeman, N'IT, on loan to the F-ort Peck Paleontologl'Field Station at Fbrt Peck, N{ontana. DESCRIBED: Furcula br,'Larson and Rigby'(2005); Lipkin ancl Carpenter this r,olurne. sKEL!tlAL RhtN{AINS: The skull consists of a braincase, both maxillae ancl prenasillae, incorrplete nasals (most of the right), right postorbital, right 1ugal, both lacrin-rals, both quadrates, both quadratolugals, both cler-rtaries, left splenial, left prearticular, right surangular, and the right artictrlar. The forelirrbs include the furcula, both scaprilas, I coracoid, both hunreri, met:rcarpal III, ar-rcl 3 rnanus phalanges. Its hind lirnbs ar-rd peli.'is include a complete right ieg u,ith calcaneurn, astragaltts, ar-rd I mctatarsal; a complete left iliurn, partial right iliurn, both pubes, both ischia. and the sacral vertebrae. 'l'he skeleton also has sotne dorsal and cen'ical r,'ertebrae, a string of 9 or I0 anterior caudal ."'ertebrae (n-rost lvith chevrons), manv dorsal ribs, some cer','ical ribs, and quite a felr, gastralia (N. N{urphr', personal comrrunication 2005). coN{PLETENEss: Thcre }ras not vet been a corrplete skeletal inventorr'. It is estimatecl to be about lZ0 bones, or 40% con-rplete b.,'bone count. oN DISeLAv? Cast of the skeleton is on clisplay at Fbrt Peck h-ite rpretive Center. Fort Peck. EXC.A.vA'I't1D:

Figure 1.18. Peck's Rex,

MOR 980, cast of skeleton at the Fort Peck lnfprnrpfi\/a apnfar ( A t

cast of skull (B). Photos a6t !rfa
33

CoN{}lENTS: Peck's Rex u'as another Tyrannosaurus rex involved in contror,'ersr,. T'he property'rvas originalll' private, but the federal government foreclosed the land because of an unpaid loan. A California teacher discor.'ered theT. rex n'l-rile exploring for fossils as an Earth

Watch volunteer, under the supervision of J. Keith Rigbi', r,l'ho began the ercavatior-r. After the Earth W'atch gror-rp closed the quarrl,', later that vear, the originai landowners returned and tried to excavate the dinosaur thernselves. The governmcnt seized the specimen, and eventuallv the specinen rvas pr-rt under the care of ttre Museum of

thc Rockies (http://rvrvu'.r-rd.edu/-ndrr-ia

gl

ail}}T l igbvrex.htrrl).

The specimen received its nicknarne after nearbv Fort Peck Lake. 'fhe excavation of this specimen il'as unusual because several different groups particip:rtecl. J. Keith Rigbl'of Notre Dame Universihi along n itl-r Earth Watch volunteers, the original landorvners, Nate Murphv from the Judiih River Dinosaur Institute, and Kraig Derstler frorn the Universit)'of Ner.v Orlearrs n'ere all involvecl ivith the reco."'erv of the skeletor-r. For ftrrther discussion, see Derstler and N,ll'ers (this volurne).

Tinker DISCovERED: The .,'ear 1997, N{ark Eatman, professior-ral collector.

LocA'rIoN: Harding Countl,Land, SD (fig. 1.1, site 28). t'oR\{ArIoN: Hell Creek Formation. EXCA\ArED: Mark Eatrnan in 1997. and N,like Farrell in I99B (Glut 2002). REPOSITORY:

None, as ofvet.

DEScRIBED: Partiallv described

in Glut

(2002).

to Barrr.' James (personal conmunication 2005), the specirnen has rnost of a skull (aithough some bones are onll,pieces and fragnents) consisting of the both pren-raxillae, left maxillae, both quadratojugals, right palatine, left jugal, cluadrate, squamosal, pterygoid, a parietal, :rnd part of I nasal. The lowers consist of left dentar_v, both articulars, both coronoicls, right suranglrlar. the left prerrrticular. anqtrlar. arrci splenirl. The skeletori is made up of 20 partial caudal ."'ertebrae and 12 chevrons; 5 dorsal and 2 cervical ribs and nllrrerous rib fragn'rents; both pubes, both ilia (incompiete), and the left ischia; parts of both scapula, the right coracoid, both hurneri (left complete); and a r-nanus ancl a pes claw. CoNlPLETENEss: Sever-rty-three bones, or 24% of a skeleton bv bone SKELET'AL REN,IAINS: Accordir-rg

cotiltt. ON DISPLAY? No.

coN'rMENrs: Because of the status of thc land, its ownership has beer-r tied up in litigation for several years. Bakker (personal coinmunication 2002) has vieu,'ed this specimen, and is certain that it is a jur.'e-

nile T rer. He is also convinced that this specimen offers imporiant information on growtl-r rates for T. rex and will finallv settle the differerrce s bett'een juven ile Ty rannos aur us and Ndnot.I, rdnnLLS. .\ccording to B. Jarnes (personal corrrrunication 2005), the Neal L. Larson

specimen $,as found u'ith a right n-rarilla and jugal from a iarger individual, along u'ith a dentar'r'from another theropod. He believes that there are perhaps 3 different indir idual T rer specirnens from the site. The specirnen rvas heavih'rieatfrered and broken. The initial collecting rvas done without glr:e or plaster, so manv of the bones u'ere fragmented. In addition toT. rex bones, there were also a number of Edrnontosaurus skeletal elements, plants, rnolluscs, and crocodile teeth four-rd w'ith the specimen (Glut 2002).

Ollie (Rex A) DISCovERED: October 1998 by Craig Pfister, a professional collector. LocAT'IoN: Southeast of Ekalaka Carter County; MT (Fig. 1.1, site 29).

!'oRMATIoN: Hell Creek Formation. EXCAVATED: Craig Pfister, 1998 and 1999. REPoslroRy: Currentlr, housed at Great Plains Paleontologl,, Madison, Wiscor-rsir-r.

sKELE'l'AL RE\'rArNS: The skull consists of the left maxilla, both premax-

illae, both postorbitals, both quadrates, left jugal, both ptervgoids, arrd a partial braincase. The skeletorr consi:ts of both fernora, both tibia, both fibula, both astragali ancl calcanea,2 metatarsals, several

I ischia, the left pubis, right iliurn, right scapuia, both humeri, right radius, right ulna, sel,eral cerr,ical vertebrae, r-nuitiple dorsal and caudal vertebrae, manl'cerl,ical and dorsal ribs, and se'". eral chevrons (Craig Pfister lvritten colnmunication 2005). coN,rpLErENESS: A total of l2,f bones, or 4I% of a skeleton to date (Crarg phalanges,

Pfister, rvritten con-imunication 2005). oN uSPllY? No. co\'I\,IENTS: 'l'he site rreasllres 20 m b1' 17 rr . \,lanl'of the bones shor,r, evider-ice of scar,enging (Craig Pfister, n'ritten commnnication 2005).

Rex B (Tricerato

p s- AIIey

T. rcx)

DISCovERED: 'l'he r,ear I998 bv

Bill Allel; rancher and amateur collector. LocArIoN: Northeast of Isabel, Corson Countv, SD (Fig. 1.1, site 30). FORNIATIoN: Hell Creek Formatior-i. EXCAVAT'uD: Bill Allei,, l99B through 2000. REposIroRy: Cr,rrrentlr'l-ror-rsed at Black Hills Institr-rte of Geological Research, Hill Citr.,, SD, for cleaning, restoration, ancl casting. sKEt,ErAL REN{AiNS: The skull consists of the left marilla, left premaxilla, left qrradrate. left qrradratolrrgal. botlr lrcrirrrl'. rraials. left ectoptengoid, and a braincase u'ith disarticulated, nonfused frontals. The skeleton consists of onh,the right scapula, right coracoid, ancl I rib. There are also numeroLrs fragmented bones w,ith this speciuren, and ser,eral

other r:nprepared skull bones n'hose identification cannot

_vet

be made.

ffiWw **ry A Figure 1.19. Rex Q maxilla and premaxilla

(A), pes phalanges

(B).

B CoNIPLETENEss: 'llventv-four bones, or 8% ol a skeleton to date.

oN orspr,ey? No. coNINIErirs: This specinrcn is of the gracile fornr trearir, as large as Stan. 'Ihe bones lvere scatterecl, ri'ith preservation ranging from good to poor. This is one of tire most eastern T rex specimens, at 101.5'n'est longitr-rcle.

Rex C

'l'he vear 1999 bv Bill Aller; rancher :rncl arnatertr collector. LOCATIoN: Northeast of Isabel, Corson Countr', SD (Fig. 1.1, site 3l). F oRNIATION: Flell Creek Forn-ration. r.xcA\ArED: Bill Allev, 1999. DisCovERI.tD:

REPOSITORY: NoT]e.

sKELETAL REliAINS: The skrill consists of the right maxilia, right pre-

rnaxilla, right sr:rangr-rlar, right articular ancl the right spler-iial. 'l'he skeleton cor-rsists of the right (?) tibia ancl astragalLrs (calcaneurr ?), both fibula, 3 pes phalanges, right ischia, I cerr.ical r.ertebrae, 1 dorsal ','ertebrae,2 caudal r,ertebrae, I chcvron, and ser,eral boxes of uniclentified parts. Co\IPLETENEss: Eighteen bones, or 6% ol a skeleton to date. oN orsplev? No. Co\i\triNTS: 'l'he rnaxilla and pes phalanges of this TlrannosduruE rex are quite large, sinrilar in size to Sue. Bone preseri'ation is excellent. One of t1're pes phalanges has sorre severe pathologies, perhaps frorr a healecl break. 101.

2000-2005

'fhis

is anotl.rer easternnrost

T

rex snecirren et

5' u,cst longitudc.

Tlre ercar,ations of Tyrannosaurus rex contrnuecl into the 2lst centurr'. Althotrgir sorne of these discoveries n'ere nrade in the 1990s, there u,ere qtrite a rrr-rrnber of'1. rex ske]etons found since 2000. There ]rar.e been ser. eral teievision specials about some of these discol'eries, such as Discoverl' Clrarrnel's \lallet of the T rer, n'hich highliglit rnanv of tl-re r-rei,"'discoveries r-r.racle br the Nluseum of the Rockies near Hell Creek, south of Fort Peck Lake, N.lT.

Neal L. Larson

BHI6248 (E. D. Cope) DISCovERED: The vear 1999, Bucky Derflinger, rancher, amateur fossil

collector.

LocArIoN: Wade Derllinger Ranch, near Usta,

Perkir-rs Courlty, SD (Fig. siie 32). IToRMATIoN: Lower portion of the Hell Creek Forrnation. EXCAVAI'ED: Black Hills Institute field crew sunmer of 2000. REPoslroRy: currentlv stored at Black Hiils Institute of Geological Re1.1,

search,

Hill City, SD.

DESCRIBED: Partial description by Larson and Donnan (2002). SKELETAI. REI,{ArNS: To date, E. D. Cope consists of a naxilla, dentarl,

ectopterl'goid, angular, other ur-rdetermined skull bones, some vertebrae, ribs, and concretion-encased bones. other tha' the left max-

illa, the preparaiion of the specimer-r has not t,et begr-rn. CoN{PLEI'ENEss: About l0% ofskeleton bv bone count. oN DISILAv? The left maxilla is on displav at the Black Hills Museun of

Natural History', HillCitv, SD. Di-rring the excavation, a nunrber cf centra rvere discovered piled on the surface. It appeared that some time ago, someone had intentionall,v piled these bones up. Larson ancl Donnan (2002) speculated that tl-ris could possibly be the site irom ri hich Edward Drinker Cope had collected 2 vertebrae ironr a partial Tyrannosaurur; rex l-re described as LLanospondylus gisa,. L-nfbrir,rnatelv, this

CoMN,IENTS:

One

Hu-:'::

/:ars ofTyrannosaurus rex

Figure 1 .20. E. D. Cope, BHI 6248, excavation site Photo by Dan Counter.

question remains unsolr,'ed. Cherrical analy,sis might ansil'er the questton.

This specir.nen n'as scattered over a large area like Duffi', Stevcn, ancl Fox. And like Stel'en, it appears that it u'as also cannibalizecl (Larson and Donnan 2002). N'Iost of the skeletal elernents are encased in sideritic and phosphatic concretions, rnaking it difficult to prepare and recognize thc bone clements. N4ore of the skelctor-r could be buriecl at the sitc.

Monty DIScovERED: Tiie vear 1999, anonynrous lanclow'ner. LocA'1'IoN: Northern Niobrara Cor-rntr,, \\'Y (Fig. 1.1, site 33). FORN'IATION: Lance Forrl]auorr. EXCA\ArED: Collected bv Craig Sundell, Fred Nuss, and crew in 2000.

REposIroRy: Babiarz hrstitute of Paleontological Studies (BIOPSI), N4esa.

AZ.

SKELETAL REN{AINS: Babiarz (personal cornrnunication 2005) reports

that tlie skull consists of a braincase; nasals; the right rnaxilla, lacrirnal, postorbital, quaclratolugal, and the squamosal; both quadrates, both ptervgoicls; the left premaxilla, jugal, ancl surar-rguiar. T'he skeleton consists of4 cervicals, 2 clorsals, J cauclals, l2 dorsal ribs,4 gastralia. I pubis, a partial ilium, I pes phalange, an ulna(?), and serr eral bones sti1l in jackets.

coN{pLErENEss: Fiftr-three bones, or 18% (to date) ofa skeleton br,bone colrnt. oN DrspLAy? Ye s. uarts at Arizona State LJnir,'ersitv. F gure 1.21 . Monty, right maxilla dur-

ing excavation. Photo by Craig Sundell.

Neal L. Larson

coNIN{ENTS: The specinten u'as nanted after the landou'ner's first nante

Montv. It

l-ras a

fairli'good braincase frorn uhich an endocast

is

being produced.

Figure 1 .22. B-rex, MOR 1125, cast of skull on display at the Museum

of the Rockies. Photo by Peter Larson.

MOR r125 (Bob; B-rex) DISCovERED: The r,ear 2000 bv Bob Harrnon, a professional preparator

for tl-re \luseum of tl-re Rockies. LocA'rIoN: Near the Fort Peck Lake, Charles \1. Russell National Wildlife Refuge, Garfield Countv, N,IT (Fig. I.1, site 34). FoRNIATtoN: l,oner half of the Hell Creek F'orrnation. EXCA\ATED: Bob Harmon, Nels Peterson, and 2r \luseurn of the Rockies field crcri, 2001-2003. REPoSIToRY: \lluseum of the Rockies, Bozenran. \l'l'. DUscRIBED: L)escription of dinosaur skin tissuc tront the femur in Schn'er-

One

Hu.:':: tars of Tyrannosaurus

rex

tzer et al. (2004) and in the rnedullarv bone fron-r the same femur bv Schrieitzer et al. (2005). See also Schn'eitzer et al. (this volurne). SKELEIAL RENIAINS: 'fhe skeleton has a fairly complete vet disarticulated skull that is rnissing both premaxilla ar-rd a dentary, ph-rs a few other skull bones.'l'here are J cerr,'ical,4 dorsal, 5 sacral, and 12 caudal vertebrae, along ivith 7 chevrons,4 cervical, I3 dorsal ribs, left scapula and coracoicl, the furcula, left ulna, both femora, tibiae, and fioulae, right calcanelrm and astragalus, and ll pes phalanges (P. Larson, personal communication 2005). coMpLETENESS: A total of I I I bones, or f7% of a skeletor-r by bone

count. oN DISPLAv? Yes, the furcula, ulna, a portion of the femur (showing the structure lvithin the bone) ar-rd a cast of the skull are on dispiay at the Museurn of the Rockies, Nlontana State University, Bozeman, MT. coN,IN.{ENrs: This specinien has rnade headlines u,ith the discovery of medullary bone in the right fen'rur inclicating that it r,vas an egg-producing female (see Schlr'eitzer et al. 2005, this volume), provir-rg that ,vou can sex a rex, or at least some of them. It has also been referred to as Bob, after the discoverer, Bob Harmon, before it il'as determined to be female. It is of the robust morphotvpe.

MOR I126 (C-rex\ DISCovERHD: The year 2000, Celeste Horner.

LocArIoN: South of the

F-ort Peck Lake, Carfield Countl', site 35). FoRMATIoN: Lo'nver half of the Hell Creek Formation.

MT (Fig. i.l,

Bob Harmon, Ioe Coolie, and a N{useum of tl-re Rockies field creu'. 2000-2001. REposIToRy: Museum of the Rockies, Bozen-ran, N{T. EXCAVATED:

SKELEIAL RENIAiNS: The skeleton consists of a left prearticuiar and surangular, 20 dorsal ribs of varving completer-ress, 3 partial dorsal lertebrae, and a chevron (P. Larson, personal comrrunication 2005). CoN,IPLETENESS:

Til'enty-six bones, or 9% of a skeleton bv bone count.

ON DISPLAY? No.

coMN{ENTS: C-rex was named in honor of Celeste Horrrer. after the first letter in her name. Beginning in 2001, the Museum of the Rockies began naming (or referring to) each of their different Trrannosaurus rer specirnens after the first letter of the first name of its discor,erer.

Although most of tl-rese T rex specin-rens are rnade up of onll' a bone or two, some (such as B-rex, C-rex, complete.

Neal

L

Larson

ar-rd

G-rex) are rruch more

UCRC PVI

Figure

PV1, as

DISCovERED: The vear 1950 (or earlier), Zerbst famil,v (Arlene Zerbst,

left arm, hand scapula, coracoid, and furcula u ndergoi ng p repa rati on

on Schneider Creek, a branch of the Chevenne River, Niobrara Countl,', WY (Fig.

F

hor,rse

(B). Photos:

bi'a field crew'led bv Paul Sereno, Ur-iiversitl,of Chicago, students, and Project Exploration 200i. REPosIroRy: Universitv of Chicago Research Collection, University of Chicago, Chicago,lL. DESCRIBED: Furcula ar-rcl pectoral girdie bv Lipkin and Sereno (2004). EXCA\ArF;D: Collected

SKELETAL REN{AINS: Par-rl Sereno (r.vritten communication) relaies tl-rat "tl-re skeleton preserves a cornplete, articulated and in-the-ror,rnd

torso including botl-r pectoral girdles and forelimbs (including the frrrctrla). gastral basket, ribcage, and the cervical-dorsal colurnn.

Onll'fragments of the hindlimbs, folded urrder the torso, remain. A bodl'outline can be seen in cross-section, rviih the inside of the torso fillecl il'ith finer-grained siltstone than the outside (mediun-r-tocourse sandstone)." CoNlPI,ErENEss: Estimated 60 bones. or 20% of a skeleton bv bone

count. ON DISPLAY? No.

coMN,tENrs: Originalh published as UCPC Vl. l'he body portior-r of ar-r articulated T\.rannosaurus rex skeieton ri as knorvi.r for man,v 1'ears before an','one identified that it was anr thing rrore than just another duckbill skeleton. It lav or-i a parcel of BL\ I land n'ithin the pasture of Leor-rard Zerbst, ar-rd often became the stop tbr geological field trips to r ierr r dinosrrrrr irr the rotrgh.

rex

(A)Wendy

Taylor; (B) Paul Sereno.

1.1, site 36). oRN{ATIoN: Lance Formation.

/ears offyrannosaurus

.23. UCRC

found in large,

weathered blocks (A);

personal communication 2005), but not identified as aTyrannosaurus Tex skeleton until 1997 bv Craig Derstler (P Larson, personai

comrnnnication 2005). LocArIoN: A feu' kilorneters south of tl-re Zerbst ranch

'l

41

Figure 1 .24. UMNH 110000, left dentary on display at the New Mexico Museum of Natural History.

Accorcling to Parrl Sereno (u,ritter-r conrrnunication), "the speci-

rren lar,on its side in a large, extremelv hard, sideritic, sandstone concretiorr. The earliest photo (in a 1952 rancl-rer's gazette) shou,s a complete concrction set atop a footing of sotter siltstone. The specinren \\'as thought to be a duckbill tts F)dn'Lontosaunrs is comnron irr the area. Since that time, the concretion broke into about 5 pieces, the largest containing thc intact torso. "There is no evicier-rce that the skull il,as el,er prescnt, as traces should have been found in the flat terrain surror-rnding the concretion. A 20cm-diameter trce trunk and erodecl hadrosaur bones are preser."'ed loclged against the torso; the inclir,idual appears to have fallen suclclenlv inio a channel. With partial preparation, it u.:rs possible to identifr,the specirnert asTyranrLosdlLrLts rex, an indir,.idual approximatelt'66% the size of 'Sue,'FMNH PR2081."

UMNH

lIOOOO

DISCOvIIRED: The r,ear 2001 bv Rose Difler' (student) and

Quintin

Saha-

ratian (technician) frorn the Unii.,ersiti'of tJiah (San.rpson and

Loeuen 2005). LOCA I

IoN: Near Price, Carbon C)ountr,, UT in the

\{anti La-Sal Na-

tional Forcst (Fig. l.l, site 37). FOR\tA1'to\: North Hon'r Formation.

t.\c.\\Ar ro: Collected bv the

Utal-r Nluseum of Natural Historr, fielcl cres.1001. REposrroRr: Utal-r lluseurn of Natural Historv; Salt Lake Cit)', UT. DESCRIBED: Sarnpson and Loen,en (2005).

Neal L. Larson

SKELETAL REMATNS: The skull is ven'ir-rconrplete, consisting of a right

postorbital and squamosal. The skeleton consists of 2 cer','ical 3 sacral and a series of 6 n-ridcaudal vertebrae, along ri ith 6 chevrons and a rib. Pelvic girclle elernents inch-rde: the left pubis and iscl-rium and the distal blade of the right iliurn. There is a partialleg consisiing of the left

tibia, fibula, and the astragalus (San-rpson and Loer,ven 2005). CoMPLETENEss: Trr,'entv-six bones, or about 9% of a skeleton, by bone

couilt. oN DrspLAy? Yes, at the Utah Museurr of Natural Historl,', Salt Lake

City, U'll coMN,IENrs: This discover-v ertended the known geographic range of ?1'ranno:iaurus rex n'estrvard into central Utah. This indicates thatT. rex spannecl "habitats from wet lowland coastal plain environments to

cooler alluvial plain settings and semi-arid, upland intermontar-re basins" (San-rpson and Loelven 2005). Because Alamosaurus has been for-rrd in the same formation, Sarnpson and Loewen (2005) sr-rggested tl-rat perl-raps T. rex rtay have exploited this potential food source.

TCM 2001.90.1 (Bucky; formerly BHI 4960) DISCovERED: The year I998, Buckv Derflinger, rancher, arnateur fossil

collector.

LocArIoN: \\'ade Derflir-rger Ranch, originai Usta towrr site, Perkins Countr', SD (F'ig. l.l, site 38). FoRMATIoN: Hell Creek Formation. not far above the contact of the Fox

Hills Formation. Black Hills Institr-rte field crew, sllmrner of 2001 and 2002.

EXCAVATED:

REPosIToRY: The Chiidren's N4user-rm, Indianapolis, IN.

Lipkin and Carpenter (tl-ris r,olurne); partial description of excavation and eiements

DESCRIBED: Furcula by Larson and Rigby (2005) and

by Clr,rt (2006). ACQUISITIoN: Purchased fron-r tl-re Black Hills Institute of Ceological Research. 2001.

One HundreC Years ofTyrannosaurus rex

Figure

1

.25. Bucky,

TCM 2001.90.1, por-

tion of the large Bucky excavation (A), skeleton as mounted (B).

43

SKELETAL RE\'{AINS: There n'ere r-ro skull elerner-rts or rrajor leg bones

found n'ith the skeleton.'fhe skeletor-r consists of 8 cen'ical,9 dorsal, i sacral, ancl 15 car-rdal vertebrae; 14 chevrons; Il cen,ical ribs; l6 dorsal ribs; 24 gastralia; a cornplete 1,et pathological fr-rrcula; botlr scapulas, right coracoid, left ulna, 2 manus pl-ralanges; boih iiia, 1 ischia, 4 rretatarsals, and 9 pes phalanges. coN.rpLErENESS: A totai of I0l bones, or 74% of a skeletor-r bv bone count. oN DISpLAy? Yes, the original Bucki'skeleton is mounted, along u'ith a cast of St:rn, as ifattacking aTriceratops skeleton (Kelsev). CoNiNtFlNl's: Bucki Derflinger discovered a pes phalange frort this fi'rrznnosaurus rer ri'hile he u'as breaking in a vonlrg horse on his father's ranch about B miles east of the original Sr-re dig site. 'firis could be consiclereci the first cliscor,erv of aT. rex bv a horse. Thc specimen nas named Buckl' in honor of its discoverer, btrt as fate wor-rlcl har.'e it, this is a robust morphotvpe and therefore most likelr'female. Tl're carcass origir-rallv lav or-i the ground, decomposing, and becanre clisarticulated. Soon after, it n'as transported br,u,ater anci cleposited in a lori', shallo*'rallei'.'l'he size of the ercavation is cnormous, about I50 feetbv 30 feet, and u,ith l2 to 30 feet of or,'erburden. The skeleton n'as discor,'ered along lr,ith numerous bones frorn an F)dmontosaurrrs (u'itl-r bite marks in the sacmm), ser,'eral Tricera/ops bones, turtle elenents, a cli.,'erse Late Cretaceous fauna of fish, reptiles, mamrrals, dinosar-rrs, and plants.

MOR ll28 (G-rex) DISCovERED: 'l'he r"ear 2001, Creg

\\'ilson, then a studeni at LJr-riversitr,' of California, Berkeler,. LocArIoN: Near the Fort Peck Lake, Garfield Countl', NIT (fig. 1.1, site l9). FOR\'IA'l IoN: Hell Creek Fon-nation.

EXCA\ArED: Nels Petersor-r ancl the Nlluseum of the Rockies fielcl crerq 2001. REPoSIToRY: N{user-rm of the Rockies, Bozernan, N'lT. SKELETAL RE\IAINS: The skeleton consists of an incontplete dentarr,, 7 robust ribs, 4 dorsal and I cauclal vertebrae, 3 chel'rons, a partial scapula, both ischia, both pubes, the left fenur, and left tibia (P

Larson, personal corrmLrnication 2005). CoN{PLETENEss: 'liventy-three bones, or 8% of a skeleton bv bone count. oN DISPLAY? A single tooth fron'r the specimen is all that is currentlv or. displav (Bob Ham-rorr, pcrsonal communication 2005).

N{OR

lli2

(F-rex) DISCo\TERED:'l'he vear 2001 bl, Frank Stewart. LocA'rIoN: Near the Fort Peck Lake, Garfield Count'u', \.,'IT (Fig. 1.1, siie 40).

44

Neal L. Larson

FoRriArIoN: [,ou'er half of tl're Hel] Creek Fornration. EXCA\.A'I'ED:

N{useurr of the Rockies fielcl crcu.1001.

RIIPoSI'l'oRY: N4nseunr of the Rockies. Bozeilan.

\l'll

SKFILEI'AL REN{AINS: The skeleton consists of a leg. pelvis, posterior ribs, sorne posterior dorsal l'ertebrae (all hear

ilr rieathered), a metatarsal, vertebrae, 4 7 caudal and cher.'rons. CONTPLETENESS: A total of 25(?) bones, or Et?)% ol a skeleton br bor-re couDt. ON DISPI,AYT NO,

coN,INIENrs: The legs, pelvis, ancl ribs are heavilv rveathered and fragmentecl.

Otto DISCo\TERED: The vear 2001 b1'Craig Pfister, a professional collector.

LocArIoN: Ncar Ekalaka, Carter County, MT (fig. l'oRNIA'rtoN: Hell Creek F-ormation.

1.1, site 41).

EXCA\ArED: T'he 1'ears 2001 and 2002 bv Craig Pfister. REposIroRy: Currentlv housed at Great Plains Paleor-rtologi.', Madison,

wt. SKELETAL RE\'IAINS: According to Craig Pfister, the skeleton consists

of

both femora, both tibia, 2 netatarsals, 1 fibr-rla, rr-rultiple cervical and dorsal ribs, and multiple caudal vertebrae. coNIPLl,t:f I.tNIiss: 'f hirtl.tn,o bones, or I0% of a skeleton bv bone count ON DISPI,AY? NO.

Thc sitc llas a point bar deposit and measured 40 m bl' 32 rn ancl 15 nr decp (Craig Pfister, u'ritten connnnication 2005).

CO\,INIENTS:

N{OR/USNM (N-rex) DISCovERED: The vear 2001, Nathan Nlvhrvold, computer businessman,

enthusiastic amatenr, Hell Creek Project undern'riter. LocA'I'IoN: South of Fort Peck Lake, Charles \'1. Russell National Wildlife Refuge, Carfield Countr', N{T' (F-ig. 1.1, site 42). FoRNIATION: Hell Creek Forrnation. EXCA\ATED: N,Iichael Brett-Surrnan and a Smithsoiiian Institr-rtion field creri', 2002, 2003. RFtPoS

IToRY: Accorcling to N,{ichael Brett-Surman (personal comrnunica-

tion 2005), the specirnen is currently still held bi'the N,luseurn of the Rockies, but it is in the process of being transferred to the National N{useurr of Natural Historl', Sn'ritl-isor-rian h-rstitution, Washingtor-r, DC. sKELEI'AL RE\lAINS: The skeleton consists of iin irrconrplete dentary, an angular, I cervical 'u'ertebrae, 2 ceri,ical ribs. I clorsal spirres, 2 dorsal ribs, J caudal r'ertebrae, 3 chel'rons, an iliurr tneathered), ischium, pubis, right leg, and articulatecl foot (nearh cornplete). Co\rPLE-i'ENEss: About 40 bones, or l3% of a skeleton bl bone cor-rnt.

Figure 1.26. Wyre4 BHI 6230, excavation (A)' skin impression (B); left tot pol)

ot tu

tt

lcLQlQl-

cals /C), right pes (D)

oN orspr,,q,y? No.

coNIt{ENrs: T'his

skeletor-r u,as named for first initial of the discor,'erer's name. Nathan Mvhn'old n'as n'orking as a volunteer lvitli the Museum of the Rockies in 2001 u'hen he four-rd the skeleton. 'fhe Smithsonian Institr-rte, rvhich has only a cast of Stan or-r displar', has been trving to obtain an origir-ral skeleton and is ii'orking on acquiring this specirren from tl-re Museum of the Rockies; thus, at this tirre, it has no catalog nnmber.

BHI6230 (Wyrex) DISCo\TERED: T'he r.ear 2002, Dan Wells, policeman and amateur collec-

tor, and Don W,\'1isl<, landorvner, rancher, and amateur collector. LocAl'IoN: Don ar-rd Allison Wvrick Ranch, north of Baker, Fallon Count\', N'IT'(Fig. l.l, site 43). FoRN{ATIoN: Hell Creek Formation. EXCAVATED: Dan Wells 2002 and 2003. Black Hills Institute field crerv 2004. REPosi'roRy: Currentlv housed at the Hor-rston Museum of Nature and Science, Houston,'l'X. DESCRIBED: Partial descriptior-r bi,'Larson and Donnan (2004). SKELETAL RENlAINS: The skuil consists of a partial braincase, the right

squamosal, postorbital, jugal, surangr-rlar, articular, prearticular, and angular. The postcranial skeleton consists of 2 nearlv complete legs and feet (lacking to date onlr,the left tibia, astragalus, calcaneum, I left tarsal, both metatarsal I, and 5 pes phalanges from the righi

foot).'l'here are 22 vertebrae (5 dorsal, I cervical, and ll caudal), 20 ribs (5 cen,ical and 15 dorsal), both ischia, right pubis, and right

Neal L. Larson

iliurn. It also has a left scapula, coracoid. t'iumerus, ulna, carpals, and all 3 inetacarpals. Seventeen gastralia hare been found rvith the skeleton to date. co\,rpLErENESS: A totai of I14 bones (to dater. or J8% of a skeletor-r by bone count. oN DISpLAy? No, but preparation of the skeieton mav be viewed at the Black Hills Institr-rte of Geological Research, in Hill Cit\', SD. coN,IlIENrs: Intrigued by'the find, \Vells took a bone to the Black Hills Institute for identification. He returned to the site the next sumrrer and began to excavate in earnest. Dor-r Wr.'rick realized the importance of the find u'hen legs, foot bones, and vertebrae started appearing. He called a halt to the digging, contacted the Black Hills Institute, and arranged to har,'e them fir-risl-r the exca.,'ation.'fhe name "Wvrex" is a combination of tire first Z letters of Don's last r-rane and "rex." In N{a1'2004, Biack Hills Institr-rte began the first live online Tyrannosaurus rer excavation. With dailv reports, photos, and video segnents of the dai's digging, this dinosaur excavation extended far beyond the quarrl,and into schools, homes, and businesses for the next 3 r.r'eeks. Thousands of people a da1, 11'sn1 to the Web site to see rvhat nerv bones or discoveries had been rnade. To date, 22 tr-rrtles (Plesiobaena antiELa) have been unearthed at this site, frorn complete to disarticulated and fragmentary shells. \Vl'rer w'as buried on the edge of ar-r ancient pond or lake, and these turtles had perhaps been feeding on the carcass. It is unknorvn at this point vn4rat caused the death of either the T. rex or tl.re turtles. Son're of the exciting discoveries u,ith \Vy'rex are carpals along n,ith 3 rretacarpals frorn the left hand (see Lipkin and Carpenter this i'ol-rme), and 2 nearli,'complete feet. During preparation, several patches of skin (Fig. 1.268) u'ere found with the skeletor-r. Most of the skin patches (rnore than a clozen) ivere for-rnd on the bottom side of the articulatecl tail. The iliscoven' of skin il'ith W)'rex is a first for T rex. Plans are currenth, underlr,a)'for further excavation at the site ir-r l-rope of finding rnore of the skeleton. The preparation of the skeleton mav be r"ieu,ed bv the public at Black Hills Institr-rte of Ceological Research in Hill Citt', SD. Ou'nersl-rip of the specimen is currenth' being transferred the Houston Nlh,rseurn of Nature and Scier-rce, r.rfiere it is scheduled to be on display bv 2009.

LACM 7509trr0r67 (Thomas) DISCovERED: Tl-re vear 2003, Bob Curry, scl-roolteacher and amater-rr fos-

sil collector.

I-ocArIoN: BLM land near Ekalaka, Carter Countr',

\lT

(Fig.

l.l,

site

4+).

FoRMATIoN: Hell Creek Formation. EXcA\ATED: An ir-rten-rational creu'from the Los Angeles Countr', 2001-2005.

\atural Historv

Nh-rseum

of

Figure

1

REPosIToRY: 'l'he Natural Historv Nluscurn of [,os Ar-rgeles Cour.rt-v, Los

.21 T^c^as,

LACM 75A9:tC157, durrng exca,a: cn tA); right fer'-' g,rrnQ eXCd-

vatto. B,,igntdentary 'C. P'rcros.'tA) Doug Goodreau; (B) Ursula Goelich, (C) Gary Takeuchi. All photos courtesy Natural History Museum of Los Angeles County.

Angeles, CA. SKELE'rAL REN{AINS: Frorr Liiis Chiappe

(l'ritten comrnunication

2005)

"'I'he skuli consists of a complete braincase, postorbital, both jugals, scprarrosal, quadratojugal, quaclrate, lacrimai, both frontals, both rnax-

illae, ectoptervgoid, both clentarics, ancl at least one set ofarticulated skull bones but in jackets but thei' cannot be identified at tliis time). There are also 30-35 loose teeth ancl a feu,rnore in sittr. The skeleton consists of complete legs ancl feet postcler-itarv bones (there are other

(rriissing

I r.netatarsal and sorne phalanges, a feu dorsals, the sacrun, about 20 caudals, along lr.'ith rnanv ribs and gastralia. Thc pelvis includes both ilia and ischia. Both scapula ancl coracoids are presen,ed although no forelimb elements are knor,,'rr at the nrornent." coNrPLETENliss: Atotal of ntore than 110 bones (to date). or more than 1t-o/.

of a skeleton by bone cour-rt.

ox nrspley? No. naned'fhornas br,tire discor,erer, Bob Currr'. in hr.,nor of his brother. Frankie fackson of N{ontana State lJniversitv informecl l,uis Chiappe (director of the Dinosaur Institute at the L,\CN'I) of the cliscoverr'. The cxcavation took 3 seasons, during rrhich ther collectecl about 130 blocks, sonre containing several eleme nts. \luch of the specinen remains trnpreparecl, so the num-

CoNINIENTS: Tl're clinosaur nas

ber of rccognizccl elements is likeli to increase (Lr,ris Chiappe, rvrittcn conrn.unication 2005).

48

Neal L. Larson

Figure 1.28. lvan, during excavation showing scap u I a -co racoid, ri bs, and other bones. Photo courtesy Gary Olson.

Wayne DISCovERED: The vear 2004, Gary'Olson, professional collector. LocATIoN: Sor:th of Rhame, southr.r,est Borvman County, SD (Fig.

I.l,

site 45).

I,-oRMArIoN: Hell Creek Formation. EXCA\A'I'ED: Gary Olson and Alan Komroskr', 2004-2005. REPosIToRY: None; currentlv in possession of tl-re collector, Fargo, ND sKELETAL REN{AINS: This incomplete specirnen consists of 19 caudal and I dorsal vertebrae, 2 chevrons, several rib (and/or gastralia) segments, plus some other unidentified parts (Garr.'Olson, personal

commur-iication). CoNlPLETENEss: Tlver-it-v-four bones, or B% of a skeleton by bone count. ON D]SPT,AY? NO.

coMNIENrs: A disarticulated. u,eathered skeleton. Ivan DISCovERED: 'l'he 1,ear 2005, Gary Olson, professional collector. LocArIoN: North of Br-rffalo, r-rorthwest Harding County', SD (Fig. 1.1, site 46).

FoRNIATIoN: Hell Creek Forn-ration. EXCAVATED: Gar,v Olsor-r ar-rd Alar-i Kornroski; 2005.

currentlf in possession of the collector, Fargo, ND. SKELETAL REMAINS: Gar,v Olson (persoral communication 2005) relates REPoSIToRY: None;

that the skeleton consists of a nearly complete pelvis, with paired ilia (top half eroded), paired ischia, and paired pubes articr-rlated to the sacrurl. Ivan has one leg, consisting of a femur, tibia, fibr-rla, and astragah-rs. The feet contain 2 metatarsals ancl 6 pes phalanges. The body has a fusecl scapula coracoid, an estin.rated l5 cenicai and ciorsal vertebrae, and approxir-nately 25 cervical and dorsal ribs (this rib colrnt mav aiso include some gastralia), approrimately 25 caudal vertebrae, and an estin.rated l0 chevrons.

r'ears of fyrannosaurus rex

coNrpr.r,rE\ESS: A total of II6 bones, or )9% of a skeleton bv bone count (Carr Olson in'u'entorv). oN lrspr,.*'? No. coNIuENt s: Ca11,Olson n,as hunting for fossils r,i'hen he l-rappenecl upon several bones of a large theropocl r.veatherir-rg out of the hillside. Exposecl nere tlie fermr, tibia, metatarsals, pes phalanges, and large number of rib and bone scraps. He planned to ciub it Ivan the Terrible, but ur-rfortunatell', the specirnen il'as not for-rnd n'ith a skull, scr he called it just Ivan. Olson explair-ied that he dug all aror_rnd the skeleton, but it appears that if Ivan u'as origir-rally buried u'ith its skull, it ri'e:rthered or-rt long ago. Tl-re preservation is excellent.

Additional lmportant Specimens

The lrolotr,pe ol

N4arLospondylus gigus Cope, 1892, consisted of 2 large theropod cerr.ical vertebrac (onl1' I vertebra is knori'n to exist toda_v). It rvas later disctrssed and reclcfined asTtrannosdurus rex by Osborn in 1916. In 1905, Barnr,rrr Broun collected anotl-ier, r,erv partial, Tyrrlnnosar-Lrtrs rex specimen frorri Hell Creek, N4l'. According to Osborn (1906), the specimen (A\'INH 5881) consistecl of the left fernur, both tibiae, left fibtrla, and 4 rlrctatarsals. Bron'r-r in 1908 collected a braincasc of aT. rex in NIT (AN{NH 5029 = CN,I 9379); it also has a splenial, articr-rlar, and a prearricular. 'l'he Arnerican N'Iusenm has another indir,idual T rer braincase (A\INH 5l17), collected bv Sternberg and figured bi,Osborn (1912). 'l'he N'luseuur of Palcontologl; University of Califomia, Berkeler., has several clifferent'lf,ranttosaurus rex specinrens, one a nraxilla (UCNiP 118742), the other a maxilla u,ith dentaries (UCN4P 13l5El), both fronr N{ontana. 'l'he Science N,'luseunr of N,linnesot:r has the anterior uortion of a brainc:rse from South Dakot:r (N{N4S 5l-2004) (\,lolnar 1991;. T}re Nlr-rseum of the Rockies collected a portior-r of a braincase in NIOR l13l (also referred to as J-rex). There is also a large partial the ropod specinen from the Tornillo Forrration of \\'est Texas that u,as described as T. rex (Lar','son 1976), but Carpente r (1990) thought that it rl'as norphologicallv too different to include it in the species (although Carr and Willian-rson 200,1 believe it i$. Williarnsor-r and Carr (2005) reportecl on an adclitional, vet fragrrentary, Tyrarntos(luruE rex specirnen (u,ith dentarr) frorn the Naashoibito N4enber of the Kirtland liormation in Nen, N'lexrco. There ale reports of 2 aclditionalT. rex skeletons cliscor,'ercci cluring the slrrrrner of 2005 frorn the Hell Creek Forrration in Harding Countr'. Althotrgh I ha'n'e seen a fen'bones frorn these specirlens, it is still premature to providc ani,'details on their completeness or significance. Tlrere arc nllrrerous less coirrplete Tt'rcntnosourus rex specirrrerrs rro bones or fen'er) in r.arious collections across North Arnerica and Europe (e.g., Natural Historr,Nluseum, l,ondon, Englancl, UK) that have not been inchrdecl in this srrmmarr'. It certainlv appears probable that more T rex discoveries l ill be rliade ir-r tl-re near futr,rre. With so manv ne\\'specinens to stuclr', there is still the potential to learn ntuch more about the nrost far-norrs of all tlie clinosaurs , T. rex.

Neal L. Larson

No. of

Specimen

Bones

Percentage

of Skeleton Sue FMNH PR20B1

219

73o/o

Stan BHI 3033

190

63%

Table 1.2. Twenty Most

Complete Tyrannosaurus Rex Ske/etons

Note.-See text for detarls.

N/loR 555

l4tr

49%

* The bone count was

AMNH 5027

143

48%

Ollie*

124

41%

provided by others, or the number is estimated

Scotty RSM 2523.8*

120+

40o/o+

Samson (Z-rex)*

121

40o/o

980*

120

40%

lvan*

116

39o/o

Wyrex BHI 6230

114

3Bo/o

MOR 1125

111

37

110+

37 o/o+

'101

34o/o

Black Beauty RTMP.8'l .6.1

85

28o/o

SDSN/ 12047

82

27o/o

Duffy BHl4'100

79

26%o

LACM 23844

74

25o/o

Tinker SD rollerted bv Fatman and Ferrel*

73

240k

UCRC V1*

60

20Yo

MOR 009

5B

190k

Pecks rex MOR

Thomas LACM 7509/1

01

67*

Bucky TCM 2001.90.1

because

the preparation

not yet complete. For some specrmen5, Ine actual bone count may go up (with further preparation) or down (if gastralia were identified as ribs). is

o/o

From all of the inforrnation ttrat could be learned from contacting people personallr', visiting rrulseLlrns, reading publicatiorrs, and rese arctring on the Internet, it trppears that there are currenth,46 knorin Tt,rarLrLosaurus rex specirnens n'ith l0 bones or rnore (Tablc l.i). As can be seen frorr Figr-ire I.1 and Table 1.1, ntosl'I1,76171116sdurus rex skeletons were collected just south of Fort Peck Lake, near the tl'pe of Flell Creek Forniation, n'itli a second large conglonreration near the border of N'lor-rtana, North Dakota,

and Soutli Dakota. Tlie exposures of tl-re Hell Creek Forn-ration are

ex-

tensive ancl ri'ell exposed in these regions, r,vhich most likelr, is the reason for the discoverv of so rnanv specirnens from these areas. Although felr,er specimens are knon'n from other regions, there is cverv reason to belier.e tl-rat

aclditional specirrens n'ill be found. In snntrnarv, then, the range of T

rex is tl-rerefore knon n to inciude nearlv tl-re entire Western Interior.

Thcre is aluavs nruch discussion as to uhich is tlie rnost cornplete 'l\'rannosaurtLs rex skeleton, or lr'here each skeleton lies according to the arnount of completeness. For that reasor-r, the 20 rnost complele T. rex skelctor-rs are sLurmarizecl in Table 1.2.

Thanks to Peter Larson and Robert Farrar for proi idrng me ri ith quite a bit of this information ancl also for the rnuch-nee cle d cditorial he$ during the clrafting of this chapter.'l'lranks to Kennetli C.irp.:rtcr and Peter Larson for

Acknowledgments

51

their patience, editing, and tl-re organization of this publication.'fhanks to the Black Hills \'fi-rseum of Natural Historl'for organizing the 100 Years of Tyrannosattrus rex S1,n-rposium in June 2005.'l'hanks to John Babiarz, Japh Bo1,'ce, Kenneth Carpenter, Luis Chiappe, Phil Currie, Kraig Derstler, Bob Harmon, Rick Hebdon, Barrv James, Christine Lipkin, Nate N4urphv, Cary Olson, Scott Sampson, Richard Slaughter, Craig Sundell, Tom Williamson, and the Black Hills Institute for providing r-r-re w'ith muchneedecl information on the specimens. Larry Sl-raffer helped by cleanrng up and organizing the manv photos of T. rex. Thanks to all of the different photographers, lr'ho are credited in the figure captions. And finally, a brg, special thank vou to each and everv one of the landowners (ir-rcluding the U.S. and Canadian governrnents), lvho allow'ed access to the discoverers and the collectors of these rvoirderful ar-rcl fascinating creatures.

References Cited

Bakker, R. 'f. 1986. The Dinosaur Heresies: New Theories Llnlocking the Mystery of the Dinosaurs and Their Extinctiotl. Zebra Books, Neu' York. Bakker, R. T., Williams, \'I., ancl Currie, P 1988. Nancttyrannus, a ne\v genlrs of pvgr-nl' t1'rannosaur, from the latest Cretaceous of Montana . Hunteria l(5):26. B;ork, P. R. i9E2. On the occ!-rrrence of Tyrannosaurus rer fronr northrvestern Sor-rth Dakota (abstract). Proceedings of tlrc South Dakota Academr- of Science 61:161-162.

Brochu, C. A. 2003. Osteologl' of TtrannosatLrus rex: insights frorn a nearll'corrplete skeleton ancl high-resolution compr-rted tonrographic analvsis of the sktrll. /ourrral of Vertebrate Paleontology 22, N{erroir 7, Supplement to 4. Carperrter, K. 1990. Variation in Ttrannosaurus rex. P. 141-i45 in Carpenter, K., and Crrrrie, P J. (eds.). Dinosaur S),stematics: Approaches and Perspectives. Carnbrid ge Un ir.'ersitr, Press, Can-rbrid ge. 2004. Redesciption of Anktlosaurus nugniventris Brou,n 1909 (Ankvlosauridae) frorn the Upper Cretaceous of the Western Interior of North - Anrerica. Canadian lotLrnal of Earth Science 41: 961-986. Carpenter, K., ar.rd Smith, N'I. 2001. Forelirrb osteologv and biomechanics of Ttrannosaurus rex. P.90-1.16 in Tanke, D. H., and Carpenter, K. (eds.). ArIesozoic Vertebrate Lilb. lndiana Universitr, Press, Bloornington. Carper.rter, K., and Young, D. B. 2002. Late Cretaceous dinosanrs fron the Denr er Basin. Colorado, Rocky X,Iountah Ceology 3 i-(2): 23 /--251. Carr,'f. D. i999. Craniofacial ontogenr,in'I\'rannosauridae (Dinosauria, Coelurosauria). lournal of \lertebrate Paleontologl, I9(.)):49 t--520. Carr,'l'. D., and Willianrsor.r, T. E. 2000. A review of T\'rannosauridae (Dinosauria: Coelurosauria) fron Ner,,,\'Iexico. P il3-145 in l,ucas, S. G., and Heckert, A. B. (eds). Dinosaurs of Nerv \'lerico. New Mexico \4usettm of Natural Historl, and Science Bulletin 17. Carr, T. D., and Willian.rson, T. E. 200+. Diversitl'of Late Nlaastrichtian Tyrannosauridae (Dinosauria: Theropoda) frorn n,estern North Arreric a. Zoological lounnl of tlrc Linnean Society 112: 479-58. Cope, E. D. 1892. Fourth note on the dinosauria of the [,:rramie. American N aturalist 26 : 7 5 6 -7 5 8. Connter, D. 1996. T-rex: Tlrc RealWorld (r,ideo). Off Line Video, Butte, \,IT. Crrrrie, P ). 1993. Black Beautr'. Dino Frontline 1:22*36.

Neal L. Larson

2003. Cranral anatoml of tvrannosaurid curo:aurs

frorr the Late Creta-

ceotrs of Alberta, Canada. Acta Paleaeontr,'iizictt Polonica 48(Z): 19I-226.

-. Davies, \'I.

J. 1997. The curse of T. rex. Nolrr r rdeo . \\.GBH Boston Video, South Burlington, VT. Derstler, K., and N,ll'ers, J. 2005. Preliminan accoLrnt of the tl,rannosaurid "Pete" frorn the l,ance Formation o[\\'ronring. P, ]0 in l00Years of Tyrannosdurus rex: A Symposiunr, Abstracts. Black Hills \{useLrm of Natural His-

torl', Hill Cit\', SD. Dingrrs, L. 2004. Hell Creek, Montana: Atnerica's Ket, to the Prehistoric Pasl. St. N'lartin's Press, Nelr, York. Donrran, K., and Counter, D. 1999. 'f he Rex-Files: STAN (r'ideo). Counter Productions & Black FIills Institute of Geological Research, Hill Cit,v, SD. 2000. The Rex-Files: SUtr (r'ideo). Counter Productions & Black Hills Institute of Geological Research, Hill Citv, SD. -. Erickson, G. NI., Lappin, A. K., and L,arson, P. L. 2005. Androgvnous rar-the utilitv of cl-revrons for deterrniling the sex of crocodilian and non-alian dinosaurs. Zoolog,t 108: 27 i- -286. Fiffer, S. 7000.T1-rannosaurusSue. \\'. H. Freeman, Neu'York. Gilletie, D. D., Wolberg, D. L., and Hunt, A. P 1986. TyrannosaunLs rex front the N4cRae F'ormation (Lancian, Upper Cretaceous), Elepl.rant Butte Reservoir, Sierra Corurtr', Nerl, Mexico. P. 235-238 in Clemons, R. E., King, W E., N{ack, G. H., and Ziclek,J. (eds.). New Mexico Ceological Society Cuidebook, 37th Field Conference, Truth or Consequences Region. Nerl Nlexico Geological Societv, Socorro, NNI. Glut, D. F. 1997. DinosatLrs: The Etrc1,clo1tedia. N'lcFarlar.rd, Jefferson, NC. 2000. Dinosaurs:'llrcEncyclopedia,Supplement I. \,IcF-arland, Jefferson, NC. Dinosaurs: Tlrc Encyclopedia, Supplemart 2. N,lcFhrland, |efferson, NC. -. 2002 2003 Dinosaurs: Tlrc Encyclopedia, Supplemen f 3. \4cFarland, leffersor.r, NC. -. 2006. Dinosaurs: The Encyclopedia, Supplemen I N,IcFarland, NC. -Holtz, T. R., 2004.'fr,'rannosauroidea. P. lil-li6 in'1. Weisharnpel,Jefferson, D. B., Dod]r. -. son, P, ar.rd Osn.r6lska, H. The Dinosauria. Zncl ecl. Lhriversitl of Californra Press, Berkelel,.

Horner, l. R., and Lessen, D. 1993. The Complete T. rer. Sirnon & Schuster, Neri,York. Hurum, |. FL, ancl Sabath, K. 2001. Giant theropod dinosaurs from Asia and North An-rerica: skulls of TarbosatLrLLs bataar andTt,rannosaurus re.x compared. Acfa Palaeontologica Polonica 48(2): 161-190. Johnson, K. R. 1996. Description of seven cornmon fossil leaf species from the Hell Creek Forrration (lJpper Cretaceous: Upper \{aastrichtian). Nortlr Dakota, South Dakota, and \{ontana. Dent,erMuseumof NaturalHistory Proceedings, Series

3( 1 2).

Larson, P. L. i994. Tyrannosaurus sex. P 139-155 in Rosenberg, G., ar.rd Wolberg, D. (eds.). Dlno FestProceedings. Paleontological Societl, Special Pub-

lication

7.

The king s neu,clothes: a fresh look atTlranrtosatLrtLs rex. P. 65-71 in Wolberg, D. L., StLrmp, E., and Rosenberg, G.D. Dinofestlnternational - Proceedings. Acadernv of Natural Sciences, Philadelphia. 2000. Cranial rnorphologr', mechanics, kinesis. and variation irtTyrannosaurus rex. In The Rex Files: Scientific Papers ,utd Popular Articles and -. Miscellaneous Information on Tyrannosaurus rer. Black Hrlls Institr,rte of Geological Research, Hill Citv, SD. Larsorr, P. L., and Donn:rn, K. 2002. Rex Appeal. thc .:,rna:in4Stor1,of Sue, the I99

i-.

53

Dirtct:dL,r thttt Changed Science, tlrc Lav'

tnd \,Iy LllZ. Inr isible Cities

Press,

\lontpeli.r. \'T. lU0+

Borzes Rocft.

Invisible Cities Press. \lontpelier. \''l'.

Larsorr. P. L.. and Rigbv, K. 2005. IrLrrcula olTtrannosaurus rex. P.247'255 in -. K. Carperiter i.ecl.j.'l-he Canitorous Dinosaurs. Indiana L]niversitv Press,

Bloontington.

D. l9;6. T1,rarutosaurus andTorosaurtLs, \,laestrichtian dinosaurs frour '1'rans-Pecos,' I'eras. our nal of Paleontok gt, i 0 : I i 8 6.1. l -

[,an,scrn,

1

l,ipkiri, C., ancl Sereno, P C. 2004. The furcula o{Ttrarn'tosaunLs

rex.

lournal of

\lertebrate Paleontologv- 24(Suppl. to 3): 83A-8"1A. \,{aleev, E. A. 1974. Gigantic carnosaLlrs of the familv'li rannosauridae. Resu/fs of the Soviet-X/kngolian Paleontological Expeditiort l: ll2-191. Nlclntosh, J. S. 1981. Annotated catalogue ofthe dinosaurs lReptilia, Archosauria) in the collections of Carnegie Nlusenni of Natural Historv. Carnegie Nluseum of Natural llistory Bulletirt l8: l-67. \,iolnar, R. Fl. 199i. The cranial norphologv of'fyrannosattrtLs rex. Palaernttogntplzic,t ll-: I 1--l-('. Nen'marr, B. II. 1970, Stance ar.rd gait in thc flesh-eating Ttrannosaunts. Biological lournal of tlte Linnean Society 2:II9-123. Olshevskr, G., Ford, T. 1,., ancl Yarramoto, S. 199;.'l'he origir.r and er,olutior-r of the tlrannosaurids, part 1. Klorlug aku Saizensen lDino Frontlinel9:

92-t99. Osborn, H. F. I90;. Tt,rdnnostlurus and other Cretaceous carnilorons dinosaurs. tsulletin of the American NIusetLnt of Natural History 2I:259-265. 1906. Ttrannoscturus, Upper Cretaceous canrir,orous dinosaur (secor-rd comnrrnicartion). Btlletin of tlrc Anterican Nluseunt of Natural Historl. 22:781-296. 1912. Crania of Tr.'rannosarLrlts ancl A/losourus (Ttrannosaurus contribution No. 31. \,lentoirs of the American lluseurn of Natural Histon' 1: 1-30. I9I6 Skeletal adaptations ofOrnitholestes,Struthionintus,T1,rdnnctsaurus. tsulletin of the Anerican \luseun of-Natural Histort, 77: 733- i- ,- I. -. Paul, G. S. 1988. Predatory Dinosaurs of the \\rorld: A Contplete lllustrated Clulde. Sinron :rnd Schuster. Nen York. Russell, D. A. 1970. T\'rannosaurs frorn the Late Cretaceous of Canada. National NltLseunt of Natural Sciences, Publictttiotrs in Paleontolog,- l: l-1.1. Santpson, S. D., and Loenen, \,1. A. 2005. Tyrdrtnosattrus rer from the Upper Cretaceous (Nlaastrichtian) North llon'r Fbrmation of LJtah: biogeographic and paleoecological irrplications. Iournal of \lertebrate Paleontolcter 25Q):469*412. Schri'eitzer, NI. H., Wittnei.er, l. L., and Horncr, J. R. 2004. A novel dinosaurian tisstre exhibiting unusual preserr,ation. lournal of \,'ertebrate Palecxttologt 24(Suppl. to l): lllA. 2005 One prettr.amazirrg Tt,rannosaurus rer: a prcsentation celebrating 100 r'ears of Tt'rtnrnosaunts rex. P. 36 in I0 0 Years of 'lt'rarnrcsattnLs rex: A - Sytnposhnn, Abstracts. Black Hills N,luseurn of Natural Historv. Hill Citv. SD.

Snith-ilill,

l]arstack Butte surrendcrs terrible Lzard: South Dakota inosaurs. Atner i c cu't \41est ( \.,larch/April ) : 2 3 -29. \\/illiarnson, T. E., and Carr, T. D. 2005. Latcst Cretaceous tr,rannosaurs fronr the San Juarr Basin, Neu'\'lexico. P 38 in l00Years of 'I\.rannosatLrtts rex: ASt,nrpositnn, Abstracts. Black llills \{useLrm of Natural Histon, Hill Citr, P. 1981.

rarrrcl rers d i g d

SD.

Neal L. Larson

The nr-rmber of bones in an adult'lyrdnnrt,'titirtL' rer skeleton is estinated at 100. Of these, 55 are skull bones, r'hich inclLrde JI cranial and 14 rnandible elen-rents. The cranial elernents consist of pairecl premaxillae, maxillae, nasals (fused), lacrimals, jugals, postorbitals. scluamosals, quadrates,

Appendix. The Skeletal Elements of Tyrannosaurus rex

quadratojr,rgals, palatines, ptervgoicls, ectoptcrr goids, epiptervgoids, the unpaired vorner, and the braincase.'I'he braincase consists of the unpaired

basioccipital, supraoccipital, basisphenoid, and parasphenoid, along ri,ith the paired parietals (fused), exoccipital-opisthotics, prootics, laterosphenoids, and fror-rtals. 'f he loil'er jai,r's consist of paired der-rtaries, coronoicls (also referred to as "supradentaries" bv sonre other authors), splenials, angu-

lars, surangulars, prearticulars, ancl articulars. Hvoids remain undescribed in t1'rannosarrrids, although there w,ere probablv at least 2 i:nTt,ramtosaurus rex. Teeth are not coltnted because thel'are shed.

'l'he axial skeleton (rninus the skull) contains ll.[ bones. It consists of l0 cen'ical vertebrae,2 proatlas, I8 cervical ribs, 13 dorsal l,ertebrae,72 dorsal ribs (the l2th and llth clorsal'"'ertebrae clo not have ribs), 5 sacral vertebrae, 44 caudal ','ertebrae (estinated, the actual caudal collnt for Tl. raTnosdurus rer is vet unknon'n), and .{0 to 42 chevrons (estirnated). Osborn (1916) estimated thatT. rex had 56 car,rdals, N{aleev (1974) estinated 40 and 45 in the Asian tvrannosaurid,'farbosaurus, Holtz (2004) belier,ed thattyrannosarlrs had fron 35 and 44 caudals, and Par-rl (1988) estiinatecl that there are J9 caudals in T. rer. The inost complete tail, FNiNH PR208l (Sue), has J6 caudal \rertebrae and w':rs restored u,'ith 47 caudal vertebrae (Brochu 2003). 'fhe nurnber of T. rex chevrons is also unknou'n because this nr-rrnber ultimatelv relies on the caudal count. Chei'rons probabl1, begin with tlie second caudal vertebrae, and they ma)' or rrav not have exter-rded to the last caudal r.,ertebra. The placen-rent of the first cher,'ron varies in living crocodilians and nonavian dinosaurs, and tl-re cher.'ron count varies as \\,ell (Erickson et al. 2005). I consider gastralia as derrnal elements and have not incltrded thern in this bone cotrnt. FN{NH PR2081 has a fairlv complete set of gastraiia of i3 pairs (Brocl-u,r 2003). Both TCN{ 2001.90.1 (BLrcky) and N{OR 980 (Pecks Rer) also have fairlv con-rplete gastralia baskets. Some T. rex gastralia are as large as dorsal ribs and are ofter-r confusecl or misidentifiecl as dors:rl ribs. The appendicuiar skeleton contair.rs 89 bones. 'l'he forelimbs har,'e 3l bones consisting of the furcr,rla,4 shoulder girclle (paired scapulae and paired coracoids), 6 forelimb (paircd huneri, paired ulnae, and paired radii), 4 rvrist (2 paired carpals), 16 mantrs bones (6 netacarpals and l0 manlls pl-ralanges-i.e., 5 in each hand). On the basis of N,,IOR 980 (Peck's Rex) and BHI 6230 (WYREX), Tyrannosar.rus re.t had 3 metacarpals in each hand, as in Daspletoscurus (Russell 1910r. r e t onlr 2 functional fingers on eacl-r l-rand (see Lipkin and Carpente r this r olurne). 'l'he hind lirnbs consist of 5lJ borres. rilrich irrclrrde tlre follourrrg: b pehic.rpaired ilia. pubes, and ischia), 6 leg (paired femora, tibiae . fibulae t, 8 ankle (paired calclnea. astragali. arrd ?-puired trrrsals,. arrl lr '' rr. . irr tlrc fcct ri prrirs of rnetatarsals and 14 pairs of pes phalangesr. I ir. trith rretatarsal \vas apparentlv nonfunctional and had no phalanges.

55

/1

-; ..::L.;* :.

,r',,F.,/

'',', |,,/

4;'/ i.'

" f.'liiffl'f: l=".*-

Figure 2.1 . Tyrannosaurus rex skeletal drawing (by W. D. Matthew) from Osborn (1905), based on a skeleton not fully collected or prepared from Montana.

Figure 2.2. Tyrannosaurus rex skeletal drawing (by L. M. Ster-

ling) from Osborn (1906), based on skeletal remains from Wyoming and Montana (AMNH 5886, AMNH 973, and AMNH 5881).

I I

i-r{ I

i

l I

/

WYOM

G'S DYNAM OSAU RUS IMPERIOSUS AND OTHER EARLY I

N

DISCOVERIES OF TYRAN NOSAU RUS REX IN THE ROCKY MOUNTAIN WEST Brent H. Breithaupt, Elizabeth H. Southwell, and Neffra A. Matthews

The first remains of t1'rannosaurids in Nortl-r Anerica u'ere discovered

in

Introduction

1855, when the farrous rvestern explorer, Ferdinand V. Havden, found

sorre large teeth in the Cretaceor-rs units of N{ontana. The foilowing year, Philadelphia paleontologist loseph Leid1,' (1856) described these teeth as tlrose of the carnivorous dinosaur Deinodon horridus ("horrifi'ing terrible tooth"). Cr:rrer-rtlv, most of these teeth represent the Late Cretaceous theropod Albertuaurus.

The discoverl'of ihe best-knou'n representative of the tr,'rannosaurids, Tyrannosaurus rer, dates back to 1874, w'hen Coloraclo schoolteacher Arthur Lakes found a "Fossil Saurian Tooth" (YPM 4192) in the Late Cretaceous Denver Formation near Colden, CO (Carpenter and Young 2002, p.239). This specirnen u'as sent to Yale paleontologist Othr-riel C. Marsh, and although it ivas not clescribed by hirr, it still resides in the collections at ihe Yale Peabodv Museum ir-r Ner,r'Haven, CT. From this same site ir-r the Denver Basin, mention is made bv geologist George L. Cannor-r of a large theropod jarv in 1888 (Cannon lB88), but further information and the specimen are unavailable. Over the vears, other specirnens (later to be identified as Tyrannosaurus rex) ll,oulcl be n'rade a','ailable to N,larsh by his collector, John B. Hatcher, from the uppermost Cretaceous of Wi,omirrg. These and subsequent discoveries are presented below.

In 1890, Hatcher founcl a partial right metatarsal IV (USNM 2110) in tne Lance Formation fron Lance Creek, Converse County (now Niobrara County), WY (Nlarsh lB90). The follorving vear, Hatcher continued to collect in ihe latest Cretaceous ur-rits of eastern \\'voming. Along Alkali Creek, he found a left femur, tibia, and partiai fibula (USNM 8064) at one locality, and (r,vith the help of A. E. Sullins) a right ilium (USNM 6lB3)at another site along this clrainage (N4arsh I892r. \larsh (1896) identified all

Dynamosaurus and other Tyrannosaurus Specimens

of tl-rese Wvorning specimens as representing a large iornt of Ornithomimus

(O. grandis). This "grand bird-rnin-iic" was "one of tl.re rnost destructive enemies of the herbivorous Ceratopisidea," accordiirg to \,{arsh (1896, p. 206). At the same time that Marsli's collectors u e re erploring the Rock1.

57

Nlountain West, Niarsh's archrival, Edn'ard D. Cope of Philadelphia, u,as also collecting in similar areas. While in South Dakota in 1892, Cope discovered in the Upper Cretaceous Ceratops Beds (see N,larsh l896; Hatcher 1893; Hatcher et al. 1907), trvo large, n'eatherecl, r'ertebral fragnrents (ANINH 3982) that he narred ManospondthLs gigas, "giant porous vertebra" (Cope 1892). Although he believecl these r,ere from one of tl-re large agathar,rrnid ceratopsians that I're hacl studied previouslr (Breithaupt 1999), the single specin-ren currentll'residing in at the American Nluseunr of Natural History in Neu'York, a dorsal r,'ertebral centrur.n (AN{NH l9E2) is fronr aTtrarLnosaurus rex (see N. L. Larson this voltrne). The ]ure of the Ceratops Beds of the \Vest ri'oulcl leacl to some of the rrost irnportant discoveries of Tyrannosaurrs rex in the earlr' 1900s. In 1900, paleontologist Henry'F. Osborn sent famecl clinosanr hunter Barnum Brou'n to the Cretaceous Ceratops Beds to Enrl'lriceratofs specimens for clisplav at tl-re American N'luseum of Natural Historr, in Ne',i' York. Broli.'n, H. N4.

Smith, and their cook, Arrrstrong, explored the siruilar areas of eastern Conin eastern \Vvoming, as had Hatcher previously. After getting off the trair-r at hidgemont, SD, thev trareled r-rp the Chey'enne River to the junction uith Alkali Creek. In the Cretaceor-rs or,rtcrops of this area, ther' ',1'ere successful in finding sorne fraginentarr, Triceratops remains. Continr-ring up a srnall tributan' of Sei'en Nlile Creek, Brorvn and crerv found in the latest Cretaceous deposits of thc arca leaf verse Countv (now Niobrara Countv)

inrpressions, a fossil turtle, ancl aTriceratops pr-rbis, as w'ell as a disassociated partial skeleton (approximatel,t' I3% complete) of a large "Ceratosaurus-hke" carnir''orous dinosar,rr, according to Brou'n (see Osborn I905).

'fhis specirnen (AMNH Field 12) corrsisted

of the lon'er jari's and teeth, various cervical and dors:rl vertebrae, ribs, and portions ofthe hips and linrbs (forrnerll,AMNH 5866, nou BN4NH R7995; see N. L. Larson this r.olunie), as rvell as numerolrs clermal plates (B\4NH R8001; see Carpenter 2004). N{ixed in n'iil-r this skeleton n'ere the teeth ancl jan' of a haclrosatir, the frill of a ceratopsian, and the teeth of ar-r ar-rkr'losaur, as r,i'ell as the scales of fish and other undeterminecl bones, "all eviclence of the animals last rreal," ac-

cording to Brolr,n (see Bror,r'n and cre'"r, opened trp a 4 bi l2 m (14 b1'40 foot; qllarr\,in the soft, fir-red-grained clavstones and siltstones ir-r the Lance Forrnation, approxim:rtely'4 km (2.5 niles) north of Chevenne Rir,'er (not 6 milcs in Weston County; as noted bv Osborn 1905; see Breithaupt et al. 2006). Osborn (1905) naned this partial skeleton D),narnosaunrs imperiosus ("powerful inperial lizard"), in particular because of the osteoderms (novn knorvn to belong to an ankf iosaLrr-see Carpenter 200,1). Osborn (1905) also narned TyrarLnosaurus rex ("king of the tvrant lizards") for a partial "Deinodon-like" skeleton (forrrerll AN'INH 971, nou CN{ 9380) found rn the upperrnost Cretaceous Hell Creek Forrnation of N,Iontana br. Broil'n in 1902 (see N. L. l,arsor-r this r,'ohrme). Osbom n'as spurreci to publish l-ris 1905 paper on Cretaceous carnivorous dinosaurs before all of his rnaterial had been fulll collected and prepared (1I%) fror-r-r tl-re l-rard concretionarr' sandstone rr-iatrix because the Carnegie N,Iuseun vn,as also preparing a partial (9%) skeletor-r of a large tl'reropod at the same tirne). This specimen (C\l 1-100), rvhich included parts of tl-re skull and loner jari's, r,arious 58

Rrant l-.1 Rraithat vP( t^t at )l r( vr,

vertebrae, ribs, and hip and limb bones. as r,.cjr ls r.arious ornithischran fragments, n'as also foi-rnd in the Lar-rce Fornr.rtioit of Converse Courrri,,

(nou' Niobrara Countv, WY) along Schneider Creek bv former AN,INH emplovee Olaf A. Peterson in 1902 (N{clntosh 1951: see N. [,. Larson this volume). Because the Carnegie specirnert n as thought to include a skull,

Osborn \\,as concerned that Peterson rr'o.ld pLrblish o. this large carnivorous clinosaur before hin (Breithaupt et al. lt-)l)6 i. Once the \Vi.on-ring and Nlontana rnaterial had been prepared (bv Richard S. LLrll and bl'Paul Miller and Peter Kaisen, respectivelv), Osborn (1906) svnonvmized Dynamosaurus imperiostrs n ith Tyrannosdurus rex, utilizing botl-r specin-rens in his clescriptions ancl figures (Fig. 2.2). Horvever, even as late as 1916, Osborn still contencied that the derrral scures of the "Dytamosdurus imperiosus" specirren r','ere unlike those of any ornithischian, and he believed that tl-rev mal l-rave exter.rded dolr'r-r the back ar-icl along the sides of T. rex, "the rnost superb carnivorous mechanism among the terrestrial Vertebrata, in il'hich raptorial destructive power and speed are cornbined" (Osborn 1916, p. 762). Interestingll', close examination of thesc osteoderms shou,s a series of depressiorls that resernble bite marks from a large theropod. In fact, these anklyosaurian scutes mav have represented the last meai of the D. imperiosus speclmen. Brorvn continued to u'ork in N,,{oniana, and in 1906, he uncovered ar-r even rrore conplete skeleton of T. rex in N{ontana (Osborn 1912), inclucling the first complete skull and most (45%) of the skeleton (AMNH 5027).

After tl're 1908 field season, the Arnerican N,luserrm of Natural Histor,v had 2 fairlv corlplete skeletons olTyrannoscLLLrLLS rex, n'hich thev planned to nonnt in a drarnatic, interacting pose (see Osborn 1913). Hou,er,er, because of the high cost, onh' the specirnen (AI'INH 5027) found in 1906 rvas exhibitecl (see Osborn l9l6). B,"" 1912, the museum had obtained a total of 8 specimens of Tl,rannosdurus rex frorn Wr,'oming ancl N'lontana. Hon'er,'er, rnar-rv of the best specirrens were later sent to other mrlsellms. The tvpe specirnen (A\,fNH 971) of 'fyranrLosaurus

$':rs solcl to Pittsburgl-r in l94l (CN4 9380) and in 2008 '"er remountecl for displar'. The tvpe skeleton olDynamosatLrus imperiosus (AN,INH 5866), along n'ith parts of ANINH 97),5027, and 5881, u,ere sold

."vas

to the Britisir N{useum (Natural Historr,) (BN'INH R799) in 1960. The D. imperiosus rraterial rvas used ir-r a' interesting half-rriour-rt displav of tliis dinosatir, w'here it exhibited one of the first state-of-the-art poses (i.e., a shorter tail carried in the air) bv Barne_v Nervman (1970). In addition, D. imperiosus \\'AS one of the first T rex specir'rens to undergo bone histologrcal stucly (Reid I984). After being or-r displar'for a nur'ber of years, most of the composite half-mo.nt skeleton is norv in tl're research collections of the Natural Historr,N4r-rseum, although one dentarv rer.nains on displav. In 1996, a partial (12%) skeleton u'as found in \\reston Cor,rntl', WY Althorrgh it n'as touted as being more of the "Dlncno sdurus imperiosus" specirnen (Bonhans and Butterfields 2004) found br Brorvn, it u'as actually found manl niiles north in a different countr of e astern W1'orning (see N. L. Larson this voh-rrre).

Wyomtng

:

1..'amosaurus imperiosus

Building on the for-rr-iclational research done in the late 1800s and earlyI900s, continued ll'ork in the r-rppermost Cretaceous formations of the \Vestern Interior has produced rnanv irnportant additior-ial specimens of Tvrannosdurus rer. Currentl,v knot'n from dozens of skeletons frorn tl-re Western Tyrannosaurus rex was Interior (surnmarized bv N. L. Larsorr this "'olume), to clearlv one of the rnost impressir.'e creatures ever n,aik onr planet. After over a century ofresearch, discoveries during the last 15 l'ears provide interesting insighis about this dinosaur, and illustrate hoq' science progresses and ho',1.'our ideas on prehistoric beasts change through time as ner.r' inforrnation, technolog\,, and interpretations become available (e.g., Schrveitzer et al. 2005; Paul 2000; Hutchinson and Garcia 2002; Horner and Lessem 1993;

Farlon'at al. 1995; Carpenter 1990; BrochLr 2003). Although n-ruch has

been r,r'ritten abotrt this r,''ell-knoil'n dinosattr, nanr, questions stili remarn. Althouglr Tyrannosaurus rex itself is extinct, ideas regarding its life and times

continne to evolve.

References Cited

Bonlrarns and Btrtterfields. 2004. Catalogue of Natural Histort AtLction. San Francisco. Breithaupt, B. H. 1999. 'l'he first discoleries of dinosar-rrs in the Arnerican West. P. 59-65 in Gillette, D. D. (ed.). Yertebrate Paleontolog,- in Lltah. Utah Geo-

logical Surver' \iliscellaneous Publication 99(1). Breithatrpt, B. H., Southu'ell, E. H., and N,Iattheus, N. A. 2006. DynamosaurtLs imperiosus and the earliest cliscoveries of 'h'rannosaurus rex in Wr on-ring arrd the \Vest. P. 257-Z;8. Lucas, S. G., and Sullivan, R. (eds.). Late Cretaceous Yertebrates from the \\lestent Interkr. Ner'r' Nlexrco N'lttsettm of Natural Historv and Science J5. Brochu, C. A. 2003. Osteologl of Tl,rannosatLnrs rer: insights from a nearh'complete skeleton and high-resolution computed tomographic anall'sis of the skull. /ournal of Yertebrate Paleontologt, N'len.roir 7. C:rnnon, G. t,. 1888. On the Tertian Dinosauria tbund in Denver beds. Colorado Scientific Societt' Proceeclings 3: 140*147. Carpenter, K. 1990. \/ariatior-r irTlrannosaurus rex. P. 141-14) in Carpente r, K., and Currie, P i. (eds.). Dinosaur Ststenntics: Perspectit,es and Approaches. Can.rbridge Llnir,ersitv Press, Carrbridge. 100+ Redescription ol Artk,-losaurus magrLittentris Brou,r-r 1908 (Ank1' losauridae) fron.r tl-re Upper Cretaceous of the Western Interior of Nortli - Anerica. Canadian lotLrnal of Earth Sciences 41: 961-986. C:rrpenter, K., and Young, D. B. 2002. L,ate Cretaceous dinosaurs from the Denr,er B a s i n, C olo rado. Ro c ky \7 o utt ain G e olo g,r' 37 ( 2) : 217 -25 4 Cope, E. D. 1892. Fourth note on the Dinosauna of the Laramie. American Nafrzralist 26: t- i6-7 i8. Farlor.v, J. O., Snith, NI. B., and Robinson, J. \{. 199t. Bodv mass, bone strength indication, and cr.rrsorial poter-rtial of Tv-rdnnosdurus rex. lountal of Yerte.

brate Paleontoloy 15 6 1: 7 13 -7 25. Hatcher, J. B. 1893. The Ceratops Beds of Conr.'erse Cottntl', \\'1'oming. Anrerican lotLnnl of Science (ser. 3) I45: 135-144. Hatclrer, I. B., N{arsh, O. C., ancl Lull. R. S. 1907. Tlrc Ceratopsia. U.S. Geologrcal Survev Nlonographs 49. Horner. J. R., and Lesserr, D. 1993. The Cornplete Tl ra.t. Sirnon & Schuster,

Neu'\brk.

Rrant l-J Rraithzt t^f af

^l

Hr.rtchir-rson,

l. R., and (]arcia,

N,L 2002.

Tlrdnr...::.-r,,- uas not

a fast nrnner.

Nature 415:1016-1021. Leidy, J. 1856. Notice of the rernains of ertinct reptrle: and fishes, discor,erecl br, Dr. F-. \l Hal,clen in the badlands of the JLrclith Rirer, \ebraska "lerritorr'. Academt, ofNatural Sciences, Proceedings l5i6: -l--l Marsh, O. C. 1890. Description of nes'dinosaurian reptiles. AmericanlotLrnal of' Science 39:

El-86.

1892 Notice of neu,reptiles fronr the l,aranrie Forrl:rtion. American lournal of Sciertce 143: 449-453. -. 1896. The dinosaurs of North Anierica. Annttal Report, Llnited States Ceological Surler' l6: I+i-214. -. Mclntosh, J. S. 1981. Annotated c:rtalogue of the clinosaurs (Reptilia, Archosar,ria) in the collections of Carnegie \{use urn of Natural Historr.. Carnegie Museunt of NatLLral Historl'Bulletin 18:67. Neu'rrran, B. I-1. 1970. Stance ancl gait in the flesh-eating Tlrannosaurus. Biological lountal of tlrc Linnean Society 2: II9-123. Osborn, H. F. 1905. 'l),rannosaurus attcl other Cretaceous c:lrnivorous clinosaLrrs. Bulletfu of tlrc American Ntlusettm of N atural Historr 2I: 7.59-265 1906. Ttrannosaurus, L.lpper Cretaceous carnivorous dinosaur. Bulletin of the Arnerican Museum of Natural Histort 7-2:281-296. -. 1912 Crania of Tlrannos(llLrus and AllosatLrus. \'lentoirs of the American MuseLLm of Natural Histort, 1n.s.) 1:l-10. -. 1913 'In'rannosauruq restoration and nrodel of the skeleton . Billetin of the Anrerican Nluseun of Natural Histort, 32: 91-92. -. 1916. Skeletal adaptations of C)rnitholestes, StrtLthionirnus,Trrannosaurus. Bulletin ctf the AmericanMusetnt of NaturalHistort 35:773-7 t-1. -. Paul, G. 2000. Limb design, function and nrnning perfornrance in ostrich-mimics and tr,rannosaurs. P 251-270 in P6rez-Nloreno, B. P, Holtz, T. |., Sar.rz, J. L., and \Ioratalla. J. (eds.). Aspects oiTheropod Paleobiologt. Caia: Revista de Geociencias, NIusetL Nacional de Historia Naturc/, Lisbon, 15. Reid, R. E. I.l. 198.+. The histologv of dinosaurian bone, and its possible bearir.rg on clinosaurian phl siologt. Zoological Societt, of London Stn'rposia 57: 629-663. Schu'eitzer, N,l. H., \\,'ittnreler, J. L., Horner, J. R., and'lbporski, J. K. 2005. Softtissrre and cellular presen'artion inTyrannosatLrus rex. Science 307: "'essels

I9i7-1955.

HOW OLD IS I, REX? CHALLENGES WITH THE DATING OF TERRESTRIAL STRATA DEPOSITED DU RI NG THE MAASTRICHTIAN STAGE OF THE CRETACEOUS PERIOD Kirk Johnson

Intense interest inTyrannosaurus rex atxl other dinosaurs of the Heil Creek, Laramie, Lance, Scollard, Willolr,Creek, Frenchrnan, Denver, and Ferris forrnations (the Triceratops fauna) raises the obr.'ious question of the age ancl cluration of these formations. At the present time, this is a surprisingly difficr-rlt question to ansi,l'er. It is useful to divide the questior-r ir-r half: Over what time spar-r did these dinosaur-bearing formations form? And rvhat are the ages of specific dinosaur fossils? Because several of these forn-rations span the Cretaceous-Paleogene (K-

T) bounclarv, and because no in situ nonavian dinosaurs are knorvn

fron-r

above the K-T boundari', a definiiion of the K:T boundarl.serves as a usable

mininrtrm age for tlte Triceratops fauna. The K:f borindar,v is based on a stratotype in Tiu-iisia and is radiometrically' dated at 65.5 + 0.7 N,{a. The K-

T boundary can be recognized in terrestrial rocks of the Great Plains and Rocky N{ountains bv a combination of criteria, including disappearance of tlre palvnological Wodehouseia spinata Assemblage Zone, presence of iridium and shocked mineral anomalies, and reversed magnetic polaritv (elaborated in Hartn'ran 2002; Hicks et al. 2002; Nichols and Johnson 2002; fohnson et al. 2002). Al1 ofthese rnethods require laboratorv analvsis but can resoive the stratigraphic position of the bor-rndarv to a feq'millir-neters. Age resoh,rtion rvithin Nlaastrichtian rocks is much less precise and involves the use of rnagnetostratigraphy', radiometric dating, pollen/spore,

mammal, and ammonite biostratigraphy. The Maastrichtian Stage (final

t 0.6 Ma, on the basis of correlation of its stratotvpe in a qllarr)' in southvn'est F'rance to the rnarine strontiun-r isotope curve, and encls at the K:T bor-rndarv. Parts of fir'e geomagnetic polarity subchrons occlrr in the Nlaastrichtian (part of C29R, Cl0N, C30R, CllN, and part of CllR). Because Cl0R is brief (-10 kr), the 5.1 Ma of the siage of the Cretaceous) begins at70.6

Maastrichtian is essentiallv represented bt'a normal interval bor-rnded

b1

2 reversals. Great Plains N{aastricl-rtian stratigraphr is complicated b,v the Bearpaw marine transgression, rvhich resr-rlts in a section that is marine at its base and terrestrial at the top and to the uest. Because rnagnetostratigraphv and radion-retric dating can be applied to both marine ancl terrestrial strata, correlation shor-ild be possible. Horvever. onli tor-rr.\r+')/le radiometrrc How Old

/s T. rex?

Dating the I rex Beds

dates are knor,vn from forrnations that contain theTriceratops faur-ra: 66.56

+ 0.1 Ma from the Kneehills Tuff lust belou tlic Scollarcl F'ornation il Alberta (45 m belon'the Kjl');66.8 t 1.2 Nlla from tl-re upper N4eeteetse Formation (belou'the Lance Fomration and 200 n belou'the K-T) in Elk Basirr, Wl and 65.73 + 0.lJ and 65.96 + 0.21 N'Ia fron the Denver Forrnation (5 and 20 m belou'the K-Tboundarr', respectiiell'). N{eanuhile, ttre vonngest dated arninonite zones are Baculites grandis at 70.15 t 0.65 N{a and B. clinolobatus at 69.57 t 0.17 \'la, both from Red Bird. WY Thus, there is a gap of at least 2.77 NIzt in tlic n-riciclle N,Iaastrichtian n,here no radion-retric dates are knon,rr.

This gap coincides lvith the rrid-N'laastrichtian polariti'normal (C3()Ni so rnagnetostratigraphr,does not help resolr'e the isstre. There are onll' two pall'nostratigraphic zones in the N'laastricl-rtian, one in the very, early part (Aquilapollenites striatuslZ) ancl or-re ir-r the verr'late part (\\/ode hotLseia spinata AZ). These palvnological zones are onlv knou, in superposition in tr'vo cores in the Denver Basin. N'Iarrrrals of the Lancian North An-ierican Land \"{ar-r-rmal age co-occur u,ith the Triceratops faLrna, so thev share its poor time resolr,rtion rather than resolving it. A short-iern soltrtion l-ras been to trse the duration (frorr marine o'clostratigraphr') and thickness of polaritl'subchron C29R to project an age moclel clownsection frorn the

CllN),

Kjl'bor-rnclarl'to clate N4aastrichtian fossils ancl fornations. 'l'iris nethod I'ields ar-r age range of 66.86 to 68.0 NIa for the base of the Hell Creek l.'ornration in Nortlr Dakota and N'Iontana, and 68 to 69 N{a lor the Triceratopsbearing Lararliie Formation in the Denver Basin. This t1,pe of projcction is prone to inaccuracl because the K-T bounclarv and the tclp of C29R are separated in several sections b),a thickness that is -10% ofthe tliickness of the Hell Creek Formation. Thus, small errors coulcl bc grcatlv magr-rifiecl the dist:rnce to a much more distant poir-rt. Clearlt', rnore radiometric dates near the basc of the Triceratops lattna are needed to refine age rnodels for N{aastrichtian terrestrial fossils. The search for volcanic tuffs and bentonites near the base of the Hell Creek and in the top of the underlving For Hills Sandstone is a prioriti'for future rvher-i using t',1'o closelv spacecl points to extrapolate

research.

References Cited

Hartman, J. H. 2002. l{ell Creek Formation and the earll picking of the CretaceonslTertiarv boundarr,in the Williston Basin. P. 1-7 in Hartman, l. H., lohnson, K. R., and Nichols, D. J. (eds.). The Hell Creek Fornntion and the CretaceotLs-Tertiart, fiorrr4orl in tlrc Nortlrcrn. Creat P/ains. Geological Society of America Special Paper 361. Hicks, J. I.'., Johnson, K. R., Obradovich, ). D.,'Iaure, L., and Clark, D. 2002. Nlagnetostratigraphr,and geochronologl ofthe Hell Creek and basal Fbrt Union Formations of southu'estern North Dakota ancl a recalibration of ihe age of the CreiaceousJertiarv boundarv. P. i5-55 in Hartnan, J. H., iohnson, K. R., and Nichols, D. J. (eds.). Tlrc llell Creek Formtttion rmd the Cretaceousllertiary Boundart in the Nctrtlrcrn Great Pkirrs. Geological Socie tv of \rrrerica Special Paper 3(rl. Jol.rnson, K. R., Nichols, D. J., and Hartirial, j. H. 2002. Hell Creek Fbrrna-

Kirk Johnson

tion: A 2001 svuthesis. P. 501-510 in Hartnan, J. H., Johnson, K. R., and Nicl.rols, D. J ieds.). 'I'he Hell Creek F-ormation and tlrc Cretaceous-Tertiary Boundart' in the Northern Great P/alns. Geological Societr,of Arnerica Special Paper 361. Nichols, D. J. ancl Johnson, K. R. 2002. Palvnology'and microstratigraphv of Cretaceous-Tertian boundarv seciions in southriestern North Dakota. P. 95-143 in l'lartrnan, J. H.. lohnson, K. R., and Nicl.rols, D. J. (eds.). The HelI Creek Fornntion and tlrc Cretaceous-Tertiary BotLndart' in the Northern Oreat Plains. Ceological Societr,of ,\rnerica Special Paper 361.

How Old

/s T. rex?

65

Figure 4.1 . Discovery site for LDP 977-2.

.

N o

40 km

ro /. ) \tratiorsnhir occurrence of LDP 977-2

Newcastle

LDP ffi77-2

'

Lusk

Fiat

\rr,"

Lance Point Bar/ Meandering Channel Sands

Kraig Derstler and John M. Meyers

PRELIMINARY ACCOUNT OF THE TYRAN NOSAU RID PETE FROM TH E LANCE FORMATION OF WYOMING Kraig Derstler and John M. Myers

During the 1997 expeditior-r of the Lance Dinosaur Project, Rob Patchus discor,'ered a tvranuosanrid skeleton in the Lar-rce Forrnation of eastern

Introduction

Wyonting. Nicknarred "Pete" to honor both Peter Larson and Rob's late grandfather, the skeleton n,as ercavated in Jr-rl1,and August 1997. The next slrnrmer, Peter l,arson anil several'u'olunteers helped K.D. bulldoze the site in an unsuccessful effort to locate additionai bones. Presentlr,, the fossil, LDP 977-2, is housed at the Universitt'of Neu Orleans, ri'ith some portions on loan to Kansas State University, Nlanhattan, u,here J.NI. is preparir-rg and studving it as part of his gradr-rate research progrant.

The specirnen u'as cliscor'ered in a small br-rtte on the Su'anson Rar-rch in northern Niobrara Counti', WY (Fig. 4.1). The butte n,as remor.'ed in the course of the ercavation but r,r'as a prominent fcature of the local terrane; it lay u'ithin 200 m of an outlook rvhere contemporarv ranchers scan the regior-r for range fires. The precise location is available frorn K.D.

The t,vpe for the Lance Formation in northern Niobrara Countl'and southern Weston Countl is roughlr 710 m 12360 feet) thick (Clenens 1960).'l'he formation dips nearlr' 1u rvest. Unfortunately', u'ith such a srnall angle of dip, it is not possible to clirecth'rneasure the thickness of the l,:rnce (and w'e are not arvare of anr, cornplete cores or useful well logs for thrs pr-rrpose). As a result, it is necessarvto nse geometric constructions of the stratigraphic cohrrnn. Stratigraphic positions must ther-r be expressed as percentages above the base or beloli,the top of the forilation. \\"hen this technique is used, and if n'e assune 720 rn tl-rickness, LDP 977-2 occurs 460 rn (6)%) al>ove the base of the Lance, or 460 m belor.v the top of the forrnation (fig. a.2). At the site, approrimately J m of Lance are exposed. All but the upper 30 cm consist of light bror,r'n, friable, n-rediurn-grained sanclstor-re, with 10-80 cm crossbed sets and scattered pieces of carbonizecl nood. LDP 977-2 occurrecl ir-r the upper 50 crn of this sancl. T'he outcrop u'as capped bv a l0-cm-thick laver of dark bro*'n, nell-cemented, n.reclium- to fine-grained sandstone that had 5-10-cm crossbe ds arranged as clinbing ripples. This sandstor-re bodr,' u'as elongate nortir-soutli and, despite the r.veathering, thinned noticeablv to the east and rr e st. Thc contact betrveen the underlving light-colored sanclstone and the d.rrk one above is obscured

Occurrence

ihe fact that the dark sand u'as concreted and the zone of heavv cement exiended dorvn into the fossiliferous sandstone. The tops of nany of the bones r,vere cemented witl-rin this concreiecl zorre. The bone-bearing sandstone is interpreted as point bar and meandering channel deposits. The hard cap rock is interpreted as a surviving segrnent of a braided stream deposit forrr-red during the dry season on the rnuch larger rneandering charlnel sands. This is not to say that the rocks necessarilv represent a sir-igle wet-drv seasonal cor-rplet. One of us (K.D.) has observed similar concreted, braided-strearn segments thror-rghout the thicker meandering channel sands of the Lance and contemporaneolls Hell Creek deposits of \Vvorning, the Dakotas, and Montana. When thev $'eather out, thev are frequentlv rnisidentified as petrifiecl logs bv nongeologists. Occasionalli', a bit of the original anastomosing pattern of a braided stream is preserved. The outcrop contained too little information to deterrnine u,hether the bones specificallv accumulated on a point bar or came to rest u'ithir-r the channel of the meanderir-is stream. b,v

Description

The exca'n'ation covered roughlv 150 m: (Fig. a.3). The entire set of in situ bones came fron-r the north-central l0 m2. A huge debris field extended from the exposed edge ofthe outcrop and continued for at least 100 n'r into a deep canvon east of the or-rtcrop. Tens of thousar-rcls of bones scraps were

recovered, but onh'a snall percentage rvas osteologicallf identifiable.'l'he bones are sliglitly,' perrnineralized ivith calcite and traces of pvrite, which is tvpical ofbones from the Lance. As shon'n in Figure 4.1, the fossil includes 2 short segrnents of serri-

articulated cervical ancl dorsal vertebrae contair-ring 5 vertebrae each. An llth isolated vertebra was also recovered. T'he outcrop also produced at le:rst I cervical rib, 10 dorsal ribs, and 4 gastralia. In the field, crew memFigure 4.3. Bone map of LDP 977-2. Only the upper portion of the

debris field is shown.

l..!'.."!'^l..,......*

Kraig Derstler and John M. Meyers

bers identified fragn-rents of numerous dorsal ribs and gastralia, at least 2

Figure 4.4. Distribu-

proxirral caudal vertebrae, i distal caudal vertebra, dorsal/cervical r.'ertebrae, the shaft of a l-rind limb long bone, and several heavy pieces of the

tion of bones found

pectoral girdles. No skull elements or teeth r,vere ider-rtified. The distribution of identified bones is shorvn in Figr-rre 4.4. Interestingly, all of the ribs appear to have their ventral ends broken before final burial. 'fhe dorsoventral height of the last cer','ical is 72 cm, whereas the anteroposterior thickness of the second dorsal centrun-r is Il cm. 'l'hese measLlrements are three-fourths the size of those corresponding to FMNH PRZOBI (Sue). Thr-rs, Pete was probabl.v an anirnai 9.4 n (ll feet) long. Until LDP 977-) is prepared, the fossil will be difficult to identify beyond noting that it is alarge tvrannosaurid. The bones cliffer in no significant n'ay from those of defir-ritive specirn ens of Tyrannosdurus rex (e.g., CM 9380, MOR 555, and MOR 980, BHI 3033). As sr-rcl.r, the specimen is tentatively identifiecl asT. rex.

Drawing modified from Derstler (1 994), scaled to an animal with a

LDP 977-7 n as found in a region of the Lance Creek area knorvn to have been examined by several early paleontologi expeditions. Hatcher collected in the region for O. C. Marsh in the late lB00s and for the Carnegre Musenm in the earlv 1900s. Although he did not keep notes on the areas

with

31

ot

Hatcher's niap rFrs.

J.i

-foot length; 80-cm1

tall human for scale.

istorical Consideration H

he prospected dr,rring the initial exploratior-rs of the Lance dinosaur fields, it is possible to reconstruct this infonnation fbr each vear (lBB8-1892) by noting the 1,'ear of collectior-i for each of the ercavation sites he placed on his hand-drawn map (Hatcher et al. 1907). -\lthough these rnaps cannot be compleiely reconciled n'ith nore recent utaps. it is possible to approxi-

mately locate LDP 977-2

Pete (LDP 977-2).

. Fron-r this, Hatcher

69

N

t

ie Cr.

1

891 Greasewood Cr.

DP# 97V{2

1892

I'

Cow Cr.

I

O\ Jil ()l

.l

Ll

t\

- 1890

OI

c0 I

17

I

20 &23

1

889 .sk-3

I {

+Sk-4

5K

$\

I

,u,"'|18

t-v"=

888

E] OI

3_i'

o\

e0{

t) l)

Figure 4.5. Hatcher's Lance fieldwork for Yale Peabody Museum,

reconstructed from museum records by year. Base map modified from an unpublished handdrawn map in Hatcher's

handwriting found in Yale Peabody Museum

files. Shaded polygons oneln<e
nearl1'reached LDP 977-2 during each of his last 2 seasons, I891 and 1892,

but passed slightil'

r,r'est.

In

I895, San'ruel Williston lead an expedition into the f,ar-rce. He brieflr'carnped at Hatcher's 1890 canpsite and collecting 2 miles furtl-rer north (Clemens 1963). Williston reportedh trar,'elecl nuch farther north rvhile prospecting, but it n'ould be ar-r exaggeration to claim tl-rat Wiliiston barelv missed LDP 97i-2. Hatcher returned to the Lance in I900 to collect for the Carnegie Museurn of Natural Historl (Clenrens I963). Hc limitecl his u,ork to Marcus Dra$r, as shorin in Figure -1.6. This time, he barelv n-rissed

LDP

9 t-7-2

froni

tl-re sorrthn,est.

In 1900, Barnum Brou,r-r, r,r,ho t'as on the Williston trip, also r,entured into ihe Lance Formation, collecting for the Arrerican N{useum of Natural Historl, (Clenens 1963). He prospectecl along Alkali and Ser.en \Iiles Creeks. Although there is no evidencc that he got closer than 15 krn (9 mile$ to the northeast of LDP 977-2,it is n,orth noting that Bron,n did collect the tr,'pe specime n lor Dynamosaurus irnperiosus along Ser.'en N,Iiies Creek at this tirre (see N. L. Larson this r,'oltrrre). By piecing together information from rnuseunr labels and sketcin'published accounts (e.g., Sternberg 1990, 1991), it is possible to reconstruct the area prospected by'the Sternberg famil1' during the 3 r'ears tl-rat thei' worked in the Lance, 1908 through 1910. This information is presented in Figure 4.7. Thev r'vorked further north and n'e st. 'l'her, too alnost venturcd inio the vicinity of LDP 977-2.

Kraig Derstler and John

M

Meyers

t

Ha2

N

Doeqie Cr. y,

I

i

-

.11 "

-*

zo Greasewood

97 .2

Cow Cr.

d,{

o1 L . ?,1

Cr.

- 1890

o3

t7

*41

r20 & 23

,25

.sk-3 .sk-4

o\:

.29

"r-t'5:oq/,/ V// ./

.8. Qu.

Op.2

.Qu-

' .2

1

'10

*28

'o

-/ Figure 4.6. Hatcher's Lance fieldwork for Carnegie Museum of Natural History in 7900. Map as in Figure 4.5. Figure 4.7. Sternberg family fieldwork, combining the years 7908 through 1910. Base map modified from BLM Lance Creek Surface Management Map, 1:100,000 scale, 1991 edition.

LDP #977-2 F--------ldrm------------

71

Figure 4.8. Photograph of LDP 977-1 outcrop

Althor-rgh other paleontologists passed near l,DP 977-2 betrveen l9l0 and 1997, u'e are onlv arvare of one other near miss. In the late I940s, a field partv frorn the Unir,ersitr,of \\'r,'oming camped roughlv half a mile to the north-northeast lvhile thev excar.'ated an aclult Edmrn'Ltosaurus annectens on another nearbl, ranch (Leonard Zerbst, personal commr-rnication to K.D. 1995). 'l'here is no recorcl of an'u' prospecting bv this crew. Naturallv tliere are i.,arious sollrces of uncertaintl,'in the places reached b".each erpedition. Withir-r these bounds, it appears that Hatcher, Williston, Brolr'n, and the Sternbergs approached close to the location of LDP 977-2 u,ithor:t actuallv reaching it. It seems likely that an,v fossil prospector in the area lr'otrld har,e searched the precise spot where LDP 977-2 lar,. As rnentioned above, the discoverv butte ri'as a proninent part of the local landscape (Fig. a.B) and it lat' n'ithin a felr' hundrecl rneters of the best lookout in tl-re area. It is an easv spot to reach, so the site rvould have been irresistible to an1'one searcl-ring for dinosaurs. \\'e do not have any d11..1 information on the amount of tirne that LDP 97 i--2 rvas exposed to erosion. Horvever, the size of the debris field suggests that the skeleton originallv cor-rtained manv intact bones and that it u'eathcred for a considerable period of time. Perhaps n.rore importantlr,', comparison betu.'een photographs of nearbv Lance outcrops taken b1.' Ler i Sternberg in 1908 (Sternberg 1990) and the rnodern terrane shou'that

and the western skyline before excavation in July 7997.

hard sandstone caprocks and the softer sar-rds imrnecliateir,'r,rnderlying har,'e changed little in 95 r'ears. This strongir,'suggests that the similar caprock

72

Kraig Derstler and John M. Meyers

and softer sands associated u ith LDP 977-2 have existecl for n.ell or,er a centurl'. In sirort, tl-re skeleton u as almost certainlv erposecl n hen Hatcher, Brolvn, and tl-re Sternbergs explored the Lance. \Ve find it fascinating to inragine how the l-ristorv of Tyrannosaurus rax research night hale differed if Hatcher had provided N,Iarsh (or hrs successors) r'r,ith a good skeleton in the earlr'1890s, or if he had done the same for Carnegie's r-nuseum in 1900 (r,'ears before thei' purchased one frorn AN{NH), or if the Sternbergs had been able to sell ar-rother skeleton to Osborn in 1908.

\\'e thank Rob Patchus,

n4ro discovered the fossil, and the other nembers

Acknowledgments

of the 1997 Lance Dinosaur Expedition: Ron Francis, Marcus Eriksen, and Joev Masters. We also thank Stanlev and Gloria Su,anson, Rol'Rassbach, and the tor.vn of Neu,'castle, \VY. \\'e gratefulll, acknorvledge tl-re assistance of Peter L:rrson and his r.'olnnteers, ilfio helpecl bulldoze the overbr-rrden at the site in 1998. Finallr', Larrv and foy'ce 'fuss, Winifred, \,'l'f, gracioush'hostecl us n{-rile r','e prepared t}iis chapter in ihe afterrrath of Hurricane Katrina.

Clenens, \\1 A. 1960. Stratigraphv of the tr. pe Lance Forrnation. Report of the XXI Internationdl Ceological Congress (Norden), PartY (Proceedings of Section 3 I h e C r e t ac e o u s -Te r t i ar t, B o ut d a n) : r- -I3 -" 1963. Fossil mar-nmals of the tvpe Lance Formation, Wvoming. Part I. Introduction and nultituberculata. Llniyersitt of California Publications irt -. Ceological Sciences 48: l-105. Derstler, K. i994. DinosaLrrs of the L:rnce Fbrmation in eastern \Vr,oming. P 127-\46 in Nelson, G. E. (ed.). Fortt,-fotLrth Artnual Field Conference Cuideboofr. \\'vomin g Geological Association, Casper. Hatcher, J. 8., N,{arsh. O. C., and t,ull, R. S. 1907. Tlrc Ceratopsia. Unitecl States Geological Sun'er, Nlonograph 49. Sternberg, C. H. 1990. The Lilb of a Fossil Hunter. 1908. Indiana Universitv

References Cited

.

Press, hrdianapolis.

-

i991. Hunting Dinosaurs in tlrc Badlands of the Red Deer Riter, Alberta, Canada. l9lZ. Ne\\'est Press. Edrnonton. Alberta.

Preliminary Accor,tL

of the Tyrannosaurid Pete 73

Wolf Point t--l

.,

{qvet

N

(D uon-ego

1

r ,

Jordan

Circle

20 Miles

Figure 5.1. Location map for MOR 980 (Peck's Rex)

Figure 5.2. Stratigraphic section. (Left) Measured section (information from Rigby et al. 2001). (Right) Measured section within the MOR 980 quarry.

"Duane Clay"

- overbank

@

Hell Creek

sideritic Sano

./ -/'- bonebed

Formation

t/

basal

"Rex Sand"

- oxoow

silt"BBQ 5and"

-

seasonal

meandering/ braided channel

Kraig Derstler and John M. Meyers

TAPHONOMY OF THE TYRANNOSAU RUS REX PECK'S REX FROM THE HELL CREEK FORMATION OF MONTANA Kraig Derstler and John M. Myers

During summer

1997, rvhile excar,'ating a hadrosaur skeleton frorr tlie HelI Creek Formation in McCone Count1,, N4! a field creu,'led bv Keith Rigby discovered the clisarticr-riated remair-rs of a large tvrannosaurid. Occurrirrg

Introduction

near the eastern shore of l,ake Fort Peck, tl-ris theropod quickly became known as Peck's Rex. (The name is traden-rarked bv Fort Peck Paleontologv Inc., Fort Peck, NI'l'.) That autumn, a local resident looted part of the skeleton. Within a ferv',r,eeks, federai agents recovered the looted material and conducted a salr,'age excavatiorl at the site. Resultant hostilities hampered sr-rbsequent piecemeal excavatior-r bv Rigbv ancl associates. It n'as r-rot until 2004 that ive, aidecl bv a field cren', essentialh'completed the excavation. The skeleton is cataloged bv the N!-rseum of the Rockies in Bozemarr, Ml as MOR 980, and it is on loan to Fort Peck Paleontology'lnc. (FPPI), Fort Peck, N,{T. Ntla jor portions of the skeleton have been prepared bv staff and volunteers of FPPI. Damaged portions u'ere restored and the missing elernents reconstmcted bv FPPI in 2001-2004. Sr,rbstar-rtial portions of the fossil remain unprepared, including vertebrae embeclded tiihin concretions and rnost of the bones collected in 2004. Nevertheless, as of June 2004, casts of Peck's Rex had been mounted for exhibit in Fort Peck, M! and Baltimore. N{D. The humeri u'ere later prepared ar-rd studied by us at the Universitv of Nei,v Orleans. Other portions of tl-re skeleton are being studied in different iaboratories, and sorne observations are presented elservhere in thrs volume. Hon'ever, the purpose of this chapter is to consider the events betr,r'een death and final burial for N{OR 980.

The quarry,for MOR 980 is located on federal land adrliinistered b1,'the U.S. Arml'Corp of Engineers, approximatelr' 12 km (20 rniles) sor-rtheast of the Fort Peck Darr in McCor-re Countl', N{T (Fig. 5.}). It lav approximately

I n-rile u'est of State Route 24. Ntlore specific localiti' information is ar,'ailable fron-r us and the staff at F'PPI. The skeleton was collected from the upper part of the upper Maastrichtian Hell Creek Formatior-r, 6 m belou the top Gig. 5.2,left). The quarr! lay imnediatelv abor,e the informallr named BBQ Sand (Rigbv et

Taphonomy

of

Peck's Rex

Occurrence

al. 2001). Details of the stratigrapl-ri', inclucling a con.rposite neasurecl section and a photograph of the localitr,, can be found in this reference. In the rneasured section presented here (Fig. 5.2 right;, Peck's Rer lay near the base of the local Rer Sand, a 0.1-1.8-m-t1-rick sancl and silt unit tl-rat is particularlr,rich in sideritic noclules. In tum, it is or,erlain bi' the Duane Cla1,'. 'fhe base of the Rex Sand is erosional, n'here:rs the upper contact is conforrrable but heavily bioturbated bi'large (ceratopsian?) footprints.

Preservation

In general, the bones are permineralizecl u'ith calcite ancl ninor amonnts of pvrite. A feri' bones are permineralized ri'ith siderite instead of calcite. Betlr,een one-third ar-rd or-reJralf of the bones ii'ere embedded in large (0.3-2.0 m) siltv limestor-re concretions. MOR 980 inch-rdes rvell over 85% of ihe skeleton, rnostlr, disarticr-rlated. Holvever, a string of 11 distal caudal r.'ertebrae lal in articulation near ihe eastern edge of the excar.ation. All of the teeth are rootecl, inclicating tl-rat they fell out of the dentaries, naxillae, ancl premaxillae as the carcass disintegrated. 'fhe fossil ir-rcludes a number of seldorn-seen eleuents-for example, a third inetacarpal, the ftrrcula, and both hurneri (see l,ipkin and Carpenter this volurne). On the otl-rcr l-rar-rd, tl-re right leg is ahnost er-itirelr, n-rissing. Virtualli'all rretatarsals are also rnissing fronr the collection, although tn'o nore lvere obserr"ed in situ (N. Nlurphl, person:rl comrrunications to K.D. 2003 and 2004). None of the bones are distorted bi' cornpaction, although rranv shou' signs of postrrortern rotting ancl prebtrrial breakage . Picces of indil'idual bones are scattered, and the breaks are r-rot crisp. 'fhese obserr.'ations indicate that at least some of the bones u'ere softened, presurrablv br prebr-rrial

rotting, then fell to the lake bottom as indiridual pieces n'ere shed fronr the carcass. Modesi urovernent of the carcass n'ithin the lake. ratirer than water florv, rr-ral,explain the scattering.

Excavation Maps

The quarr,v and bone rnaps generated clurir-rg 2004 br,K.D. are shon'n in Figures 5.1 and 5.4. Individual bones are ker,ed to inventorr,'lists on files lvith K.D. and FPPI. As excavation proceedcd, it becar-ne apparent that tl-rc Rex Sand was deposited on a high-reliefsurface. Several dozen elevations wrere measllred to the nearest centineter on this surface trsing an arbitrarr, base elel'ation. A contour n-iap of this surfacc is sho',1'n as Figure 5.5 using IO-cm contour intervals. Althoug}r information is not available for excavations before 2004, it is ai>parent that N1OR 980 n'as concentrated in the cleepest part of tire oxbon'.

Bone

n-raps

for pre-2004 ercar,atior-ts are sketchv at best. For exanrple,

lr'e are not arvare of any maps that il'ere proclttcecl cluring the 1997 looting or the follon-up salvage excavatiott. In 2002, Bill \Vagner reconstrttctecl a bone map for all of the areas excavated up to tliat tinre using old pl-rotographs, sketch maps, preparation maps for several largc bone-bearing concretions, and personal recollections. He proi'ided K.D. lrith this rnap, Kraig Derstler and John M. Meyers

N

-.,,r/!,j:_l

'"/t..

i

"it4

i

'1,.

'!'rt.

cst lor stradgraphi( sect;on pre2004 backfill

.n

1'-+!d--r-_r 10

meter!

Figure 5.3. The 2004 quarry map. Ltghter gray

-

areas are portions of the exposed Rex Sand that were left in place. P indicates old plaster on the side wall of previous excavation. Edge of

-.,,--iou,11"r_-_.

outcrop and edge of old excavauon are mapped only where observed. The 1997 talus was rden-

tified by Duane Sibley and others present during that year's excava-

tion. The area includes debris produced by all 3 excavations that year. O.iginal

Figure 5.4. Bone map for 2004 excavation of MOR 980. Unexcavated portions of the Rex Sand are /ess than 5 cm thick and judged unlikely to contai n add itional bones.

€xcavation

.,/

t

J

'P !L:r

i-- -!-'_ -

_

I rlr

-"

C i nd i cates bo

n e-

bea ri ng

meston e co ncretio ns; +, survey grid points.

Ii

Taphonomy

of

Peck's Rex

77

Frgure

::

map c:

:':

lontour

case of the Small dots

Rex 5a-J -*^ ql//:): ^t^,^*;^^ I >Ld. :tcvdLrut

/

tlor,s Contour rnterval

is

m fsrhanizod lan< v,.,iihin the Rex Sand are 1A

e

shovtn in solid black.

copies of his original clata, ancl another field rnap produced during the 2003 season. We combined all of this ir-iformation onto a single, pre-2004 bone rnap, but trnfortunatelr,, n,e coulcl not correlate this ll,ith the 2004 nap. This correlation n'as macle possiblc bv uncol'ering about 9 rn of the old excar':rtion to usc as a datum for linkir-rg the old and ne*,maps. Plaster splatters or-r the exhurned excavations also helpecl align tl-re tw,o. The resulting composite map is shon'n in Figure 5.6.

Bratded channel sands

Fossils

from the

Rex Sand within the underlying BBQ Sand are shown as

ray areas. O rientation and flow direction of asymmetrical ri pples i n g

a basal layer of the Rex Sand are shown by bear-

ing symbol attached to a directional arrow. Other information taken from Figures 5.3 and 5.4.

The or1r,prorninent vertebrate fossils in the Rex Sand are Peck's Rex and a partialli' articulated hadrosaur. The l:rtter apparentlr' lav several rneters southn'est of N{oR 980 on a higher part of the sarne depositioral surface. We are not alr,arc, hol.,'ever, of anv maps or other written records for the condition of this hadrosaur or its precise location. A fer,r, bones and tendor-rs from the haclrosaur r'vashed clou'n into the deeper area and *,ere r'ixed rrr with Peck's Rex. Understandabh'. none of the Tj.rarntorarrrrs bones i,vashed upn'ard to commingie lvitl-r tl-re hadrosaur.

Onli' rare

scraps of other anirnals \\'ere recovered fron the Rex Sand. ir-rclude a feu'intemal molcls of nondescript snails, ser,eral sl-tedLeidosuchus teeth, a large shed tootl-r frorn a large drornaeosanrid, some gar and

'fhei

other fish debris, one baer-rid turtle fragment, ancl ror-rndecl fragrnents of Kraig Derstler and .lohn M. Meyers

.,u& tN

Triceratops bones and teeth. Unusuallv; the Rex Sand contained no soft-shel1

turtle ren'iains. Although animal fossils are sparse, plant ren-rair-rs are abundant and often rvell preserveci. 'l'het'include carbonizecl wood, seeds, arnber droplets, and foliage representing a diverse assernblage of dicots, palms, ancl conifers. The Rex Sand cont:rins no obr,ious trace fossiis other than tlie dinosaur tracks at the contact ri'ith the overlving Dnane Clar' (see belou).

The Rex Sand is ir-rterpreted as an oxbor.v lake filling. It occr,rpies a channel tl-rai u as cut into the underlving BBQ Sand, and it grades uprvard into overbank siltv clavstone (dubbed the Dr,rane Cial'). The upper surface of the Rex Sand is pianar and subhorizonal. The thickness of the Rex Sar-rcl corresponds to the depth of tl-re underh,ing depositional surface. Interr-rallr, the Rex Sancl can be dil'ided into I subunits. The lorvest is a several-certimeter-thick series of thin-bedded, r'ellorv-green, siltr.', fine-grained sandstones. Each lai,'er contains asvmmetrical ripples thai indicate current

flo"ving tolvard the south-southeast. 'l'he second unit contains the bones of Peck's Rex. It is a 5-70-cn-r-thick, orange-broun, siltl,sand, n'ith small shale chips, rranr, pieces of carbonized u'ood, otl-rer plant debris, small linestor-re nodules, and occasional p-vritic or sideritic concretions. Some Taphonomy

of

Peck's Rex

Depositional Model Finrrra ( 6 Cnmnncifa

bone map. Pre-2004 maps and information compiled by Bill Wagner. Dashed figures on old beari ng concretions. Note

the articulated stilng of caudal vertebrae near the eastern edge of the map.

79

of the sideritic concretions l-rave a linrestone core.'l'he unit is massive bui poorlv ccrnented. occasional inbricated pebbles inclicate current flo'',tou'ard the south-southeast. Hori'ever, tl-re lack of obvious bone orientation

that the currents rvere r.r'eak. 'fhe uppermost subur-rit is a 60-100crr-tl-rick, mecliun-beclcled orange sand, n'ith rnultiple lavers of sideritic concretions ancl occasiorral large pieces of carbor-rized rvood. It contains fen' other fossils ancl no internal sedirnentar-v structures. Ir-r general, it is bellcr cerrrcrrted tlrrrr tlre bone-bearirrg lar er. 'fhe i:r-rderlving BBQ Sand is a neanclering channel-and-point-bar unit deposited bv a sizable rneandering streant. Reflecting wet-drv seasonalitv in the regior, tlie BBQ Sa'd co.tains a fe*'braided cha'nel sands depositeci cluring tlie dr1' seaso.. These braidecl cha.nels, their internal sr.rggests

crossbeds, and crossbeds rvitl-rin the meandering portions of the BBQ Sand east (Fig. 5.5).

ali inclicate n'atcr flon,ing to the

In contrast, the Rex Sand has consistent indicators sholr'ins that the r,vater) noving to the sor-rth-southeast. N,'Iost reasonablr', this infilling is not related to the deposition of the r:rderlving BBQ Sar-rd. Insteacl, it mar., be tied to the sane stream that cut and oxbon'filled rvith sedirnent (and

then abandoned the oxbow channel. Despite the presence of flo',r' indicators u,ithin the Rex Sand, several pieces of evidence indicate that the oxbon, lr'as generall_v stagnar-rt. The lack of aquatic fauna, particularli'soft-sheil ttrrtles, sr.rggests hosiile aquatic conclitions. Preservation of plar-rt rraterial (particuiarlv abr-rndant, diverse, n'ell-preserved foliage in the base ofthe bone-bearing part ofthe Rex Sand) indicates that a.oxia pre'ertecl the leaves fron deca'ing. Final\,, the siclerite four-rd

tl-rroqghout the Rex Sand strggests that the bottom of the lake was chen.ricallv reclucing, again consistent u'ith the ar-roxia and stagnant water hypotheses. Presun-rablr', orvge'ated *ater and sediment reached the oxboq'episodicallr', durir-rg floods. Betu'een floods, tl-re oxbow rvaters were inhospitable to life. Peck's Rer entered the fossil record through this setting.

Taphonomy

There is presentll' no rneaningful informatioii on the cause of death for NIOR 980 or hori' it entered the Rex Saird oxbor.r,. Hon'ever, it seems reasonable to suggest tl-rat it er-rtcred as a relativelv intact carcass. The high degree ofskeletal cornpleteness, the articulatecl caudals, anci the presence

of the bones th:rt usr,ralh' disappear earh' ir-r postn.rorten l-ristory (nanus, distal caudals, gastralia) all support this hvpothesis. The prepared portions of the skeleton do uot shor'r,anv solid e'ide'rce of postmortem scavenging marks. This is cor-rsistent ri'ith the nearly con-rplete absence of shed teeth of poter-rtial scavengers ir-r the Rex Sand.

'l.he

bor-res are concentrated in the deepest portion of the oxborv rvhere ll'atcr u'as at least 1.5 rr deep (based on the thickness of sedin-rents). The lack of bor-res on the oxbolr, sheif to the n'est indicates that this area r,r,as tor-r shallori for the carcass. Thereforc, the skeleton arrived as a bloated carcass in the dcepest part clf the oxbou, and rvas nnable to move into shallolv areas, or it rias actuallv grourdecl there. In either case, tl-re bones dropped from the carcass to the lake bottom as thev rotted free.

Kraig Derstler and lohn M. Meyers

N'Iani of the bones are broken, n,ith the pieces found rreters apart. Sr-rch

broken edges are ne.,'er sharp, and ther,'usuallr'frave rnatrix injected

into thc trabecr-rlae. Strch bones had to be softer.r before breakage so that thel'simpll'fell apart. In short, manv of the bones u'ere rottecl before thel fell frorn the carcass. Consistent u ith this hvpothesis are hundreds of theropod bone shards scattered throughout the rridclle portion of the Rex Sar-rcl. 'fhese represent bones that rotted to the point u'here ttiev sin-rpl1, disintegrated. The nissing 15% of the skeleton cannot be explained as loss due to rnoclern rveathering because none of the skeleton r,r,as exposed at tl're tinre of discoverv. Ratl-rer, the specimen u,as accidentall,v cliscor,ered in the course of excai.,ation of a hadrosaur skeleton. 'fhere are fel,r' alternatives to explain the missing portions. Perhaps a feil'smaller bones rer-nain in the thin. unexcavated areas of the Rex Sand. Possibl1.a fel'n'are hidden li,ithin the unprepared concretions, or a fen srnallcr bones rrav have rotted cornpleteh' before buriai. Finallv, sorne of tl-ie bones corild hal'e bcen clestroved or othern'ise lost during looting and the salr'age erc:rvation. Whatever the explanation, \\,e are surprised that N{OR 980 is uot more complete because there seems to be no 6b1,is11s 11'21' to clispose of the missing bones.

We thank the staff and volunteers at FPPI and their counterp:irts at the tJ.S. Arrm' Corps of Er-rginee rs, particularh Dtrane Siblcl, l,oLr Tren-rbler', and Bill Wagner. \\''e also ackr-rou,ledge the erceptior-ral field assistance of Douglas and Arcl'r Var-r Belle., Dorv Tr-rrnipseed, Teresa Logudice , Steven Luton, Dana Hensler,, and Ruth Ebert. Bob Richter arranged for and dclir. ered :r great deal of field equipment. Nat \{urphv and Bill Wagner provicled infonnation on the occurrence and historl of N,IOR 980. Peter I-arson \\:as an enclless sorlrce of inforrnation ancl enthusiasm concerning'I't-ran-

Acknowledgments

nos(ilfius rer. Finalli, Larrv and Jovce'l-uss, \\/ir-rifred, N{'l , hosted us u'hile preparing this cl-rapter in the extencled aftern-rath of Hurricar-re Katrina.

Rigbv, j. K., l,inford, C. B., and Rigbv, j. K., Jr. 2001. Geologr,of the McRae Springs Quaclrangle, NIcCone Countr', northeastern N{ontana. Geologl, Studies, Brigham Young Unirersity 16: l5-91.

Taphonomy of Peck's

Reference Cited

Rex

81

Fiarra A 1 RA/lP

P20A2.4.1 (Jane) on dis-,t;

tt f ha Rt trnaa A,4t t:c n nf l\lzft trzl LJictnrtt ll -^ ^ 'ztarr'l

Michael

D

Henderson and William H. Harilson

TAPHONOMY AND ENVIRONMENT OF DEPOSITION OF A JUVENILE TYRANNOSAURID SKELETON FROM THE HELL CREEK FORMATION (LATEST MAASTRTCHTTAN) OF SOUTH EASTERN

MONTANA Michael D. Henderson and William H. Harrison

Extensir,'e outcrops of the Hell Creek Forniation (uppermost Maastrichtian) occur in eastern N{or-itana. Tl-re formation is r.videlv regarded as har.

ing been deposited in a low'lar-rd flr,rviolacustrine sl'stem; these sections consist of a stacked series of fining-uprvard seclimentarr,seqllences forn-red by cl-ranneis rneandering across a lowland floodplain (Kirk fohnson, personal comrnunication). The soft texture of the Hell Creek strata, conbined with the sporadic rainfall in the nortl-rern Great Plains, has resulted in the developrnent of extensive bacllands throughor,rt its outcrop area. These badlands contain an abundant and diverse fossil flora and fauna, including clinosaurs.

In 2001, an expeditior-r frorr the Btrrpee Nllnseum of Natural History, with perrnission from the Br,rrear-r of Land Management (BLM) to survey, for vertebrate fossils, discoi,'ered several foot and lou'er limb elenents of a theropod dinosaur lveathering from an exposure of the Hell Creek Formation in Carter Cotrnt\,, N'IT. After initial evaluation, the site was u'interized and an application made to the BLM to open a quarry the follor.ving year. In the summer of 2002, a field creu' returned to excavate tl-re specimen. During the course of the excavation, a sizable quarry i.r,as created, which yielded rrajor portions of the skeleton of a tvrannosaur (BN4R P2002.4.1), nickr-iamed fane, approximatell'7 n'r in length (Fig 6.1). In addition to Jane, manv associated plant, invertebrate, and vertebrate fossils rvere recovered from the quarrv.

Lack of fusion of the r-reurai arches to their respective centra in the vertebral column indicates that Iane is a iuvenile animal. Examir-ration of histoiogical sections from a rib, fibula, ancl metatarsal indicates that at death, fane l1 years old and stillin a phase of rapid gror,vth (G. Erick"vas son, personal comrnunication 2003). Recovered skull bones and teeth of fane (BMR P2002.4.1) bear a close resemblance to those of CN{NH 7541, a controversial tr''rannosaurid skull that has been interpreted as belonging to eitlrer a juveniie Tyrannosaurus rex (Carr 1999; Carr and Williamson 2004) or a separate taxon, Nanotyrannus lancensis (Bakker et al. 19BB;

J

u ve n

iI

e

Ty ra n

n osa u r i d Ske/eton

Introduction

Cnrrie 2003a,20003b; Cr-rrrie et al. 2003). Research is currentlr'ongoing into tiie s1'stematic position of both specimens. h-r spite of manv taxa of dinosaurs knon'n fiom the Hcll Creek Formation, most finds consist of isolated bones (Pearson et al. 2002). 'l'he discor. err.'of a substantial portion of a jur,er-rile tvrannosauricl skeleton in the formation is so unusual that the circumstances of its burial and preserr,ation nerit careful ar-ral1'sis so that like environrnents can be erplorecl.

Stratigraphy

Extensive exposrlres of the Hell Creek Formation occur in southeastern \Videll' regarded as a prograding, clastic ri,edge associated n,ith the retreat of the \\'estern Interior Sea, the Hell Creek prinrarilr corrsists of poorll'cemented channel ancl crer.'asse splar,'sandstones, overbank rrrrdstones and siltstones, paleosols, carbonaceous clavstoncs, and thin and N,'Iontana.

sparse lignite becls deposited dr-rring the iast l'ears of the Cretaceor-rs Periocl

':,,e 5.2. Jane Quarry ' :^: re/i Creek Forma: r- ,iesi l\/laastrichtian) ' 'a.:n'lvestern carter . ?:-^ty,

MT.

(Nlurphv et al. 2002; fohnson this i'olunre). Near its tvpe section in Garfield Countr', north-central N'{ontana, the Hell Creek Forrnatiolr is I70 m thick (lohnsor-r et al. 2002). Its thickncss in soutlieastern N{ontar-ra is estir-r-ratecl to be 150 n; hon,ever, no conrplete sections of tl-re forrnation are erposecl. 'l'he nearest complete scctions are in south',r'estern North Dakota (aboLrt 100 km frorn the qtrarrrJ, n'here the formation is approrimatell' 100 m thick (N,h,rrphr ct al. 2002). Unfortunatelr', no identifiable marker beds occtrr in thc Hell Creek, r,r'ith the exception of the top and bottor.r-r contacts. Within tl-re formation, there is little lateral continuitr of beds and bentonitic snrface iieatherinq obscures

,t":-.-

rhi

lth

,".

Figure 6.3. Stratigraphic section of the Hell Creek Formation exposed in the lane Quarry, Carter County, MT.

sandy mudstone-contains yertically orienled root casls

f-

rop otquarry sandslone laminaled siltslone

tano$one

siltstone sandslone sillstone cross bedded $andslone laminaled siltstme wilh abundant Prslia conuoata Clayball snglomerale (Tf rannosaur beanng unit) n{as$ive $andstare wilh weak cross beds

bedding (Jol-rnson et al. 2002). Consequentlv, the exact stratigraphic placernent of Jane t,ithin the formation is con-rplicated. Pollen and plant rnegafossils from the fane Quarrv correlate u,itli a stratigraphic level in southll'estern North Dakota that is 28 to 35 m below' the top of the forr rratiorr.

The Jane Qtrarn' is located on the northern side of an elongate eastr,vest-trending ridge in northwestern Carter Countr; M f (Fig. 6.2); the exact localiiy is ar,ailable fiom us. 'fhe tr,rannosallr \\'as discovered r,r'eathering or,rt near the base of the butte. The far.re Quarn'section exposes a fining-upward sequence of clastic sedirnents approximateh'8 m thick (F'ig. 6.3).

At the base of the section is nrassive, poorh' cerrented, clirty; tanbron'n, crossbecided sanclstore. Its total thickness is unknorvn because it is inconpletelr'exposed. Abundant ivood and coniferous and deciduous leaf impressions are present on or near the upper strrface of the sandstone. Decidncrus leaves recove recl fron-r this unit are identified as belonging to Dryophyllum nLblalcatum and "l'ltls" stantoni. The onlv vertebrate fossil encountered in the ur-rit u'as a single midseries cervical vertebrae of a large azhdarchid pterosaur (Henclerson and Peterson ir-r press). A clav-ball conglomerate cornposed of poorlv sorted sand, silt, ar-rcl rounded greenish-colored clar,clasts overlies the sandstone (Fig. 6.4). This unit is lentictrlar, shoi,ving rapid lateral variation ir-r thickness (12-40 cm). The tvrannosaur skeleton u'as discovered in the lori er part of this conglornerate, at its contact r.iith the ur-rclerl_ving s:rnclstone. Diageneticallv proL

-. ?nite Tyrannosaurid Skeleton

B5

: o-.e

6 4. Thin section

o' ine clay-ball conglomo,- L|dt lul/Lol//gu = +,,--^^^--,,t 11ir Lyt dtu tv)qur jQVf ^^;/^ ( B l\4

R P2002.4.1 ).

(t/c /-^^ Jdt tc

Arrows

indicate siderite and a clay ball. Scale bar = 1 cm.

cluced siderite nodules occur n'ithir-r the conglomerate and partly'encased several bones of B\"IR P2002.4.1. Plant fossils recovered frorn this unit include n'ood and bark irrpressions, conifer cones and ueeclies, and numerous srnall, roturd to oval seeds, preserved as internal casts. In addition, an abunclant, cliverse, :rnd r,r'e11-preserved palynoflora occurs in siderite noduies and clai'balls ri'itlrin the conglor-r-rerate. To clate, 5l genera of pollen, spores? and cr,sts hai'e been recor,ered. These indicate the presence of a diverse flora of flori'ering plants, conifers, ferns, c1'cads, and pahns. Poller-r of Cunnera, a herbaccous plant, is especiallv common. Recovered poller-r and spores are tvpical ol the Aquilapollenites pall'nofloral province, rvhich is found in Upper Cretaceous rocks from rvestern North America westward into r-rorihe astern China. hn'ertebrates are representecl b1'poorly preserved inten'ial casts of unionid bivalr,es (2 species) and high-spired gastropods (l species). Remains of r,ertebrates (clinosatrrs, lizards, freshwater fish, croco-

dilians, champsosaurs, turtles) are common and represented bv disarticulated skeletal elernents randornh,distribr-rted lvithin the r-rnit. Preserv:rtion of these bones and teeih range from pristine to significantll, won-r. A 2- to 4-cnr-thick lal'er of siderite caps the conglomerate. Above tl-rc siclcrite cap is a siltstone. The basal l0 to 35 cm of the siltstor-re is finelv larninated ancl contains extremel,v abundant fossils of aquatic monocots, prirrcipallr,a kind of u'ater lettuce, Pistia corrugafrz, many preservecl as u'hole plants (F ig. 6.5). A seconcl 2- to 4-cn-r stratum of siderite caps the Plstiabearing lavers. Higher in the unit, sporadic sandstone lenses (up to 1.5 rn thick) occrrr. Crossbeciclir-rg u.'ithin the sand units indicates water floiv from

Michael D. Henderson and William H. Harrison

sorltli to north.'fhe top 0.5 nr of the qLlarrv is sandl siitstone, ri,hich is not laminated, :utcl iontains verticalh' oriented root casts.

Tl-rc Jane Quarrv section appears to be a tvpical floodplain seqllence. We interpret the nrassive, crossbeddecl sandstone on lvhich the tlrannosaur lal as

point bar sancl. The clar.ball conglomerate that contained the juvenile t1. r:rnnosallr records a nuclflot'from a flood event, or a bank collapse. Abor,e fane, the lan-rinated siltstone containing reecls ancl Pisfla inclicate a strear-rr avuision ancl tfre strbsequeirt do'elopnent of an oxboli'lake on the site, lvhile

Environment of Deposition

:r

sandstone lenses higher in tl-ie section are thought to have been prodr-rced bv

rundern'ater dunes nrigrating througfr the lake during times of high w'ater n'hen the abandonecl channel uas ternporarilr,reconnected to the rir,er svs-

of

terr. Verticallr oriented root casts present at the top of the cprarrf indicate

Figure 6.5. Leaves

er,entuallr siltcd up and vegetation w'as established. Fossils of plants and animals associated n'ith Janc (BN,IR P2002.4.1) corresponcl closelt'u'ith those collected in association w'ith a TlrrunrlosdLLrus rex (Peck's Rex) fron-r the upper Hell Cre ek Formation of N,lcCone Countl; NIT

laminated siltstones above the tyrannosaurbearing unit.

tl-rat the lake

(Derstler and N'lvers this a'cl aroiher T rex (knou n as Scottr) fro.r 'ol'rne), the contemporaneoLls Ftenchrnar-r Fbrnration of southw'estern Saskatcher,al, Canada ('lbkarlli and Brl'ant 2004). The eni'ironment of cleposition of all these specimens inclicates burial took place on a \\,arm, net, lor,r,land floodplain.

All t'u.rannosarir skele tal elcments recovereci fron the Jane Quarrv are consis- Taphonomy tent rvith deri'ation from a single indi'iclual. 'l-he 1-15 bones, representirrg approxirrratel

"'57%

of the skeleton, ilere collecte d trom

i L',, e rt

i

I

a

e

4 m: area (Fig. 6.6).

Tyra n nosa u rid S keleton

Pis-

tia corrugata from the

q12

\\

-n ,-7'

/c>

ri

in\

0$

s

Ag

Figure 6.6. Quarry map showing distribution of skeletal elements of BMR

P2002.4.1 (Jane). Dotted lines indicate field jackets. Sca/e bar = 1 m.

'fl-re ty'rannosaur 1a1'on its rigl-rt side u'hen buried. Portions of the right foot remained in articr-rlation. Skull bones r,vere disarticulated but concentrated in a lin-rited area over the hips. A segrnent of 16 proxirnal caudal vertebrae, rvith their associated hernal arches, u'as found arcing over the back.'l'his drs-

tribution of bones ir-idicates that after death, shrinkage of rntrscle

s ar-rcl

liga-

rnents along tl-re vertebral column contortecl tl-re carcass into the classic dinosaur-avian death pose. Loose teeth from the right dentary'u'ere found north

of it in a pattern consistent with rnovement b."' u'ater or nrud from south to nortl'r. Manr,of fane's ribs and presacral vertebrae n'ere scattered or rtissing. This could be the result of movement bi, lr'ater or mucl, bloating then bursting of the carcass, or scavengir-rg of the carcass. The right hurnerus n'as found about a rreter from the main bone concentr:rtion, ttpstream from inferred paleocurrent direction and in direct contact with a shed tvrannosatir tooth. The context suggests scar,'enging, but the cornpleteness of the skeleton and concentration of bones indicate scavenging rvas not extensive . No tooth rrarks t'ere observecl on oresen'ed bones. BB

Michael D. Henderson and William H. Harrison

The bone preseru'ation of Jane is excellent, u,ith no signs of postrnortern weatherir-rg. 'l'l-ris ir-rdicates that tl-re skeleton ll,as not erposed on the point bar for an exter-rded period of tine. Rapid burial of fane's skeleton b1' a mudflow appears to be the kel' event responsible for its completeness. The finelv laminated siltstones of the orbon' lake deposited on top of the remains pior.'ided furtl-rer protectior-r fror-n d isturbance.

'fhe seqtrence of events leading to burial

1.

2. 3.

4.

5.

6.

ma-v be

surnmarized as follorvs:

Summary

A juvenile tvrannosaur died. At the time of death, or shortlr thereafter, its bodv can're to rest on the point bar of a cl-rannel on a forested, lou'land fl ooclplain. Shrinking rnuscles and ligarnents contorted the tvrannosaur s corpse into the classic dinosaur-avian death pose concurrent n ith, or soolr after, n-rinor scavenging of the corpse occllrred. As decav proceeded, disarticr-rlation of the skeleton reached an advanced stage. Ligaments rerr-iaining aiong the hips, base of the tail, arrd feet kept these eleurents in place. Burial ri'as accornplisfred bv a viscous mudflou'composed of poorl,v sorted sand, silt, and clal'balls. Entrained in these sediments u,ere pieces of r,','ood, seeds, leai.'es, and a varietv of .n'ertebrate bones ar-id teeth. Possiblv, burial r',,as related to a cutbank failure triggered by a flood event. Sorre skeletal elements rvere mor,ed by tl-re mudflolv. After depositior-r, diager-retic siderite nodr-rles forn.red around some of tl-re clinosaur's bones and in tl-re conglornerate. The meancler channel r.r'as abandoned and becarne a deep oxborv lake. Under qr-riet water conditions, aquatic plants flourished and larninated silts n'ere deposited.

Peter Larson (Black

Hills Institute) generouslv provided advice and assistance Jol-rr-rsor-r (Denver Museum of Natr-rre & Science) r'isitecl the tvrannosaur qllarrv site and provided assistance in inierpreting tl-re strata exposed there and helped identifi.,plant remains. Doug Nichols (USGS Denver) provided assistance in identifying the palvnoflora associated u'ith the tvrannosaur. Reed Scherer and f . N{ichael Parrish (Northerr-r Illinois Universitr,) read ancl comrnented on a draft of this chapier. John Warnock (Nortl-rern Illinois University) prepared the stratigraphic column

in collecting the tyrannosaur. Kirk

and Molll'Holman (Burpee Museum) produced the skeietal drarving of Jane. A number of staff and volunteers frorn Burpee N{useum assisted ir-r the excavation ancl preparation of Jane's skeleton, including: Melissa Birks, Dave

Carlson, Ler,l Crampton, foseph De La Morte, Shannon Farley-Maconaghli Chris Garnhart, Jill and Richard Hertzing, Lisa Johnson, Jim Keller, Cl-rrissy \'{ajero',visz, N{irian-r Michaelis, Deborah Nloar-rro, Brian Ostberg, Holli Pahner, )oseph E. Peterson, Sheila, Richard, and \anci,Ran'lings, Scott Santoyo, N'lelissa Sciirock, Ernie and Sue Srnith, \like Spiachello, Mindy Thornpson, Katie Tremaine, Carol and Hazen Tirck. and Scott Wiiliarns. .

,.-'

te Tyrannosaurid Skeleton

Acknowledgments

References Cited

\\rillians, \1.. and Currie,

P. 1988. Nanotlrarirus. zr ne\\ gqnu\ of the latest Cretarceorrs of N'lontan:r. Huteria I: l-10. Carr, T. D. 1999. Craniofacial ontogenv in'l\'rannosauridac (Dinosauria, Coelurosarrrial. lourrnl of Yertebrttte Pttleontoktgv 19: '197-520. Carr,'l'. D., and Williamson, T. E. 200'+. Dir,ersitv of late \iaastriclrtian'1\'rannosauridae (Dinosaurra: Theropocla) fror-n uestern North Anrerica. loological lounnl oi tlrc Lintrcan Societt 112: 4 t-9-573 Currie, P. 2003a. Allonretric grouth in tvrannosaurids (Dinosauria: '1'heropoda) frorrr the lJpper Cretaceous of \orth Arlerica and r\sia. Oarnditut lotu'ncLl of Earth Sciertce 40: 651-665. 2003b Cranial anatonn.of tlrannosauricl clinosaurs fronr the late Cretaceotrs Alberta, Canacla. Acta Palaecnftologica Polonica |E: l()1-726. -. Cr.rrrie, P., Hurunr, J. I{., and Sabath, K. 2003. Skrrll strLrcture :rnd clolutiou irr tvrarrnosaurid d inosau rs. Acta Pal ae ontolo gic a P olo ic a 4E : 22i -23 1. Henclerson, NI. D., and Peterson. J. Ir. hr press. -,\n Azhdarchicl Pterosaur cerlical vertel;ra from the Hell Creek F'orr-nation (Latest \Iaastrichtian) of southeasterrr Nlontana. I ounlal oi \re rtebrate Pal e ontol o gt'. Johnson, K. R.. Nichols, D. J., and Hartman, J. H. 2002. llell Creek F'oruration: a 2001 svnthesis. P. 503-510 in Hartrran, J. H., Johnson, K. R., and Nichols, D. J. (eds.t. Tlrc Hell Creek Fornntion and tl'Le Cretttceous-Tertiart Boutdttrt ut the Northern Creat Plains: Art Integrated Continental Record of tlrc F,nd of tlrc Cretaceous. Cleological Societl of America Special Paper 361. N'lurphr', E. C., Hoganson, J. W, and Johnson, K. R. 2002. Lithostratigraphr of the Hell Creek Formation in \orth Dakota. P t03-i]0 in Hartrnan. i. H., Johnson, K. R., and Nichols, D. J. (eds.). The Hell Creek Forntatiort ttnd the CretaceotLsllertiart, Boundart, in the Northern Crettt PIains: i\tt lntegrttted Cctntinental Record of the End oi the Cretaceous. Clcological Societl of Arrerica Special Paper 361. Pearson, D. A.. Scl.raefer, T., Johnson, K. R., Nichols, D. J., ancl llunter, J. P 2002. \'ertebrate biostratigraphr,of the Hell Creek Forrnation in southu,estern North Dakota and northnestern South Dakota. P ;03-510 in Hartmarr. ). FI., Johnson, K. R., and Nichols. D. J. (eds.). The Hell C)reek L'ormatktt and the Cretaceous-Tertiart Boutdart' ht the Northent Creat Plairts: Att hiegrated Continertal Record of the End oi the Cretaceoas. Cleological Societv of America Special Paper 361. Tokartk, T.'l'., and Brvant, II. N. 2004 The fauna from the Tlrrlnnosd.urus rex ercavatiorr, Frenchnran Fornration (Late Nlaastrichtian), Srlslra/c/reu'an. Saskatchwan Ceological Surlel.', Surnm art, of Inyestigalions I : l-1 2.

Bakker, R. T..

--"-

r:orn lr-!5rr11 r\ LdTILLUJLTLUT rl

r

Michael D. Henderson and Wrlliam H. Harrison

Figure 7.1 . Medullary bone in extant laying hen. (A) Gross cross section of femur of actively Iaying hen shows extensive medullary bone formation. New bone is ranr'lamltt arianfad

a

nr'l

much more porous than overl yi ng co rti ca I bone. (B) Low magnification and (C)high magnification of histological section of demineralized bone from laying hen. Chem i ca I d if fere nces be -

tween cortical and medullary bone are indicated by d iff e renti a I respo nse of each bone type to hematoxylin and eosin /a\ )cPdr -+-l^;^^tv. ilt^t \r/t -^^-.- d)Ldtuu

tion of the medullary bone from cortical bone is seen as sectionrng artifae | | aroo m, tlfint trla^+^) dteu

^.+^^-l--+uJteuL/d)()

-"^ d/c

,,;v/)_

ible around bone
blasts align along preexi
tive in deposition of new bone. Abbreviations: CB, cortical bone; MB, med'

tllar,t hnna Fl R anda<-

teal laminar bone; OCL, ^
l;rr tnaa OC

osteoclast, OB, osteoblast. Scales as indicated See color version of this figure in the accompany-

ing CD-ROM.

L%;

92

Mary Higby Schweitzer et al

ONE PRETTY AMAZING T. REX Mary Higby Schweitzer, Jennifer L. Wittmeyer, and John R. Horner

Determining ser in ertinct aninals is difficult because nost features commonlv usccl to assign sex are lost in the process of fossilization. Despite thrs difficultr', manv bonv feattrres of dinosaurs have been interpreted to be ei iclence of senral dimorpliisrn, inclucling degree of robustness in sauropocls

Introduction

and thcir close relatir.'es (\\'eishampel and Chapman 1990; Galton 1997; Ben-

ton et al. 2000), theropods (Carpenter 1990; l,arsor-r 1994; Smith 1998) and protoceratopsids (Tereschenko and Alifanoi'2003); horn core size in ceratopsids (Godfrer, ancl Hohres 1995); or presence or absence of thc first cauclal chevron (Larson and Frev 1992; Larson 1994), to nanlc a fen'. Hou,ever, even if such feattrres conld definitivelv be shovn'n to be products of sexual clifferentiation, it re mains in-rpossible to assign a particular feature unambiguouslr'to a specific sex (e.g., tl-re robust morph being fernale; Carpenter 1990; Larsorr I99'+). At best, assigning sex to a specific morphotvpe of dinosaurs has fiillen lvitl-rin the realrn of speculation. What is neecicd is an unambiguous nreans of assigning a particular sex to rliale and fen.rale rnorphs. One possibilitr,rs il-re iclentification of medullarv bone in dinosaurs. N{cclullarr,'bone is an ephemeral reproductive tissue that is present ir-r living iara ar-rcl that is found excltrsir.eh, in ferrale, actir,eli' reproducirrg birds. This bonv tissue lines the mcclullarr.cavities of thc long bones of extant bircls; it is chernicallv and morphologicallv clistinct from other bone tt.pes. Special characteristics of corrposition ar-rd structrtre contribute to the high netabolic rates of nedr-rllarr.bone. In fact, it is capable of beirrg metabolizcd 10 to 15 times faster than cortical bone (Simkiss i96l; Dacke ct al. 1993), and it ser','es as an easilv nobilized calcium storage tissue for the prodr-rction of calcareous eggshell (Strgii.'an-ra and Kusuhara 2001). Its presence in dinosaurs n'oulcl indicate sex, support phvioger-retic proxirnirr., suggest sl'rared rcproductive phl'siological strategies u'ith extant bircls, and iLrdicate reprocluctive phase at the tin.re of death.

In:rdclition to protection and support of vitai internal organs, bone plavs an inrportant role in calciun n-retabolism in r,'ertebrates, inchrding al1 avian taxa (Nliller and Bou.'man 1981). [,ong bone formation in extant birds procedes n.u-rcl-r the sarre as in other i'ertebrate tara through endochondral ossification of preexisting cartilage rnodels (\Vhiteheacl 2004;'far'k;r et al. 1971). Bone

Comparison of Medullary and Cortical Bone Characteristics

elongation involi,cs periostcal deposition, ancl concurrent endosteal osteoclastrc re sorption at tiie nretaplx'seal region, resulting in or erall maintenance of bole morphologv and thickness cluring longitudinal grou th {Tallor et al. l97l).

One Pretty Amazng T.

rex

93

In both fonnation ancl elongation, bone production invoh.'es 2 phases, n'l-rich reflect the composite nature of bone rnaterial. In the first, the bone-

forrning cells (osteobiasts) secrete organic rnatrix (osteoid) ('la1'lor et al. l97l; McKee et al. 1993). This matrix primarilv consists of the fibror,rs helical protein collagen I ancl the accessor)'collagen V; the noncollagenoris proteins osteocalcin, osteopontin, and osteonectin (Bonucci and Gherardi 1975; N{cKee et al. 1993; Gerster-rfeld et al. 1994; Sr-rgivan-ra and Kasuhura 2001; Wang et al. 2005), and bone sialoprotein (Cerstenfeld et al. 1994; Robey 1996 and references therein); serum proteitis, including hemoglobin and alburrin (NltcKee et al. 1993); and various g1r,'cosaminogll,cans (Bonr-rcci and Gherardi 1975; Dacke et al. 1993; Arias and Fernandez 2001; Wang et al. 2005) . Therefore, cortical and trabecular bone have specific, characteristic, ancl defineable chemical and lnolecular profiles. However, in female birds, a trnique bone t-vpe is forrned as the result of a sllrge in blood estrogen levels at tl're onsct of sexual rnaturitr'(Bonucci and Gherardi 1975; Kr-rott and Bailel' 1999; Dacke et al. 1993; \Vhitehead 2004). N{edullarv bone does not occur naturally in any other taxon (Else\ and Wink 1986; Dacke et al. 1993), and it is present onl1'during tl-re reproductive periocl in all living female birds, filling the rnarrolr' cai,'ities of manv skeletal elements (Wiison and Thorpe l99B; Var-r Neer et al. 2002). It is produced br specialized osteoblasts that lie w'ithin the endosteum, a thin connective trssue layer that lir-res the n'rarrow surfaces of the bones (Van Neer et al. 2002). N4edullary bone exists onlv to offset the effects of bone resorption during sheiling bv serving as an easilv mobilizecl sottrce of calciltm, and it has no direct biomechanical function (Bonucci and Gherardi l9i5; Wilson and Thorp 1998). It is chemicallv and rnorphologically distinct from other bor-re t1'pes. Although medullary bone has been assrtmed to be present in extar-rt paleognaths, it has not been prer"ior-rslv imagecl or studied, and no data exist regarding the morphologv or chemistr,v of this bone tvpe in ratites. Tl-re r-r-rineral phase of both n-redullarv and cortical bone is prirnarill' hl,droxl'apatite (Ca,o(POo)n(OH), ), bui the ratio of mineral to organics is

higher in medullart'bone (Ascenzi et al. 1963; Tavlor et a1. 1971; Dacke et ai. 1993), and n-redullary bone incorporates a higher proportion of calciun carbonate (Pelligrino and Blitz 1970) than other bone tvpes. Medullary bone is not only more highlr, mineralizecl than cortical bone, but also the distribuiion of minerais is different betrveen the 2 bone types. In cortical rneasr-rrably

bone, the rrineral crystals are regularlv distributed at the heacl of the A bancls of collagen molecules (Ta,vlor et al. 1971), but in rnedullary'bone, rnineral distribr-rtior-r ar-rd orientation is much more ranclom, with mineral cr,vstals additionally deposited in intrafibrillar spaces (Ascenzi et al. 1963; Taylor et al. 197l). In additior-r, rnedullarl'bone does not exhibit birefringence because

of the random arrangement of both collagen fibrils and mineral, u'hereas other bor-re types are ar-risotropic in polarized light (N'Iiller and Borvrnan lg8I; Wilson and Thorp 1998). Finallli the mineral crvstals incorporated inio rreclullarv bone are somewhat larger than the microcr,vstalline apatite of other bone ty'pes (Ascenzi et al. 1963), producing a greater crvstallinitr'' index.

The organic phase of rnedtrllarl bone differs significanth' frorn that of cortical and trabectrlar bone. Collagen makes up a greater proportion of the Mary Higby Schweitzer et al.

organic matrix of cortical bone, whereas the percentage of noncollagenous proteins to collagen is far greater ir-i n-redullarv bone, cornprising approximatelv 40% of the total organics (Knott and Bailey 1999). The concentration of .",arious glvclosarninoglycans is greater in medullary tl-ian cortical bone, and it incorporates different anino sugars (Bonucci and Gheraidi 1975). Hexosamine and keratan sr,rlfate are much more prevalent in medullary thar-r cortical bone ('la-vlor et al. 1971; Wang et al. 2005), which incorporates chondroitin sulfate instead. In addition, relatively high concentrations oftartrateresistant acid phosphatase (TRAP), an enzyme involved in digestion of bone (Sugiyama ancl Kusuhara 2001), are found in rnedullary bone. These chernical differences are reflected in the differential response ofthe 2 bone tvpes to various histochernical stains (Fig. 7.1; Tavlor et al. l97l; Sugiyama and Kusuhara 2001; Wang et al. 2005).

Unlike other bone types, rneduliary bone has no biornechar-rical or other supportive function. It exists solell,as a calcium storage tissue that aids in minerai mobilization to the shell gland during la1'(Dacke et al. 1993;Wilson and T'horp l99B; Whitehead 2004). As rnentioned prer,iouslv, n'iedullarv bone formation in birds is triggered by increased levels of both estrogen and androgens that accompany ovulation, activating osteoblasts to begin secretion of osteoid u,hile inhibiting osteoclast activitv (Dacke et al. i993; Whitehead 2004). The formation of medullary bone begins approximatelv I or 2 n'eeks before lav. It is maintained during the full la'",ing q'cle, and it rnay persist up to

I

r'veek

after lay before resorption is complete (Reynolds 2003).

Medtillarv bone osteoclasts in fernale birds are specialized to contain estrogen receptors in their cell menbranes, u'hich, when triggered bv rising repro-

ductive hormones, increases the efficiency of mobilizing stored calciurn (Miller 1981). Although evidence of medullary bone rnav be found in virtuallr,all skeletal elernents of extant birds, it is most abundant in the fernur and tibiotarsus of most birds studied (Revnolds 2003), and, consistent with rts function as a source of rapid calciun mobilization, it is infused rvith abundant vessels and blood sinuses. In fact, up to 40% of the calciurn used in eggsl-reli fornation comes directh'from the resorption of rnedullary bone (Mueller et al. 1969; Dacke et al. 1993). Although it is r-rot known to serve a direct mechanical function, in redr,rcing the resorption of cortical and trabecuiar bone, it may aid in maintaining integritl.and strength of structnraliv important bone (Whitehead 2004), and incleed, ihe presence of n-redullar),bone in long bones oflaving birds has been shou'n to increase fracture resistance of these elements (Fleming et al. 1998). l,ike birds, rnost reptiles, ir-icluding crocodiies and alligators, also produce calcareous eggshell, but apparently do not produce medullarv bone (Elsei' and Wink 1986; Dacke et al. 1993). This may bs because of different rrechanisrns ofshelling (fackson et al. 2002) and overall greater bone density that can offset the calcium drarv without requirir-rg additional bone storage sorlrces. 'fhus, extant nonavian archosaurs undergo bone resorption during lav, but the structural integrity and biornechanical function of tl-rese organisms is apparently not compromised during shelling. One Pretty Amazing f . rex

Function of Medullary Bone

Although nieduiiarl bone iras not been previouslv observed or clcscribed in dinosaurs, it n'as proposecl that reproducing dinosaurs, at least in the theropod lineage most closelr'relatecl to avian clinosattrs, t'ould possess this ephemeral tissue (N{artill et al. 1996; Chinsanr,and Barrett 1997). 'l'1-re failure to obser',,e or identifv these fragile reprodr-rctive tisstrcs in dinosaurs previouslv nav be due to a nurnbe r of taphonomic and/or biological factors, or observational bias. First, n'e clo not irave atn'ri'av of estimating the length of the reproductive cvcle in theropods. The re is a u ide range of reprodtictive strategies among lil'ing birds, and tl-re extent ancl clistribution of r-nedullarl' bone in these tara differ corresponclinglr (Scliraer and Hunter 19B5). If theropods reprocluce seasonallr', ther. n:rt'onlr'possess the tisstre for a rraximurn of a month or less. Second, because of the relativelv tl-rick, clense corter, the need for medullari bone rnal'be less in these animals, so the medullarl' laver mat bc qLute thin. 'fliircl, in ertant birds, tlre tissue is quiie fragile, and separaies easilv frorr the overlvirtg cortex (Fig. 7.1B, C). It mav be that the tissues are iost, either durir-rg fossilization or dr-rring subscquent recoverv ancl preparation. Third, it mav be that n.reclttl-

larl' bone differs sufficientlv fron-r that of extant dcrived birds so th:rt it i: not recognized. A fourth factor rral be the failure to cxatnine bones for its presence becatrse of collection techr.riqttes requiring bor.rc to be conservcd,

and not broken to erpose ir-rterior fragmertts.

Medullary Bone in T. Rex

At the end of field season in 2002, a r,ell-preserled specirlen ofTt'ranrn' sdurLts rex (NIOR Il2>) rvas found as an association of disarticulated elernents. The site u,as located ai the base of the Hell Creek Forrnation (Lancian), about 8 m above the For Hills Sanclstone. Soft, li'ell-sortcd satrclstones derived from an estuarine or fltn'iai setting surrottnded the skeletal clemcnts. Some of the elements evidencecl slight crusbing, but overall preservatior-r rvas ercellent. N,{OR 1125, nicknarned Bob-rex after its discoverer,

Bob Harrnon, is a relativelr sn-rall but fullv adult Tl rex. In comparison n'ith another T rex, FNINH PR2081, u'ith a fernur length of about 111 crn, the femur of N{OR 1125 is onlr'107 cm in length. Bv ttse of lir-res of arrested gron,th, NIOR 1125 r.r'as calculated to bc about 18 r'ears olcl atthe titue of death (Horner and Padian 200'1). The remote region u'here NIOR 1125 r'vas recoverecl hacl no roacls into the site, so a helicopter u'as requirecl to transport field jackets to the \lOR laboratories. Hor,r'ever, the jacket containing tfre fen-rur arrcl other elen'ients n'as too heavv to be airlifted out, and the jacket and bones tliey contained u,ere broken and rejacketed for removal. In the process, rrar-rv interr-ral fragments that u'ere visuallv free of preservative or consolidants r'r'ere coilected for analr,'ses. When these fragrrents n'ere exautined in hartd sample, a bonv tisstte lining the endostcal stirface of the bone could be seen tliat n'as clistinct in texture, appearance, and distribution fror-n other describccl dinosaur bone tvpes. The rlorphological similarit-v of the nerv tissues to avian meclttllan' bone r,vas irnrrediatelv apparent (Schn'eitzer et al. 2005b). Figure 7.2 shon's fresl-r-fracttrre irnages of T\,rannosaurus rex endosteal iissr-res (Fig. 7.2A, B), Mary Higby Schweitzer et al.

Figure 7.2. Fresh fracture

of tibiae of MOR 1125 (A, B), ostrich (C), and emu (D). Morphology and mi-

crostructu re of m ed u I I a ry bone is observed in all cases as distinct from overlyi ng co rtica I bon e. Medullary bone rs /ess organized and more vascular. Large vascular sinuses can be seen in the medullary bone, and in SOme caset large eroston cavities (*) are visible at

cornpared rvith medr,rllarv bone tissues in reproducing ostrich (trig.7.2C) and emu (Fig. 7.2D). The hallmark traits of medullary bone-dense \rascularitv ancl randorn, rvo.,,en bone pattern-are clearly' visible in all samples. Large erosion cavities are visible in all meclullarv tissues (indicated w'ith an asterisk in figures), indicating that calcium mobilization has occurred.

Dernineralization of extant bonl' tissues is commonlv used to rnore clearlv observe microstructural characteristics, such as fibril orientation; and rvhen mineral is remo."'ed, the primarill,'collager-ror-rs protein matrix rs exposed. Conventional w,isdom has held that u,hen fossilized dinosaur bone is subjectecl to the same treatrnent, the bone nould dissolve corlpletely because ito proteinaceous naterial r,vould persist over the course of geological time (Hoss 2000). In orcler to deterrnine characteristics of presun-red nredullarl,'tissues, rve prepared a partial demineralization designed to etch mineral enough to expose r-rnderlf ing patterns. At this point, rve discovered an unexpected ancl nor"el characteristic to this bonr,tissue. As minerals were dissolved from the medullari'bone, the sarnple did not disintegrate, but, sirnilar to extant borre, tissues remained (Schu'eitzer et al. 2005a). Furtherrnore, these dinosaur tissues exhibitecl apparer-rt original flexibilit,r,i comparable to that seen in extant ratites. Hou'ever, these characteristics are not germane to this chapter and r,vill be discussed elsewhere.'fhe retention of a pliable and fibror-is matrix after dernineralization speaks to unusual pr.r"r,,rtio.r in this dinosaur n'raterial ar.rd suggests that perhaps theorized modes of fossilization mar.need to be reevaltrate
rex

the interface between medullary and cortical bone and in the medullary bone itself, indicating some resorption of bone has occurred. ln emu (D), a large elongate erosion

room is infilled with new medullary bone with c h a ra cte r ist i c co r r u g ate d textu re. Abb reviati

o

ns as

in Figure 7.1 . T, trabecular spicule. Scales as indicated. see color version of this figure in the accompanying CD-ROM.

97

Conclusion

The enclosteallt,derir,ed bone tissr,res observed in this specirnen of TyrannosdurrLs rer (N4OR 1125) have all of the n-rorphological characteristics of n-reclullan,bone, a distinctive aviair reproductive tisstte. Although not identical to published accounts of extant neognaths, ihe dinosaur tissues fall r.r'ithin tl.re rar.rge of morphological variation observed in ratites. This bone tissrre is clerii'ecl from the endosteum, is highly'r,'ascular, ar-rd exl-ribits the

Figure 7.3. Demtneralized

random, n'oven bone arrangement consistent with ver,v rapidly deposited bone. In addition, it has been iclentified on the endosteal surfaces ofboth femora ancl one tibia, the only bones exarnined for the presence of this trssr-re. 'l'l.re clistribution is consistent rvitl-r tl-rat seen it-t extant birds and suggests an orgar-rismal, rather than pathological, response. Pathologies of the enclosteum are relativell' rare and localized, and thev are trsuallv accompaniecl bv cortical bone anomalies in the affected regions. No anornalies u,ere observed, either grossl-v or microscopicallv, rn NiOR 1125. In light of the fact that the relationship betrveer-r theropod dinosaurs and birds is robr-rstlv supported (e.g., Cauthier l9B6; Sereno 1997; Holtz 2004), it is rlost parsirnonions to conclude tl-rat this novel tissue seen in N,IOR I125 is medullary'bone, and its presence in theropocls not only adds independent sr-rpport to thc robtrstly'dernonstrated relationship betn'een theropods and birds, but aiso suggests that these organisrns had sirnilar reproductive phl siological strategies. In additior-r, its presence pro-

fragments of medullary bone from emu (A) and MOR 1125 (B). The fibrous, woven pattern of bone matilx is visible in both cases, and the relatively lacy appearance results from penetration of the bone by blood vesse/s. Scales as

indi-

cated. For methods on demineralization, see Schweitzer et al. (2005a), supplemental online information. See color version of this figure in the accompanying CD-ROM.

With careful examir-ration, other, less epl-remeral rnorphological traits nav be ider-rtified in this specirnen that can be appliecl to differentiate r-ionreproducing vicles a means for ur-rarnbiguotis assignment of sex in dinosaurs.

females in this lir-reage.

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100

C alc ifi ed T i ssue

Mary Higby Schweitzer et al

Internati onal 62: 506-5 I ..

tti

t:eue W *, ,ei*

tl:

VARIATION AND SEXUAL DIMORPHISM IN TYRANNOSAURUS REX Peter Larson

The science of paleontologl has often been accusecl of being more art than science. This assessn-re nt sterrs frorn the probler.r-rs e ncounterecl ri'hen dealing n,ith the patrcitl, and incorriplcteness of the fossii rccord. Not the least of the problems confronting paleontologists is the scarcitv of specirnens. To date, '{6 specimens (\. L. Larson this volurne) consistiirg of more than a fer." associated bor-res have been assigned to'I'yrannosaurus rex Osborn (1905, 1906). Although this is a robust representation for ertinct theropods, r.r'hen conrparecl n'ith extaut populations, this nLrnrber seems ertremcll inadequate. Fbr erample, BLrss (1990) reported a 1973 cor-rnt of 14,109 African clepharfis (Loxodonta ttfricana) in the 3840 kmr (1481 rnir) Kabalega Falls National Park in Uganda. On its face, 46 specimens scerrs a palrrv nurrber from q hich to de finc a specie s, lct alone :rtternpt to identifv males ar-rd females. Yet that is eractlr,t'hat this stuclv attenrpts. The use of modern taxonomic nrcthods rnav be used to identifi anomolons morphological characters and to remove qucstionable specinrens fiom a t:rron to u'hich thet,have been urrnaturallr joined (nrorc belon). Taken even further, rrorphometrics, phi'siologr, ar-rd pathologr,can be used to help separate ancl defi rtc scr rr rorpl rotr'pe:. For this studr', J,l specimens attributeci to'l\,rannosatLrus rex, including specimens listed as Ttrrrnnosriurus "x" lncl Nanotr-rannus (considerecl as specirnens ofT. rer br Carr 1999), li'ere examined. In addition, 2 specimens assigned to TarbosatLrtLs bdtdctr, one assigned to Corgosattnrs and another to Albertosauru.s, \\/ere eramined as or-rtgroups. These specirnens are listed in Table 8.1.

In arv pop.l:rtion, indi'idual n'ithin a species n,ill occur. This 'ariation variation is clue to ontogenr', nutrition, genetic variance, p:rthologr; and, of corlrse, sexual climorphisrr-r. Thus, it is inrperative that these factors be excluded n'hcn examining the cluestion: "Have rescarchers inclr-rded specimens w'ithir-r the species T rer, ri ith variation ber,ond that expected n,ithin a living population?" Extant phvlogenetic bracketing tecl-rniques (Witmer 1995) li'ere tlsed to evaluate the characters used in this studi for the purpose of isolating those :rttributable to ir.rtraspecific rariation.

Vanation and Sexual Dimorphsm

Introduction

Figure 8.1 . (Left) Tyran-

"x' (AMNH 5027). (Right) Tyra nnosaurus rex (BHl 3033). nosaurus

Figure 8.2. Medial view of right dentary of the type Tyrannosaurus rex CM 9380. Note the incisiform first dentary tooth. Figure 8.3. Left and ilght first dentary teeth of

Tyrannosaurus rex BHI 3033. (A) Lateralview, (B) Posterior view. Note that both serrations are exposed in the posterior view, creating the typical ty ra n n osa u ri d D -sh a ped cross section.

Variation

Table 8.1. Specimens I lcad in tha (.tt trh,

Tyrannosaurus CM 93BO

cM

rex

Tyrannosaurus

"x"

Nanotyrannus Outgroups

AMNH 5027

BMR P2002.4.1

MOR 008

CMNH 754,1

LACM 23844

SDSM 12047

BHt 6235

LACM 2345

Samson

LACM 28411

1400

Tarbosaurus BHt 6236

ZPAL-MgD-t/4

Gorgosaurus

MOR 009

TCM2001.89.1

MOR 1128

Albertosaurus

MOR 1125

BHt 6234

MOR 555 MOR 980 FMNH PR2OBl BHt 3033 BHt 4100 BHI 4182 BHI 6232 BHt 6231 BHt 6233 BHr 6230

BHt 6242

TCM2001.90.1 RTMP 81.12.1 RTMP 81.6

1

UCMP118742

BMNH R7994 NHN/ R8OO1 USNM V6183

LL.12823

Ontoger-ietic variation rna,v include aspects other tl'ran the ob',,ious increase in size. For example, it mav also include an increase in the nurrber of alveoli, or tooth positions (e.g., Edn'LontoEdurus annectens; personal obsenation). In certain groups (i.e ., namrnals), gron'th to ach,rlthood mav also inciude modi-

fication of tooth n-rorphologl', along with an increase in the number of tooth positions (Romer 1966). Iror manr.,r,'ertebrates, ontogeny' also includes an increase ilr bodv size at a faster rate than for the brain, e1,es, and skull (Locklel' et al. this volr-rrne). Nutritional variation mav rnanifest itself as smaller bodv size ar-id smaller body mass-differences that are not generally cor-rfused witl-r taxonoinic characters. Genetic variation mav be rronitored by' using extant populations as examples (Darrvin 1868). Pathologic specimens shoi,ving eviclence of disease or healed injurl are relativelv easily recognized, and are generall,v not reproducible from specimen to specimen in a form that lr'ould be noted as a taxonomic character. Finally, sexual dirnorphism lvill be discussed in depth near the end ofthis chapter. Peter Larson

More than 25 I'ears ago, Robert Bakker (personal cornmunication) made the case for dil'iding the North American genu,sTttrannosdurus into 2 species, T. rex ancl what he refers to asTyrannosaurus "x" (Fig. E.l). Bakker's reasoning',vas based on a peculiar variation in the anterior dentition of the dentary. The type of Tyrannosaurus rex (AMNHg71. = CM 9lB0) possesses a single incisiform tooth occupf ing the anterior position in the dentar1,. This tooth is morphologically reniiniscent of the teeth of the premaxilla, is D shaped in cross section, and is substantiallr,'smaller tl-ran those directly posterior to it (Figs. 8.2 and 8.3). Bakker also noted thatAMNH 5027 ap-

The Case for TyrannosauraJs

"x"

pears to possess 2 incisors ir-r each dentarv. For lack of specimens, his vier.vs were never published. Paul (1988) and Molnar (1991) have both also con-

sidered the possibilitv of a seconcl species of Tyrannosaurus. A quarter of a ceniurv later, there now' exist at least I5 reasonablv complete Tyrannosaurus skulls. Three of these specin-rens (MOR 008, SDSM 12047, and Samson) share certain characters, including the double lower incisors, with ANINH 5027 (Figs. 8.4 and 8.5). Because tl'rese "incisors" are ei-

ther missing or were restored on all 4 specimens, i,r'ithout cornputed tomographic scans to look at unerupted teeth, the D-shaped morphology of these "incisors" is in question. The apparent differences seem to be best expressed by con-rparing the size of the second dentarl'tooth rvith that of the third, ar-rd because the teetl-r then-rselves r.vere not alu'a)'s available to n-reasure, the length of the second ancl third alveoli were measured and compared. The results of these rreasurements are founcl in Tbble 8.2.

Although all 4 skulis seem short r,hen compared rvith fr,rll-grown ir-rdividuals (i.e., BHI 3033 and FMNH PRZ()BI = BHI 2033), ontogenetic variation mar,'be ruled or-rt becatrse other individuals of approxirnately the same skull length do not share this character. One of the specimer-rs, Sarnson, has a femur (length, 129 cm) of comparable length to Stan (BHI 3033; length, i11 cm), but r,r,hose skull is less tl'ran 80% as long (104 crn). A shorter skull and variation in lorver jaw clentition is unlikeli to be caused bl,differences in nutritior.r. Pathologv mal'be ruled out becar-rse of the lack of ar1' associated n'ranifestation of healed injr-rrl. Genetic variance also seems in-rprobable because no modern correlates exist. A case could be rnade for the differences in the dentition being attributable to sexual din'iorphisn.

Specimen T.

DT2-L

(mm)

DT3-L

(mm) Ratio of DT3 to DT2

rex.

CM 93BO

55

f\40R 555

52

56

1.1

MOR 980

51

51

1.0

BHt 3033

56

60

1.1

BHt 4182

33

2A

1.0

MOR 008

4B

64

1.3

SDSM12047

3s

55

16

33

EA

T.

1.0

Table 8.2. Comparison of Lengths of Second (DT2L) and Third Dentary Tooth or Alveolus (DT3-L)

*

From the holotype.

"x"

Samson

1.6

Variattan and Sexual Dimorphism

105

!qk_*,

R$ \E g E*3

w x

F

gure 8.4. Dorsal view of

the anterior portion of the left dentary of Tyran-

nosaurus rex CM 9380 preserving small first dentary tooth DTl and ls

ra a <aran r-l rl a nf

a rt

t

tooth DT2.

Although there arc moclern exarnples of semal dirriorphism in the canines of some prir-nates (Nlartin et al. 199'1) and in the canines or incisors of ri alrus, elepl-rants, bush pig, ar-rd hippopotan'rus (Lincohr 1994), serual dinrorpl-risrr expressed as differences in clentition ir-r extant tara seems to bc restricted to marrmals. Any dental e\pression of sexual cliurorphism remains ttndocumentecl for crocodilians, extinct tootl-recl birds (ertant plnlogenetrc brackcting), or other ertant reptiles. Can the differcnce in the teeth be attributable to speciation? Although stratigraphic information for the 4 specirnens is r-rr-rai'ailable, tiiere are gooci records available for Ti'rannosaurus rex. BHI 2031 n'as coliected l6 m belon' tl-re Kjl'boundarv in the Hell Creek Formation (the Hell Creek in the area, near Buffalo, SD, is approximatelr' 150 m thick). A second indisputable specinen of ?yran nosdurlLl rex (BHI 4182) ivas collected nearbr', frorn n ithin I0 rn of the base of the fornratiorr, and it represents perhaps the oldest knon'n recorcl of 'li'rannosaurus from Norih America (Kirk Johnson, personal cornrrunication). Geographic distribution is also not a factor, because 'f. rex cooccrlrs u'ith

106

Peter Larson

T

"x."

rt.ii.t

:"1|i.*:

i!l:r:r:

Dentarv and rnaxillan,tooth (alveoli) counts also seem to var)'between the 2 "species." Tl'ris is particularlv evident in the dentarl; lr'ith ll or 14 for 'fyrarLnosourus rex ancl 14

or

15 for

T 'r."

The distribution of all of these

characters, vithTarbosatLrus hataar as an outgroup, are listed in Tbble B.l. A fourth character separating the 2 forrrs is the relatir,e size of the lateral

pneumatic lachrvrnal foranien. Specimens referablc to T 'x" l-rave relatively snraller lateral pneumatic lachri.'rnal for:rrr-rina th:rn those of 'li,rannosaurus rex (Fig.8.6). when me'surecl .nd plottecl as lach^'mal forarnina length's. laclrrl,n-ral length (Fig. E.7),7\'ranrrcsd.urus "x" cl.sters separateli,, frontT. rex

iiiii

Figure 8.5. Dorsal view

of

the anterior portion of the left dentary of Tyran-

nosaurus "x" (Samson) preservi ng sm a I I a lveol i for DTI and DT2 and a large alveolus for the

third dentary tooth DT3.

(as do GorgosaunLs anclNanotyranntts). Ho*e'er, it should be notecl that the size of the lachrv'ral forarnira in Allosaurus is extre'rely and this 'ariable, difference betn'een 'I'. rex a''d T 'i" mar r-rot be statistically'significa't, espe-

cial\, gil en the sample size ( Kenneth

Skull Character

Car penter. p.rro,-r"L .o,-,-,rnunicationl.

Tyrannosaurus Tyrannosaurus Tarbosaurus rex

Lateral lachrymal pneumatic foramina

Small

Maxillary tooth count

11

or

12

Dentary tooth count

13

or

14

Dentary incisor count

1

L3DT/L2DT DT3-L/DT2-L

1.0-'1

1

Very small

Small

12

12

14

or

15

or

Table 8.3. Comparison Skull Characters

13

15

2

1

1.3-1.6

1.2

Var'arion and Sexual Dimorphism

t07

of

Figure 8.6. Lateral view

of the left lachrymals of (A) Tyrannosaurus "x" AMNH 5027 and (B) Tyrannosaurus rex BHI 3033. Note the larger lateral pneumatic foramen on T. rex.

B Are these 4 cranial characters enougl'r to erect a new species? (No significant postcranial characters r.vere noted.) Becanse r,ve are dealing with ar-t extinct group, cloir-rg so at this tirne rnight be premature. Although it is likell tlrat a second North Arnerican Latest Cretaceous species of Tyrannosaurus exisis, all of the specirnens in questions are in need of further preparation that rvill perrnit a more thorough conrparison ri'ith tl-re t1'pe (ANINH 973 =

CM

9380) and other referred specimens. Fortur-iateh', preparation of 2 of the specinrens (SDSM 12047 and Sarnson) is alreadv nnderrva\'. The ultimate disposition of Tyrarutosaurus "x" mav soon be resolied.

ls Nanotyrannus

lancensis a Juvenile Tyrannosaurus rex?

'fl-re genus Nanotrrannus r,vas erectecl bv Bakker et al. (1988) for the ti'pe specirnen (CN{NH 7541\ of Corgosaurus lancensis Gilmore (1946). This specirnen (fig. 8.8) consists of a relatir.,el,v cornplete skull preservecl with

the jau's

ir-r

occlusion, n'ith verl'little distortion and no associated postcra-

Lachrymal Length vs Lachrymal Foramina Length

Figure 8.7. Lachrymal

length vs. lachrymal foramina length.

lTcad2ool

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nial rlaterial. Bakker et al. (i988) argtrecl tlrat certain derived cliaracters,

FinrrraRR

inciuding thc constnrction of the basicranium, the angle of the occipital

men of Nanotyrannus lancensis CMNH 7541 .

condvle, tlrc marillarl'tooth count, the over:r]l tootli morphologi,, tl-ie reiative narron,ness of tire snout,:rncl tl-re erpansion of the tenpor:il region of

the skull cleariv separatecl tl-ris specimen from other tvrannosaur clades (Gorgosaurtts, Albertosaurus, L) aspletosaurus, and Tl,rannosatLrus'). .\lthotrgh the characters discussecl bv Bakker et al. (1988) clearh., separated this specinren from its earlier assignnrent to ()orgosaurus, its distancc fron.r the T\,rannosaurtLs clacle seerned less clefined. Thev both "achieved the highest degree of potential stereoscopv kno\\'n among large theropods,"

and thel agree irr characters, inclucling the orientation of the occipital cor-rd11e (Bakkcr et al. 19EE, p. 25).'l.hev also acldress the question of the skull being that of a jur,enile : "The sutures betn'een the lachrl'n-ral and prefrontal have thoror-rghli.'coalesced inNanotyram?us,

as have

the sutures

beti,veen frontals and prefrontals. . . . Without question, the tvpe of Nano-

tyrannus ll'as fullr.aclult and had reached the urarirnilm size the individual rvould frave attainecl if it had lir ecl longer" (Bakker et al. I988, p. I7). Carpenter (1992, pp. 259, 260) disagreecl \\'ith Bakker et al. (l9BB) when he noted tl-rat "tl-rc coalescence of cranial bones is knoun to be r"ariable in dinosaurs" bringing ulrder suspicion "its Lrsabilitv to 'age"' dinosaurs. Carpenter furtlier noted that "the oval shape of the orbit" rnav rvell

\,ia.,aiion and Sexual Dimorphsm

109

Trrnacnaei-

be a juvenile character. He concluded that Nanof yrdnnus lancensis covld be a jur,'enile T. rer. Carr (1999) expanded this possibility. On the basis of 17 specirnens

referred to Albertosaurus libratus, Carr erected an ontogenetic series of (l-3). From bor-re texture, lack of fusion, shape of the orbit, and overall skull morphologr', Carr placed CMNH 7541 into his stage l, ihe voungest in his ontogenetic series. Carr then declared Nanotl,rannus Iancensis to be a juvenile T),rannosaurus rex.In later argurnents (Carr and Williamson 2004; Carr et al. 2005), this designation lr'as used io establisl-r gror'vth stages

a

grorvth series for

T

rex, establishing a sequence ofchanges

fron the srriall

juvenile LACN'I 28471, follorved b_v the juvenile CMNH 7541 (stage I), through sr-rbadults LACN{ 23845 and AMNH 5027, to the full1'grou'r-r adults LACNI 2)844 and FMNH PR208l (BHI 2013). Although Carr (1999) preser-rted a compelling and thoughtful argurnent, not ali paleontologists agree with his assessment. Currie (2003, p. 223) pointed out that "rnost of the characters used to demonstrate that Nanotyrannus and Tyrannosaurus are synonvmous are also characters of Tarbosaurus andDaspletosdurus." Bakker et al. (l9BB; personal comrnuuicatior-r) noted the discrepancl,' ir-r tooth cor-rnts- l5 maxillary teeth in Nanotyrannus and 1l or I2 ir-r TlrannosarLrus rex-and the lack of tooth recluction ontogeneticallt, in tire maxill:r of anv extant species. The primitive compressed n:rture of l\anotyrannus teeth (Bakker et al. 1988) as conpared u'ith the derived inflated teeth seen in T. rex and evidence of feeding behal'ior differences also argue for the ur-riqr,reness of CNIINH 7541 (Larson I999). Because the groli'th series argnment of Carr is rooted in the assumptior-r tlrat NanotyranntLs is a juvenil e T. rex, rnuch of Carr's concept of ontogenetic change and ontogenetic stages irt T\,rannosaurlts rex is in question (Jorn Humm, personal communication). I agree w'ith Carr and Williamson's (2004) assessment of LACN4 28471 (the so-callecl Jordan theropod)u,ith CN'INH 7541 (the tvpe of Ncnottrannus)), ar-rd u,ith the designation of the subadult LACM 2)845 asTyrannosaurtLs rer. Horvever, I disagree ',i'ith the subadult designation of AMNH 5027, which groups as a full adult r,r'ith TyrannosaurtLs "x" and rvith Nrcnotyrannus as a juvenile T rex. An isolated left lachrvn-ral (BHI 6235) comparable ir-r size and r-norphology to CMNH 7541 u,as found associated n'ith Sue (FNINH PRZOBI) and erroneously identified as a juvenile T. rex (L,arson 1997). It, too, should be referred to l\anotyrannus. Finall,v, the recent cliscoverv of a fourth specimen (BI,lR P2002.4.1) is clearl,v referable toNanotyrannus. Tl-ris specirnen, nicknarned Jane, in addition to many ur-rcnrshecl and w'ell-preserved skull elen-ients with a nearlv conplete der-rtition, also preserves much of the postcranial skeleton. Although this subject is discussed in cletail elsenl-rere (Cr-rrrie 2003; Currie et al. 2003; Larson in press), a list of characters separating Nanotyrannus fron'fyrannosaurus is presei'rted in Table 8.4. For pr,rrposes of comparison as outgroups, those characters are also listed for Tyrannosaurus " x," T arb ct s aur u s, C or go s auru s, a nd Alb e r to s aur u s.

110

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85

Is it possible to recognize sexual dimorphisnr in Tyrannosaurus rex? 'l'he subject of sexual clinrorpl-rism in nonavi:rn iheropods has been eranined bv a nunrber of autl-rors over the vears (e.g., Paul 1988; Colbert 1989, 1990; Raath 1990; Chinsamv 1990; Cat, 20051. 'i'he subject of sexual dinrorphisn"r in TrrannostturtLs rer has surfaced repeatedlr' sir-ice Carper-rter first broached the subject in 1990 (N,Iolnar 1991; Larson ar-rd Frer.' 1992; Larson 1994, 1995,2001; Horner ancl Lesserr 1993; Carpenter and Srnith 2001; Larson and Donnan 2002; Brochu 2003; Molnar 2005). These authors

Sexual Dimorphism

in Tyrannosaurus rex

have also explored the possibilities of identifi'ing, or at ]east separating, the

of iarious theropod species on tl-ie basis of differences in cranial ornamentation (Larson 1994; Nlolnar 2005), pelvic construction (Carpenter 1990; I.arson 1994,1995,2001; Larson and Donnan 2002), erosion ofthe femur to liberate calcitrm for egg production (Chinsaml' 1990), presen,ation of n'redul1ar1. bone (Schu eitzer et al. 2005 ), differences in hei-r'ral arci-r (chevron) morphologr (Larson and lirei 1992; Larson 1994,1995; Erickson et al. 2005), the presence of eggs r.rithin thc pelr,ic arc (Sato et al. 2005), and skeletal n'rorph (i.e., gracile vs. robLrst morphs) (Paul 19BB; Carpenter 1990; Raath 1990; Chinsamr' 1990; Larson and Frev 1992; Larson 1994, 1995, 2001; Larson ard Donnan 2002; Carpenter and Smith 200l). Serual dimorphisrn in ertant animals is il'eil clocumer-rted. We recognize this in mamrnals as the presence of antlers in male cervids; longer and more massive tusks in male elephar-rts, suicls, and ri'alrus; larger horr-rs in male bor.'ids; the presence of canines in rnale eqtrids; and a generalh'larger rnale bod-v size (e.g., N,'{acdonald 1984). This semal size dir-norp}risrn can be quite impressii.'e, reaching as much as a 7:l (3500 kg : 500 kg) ratio of nrale to fenale body rrass in the soutliern elephant seal,Nlirounga leonina (Lindenfors et al. 2002). Interestingll', for nanr, rrarrnals, ihe onh, obvious sexnal clinorphism, ercluding geniialia, is expressed in adult size, r.l'ith males or-rtr.r'eighing fernales (N{acdonald i984). Nlar-rv reptile groups (e.g., crococlilians; Bellairs 1970) seern to follorv thrs mamtaalian pattern of sexual size dimorphism. Hor,r'e'u'er, it is not ain'avs the males u,ho otrtn,eigh the females. In turtles and snakes (Fitch 1981), and even in a fer,r't.narrmal groups like baleen lr'hales (N'Iinasian et al. 1984) ar-rd h'u'er-ias (Estes 1991), sexual size climorphism is expressed br,fenales being larger than males. Species of invertebrates, to offer other exarnples, are often quite sexualll'size dimorphic, u'itl-r the female, almost uithout exception, being the larger. In fact, tl-re n'orld record holder for the rnost sexnallv size-dimorpl-ric anirnal is the blanket octopus, TrernoctoptLs violaceus, r,i,here fernales may or-rtlr,eigh nales b1,'as much as 40,000 to 1 (Norrnan et al. 2002). sexes

Birds, the closest living relatives to non:rvian theropods, are often quite sextralh'dimorphic. 'fhis dinrorphism may be expressed as differences in

coloraiion (the ostrich, Strutlio cameltLs), plurnage (the cornmon peafowl, Payo cristatus), ker:itinous structures (the rl-rinoceros hornbill, Buceros rhinoceros)1, fleshv head ornarnentation (the common tr-rrkei', Meleagris gallopavo), or even inflatable fleshv stnrctures (the greater prairie chicken, Tympanuchus cupido). Unfortunatell', because none of these features is likel1,to be preserved in the fossil record, thev arc not mnch use in recognizing sexi-ral dimorphisrn in extinct theropocls. Serual size dimorphisn, \/at altan and Sexual

Dimorphism

113

hor'vever, is effective in separating rrales from females in some bird species

(Brad [,iveze'"., personal coinmLlnication). Sexual size climorphism mav also prove recognizable in nonar,ian theropods like T'l,rorznosaurus rex. For manv birds, sexual size diurorphisrn is measnrable. It mar-rifests itself as males larger thar-r females in gr-rlls (lngolfsson 1969; Schnell et al. 1985; Bosch 1996), steamer ducks (Livezev and Humphrev l9B4), sparrori's (McCillivra-v and Johnston l9B7), and skimrners and terns (Coulter 19E6; Quinn 1990), among otl-rers. Sexual size climorphisn also occurs n,ith fernales larger than rnales in spotted orvls (Blakeslei'et al. 1990), ospre):s (Schaadt ancl Bird 1993), sandpipers (Sandercock 1998), erurs (Nlalonel,'and Dali'son 1993), and so forth. N{orphometric anair sis, perfonned br, skeletal rleasurerrenrs, l-ras proven effective in separating sex $,hen the clifference in mass is over 67o (Schnell et al. 1985). It has even been possible to separate the sexes ofrrature ir-rdividuals through n-rorphonetric examination (bl using bil1, r,r,ing, and tail

measurenlents) ll,l-ren mass differences betu'een the seres u,as insignificant or even indiscenrible (Winker et al. 1994).

Altliough researchers

har,'e

re

ferred to the presence of robust ancl grac-

ile n-rorphotvpes, N4olnar (2005) points out tl-rat to date, these rnorphotvpes have not been adequatell' quantifiecl, but rather are generallv based on visual assessments. Is it possible to recognize and quantifi'sextral size dir.norplrism, and clearlv classifi.'individual T),rannosaurus specimens as robust or graciie morphs? To answ'er this, I have taken measurements of select elements from 25 specimens of TyrannctsaurLLs rex. Nlleasurerrents rvere also

taken for 2 outgroup specirnens assigr-recl bv this studt' to Nanottrannus lancensis (CN,INH 7511 and BNIR P2002.4.1) and one to Gorgctsdurus sp. (TCM200l.89.l). Even though this studl' consiclers 'Ittrannosaurus 'r" to be tlre sarne genus as T. rex a:nd hence shoulcl be separable in a consistent manner, I of these specimens (AN4NH 5027, Samsor-r, and NIOR 008) also appear as outgroups. Measuremer-rts from element to element and "'aried consisted of lengths, rvidths, heights, and/or circumference, as sho,"vn rn Figr-rre 8.9; the values are found in Tables 8.5 and 8.6. Clustering on graphs is assurned to separate serual size din-rorphs. The results n'ere then compared lr'ith a l'isual ar-ralvsis that dir,ided robust rnorphs frorn gracile. Some elements failed to provided significant results (e.g., dentarr, length vs. tooth rorv length). For other eiernents, there rvas sirrplr'r.rot enough data to ;,ield rneanir-rgful results (e.g., metatarsal II length vs. circurnference, Fig. 8.11; iliurn ler-rgtl-r vs. height, Fig. 8.12; and humerus length r.s. circumference, Fig. 8.13), although visual examination rvas able to separate them, indicating that the human eve can see apparent differer-rces (as in Fig. 8.10). Elements that provided too few' data rnav vet prove useful for quar-rtifiable analvsis rvhen aclditional specirnens are disco'"'ered. Elements that ivere abundant, such as the fen-rur (Fig. 8.la)and hunenrs (Fig. B.l3), vielded clear resuits, w4rich confirn-red their scparation by visual inspectior-r: robtrst plottecl individuals look n.rore robr-rst. Fron.r tlre resr-rlts of the analvsis, 2 morphs of T,rrannosauruls are apparent, a robust and a gr:rcile morph. Neither geograpl-ric r.ror stratigraphic distribution can erplain these differences. Therefore, because both crocodiles anci birds shorl'sexual size clin-rorpl-rism, extant phl'logenetic bracketing tells t1n

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t"2l l-rr<-) (J 1l itr\/ rymar --l ==^l

/

L:chrymal

"

m easu

reme

used in this study.

F"

i \""'* I /( ILr) I

7

)\

-fi{f Humerus

'.J

t

t\+)

] \

/

]J r'

{ i(r"l [J l\, \ IW

l.\

_zl)

Metalarsal

that the rnost parsimonious explanation for the presence of these 2 morphs The formr-rla developed bl'Anderson et al. (1985) was used to estirnate the nass of the robust and graciie morphs frorn femur dianieter. 'l'he rveight estimates (Table 8.7) shot, a maxirnurr n'eight for the gracile rrorphs of 4.0 metric tonnes, il'ith a mean of 3.5 metric tonnes (6 inr,rs

is serual size dirnorphisn-r.

dividuals); :rnd a narimum rveight of 5.6 n-retric tonnes ancl a mean of 4.7 rnetric tonnes for robust n-rorphotl'pes (9 individual$.

Civen that the presence of 2 morphs has been established forTyrarLnosau- Male rus rex, can \\:e cleterrnine tl-re sex of the morphotvpes? Carpenter (1990) suggested that, on the basis of the greater divergence of ischiun (Fig. 8.17), the robtrst forrn u,as femaie. Larsorr and Frev (1992) agreed rvith Carpenter, and thev further suggested that the location ancl morpholog,v

Vartailon and Sexual

Drmorphism

117

of

nt tech n iq u es

or Female

Figure 8.10. Anterior view of right metatarsal tl of (A) gracile (BHt 3033) and (B) robust (TCM 2001.90. ) morphotypes. 1

q9r

!1fi IN

of the first chevron nright also be used to l,ield the samc result. Hon'elcr, this method has proven unreliable (E,ricksoir et al. 2005). Elsewhere, I (Larson 1994, 1995) have suggested that the r.r ider pelvic arch ancl he:rlecl injuries of the proxirrial caudal vertebrae (consistant n'ith injuries potentiallv inflicted bv a mounting male during copulation) n'ere rcstrictecl to robust rnorphotr,pes. I (Larson 2001; l-arson and Donnan 2002) sLrpportecl Carper-rter's (1990) conclusion that robust inclividnals n,ere fernale. But because of the tenuous nature of these conclusions, I liave specr-rlated that one wav to positii'eli' recognize a lemale is to locate medu]larv bone n'ithin the skeleton (Larsoi'r and Donnan 2002). N,{edullarr,bone is onlv deposited riithin the medr.rliarv cavitv in the long bones of feniale birds dtrring ovr-rlation, as an aid to the quick nobilization of calcium for egg Peter Larsan

Metatarsal ll Length vs Circumference 320

Srnsma 300

a Mv!( )f)

280

Tclvgool

90

l!

1IBHI

6230

260

o

2

zoo

l

E

e

MOR 980

Eno

o

6

zoo

a rvevvr.oy.

I

180

160

aBMRPzmz41 140

,180

520

500

ffi

550

580

500

620

Length a cracile I Robust Figure

8.'1

1. Metatarsal ll

Acorg/Nano

length vs. circumference

Figure 8.12. llium length vs. height.

llium Length vs Height 650

600

monrpnzoer

nlll

I

?6??

a

a

550

500

'ILIVIZUUI

w' I !

ouoRggo

450

f

4oo

MORM9

350

r

3@

TCM200I 89 I

250

1BMRP2002a I 2@

700

800

900

1000

l

l00

l?m

13m

1400

Length

a Gracile I Robust L

:' '' ^.

anrl

Gorg/Nano

\ennl Dimornhism

119

lt@

t@0

GSA ,.,r'arr.

't;ii

:

16.

.!i!. ."!,.

il fi CM

IN

I lmm

Figure 8.13. Anterior view of (A) left humerus of

gracile (BHl 6230 and (B) right humerus of robust (FMNH PR2081)

productior-r ('l'aylor 1970; \Velti'and Baptista 1988; Schri'eitzer et al. this volume). Although the absence of nedullarv bor-re is inconclusive (it is not

founcl in males and nonovulating females), its presence rrr-requivocally identifies a fernale.

Medullart'bone has not been docurnented in or,ulating female crocodilians. Although ovulating birds have meclullarv bone. there \\ere no guarantees that ancestral nonal'ian theropods shared this character. What rvould be the chances of finding the fossil of an ovulating female Tyranno-

morphotypes.

sdurus rex, preser"'ing the meclullarv bone, exposing the inside of the med-

ullarv catitr', and recognizing ancl then verifving that the tissue is meduliary bone? LInbelier,abl1,, that is exactll rifiat Schu,eitzer et al. (2005, this 120

Peter Larson

Figure 8.14. Anteilor view of (A) left femur

of

gracile BHI 3033) and (Bt right femur of robust (TCM2001.90.1)

morphotypes.

volunre) dicl. Sclnveitzer et al. have r''erifiecl the presence of rnedr-rllarv bone

rvithirr the fernur of a specimert o{ T|rannos(tLLrus rex bv cornparison n ith medr.rllarv bone extractecl from laling chickens (,CalhLs gallus) and ostriclres (.Struthio can'Lelus). Bv plotting infom-ration fronr the fenrur front rihich tl-rc n-rcclullarr bone 'ni'as found (N,IOR 1125t, it n'as fonncl that the specirnen clustcrs n'ith robust rnorphotr,pes fFig. 8.18), therebr pror.iding independent supporting evidence that the robLrst morphotl,pes are nost

Variailan and Sexual

Drmorphism

121

Table 8.7. Calculated Mass for Tyrannosaurus Specimens and Outgroups, Nanotyrannus and Gorgosaurus

5pecimen

T.

Type

Femur

Femu r

Mass

Mass

Length

Circumference

(ks)

(tonne)

(mm)

(mm)

rex

cM 9380

1200

4726

4.7

0n

3s35

3.5

1260

580

5601

5.6

R

BMNH R7994

fvoR

,4

1128

MOR 1125

B-rex

1150

510

3943

3.9

R

f,/oR 555

Wankel rex

1275

514

4028

4.0

G

1232

483

3399

3.4

MOR 980

Peck's Rex

FMNH PR2O81

5ue

1340

580

560',]

56

R

BHt 3033

Stan

1310

500

3735

3.7

G

BHt 6232

1180

527

4312

4.3

R

BHt 6233

f

BHt 6230 BHt 6242 RTMP 81.12

1

RTMP 8'1 6.1

T.

Morph

il0

515

4049

4.1

R

Wyrex

1'190

494

3614

3.6

C

Henry

1180

512

3985

4.0

R

Huxley

1

200

560

5090

l.

R

Back Beauty

1210

470

31

55

3.2

USNM V6183

990

LL 12823

1

I

425

2397

2.4

200

467

31

00

3.1

C

"x" Samson

Z-rex

1295

560

5090

5.1*

BMR P2002.4.1

Nanotyrannus

720

250

563

0.6

TCM2001.89.1

Gorgosaurus

825

270

695

0.7

A hh,^,,i^+i^^-. nuutcvtoLtut

certainl,v females. We na1, therefore asslrrre that the gracile morphotvpes are males.

tJ.-

G, gracile; R, robust * Mean, 4.1.

'l'his study examined

Conclusion

3'1 specimens that have been assigned b),r'arious autlrors to Tyrannosaurus rex. This list also includecl speciurens ascribecl by' some atrthors to Nanotyrannus lancensis btit svnor-rvnrized by others r,l'ith T

rex.B,v use of shared ar-rd derir,ed characters, these specimens (CN,,{NH 7541, LACM 28471, BMR P2002.4.1, and BHI 6235) may clearly be removecl fronr the clade, thus r,alidating the u'ork of Gihlore (1946) and Bakker et al. (1988). Also of contention is a group of 4 specimens (ANINH 5027, N4OR 008, SDSNI 12047, and Samson) that ha'n'e been referred to as 'fyrarLnosczrirus "r. " Again, b-v use of taxonomic characters, there is ample evidence to remove them from

tlre species rex, but rnaintain thern n ithin the genus Tyrannosaurus. 81' use of morphometric ar-ralysis, gracile and robust morphs are confirmed to be present u,ithin the clade Tyrannosaurus rex. Extant phvloge-

netic bracketing (comparison ri ith lir,ing crocodiles ancl bircls) leads r-rs to concltrde that the existence of these 2 morphs most parsirnoniouslr.repre122

Peter Larson

Humerus Length vs Circumference

190

FMNHPR2081

I

180

BHI 6231 170

o o o o

CM 9380

I o MoR so

1

160

a

von:::

TWal 6t

150

o BHI

(J

6230

140

C) 130

120

BMRP2(X)'2.4.I

110

z'to

330

310

Length acracile lRobust l Nano O

Gorqo

Figure 8.15. Humerus length vs. circumference

Fioure 8.16. Femur lenoth vs. circumference

Femur Length vs Circumference @0

MvK I lzol FMNHPR2O8l I P81.12.1 CM 9380 I

560

520

6232

I I:--- ---- a MOR 1125 .BHJ6Z30 I

^ ltnp om

480

o

aBrE

-

',

MO

""

usNMv6l33l

o

rrrrootre

et.0. t

.E 400 C)

o

360

320

280

240

Al.CMztIJl

Ey

aBMRP2m2.4.1

900

1000

1100

1200

Length O

Gracile

I

Robust L Gorg/Nano

'y'ariation and Sexual DimorphBm

123

o* .n.. a---'-"

l1 ll

t,

)

\

t I

l ,

\.---.-.*

\

s--\

\ \ \ \ \ r\ t.t

Figure 8.17. Overlay

of

the ischia of (A) CM 9380; (B) RTMP 81.61, and (C)AMNH 5027 (after Carpenter 1990).

Acknowledgments

\

sents sexual dimorpl'rism. 'l'he discoverr,' of medullarv bone n'ithin the rnedtrllarv cal'itv of a robust specirnen of T. rex established N{OR ll25 as female (Schn'citzer et al. 2005), and therefore all other robust T re.r specirnerrs are, in all probabilitv, also female.

I thank Larn'Sl-raffer of Black Hills Institute for preparation of the figures and tables, ar-rcl Neai Larson for some of the pl-rotograpl-n,. I anr extrenelv grateful to Phil Currie, Bill Simpson,'I'irn Tokarrk, Phil Fraler,, Torn Williamson, Chris N{orrorn, Phil N{annir-rg, Kenneth Carpenter, N'Iike Henderson, and Scott Willian-rs, w,ho grabbed their tape measures ancl supph'ed rnissing data at:r nroment's notice. Conversations n,ith Kennetli Carpenter,

Ralph NIolnar, Thonas Carr, \'{ike Henderson, Phil Currie, forn Hururn, Creg Erickson. Bob Bakker, ancl:r host of others have pror,ided insight.'l'he 124

Peter Larson

Femur Length vs Circumference nD

MOR ll28

a1

I A*.*

lt 1

cM 9380

BrlI6232. 480

I

I

.By::z:z o lzF o"tt ui'olo* *o

BHr6z33. n MoR l

FlvfNH PR2081

aBHI

3033

at.o.t

at o

"",rrrroatlP

440

usNMv6183

E

€

t

+oo

I .!

i
280 240

I

I CMZU{)1.E9.r

ABMRP2002.4.l

?oo

800

1000

900

1100

1200

1300

1400

Length

a Gracile

I

Robust A

conrpii:rtion of clata n,ould not have been possible \'\'ithout the access, help, and paiience provicled bv the curators, collection rranagers, and preParators at all the irrstitutions I u'orked r,r.'ith, especiailv gill Simpson, Jack Horner, Carrie Herbel, N,llark Norel], [,uis Chiappe, and Ntatt Lamanna. Last, but certainli'r-rot least, thanks to all the discoverers and collectors rvho saved the specimens that pror.'ided mv data.

Anderson, ). F'., Hall-\lartin, A.. ancl Russell, D. A. 1985. l,ong-bone circumfererrce arrd ueigl rt irr rrrarrtrnLlr. birtl'. arrd ditro'attrcr. lorrntal of theZoological Societl' ofL,ondon A 207: 53-61. Bakker, R. T., Williams, \{., ancl Currie, P 1988. Nanotrrannus, a new genus of pvgrrv tlrannosaur. fron-r the Latest Cretaceous of \{ontana. Hunteria l(,5): I-7.6. Bellairs, A. 1970. '|he Life of Reptiles. Llniversal Books, Ner,r, York. Blakesle-v, J. A., Franklir.r, A. B., and Clutierrez, R. J. 1990. Sexual dirnorphisrn in northern spottcd ouls fron.r northu,est California. lotLnnl of Field Ornithol-

Figure 8.18. MOR 1125, a

female Tyrannosaurus

rex' clusters with other robust individuals

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J. S. 1q9tt. Serual size dimorphisrn and parental care patterns in a rnononrorphic .rncl a clirnorphic Laricl. Aule 107: 760-271. Raath, NI. .\ 1990 \lorphological variation in snall theropods ancl it's n'reaning irr slstcnratics: eviclence fronr Slrzlarsu s rlndesiensis. P 91-105 in Carpenter, K., and Currie, P J. (eds.). Dinosaur Slsfenzcflcs: Approaclrcs and Per-

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spectives. Canrbriclge LJniversitv Press, Canrbridge. Romer, A. S. 1966. \,'ertebrate Paleontologt. Universitl of Chicago Press, Chicago. Sanclercock, B. K. 1998. Assortive ruating ancl sexual size dimorphisrri in n'estern and semipalnratecl sanclpipers. Auft 11513): 786-791. Sato, 'll, Cheng, \'., \\11r, X.. Zelenitskv, D. K., ancl IIsiao, Y 200t. A pair of shelled eggs insicle a fenrale clinosaw. Science 308: 175. Schnell, G. D., Worthen. Cl. 1,., ancl Douglas. NI. E. 1985. Nlorphometric assessment of senral dinrorphisrn in skeletal elernents of California gulls. C'ondor 87:

484-491.

Schueitzer. \'1. H., Wittmerer. J. L.. ancl Horner, J. R. 2005. Gender-specific re prodtrctive tissue in ratites and Tt'rantrcsar-rus rex. Science 108:

1456-i+60. Schaaclt. C. P.. ancl Bird, D. NI. 1991. Ser-specific grou th in osprevs: the role of sexual size clirriorpirisrn. Auft 110: 900-910.

'lal'lor,'l-. G.

1970. Hon an egg shell is nrade. Scientific American 222(3): 88-95. Weltr,, T. C., ancl Baptista, L. 1988. The Life of Birds.4th ed. Saunders College Publications, F-ort \\/orth, 'fX. Winker, K., \/oelker, C. A., ancl Klicka, J. T. 1994. A morphometric exarnination of sexnal clinrorphisnr in the ll1/oplzilus,Xenops, ancl an Aulomolus fronr sotrtlrern \/eracruz, l\lexico. lotLrnttl of Field Ontitlrclog1,65(3): 307-323. Witrner, L. \,'1. 199t. 'l'he extant phrlogenetic bracket ancl the irnportance of reconstructing soft tissue in fossils. P l9-33 in Thonason, J. J. (ed.). Func tiotnl N'Iorphologl, in Yertebrate Paleorttologt. Canrbriclge LJniversitv Press,

Carrbridse.

128

Peter Larson

H. sapiens

erectus

o @

seozsocc

o o

'.-?t

o1. =

2-

H.habilis

.;

A, afarensis time of transition from juvenile to adult period (in years) 3.5 4.0 4.5 5.5 5.0 predicted age of eruption of molar tooth (in years)

Figure 9.1 . The compensation principle is well ttlustrated by the hominid

skull, which demonstrates a reciprocal relationship between cranium and jaw if one is peramorphic, the other is paedomorphic, and vice versa. Nofe that the main evolutionary trend is toward cranial enlargement (e ncepha I izati o n or a nten). After M cN a (1997). mara ri o ri zatio

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Martin Lockley et al

WHY TYRANNOSAURUS REX HAD PUNY ARMS: AN INTEGRAL MORPHODYNAMIC SOLUTION TO A SIMPLE PUZZLE IN THEROPOD PALEOB IO LOGY Martin Lockley, Reiji Kukihara, and Laura Mitchell

Tl-re pnrpose of this chapter is to shorv that the reason Tyrannosaurus (and

lntroduction

Carnotaurus) had miniature arms may be surprisinglv simple as n'ell as consistent u'ith the broad rnorphological context of theropod and saurischian grorvth d\,namics ancl heterochrony. Inherent, or formal, morphodr,namic groli,th irends (sensu Gould 2002) lead to strong anteriorization (of the head) in derived, large (mainil' perarnorphic) members of varions theropod, saurischian, and dinosaur clades, as well as in other r,ertebrates. These seem to be of no obvious functional sigr-rificar-rce (sensu Gould 2002), ieading to il-re inference that we sl-roulcl pav more attention to these r-norphocll'narnic trends as part of the inherer-it structure of veriebrate organization. For example, in arnphibians (salarnanders ."'ersus frogs), pterosaurs (rhamphorvhnchoids \rersus pterodacty'loids), sauropodomorphs (pro-

sauropods versus brachiosar-rrs), orr-rithischians (primitive th-vreophorans versus derived ceratopsiar-rs), and primates (monkevs versus honirricl$, the latter (deril'ed) groups ahval's show more anteriorization (encephalization) than their prirritive relatir,es. There is also a compensatory reduction or loss

ofthe tail.

Liken'ise, in derived forms, tire inner (proximal) portions of the limb (fernora and hr,rmeri) are typicallv more developed than the distal portions. Tl-ris differentiation of proximal and distal limbs and feet or hands gives rise to diverse rnorphologies that have been interpreted as being of functional utilitl'-for exampie, grasping theropod hands or slashing raptor clarvs. However, such developrnental exaggeration or ernphasis in one organ or region of the bodv inevitabh,' results in underdevelopmer-rt in adjacent organs, as required bv the principle of corlpensation, also knou'n as heterocl-rronic trade-offs (sensu McNarnara 1997). Nlor,rnting er.,idence from evolution of development str-rdies (Carroll 2005)-populariy knorvn as evo-devo-suggests tirat organs must be looked at holistically (i.e., in the context of the rvhole bod,v) and that formal cler elopmental patterns and rr-rorphologies reiterate fractally and conr.ergelrih througl-rout the ',,ertebrate r'r,orld, and indeed in the biosphere in gene ral. T. rex is undoubtedlv one of tl-re most popular. iascinating, and controversial dinosar-rrs. Although iis iarge head and ferocious teeth have ob.",ious WhS

-.'=":saurus

rex Had Puny

Arms

lf grasping hands and long arms generally typify theropods, how does one explain the outrageously d i m i nutive forelimbs of Tyrannosaurus

andCarnotaurus....lt not at all clear why these animals indepen-

is

dently miniaturized their arms.

Fastovsky and Weishampel 2005, p. 283

131

ftrnctional rrse in fostering its repr-rtation as tlie king of the preclators (or an uncliscrinrinatirrg bone-crunching scavcnger or scavenger-predator), its tint' arn'rs star-rcl out as an Lrlrllsllal or anonalous rnorphological feature. Incleed, thc forelinbs are described as "outrageousll'climini-rtilc" bi'leading experts in the latest tertbooks (c.g., Iiastoi'skr.. ancl Weishantpel 200i, p 283). Cliven the prevalcnce offunctional explanations generatecl br,the Danvinian paradigrri (Goulcl 2002), it is not surprising that paleontologists have pondered the usc of such smali and apparentlv iestigial organs. A1though Darri inist-n tr.picallr, demands or at least prefe rs fur-rction:rl explanations, biologv gener:rllr' accepts that some organs arc llore functional than otl-iers, and the llsc of terms like vestigial acknonleclges the fact that function mav hal'e bccr.r lost or dimir-rished in some org:lns, as Paul (1988) inferred in the casc of tlrannosanrids. \\/e n'ill return to the specific case of T. rex forclinbs once \\'e iiave presented a broader contert in uLrich to develop our Llnderstanding of tl'reropod lirnbs. Functioniil argrlrncnts c:rn onh.take us so far because tl.rer,ignore inherent, intrinsic, or fornal grori'th ancl developn-rent. Hi'o-devo pronrises to gre:rtlr' subsrlrne and reorient the functional Daru inian paradignr. But evo-devo is not ne'"r,; it is rnerelv the rediscovert' of the sr-rbdisciplines of

heterochronl and rnorphocllnanics (Gould 1997; N{cNarrara I995, 1997) bi'biologists. This intrinsic, fomral approach has been knorvn for decacles, although undenrtilizecl, and can be traced as far back as Wolfgang Goethe ancl Ceoffror,Saint-IIilaire in the late 1700s ancl earlr'1800s (LeGLlader 2004). 'l'hese approaches are holistic and internallr'corrsistent, and, as current cxciterrent aboLrt evo-de\,o shon's, ther help denronstrate that n,e can reaci clevelopmental patten-rs in the fossil record, even though some biological (genetic :rnd nrolccular) er,'idence is not directli'available. We ner,'ertl-reless see the same patterns of rnorpliological erpression in :rncient and rnodern forms :rncl can thus unifr.,biologi'and paleontologv nore thoroughlr'. Incre:rsingll', it is possible to clemonstrate that these organizational trends or patterns repeat in manl groups in an ordered, lau.,ful n'av. 'l'he rnain thrust of this cliapter is therefore 2-fold. First, r,r,e rnakc the case that norpholog\,is not rrecess:.rri1r'cornpletelv or uholli erplicable ir-r terms of function because intrinsic growth clr,nanics, rihich Goulcl (2002) describes as forn'ral (and related to intrinsic generation of fonl), plav an irrportant role , as recclgnized bv stuclents of heterochronr' (NlcKinner.and \lcNarrara 1997; il.,lcNanrara 1997) and evo-clo,o (Carroll 2005). Second, an understancling of these formal dvnamics rer,eals that shifts in the tining or inorphological cler,elopment produces a cascade of cornpensating effects throughout the bodv so that if one organ gror.r's large, one or nrore adjacent organs u.,ill be reducecl in size and vice versa.

We arguc that T rer and other tvrannosar-rrids had srrall forclirnbs because thev had such large heacls-or nrorc accnr:rtelr', ne stress the nrorphodr,nan-ric cornpensation bet\\,een heacl ancl forelirr-rbs. 'l'hus, anterior grou th blpassecl other anterior orgalls :urd concentrate cl in the heac1. This is in contrast to the patterns observed in other relatecl theropod dinosaurs (cocluros:rurs), snch as tlic ornitliornirnicls, n'hich dereloped lorrg front

linbs and necks but hacl snrall 132

Martin Lockley et al.

heacls.

In such anirnals, anterior gron'th

concentrated in the forelimbs and neck (as n e ll as the anterior organs), but ner.'er becarne exaggerated in the head. Strpport for such a h1'potl-resis rs derived from an overvier,r,of recurrent morphological trends in the Theropoda as a rvl-role, and in the Saurischian clade to ri'hich thel'belong. Fractal or recursive trends mean that thev repeat at different le','els or scales of organization rvith similar br-rt not identical patterns (see Bird 2004 for definrtions). For example, as noted below, in manv tl-ieropods, includingT. rex, short forelin-ibs are associated lr'ith relaiively'long hind limbs. As poir-rted out bl'Locklel'and Kukihara (2005) and Locklev (in press), dimorphisrn in tl-re r,r'ell-knorvn dinosaur Coelophtsis reveals similar compensatior-rs (srnall forelimbs = large head, and large forelirnbs = small head) at the species level. (There is also a patten-i of compensation betrveen large forelirnbs and sn-rali hind limb, or vice versa, and corresponding cornpensations throughout the rvhole bod1,'.) 'fhese are larvful in the sense that the1, can be shown to recur fractallv at man.", differer-rt taxonornic levels ivithin the r,ertebrates, and so nust represent sone inherent pattern of biological organization. For exarnple, just as tl-rere is a polaritv betn'eer-r the 2 Coelopliysis dirrorphs or the primitive and derir"ed coehrrosaurs (ornithomirnids versus derived tvrannosaurs), so too there is a similar polaritv betneen prinritive and derived ceratosaurs (e.g., Coelophysis versus CantotatLrusi). In tlre latter case, the convergence betrveen Carnotaurus and T re.r in respect to forelirrb-head compensatior-rs is striking. We argtre that tl-re implications of this rnorphodl'namic approach are far-reaching. For exanple, it has long been knor.r'n that theropods had their hands free, trnlike other clinosaurs, and so rvere not o\rerspecialized or committed to qr,radrupedal locoi.r-rotion, like most other dinosaurs ancl the maiority of terrestrial vertebrates. How,ever, rve take this argument further b)'strggestir-rg that not onh' did the anterior limbs of tiieropods der.'elop phvsical fexibilitr., lrfiich in turn helps support a phvsical or bionechanical connectior-i lr'ith n'ing der,'elopment in birds, but also a close relationship existed betrveen the respiratorv svstent as an anterior organ and the anterior lirnbs. Thr-rs, it is inportant to think in terms of hor.v the aforernentioned morphod1'r-iamic der,elopment in lirrbs, neck, or head is closel,v integrated r,vith de-

velopment of ph1'siological svstel-ns like respiration. \\'e knori' that marn' theropods (coeiurosaurs and oviraptos:mrs) and birds hacl a fundarrentalli inportant relationship with the air (i.e., air sacs, feathers, wings, and fliglit), and we argue that this represents an emphasis on the anterior part of the middle s\,stem (pulmonarv svstem, anterior torso, and forelimbs). For example, Carrano and O'Connor (2005) describe the vertebrae and srnall ribs of the neck region of Ontitlrcmimus as being perforated bv the pulrnonarv svsteilr, although in larger, nrore peranlorphic theropods, like Tyrannosaurus ancl Carnotaurus, sor-natic grou'th eviclentlv bvpassecl the forelimbs and u,as concentrated in the head. These large forrns also frequentl,v developed extensive pneun-raticitr,-not just in the neck region, but often throughout the rl,hole bodv (Xu et al. 2004). The same pattern is seen rnost rnodern birds. Thus, small birds rra,v shon' less pneumaticitv than large ones. This is not directlv correlated \\'ith flight because some large birds, such as the ostrich, are flightless. Therefore, one n'iight argue that rn thc larger theropods, as rs Why T.lratr osaurus rex Had Puny

Arms

133

the case in large birds, the nfiole boclr hacl become like an enlargecl hu-rg. Feathers are also a llleans of incorporating air ri'ithin the boundaries of the phl,sical bodr. One rriight argr-re, therefore, that feathered forrrs n'ith little skeletal pnetrrnaticitv ha','e a nrore outnard relationstrip ilith the air than large forrris u,itl-r rvell-cler,elopecl internal pneum:rticitv but no feathers. Agairr. llris is arr erarrrple of corrrpcrrsrrliort. Before preser-rting the data that support these morphological comparrsons and inferences, it is necessarr,to outlirie the morphodl'nanic paradignr and its stronglv heterochronic flavor.

The

T\l'o generations before Darri,in introchrcecl the concept of natural selectior-r, u'ith all its functional inrplications, the German founders of moclern biologr', incluclir-rg Goetl-re, n'l'ro introduced the term morphologt, thought in terms of dvn:rnic processes. The recent introduction into the English langtrage of the verb to morph emphasizes both this dvnarnic connotation ancl tlre resLrrsence of strch process thinking. (fhe OxfordEnglishDictionary defines this verb as to "change srnoothlv and gracluallv from one image to another.") hrterestir-rglr', this trsage is intirnatel-v associatecl n'ith the drnanic field of anirnation. 'l'his clvn:rrnism contrasts n'ith the mincl-set of

Morphodynamic Paradigm

spatial coordinates, rneasurements, and discrete character attribr-ites associatecl

lr'ith n:rnr, tarononric, anatorrical, nrorphornetric, and cladistic

ap-

proaches that follon,ecl. Although these are ali useful to varving degrees, rnanr,of the contributior-rs of the carlv Gerrnan biologists (e.g., Coetl're and Ernest Haeckel) n'ere often oi'erlooked li'hiie attention r',,as directed to tl-re u'eli-established tradition of monographic description of anatoml' for clas-

sification purposes. In effect, our concept of rrorphologv becarre frozen, and species vn'ere mostl'n' described on the basis of adult forms that representccl tl-re final n-ranifestation of thc dvnamic proccss of ontogenr.. Such cataloging, althorrgh important, has sometines been characterized as rnere st:rmp collecting, ancl it shifts our mind-set au'ar,'from tlie dt,namic, org:rnic process. In the contert of the dvnamic nature of the gron'th process, this charge is r.rot n'l-rollv ur-rjustified. For exarnple, as notecl by Arthur (2006), onlr,a feri, 20th-centun,biologists r,r'orking betvn,een 1900 and 1975 u'ere realh' focused on thc cl1'namic relationships betr.r'een evolution and dei.'elopn-rent; among these u'ere Juliar-r Huxlel', Cavin de Beer (1940), and Dl{rct,Thorrpson, ri'hose classic On Crowth and Form (1917) has been cited as an exarrple of "the tlieorl of transforrnations" (Arthur 2006, p. 401) dealing u'ith the tvpes of macronrorphological clr,r-ran-rics n,e discnss here. Hori.'ever, despite the freezing of tire concept of morphologr.', lvhich ivas originallr,' closelv allied to the cll'namic concepts of rretamorphosis ancl transmutation (the latter:rn e arlr' 19th-centnrv svnonvm for evohrtion), Gernran biologists sucir as Hacckel (li,ho coined the term biology) \\'ere at the forefront of embri,ological rescarcir, thus maintaining a foctrs on cltnamic processes. Haeckel (1866) also coined the term heterochrony, and he developed the famous biogenetic lzrr','that "ontogenv rccapitulates phr. logenr." 'l'hus, an anteriorization trend (P-A) in ontogenv m:rv parallel one in phr logenr (as seen inTrrannosaunrs; see belou). Despite the shortcom1)/

Martin Lockley et al.

ings in this lan' if taken too literallr', its general relevance in linking indir,idual clevelopment and evolution has rrerit. hrdccd, the recent emergence of the evo-cievo field is in itself stror-rg validation of the rener,ed interest in this approach (Arthur 2006). There are even clairrs of a reverse biogenetic

law'(Suchantke 1995), u'hich can be characterized as er reverse rnorphodr nanic moverrient (i.e., an anterior-posterior [A-P] tiend in one organ mav be compensated for br,a P-A trend in another). What is of fr-rr-rdanental importar-ice here is to note tl-rat heterocl-rrorr-v is not some specialized branch of biologv. Indeed, a compelling case can be made that it is essentiallv a svnonym of the original dvnarric concept of morphological dei,elopment as process, which emphasizes the highil,' organic natllre of changing or morphing of anatorn, through time. Nloreover, the dir-ramic processes are driven b1, internal oniogenetic forces. Although such dvnamics nere recognized in the biometric sense b1' such concepts as allornetrl'or nonlinear gror.r'th, thev ha.,'e been overlooked bt,the Darrvinian notion that the organism is too rnuch under the spell of external influences tl-iat force it to passiveh,adapt to the environmer-rt. Gould (2002) clearl.,, recognized the difference betu'een the forn-rer intrinsrc

Coethean (or forrnal) perspectir,e of the Gern-ranic school and tl.re latter extrinsic Darr,r'iniar-r (or functional) perspective of the English school. It is onlv noli,'that the Darri'inian and neo-Darq,'inian (genetic) paradign-r l-ras been explored to the poini t'here deficiencies in ftrnctional explanatiorrs are evident that the intrinsic or formal paraclign-r is cornir-rg back intcr voglre arnong rnainstreanr biologists. Ccnetics, in its earlv davs, ain-red to support the selectionist Darwinian paradigm br,using mathematical populatior-r-base cl st:rtistical rnodels (harking back to l9th-centurv social Darn,inisn-r and Malthus's icleas of populations competir-rg for scare resources). Ironicallr, nrodern cleveloprrental genetics ancl er.o-devo nou. inforn ns that form and species dii,ersit)'is generated bi'ir-rternal processes tl'iat are most

d','nanic and complex in the verv earlv formative stages of ontoger-ry. Put sin'rplv, focus has shifted from the paracligm of a passi.,.e Darr,','inian organism, pushed around bv the erternal environrnent and competing to snrvive bl.functioning properll', to an active rrodel of clvnamic organisms generating form throtrgh complex internal or fornal organization. Despite tl-re prer,'ior,rs strong focus of nainstrearr biologl' and evolutionarv studies on Daru'inian selection paradigrrs, a number of norkers have kept alternative perspectives alive. Anorrg the rnost relevant studies are those that have explored the cl1'namics of heteroclironv (Goulcl 1977; N{cKinnev and il,IcNan-rara l99l; N{cNanara 1997). The latter studv introcluced the irnportant concept of l'reterochronic trade-offs that are, in fact, basicallv a st'nonvm of thc compensation principle ir-rtrocluced by Goethe (1795). This principle essentiailr' tells us that no organ can develop rvitl-rout a reciprocal effect on an adjacent organ. N'lcNanara (1997) gives the exceilent example of the tracle-off betrveen the large hunan craniurrr and srnall jari'ancl contrasts it rvith the opposite oi reciprocal case of the srrall craniurn and large jan', as seen in the chirrp or certain primitive honrinicls (Fig. 9.1). In such a case, the larger organ is peramorphic (exhibiting ntore grou'th) ancl the srraller one is paedomorphic (erhibiting less grori th). It seems that sucl'r Wht f\'a'.csaurus rex Had Puny

Arms

135

cornpensations are follnd universaill'throughout the organic w'orld and thai they are an integral factor in the evolutionarv process. In this regard, lve may r-rote the recent resnrgence of interest ir-r the work of Geoffrov Saint-Hilaire (l8ZZ). Endorserrents b1'Thoni (1975), Gould (1985), DeRobertis and Sasai (1996), and LeCuyader (2004), among others, ciearly demonstrate Saint-Hilaire's profound understanding of ir-rtegrated organization in organic s1'stems as early as the 1790s. Thus, Saint-Hilarre recognized and endorsed Goethe's compensation principle, which he called tl-re "lau' of balancement of organs," and tried to encourage French anatomists such as George Cuvier to understand its fr-rndamental in-iportance and pa,v more attention to the higher level of biological tl-rinking going on rn Cermanv (Lenoir 1987). Despite ihe rejection of ihis svstem of thinking bi, Cuvier and later by n-rost Darr.vinians, rvl-io labeled the school "transcendenial Nature Philosophv," Saint-Hilaire has been proved right in his thesis that ail organisn-rs displav a fundanental unitv of compositiorr and unitv of organization. Thus, he realized that clifferences in rnorphologl'between organisms r,vere only superficial and the result of different ernphasis of organs durir-rg cleielopment. 'fhis is essentiall,v the central message of heterochrony; whicl-r is still paid too little attention todav. Saint-Hilaire give explicit examples of differential development, noting ihat if a bone did not del'elop in one species, it could be shorvn to l-rave been arrested at an earlv stage, when it r,vas

still tissue or cartilage. N{ore pertinent to the present stucll; Saint-Hiiaire noted that bod1, plans repeat again and again in what todav rve u'ould call a recursive or fractal pattern, lvhich he variouslv called "r-rnity of organization," "unit,v of plan," and "unitv of cornposition." Thus, rvhen "der.elopmer-rtal genetics . . . arrived on the scene like a thunderbolt" (LeGu1'ader 2004, p.244), it became clear that horneotic genes (Hox genes) of the homeobox shorved the same A-P or-

ganization as the macrornorphologl'-exactly as Sair-rt-Hilaire frequentl,v noted in his principle of connections (or theorv of analogues). This is norv call,ed colinearily (Duboule and N{orata i994). It is outside the scope of this chapter to delve further into Saint-Hilaire's prescient observations, except to note that his claim that arthropods lvere organized like upside-down vertebrates, although long scornecl bv Cuvier and many subsequent generations

of ar-ratornists, has been shoun to be genetically correct: that is, "tu'o major

directions . . . the that r.vith dorsal expression in the vertebrate and vice versa!" (LeGuvader 2004, p. 252). The r-nessage is tl-rat it is dangerous to dismiss prescient holistic thinkers because their ideas are perceived to be too general, too complex, not obviouslv applicable to specific cases' or otheni,'ise hard to follow. Sair-it-Hilaire, like his contemgenes have been discovered rvhich intervene in antagonistic

insectt gene ivith ventrai expression is the

san-re as

porarv Goethe, lvould have been quite at hon-re discussing the compensation principle, antagor-iistic genes, and tl-re balancernent of orgar-rs n'itl-r an1'or-re versed in modern heterochronic and developmental studies. Like modern students of heterochrony (McNaniara, personal communication), Goethe and Saint-Hilaire n'ould likely have been surprised to learn that developmental genetics claims that rnar-n'of these insights are new in prir-rciple, r.vhen in fact such insights were around at tl-re birth of biologr', and since then, devel-

136

Martin Lackley et al.

opmental genetics has beer-r n-rostly concerned n'ith rediscoverv of these principles and explar-ration of details and mechanrsms. 'i'he fuller potential of such approaches is brilliantll'realized in tl're lr,ork of Schad (1977) on Man and Mammals, n,hich u,as brieflv strmmarized bv Riegr-rer (1985, l99B) ar-rd Locklev (1999a) and applied to dinosaurs (Lockley 1999a, 1999b,2001, in press). In these and a few other related str-rdies, the tern morphodttnamics has been introduced partly as a rreans of redvnarnizing the concept of morphology so as to reflect its original process meaning, but also as a convenient n'ay of stressing that there are morphodi/namic trends in the evolution of varior-rs clades, such as increasing anterior or posterior developnental emphasis. These cephalo-caudal or caudo-cephalic trends have been known for many years, and a substantial literature on the topic exists, especiail,v in the field of phvsical anthropology (Kingsbun' 1924; Verhulst 2003). In recent years, developrnental microbiologl'has been ror-rtinelv preoccupied with horv A-P axes and polarities develop (e.g., Wallenfarrd and Se1dorrr 20007. Possibl-v the best-known and most obvior:s example of a recursive anteriorization trend is that referred to as cephalizctiorz, lvhich is seen in vertebrate clades and in vertebrates ir-r general (Fig. 9.1). Other examples include the polaritv betneen prirnitive arnphibian organization, as seen in tl-re salamander morphotvpe (characterized by a long tail and small head), and frog morphology (large head and no tail). Everl'schoolchild knows the stori' of tadpole-frog metamorphosis. Liker,vise, we see the same trends u-i prirnates (from monkevs to hominids). The sarne trend is also obvious ir-r many dinosaur clades such as ceratopsians, and here \ve point to the reiteration of the trend in theropods. Such anteriorization trends can generalll' be classed as correlated progressions, i,vhich refer to the reiteration of directional trends in evolution that follorv repeated or fractal variations on a theme (sensu Kemp 1999). This concept is essentially sirnilar to the concept of colinearitl, (LeGuvader 2004). Schad's genius u,as to recognize that the expression of ph1,'sical exaggera-

tion of anterior or posterior organs in anr animal (man-rrnals in his

1977

studv) rnust be seen as onl,v one side of a compensatorv relationship w'ith phvsiological processes. Phr.'siologically, for example, r-rngulates (r,vhich are predominar-rtlr,'large, placid, longJived, derived, and evoiutionarilv specialized) have rvell-developed posterior digestive (or metabolic) slstems (rnultrcharnbered stomacir) ancl iimbs designed for sustained (long distance) loco-

rrotor efficienc\,. Horvever, the main ph1'sical exaggeration is seen in the anterior regions (horns, shoulders, manes, bearcls, front limbs ofter-r larger than hir-rcl). In striking contrast, the predominantly small and evoh,rtionarill unspecializecl rodents shou'tl-ie opposite, or reciprocal phvsical and phvsiological organizatior-r. They are phl'siologicallv dominated (anteriorly) b1' overactive sensorv and nervous svstems (sense-ne1,e en'iphasis) ancl are behavior-

allv frenetic and shortlived, u'ith u'eak, lon.endurance lirnbs, but

they

express their rnaxirnurn or exaggerated ph1'sical clevelopment in the posierior part of the body (long tail and hind limbs longer than front limbs). The carnivores represent a middle or central gror-rp (trpicalh intermediate in size),

in

r,r4rich the anterior and posterior physical and phrsiological svsterns are

Why fyra^rcsaurus rex Had Puny

Arms

137

Ftgure 9.2. A holistic viev. of 3 major groups of placental mammals (after Schad 1997; Lockley t999a). The rodents, carnivores, and ungulates express d if fe re nt e m p h a sis of the physiological organ systems, i.e.,
m

ic

ci rcu I ato

hn

I

ir

(o

r

ry),

respi rato

an

d

/r'l i n a< t i t n\

-

RODENT

UNGULATE

CARNIVORE

,/l\

/l\

ry-

m eta I i

m

h

af tha nncfa-

rior, central, and anteflol physi cal

(so

mati

d

em pha -

organization reveals many fractally re peated ( i te rativd g rad i ents such as, small (pae-

srs. Such

dom or p h ic-sho ^^-+^+in^ lul t 9c)LdL/ut )/-A^.+

rt

Ii

ved

I^-^l l-lwtol

LARGE

CENTRAL

SMALL

centers of gravity (em-

metabolic limb orientation

rhythmic orientation

nerve sense

orinettation

tT{ VU

w

.,., /f\\

.. t

I

\

'f) (r\tt

I

\/ 4 roES

5 TOES \

\

SMALL BODY BIG TRACKS

/

Y

X

RODENT

UNGUBL.ATYES SMALL TRACKS

-

range) and large (peram o rp h i c- | o n g I ived - | o ng

Early

Later evolutionary development

evolutionary development

estation-wide ra nge). These gradients also cor-

g

nd to

o

ry trends from primitive to derived. Moreover, the morphology of the tracks respo

evo I utr

o na

also show the posterior

to anterior shift, with progressive loss of heel in Iarger forms. Thus, the track-body size relationship cannot be interpreted functionally, but i

n
relative shifts in the development of proximal and distal portions of the limb.

PHYSICAL POLE PHYSIOLOGICAL POLE

less cxaggeratecl (more balanced) ancl tl-rc cler,elopmental emphasis is

rrore

centered in the circulatori'and respiratorr,sl'stens (he:rrt and lung rhvthrnrc athleticisn) (Fig. 9.2). Thus, ther,'rhvthrnicallr'alternate betri'een intense

frenetic and placid bchaviors

as an expre ssion of

the strong ir-rfluence of their

rhr thmic organs. 'l'l-re clistribution of incisor, canine, and

nolar teeth also reiterates the outn'ard-inn,ard and A-P polaritt'of rnamrnal organization. Bec:rtrsc the jan's are analogous to the limbs of the head, thc r.r'rolar teetl-r correspor-rd to a greater der,elopnrent of the inner or proxirn:rl jari; paralleling the inner liurbs of the ungulate, ufiereas the incisors correspontl to the distai or ottter regiolr. As previouslv r-rotecl, the essential lressage of Schad's work has beert strnrrnarized bv Riegner (198t, 1998) ancl Seamort, and Zajonc (1998), and (Locklcr 1999a, 1999b). Although this n.rorpliodvnanric approach is not let u'iclelv appreciatecl, is higl'riv holistic in that it accornrnodates rriorpl'rologi', phvsiologr', heterochror-rr', fractal orgahas been applied to dinosaurs

138

Martin Lockley et al.

nizatior-r, and even color patterns. All r-najor ar-rirral groups are re.,'ealed to be complex svstelrs il'ith the t1'pe of organized and compensatorr polarities outlined above. The rodent pole (i.e., small, predoniinanth,paedornor-

phic forms r.vith posterior orientations: long tails and hind limbs) is rnore ollt$'ard and connected to the environrnent ancl its stimr,rli, u,hereas the trngulates are more inlvard and emancipated from the environment. 'l'his is literalll' trtre in terms of size, but it also affects behavior such as home range, aggressior-r, social strtrcture, and need for nesting protection (see Schad 1977, 1992,for detailecl explanations). T'here is also a polaritv of organization betleen sn-rall, predorninar-rtlv paedon'rorphic clades, such as rodents, u'hich are verv dir,'erse (in species ricl-rness) br:t not disparate in form, and large perar-norphic clades, sllch as ungulates, which are less diverse in species but mr-rch rnore disparate in forrn. Thus, in the san-re r,i.a1, that the individual r-rngulate takes up more physical space than the rodent, tl're ungulate is also further separated frorn other ungulates in terrns of its n-rorphospace characteristics (sensu Foote l99l). Again, these characteristics indicate ar-r organization tl-rat is fractal and recrlrsive, in that the general stnlcture of taxonomic groups repeats at all hierarchical levels rvith an almost endless, staggered seqllence of ninor variations or-r the general therne (see Bird 2004 and Carroll 2005 for discussion of the inherentiv fractal and recursive organization of orgar-ric svstems, and the use and definitiorr of terrr-rs like iteration, recursion, and staggered sequences). Conwav (2003) also stresses the rarnpant convergence in nature that points to inherent organization ratl'rer than randonness. An excellent exampie of sucl-r fractal organization nas demonstrated br" Portmann (1964), r,r4ro sholr'ed that in mammals, r-rngulates hal'e large forebrains relative to hind brair-rs, in con'iparisor-r lvith rodents, ',vl-ricl-i have

the reverse organization. He called this the 'heo-pallial index," rvhich is a rneasrlre of the relative size of the forebrain or neocortex. It is small in rodents, intemediate in carnivores, and large in ungr,rlates. So ungulates (e.g., rurrinants) manifest more complex social behavior and are percei','ecl as being inclined to mrninate inu'ardh'. Thus, the distribr,rtion of physical brain niass in these rnaior mamnal groups is a fractal reiteration of ivhole body A-P organization. This general trend in vertebrate brains has been confirmed by subsequent stuclies of reptiles (Hopson 1977, 1979; Jerison 1969), nonavian theropods (Chatteijee 1997; Larssor-r et al. 2000), and mammals (Kaas 2000). The same is true of feet and footprints (large posterior emphasis in rodents and more anterior emphasis in large r,rngr-rlates; Locklev 1999a). In tl-re case of brain mass distribr,rtion, tl-re in*'ard-anterior characteristics of tl-re ungr,rlate neocortex rnirror the inward or proxirlal characteristics of the molars. With this background, we can trlrn to the er.o-devo paradign'r, n'hich is highly convergent u'ith the Schadian paradigr-n. It shor,r's that the organization and influence of Hox genes lead to sin.rilar morphological expressions in related organisms that are higl-rlv recursire or fractal, leading to endle ss forms that are variations on a universai or courmor-r thene or organization. (Organization iiterally means "an ordere d sequence of organs.") However, before being completelv sedr-rced bl the compelling er.idence for Why

i','z^ts32srus

rex Had Puny Arms

139

tl're organrzational role plaved

bl,Hor

gene s

in controlling, driving, or ex-

plaining nrorpliologr, n'e sirorrld note that Schad (1977) and others, such as

Portmann i1964), rnust be given credit

as

pioneering bioiogists n'ho rec-

ognized these orgar-rizational patterns iu macronorphologr', phvsiologv, behavior, ancl color patterns before tl're sane organizational patterns and strtrcturc u'ere clemonstrated in the microscopic lvorld of rriolecules and Ho.r genes. It is nori iime for a svnthesis, and it is in paleontologv, n,here macromorphologv is available but genes are not, that

r,r'e

can effect a mar-

riage of these rnacro ancl rriicro (evo-devo) fielcls (Carroll 2005).

evo-clevo paradigm (Carroll 2005) is sirnilar to that outlinecl above as the rrorphoclr,namic paradigm. N'lolecular ancl cellular

The Evolution of Development, or the Evo-Devo Paradigm

In rnan.,,respects, the

biologists have in recent r.'ears studiecl the honeobox (secluence s of horneotic genes in regular repeated segnents or boxes) and have show'rr that diverse inr,'crtcbrate and vcrtebrate species share an orderlv A-P arrangenrent

of tl-rese clei'elopnental ger-res knor,r'n as Hor genes r,i'ithir.r tlie homeobox. N'{oreover, the arrangement of these Hor gcnes is in the sarne, or sin-rilar, A-P order as thel'appear in the organs of the bodr (Fig. 9.3). Thus, the sequence or orcier of cieveloprnental Hox genes is iike a nicrocosm of the rvhole boclr'. implvir-rg a highlv fractal or recursive forrn of organization. Such n'ork shou,s tl-rat not onll do individual Hox genes develop from anterior to posterior in earlv embrl'ogenesis, but this san're A-P directionalitv recurs in ihe der,'elopment of the 7 rhonbomeres of the hincl brain, and

Figure 9.3. The homeobox demonstrates a parallelism between the A-P organization of Hox genes and the A-P organization of actual body organs. Modified after Carroll (2005).

t I l

----j-d **---t-*

'J

sex combs

labial probiscpedia deformed reduced antennapedia ultrabithorax

il::,j.t-.;; ., , r:T1 "nilix$ w 140

Martin Lockley et al.

abdominal

a

abdominal b

w - "sw, -l-

in the development of somites throughout the

u ]role bodt, ancl

in limb for-

natiorr (fig.9.l). As srirrmarizecl bv Carroll t2005, p. 100), n'e knoi.r'eractly i,r'hicl-r Hox genes are involved in the erprcssion of these stages of celltrlar and sornatic developn-rent and can characterize thenr as "the staggered expression of the Hox genes" (see Fig. 9.4 for cletails). This clearlr inplies a sequence of development that is heterochronicallv controllecl or timed. Moreover, in the case of the developrnent of body somites, Hoxc6 is associated rvith the bor-urdarv betn'een cervicai and thoracic vertebrae and is there fore closell' associated n ith the point of origin of anterior limbs. Carroll (2005), like other e'".o-clevo biologists, stresses that all de',,eloprnent is strongl-v controlled bi' the timing of Hox gene expression, n'hich ir-r tnrn rs controlled bv corlipler genetic s'"vitches. Again, tiie importance of heterochronic tinrir-rg in ger.rerating morphologv is emphasized. Slight differential changes at earlv stages in development can ha'ne profound effects and have nnequivocalll,been shou.'n to cler,elop different races (rnorphotr.pe$. Carroll (2005) goes on to stress that ail el'olution can be unclerstood tlrrorrglr lhc epplit atit.rrr of tlris llaradigrrr. Srich r,vork sholi's that although incliviclual ontogen\,is a conrplex heterochronic process, the general arrangement of Hox genes is repeated fractallt' or recursi','elr,throughout tl-re organic r,iorld. Thus, it appears that all organisms har"e the same general patterns of organizatior.r, but t]rer" are different in cletail ou'ing to subtle shifts in the tirning of development and n-rorphologv frorn cell to cell, organ to orgar-r, indir,idual to indir,'idr-ral, species to species, and clade to clade . (For a discussion of terms hke iteratiott and recursion and the application of corripleritt. and chaos concepts to el'olutionan' theorl; see Bird 2004.) In short, we can non' be increasingil' confident that the evoiutionan,relationships n'e perceile in related clades (e.g., ceratosaurs, coelurosaurs, and other groups n ithin tl-ie theropods, or :lniong related clades such as noclern birds) can be understood in tenns of these A-P morphodvnarnics and lleterochronl; u'hich have been sholr,n to applv consistentlr,to a u,ide rattge of exlarrl r ertebrate clades.

As indicated abor,e, there is gron,ing evidence to suggest tl-rat organisrn growtl-r (morphogenesis) is nruch nore ordered than previouslr'thought. For exarliple, Sfrubin and Alberch (1986) demor-rstrated that the lirnbs of rnost higher vertebrates follou,sir-nilar grou'th patterns or programs. Similar

in l-ris study of prirnates. These str,rdies shou'that durring earli,ontogenv, tl're distal limb der..eiops first (A-P direction; Fig. 9.4). Later, the proxin-rai lirrb develops at an accelerated rate, relative to the foot, especiallr, in large peran-rorphic species (N'lcNarrara 1995; Long ancl N,lcNarnara I995, 1997; Locklev in press). T'l-iis is, therefore, a posterior-anterior (P-Al clistal-proximal or cauclo-cephalic) cie','elopmental direction for the limb as a n'hole. In differer-rt species, as differential (heterochronic) gror th retards or prolongs developrnent, the ratio of disial to proxirnal lirnb proportions u'ill r,'arr,'considerablv and u'ill shor.r'a strong rel:rtionship to size observatior-rs have been n-rade bv Verhulst (2003)

.

Limb Construction and Morphological Organization in Theropods and Related Vertebrates

Finrrra

Q

East

L lTnn tn h^t-

tom) Dynamic A-P (or west-east) flow di rections in Hox genes, hind brain rhombomere, wholebody somite, and limb develo p ment. Proxi mal distal orientations in the limb correspond to A and P, respectively.

lndividual Hox Gene

^":;::

%_: Fore r-------.

F_Hind--__--_---{

--

Mid

Hind Brain Development

Hox

Somite Formation

Htno Eraln

a2

Hox b3 Hox b4

i t-l

Whole Body

Rhombmeres of

Hox b1

Shift in Hox Gene Expression

after Carroll (2005)

,-7

Hox b2

Anterior - Posterior

Modified

(EveDevoOrientation)

Poslerior Expression

rrtiI I _**____i --fI-r-r--l L ru

mtt

L -,

:;l

r

I

i:

on'"'$''o'

i

Cervical lThoracic Hox co

Proximal

Limb Formation

: --e\

Z;1

T/

-

Distal

inlerdigital tissue dies early = early distal = Paedomorphic

/dealh

,"lJ:[,i1,1,"",T:fffi,.

f*no*"

Some Hind Limb Proportions T'he distal-proximal differential is particularll'obvious ii'r the saurischian clade. If rve compare small, primitive theropods with large, derived sattropods, u,e find that tl-ie former have relativeil'large feet (distal organs) and short inner (proximal) limb bor-res (fernora and hurneri), whereas the reverse is true in the sauropods (Figs. 9.5,9.6).li-r general, the theropod-sauropod polaritv is also a P-A polarity: that is, theropods are bipedal, hind lirnb rvalkers, u'hereas sauropods moved ar-rteriorl,v into quadrupedal postr-rres rvith iong anterior necks (Lockley 1999a, in press). The sarne posterior (biped)-anterior (quadruped) polaritl' repeats in manl' other dinosaur clades and is related to many factors, including size and phvlogerry' (primiti'n

e l'ersus derirred characters).

If r,r'e narrorv our focus to tl-reropod lin-rbs, rve can look at both printitive and derivecl clades. Among the ceratosaurs, it appears that srnall, gracile forms like Coelophysls and Elaphrosaurus ha','e relati','elv short fernora cornpared li,ith larger robust forms like Ceratosaurus (Fig. 9.7).

142

Maftin Lockley et al.

Figure 9.5. The principle of distal versus proximal emphasis in saurischian

limb elements (after Lockley and Jackson in press; Lockley in press). From left to right, each

row shows a theropod, prosauropod, and a sauropod. (Top)Dilophorus (A), Anchisaurus

sau (B),

and Apatosaurus (C)

are all relatively primitive re p resentatives of th e i r respecttve g rou ps. (Bot-

tom) Tyrannosau rus (D), Plateosaurus (E), and Brachiosaurus (F) are re d erived re p rese nta tives of their respective groups. Cf. Figure 9.6. mo

In the rnore deri'ed coelurosatirs, which include the tyrannosaurs and ornithornirnids, *,e fincl similar patterns. 'l'he gracile ornithomimids suggest a contrast lvith ihe robust tvrannosatrrids. The relative proxirnal lirrb (femora) lengths are somervhat shorter thar-r in the tvran'osauricls and therr distal li'ib elements (metatarsals) are longer, thus fitting the general trend tou'ard distal emphasis in smaller, predomi'antlr paedomorphic forms

(Fig e.B). within the 'li'rar-rr-rosauroidea, taxa like Dilong and Albertosaurus j;,veniles tencl to have shorter femora than large foms like Ttrannosaurus. rn Why T'1ra.,.osaurus rex Had Puny Arms

143

Figure 9.6. The principle of distal versus proximal emphasis in saurischian I i mb elements i I lustrated by a display in the American Museum (after Norell et al. 1995). Genera from left to right are Diplodocus, Apatosaurus, and 2 Allosaurus. Cf. Figure 9.5

Figure 9.7 Hind limb proportions i n Ceratosau rs. ll oft\ Cna Coe lop

I

a nh

i<

n i cl aa

hysis (A),

Li I ie n -

sternus (B), and Dilophosaurus (C). (Right) Ceratosauroidea

Elaphrosaurus (D) and Ceratosaurus (E).

Coelophysoidea

Ceratosauroidea

Figure 9.8. (Left) Hind limb proportions of Col eu rosa u rs.

O rn

ith

om

i

-

misaurs. juven i le G a I I i m i mus (A), Ornithomimus (B), Struth i om i m us and Gallimimus (D). (Rig

ht)

(C),

Tyra n nosa u ri ds

;

hypoth etica I j uven i I e A l -

bertosaurus (E), Dilong (F), adult Al bertosaurus (G), and adult Tyrannosaurus (H). Shown are their proportions when scaled to the same limb

Ornithomimosauria

Tyrannosauroidea

size.

Dilong (Xu et al. 2004), the feet (phalanges) are significantlv lor-rger thar-r in the larger taxa. Long and McNamara (1995) inferred important developmental shifts during tyrannosaur ontogenr'. 'fhus, jur,'enile Albertosaurus pr,rrportedh' has a relativelr, long foot (distal lirnb) and short femur compared with an adult. (Note, hou'ever, that the reconstruction of the jr,rvenile Albertosaurus was h1'pothetical fRussell 1970, figs. B and 9 therein], and so must be further tested before inferences are dral'n'n.) It is nevertheless interesting that Russell (1970) and Long and N'{cNamara (1995) depicted the jr,n'enile ivith strong posterior er-nphasis, with long tail and relativelv small head cornpared w'ith the adr-rlt (fig 9.9). This n'hole-bod1,'A-P polaritl'appears to r-nirror the pattern seen in other vertebrate groups discussed abol.e, and is further conparable to the proxinal-distal polaritv seen in limb elements. 'Ib clarifr: il-ris poir-rt, we stress that vectors of A-P (or cephalo-car-rdal) grou'th for the r.r'hole body follorv a }'read-trur-rk-tail direction along the vertebral column. Holr'ever, appendicular organs such as the lirlbs ar-rd the jaw are better described ir-r terms of their proximal-distal elements or orientations. So the hind foot rs posterior relative to the ufiole f6fl1', br,rt also distal relative to the n-rore proxin'ia1 (ar-rterior) location of the fernur. The san-re proximal-clistal orier.rtation rs evident in forelirrbs ancl the jau's, althor-rgh it is clear that these organs are more closelr,' connected to anterior organs of the axial bodl'. h-r tl-re case of the jaw, especiallv in mammals lr,here incisor-canine-rnolar heterodontl' rs rvell developed, these teeth are situated distaih, medialll', and proximallv relatir,e to the cranium. Holvever, because jari s protrude anteriorlv relative to the axial bodl', the terms anterior medial and posterior could equallv lvell be used. As noted belolv, the respecti."'e A-P or prorinral-distal polarity, betrveen cranium and jar.',, is proving important in sttrdies of tvrannosaur sn.rali fornrs like

Wht-:'.'r^^otuurus

rex Had Puny Arms

145

Figure 9.9. Whole-body roportio ns of hy poth eti cal juvenile Al bertosaurus (A) (after Russell

p

1970), Dilong (B), adult Albertosaurus (C), and ad u It Ty ra n n osa u r u s (D) scaled to the same body size. Modified after Mc-

Namara (1995).

ontogenr' (Carr i999). It is :rlso noterl'orthy'that upper jarv nraintains a fixecl cranial (anterior-proxin-ral) orientation i'r'hile tl-re lolr'er jar'", can move in a posterior (distal) clirection.

\Ve provicle a feri further theropod hind limb examples to help stress nature of this pattern. First, anong the large allosaurids ar-rd related forms (Fig. 9.10), n,e see :r sir.nilar ernphasis on the development of the inner limb (fenora). Bv contrast, in the srnall dromaeosaurids, rve see a much greater ernphasis of the distal lirrb (tibia and fibtrla: Fig. 9.11). This, of coursc, can be partialll'explained bv the effects of scaling (Pike et al. 2002), but such singie explanations do not negate the inherent proximaldistal lirrib compensations discussecl herein. For exarnple, thc repetition of the large prorirri:rl 'u'ersus srnall distal elerlient polaritv in large species and its opposite or reciprocal (small proxinal versns large clistai) elements repeats not onlv in dinosar-rr linibs used for lvalking, but also, as discussed tl-re r'i'idespread

146

Martin Lockley et al.

0 Hind limbs o{

Figure

9.'1

a | | osau

ri ds

la

rge

th

e

a nd selected ropods P i atn iz-

kysaurus (A), Allosaurus (il, and Gigantosaurus (C).

below, in u,ings of pterosaurs and bircls n'ith entirelv clifferent functions (Kellner 2003; lliddleton and Gatesr' 2000, respectir.eh). Some Forelimb Proportions

As noted bt,Middleton ancl Gatesl' (2000), in comparison r,vith T),rannoscurus and Carnotaurus, the forelirnbs of most theropods are nell cler,'eloped (cf. Fastoi'sk1 and \d/eisharrpel 20{J5). We havc alreadr, established that the proximal portion of the hind lirrbs is inore cleveloped in large t1 rannosaurids than in juveniles, but the sarne :rppears to be true of the forelin-rbs. Tlre hurnerus makes up abofi 50% of tl-re length of the limb. The lrunreral proportion is even more exaggerated in Carnotaurus, comprisirrg nrore than 60% of the lirrb lengtl'r. Compare this iiith the humerus proportion of less thar-r 40% lor StruthiomhntLs andOrnithon'Lirnus (Fig. 9.12), arrd the comrnent of Hutt et al. (2001, p.2291that the relativeiy small tvrannosallr Eotyrannus has a "manus proportionalh long tcligit II c. 95% of hunerr-rs length)." It is cle ar that the same dvnar-nics att?ct the front ar-rcl hind limbs in all these forrns. The consistencv in developmental dvnarnics

Figure 9.1 1. Deinonychosaur hind limbs Bambirapto r (A), Velocoraptor (B),

and Deinonychus

(C). Note short proximal

limb in Bambiraptor. Figures 9.7 and 9.8.

Cf.

across these rnr,rltiple organs and across multipie tl-reropod clades can hardly be attribr,rted to soleiy to function. Middleton ar-rd Catesy (2000) have shon'n similar patterns in the forelirnbs (ivings) of birds. For exarrple, srnall, predominantlv paedomorphic

flying birds such as passerines have short proximal humeri and long distal lvings, r.vhereas large (mostly perainorphic) ground birds have long l-u-rn-reri and short distal n,ings (Fig. 9.13). The same trends in proxin-ral-distal lirnb proportions are seen in comparing srnall, primitive (paedonorphic) rharnphorhyr-rchoicl pterosaurs and large, deril'ed pterodactyloids (Kellner 2003;

Ntitchell and Lockley',

ir-r

preparation). Here rve stress the point made bv all

heterochrorric strrdies te.g.. \lcNamara l99Ttthatcorrrperrsatiorrs or tradeoffs rrake rnost organisms a rnixture of paedon-rorpl-ric ar-rd peramorphic characteristics. Thus, a small or large animal mav onlv be paedomorphic or peramorphic ir-r tl-re ger-reral sense of body size (less or r-nore grorvth, respectivell').'l'hns, we see the sal-ne or similar patten-is in sn'rall (primitire) ancl large (derived) marnrrals (Schad 1977) and in primates (!'erhr-rlst

Martin Lockley et al.

Figure 9.12. Dinosaur forelimbs. (Top left) Juve-

nile Gallimimus (A), Or-

nithomimus (B), Struthiomimus (C), and Gallimimus (D). (Top ht) Tyra n nosa u roid ea :

rig

hypothetica I j uve n i I e Al -

bertosaurus (E), adult Albertosaurus (F), and

ls

's.'a'

I L

Tyrannosaurus

ar a\

(G).

(Lower left) Dei nonychoM

sau rs: Ba m bi ra pto r (H), Velociraptor (l), and

Deinonychus rig

(J). (Lower

ht) Ceratosa u roi d ea :

ph rosau rus (), Cera tosaurus (M), and Carnotaurus (M. Cf. Figures 9.7, 9.8, and 9. 11 for E la

correspond i ng 2nd

aT Fldt tra I

h i nd I i mbs I < 7Ar

bird forelimbs.

2003). In si-rort, it is a characteristic of all these major groups of vertebrates that tl-re more derived and more obviouslv peran-rorphic forms have proxima1 rather than distal limb ernphasis. Put another wa)', the inner organs are more developed.

It is irnportant to stress that compensation principles, balancernent of organs (or heterochronic trade-offs) evidently apply' at manl' different levels of morphological organization. Thus, n'e can move from comparing proxin'ral versus distal organs r,vithin the hind limb or forelimb in differer-rt species (cf. Miclclleton and Catsel'2000), or to comparison of limb proporiions at different stages of development (Reisz et al. 2005). This inevitably leads to comparisons of adjacent organs such as head, neck, and forelimbs. Whl for example, anong manv saurischians and some birds do we get verv long-r-recked forms with relativell'srnall heads? Wh1'are such morphologies less u,ell developed in tl-ie vast majoritl, of ornithischian dinosaurs and rnammals? Put another u'a)', u'hy do some saurischian (notabll,theropods like T. rex) hal'e ar-r opposite or rec\;rocal organization (large heads ar-rd relatively'short necks)? And why do some forn-rs have sr,rcl-r diminutir.'e forelirnbs, yet lvell-developed hind limbs? Given that clevelopmentaliv the forelinrb bud originates at the junction betu'een the neck and trunk (cervicals and dorsals; Carroll 2005), the possibilitv of a developrnental explanation must be explored. According to Russeil (1970) and Long and \ Ic\amara (1997), the anterior part of the jr-rvenile tvrannosaur bodt'is relatirelr small. The juvenile

Relationships between Head, Neck, Front Limbs, and Other Anterior Organs in Theropods

head is relatively small compared u'ith the adult head. and the front lirnb is Why T'1r2nq5lurus rex Had Puny Arms

149

portions of proximal and distal wings rn modern birds, after Middleton and Gatesy (2000). Note polarity between small (paedomorphic) forms with distal emphasis and large (peramorphic) forms with proximal emhhrcrc

I f

tstdttra9

)))))) lt @@@@@@@@@@ panot Murre

Osrich Krwi Rlca

Penguin

A.lbatross

Hombill

Swa.llow Swift

t/

relativell sm:rll cotnparecl n ith the hincl linb. Assuming this reconstructiorr has sorne nterit, the situation is the reverse or adult organization, shon'ing hon'tl-rere \\'as a progressive :rnteriorization of grou,th. or shunting of grou'th frorr rnore posterior to more anterior organs (Fig. 9.9). [{on'ever, this reconstruction of a jur.cnile is entirelr'fu'pothetical, :rnd ri,e can gain better irsight into tvranrtosaur ontogeni frorr recent studies bt Carr (1999) and Currie (2003). For example, the lightlr built albertosaurines have "longer, tibiae, longer nretatarsals ancl longcr toes" (Currie 2003, p. 663). These all point to cnrphasis of clistal linb elerrents in the snraller, lighter, more gracile group, as conpared r.i'ith proximai limb elements in the robust tvrannosaurines. Carr (1999) studied onlr"the cranial morphologr" btrt ner,crthelcss shon'ed

the shift froln a narro\\', elongatc gracile skull in earh' ontogenr' (stage I) to one that is robtrst, shorter, and clccpcr in latcr stages (stages 3 and 4).'l'hrs shift is :rccornpanied bv the loss of rostral (distal) end of the marilia and a n'iclening of the proximal portion of the skull, all of n'hich l-rave far-reacl-rir-rg implications for tvrannosaurid taxonornr' (Carr I999). As noted prer.'iotrsh; such shifts fall uncler the general label of anteriorization (or enrphasis of proximal organs) tr,pical of large clerived fomrs rrr rrrost r.ertebratc clacles (Lockler' 1999a, in press). Incleecl, Carr (1999) goes

hint a re capitulation br, corrparing jur,enile tvrannosar-rrs u ith othcr ruore distantll relatecl prir-nitile theropods, u'l-rich had long ancl narv611' (rather tlian broacl and deep) skulls. This gener:rl pattern is clearlv so far as to

supportecl bi' the discoveri of sniall, gracile, long-snouted basal tvrannosauroicls ltke DilorLg (Xtr et al. 2004) and ()uanlong (Xu et al. 2006). TliLrs, it is perhaps no strrprise that as derir,ed tvrannosaurs, ceratosaurs, brachiosaurs, ornithopocls, ceratopsians, and pterosaurs became larger than their

ancestors, thev cleveloped large heads atrcl exaggerated heaclgear as their er,olutionarv ci.'cles culminatecl. Obserr,ations br, Hone et al.(2004) liar,e rer.i',.ecl the idea of Cope's rule and the increase in evolutionari'tenclencl' touard l:rrger size through tinic. hrdeecl, it appears that tl'ris tendeno rs prevaler-rt in manv differcnt clinosaur groups? and is "r'rot liniited to arn

particular subclacle" (Hone et al., 2004, p. >90). These autl-rors note that the tencleno, is particularlv pronotrnced in the Sauriscl-ria, and thel single out the ti'rannosaurids as a prol]ounced example. We infer that the correlation bctncen largc size ancl largc heads is notetorthr', so there is likelv a

connectiorr betri'een Cope's role ancl pronouncecl anteriorization. As s'e follor,r'these ritrole$odv anteriorization trends, n'hich have the most obviorrs manifestations in the heads of the large clerivecl species, it is

150

Martin Lockley et

al.

necessarv to keep track ofsirnilar fractal patterns that affect the individual organs such :rs linrbs, ar-rcl their inner (prorirnali ancl outer (distal) elements

(Figs. 9.5-9.13). In tliis regard, it is no coincidence that tirere is a distalless gene that controls or affects the der.elopment of clistal lirrbs in a n'icle rarrge

of anirnals species, and that it is so named because it inliibits the grori'th of distal lin'rb elernents n'hen mutated (Carroll2005). This is the opposite of the rnalfornations caused bv the fertilitv drug thalidomide, ri'l'rich often attackccl the prorimal portion of the limb during a critical gron,th stagc of the fetus-that is, 20 to 36 clar,s after conceptior-r (Gilbert 2000). Because the relatir.e gron'th of distal portions of the limb is dependcnt on n'holebodl'size-as shou'n in the case of the sauriscl-rians-n'e can infer that the rclative importancc of a distalless organizing principle (or its equi','aleirt gene) is correspondinglr.,erpressecl. It is assumed that the rranifestation of nlorc or less distal gronth is linked to heterochronic der,elopn-rental dr. nalrics. Srich clvnanics are directlt' ar-rcl ir-rclirectlr,, explorecl in a recent studv of prosalrropod errbrr,os bv Reisz et al. (2005). Thev concluded that the jui'eniles had largc hcads ancl forelimbs, but that negative allornerrv cluring postnatal clevelopment reduced forclimb grow'th and grow'th of the head (relatir.'e to the neck). Indeed, thev sl-row,ed that relative io the femur (taken as the standard), the tibia anci dorsal vertebrae gren' isometricallr', but that there n,:rs strong positii e allometrv in cervical 'n'ertebrae and negative allonietrv in the skull.'l'his stresses tlie dr,,namic grori'th compensation betu'een thc neck and the skuli. as discussecl herein for coelLrrosauriaus. Strch dvr-ramic corrpensations ha','c far-reaching irnplications.'l'hus, Reisz et al. (2005) inferred ihat giant sarlropods likelr,evolved :rs a result of the opposite process in li'hich forelimb gronth n'as not suppressed-that is, through paedorriorphic retentioli of earlv ontoger-retic features in the ailult (cf. Bonaparte ancl Vince 1979). Thus, the sauropod mar,shon' manr.features of an o\rergro\\:n prosarlropod embrvo. The poiaritv betneen lorrgnecked sauropocls n,ith small hcacls ancl long forelinrbs, and shorter-necked prosauropocls n,ith shorter forelimbs ntav be developmentallr. convergent r.r'ith the polarities seen irr theropocls. We hai'e alreadv arguecl that tl-re head is the rnost anterior organ of the bodl'and is cl-r:rracteristicallv largest in highlv derirecl forn'rs tl'rat shon'extrerne encephalizatior-r. Here some qualification is necessarl'to distinguish betu'cen absolutc and relative head and/or brain size. For examole. absolute head encephalization is generallv less pronounced in tl-ie saurischian than in the ornithischian dinosaurs (Locklev 1999a), as seen in a con-rparison betu,een sauropocls and ceratopsians. Holr,ever, as shourr bv the fanrous erample of encephalization inTroodon (Russell ancl Seguin 1982), a small animal ma)'have a relatir,elr'large head ancl/or brain relative to bodr sizc, e\,en if the absolute size is not large in comparison u itl-r other, mucll larger dinosaurs. As noted above, there is a polaritv in he:rd-neck relationships in manv dinosaur groups (r'ithin the tl-reropods, u'ithin saurischians, ancl u'ithin the Dinosauria as a u'hole). T'his suggests a fractal recursion of grou'th dvnamics and/or subsequcni functional adaptations. For eranrple, arnong certailr grorlps of Sauriscl-ria, (e.g., the srlaller, gr:rcile tireropods, ontithoninids, and sauropodorriorphs), the neck can be verr der e loped {elongate) nfiile the

LARGA HEAD Short neck

Small head

Short Arms

LONG NECK LONG ARMS

Figure 9.14. The polarity between small (paedomorphic) taxa with small heads and long necks and forelimbs and large (peramorphic) taxa with reci p roca I or co m pensatory organ ization (large head and short neck and forelimbs) is well demonstrated by the respective ce

ratosa

u

ri a n

s (Coe I o -

physis and Carnotaurr t<) anrl fhe ra
col

e u

rosa

u

rlJrr!!,'v

rians (O rn i -

thomimus and Tyrannosaurus).

head remains relativeli'snrall. T1-ris characteristic is also t-vpical of uranv bird grolrps (as cliscussed belou' in relatior-r to Hoxc6). Bv contrast, the neck rs never hvperdeveloped in the large ornithischians, although it is urore developecl in large haclrosaurs and iguanodontids than in other groups, ancl e'n'erl

in srraller forms, it does not reach exaggerated proportions. 'fhus, the n'hole tendenc,r' torvard anteriorization is less developed in the sar-rrischian heacl than in that of on-rithischians (Lockiel' 1999a), although in conpensatiort, tt is more clevelopecl in the saurischian neck.

If n'e just limit our vien'to the theropo
If ii'e limit onr vierv to the morphological variatiorr lr'ithin the genus Coelophysis (Colbert 1989), r,vhere 2 din-rorphs are recognized, rve find that the largeJ-reacled, robust form has relativelv shorter forelirrbs, n'hereas the sn'raller, gracile form has relativel1, longer forelirlbs (Lockle1'and Kukihara 2005; Fig. 9.15 herein). Note here that the differences betrveen 2 clin-rorphs of the same species are much less tl-ran betneen different genera nithin larger clades. Also, given the similarit,v in size (Table 9.1), actual sizes are given rather than relative proportions, except ir-r the case of tl-re cervical/ dorsai ratio.'I'hese corripensatort' relationships betu'eett adiacer-rt organs in Coeloph,tsis extend throughout the u'hole body so th:rt the robust form has lor-rger hii-id legs and a shorter bodr', lr,l-rereas the gracile forrr has a longer bod-v and shorter hind lirrbs. As pointed out bl Locklev (1999a), srr-ra}ler, n-rore primiti'n'e clinosaurs n'ith posterior er-r'rphasis have narrorv, elongate bodies and short limbs, u,hereas larger forms n'ith ar-rterior en'rphasis ty'picalh' have foreshortcned bodies ancl longer limbs. This generalizatiott corresponds to the case of the Coelophysis clirnorphs and appears to be supportecl bi'the obsen'ations of Bakker and Bir (2004, p. 303), ivho noted exactl,v the samc trends in "progressive shorter.ring of the torso" in the sequertce Ceratosaurus-Allosaurus-

152

Martin Lockley et al.

Figure 9.15. Morphodynamics of Coelophysis dimorphbm based on comparison of the robust from (AMNH 7223) and the gracile form (AMNH 7224). Note the alterna-

tion of long and short organs (i.e., natural body
haacl narL

trunk, tail, limb, foot)

Coelophysis baud AMNH 7223 and MCZ 4327 robust

short

showing an organized, reciprocal pattern of heterochronic compensation. Ultimately the robust form has more anterior emphasis and longer limbs, and the gracile form has posteilor emphasis and short Iimbs. Thus, one is the perfect reciprocal of the other (after Lockley in press)

Coelopttysis baun AMN H 7 224 gracile

Corgosaurus and correlated it rvith "ir-rcreasingly sharp S flexure of the neck," wl-rich is also a n'ranifestation of foreshortening.

Clearll; changes

ir-r

morphological development in

an1, organ have a

cascade effect throughor,rt the body, ancl thev certainll'have a compensa-

tory effect in adjacent organs. This is the dvr-rarnic essence of the morphodynamic paradigm. It has been shou'n that specific Hox genes plal'a role in these changes or sl-rifts. 'fhe anterior expressiorr of Hoxc6, for example, plavs a pivotal role in defining the transition frorn cervical to thoracic vertebrae. This bour-rdary is closely associated rvith the grorvtl-r of forelimbs. As sr-rmmarizecl by Carroll (2005), the rr-rouse, chicken, and goose have short, medium, and long necks rvith T, 14, and 17 vertebrae, respectively. Each, it can be argr-red, has increasinglv r,r'ell-developed fore limbs. Bv contrast, according to Carroll (2005), the snake has no cervicai vertebrae and hence no neck or forelirrbs. It is all head anci exaggerated thorax (Fig. 9.16). These shifts in organization in the central and anterior part of the vertebrate body' may give us clues to the rnorphodvnamic organization rn saurischian dinosaurs ar-rd the likely relationship to Hox gene expression. Thus, the polaritv betr,r'een the theropods s itli short necks, large heads, and small forelimbs is contrasted u'itl-r the sauropods that have long necks and forelimbs but small l-reads. T. rex,like rnost theropods, has 10 cervical

WhS

-,')^' -SaJrus

rex Had Puny Arms

153

Skeletal Element

AMNH 7223 (Big Head)

AMNH 7224 (Small Head)

Skull-spine to caudal 17

1838 mm

1761.5 mm

Skull length (mm)

265 long

222 shorl

Neck (cervicals)

485 long

405 short

Trunk (dorsals)

425 short

455 long

Cervical/dorsal ratio

Long neck (1.14), short body

Short neck (0 89), long body

Sacrum

'120

Proximal tail (caudals 19)

291 long

279 shorl

Midtail (caudals 1'l-17)

252

252.5

Distal tail

822.5

Missing

Forelimb total

354.9 short

412.9 long

Scapu la-coracoid

'134

short

156 long

trUMCTUS

'120

short

134 long

Radi us

65 short

89 long

Metacarpal 3

35.9 short

40 9 long

Hind limb total

559 long

549 short

short

148 long

Femur

209 long

203 short

Tibia

224long

221 shorl

Metatarsal 3

126 long

125 short

in the sauropods, there are

to

Table 9.1. Measurements

and

tvt tvtalvt vt 9qr t) vt z

cervicals ancl9 to 14 thoracics (Fig. 9.16; \L'eisharnpel ct al. 2004). 'l'his polaritl' (long neck-long forelimb-small head versus short necksl-iort forelinb-large head) recurs fractallv ri ithin the coehrrosaurian theropocls (tvrannosarlr versus ornithorrimicls) :rnd n'ithin the sauropocls (diplodocids versus brachiosaurids). Hou'ever, it is irrqtortant to note that ri'ithin tlre nonar,.ian theropods, the number of cerr.'ical and dorsal r.,ertebrae do not varr mtrch. On the basis of analogy n'ith rrodem reptilcs, birds, and nramnrals, n'e corrld assrlme tl-rat the expressiorr of Horc6 is constant n'ithin the theropods (althoLrgh it is knori'n to varv in birds). Hori'evcr, among the satrropods, we can infer that Horc6 erpression is more variable becausc of the greater rariabilitr (disparity) in number of neck vertebrae (Fig. 9.16). \\1e speculate that this is consistcnt n'ith the model of greater disparitr,of form in large, clerived clades such as sauropocls, as compared r.i'ith le ss clisparate bLrt rnore dir,erse clades such as theropods. Fbr exarrple, \\/eishampel et al. (2t10.1) list 2 n'ell-knon'n theropod genera for each knorl,n sauropod genus. Recent finds

Coelophysis Dimorphs

Note.-Data from Colbert (1eBe).

13 thoracic'",ertebrae, n'hereas

12

19

have also tencled to emphasize sauropod disparitr', as in the case ofAnzclrgo-

s(lurus, r'ihich has an ertraorclinarv eraggeration of the neck in tlie forrn of bifurcated neural spines (Salgado zrncl Bonaparte 1991), and the short-necked sauropocl Brachttrachelopan (Raul-rut et al. 2005). As alreadr, noted br., Lockler, (1999a), these are rracromorphoiogical A-P

polarities that are obr,iouslv convergent li ith the Schadian rnodel for manrlals. N'loreorer, thei'provicle stror-ig strpport for the idea that saurischians (especiallr theropocls) are closel'n'relatecl to birds, becanse it is n:rinlr.'in this

1<)

Martin Lackley et al.

chick

goose theropod short neck Diplodocus

@

long neck

neckyertsbrae

group, not in ornithischians, tl.r:rt the r,ariation in r-reck and forelirnb developrrient is so pronounced. Bv contrast, in general among ornithischians, the

Figure 9.16. The relationship between the cervi-

necks are sl-rort (as fen,as 7-8 cen,icals in prirnitir,e forrns ar-id np to no more

cal -thoracic verteb ra I

than l0 in most other forrrs, ercept in the iguanoclontids and hadrosaurs, u'here the nnrrber nrav reach 1l-15), but it is in the l-reads that we see the

boundary in modern snakes, mammals, and birds as a reflection of the anterior expression of Hoxc6 (modified after Carroll2005), with inferred arrangement in

n'iost enl:rrgement and elaboration, especialh., in deril'ed forn'rs.

'l'hus, ri'e have a plausible explanation for the small arms olT. rex and the long ne cks ancl forelirrbs of coelurosaurs and sauropods that is entirely consistent ri ith the broader pattern of Hox gene (Hoxc6) expression ihror-rghout 3 ma jor classes of extant vertebrates: rnarrmals, birds, and reptiles (sensu Carroll 2005). Although it is tenpting to credit Hox genes u'ith providing the ultimate explanation for sr-rch distinctir,'e rnorphological traits, r,r'e have alreadl' strggested that Hoxc6 does not provicle a compeliing causal explanatiolr for tl.re long-neck versrrs short ne ck polaritv within the theropods. Evo-der.'o propone nts aclmit that the actual cause of tl-re switcl-ring on and off of honeotic genes like Hoxc6 is still a cor-nplex nvstery. The gene has a pivotal relationship in dcfinir-rg the morphoiogical boundary betiveen 3 organs (neck, fore limb, and thorar or torso). but is only or-re of n-rany dynanic factors that influence the nrorpl-rologl of these organs. Nlloreover, Hoxc6 is depenclent on other genes to snitch it on or off. If n'e are correct in ir-rferring the role of this gene in inflriencing ditferential orgar-r development betlr,een tl-reropods and sauropods, and n ithin satiropods, br-rt noi w'ithin tireropods, \\:e can ask u'hether tl'ris ge ne plavs a role in the de",elop-

saurischian dinosaurs

(theropods and sauropods), based on vertebral formu I a, for com pa rison. Theropod formula (10c + 13d) is constant, but sauropod formula varies between short-neck and

long-neck extremes. Numbers at the base of the 4 right columns indicate head, neck, and thorax totals for dinosaurs. Numbers in the 4 leftmost columns are after Carroll(2005).

155

ment of the srnall arrns ofT. rex (andCantotaurus). For cor-rsistency, \\re can point to the recursive natnre of the morphological changes seen lvithin the theropods (and in the birds, r,,'here Horc6 cloes plal'a role in differentiating the vertebral morphologv of major gror-rps) and infer that some sirnilar rnfluence is at work (Fig. 9.16). These argun'rents favor an understanding of dinosaur rnorphologl,in the context of the developrnental morphodvnamics that affected these organs.

Previous

Viewed from the abor''e perspective of linbs as organs in complex s1,stems, rve must tr1'to understand their morphoiog,v in relation to adjacer-rt organs. Thr-rs,

Interpretations of T. rex Forelimbs

given the broad perspective demancled bl,modern biological thinking, the idea that T. rax forelimbs served sorne specific indir,'idual pllrpose lnily rlow be questionable. Ner.'ertheless, as pointed out bv Carpenter and Smith (2001),

the qtiestion "What, if anvthing, did TyrannosatLrus do n'ith its punv front legs?" has beer-r asked on nanv occasions (Gould 1980). Thr-rs, althor-rgh tl-re

question remains w'hl ihe arrls are "outrageouslr"' putr1, (Fastol'skv and Weishan'rpel 2005, p. 2Bl), it is likeh'the rvrong question, at least frorn the developn'rentrl 1,lg11,point. Preferabll; n e should be thinking about how inl-rerer-it morphody'namic organization leads to exaggeration of some organs and reduction of others, ar.rd hon'these patterns ma1; fs recognized as a staggered or organized seqllence of morphologies u'ithin clades. Nllanl, ths611. s of T. rex arm functiorr have essentiaiii' been negative il the sense that the-v point out that the arrrs could not function to reach their

mouth, or \l,ere unlikely to be of much use to push themselves up from a prone position (e.g. Neu,r-nan 1970; Fastor,skl,ar-rd Weisharnpel 2005). Positive functional theories include the iclea that the arrns were strong and useful for ch-rtching prel'(Carpenter and Srrith I995, 2001), or ihat thel servecl sorne sexual function (Osborn 1906).

(l9BB, p. 120) statecl that "much specr,rlation has been clirected towards the use of these forelimbs . . . fbr-rt that] . . .this obsession is rnisplaced. Tl-rev rvere not inportant to their o\,\,ners, so ther,should not be irnportant to ns." Frorr a functionai perspective, \,r'e agree, but n'e hold that frorl tfre perspective of the con-rpensation clvnamic, the sn-rail size is der,elopmentalll' significant. Paul (1988, p. 320) also noted that "in Tyrannosaurus and even more so in Albertosaurus the forelimbs became er,'en smaller with time and were on their u'av to complete loss." This statement suggests some sort of intrir-rsic biological dvnar-nic in the T\'rannosauridae, although no explicrt cause is suggested. (Complete loss offorelimbs does occur in reptiles funakesl Par-rl

in conjnnction rvith an excessivelv anterior expression of Hoxc6.) It has also been noted in other tetrapods, from Paleozoic lepospond,vls to Mesozoic and modern squamates (Caldrvell 2003, p. 573), u,'here it is clearlv been tied to "developrnental genetic models . . . associated n,ith morphogenesis" and not prirnarilv to function. Paul's avoidance of a functional explanation is perhaps sy'n-rptonatic of the evider-rt difficulties encor,rntered u'hen trf ing to find one that is corrpelling. 'fhis ma-v accourrt for the fact that even some popular treatments olT. rex largell'avoid the subject (Horner ar-rd Lessern 1993).

156

Martin Lackley et al.

Ali interesting strggestion r,vas made br Fastovskr, ancl Weishampel (2005) that the sinall anns helpecl to balance the big head and prevent the anin-ral from tipping forn'arcl. '['his bionrec]ranical suggestion cloes ini'olr,e the principle of comper-rsation, br-rt it is distir-rct from our strggestion that the conpensation is clue to the inherent (formal) increase in anterior er.nphasis rvithin tl-re head as another example of a cephaiization trencl.'l'he ide:r of biomechanical functior-r is trncor-tvirtcing because aninals are not rnachines, ard to be consistent, the sarne argnment n,oulil need to be applied to all -l'hus, other dinosatrrs anci their organs. bipcclal animals n'ith large forelimbs (inclucling nost other theropods) might be interpreted as having clevcloped such limbs in orcler to compensate for srrall heacls so as to avoicl falling backu'ard. Given the realitv of anterioriz:rtion trencls, it seems rnore parsirrolliotls to sin-rpll,infer th:rt some species \\'ere l-nore anteriorl' de'cloped tha' others, and that thc expression of morphological dir,ersiti' is an inherent propertl' of dcvelopment ri ithin a cornplex organic sr.stem such as :r cladepossibly a tvpe of t'ithin-clade homeostasis. When rl'e do this, and rihen n'e consider hoi'n'these various degrees or stages of development rlould be expresseci in clifferent organs of the bodi' rlhile obeving thc conrpcnsation principle, r'r'e quicklr' find that \\,e are looking at ihe t1'pes of morphologicai variation that ne find in nature-in this case, aurong theropods ancl saurischians (Fig. 9.1't).

Locklev (1999a), the Schaclian morpl-rod."'namic paradign allor,r's us to draw some compelling inferences about saurischian behavior and phlsiologt; ancl to understand their biological organization ri ithin tf ie contert of the irlrole clacle. For exarrple, srnall, prirrritive tl-reropods such :rs Coelopht,sis tl'picallv have short limbs and long, narron,bodies, tails, ancl feet. 'l'heir morphoger-resis inherentli'crnphasized the posterior organs; er,'en the ir teeth are l:rterallr'compressed and posteriorlr,'recun'ecl. Footprints and tracku'avs are also inherentlv r-rarrou,, and thev sometimes sholv ei'idence of the animals sitting back on their posterior organs (metatarsals and ischia).'l-rackri'avs also sr-rggest that thev rroved quicklr,' (Farlon' i98i) but li'ere t1'picallv not gregarious. Thel probabl-v hacl large er,es and relativeh'large brains, perhaps riith hincl brain ernpl.rasis. All these characteristics are convergent n'ith rodents to varving degrees, ar-rcl although thev do not suggest a close biological affinin', thel'suggest a nrorphoclr'rurmic, and presumablr'genetic, organization that was con\rergent u'ith and corrnected to characteristicallv srriall bodv size. Aclditionallli their predonrinanth paedomorphic characteristics probablv indicate tirat tl'rev had relatir,elv short life spans. Bv contrast. largc preclominantll' peranrorphic) derived theropods like 'I'. rex har-e generated much debate regarcling their locomotor capabilitres (speed), diet, nretabolisn-r, and aggressive, predator\, and/or scar,enging behaviors (Paul l9E8; Horner and Lessern 1993t. \lorpliologicallr, thev tend to be longer lirnbecl (hincl lirnbs) sl-rorter. n iclcr torsos and some\\'hat "r,itl-r shorter tails (Bakker and Bir 200'l). Their teeth are also much n'ider (less narror,r), and in sorne large theropods, there is er ide nce of a li'ider trackn,ay' (Locklel' 2001). Thev also derelopecl larger head.. sonietinres uith srnall As noted by

{

Discussion

crests or lrorris (as inCarnotaurus). There is also much evidence from healed and resorbecl bor-re that tl-rer., had active metabolisn-rs, nfiich mav u'ell have permittecl them to scavenge old meat. All these characteristics place large forms like T. rex at w'hat Schad (1977) calls the rnetaboliclimb encl of the theropod spectrum. Horvever, \\'e can go one step further and sav that n ithir-r

the coeh-rrosaurs, it appears that the tr,'rannosaurids represent the nore nretabolic exaggeration ancl the ornithomin-ricls express the greater lirlb ernphasis. Hone et ai. (2004) even infer that there mav be an ideal rrean dinosaur

bodr,size (rvhich ther,'specifi' as 7.6 m in length) abor,e u'hich il-rere is a strong tendenc-v torvard Cope's rule. Thev even use tire chaos theorv netaphor ofa possible "attractor" for such "an apparent stable equilibrium body size" (p. 594). Thus, thc-v not onlv impl1' that nrorphologv u'ithin clinosaur clacles ar-rd subclacles has plastic ar-rcl cli'nanic clualities that express consider-

dil'ersity of forrn during the course of dei'elopment and e',,olution, but thel,also infer that there mav be sorne sort of larger organizational patterning arouncl hon-reostatic equilibrium, or an attractor. In the context of our disctrssion, Jl rex, like rrost large derir,'ed tvrannosaurids, is on the large peralrorphic side of the equilibrir,rrn poini, r'"{rereas n.rost small gracile ornithomir-nrespect to overall size. ids are on the srnall paedorlorphic size "r'ith A brief perspective on sauropod characteristics provides a sense of the ablr,'

polaritr inherent in the lrorpl-rocivnamics of saurischians as a ufiole. Sauropods n'ere all large ancl qr-raclrupedal, n'ith long necks. Thev r,ere predominantll,perarlorphic as a resr-rlt of acceleratecl gror,r,th (sensr.r Erickson et al. 2001, 2004) and 1ikel1, long lired. Thev mav hal'e been derived heterochronicallv fron prosauropods bv retention of jr-rvenile prosauropod proportions

durir-ig prolor-rged grou,th (Reisz et al. 2005). Smaller primitive forms such as the diplodocicls had a nore posterior and narrorv en-rpl-rasis (iong tails, sr-r-rall forelinbs and skr-ills, and narron,trackwar"s), derii'ed forms like "r4rereas the brachiosaurs and titanosaurs had greater anterior ernphasis (short tails,

longer necks, somen,hat larger skulls, longer forelin-rbs, and u'ide trackrvays; Farlou' 1992; l,ocklel'et al. 1994b). All appear to har.'e been gregarious ancl u'ere vegetarian, r,r'ith rounded teeth. In comparisor-r r.l'ith their theropod cousirrs, the sar-rropods u'ere larger or,erall (rnore peramorphic), ri'ith greater

metaboliclirlib

en-rpl-rasis (r,egetarians

li,'ith erect limbs), thus suggesting con-

\iergence r'vith ungulates. ('fhis rnorphodvnamic trend ton'ard ungulate con\iergence becornes even more pronounced in clerived ornithischiar-rs; Locklel'

I999a.) Sar-rropods also reveal a longJimb, short-foot design, compared lr,ith the relativelv short-lirab, long-foot design arnong rnost tl-reropods, especiallv the rnore primitive forms (Fig. 9.5).

'l'he irnportance of eniph:isizing these polarities and inherent cornpensations in the context of heterocl-rronic langu:rge is to stin-rulate interest and

observation ofthese recursive fractal patterns, and to obsern'e dinosaur clades as con'rpiex organic systeins, like cells or rvhole individuals, but on larger scales. Agair-r, as scier-rtific language evolves, dr,namic terr-r'is like morplnlogical equilibriunt point or attractor n'ia1, replace the ntore static concepts of mean or (l\terage and allou'r-rs to see clacles more like dr''nan-ric or homeostatic superorganisms, and less like a classification of separate, inclir,iclualll'ciifferent fornrs. The evo-devo paradigrn supports such holistic morphodinamic

158

Maftin Lockley et al.

thinking, but it essentialll'proceeds from the bottorn up (molecules to cells and embryonic rnorphologie$. The fossil record offers a clifferent tvpe of macromorphological evidence that requires us to u'ork from the top dolvn. This is where the n-rorphodl,'nan-ric paradign-r can be most r-rseful if sufficiently understood. Not onlv does ii help us ur-rderstand the inherent, fomral growth dynamics that lead to differential organ ernpl-rasis (e.g., heads, necks, and limb$, but it also gives valuable clues to horv these relate to phy'siology and behavior.

Hou'can lve make

sense of all tl-rese parallel and equal and opposite directional morpl-rodynarnic grovn'th trends? There are clear recursil'e patterns. During or-rtogen,r,; manv growth trends proceed in the A-P direction, also known as the cepl-ralo-car-rdal directior-r (sensu Kingsbury 1924; Verhulst 2003), and by definition, as an organism grol\rs, it gets older. Does this mean that growth in the opposite direction (P-A) somehow represents a juvenilization process? There are many lines of evidence that suggest that during phylogen,v, descendar-rts often begin to look more like juveniles representatives of their ancestors. Thus, embryonic apes look hr-rinan (Verhulst 2003), and rnanv birds resemble juvenile theropods. There has been much debate on this topic (Could 19 r'7, 2002), which is or-rtside the scope of this chapter to deal r,vith in cletail. Nevertheless, the large head is characteristic of early embryological development in most vertebrates, which sr-rbsequently have to grow into their bodies, so that tl-reir heads get relatir,ell'smaller during ontogenv, even though they grorv larger in absolute terrns. Thus, the long-term evolutionarv trer-rcls (correlated progressions, sensu Kemp 1999), which have led to an anteriorization or encephalization in manv groups, suggest a ty'pe of progressive juver-rilization (Sr,rchantke 1995). Given the forrnative importance of early ernbr,vonic development ir-r sl-raping tl-re morphologv of ach-rlts, it makes sense to consider that the heterochronic shifts that allow increased developn-rental activitl'earlv in ontogeny n,ill allorv for greater evolutionary flexibilitv and novelty. The stiggestion that such jtrvenilization (paedornorphosis) has played an important role in evolution is familiar to str-rdents of heterochrony and n'rorphody'namics (Gor-rld 1977; Schad 1977; N4cKinney and McNamara I99l; N{cNarnara 1997; Verhulst 2001). We conclude that such morphocll,narric trends likelt' influerced dinosar-rr phvlogenr,i as the_v have been inferred to have done ivith other vertebrate groups. Given that all species display a mixture of perarnorphic and paedorrorphic characteristics (McNamara 1997), as in the case of the ostricl-r, which is peramorphically large in terrns of its rvhile bodv but pedon-rorphic in terrns of its juvenile plurnage ar-rd partial nakedness, it could be that T rex was the coelurosaurian version of tl-ris "overgrou,'n babr"' phenomenon: i.e., peramorphic in or.'erall size but paedomorphic in the sense that it had a big skull. We r-rote in the case of tr,rannosaurids that recent studies make increasing reference to }'rypern-rorphosis (Carr 1999). peramorpl-rosis (Xu et al. 2004), and acceleration (Carr 1999; Erickson et al. 200,1). We suggest that this rer-rerved interest in heterochrony is a healtlir sigr-r that we are beginning to better understand the developmental clvr-ramics of an extinct group of animals whose biologv cannot be studied clire ctlr.

159

Conclusions

N{ost functional interpretations of T rer forelin'rbs are sinplistic or Llnconvincing. No one has rnacle a conrpelling case tl-rat the arrrs r,iere usecl for rnating, ciutching, or getting r-rp from a prone position. Likelr,ise, the suggestion that small arrrs provided sone kind of biomecl-r:rnicai bal:rncing

nrechar-risrr to cornpensate for a large head is hard to prove. Honer,er, ne agrec that during all r.ertebrate dcl'eloprncnt. there is good evidence for the

so-called balancenent of organs. This prinarr. or formal developrnent:rl dr,namic nrar'lead to the sccor-rclar\,appcarance or rranifestiition of a furrctional or biomecliar-rical compensation. Nlorphocll'namic studies of mamrrals and diiios:rLrrs suggest that ue can trace A-P andior P-A currents of macromorphological grori ih expressed as relatir,e eraggeration or reduction of organs. Sucl-r rnorphodvnamic organization is inhcrer.rtlv heterochronic ancl generalli,emphasizes posterior clevelopnrent in snall hnainli paedomorphic), prinritive organisrns and anterior emphasis in large (predominantlv perarnorphic), derived fornrs. On tlre basis of such a paradigtn,T. rex atxl Carnotaui"us \\,ere the largest ancl rnost clcrir,ccl (ar-rteriorizecl) taxa in their respectir.'e clades (coelrrrosaurs and ceratosanrs), and ther,can be comparecl rvith their nore primitive relatir.es in these sarne clades lr'here morphological enphasis is centered more in the neck and forelirnbs. We use the compensation principle, n,hich is also inhcrentlv lieterochronic, to argue that the small l-read, long neck, and long forelin'rb versus large head, shori neck, and short forclimb polaritr, repeats :rt rr:rnr' ler.els in the taxonomic hierarchv of saurischians (ancl other ciades), and it is thus an example of lauful or ordered patterning in rrorphodvnamic svstems linked to P-A encephalization. 'fhe evo-devo paradigm, ancl especialh' tl-re pivotal role of Hoxc6 nt defining the cen,ical-tl-roracic bor-rr.rclan'and forelimb budding, is cornpelling er,iclence tli:rt u,e can begin to understand differential theropod ar-rcl saurischian morphologv fronr these formal, cler,elopmental perspectives. During ontogcnv of vertebrates, tl-re w,hole bodv ar-rd its organs generalli' grou.'fronr anterior to posterior, although grorvtl-r ratcs r,'arr.from species to species and organ to organ. Hon'ever, during er.olution (phr'logen1 ), tl-iere are man'n,trends in the opposite (posterior to anterior) ciirection. 'fhrs is seen bv sorre authors as a juver-rilization trend. Recent ptrblishecl u'ork on tvrannosaurids frequentlv refers to 'u,arious forms of peranorphosis (acceleration and hl,permorpl-rosis) as irrport:rnt developrnental dr,'namics that help us integrate our underst:rr-rcling of thrs popular and ivell-studied group. S'1e suggest that these same clvnarnics recur fractallt'o'cn r,r,itl-rin species, but most r,isiblv tliroughout the Coelurosauria, Theropocla, Saurischia, and Dinosatrria, thus allou,ing ns to see these dvnanrics in a broader contert.

Acknowledgments

Thanks to the Biack Hills Geological Institute for the inr,itation to participate in the 100 Y'e ars of TvrannosdurLLs rer Svnrposiunr (June 10-l i, 2005). Tl-ranks also to Kenneth Carper-rter, Denver N4usenn-r of Nature & Science, for sr-rggestions regarding references, ancl his corrrrnents on the hvpothe tiMartin Lockley et al.

c:rl jtrverrile Albertosaurus restoration of Rr-rssell (1970). \d/e also thank Wolfgang Schacl (Witten-Hcrclecke Unir ersitr I and Ken McNamara (Western Ausiralia Nluseun-r) for helpful discussion of heterochronv and morphodr.narnics. We also thank Ken McNan-rara, Kenneth Carpenter, and Peter l,arson for their helpfr-rl and at tines challenging revien's of the chapter in manuscript.

Arthur,

\\i

2006. D',\rc' Thornpson and the theon, of transfornations. Na/ure

7:

.101-406.

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Hopkins Universitl Press, Baltimore, \{D. K. Nl., and Clatesr', S. \1. 2000. Tlieropod forelimb design and er.'olution. Zooktgical lournal cl' tlrc Linrcan Societt 128: l4c)-187. Ncn'rnarr, B. H 1970. Stancc and gait in the flesh-cating dinos:rur T\.rtuulosrtur us. B iolo gic al I otLr n rtl of the Linnean Socletr. Z : 1 I 9- I 2 l Norell, NI. A., Gaffner,, E. S., and Dingus, L. 199;. DiscoyeringDlnosarrrs. A. A. Knopf, Neu York. Osborrr, H. F. 1906. Tv-r(ultlosdlrrus, tJpper Cretaceorrs carnivorous dinosaur. Billetin of the Atnerican N'hLseunt of Natural H[stort, 22:281-296. Paul, C. 1988. Predatort Dhnsaurs of the \r\:orld. Sinron & Schuster, Neu York. Pike, A., \'ersus, L., and Alcr:rnder, R. \1. 2001 I ire relationship betueen linrbsegment proportions and joint kinernatics iirr thc hincl lirnbs of cluadrupeclal nrannrals. lournal of Zoologr 258:42,-4)1 Portnr:rnrr, A. 1964. Neli'Palfts in Bioloet,. Harper c! Rori. \c\\,'Ibrk.

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\\. \1., Remes, K., liechner, R., Cladera, C., ancl Puerta, P.2005. Discoverv of a short-necked sar.rropocl dinosaur frorr-r the Late ]urassic period of Patagonia. Nature 1)5: 670-6 i-2. Reisz, R. R., Scott, D., Sues, H. D., Ei'ans, D. C., ancl Raath, \{. A. 2005. Embn'os ofar Earlv Jurassic prosauropod dinosaur ancl their evolutiolan,significance. Nature J09: 761-764. Riegr-rer, M. 1985. Horns, spots and stripes: forn ancl pattern in marnmals. Onon N ature QLLarterb 4 (4): 22-35. 1998 Horns, hooves, spots ancl stripes: form aurcl pattern in rnarnrrials. P. I1 ,.-212 in Seanon, D., ar-rd Zajonc, A. (ecls.). Coethe's'lrat,of Science: A -. Phenonrcnologv of NattLre. State Universitv of Neri York Pre ss, Nen'\brk. Russell, D. A. 1970.'lirannosaurs frorn the L,ate Cretaceous of \\'estern Canada. Naticnal Musetnn of Natural Science Publications ht Paleontologt, l: 1-3'1. RLrssell, D. A., and Seguin, R. 1982. Reconstrr.rction of a srnall Cretaceous theropod Stenotnclnsaurus ineqtLalis and a hvpothetical dinos:ruroid. S1//ogeus 37 l-13. Saint-Hilaire, G. 1E22. Consid6rations g6n6rales sur la vertbbre . Nlernoires dtL L/ltLs€um d'Histoire Naturelle 9: 89-11'1. Salgado, 1,., and Bonaparte, J. Fl 1991. tln nuevo sauropoclo Dicraeosauridae, Anrdrgdsdun$ cazaui gen. et sp. no\'., cle la Forrnacion La Arnarga, Neocotniano de la Provincia del NerrqLrer.r, Argentina. Atneghiniana 28(l-'1): 333-7+6. Schad, \\l 19 t-7. NIan and Mamnnls: Towards a Biolog, of Fornt. Waldorf Press, Rar,rhut, O.

Neu.')brk. 1992. The Heterochronic Role of Evolution in the \/ertebrate Classes and the Hominids. Ph.D. diss., Unir,ersitv of Witten, Herdecke. -. Searron, D., and Zajonc, A. (eds.). 1998. Coetlrc'sWar of Science: APhenornenologl, of NattLre. State Ur.riversitl of Neri York Press, Nes' \brk. ShLrbin, N. H., and Alberch, P 1986. A nrorphogenetic approach to the origin ancl basic organization of the vertebrate linb. Evolutionart'Biologt 20: 119-3E7. Suchantke, A. 1995. 'l'he rnetan-rorphosis of plants as an erpression of juvenilisatiorr in the process of er,olution. P.4,--69 in Bockemuhl, J,, and Sr-rchantke, A. (eds.). Tfte Metarnorphosis of Plants. Novalis Eclucation Series, Cape Tori n, South Africa. 'l'hon'r, R. 197 j. La th6orie des catastrophes et ses applications. Reflexions sur Nouvelles Approches dans l'dtude des S1'sfdnres. Editions de I'ENSTA, Paris. Thoinpsor.r, DA. \\r. I9I7. On Crowth and Form. Canbridge t.hriversitr, Press, Cambridge. Verhr,rist, J.2007. Detelopntental D1,p6rl1rt in Humans and Otlrcr Prinntes. Adonis Press. Neu' York. \\hllenfand, \1. R., and Sevdoux, G. 2000. Polarization of the anterior-posterior axis of C. elegans is a rnicrotubule-directed process. Science 408: 89*92. Weishan.rpel, D. B., Dodson, P., and Osr.ndlska, H. (eds.). 2004.T|rc Dinosauria. 2nd ed. tlnir"ersitv of California Press, Berkeler". Xu, X., Norell N{. A., Kuang, X., Wang, X., Zhao, Q., ancl Jia, C. 2004. Basal tvranlosauroids from China and er,idence for protofeathcrs in trrannos:uroids. Nafure 431: 680-684. XLr X., Clark, J. \,1., Forster, C. A., Norell, N.{. A., Erickson, Cl. NI., Eberth, D. A., Jia, C., and Zhao, Q.2006. A basal tvrannosauroid dinosaur from the I-ate |rrrassic of China. Nature 439:71i-718.

164

Martin Lockley et al

Deinonychus

166

Christine

tipl

11 s116 Kennelh Carpenter

LOOKING AGAIN AT TH E FORELIM OF TYRANNOSAURUS REX

B

10

Christine Lipkin and Kenneth Carpenter

The large theropod T\,rannosaurtLs rexis the archetvpe carnivorous dinosaur ever since it'"i'as narned in 1905 (Osborn 1905). Even its nane, "tvrantlizard king," ir-n'okecl it as a top pre dator. Recent cl-raller-rges to its title as the largest terrestrial carnivore (e.g., Sereno et al. 1996; Calvo and Coria 1998) have not

Introduction

dirrinished its popularitr,. Osborn reasoned IltatTyrannosdurus was a predator on the b:rsis of its teeth. Coprolitic material, some containing fossilized soft tissue, srrpports a carnivorous diet (e.g., Chin et al. 2003), as does toothgrooved bones of prer'(Erickson and Olson 1996) and evidence of a failed attack on a haclrosaur (Carper-rter 1998) and ceratopsian (Happ this volurne). Although Osborn (1905, 1912) lr'as clear that he considered Tyrannos(tlLrus a predator, Larnbe (1917) dissented, consiclering t1'rannosaurids to

be scavengers instead, prinrarilr' becatrsc of the apparent absence of tooth w'ear. T\'rannosauricls as obligatorl,sca\,engers never gained popularitv un-

til recentlr; u'hen the hvpothesis

r",'as

reintrodnced

bl Horner and Lessent

(1993). Bv arid large, thougl-r ,'l),rannosaurus has been consiclered an active predator, although tl're mocle of attack rerrains controversial and includes

flank bite and nrn (Patrl 19E7), opportunistic (Farlorv 1994), and r-reck or snout crtrshing (Nlolnar 1998). 'l'he method of killing is assr-uned to have been the jan's, ancl the bite force has been variously'calculated or estimated to have been I 1,400 N (Rar field et al. 2001), 6400-11,400 N (Erickson et al. 1996), or even 183,000-215,000 N (I,Ieers 2002). As N,{eers has noted,

thc high forces are consistent n'ith either sca.,'enging or predation. In arguing against predation, Horner ancl Lesserr (1993) cite the shortness of tl-re forelimbs as being useless for

holding

pre1.. h-r

support of this posr-

tion, Lingharr-Soliar (19981 considered head shaking as a means of flesh remor.al from srnall prev ar-rcl clirect ripping of flesh from large prel: Carpenter (2002) has shorvn that u'ithor-rt exception, no theropod could extend its forelirnb berond the snout, thus liniiting its usefulness as a prey-grasping organ before the rrouth',r'as engaged (fig. I0.l). Does this mean, holvever, that the forelinrbs olT\'rannosaurus \\,ere as useless as portraled? Paul (1988, p. 320) considers such the question irrcler,':rnt: "the reduced size of the forelinlt shor.l's thev n'cre not important to their o\\'ncrs, so thev should not be important to r-rs." This position, supportecl bv Lockler et al. (this volume), is based on an urrsubstantiatecl assurnption ("n'ere not inrportant to their olvners"), ufiich is just ;rs useless as the untestable spectrlations of Lockley et al. (this volurne). In point of fact, Carpenter ancl Sn-rith l00l) conch,rded that the forelinb u as pon,erful, an interpretation prelioush made bi'Brown (19i5, p. 271;: "front limbs cxcceclinglv snrall but set for a polr erftrl cltrtch."

-'-

' :. ta "J

Anain at thp Fnrclimb

Figure 10.1 . Comparison

of maximum forelimb motion in 3 well-known theropods. None of the dinosaurs can reach its manus to tts mouth as a result of constraints in the shoulder (see Carpenter 2002). Note that Ty-

rannosaurus has the greatest range of retraction. Not to 167

scale.

Nen'material

our reassessing the forelimb of Tt,rannosaurus, and a stronger case is rnade for forelimb use during predation. Sorne of thrs nelr, material displal's pathoiogies, lr'hicl-r is irrportant because thev are a reflection of lifestvle behaviors (Rothschild and N,lartir-r 1993). As Paul has r-roted (this volume), Tyrannosaurus rrlL-.st have hacl a rough, active life. The materials used in this stud-v are as follon's: scapula of BHI 3031, DMNH 2827, and MOR 555; furcula of FMNH PR2081, N{OR 980, and TCN'{ 2001.90.1; hr,rrnerus of BHI 6210, FMNH PR208l, and NIOR 555; ulna and radir-rs of FMNH PR208l, N4OR 555, and MOR 980; and manus of FN,INH PR208l, MOR 555, \IOR 980, and BHI 6230.

New Information on the Pectoral Girdle and Forelimb

has led to

The pectoral girdle and forelimb of Trrannosaurus have been described by Carpenter ancl Snith (2001) and bv Brochu (2002). Since then, the furcula has beer-r described (Larson and Rigbr'2005), the third metacarpal and semih-rnate carpal have been found (described belorv), and neu'inforrnation is available for tl.re scapula and coracoid. To date, no ossified sternal plates are knolvrl, but these are predicted to resemble those of Gorg osdurus as described bv Larnbe (1917). BrochLr (2002) has discussecl the possibilitv of ossified sternal plates in Tyrannosaurus but came to no conclusion.

Furcula T'he fr-rrctrla of Tyrannosaurus, thc presence of lvhich lvas predicted by Carpenter and Srnith (200i), is non,knolr,r-r for several specimens (Larson and Rigby 2005). It is broadl,v U or boorrer:rng shaped (Fig. 10.2), with a rougl-rened sutural scar (acrominal facet) on the epicleidiurr for a ligamentous attachmer-it to tl-re acromion of the scapula (Fig. 10.3; see also belou). In birds, tl-re rami of the furcula have a nearh' circular or laterallv cornpressed cross-sectional geornetn' that alloivs then-r to act as a sprir-rg, u'ith laterally directed tensiorr added on the dor,','nstroke and medial directed recoil on the upstroke (Jenkins et al. 1988; Boggs et al. i997; Hr-ri 2002). In Tltrannosaurus, horvever, the furcula is clearlt'desigr-iecl to resist extrerne lateral forces: (l) the rami are anteroposteriorlr'flatter-red (cf. Fig. 10.2R G), thr-rs prohibiting laterornedial springlike action; (2) the rami cliverge, thus directing lateral stresses dou'n the shaft (Fig. 10.4A; and (3) the rarni cleepen distallv frorn tire epicleidiun-r and the furcula is deepest (thickest vertically ir-r the anatornical position) near the midline to counter the stresses directed do',vn the rami. In most theropods, tl-re furcula is nearl,v uniforn throtighout its length (see Chure and Madser-i i996, fig. 2, 3; Makovickl'and Cr-rrrie 1998, fig. l; Cr-rrrie et al. 2005, fig. 16.8; Larson and Rigbl' 2005, fig. 12.7). 'l'herefore, the great depth of the Tyrannosaurus fttrcula is unnsual and is clearlv adapted to resist stress. T'hree of the 5 knon,n T\trannosaurus furctrlae are pathologic (Fig. 10.2) and n,ere exarnined by cornputed tomographic scanning and X-ray. T\,"'o of tl.rern are missing portions of a ramus (FN,{NH PR20Bl fFig. 10.2A, Bl and TCN{ 2001.90.1 [Fig. 10.2E, F]), and 2 shoiv localized si,vellir.rg of the cortical bone (MOR 980 [Fig. 10.2D1 and TCN{ 2001.90.1 lFig. 10.2F]). Christine Lrpkin and Kenneth Carpenter

Er--r-r-f-r

G Figure 10.2. Furcula

of

Tyrannosaurus rex inrlt trla
thologies, including fractures (black arrows) and localized exostosis of stress fractures (white arrows). FMNH PR2081 in posterior (A) and anterior (B)views, MOR 980 in posterior (C) and anterior (D) views, TCM 2001 .90.1 in posterior (E), anterior (F), and lateral (G) views. Scale in cenilmeters.

Figure 10.3. Close-up

of

the epicleidial facet (arrow) on the dorsal edge of the scapula DMNH 2827 (A) and lateral view with the furcula articulated (B).

' ' '.o

Aodin at fha Forclimf

169

r,.",ere broken in life, n'ith subsequcnt ren-rodeling of the fracture surface. Surprisinglr', none shon a pseudoarthrosis joint at the site of the break, ihus indicating significar-rt displacenent of the broken portion, possiblv due to the contraction of the \,1. supracoracoideus brevis, ll'hich probablv inserted alor-ig tl-re ramlls. 'fhe anount of force needecl to break a ranus il,as calculated from the largest furcula, TCN,'I 2001.90.1. The fracture is 2.5 cru rr ide; hori ever, the bone is renrodeled on tl-re anterior ar-rd posterior sides so as to eraggerate

The missing sectiorrs of the rarni

the origin:il thickness of the bone. Therefore, the anterior-posterior tliickness is approximated from the r-uidarraged rarnrls, u,here it is has the sanre n'idth, ufiich gives:r thickness of LJ5 cm. The rarnus can be inodclcd as an ellipse; therefore the area of the break is gir,en bl the folloning:

A,8,,

(1)

or 2.6 cn-i:, u'here A, is the radius of the ramus u'idth and B, is the radius of the

thickness. Gil'er-i that the shear strength of living cortical bone is conser\,:l-

tivelr'-l0r N/cm:

(Cr-rrrev 2002), abor-rt 26,000

N

(i.e., 2652 kg of force) \\'as re-

quired to break the furcula. As seen bl cornputed tomographl, trabecular bone occupies a srriall portion of the norrnal ranlus, so it u as not considerecl in the calculations because it ri'ould hal,e recluced the fracturing force onlr,'slightlv. T\l'o of the pathologic furculae also shon'a characteristic bonv callus from a healed stress fracture (Rothschild 1988) located on the posterior side (Fig. 10.2D, F; Fig. 10.5). Stress fractures occrlr as a result of repetitive

loading on bone, u'hicli leads to mechanical failure and microfractr,rring (Resnick 2002; Rothschild ancl tr{artin I993; Rothschild 1988). Rothschild and Tanke (2005) and Rothschild and Nlolnar (this volr-inre) r-rote a high incidence of stress fractr,rres in the manual elements of tvrannosaurids. They also note,'Active resistance of prei'is required to or.'erstress the ntanus," r,vhich u'ould also essentiallr' include the rest of the forelirr-ib and pectorai girdle. Because a stress fracture is a partial fracture, the amourt of force inust be less than the maxirnurn required to completelv break the bone. Again, the furcr,rla of TCN4 2001.90.1 rvas used to calculate the force. The normal portion of the furcula corresponding to the pathological portion measures 4.5 cm clorsoventralli'and L7 crn anteroposteriorh,. Assuming the regions of the stress fracture rvere approxirrateli the sarne diniensions, then the force must har.e been less than 60,080 N (612B ke of pressure), resulting from ecluation l.

Scapula

'fhe scapula or T. rer rvas mostlv described b1, Carpenter and Smith (2001). Neu'inforrnation is available based on DMNH 2827. Tlie acrornion is a thin plate that is often darraged or lost in other specimens (e.g., NIOR 555). Forttrnateh; this region is presen,ed in DN'{NH 2827 and shorvs a small facet for tl-re epicleiclium near the scapulocoracoid sr-rture (Fig. 10.3). Thrs epicleidial facct measures 4.8 cn br, I.1 cm. Placement of the furcula connecting the epicleidiai facets ofthe left and right scaptrla shon, hou' close

170

Christine Lipkin and Kenneth Carpenter

Figure 1 0.4. Reconstruction of the pectoral girdle

and forelimb of Tyrannosaurus showing (A) the distribution of force

from the scapula

(a ar-

rows), through the furcula (b arrows), which results in cumulative force (c arrow) at the middle of the furcula. Resisting force c explains why the furcula is deepest at the midline, which is unlike any other theropod furcula. The range of motion for the forelimb segments (B), angle represented by arc a = 40',

arcb=60',arcc=67'.

Figure 10.5. Evidence for stress fracture

in the fur-

cula of TCM 2001.90.1 is the prominent callus (A), seen clearly in dorsal

view (B) and in close-up showing periosteal reactive bone (C). The region is X-ray opaque because of the greater deposit of bone (D, between arrows) Scale for A in cenumeters.

Lcoking Again at the Forelimb

171

i\ \{

of

togethertl-recoracoidsreallvriereinlifetFig. 1{J.4A,Fig. i0.6),apositior-r

Figure 10.6. Position

supported bv a nearlv uncrushed T'rannosaurLLs chest region found in situ that is currentlr, uncler studv (Lipkin and Sereno 2004). A sin-rilar close

the furcula relative to the

is :rlso knor,rr in haclrosaurs (e.g., Osborn l9l2), suggesting that coracoicls n e re closeh' placed in all clirrosaurs (including sauropods), as has

piacencnt

been cliscusscd elsen'here (Carpenter 20021 Carpenter et al. 1994). D\,INH 2827 also sholis rur Lrnrisual patl-rologv of the glenoid, which rs partialli collapsed as a result of l'entroposterior rotation of the coracoid. A1though the glenoid n'as partiallv d:rmaged during preparation (the bone rn the region rvas crun'rblr), it is clear tl-iat the 2 bones u'ere initially darnaged before co-ossification because the 2 bones are no\\r firrnh'fused bv remodeled bone (Fig l0 7).'fhe rotation is less near the acrornion and greater near the glenoid, suggesting that great rotational forces r'"'ere applied to the coracoicl in a posteroventral clirection, therebv partiallv collapsing the glenoid. Althor-rgh the claniage mav have resulted fron a fall onto tiie chest, the direction of rotation also corresponcls to the vector for the M. coracobrachialis brer,is ventralis (although the tern-rir-rologt' is retained for "dorsal" r'ersus

sca p

u Ia -

co ra

coids as seen

in a mounted skeleton of

Tyrannosaurus (cast of BHl3033). Human (Neal L. Larson) for scale.

Figure 10.7. Partial collapse of the glenoid in DMNH 2827 as seen in

lateralview (A), with close-up (B); in medial view (C), with close-up (D); and ventral view showing the telescoping that occurred between the arrows. Sclerotic bone overhangs the lateral surface. The amounr

T-rT-r-r--l

B

of deformation decreases dorsally to about the level of the coracoid foremen and indicates a posteroventral rotation of the coracoid due to great stress.

r-r-r-T-I-1

r-r-r-T*r] -:c
173

"ver-rtrai" rruscles, \ve are anare that the more l'ertical position of the humerus in Tyrannosaurus indicates a need for n-rodified terminology). It rs Figure 1 0.8. Comparison of normal right humerus of MOR 690 and its pathological left in anterior (A, D), lateral(8, E), and

posterior (C, F) views. Note spur at dart in (E), perisoteal reactive bone opposite arrow in (F), with close-up in (G). Region between darts in (F) are shown in lateral view in (H) and in close-up in (l). See text for discussion Scale in centimeters.

174

therefore possible that the clamage occurred lr'l-ren the individr-ral was voung and the forelin-rbs were pullir-rg struggling prev toward the chest. Unfortunately; so little of the skeleton u'as recovered (see N. L. Larson this volumel that ihe extent and location of damage to other bones is r:nknorvn (e.g., right scapula-coracoid, humems, gastralia). The distribution of pathologies elsewhere on the skeleton might resolve betrveen the 2 possibilities.

Humerus Several additional humeri are now known, incltrdir-rg n.rore wiih pathologies that reflect behavior. Overall, tl-rese specin.rens resemble those described b1'Carpenter and Smith (2001), differing only in minor detail. Two of tl're new specimens are of gracile rnorphs (e.g., MOR 980 and BHI 6210), nhich are probably male (P Larson this volume). The robust morph (e.g.,

Christine Lipkin and Kenneth Carpenter

Figure 10.9. Muscle maps cvd cbv.

@

\l

scc v dc hr D

ffi

A

K

qqt

%

I

Imn td

tm

tbclpa

for humerus in Tyrannosaurus, Alligator, and Gallus. Top row is anterior, bottom row is posterior. Muscle map based on scars (A, F) Tyrannosaurus. Map for Alligator (8, G) and predicted for Tyrannosaurus (C, D)

of Alligator humerus. Map based on deformatton

for Gallus (D, l) and predicted for Tyrannosaurus (E, J) based on deformation of Gallus humerus. Note that predicted scars for deformed

Alligator

ffi L

F

(C, H) are a

better match for the scars of Tyrannosaurus (A, F). This prediction is also supported by the

pattern of avulsion seen in a Tyrannosaurus human t< (l( I i 9aa Fint tro

FN4NH PR2081) is broader proximallr,'than the gracile rnorph (cf. Carpenter and Smith 2001, fig. 9.4, ri'ith F-ig. 10.8). As noted b1' Carpenter :rnd Srrith (2001), the humerus of FMNH PR208l shows several pathologies, as does the neri ieft htrrnertrs of NIOR

10.13 and

980 (e.g., Fig. I0.8). This latter humerus shon's an extensir.'e juxtacortical pathologi,located prorirn:rllr'on the anterolatcral, lateral, ancl posterolateral sides of the cliaphvsis, u'hich I'ras all but obliterated the deltopectoral crest (Fig. I0.8D, E).'l'he pathologv shon's extreme dismption of the cortical bone and irregular patches of sclerotic bone that strggest uner,en loss ancl regrou'tl-r of tl're periosteurn. The resulting pcriostitis inrplies extensir,e ir-rflammation of the region.'l'he region of the pathologv corresponds riith the crocodile hurnetus to the insertions of the \1. pectoralis, the conrnon insertion for the M. snpracoracoideus corr-ipler, \4. deltoideus clavicularis, common insertion for tl-re \I. teres major and N,I. latisirnus clorsi, ancl origins of the N{. brachialis, N{. hun'reroradialis, and part of thc triceps brevis cranialis (cf. Figs. 10.9B \\'ith 10.9K, G u'ith L). T'here is also a juxtacortic:rl lesion on the posterior side that, in the crocodile, corresponds n'ith the origir-r for the proxinral part of the NI. triceps brevis intermedius (Fig. 10.8F-, C; corrrpare 9C ri'ith L). Nlore distalli, there is a sn'rall spur on the posterior side as n'ell (Fig. l0.BIi, R H, I) Tl-rese 2 lesions blend n.ith the cliapl-x sis prorirnallr'but have sl-rarp, overiranging margins distallr that ma1'be due b oste oblastic response to the extensor motiorr of the or,erlving N{. triceps grorrp. 'fhe large patliologr,on the prorimai end is irregrilar or knobbl'. Supcrficiallv, it suggests a n'ralignant neoplasrn or ertensrre osteomlelitis, but as Dor-urellv et al. (1999) have notccl, site location i: inrportant for differential ,:<

ng Again at the Forelimb

text for further

explanation.

175

-l-he

diagnosis. iocation ancl extent of the pathologv is most probabl-v due to avulsion of nruscles in the r,icinitl of the cleltopectoral crest, and the posterior pathologies cl-re to periostitis frorn trauma to the periostenrr associated r,i'ith the event that car.rsed the avulsion. 'l'he aggressii,e appearance of the

proxinral pathologr', caused bv bone resorption resulting in a li,'tic appearance of bone, is cliaractcristic of a healing avulsion ancl can mimic the appearance of osteor.r-n'elitis or skeletal E'"r,ing sarcoma (Ster,'ens et a1. 1999). An ar,uisior-r is a failure of bone at a tenclinous or apclneurotic insertion of rnuscle ('lbhrar-rzadeh 1987; El-Khourr,et al. 1997). A'ulsions can either be actrte (the result of extreme, abnormal muscle contractions) or chronic (the resr,rlt of rcpeated n'iicrotrauma or overtrse) (Stevens et al. 1999), ."r,here reoccurrence of the injur-v is more freclucnt than the abilitv of the tissue to repair rtself (El-Khour','et al. 1997). 'l'he presence of a stress fracture in the furcula associated n'ith this specinren suggests that repetitive overlrse ofthe forelinlb ma,v have been a

major factor leading to the avr-rlsion. A seconclarl'factor mav

have been a violent stress on the arm because so rrany different rnuscles r'r'ere

apparentlv affected. Such stresses ri'ould be generated in the stidden pr-rll of the arrn tou,ard the chest at the salre tirne prev n'as stnrggling in the opposrte direction. It mav not be incidental that N{OR 980 is a votrng adult because 'lbhranzadeh (1987) noted that the inciclent of avulsion is highest in vounger hurnan indii'iduals. Regarclless of the cause, these pathologies support the h1

pothesis of forelimb use in fi,rcirnosdurl6.

Manus Tl-rc ir-rcorrplete manus olTyrannosauruE \\'as described b1'Carpenter and Smith (2001). Nen,specimer-rs, N{OR 980 and BHI 6210, provide nen,information, ir-rcluding a carpal ancl netacarpal III (F igs. 10.10, 10.1l). 'l'he carpal (fig. l0.lOA-F) is distal carpal I ("semilur-rate") and shori,s a facet on tl-re

proximal surface fbr the n'rissing radiale. 'l'his carpal shorvs that the damaged, incomplete one describecl br,Carpenter and Sn-rith (2001) is in fact a distal carpal I. Ventrallr', the r-rer,i carpal is facetecl ancl fits snuglv betu,een the proxin.ral ends of rretacarpals I and II (Fig. 10.11C), rather than across therr as in Deinortrclrus (Carpenter 2002). N{etacarpal III is slender, posteriorl'u' cun,ing, and tapering, ancl lacks a distal cond',.Ie, so it thus liad r-ro phalanges. NIOR 980 is frorn a larger ir-rclii'idual than BHI 6210, and tl-re differences betlr'een them are probablv ontogenetic. Thcse metacarpals strggest that as the indir.idual gren', the metacarpal becarne rnore robust and the proxirnal end formcd a broader attachrr-rent to metacarpal IL All of the nelr'inforr-nation on the forelirnb n'as used to create a new, vieu'of the pectoral girdle ancl forelin-rb of Tyrannosaurus (F-ig. 10.12) and r'r'as used in follolr,ing biomechanical studt'.

Reconstructing Forelimb Musculature

Nlathern:rtical rrodels for scavengers not u'ithstanding (e.g., Ruxton and Houston 2003), nr:rnr,of the sane criteria ancl assumptions for scavenging theropocls also hold for predaton'theropods as u'el1 (see Holtz this r,oltin're). In realitr, there are too manv unknou'n variables (e.g., population densities,

176

Christine Ltpkrn and Kenneth Carpenter

Figure 10.10. Distal carpal

of Tyrannosaurus in multiple views: (BHI 6230)

proximal or dorsal (A); distal or ventral (B), anterior (C); posterior (D); extensor side (E); palmar side (F). Metacarpal lll of BHl6230 in lateral (G) and extensor side (H). Metacarpal lll of MOR 690 in lateral (l) and extensor side (J). Scale in

I

centtmeters.

I

energentics, locornotion capabilities ofboth predator and prel) to ever have testable results. With so nany assullptions built on assuniptions, a house of cards results. Our approach is to rninimize assurnptions (including minin-iizing untested "common sense," referred to by Ruxton ar-rd Hor-rston 2003) and to rell'on evidence ar-rd testable r-nodels. Although r,r,e have attempted to minimize or-rr assurnptiolls, sorre are required as a result of the nature of fossilized rernains. We assume the fol-

lorving: (1) The pon'er outpr-rt of muscles of ertinct tetrapocls is comparable to that of extant tetrapods-that is, muscles \\'ere not ri'eaker or stronger than they are todat'. (2) Scars on fossilized bone that are clearlv not pathological (e.g.,lack of obvior-rs remocleling; see Rothschild anclN'lartin 1993) indicate insertion or origin for nr-rscles or for ligaments tbut see belolv). (3) Homoiogous origin-insertiorr scars, as determined br ertant phr logenetic bracketing, identifl'each mnscle (but see belou). (4) 'l'he ertent of the joint surface can be determined frorn the snooth surfaces of the joints, ri hich are separated -co
177

Figure 10.11. Distal carpal and metacarpals in articulation (BHl 6230). Proximal (A), digit I side (B), extensor side (C),

digit lll side (D). Scale in centtmeters.

Figure 10.12. Articulated

pectoral girdle and forelimb of Tyrannosaurus in lateral (A) and anterior (B)views.

178

Christine LtpLtn and Kenneth Carpenter

-\\

)

i'--:'-;K)

bi a rim or abrupt textural transition, and denote the area capped b1. joint cartilage. (5) The movernent of the joints rvas less than the area covered bt'the cartilage cap (based on dissections ofbircis) (Carpenter 2002). \{11}r these basic assurnptions, r,r'e reanalvze tfre foreli'b of Tt'rannos,lurits belo$. A testable of predicti'g rntrsculature patter's for the forelimb '-rethod elernents ofT\,ranno"aurus is presented that uses extant phr,'logenetic brackfron-r the diaphl'sis

cting, u'hich is based on comparable eleme'rts of the crocodilian ancl bird. Prer,iouslr', Carpentcr and Smith (2001) had preser-rted muscle maps for the forelirrb of Ttrannosaurus, the results of *'hich partially criticized by 'r,ere Brocl*r (2002). 'l'he foreli'b nrap was adrrittedly'influe'cecl too greatll, bv thc phi logcnetic placernent of T),rannosdurus as closer to n-rodern birds than to rnoclerr crocodilians (e.g., Brochu 2002). It r,vas believed that the rrruscle patterns should reflect this phylogenetic closeness, thus resulting in a loss of oblectir.'it1, from the start (the loss of objectivity in theropod studies rl'as subsequentlr,criticized bv Carpenter 2002, pp. 7Z-73).

'l'lre scapula and coracoid of'fyrannosau'rs

(ar-id di'osaurs in ger-reral) clifficult elements on rvhich to map muscles because feu.,rruscle scars are present and the shape of the coracoid differs; these issr-res harnper the application of pl-rvlogenetic bracketing. Ner,ertheless, the scapula and coracoid are cruci:rl ir-r rnuscular reconstructions because the rrr:scle origrrr patterns affect the nruscle patterns for the rest of the forelimb. Although nrr:scle sc:rrs rerlain the chief means for mapping muscles, strpplernental information is needecl in the case of the scapula ancl coracoid. This supplemental information, as a testable h1'pothesis, is obtained bv deforming the scaprrlocoracoids of both a crocodile (Alligator ancl bird (.Calltrs)to approxrare the rrost

-.a
Figure 10.13. Deformation of a crocodilian and avian scapula and cora-

coid (SC) to approximate that of Tyrannosaurus. Wavy vertical lines show direction and degree of

morphing. This method allows for the prediction of the position and shape of various muscles on the

Tyrannosaurus 5C (see text). (A) Tyra n nosa u rus d used as the end point to morphing of the (B) crocodilian and (E) avian pectoral girdles. Note that 2 possible scenarios (C, D) occur in the morphing of the crocodilian 5C depending on what portions of the crocodilian scapula is morphed into the acromion process of the Tyrannosaurus sca pu la - cora coi

e--^, 'l^ LvldLrvt I ^-^+;^^ ^{ ^)raPuto. I vt dt-

tual muscle scars (G). Abbreviations: bb, M. biceps

179

n-rate tlrat of TtrannosaunLs (,Fig. 1{J.13).

(continued) brachit c-M. costocoracoideus, cbd,

M.

co racob rach ia I is b revis

dorsalis; cbv, M. coracob rach i a I is brev is ventra I is, ce, M. coracobrachialis

externus; ch, M. coracohumeralis; dc, M. deltoideus clavicularis; ds, M. deltoideus scapuIaris; l,

sults can then be usecl to determine nhich of the 2 rnuscle patterns, crococlilian or a.,'ian, is rrost like that seen on the bones of T\'rtrnnoE(iurus.

All loratnr
M. rhomboideus superfiA' >uPI -,,^.^-^-^ -L tvl. -;^l:-. )ut ltoilJ, dtwt a-

coideus brevis; sc, M. sca pu

Io

h u me ra

I

is cra

n ia

-

scapulohumeralis -^ rvt. -,,r,--^^ -^,,)^l:-. )ct lduuau)t ^t )uu)ldP' ularis externus; si, M. lis, scd,

racoideus i nte rmedius; svc, M. subscap-

su p raco

u

la ris ventra I is cra nial is;

svt, M. serratus ventralts +L^.--;-. Lt M Otl)t

+ A, +-^^^-;,,-' Lt tVt. LI dPEZIU)l

tbclps, M. triceps brachii; caput longus pars scapularis, tll, M. ticeps longus lateralis, tm, M. terres major. Figure (B) and ter-

minology adapted from Meers (2003), figure (E) a nd term i nol ogy ada pted

from Yasuda (2002). Although the terminology is retained for "dorsal" versus "ventral " muscles (e 9., m.c.b. ventralis), the more vertical position of

the humerus in Tyrannosaurus indicates a need for modified terminology.

The technicl-re cloes not invohe nrorpliing of one scapulocoracoicl to another becarrse the sciipulocoracoicl of TyrannosatLrus is not used as one encl point. Althougli tlie te chnique uses a Cartesian grid, it does not atternpt to explain homologous points of 2 forms in the rranner used br, DArcl''l'honrpson (1961). Instcacl, the technique atternpts to predict the nuscle origirr ar-rcl ir-rse rtion patterns of the scapulocorac oid of Tyrannos(lurus as it n'ould be if the scaprrlocoracoicl of the crocodile or bir
'['he technique begins b1'scanning scapulocoracoicl otrtlines on r','hich the rnuscles have becn mapped (fig. 10.138, E). \,{inin-rurn thickness of the scaptrlar neck ri.'as selected to standardizc the scapulocoracoids of the Alligator, Callus, and'ffrannosaurus (Figs. l0.1lA, B, L,) because of ttie pecuhar shape ofthe avian coracoid precluded scapula-coracoid length as the stanclard. The N'le sh \\1arp fcaturc of Corel PhotoPaint 7 n as trsecl to cleforn-r the images using a l0 bv l0 grid. Bi'n-ranuallr'moving each intersect of the gricllines (node), a small area of the scapulocoracoicl surrouncling eacli node could be deforrned. The deforrnation vn'as snooth, meanir.tg that no sharp angles ar.rcl lines resultecl, thus approxin-rating changes in a biological structure. Nocles n'ere moved until the outline of the scaptrlocoracoid closelv approxinrated the that of 'Ij,rannoscttLrrrs (cf. Fig. l0.l3A and 10.11C, D. F). Because rnoving the nodes also rnor.ecl the cor-rtents of each gricl, the result is a prediction of llhat the resultant muscle pattern u'ould be like. As r-rsecl, N{esh Warp is not mathenaticallr' as rigorous as the thin plate spline of Bookstern (1991) because measurir-rg the change in lancln'rark positior-r is irrelel'ar.rt. 'livo versions are presentecl for tl-re cleforLncd crococlile sc:rpulocoracoid, ri.ith results clifferir-rg in the acrornion. Figure 10.13D :rssunles the dorsal pronrirtence just anterior to the scapular neck of the crococlilc is hon-rologous to the posterodorsal corncr of tl-re acror-r-rionirtTyrannosdrLrLLsl n'hereas Figtrre 10.13C does r-rot. This is tested belou'.

The n.ruscle patterns of the defomed crocodile and avian scapulocoracoids u'ere then conrpared against the feu.'muscle scars on the sc:rpr-rlocoracoid of T\,rdnnosrlurus (DNiNH 2827). As can be seen in Figure 10.13G, serreral nrtrscle scars on the scapulocoracoid of Tyrannosaurus seem to be r.i ith the origins for the N.'{. costocoracoidcris, NI. triceps longus lateralis, ar-rd 1,1. supracoracoideus intermedius on tl-re defomred crocodilian scapr:locoracoid, than u'ith anr,muscle origin on the scapulocoracoid of the bircl. We rrav infcr, then, that the other rruscles, for u'hicl-r scars are not evr-

I'ronrologor-rs

dent on the scapulocoracoid, \\'ere more hornologor,rs n'ith those of tl-re crocodile than of the bird. The large depression or fossa on the acromion of 'l\,rannosdurrLE seems to better match tl-rc pattenr for the NI. supracoracoideus interrredius in Figure i0.1lC thar-r for the rnultiple muscles irr this region, as seen

in Figure

10.13D. This suggests

thatthe dorsal pronir-rence of

tl-re

crococlilc is not horriologous to the posteroclorsal corner of the acronion in 'l ,--rdnnosaurus. Sonrr inclepencleut support for the shoulder of Tt'rannosaurus having tl-re crococlilian muscle pattern rat]-rer than tl.re avian pattern is seen in the Christine L'pl.'n and Kenneth Carpenter

cbd

tbc

sc dc

16+ld

Figure 1 0.14. Resultant muscle map for the humerus of Tyrannosaurus based on actual muscle scars and those inferred from Figure 10.13. Some

differences between actual and predicted include relative sizes of scars (e.9., m. deltoideus clavicularis), as well as position (e.9., M. terres major + M. latissimus dorsi). Where muscle scars are ambiguous, the

tm

hr tbi

prediction was used as a

A

B

guide constrained by unambiguous scars (e.9., M triceps brevis). Abbreviations: b, M. brachialis, cb, M. coracobrachialis brevis; cbd, M. coracobra-

c

scaptrlar blade. In a ranclonr sarnple of various bircl skeletons (DN4NH ai'ian

collection, including Aechntophorus, Buteo, CtgrLus, Cortus, AELila, Gttnr-Logtps, CalltLs, and Struffilo), a faint lor-rgituclir-ral tror,rgh is preser-rt in the distal half of the scapr-rlar blacle. h-rterpreted ar-rother r,r'ar', there is thickening of the scapular surface alor-rg the origins of the M. terres rnajor and l,l. rhomboideus superficialis; the trougtr is the unthickened bonc betrveen these origins. In contrast, the crocodile l-ras a single longitudinal thickening or riclge on the scapular surface that corresponds roughlv to the cornrron rnargin of the \{. terres major and N{. deltoideus sc:rpularis.'l'l're scapula of 'l.i,rannoscurus also has a similar ridge, not the trough seen in birds. The clefornation rnetirod outlir-recl above n'as applied to the hurnerus (Fig. 10.9B-E, C-J) ancl testccl against the rnuscle scars (Fig. 10.9A, F). Overall, the pattern most closeh' resembles that of the crocodile, u'ith notable erceptions. Aside from differcnces in relative proportior-rs of some nruscles betn,e en the actual ancl the predicted (cf. Fig. 10.9A and C, F- and H), there are :rlso son're positior-ral differences. For example, the cornnon insertion for the N{. terres n-rajor and N{. latissirnus clorsi is lot,er on the cliaphvsis arrcl nrore centrallr, located inTyrannosaurus (cf. fig. 10.9F, G, and H). Ftrrthernrore, there seerns to be a clistinct scar on all'I-t,rannosaurus hunieri, suggesting that the NI. supracoracoideus longus had a separate ir-rsertion slightll'beloiv the peak of the deltopectoral crest (Fig. 10.10)-eitlier that or the pectoralis insertcd niore lateral to the deltopectorai crest than medial, but that seerrs irighlv unlikeir'. As noted above, the patl-rolog1' on NIOR 980 better matches the muscle patten-r of the crocodile than the bird. \\/ith this information, it is possible to reconstmct the nusclcs of the pectoral girdle and antt of TrraruTosdlLrus (Fig. 1i) 151.

,':cring Agatn at the

chialis brevis dorsalis; dc, M. deltoideus clavicularis hr, M. humeroradialis; p, M. pectoralis; sb, M. supracoraco i d eus b rev is; sc, M. scapulohumeralis cra-

nialis, sc, scapulohumerat;- rouuou)t -^,,s^t:-, )LL/ )uPldtr) co raco i deus co m p

lex;

sl,

M. supracoracoideus longus, tbi, M. triceps brevis i

ntermed

iu

s (+ cra n ia I is?),

tm, M. terres major.

Ter-

minology adapted from Meers (2003).

Forelimb lBl

Figure 1 0.1 5. Reconstruction of forelimb and pectora I

g i rd

le muscu I atu re

in Tyrannosaurus based nn ra
anterior (B) views; intermediate rnuscles in lateral /a\ ^^.J /n\ ^^+^.i^. tu ar t Lcr tvr \u/ \\/ qr

views, surficial muscles in lateral (E) and anterior (F) views. Scale in centimeters. Abbreviations: b, M. brachialis; bb, M. biceps brachii, cb, M. coracobrachialis brevis; cbd, M. coracobrach i a I is brevis dorsalis; dc, M. deltoideus clavicularis; ds, M. d elto i d eus sca pu I a

ris;

h

r,

M. humeroradialis, ld, tendon for M. latissimus rlnrci n A,4 nartar>li<

ev'

J'1

P.

:c ".i sucracoracaldeus :':, i ia. '.1 scapulo' --'a'a

;s cranralts, scd, ,^^,^1;- tau-^,, )lotutvt,i^4,tutttctatr) AI --; -,,^.^-^-tvt. uoli >uPr alvr d^^1,-)/ )L//

,

coideus intermedius; sl, M. su p racoracoid eus I on gus, tbi, M. triceps brevis

intermedius; tll, M. triceps longus lateralis; tm, M. terres major. Termi-

nology adapted from Meers (2003).

182

Christine ..pL :n

2nj

Kenneth Carpenter

In this sectior-r, rve do a reanalvsis of Carpenter and Sn-rith (2001)

ar-rd an extensiorr of the biornechanical properties of the forelimb tn TyrarLnosaurus rex based rnostll'on FMNH PR208l. hr order to rvork out the forces

acting on the forelirnb, rve start by n-rodeling the forelirnb as a third-class lever (Fig. I0.16). In a tl-rird-class lever, the effort force (N{. biceps rnuscle) is applied betu'eer-i the fulcrr-im (elborv foint) and the resistance force. The elbor,l' joint is a hinge rvhere the humerus, ulna, ancl radius articulate. Of all of the nuscles coordinating and controlling the rrol'ement of the elbolr,, the M. biceps is the rnost powerful flexor of the elbou' joint (Ozkar,a and Nordin 1999). Our moclel assumes tl-rat the M. biceps is the rnajor ffexor ar-rd tl-rat the line of action (the tension) at the biceps is vertical. Anatomical ineasurements were used to derir,e the motive force arn (MFA) and the resistive force arn-i (RFA) (Table 10.1). For the ulna, the N{FA was r-neasured from the signoid notch to the rnidscar of the insertion pornt for the M. biceps (n'rotive force, MF), and the RFA lr'as derived from rneasuring the ulna frorn the sigmoicl r-rotch to the clistal end (F-ig. 10.16). To obtain ihe MIrA of the radius. we measured from the radial head to the rridscar of the insertion point for the M. biceps and frorr-i the radiai head to the distal end to determine the RFA. A tenclor-r ter-rsile strength of I00 MPa, the global n-rear-r across all species, was used to estimate the tendon tensile strengtl1inTl,Tannssaurus (Nigg and

Herzog 1999). The safetv factors in tire values of bird tendons range from i.19 to 4.10 (Van Snik et al. 1994;Alexander 19Bl). A safetv factor of 3 n,ill be used ir-r this studl'. The normal working range (NWR) is one-third the safetv factor (Carpenter and Smith 2001). Although the size, sl-rape, ar-rd tl-re biomechanical behavior of each tendon differs, the basic structure of tendons and tl-reir rnechanical properties are sin-rilar (Jdzsa and Kannus 1997). The size of the cross-sectional area ofa tendon is clirectlv related io the size ofthe load that can be carried before failure (Butler ei al. 1978). 'fhe srrrface area of the scar for the insertion of the \,1. biceps rs 122.11 mn-rr on the radius and 192 nmz on the uh-ra. The conversion for the tendon strength, expressed as MPa, is I MPa = 1,000,000 Pa, u.'ith l Pa = I N/mr. Therefore, I NIPa = I N/rnmr. The maximum i,vorkir-rg range (N{WR) and the NWR are calculated from the tensile sirength of the tendon.'fhe formula for estirnated tendon tensile strength is as foliows:

tendon tensile strength/area2 x surface area of the scar for insertion of the M. biceps = estimated tendon tensile strength

Biomechanical Analysis of the Forelimb in Tyrannosaurus rex

Elbow

Figure 10.1 6. Free-body diagram (sinplified model) of the forelimb of FMNH PR2081. Abbreviations: MF, motive force; MFA, motive force arm,' RF, resistive force; RFA, resistive force arm.

(1)

Tendon tensile strengih for the radius is 100 N/mm2

x

122.11 mm2

where NIIWR is 12,211 N/3 = 4070 N, and

= 12,211 N

N\\'R

is 4070

N/l = 1357 N

Tenclon tensile strensth for the uina is:

100 N/mm2

x

192 mm2

= 19,200 t

N

ooking Agarn at the Foreltmb

183

Table 10.1 . Power Analysis

Measurements

Measurement

Radi us

Ulna

MFA

15.2 mm (0.0152 m)

45.8 mm (0.0458 m)

RFA

166 2 mm (0.166 m)

186.6 mm (0.187 m)

MANUS

177.6 mm (0.178 m)

171.6 mm (0.178 m)

343.8 mm (0.344 m)

364.2 mm (0.36a m)

Abbreviations.-MFA, motive force arm; RFA, resistive force arm.

RFA

including manus

rvhere N{WR is 19,200 N/3 = 6400 N, and NWR is 6400 N/3 = 2lll N. 'fhe values for the MWR and NWR represent the estimatecl strengtir of the iei-rdon at the insertion of the NI. biceps and are ttsecl as the NIF in the analvsis of the poiver of Ihe TyT6lnnosdurus forelirnbs. Tl-re follolving equations are nsed to estimate the amount of force the arrn of Tyrannosau' rus can resist (resistive force, or RF):

MFxMFA=T

(2)

RFxRFA=T

1?)

Measurement of the Inanlls (177.6 rnm) n'as taken front a cast of to tl're prorimal end 2081, from the proximal end of the "r'rist of the claws. It n,as then aclded to the RFA (166.2 nm).

FNINH PR

N{WR for the radius of

T

re.r is as follorvs:

4,010 N x 0.0152m= 61.86 Nm RFx0.1418m=61.86Nm RF = 179.91 N (or 18.36 kg) NWR for the radius of T. rex is as follo"vs: 1,357 N x 0.0152 m = 20.63 Nm

RFx0.3438m=20.63Nm RF

MWR for the uina of T

= 60.0'1 N (or 6.12

kg)

rex is as foliou's,

6,400 N x 0.0458 m = 293.12 Nm

RFx0.3642m=293.12Nm F = 804.83 N (or 82.13 kg) NWR for the ulna of T. rex is as follou,s: 2,133 N x 0.0458 m = 97.69 Nm

RFx0.3642m=97.69Nm RF

= 268.23 N (or 27.37 kg)

Adding the resistive forces of the radius and ulna results in 984.76 N \4WR (no safetv factor) ancl 318.24 N

(100.49 kg or 221.10 por-rnds) for the

Christine Lipkin and Kenneth Carpenter

(13.a9 kg or 77.70 pounds) for the NWR (u,ith safetv factor). The conversion factor for kilograrrs to ner,r'tons is 1 kg = 9.8 N.'l'hese results are sunrrarized

in Table 10.2. An a','erage strength of

5 kg/cm2 per cross-sectional area of muscle u'as deterrnine the cross-sectional area of the M. biceps in TNrannosaurus (Carpenter and Smith 2001). The NWR of the tendon tensile strength for the

rrsecl to

and ulna nere added together to get the MF: 1357 N + 2lll N = +490 'l'he formula used to determine the cross-sectional area of rruscle is N,{F (kg)Atrength (kg x cni t) = ctoss-sectional area (cnr). Thus, radir-rs

N

(356.12 kg).

the estirrated cross section of theT\,rannosduruE M. biceps is 356.12 kg/5 kg x cnr I = 71.224 crrf . 'fhis translate s into a diameter of 9.52 crn. Of course the N'1. biceps is r-rot the onh'arrn protractor. In fact, b\,r,rsing half the estirnated cross-sectional area of the upper arn-r (based on a diameter of 2j cni), the arriount offorce generated is estimated to have been around l l 50 kg, or I 1,270 N. Of this, the biceps generated aboti40%, and tl-ius'"r,as a major muscle.

A small lever arn'i requires greater nuscle tension to balance a load. Therefore, n'hile resistir-rg pre\,or holding prer; it is clisadvantageous to ha'u'e a rruscle attacl.rment close to tl-re elbon' joint. The advantage to having the rruscle attachment close to elborv joint is that it il,ill have a larger range of motion of

Mechanical Analysis of the Forelimb in Tyrannosaurus rex

tl're elbon flcxion-extension. and therefore the hand can nrove faster toward

the upper arm or sl'roulder (Ozkar,'a and Nordir 1999). 'I'he rnechanical advantage is the amount of force a given effort can procluce. It can be expressed as a ratio ofthe resistive force to the N{F, or as a ratio of tlie NIFA to the RFA (Kreighbaum and Barthels 1985). Both of the equatior-rs produce the sarr-ie result.

TheTtrannosrzurus forelimb is found to have a n-iechanical advantage of the 0.09 (RFA rneasurenrent including the hand) ar-rd 0.18 (RFA measurenent excluding the hand). The rlechanical advantage of a humarr forcarm is 0.07 (RFA n-reasurernent inclucling the hancl) ar-rd 0.13 (RFA measurement cxcluding the hand). Next n'e er,aluate the force at the elborv joint. The sum of the tr{Fs (NWR + \'l\\1R) at the radius (138.3 kg) and the ulna (217.5 kg) rninus the RF'at the rranus (33.5 kg) nust equal the force at the elbou'for a static con'|38.3 fiqrrratiort. I lrcrefore, T1'ranrtosaurus has a force of + 2l-.; - 33.; = joint liZ.lUgat the elbor.r, for the NWR. This cornpares with a force of about 128.25 kg at tl-ie elbo'nv joint of an average adult rnale human for the NWR.

RF

Table 10.2. Power Analy-

(kg)

sis

Range

Radius

U Ina

Combined

MWR

18.36

82.13

100.49

NWR

6.12

27.37

33.49

Summary

Abbreviations.-RF, resistive force; MWR, maximum workrng range; NWR, normal working range.

Lccking Again at the Foreltmb

185

Acceleration

Frorn the torcpre of the forearrn, the force that could be applied at the manus and the resultant force at the elbou joint ri'erc determined. Wc non estimate the acceleration that could be generated at the clan's using the nontent of irrertia. The fleshed-out versiorr of ihe arm olTl,rannosaurus (Figs. 10.1510.17) rvas converted to a closeh'packecl series of elliptical o'linclers.'l'he cross sections of each

elliptical o'linder nere deterrnined from Figure

10.15.

Assurnir-rg a clensitv of 1000 kg/n'r: for tissue, t}'re dat:r frorn these o'linders resr-rlt ir-r a mass of 1.8 kg for the fore arm plus nlanrls. The integral of the densitr'

times the perpendicular distance to thc pii'ot point results in a moment of inertia of 0.06 kg mr. Becar-rse the \\\rR torquc of thc forcarnr and I'rand to be 118.J Nm, the angular acceleration (torclr-re divided bv the morncnt of incrtia) is l98l s 2. Tl-re angular acceleration can be conr.'ertecl to a linear acceleratior-r bv rriultiplving it b1'the distance (0.154 m) frorn the pivot point to the clan's, n'hich results in a linear acceleration of 702 nis r. This is likeh' an ot'erestimate because the skin and the clat'sl-reatli are not factored in. Aiso, this onlv gives the initial acceieration. The force fiom uruscles is krton'n to rapidlv recluce at high speeds

Conclusions

(Hill

1938).

As rve have shou n, the forearm of Tvrannosaurus \\'as capable of resisting large forces and rnor,ing at high accelerations. These results strcr-igthen the hvpotl-resis that the forelimbs n'crc ttsed during predatior-r. Hon,cver, because of the small size of the forelimb relative to the bodi'size, it is unlikeh that the T\'rannosaurtLs lr'oulcl use the nranlls for striking pre\', as discussed in Carpenter (2002). Rather, thc forelimbs mar'have been usecl to cling to pre\,. Our results of finding large fcrrces at the elbou' joint and possible signs

of injr-rn at the furcula fr,rrther support tltis l-n'pothcsis. Fir-ralli', in contrast to the belief of l,ocklev et irl. ttl-ris volun-rc) that "no usefrrl ftrnction is plausible" to explain the forelirrb of 'It,rctnno"aurus, our results support the prer,'ious assertion tiiat tlie forclin-rb plavcd a functional role in predation. Bv iniplication, the short forelinrbs of other tl.rannosau-

Figure 10.17. A 3-D representation of the forearm and manus in the

Tyrannosaurus rex FMNH PR2081. In (A)

lateral, (B) anterior, and (C) reaching views.

186

Chilsilne Ltpktn and Kenneth Carpenter

100%

radius

90%

Figure 10.1 8. Compailson of forelimb length to

70%

hind limb length shows that a progressive reduction in forelimb length does not occur in the

6s%

Abbreviations; Gu,

humerus

80%

Tyrannosauridae.

Guanlong (basal 50%

tyrannosauroid); Go,

40o/o

Gorgosaurus; Da, Daspletosaurus; Ab,

Albertosaurus;

30%

T,

Tyrannosaurus.

20% 10% 0%

Gu age {mya)3 -156

Go

-75

Go

*75

Da

Ab

T

-75

-72

-66

rids had a similar function. In strpport of this, n,e note that a progressir,'e reduction in tl-re forelinb does not occur in tl're Ti'rannosauridae (Fig. 10.18), contrarv to Paul (1988; and l,ockler et al. (this l'olurre). In point of fact, once the shortened forelirrb of the tvrannosar-rrids ivas established, it remained proportionallr stable relative to hindlimb length.

We are honclred to contribute to this r.olume. and n'e thank Neal Larsorr and Peter Larson for the organization of the sl,rrposiurr that preceded it.

Acknowledgments

We are indebted to Bill Sin'ipson and Peter \'{akor,ickr.,for access to ITN4NH PR 2081. and C.L. rvotricl like to thank Paul Sereno for access to the cast of FN,{NII PR 2081, ar-rcl N{icl-rael Benton, Paul Sereno, Gordon, }iirgen Kriu,et, Simon Braddt', Lorrie NlcWhinner', ancl Don Henderson for helpful discussions. K.C. tlianks fohn Daggett, Bill Sirrpson, and Pcter Larson for loans of specin-rens or casts, and N{att Srriith for our previons joint r,r'ork

onT. rex forelinb analvsis. C'l'scans are br.Steven White, Kaiser Perrnanente, Denr,er.

Alerander, R. \{cN. 19E1. I,irctors of safetr,in the structLrre of anirnals. Science

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W

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Lcoking Again at the

Forelimb

189

scavenger rather than a predator? An energetics approach. Proceedings: Biological Sciences 270: i)I-733.

Dutheil, D. B., Iarochene, \,{., l,arsson, H. C. E., Lvon, G. H., Maguene, P N1., Siclor, C. A., Varricchio, D. J., and Wilson, J. A. (1996). Predaton'dinosaurs fron the Sahara and Late Cretaceous faunal differentiation. Sclenc e 2 r- 2: 986-99\. Stevens, N{. A., El-Khonrl', C. Y., Kathol, \'{. H., Branclser, E. A., and Chori', S 1999. Imaging features of avulsion injLrries. Radiographics 19:655-672. Tehranzadeh, I. 1987. The spectrum ofalulsion and avulsion-like injuries ofthe Sereno, P. C.,

rntrsctrloskeletal s1'stern. Radio graphics 7 : 9 45 '97 4. \\'. i961. On Growth and F'orm. Cambridge Llnir.ersitv Press, Cambridge. \/an Snik, G., Ohnos, N{., Casinos, A., ancl Planell, J. A. 199'1. Stresses in leg tendons of birds. Netlterlands loun'Lal of Zoologl: +1: l-11. Yasrrda, N{. 2002. The An:rtonl of CalltLs. Tokvo, Ur.riversitr,of Tokr"o Press. Thornpsor-r, DArcv

190

Chisilne Lipktn and Kenneth Carpenter

Figure 11.1 . Ray Wilhrte using an Immersion M icroscri

casts

of

be

d ig

itizer on

elements of the

pelvic glrdle of Tyrannosaurus rex specimen BHI 3433 6tan). Photo cour:-"s;, Ray Wilhite and Vir'

lual Surfaces lnc.

192

Kent

A. Slei,ens et al.

REX, 5lT: DIGITAL MODELING OF TYRANNOSAURUS REX AT REST

11

Kent A. Stevens, Peter Larson, Eric D. Wills, and Art Anderson

The great tl-reropod TrrannosaurtLs rex is usuallv depicted in an active, brpeclal pose, perhaps in purstrit of prei'or lacing off ar-r opponent. Some artists, e.g., Lau,rence Lan.rbe (19i7), Cregorl. S. Paul (1988), John Sibbick (Non-nan I991, p. 72), and N'Iichael Skrepnick (Currie et al. 2004), hale providecl vieri's of these animals in other, less active postures, includir-rg h-

Introduction

ing prone or squatting. Presurnabl',' the anirral ri'ould rest',vith a substan-

tial portion of its bodr n-rass supported bv the pronrinent pubic boot. Trace fossils of small crouching theropods shot' both tarsal and pubic-iscl-riatrc ir-rpressions (e.g., Cierliriski et al. 2005). In the great theropods, descending

from a standir-rg pose to a rest position \\'as presllmablv a straightforivard matter of squatting, a process cor-rsiderablr less involr,ed than the complex sequencing of folding movenents that sorre modern large quadrupeds, sttch as camelids (Cauthier-Pilters and Daag I981)ancl bovids, nse to lorver tlreir nrass to the ground . Tyrannosar-Lrus rer might sin-rpli' have settlecl vertrcalh' in one continuons flexiorr mor,enrent inr,olving the hip, knee, and ankles.

It is in risirig front a prone or sqtratting rest position that some concent for the mechanics of the tvrannosauricl frarre might present itself. Hou' could the center of mass (CO\I) be controlled so that the anirnal lr'as stable lr4rile rising? Was there strfficient rnechar-rical adr.'antage in the rnajor extensor rnnscles to provicle a clirect ascent tl-rat retraces the trajectorr, follor'ved in descending to the ground? Were the forelimbs uscful in stabilizing the boclv and in providing thmst cluring the initial stages of the ascent? To address sone of these questions, a fullr articulated digital rnodel of 7l'rdnnosaurLrs rex \\,as created ri'here limb nror,.ements are delirnited by ar-ratomicalll' based estirnates of achiei'able range of motiorr, and the position of the instar-rtaneous CON{ of the anin-ral can be visualized in order ro judge balance and stabiliti'. Extant bipeds that lnight serve as analogs for str-rdving the sitting and standing movenents ol'I'. rex, include members of the N,Iacropodoidea, notablr,' tlre large red kangaroo (Nlauopus rufus) and a varietv of birds, particularlv the large ratites sr-rch as the emu (Drontaius not,aehollandiae) and tlie ostricl-r (Struthio carnelus). As anin-ral rrass increases, muscular strategies cannot be erpected to scale indefinitelv (Alerander 1989); the effortless rise of a small passerine fron rest to a bipedal stance rnight require rnr.rltiple, nlore cleliberate stages of limb ertension in a bipecl of ser. eral orders greater seight. 'l'he biorrechanical principles governing tfre Rex. 5lt

193

choice oi:trategr', particularll as regards.cairi; nith bodv tnass, are not il'ell unde rstood. Nlotion stuclies have conc cnir.rte d on capturing relativelv steadr-state locornotion (e.g., N{ulbridge 159v; Jenkins etal. 19BB), notthe transient bociv rnovements associated n ith :ittinq or st:rnding. 'lb examine tlre potential movernents that take the anirnal frorli standing to sitting. and vice ',,ersa, it is important to begin il ith an estirnation of the tl picai stand and sit postures. N{or"enrents that srnoothlr,'transition betn'een tliese extrerres can then be proposed and analvzed. In their analysis, it is irnportant to r-rnderstand hoii'tlie CO\l translates during the rrovemer-rt. Longitudir-ral (caudai-cranial) pitcliing ntovements in particular lvould produce instabilitv tl-rat i,l'ould have to be correctccl at risk of injurr' to the great theropod. It is also irnportant to exauine range of motion issues tl-rroughout the sit-stand moventents and the rnechanical leverage of large mnscle groups for pror,iding the necessar\, rnor"ements. Proposals have beer-r offered for horv T. rar could sit dorvn on its pubic boot, then rise bv first using the forearms as props to help anchor the front of the bodl' u'hile the rear legs n'ere straightened. 'l'he r-rpper bodv would then be tiltecl back to regain an upright standing posture (Nervman I970). This idea is but one of the poteniial uses proposed for tl-re forelinibs (Osborn i906; Horner and Lessem l99S; Carpenter and Smith 200i; Carpenter 2002). In tl-ie follou'ing, an articulated, J-dimer-rsional cligital reconstruction is used to explore alte rnatir,'e hvpotheses regarding the sit-stand mot'ernents of this dinosaur. The process of descending and then ascencling is amena-

ble to quantitative modeling, taking into consideration the distribution of rnass in the anirnal and the flexibiliti' of those joints involved in the rnovernents, particularh'the ankle, knee, and hip ri ithin the hind iimb, and the potential role of the forelinbs in the process of rising. Qr,rickTirre video sholr'ing the action is available in the supplemental CD-RON{.

Creating an Articulated Digital Model

DinoNlorph softn'are

(Ster.'ens 2002) provides a frameu'ork lvitl-r u'l-ricl-r to create and pose a cligital nrodel of T1'rattlosdurus rex.'lhe softrvare can accept 3-dirrensional data representing bone rnorphologr' (e.g., from corn-

puted torriographic fCTl scan or hand cligitization), as n,ell as more schernatic and sinrplified representations. In this str-rdr', the Tlrannosaurus rex specimen BHI l03l (Stan) at the Black Hills N,{useun of Natural Histor-v u'as used as the source for the digital nroilel. Tl'ie articrilation of the apper-rdicular skeleton and tire morphologv of the peli'ic ancl pectoral girdles n'ere of particular importance, so thel' u,ere specificallv for this studi.' (Fig. 11.1). Digitization data of the liead r,ias provided from an earlier CT scan macle b1'Virtual Srirfaces Inc. and the Black Hiils Institute. 'f he ren-rainder of the axial skelcton',i'as nrodeled schematicalh', lvith centra, nettral spines, iateral processes, chevrons, and ribs in a dimensionallv accttrate br-rt simplifiecl forrri 1Fig. 11.2). 'l'he nert step n'as to estimate the relative placement of each bone ivithir-r the olerall skeletal framen'ork. -\long tire presacral axial skeleton, the interlertebral separations and oi'era11 crtrr';rture u'ere deterrnined frorr-i Kent A. 5t?,'ens et al.

measurements ar-rd photographs ir-r lateral vielv. Likeu,ise, the rib cage \\'as formed by' painstakingll, adjustir-ig each digitallv represented dorsal rib to match the curvature, dimensions, and placement of its counterpart in reference photographs that were unclerlaid ivithin DinoN4orph as background images (Fig ll.3). To refir-re the 3-dimensional skeletal n.rodel, tl-re trr-rnk was successivelv r,ie',r,ed in anterior, dorsal, and lateral orientations, and for

each vierv, the cun'ature and placement of the ribs q,ere adjusted so that the digital ribs superirnposecl precisely'over their phoiographic counterparts. The pelvic girclles, complete u'ith furcula, r.vere then placed or-r the

thev are rnounted on Stan (Larson and Rigby 2005). Next, those DinoMorph parameters governing the position and orientation of all appendicular joints r.vere adjusted to create a neutral standir-rg

rib cage

as

pose, the starting point for this study. Tl-ren, for the major apper-rdicular joints in-rportant to this stud\', a range of motioir rvas deternined on tl-re basis of an estimate of the tl-rickness and extent of the intervening cartiiage in modern avians and direct manipulation of the casis (Kennetl-r Carpenter and Yoshio Ito, personal connunication June 2005). Direct rnanipr-rlation assisted in deterrnining, for example, the axis of rotation of the femur head

ivithin the acetabulurn, and in the forelimb the orientation of the fully

ex-

Figure

BHI 3033 (Stan). The appendicular skeleton and hoarl rttara diaitizar'l ,^,4^.^^+A^ -,.;-l )^-1,^i ' vvt tct cd) Lt tc d^tdl FT6h tlt2< ranra
schematic form, .'.,:' important drmenstc.s (e.9., centru m e ngir,, neural spine height, anci I

nterverteb ra I se p a ra tions) d i me nsio na I ly accurate. (B) The axial skeleton was laid out with reference to measurei

ments taken from the mount and photographs (see text). Scale bar indicates an overall length of

In analvzing poiential sit-stand strategies of a theropod dinosaur rveighing several metric tonnes, it is important to track the trajectorv undertaken bv the CO\{ clurir-rg hvpotl-resized rror.enrent. The CONI is computed in DinoNiorph br assigning both a volunre and a densih'to eacir Rex, Sit

1.2. (A) Dino-

Morph model of Tyrannosaurus rex specimen

11.2 m.

tendecl forelirnb u'ith respect to the pectoral gircllcs.

1

195

Figure 11.3. (A) Screen image showing the reconstruction of the trunk superimposed on a reference photograph of an assembly of casts of the Stan specimen. Background image courtesy Black Hills lnstitute of Geologic Research. (B) DinoMorph model

shown with addition of digitized pectoral gi rdles (i ncl u d i ng f u rcu I a), forelimbs, and pelvic girdle, all based on Stan.

discrete segment of the skeleton, such as each inten'al of the axial skeleton associated rvith an ir-rdiiiclual r"ertebra. Fittecl cor-rical and elliptical c,vlrnders are used as a first-order approrirliation to the bod,v cross-sectior-ral area,

Figure 11.4 (opposite). (A) Visualization of the distri-

bution of body mass, based on a parametric

fit

to segments of body cross section of the axial and appendicular skeleton. (B) Computed COM visua I ized j ust

a

nteri or

pubis, and above pes, as required for static bipedal balance.

IYO

governed br,' adjustable parameters (Fig. II.4). The densitv (i.e., specific gravitv) associated n'ith each segn-rent nas adjusted to rougl-rh'reflect cranial and axiai pneumaticit-v, air sacs, and lungs. The CC)N4 n'as con-rputed by sumnating the gral'iiational noments associated w'ith each segment tl-rroughout the skeleton. By assigning densities of 0.8-1.0 to presacral regior-rs and 1.0 to segrnents of the appendicular skeleton and car,rdal vertebral series, the overall CO\,tl rvas located jr-rst anterior to the pubic shaft (see Fig. ll.'fB), consistent u'ith estimates b1' Henderson (i999) and Hutchinson and Carcia (2002). Srnall br-rt potentiallv significant shifts in the instantaiieous COVI during movements could be detected visuall1,'as the movenent unfolded. F-or this studl', a litl-re recor-rstmction of tl-re cross sections of soft tissr-re associated n'itl-r each segment of the skeleton n'as chosen to corresponding to recent computations by one of us (P. L.). The resulting overail mass for BHI l0l3 (Stan) u as estimated as -4400 kg., or about 807 of the n-rass estimated for the rrore robust specimer-r FNINH PRZ081 ( Sue t bi usir-rg the san-re techniques { Stevens et al., in preparation). Although it ri as possible to esiimaie as little as 1800 kg for the san're skeletai KentA.

Ste;,e

"s et a/.

stmcture br,progressir,'elv redtrcir-rg bodv bulk, particularlr' in the peh,rc region, for this studl', the position of the CON{ u,as of greater irr-rportance tl-ran the rnagnitude.

It is reasonable to assume thatTyrannosdurus rex, and other theropods n'ith distallv expanded pubic boots, lor,i'erecl itself until the majority' of its rnass bore clou'n on the pr,rbis. Upon ground contact, the orientation of pelvrc girdle u.'ould have shifted slightll,'so that the elongate ventral surface of the pubis laid generalh.parallel to the horizontal ground. The elongate pubic shaft of T rer places the r.entral surface of the pubic boot just belolr, the knee, perrnitting sirnultaneous ground cor-rtact at the knees and along the pubic boot (Figs. ll.5-6). The pubis thr-rs likelv provided a stable rneans to offload the great najoritr,' of tl.re anirnal's rieight, limiting pressure on the respiratorr,slstem, and to perrr-rit repositioning of the hind linrbs rvitl-rout requiring a shifting of u,eight. The limit of hip flerion (femoral protraction) is difficult to estimate because it was governed br soft tissnes, but it iikell' '"vas sr-rfficient to pern-rit achieving the protraction shou'r-r in F'igr,rre 11.5A so that the tarsus coulcl lie flat on the grorind. The limits of knee and ankle flexion are lnore obr.ious in the osteologi'. It is notetorthv that in a full

Rex, Sit

Reconstructing a Sitting Movement

Figure 11.5, DinoMorph model of T. rex Stan demonstrating that the pubic shaft is sufficiently long that, with the animal's weight resting on the pubic boot, the hind limb is free to assume a broad range of positions from (A)crouch, to (B) kneelto (C) moderate extension

of

the hip and knee, to full leg extension when stretched behind the hips

Reconstructing Standing Movements

(not shown). Note that in the<e ? imana< f he far
limit of flexion, in (A) and (B), the knee rs is near the

fully flexed. Observe that he knco

it

deternrined that a descent rrol,ement coulcl be perfornre
In rising, Trrdnnosaurus rex has to cope n'ith lifting the CON{ br,approunatel1, l.'l m verticailr'starting u'ith tl-re pubic boot in ground contact and ending in the neutral stancling pose, as seen in Figure 11.4. This could be achieved in principle br pure nusctrlar exertion of the large ertensor muscle groups of the hind lirnb, particuiarlv the N{. car,rdofernoralis longtrs, the largest contributor to fernoral retraction, and secondarill'the knee and tarsus extensors. 'l-he I,{. cauclofernoralis longus, hon'er,cr, is simultane-

Alternative

f

squat (Fig. ll.5A), $hich brings the pubic boot in contact u'itl-r the grotrnd, the kr-ree and ankle are nearl.",fullr' flexed. To visualize the descent from a ne ntral standing pose to a squat, DinoMorph n,as used to interpolate betr.i'een these 2 ettrernes of pose. Br. constraining all joints to rnovements u'ithin their respective ranges of motion, it

rcf rloar< fhc

arat rnrl a< if
laboration with Yoshio lto and Kenneth Carpenter.

198

ousl1,'in significant stretcl-r (roughll' 115% of that ri'hile stancling), and the mornent (or lever) arm is greatlv foreshortene d (Fig I I.7). Depending or

the particuiar position of the femur in this deep scluat, the rnoment arrr rnav be less than 40% of that provided nfien stancling. l\,rannosaurLts rer, n'hile resting on the pubis, could fre eli'retract one or both ferlora (Figs. ll.5 and 11.6) and hence var\,the stretch on the N{. caudofenroralis. Optinial mechanical aclvar-rtage occurs u'hen the fenrur is roughh. vertical (i.e., associated rvith the thrrist phase in ]ocornotion). Although the fernoral position pror,iclir-rg greatest muscle mornent r,r'ould correspond tcl roughll'that in Figure ll.58, the placement of the pes in Figure II.iA n'ouid appear better suitecl for eler,ating bipedallr because the hind feet are then under tl-re CONI. If T. rex n'ere not to slon'lr' rise r erticallr, into a stationarl standing position, but instead accelerate diagonallr'frorn the squat in Figr-rre I L5A, then, pror ided the hind limbs direct the grouircl reaction force diagonallr through the CON,{, no net pitching monrent nould be created as the animal

Kent A. Steyens et al.

Much

sprinter begins a race accelerating and rising graduallv out of the blocks, it is not inconceivable IHatT. rex could har,e accelerated diagonally uprvard from sittir-rg into forward loconotion. Although it is rrore iikel1,'an rose.

as a

option for light voung tvrannosaurids, it rernains a matter of qtrantitative ntocleling to estirnate r,r,hether tl-rat u'as achier,'able bl an adult.

If the fernoral retractor muscles u'ere not ir-r an adr,antageous state for liftingTyrannoselLrlLs rex r,erticalll' out of a squat into a balairced star-rdirrg position, rvhat rvere the alternatives? One suggestion (Phillip N,Ianning, per-

Figure

'1

1.6. With the

DOOy mass

suppor:ai ..,

the pubic boot, /,*A-^ ^^ -, tU) oPPCdt

ttt t

-'.

!n.

LU t ]d I

t

been able to shift frorn (A) a sitting position (with hip flexed)to (B) kneeling on one knee or

(C)both knees, without

sonal communication June 2005)borrou's from modern analogr,res. In ratites

having to lift the body

in particular, the

weight off of the pubic boot. Although the axislike insertion of the femur head within acetab-

\{.

gastrocnemius cornes into pla1,: the Achilies tendorr

stores energr,'n'hen in a state of stretch, li,hich is trapped lr,hen the anirnal's

weight bcars clou'n on the tarsus ivhile sitting. Bv leaning foru'ard onto the its knees, the tendon is released, and the hind limb receives a passive boost. Whether recoverv of stored mechanical ellergv r,iould scale to be of significarrt value in helping bo ostTNrannosaurus rex frorn sitting to standing n'oulcl require quantitatir,'e stud",. One further concern, bevond the rlatter of scalir-rg to be effective on a 4000-kg anin-rai, is u,hether the stored energv lr'ouid dissipate during the period of rest as the Achilles tendon r.r,oulcl stretch. Another approach is to enlist the forelimbs, as suggested bv Nen'man (1970), as a potential use for these appendages. When sitting, thev are close to the ground and are brought into contact b1'a slight tipping of the pelr'is about theprepubis(Fig. ll.E).T'hey66sl6l l-rar,'ebeeninstrumentalinrisingbackinto a standing position. As shou'r-r in Figure II.9, although the forelirrb range of

ttlt tm
femoral abduction was possible, there was likely suff i ci e nt fl exi bi I ity to provi d e I ate ra I sta b i I ity. M oreove

r,

th

e poste ro I at-

eral angulation of the acetabular axrs caused fhe knees to splay ',t'ii1'1

femoral protracrco aga -

aidi ng stabi lity aga I nst

Iateral tipping in addition to clearing the rib cage as necessary tn

tocomouon.

Figure 11 .7. ln ascending from repose, the M. caudofemoralis longus is in

stretch (-115o/o) and the moment arm is greatly fo resh orte n ed com pa red with its neutral state when standing, thus providing poor mechanical advantage. Rex, Sit

199

F ig u re 1 1 .8 . When resting on the pubis, the forelimbs are near ground level. They are n'a oh, aln<ar fn nrnt tnrl

.- c :( ) ann
^iatingastandtng

-

J.

:-?nt

f rom

this rest-

rg oose. A modest tipping of the body, by pivaf ina shar tt f ha rt rrrtorl a

nte rove nt ra I su

rface of

the prepubis, would have shifted the overall COM a nteri o rly a n d retu rn ed the point of balance to between the hindfeet. In fha nrnra<<

fha fnra-

limbs would have been available to assist in stabilizing, if not actively

contributing toward raising, the body, by pushing against the ground.

Frgure 11.9. (A)Reconstruction of the pectoral

girdles and forelimbs based on CT data kxcept for the radiale and distal carpal, which were reconstructed withi n D i noMorph). Three superim-

rnotion is curiouslr' linritccl (Carpenter :rnd Sniith 2001), n hen each forelirrb is extended laterallr, n'ith elbon'straight and nianus extended as u'cll. the arrangerrent resen.rbles a jack stand (or a pair of bio'cle kick stancls). Thc stout forelirrbs, fullr crtended arrcl acting as stnrts anchore d into the grouncl br strong rrrilrrLr:rl unguais (rvhich :rre also n ell orienteci for this anclioring task), are ricll placecl for stabilizing thc anterior of this giar-rt theropod in preparation for rising. As the animal shills its ri'eight, ground rcaction forces n,orrlcl have been directed ncarlv perpendicularlr, into the cup shape of the glenoid fossa; the cornprcssive loacl ri,oulcl then distribute alor-rg the scapulocoracoid over a spari of ribs. If thc stout forelimbs ri'ere incleed involvecl in stabilizing the bodr', it is noteriorthr that the ground reaction forces norild have cornrrunicatecl directlr to tlrc vicinitv of the acrorrion process of the coracoicl, and therefore place the ftrrcula, u.hich is dircctlv alignccl n'ith this force r,ector, rrncler sigrificant bending stress. As notecl bv others (Larson 2001; l,arson and Rigbr 2005; Lipkin and Carpenter this l'olune; Rothschild and \'lolrar this volurnc), the frrrcrila is frequenth found n'ith eviclence of healecl stress fractures and breaks. The sprint start cliscussed earlicr u'ould havc been assistccl br braced and stabilizimg thc anterior portion of the boch, b1' holcling the forelinibs strutlike . Indeecl. the resertrblance of the initial pose to that of :r liunan sprinte r is striking (Fig. 11.10). Alternativeh; n'ith tl-re forelirnbs serving to anchor the animal, the posterior rnusculature of the hind iin-rbs could conic into plar n'rore graduallr'to elevate thc CON4 even thougl-r itn'as locatecl :rhead of the hind f-eet. \Vith the animal's rieight positione d fractionallr betn'e e n anchored forelirnbs and ertending hind lirnbs, the CON'{ cotrld be cler,ated ri'itli the aclclition:rl mechanical aclvantage of a second-class lever. Thc anirral ri'oulcl remain in a stable cy-r:rdrr-rpedal stance during this initial stage of elelation, ancl progressivelr, as the f-emora ancl knee corne out of the clecp crouch, the nicchanical :rdvantage oithe iarge fenoral retractors ancl knee extensors uor-rlcl have increasecl. Ii not intencling a sprint start. bLrt urerelv w'ishing to regain a stanclKent

A S:=.:'s et al.

ing posture, the great theropod rvould likell hal'e (1) tipped forr,r,ard slightlv, pivoting about the prepubis, trntil (2) the forelimbs u,ere in ground contact ar-rd helping to anchor the giant, then (3) it r,r,or,rld har.'e first raised its rurnp, much as large herbivores do todal', then (4) either step into forn,ard rnovernent or ascencled s1''rnrnetricallf into a standing posture.

Unlike qr-radrupeds such :rs bovids, the disparity betu'een forelimb and Irind lirirb length in 'll,rannosaurtLs rex limited the extent to rvhich it could ascend rurnp first r,r'hile nraintaining a purchase on the ground n,ith the forelimbs. Before achieving fr-rll extension of the hind limb, the anin'ral would l-rave had to break contact bett'een its forelinbs ar-rd tl-re ground, and eitiier take a step w'ith one hind limb in order to regain its balance, or remaln syrninetricallv posed on 2 hind lirnbs, and bv means of momentum, bodr,' moverrents, and strer-rgth, bring the COM back betu'een the hind feet. Perhaps the furcula ir-rjuries refleci rnishaps that occurred rvhile attenrpting to regain its balance, particularlr'u,hen larne as a resr-rlt of other injuries, or thev rna,v reflect the amount of stress imposed on the shoulder girdle during these

rlaneuvers. In the e.,'ent of a n-risstep or other failure to achieve balance between tl-re hindfeet, 4 or more metric tonnes falling on the forelirnbs could

^^-^A ^^-^. poseo poses are a5i--a: symmetilcally by left anc right forelimbs. With elDOWS and manus extended, the forelimbs can

l^-1, -+^^)ru +^ -+^ dL t d) d /dLn JLdr LU >Ld-

bilize the body during ascent, but the line of action of the ground reaction force would have placed the furcula under significant bending strest consEtent with commonly observed healed fractures. Forelimb range of motion estimated i n collabora -

tion with Kenneth Carpenter.

have precipitated such fractr-rres.

The great bulk of an aclult -fi)rdnnosduruE rex \\:as capable of being gracefully lor'r'erecl until it settlcd its weight on the elongate pubic boot, freeing the animal to adjr,rst its legs mnch as a sports spectator r.r'ould use a portable oneleggecl stool. When it carre to rising again to a bipedal stance, the options, particularll'for a sn-rall tvrannosaurid, would be a sprint start u'ith or u,ithout assistance fror-r.r the forelirnbs, or a more gradr,ral elevation usir-rg the hind limbs during u'hich the forelimbs plaved an essential role. 'l'he latter w,as en-

Conclusion

ergeticalh'rrore efficient and nright have been preferable for the adult. The forelimbs rvere literallv pii'otal in this operation, and mishaps rnight have resultecl in transmissiorr of enormous compressive forces on the pectoral girdies

and the delicate furcr-rla that spanned the :icromion processes. Although it was perl-raps ungainlr for the t1'rant king to rise rr.rmp first, its ascent u'as likeli' rnore elegant than th:rt of rrodern bor,ids rising irorl repose. Rex, Sit

201

Kent A. Stevens et al

We are gr:rteltrl b Rav Wilhite for digitization of T rer bones usecl ir-r tl-rrs studg ar-rd to the Black Hiils Instiiute of Geologic Research for hosting the 100Years ofTtrarntosctrLrusrex51 n.rposiurnandforprovidingaccesstospecimens. 'l'hanks also to Phillip \Ianning, Yoshio Ito, ar-rd Kenneth Carpenter for helpful sugge stiorrs regarcling range of motion and rnovements.

Acknowledgments

Alerander, R. N{cN. 1989. Dr.namics of Dinosaurs and Otlrcr Extinct Ciants. Colunrbia University Press, Neri \brk. Carpenter, K. 2002. Fbrelirlb biornechanics of nonavian theropocl dinosaurs in predation. S e ncke nb er giana Lethae a 82: 59 -7 6. Carpenter, K., and Smith, NI. 2001. Forelimb osteologr,and biorr.rechanics of T)'rannosatLrus rex. P.90-116 in Tanke, D., and Carpenter, K. (eds.). Mesczoic Yertebrate Life. Indiana Unir.ersitl Press, Indiana. Cr-rrrie, P. J., Koppelhus. E. B., Shugar, NI. A., and \\,tight, J. L. 200,1. Feathered D ragotts. Ind iana LIn iversrtl Press, Bloon-rin gton. Cauthier-Pilters, H., and Daag, A. I. 1981.T|rc CarneL ltsEcologt.Behayior and Relationship to I'Ian. Unir ersitv of Chicago Press, Chicago. Gierliriski, G., l,ockler; NI., ancl N1ilner, A. R.C. 2005. Traces of earlv Jurassic crotrchrng dinosaurs. P. l inTiackingDinosaur Origins: TlrcTriassicllurassic

References Cited

TerrestrialTransition Abstract\lolunte. Dirie State College, St. George, LIT. Estinating the masscs and centers of nrass of extinct arrinr:rls br' 3-D niathernaiical slicir.rg. Paleobiologt 25: 88-106. Horner, l. R., and Lessenr, D. 1991. The Complete T rsx. Simon & Schuster, Neu,York. Hutchinson, J. R., ancl Garci:r, NI. 2002. 'I\'rannosaunts u'as not:r fast runner. Nature 115:1018-1021. lenkins, F. A., Dial, K. P., and Goslou, G. E. 1988. A cineradiographic analr,sis of bird flight: the rr ishbone is a spring. Science 241: 1495-1.198. L:rnrbe, L. N4. 191;. The Cretttceous Theropodous Dinosaur Corgosaurus. Canacla Department of \lrnes, Ceologic Surver.of Canacla, Nlenioir 100. Larson, P L. 2001. Paleopathologies in Tlrannosdurus rex (in Jap:rnese). Dino Henclerson, D. N{. 1999.

Press

i: 26-1i.

Larsorr, P. L., and Donnan, K. 2002. Rex Appeal: The Amazing Stort of Sue, the DinosatLr that Changed Scierrce, the Law artd NLt,Life. Invisible Cities Press,

Nlontpelier, \/T. L,:rrson, P L., and Rigbr', K., Jr. 2005. Tfre fr-rrcula of'firarntosaurus rex. P.24 t-255 in Carpenter, K. (ecl.l. Caniyorous DinosatLrs. Lrdiana L.lniversitr.Press, Bloonrir-rgton.

Nltrlbridge , E. 1899. Arimals in \.Iotiott. London: Chapman & Hall. Dover re-

print,

1957.

Nervnran, B. H. 1970. Stance ancl gait in the flesh-eating dinosaur Ttrannosaurus. Bioktgical lounnl of tlrc Linnean Societt 2: Il9-123. Norm:rn, D. 1991. Dinosar-Lr! Prentice Hall Cleneral Reference. Nen York. Osborn, H. F. 1906. Ti,rannosaurus, Upper Cretaceorrs carnil'orons dinosaur. Bulletin of the Anrcrican N[ttsetLnt of Natural Histort 22:281-296. Paul, Cl. S. 1988. Predatorr Dinosaurs of the \\rorld. Ncri \brk Acaclernv of Sciences. Ne\\,York. Steverts, K. A. 2002. L)inoNlorph: parametric modcling of skeletal structures. Senckenbersiana Letl'Laea 82( l): 23-34.

Rex, Sit

Figure 1 1 .10 Ele tar o' the posteriar whtle archoring the anrer,o. cc:.. by the forelimb1 creatrng a pose much like a sprtnt

-'

start. The mechantcal advantage of a secondclass lever is provided during extension of the hind ilmbs in raising the COM. With sufficient elevation ach ieved, the animal could push back and regain bipedal balance, and complete its -+-^J;^^t9 o)LEr /( (u a- )Ldtluil

pose.

Fiat

ra 1) 1

Crn<< <ertion

through digits of a tridactyl Middle lurassic theronarl frarlz frnm tho laltF o rm ation, Wh itby, UK. Scale bar = 5 cm.

v/ | c k

Phillip

L Manning

T. REX SPEED TRAP

12

Phillip L. Manning

Tl-re underlving assumpticln of manv track interpretations is ihat lr,hat is preserved represents a surface trace. Track geometrv and rnorphologl, (e.g., irack lengtl-r lFLl and track n'idth IfW], digit length, number of digits, ir-r-

Introduction

terdigital angles) are based on lr,hat is visible, often recorded as a 2-dirnensional (2D) feature. The pages of this vol,rrre recorcl inforrnation on conplex 3-dirner-rsional (3D) bones, but fossil bones are defined bv obi'ior-rs boundaries. 'liacks are not. The tracks of dinosaurs are trull' the icebergs of the ichnological u'orlcl, rvith the majoritv of the structure expressed bclolv the track surface horizon. The fossil record rarelv offers n'rore than a 2D slice of this corrpiex mtiltitiered structure (fig. 12.1). Although this surface trace provides an opportunitl,to rnap the track (another source of error rvhen defining r.r'hich part of a surface to neasure), it is the relationship to underlving transrnitted track surfaces that is the ke1,to unlocking tlris 3D pttzzle. A fossil track is rrore than a simple 2D outline; the1, s1. conplex 3D structures that har,e vohrne that can be visualized as 3D failure envelopes (Nlargetts et al. in press). Laboratorv track sirnulations can provide son-re insight to the complex strbsurface sedimer-rt deforn'ration associated rvith track forr-r-ration (Allerr 1989, 1997; Gatesr,'et al. 1999, 2005; N,{anning 2004). The recoverv of subsurface la1'ers provides insigl-rt to irack morphologt'relatir.'e to the tnre surface track. When corrpared with fossil tracks and the tracks of ertant al.ian

theropods (bircl$, a rnore con-rplete understanding of tracks and tl-reir formation can be undertakerr. The tracks and tracku'a-vs of theropod dinosaurs are conmon in the Nllesozoic ancl can provide useful data on the locomotor abilitv of large preclators. Hower,er, speed estirnates calculatecl from the tracku'at's of large tl-reropods can potentiallr, under- or overestirrate the speed (u) at i"'hicl'r an anirnal u'as trar,'eling, if the FL (used to calculate hip heiglit) is misinterpreted. I exanine track maker anatomv and gait, fossil and laboratorv-sinulateci tracks, the con-rplexities of track formation, track preservation, and lvhat understar-rdir-rg can be gained frorr this dynamic sor,rrce of information.

The

stud1, of vertebrate tracks and traces, r,'ertebrate paleoichnologv, has

largell'conceniratecl on describing a trace, often u'ith little or no interpretation of the forrnation or preservation of that trace. It is surprising hor,i'sucl-r an important and revcaling area of trace fossil interpretation is so sparsell' represented in past literature. Hor,r'ever, seek and rou shall find!

T rov (naori l.rrn

Historical Tracks

Figure 12.2. Edward l.lite hrnrlz

Cnt trfocrt af

the Pratt Museum, Amherst College, Massachusetts.

\\,'illiam Buckland '"r'as thc first to ur-iclertake laboratorv experiments to help interpret the origin of a fossil trackn'ar (Sarjeant 1974; Pen-rberton and Gingris 2003). Buckland's "culin:rrr"' approach to cieciphering the iclentitv of ti-re track maker n:rs sirnple. Ile persuaclecl a crocodile and theil a tortoise to liaik:rcross:l soft piecnrst (presuurablv macle of clough) and then over u'ct sancl and soft clar'. 'l'he rcsulting inpressiorrs left Buckland in no cloubt that a tortoise had left tlie fossil trackn ar'(Duncan 1831), r'ielding the first of rnanl ichnospecie s, 'l'esttLclo duncarLi (Sarjcant 1990; Pemberton and Gingris 2003). Irclu'arcl Hitchcock (Fig. 12.2) shoulcl be consiclere cl tl'rc father of dinosaur ichnolog\', even thor-rgh he thought his tracks nere traces of ancient giant birds. Ilonever, it is quite ironic that in the Zlst centurr', Hoxdl2 lnd Hoxdl3 genes fVirrgas and Fallon 2005)have provecl hin partialli'right. Phillip

L Manntng

Hitcl-icock macle manl' smart observations on the presen,atior-r of tracks Lor,i'er Jurassic rocks of the Connecticut Vallev, USA. The n'rost actrte of his observations i,i as that he recosnized transrnitted tracks and illustrated a stacked sequence of tracks lHitchcock IB58). 'fhese repeated echoes of tl-re surface trace in successi."'e subsurface lavers q'ere founcl cornnlonlv anong the Colinecticut Valle,v tracks. He referred to these lavers, often phvsicallv bound together like sionv books, as his "fossil volumes" (Hitchcock 18i8). These volunes rvere recogr-rized as a dy'r-ramic record of rlovement, as Hitchcock rerrarkecl on the anterior travel of transnrittecl tracks relative to the surface track. It rvould take over a hundred 1,ears before ichnologists u'ould begin to recognize the significance of what Hitchcock (1858) hacl correctlv interpretecl.

fron the

'friassic tracks fron'r N,lilford, NJ, led Baird (1957) to conclude that tracks and trackr,vavs u'ere not just a sin'rple record of anatornt', but one that belal's

the nor,'erlent of the foot on, and in sone cases thror-rgh, sediment. Baird sau' track formation as a dvnamic ir-rteraction that rvas in tnrn controllecl bv srrbstrirle

1r

pe.

Alien (1989) used the mechanical inclenter theorr' (Calladine

Hill

1969;

al. 1982) to interpret fossil tracks, supported bv cornplementarv scaled laboratorv experintents. He usecl a circr-rlar indent or-r 1971; fohrrson et

lan-rinated piasticine anci sectioned the restrltant tracks to display the distribtrtion of sr-rbsurface track features. He noted that the undertraces in his experiments \\:ere a sr-rbstantiailr' less perfect record of the shape and size

of the face of the indenter, and concluded that ger-reral indenter theori; complernented bv laboraton'erperiments, cor-rld proi'ide insight to the forr-nation and preserr':rtion of ',,ertebrate tracks and trackwat,s.

The most conrprehensive studv on the rnechanics of the forntatiorr, presenation, ancl the clistribution of vertebrate tracks r,vas also unclertaken b1'Allen (1997). Tl-re studr, looked in detail at subfossil mammalian tracks frorr Fiandrian deposits in the Severn Estuarr', Southu,est Britain. Allen (1997) suggested that understanding tl-re nechanics of track making and the taphononv of traccs has continuecl to lag behind the descriptions of anatomical aspects ar-rd the distribution of tracks, despite its reler,ance in taxonom'1'and ecological interpretations. The 2 approaches used in interpreting the rnechanics of track forrnation can be dir,ided into tl-rose that use live anirrials w'alking over preparecl substrates (NIcKee 19,17; Iiarlor,i, 1989; Padian and Olsen 1984, l9B9) and the application of indenter theory as first undertaken br,'Allen (1989). Allen (1997) continued the experimer-rtal laboratorl'approach to a theoretic:rl mechanic:rl n-rodel as a rneans of interpreting and understanding vertebrate track preserr,'ation and l'rorphologl'. He suggested that the model of mechanical theory offered a liumber of insights into the likely' character of animal tracks in the field. He found that the use of an indentecl plastic rnaterial in laboratorv tests u'as supported br,results that qualitativeh, reproduced all the essential feaiures ofreal tracks. The distribution and presenation of subfossil tracks in the Seven-r Estuarv are presentecl in outcrop in several different rnocles as undertraces of varving degrees of cletail, as overtraces frorli a range of le','els in the shafts, T rov (nood Tr:n

emptied shafts, and as tracks. Allen (1997) iroted that onll'a small proportion of tracks ir-r tl-re area rvere capable of y'ielding unchallengeable taxonomic inforrration about the animais that made then-r. The indenter n-rodel, cor-rpled rvith laboratory and field experin-rents, provided a robr,rst means to test the inforn-iation recoverable from the fossil track record; horvever, it was suggested that furtl-rer study was reqr-rired to perrnit more solid taxonomic, ecological, and environmental inferences about ertinct as

species (Allen 1997). Reviews on the historv of vertebrate track ichnologv can be for-rnd in Sarjeant (i974) and Thulborn (i990). Although tl're use of laboratory studies to interpret the formation and preservation of dir-rosaur tracks has been limited, the multidisciplir-rarv approach Padian and Olser-r (1984) suggested, i,vhich uses anatom,v, kinernatics, and the nature of the sr-rbstrate to

interpret tracks, should have been ernbraced b,v the ichnoiogical rvorld. It was not, trntil r,er)'recentlr,-. Excellent progress is norv beir-rg n'rade with computer-aided ichnologl'. Stephen Gatesy's work brings ichnology firmlf into ihe 21st centurr,(Gates1, 2001, 2003; Cates.v et al. 1999, 2005). He recognized the complex surface relief of Triassic tracks frorn East Greenland could replay the movements of the limbs that created the tracks (Gatesy et al. 1999). We will return to Gatesy's splendid r.vork later ir-r this chapter. While I r,r,as happilv cl-rasing emu, generating experimental tracks and hunting vertebrate traces irr the field, jesper Milin was doing likelvise in Denmark. His research (Mildn 2003; MilSn et al. 2004) clearlv demonstrates the value of experimental work when interpreting fossil tracks. Although laboratorv tracks are r-rseful, it n'rust not be forgotten that their ftrnction is to aid tl-ie interpretation of fossil ones. It is a little stirprising, but giver-r that vertebrate icl-rnology' has close to 2 centuries of historr', tvrannosaur tracks are conspicLlolls bv their raritv.

T.

rex Tracks

Trrannosaurus tracks are rare in the fossil record. N{anv tracks initially identified as being rnade b1'7. rexhave subsequentll'been icler-rtified as belonging to their prev: l-radrosaurs! Tracks that n'ere allegedly made bv T rex from tl-re Mesa Verde Group of Carbon Countv, UT, r.r'ere given the suitable ich r-rospe cies Tyrannos auro pu s ( Haubold 1 97 1 ). Horvever, subsequent research (Lockley and Hunt 1995) has shon,n this ichnospecies could not lrave been niade b1' T. rex.'lhe N{esa Verde Group is too old (Campanian) to have the iracks of T. rex, and rnost workers agree that the large tridactyl tracks found belonged to a hadrosar-rr. However, ttie ichnospe ciesTyrannosauropus stands-an unfortunate assignment for a l-iadrosar-rr track. Tl-re tracks of T. rex (Fig. 12.3.) har,'e been described from the late Cre-

taceous Lararnie (Colarado) and Rator-r Fbrnrations (Northern Mexico), namecl \,rannosauripus pillmorei (Lockiel' and Hunt 1994). The Raton Formation track displavs several features that n-iight be expected for one made b1'7. rex-length (0.85 rn long) that exceeds width and a clear hallux irnpression-ancl to date, 'I'. rex is the onlv large theropod tl-rat fits this track in the late Cretaceor,rs (Lockley and Hur-rt 1994). 'l'he existence of a'1. rex Phillip

L Manning

track is irrportar-rt for ichnologists, br-rt unfortunatell; it is verr,mr:ch in the singtrlar. A trackn'av ol a T. rex had not been identified until recently. The Biack Hills Institute of Geologic Research has recognizecl a series of theropod trackrvavs in the Lance Formatior.r (N,laastrichtiar-r, Upper Cretaceor,rs) of \V1'oming. Sorne of the tracku,ar.s have been ir-rterpreted as being nade bv a tvranno.aur (Peter Larson, personal communication). The large (0.83 m FL) tridactl'l tracks har,c lon'relief, almost certainlr,represent trar-rsnitted features, and are preserved in fine- to mediunr-grained sandstone (Fig. 12.1A). T'her are associated (on tl-re same bedding plane) rn,itlr srnaller oviraptorid-tvpe tracks (Fig. l2 48) and large hadrosatrrine tracks (fig. 12 aC), displaling concentric shear failure (N4anning 1999, 2004) Tl-ie Lance Forn-ration tracks, althotrgh important, do not ha'"'e anv of the ar.rin'rals breaking into rults, merelv lvalking across the substrate. These tracki,r'avs lvill be the focr:s of future research and rvill certainlv add rliore

T. rex Speed Trap

Figure 12.3. Tyrannosauri pus pi I I mo rei (Lockley and Hunt 1994). Footprint (eft) and cast

(right). Scale bar = 50 cm.

Figure 12.4, (A) Tyrannosaurus rex track? (B) Oviraptorid dinosaur track (C) Hadrosaur track d isplayi ng concentric shea r fa I u re. Lance Formation, Wyoming. Scale bar = 5 cm. r

Figure 12.5. Mongolian theropod trackway. Trackway on left with

to or,rr knolr'ledge of this dinosaur assemblage. Althor-rgh tracks of rnediun'r to large theropocls attair-ring significant speeds are rare, thev are krioir,n

latex cast of trackway on

right. Courtesy of Yoshiki Koda.

Anatomy of Locomotion

(Farlow l9B1; Viera and'lbrres 1995). Ar-r additionai series of theropod trackn'avs recentlv for-rnd in \'{ongolia sr,rpport il-rat some mediumJarge theropods were capable of rr-rnning at rnoderate to higl-r speeds (Fig. 12.5). The fossil tracku,avs of the theropod thip height fhl I.27-I.71 rr) from lnr-rer N,Iongolia potentiallv shon's an anirnal rrovirlg at 7.15-10.6 mls (25.t--38 km/h)-relativell'fast for sucl-i a large anirr-ral! Is it possrble thatT. rex rright also have achieied such speeds? The follou'ing sections rvill begin to unpick a con-rplicated stort' of anatomy, lirnb rrovernent (kinematic$, and substrates, a storl'that holcls n'ianv clues to unraveling some of the secrets locked r.l'itfrin tracks and trackrvavs oftheropods and other bipedal dinosaurs.

The running abilitv of T rex has had a checkered histon'that is based on body fossil eviclence, frotn a sprinting, cr-irsorial preclator (Paui 1998; Sellers and Manning, in preparation) to a graviportal scavenger (Horner ar-rd Lessen-t 1993). The running abilitl'of ar-ry organism is intimatelt,tied to the anatomv of the anirnal. The relaiionship betlveen anatomv and locon.rotion was rec-

210

Phillio L. Mannino

ognized as far back as the fifth centur1,e.c., bi Aristotle (Padian 1995). The forrn of r.'ertebrate skeletor-rs l-ras a direct infuence on lirlib ftrr-rction because bones pror,ides the ar-rchor poiilts for the tendons, musculature, and ligaments that drive locor-notion and delineates the degree of movernent. The body,'fossil record preserves inforn'iation on the skeletal altatoill\,, size, and inferred gait (basecl on joint articulation and geometrv) of sorne dinosaurs. 'l'his has enabled n'orkers to generate functional rnodels and to reconstruct tlre loconrotion for soine dinosaurs (Romer l9B, 1927,1956; \\/alker 1977; Tarsitano 1983: Alerander 1996; Jol-rnson ancl C)strorr 1995; Farlon'et al. 2000; fones et al. 2000; Bier,r,ener 2002; Hutcliinson and Garcia 2002; Carrano and Hutchinson 2002; Hutchinson 2004). T. rex, alo:ngn,ith all theropods, riere obligator_v bipeds.'l'he majorit,v of theropods u'alked on 3 toes (tridactr'l), but some retained i,estigial digits I and V. The phaiangeal forrnulae rernain remarkablr.,conservati\re for the group and its descendants, tlie bircls (l prefer the tern't aviarL theropods). Like rnanv other dinosaurs, theropods stood, lr,alked, ran, and jurnped on their toes (digiiigrade),like reptilian prima ballerinas, u'ith bite! The metaiarsi varied considerabl,v in forrn, ultimatel,v fusing in the derived ar,'ian

condition (tarsometatarsus). The tl"reropod skeleton shares manv features among tetrapocls, such as the common possession of specific bones in the manus (hand) and pes (foot). Some of these features prol'ide useful homologor:s characters u,hen tracing theropod evolution, as \\'ell as the associated evolution of the locornotor trends in more clistant grorlps (Parrish l986). Analogotls charzlcters sl-rared bv distinct groups with separate evolutionarl, lineages can also provide trseful conparative inforrnation on the forrn and function of indepenclenth' evolved characters (Gates1, and Biervener 1991).

The prin-rarv corrrponents of the tetrapod skeleton concerned u'ith locornotion are the limbs and their attachments. Hor,vever, before n'e discuss the lirnbs, it is i,i,orth considering storage of energv rvithin an organism in relation to locomotion. I,Iuscular energy is of prime importance contributing to locomotiorr, but the r,'ertebral column and the flexibiliti' of bones ir-r almost the r,vhole skeleton are an important passir,'e conponent (Alexancler et al. 1985).'l'he r,'ertebrai collunn of rnarrrnals is quite different fron-r ihat of rei;tiles, but git'en the similarities in gait ar-rcl posture to dinosaurs, it seerns quite likelv that their vertebral coir-rrrn (as in all tetrapocls) plar.'ed an inportant role ir-r locomotion. 'fhe tendons that braced the backs of manv dinosaurs r'vould have plaved a crucial role ir-r storing energy for ]ocorr.rotion, as thev do todav for mammals, from shreu's to elepl-rants (Sellers and N,fanning, in preparation 2006). It has been suggested that back tendons account for about 70% of the total strain energv stored in the vertebral column, muscles con-

tribute about 10%, and the elasticity'of tl-re vertebrae themselves accounts for abort 20% (McGo',r,ar-r 1999). Pr-rt sirrpl1,, bones provicle a framenork for nruscles to delir,er their u'ork, but to fullv understand the energr, inputs to locomotion, a ri'hole-organism approach is ideal. 'l'he phi sical and rrechanlcal prope rties of bone, muscle, tendon, ligament. keratin, and other biomaterials ail ha'u,e a role to plav and nrust be accounted for ivhen unraveling the locomotorv abilities of extilict anin-rals. I rov \noad

rEn

211

Figure 12.6. Tyrannosaurus Stan. Stan shows a typical skeletal layout for many large theropod dinosaurs.

'l'heropod skeletons displar tr,pical form erpected for a terrestrial cursorial tetrapod (albeit a biped), but thc postrrre of the lin'rbs is not tvpical for rcptiles, bv the degree of adduction of the hind linrb, alloning an erect, or p:rrasagittal, posturc ancl resuitant gait (Fig. 12.6).'fhe crcct posture, in ri,hich the plane of the lcgs is perpendicular to the pl:rne of thc torso, has the limbs slung under the boclr in a tvpicallv avian or u:rmmali:rn postttre.

Tracking Extant Avian Theropods

Theropod descer-rdants, the birds, fom-r a diversc dcrived group. but the anatornv of their feet ancl lirribs renains relativeh.'conscrr':rtive and similar to their ancestors. I'loriever. the loss of the dinosauri:rn tail ar-rd thc cleveloprlient of flight resulted in rrajor reorganization of the peli'ic girdlc (Hutcliinson 2001). The manr.outcottres of tliis reorganization incltrde :rn :rnterior shift in the center of m:rss ancl alterecl linrb kinerrratics to corriperrsate for thc o'oltrtionan,changes (Catesl 1990, 1991, 199it. Bircls hai'e adoptecl tlie derived kneeJrased retraction mech:rnism for locon-rotion (Gatesv 1990, 1991, 1995r Catcsv and Bicn'cncr l99i), naking

thern poor analogLres for calculating the position, articulation, and rel:rtrr,e lirlb angles of theropod dinosaurs. Hon'ever, lnrnrans have aclopted a hipbased rctraction rnechanisrn, functionalli corrip:rrable u ith most large theropocls (Gatesr' 1990, i991, 1995; Gatesi'ancl Bien'ener 1991). The lirnb angle positions, relative to the grotrnd, fbr a human varv frorn 73"-> to 74" at heeldon,n phase to I18"-> to 124" at toe-off phase of thc step clcle. The lirrb posture for the hip-based retraction mechanism of htrrnans has been used to sinrulate the linib posture angles in laboratorr.sinulated dinosatrr tracks (N,Ianning 1999.2004). Fbssil tracks can clisplav evidence of a 3-phase distorted force bulb, inferring a heel-dou.n, roll forri'ard, and toe-off phase during track fornration, supporting a hip-b:rsed retractor mechanism for some theropocls. Triassic theropocl tracks from (]reenland (Clatesr et al. 1999) also clenronstrate that track rrorphologv can eltrcidate the tnoveuent of the step ci,cle tl.rat created tfrem.

Theropods: A Moving Experience 212

The step crcle of a hurnan c:rn bc evaluatecl bt'our brains, given tlrat ne are quite fanriliar u'ith the gait and nrove ntcnts adopted

Phillia L. Mannrno

lx'our

ou n species.

Dinosatrr gait ancl mor,'ement are problematic, given thet' are predominantlr,based on fragrnentan,fossil ei.,idence. Hot'e\,er, r-noverrent is a function of the organism's linb anatomr., joint articulation, der,'elopment and disiribution of musculatnre, and geometrr'. Constraining the limb kinematics for a particr-rlar dinosaur is fraught nith difficulties, not least of rihich is the fact that no lir.,ir-rg relative qr-rite n'alks the n'alk of a dinosaur (Nlanning et al. 2006). It might be possible to infer sone of the loconotor abilitr', gait, and so on by appli'ing the principle of extant phvlogcr-rtic bracketing (EPB) (Witrner 1995). N{ight it then be possible to bracket the potential range of locornotor sti'les and abilities of dinosaurs? Given that clinosaurs fall in the EPB of extant birds and crocodilians, this teclinique infers the locomotor str'les and abilities, like anaton'iv, phvsiologi,', and biologr', r'nigl-rt also be constrained bv the extant group. Reconstnrctions of the pell'ic and hind limb n-rusculatue of T. rex (Carrano and Htrtchinson 2002) have proven how,useful the EPB is rvhen unraveling complex soft tissue relationships. Combining EPB u'ith obseri.'ations of theropod anatorrn' (Carrano and Hutchinson 2002) ancl track data (Gatesl et al. 1999; N'Iannir-rg 1999, 2004) indicates that it is possible to reconstruct gait patterns anci mor,ement. Once gait pattern and lirrb rrorrernelit are constralned, it is possible to begir-r tl-re process of resurrecting a ti-reropod step cvcle and the processes that result in track forrnation. The par t of an aninral's step o'cle r.vhere the foot is in contact rvith tl-re ground is knon'n as the support pl-rase (Gatesv and Bien'ener l99l). It is during the support phase of loconotiorr that a track is forned. 'l'he initial angle at lr.'hich the foot makes contact n,ith the ground aliers, increasing as the ar-iirnal's bodr.rnoves ovcr the foot to the toe-off phase of the step cvcle. The foot-don'n and toe-off phase of the step o'cle hai.'e been strrdied bv several n'orkers (Clark and Alexander 1975; NtlcN{ahon 1984; Tl'rulborn and Wade i989; Padian ancl Olser-r l9B9; Gatesl' 1990; Gatesl'and Bieu,ener 1991) for different species of anirral, inch-rding humans and ratite avian theropods. T-he knee flexion in birds functions similarly to I'rip extension in hurrans, providing the principal angrrlar joint displacement by rvl-rich the bodv is moved foru'ard (Cracraft l97l; Jacobson and Holh'dav 1982). The angle of the action of force acting on a foot at the heel-dolvn phase of a linib cycle appears renarkably sirnilar ar-nong living bipedal anrn-rals (Catesv and Biewener I99i), u,'ith r.'ariation betr,"'een 56'-> ar-rd 73' to tl-re ground, depending on the tvpe of anirnal and the speed at u,hich it -l'l-re was traveling. angle to n,hicl-r the limb rotates forward before the toeoff pl-rase of the step c),cle also sholr,s little variation betu'een ser,'eral iiving bipedal animals, betu'eerr 106"-> to 138" to the gror-rnd. Variatior-r in the step cvcle limb position angles r,r'as greatest in birds, ranging frorn 56o-> to 63" at heel-dow'n to 106'-> to IJ8'at toe-off phase of the step o'cle. 'I'he relative position of an aninal's center of mass to the angle of the action of force acting on the foot results in variation in the distribtrtion of pressure over the sole of the foot during a step o'cle. Can this variation in pressure possibll'be one of the kevs to alk-ni the kinernatic information stored rvitl-rin a track to be unlocked?

T. rex Speed Irap

213

A Critical Eye for Walking

Experin-rental i.r,ork on tracklr,ays, coupled ivith considerations of

linb ki-

nematics and substrate conditions, permits the rnost robust inferences abor,rt track maker's and fossil footprint data (Padian and Oisen 1984, 1989; Manning 1999, 2004). It is logical that similar trackrval,s indicaie analogous kinernatics in rnany large theropods (Padian and Olsen l989). Horvever, Gatesv (199i) questioned the resoiution at r,vhich details of limb-segrner-rt orientation, kinematics, rnuscuiar anatom,v, and neuromuscular control cor-rld be addressed by means of Padian and Olsens (1989) techr-rique. He suggested that footprints coulcl not be equallv inforrlatir,e about all locornotor categories, even iftrackrvavs have helped confirm that birds retair-red the obligaiorv, digitigrade bipeclalism and l-righly addr,rcted limb postrire of their tl-reropod ancestors. Cates,v (1995) concluded that rt u'as quite possible that such bipeds could make alrnost identicai footprints even if thev differed in several locorrotor categories. He rnaintained tl-iat trackwai,'s could not provide enough detail to discrin-rir-rate betrveer-r l-ripbased (primitive theropod) and knee-based (avian theropod) limb-retraction mechanisnis. The track rnorphologv of tl-re iargest living ground birds (ratites), such as eu-u-r (Padiar-r and Oisen 1989; Nlanning 1999; N'lildn 2003; Milin et al. 2004) and ostricl-res (Farlorv 1989), allou, comparison of track morphologv generated by either avian knee-based or hip-based (primitive theropod and hr-rrnan) retraction mechanisrns b-v using laborator,v-simulaied and fossil tracks (Nlar-rning i999, 2004). Observations on the distribution of pressure across ratite feet wl-rer-r walking, inferred frorli track morpl'rologi' (Thulborn and Wade I9B9; F'arlorv 1989; Mar-rning 1999, 2004), indicate the presstrre distribution across the foot of a knee-basecl retraction nechanisir differs from a track ger-rerated bl'a hip-based retractor rrechanism. The distinct heel-dor'vn phase in laboratorv-simulated tracks aiid fossil tracks is almost abser-rt from emu and ostrich tracks (Farlow I9B9; N,{annin g1999). 'I'he l-reeldorvn phase is replaced by what can be described as a contact phase. In the contact phase, an avian theropod tests the groulrd to assisi motor control for the cornpleted step cycle (Gatesv and Biewener l99l). This enables an animal to accommodate for substratun-r heteroger-reitv during locornotion in a natural environment (Clark I9BB; Gaiesv and Bien'ener l99l), rvithout committing its u'hole mass over the foot, as with a heel-dor,vn phase of a hip-based retractor r-nechanisrn. The knee-based retraction mechanisrn appears to combine the heel-dorvn phase and rotation phase of the step o,cle (contact phase), r'i'ith the greatest force exerted at ti-re distal end of digits at the pushoff phase of the step cvcle. The variation in the distributior-r of pressr-ue across

the foot is essentiallv a bl.product of the relative positior-r of tl.re animal's center of rlass dr-rring a step cycie, as the bodl'moves over each foot and step, respectively. Tl-ris suggests, contrary to Gaiesr' (199i), that it is possible to differentiate betrveen hip- and knee-based retractor s1'sten-is from track geometrl', given that track relief (sr-rrface and subsurface) is a function of the distribution of pressure. The center of mass of a theropod dinosaur is also reflected ir-r the distribution of the animal's u,'eight on its 2 limbs. If the center of rlass is directly over the limbs of a biped, each iirrb will support an equal amount of 214

Phillip L. Mannino

r,ieight (u'her-r the animal stands stiil). Tl-re posture of a theropod clinosaur had to account for the rclative position of the center of mass to be stable, or, il4ren

ivalking, to be dy-ramicalli unstable (see Stel,ens et al. this volun're). The difference in the position of the center of rnass u,ould certainl','have had an effect on all theropod loconiotion, inclucling sitting, standing, n'alking, running, ancl junping. 'l'he distribution ofprcssure exerted across the sole ofa foot can vary with subtle directional changes in the load applied during a step cvcle (N,'lanning 1999). Laboratori track sirnulations ar-rd force-plate (optical pedobaragraph) experirrents can vield useful informaiion on the substirface rr-rorphologv of tracks ancl tl-re clistribution of pressures across the sole of a foot (N,f annin g 1999,2004). 1'he varving degree to n'l-rich a digit or cligrts n'ere transnritted to deeper successil e lavers correlates lr'itfr the distribution and rnagnitude of pressure acting on the sole of a foot. Experimer-rtal pressure plate svstens have been used to track the r,ariation in the center of pressrlre during a step cvcle, rnaking it possible to correlate r.'ariatior-r in load rn'ith the restrltant distribution of pressures over time throLrgh a step cvcle (N'lanning 1999, 2004). 'l'he inplication of beir-rg able to infer the kinenatics of a step ci'cle frorn a fossil track, coupled r,r'ith the size of the anirnal and speed at rihich it n'as trar.cling, could i'icld important ir-rformation on the locomotion of all dinosaurs. The lD subsurface track record of the relatii'e magnitucle ancl distribution of pressr-rre across a foot can assist in assigning theropod tracks to a primiiive (hip-based) or derived (knee-based) locomotor s),sterr. This coulcl provicie usefr-rl data on el olutiolarl trends in theropod locomotion in the fossil track record, thus supporting the evider-rce from the bodv fossil record (Catesr 1990, 1991, 1995). It mav no\\'be possible to differentiate from L,ate Cretaceons avian theropod and bipeclal ornithopod tracks on the b:rsis of subsurface deforrnation bv the presence or absence of a heel-dori n phase di-rring locomotion. A N,Iiddle furassic theropod track frorn the Scalbl' F'ornation, Yorkshire, UK, provides an ex:rmple of a 3-phase track ('l'hulborn and \Vade I989) (Fig. 12.7), u'ith features ti'picall1'erpectecl for a hip-based limb retractior-r mechanisrr (Nfanning 2004). The cross section along the meclian 1ir-rc of digit III shon's a region of clot,nriarped sediment ir-r the heel area (A), r'vhich delineates the clefomration carrsed at the l-reel-donn phase of the step o'cle (Fig. 12.7). 'fhe briclge of the foot (B) of the section of digit III delineates the seconcl forw'ard rotation phase of the step cycle (Frg. 12.7). 'l-he third and n-rost distinct point of the step cl'cle, the toe-off phase (C), is clearlv deiineatcd b1'a severelr,dou'n'nr,arped area of sedirnent larrrnae, couplcd u'ith liquefaction failure (Fig. I2.7).'fhe track displavs all 3 pl-rases of a step o,'cle (Tl'rulborn ancl \\'ade 1989) that n'ould be expected for a hip-based retractor rrechanisrr, tvpical of a N{iddle Jurassic theropod clinosaur (N,'lanning 1999, 2004). 'lb test tlris h1'pothesis further ivoulcl require the sectior-ring of manl' coniplete fossii tracks from the Jurassic and Cretaceous, to compare and contrast the distribution ofpressure across the foot in relation to subsurface featr-rres, n4rich n,ill (curators n'illine) be the subject of future rvork.

T. rex Speed Trap

215

Figure 12.7. Cross section along medial line of digit lll from a Middle Jurassic theropod track, Scalby Formation, Burniston, lll( Araa< A f^ a ranro<enf nh:cp< nf fha
=

10 cm.

Firm Grounding to Build On

Did the Earth Move

for You?

216

Prer.ious u'ork or-r dinosaur trackr'r'ays has tended to concentrate on identifi -

ing the aniural that may have produced the track, and the speed, gait, and size of the animal. The'"vav in u'hich sediments bel-rave before, dr-rring, ancl after a track is formed and the subsequent processes that mav further noclif1', enhance, or clisgtiise a track has been much neglected. 'I'he poor fossil record for T rex tracks ar-rd tracku'a1's suggests that eiiher rrore tracks must be found, or an alternative to fossil tracks be generated to studv r,r'hat potential traces might look like. A corabir-ration of laboratory'-cor.rtrollecl track sin-rulaiions, cor-rpled lvith field observations, can provide a nore corrplete understar-rding of hon' tracks are formed and preserved (Padian and Olsen 1989; Allen 1989, I997; N'larrning 1999,2004; NIihn 2001; N'lilAn et al. 2004). T'he uorphologi'of snrface and subsurface tracks rnust be studiecl n ith a r,ieil'to treating tracks as cl1'namic records of movement ancl not just static traces.

A footfall of a dinosar-rr rnechanicali',' makes dense tl-ie sedin.rent beneatl-r its foot, sornetimes resulting in failure, preser','ed as tracks. For ur:rnv vears, ichnologists have nan'ied track species (ichnospecies) at an alarrring raie using qualitative characters tliat l,ar-v greatll'from one footfall to tl-ie r-rexi. Ferv ichnospecies are sr-rpported by' laboratorr-controlled erperinients to cluar-rtif1'and qr,ralif,v interpretations of the fossil tracks. Resr-rltant ichnospecies are 2D shador,vs of what\\,'as a more cornplex JD track structure. The mechanical properties of substrate clearh'inflnence the response ancl resultant features associated w'ith a footfall. To understand the fomation and preserr.'ation of dinosaur tracks, it is essential to understand the mechanics of soils. The word soll has different meanings to n'orkers from r,'arious disciplines. The definition I r-rse here is an engineering one, defined as anv loose sedirnentarl'deposit, such as gravel, sand, clar', or a mixtr:re of these materials (Smith 1981). The size and distribution of particles that forrn a soij, corrbined rl.'ith tl-ie air or rvater occupving l'oids betr,r.'een the solid particles, affects the rnechanical properties of that soil, as does its porositl'and permeabilitl'. For example, silt-v fine- to rnediurr-grained sands have little resistance to shearing rvhen clr,v, but u,hen rnoisture content increases, so too cloes shear strength (N{anning 1999, 2004). An increase in moisture content effectir''elv increases the bulk clensitv of a sedirnent as lr"ater replaces the air contained in the voids betu,een soil particles. The denser a soil becornes,

Phillip

L Mannrng

the greater its sl-rear strength (Karafiath and No'nvatzki l97B). Horve',,er, if the n-roisture content increases be1'or-rd the soil's critical saturation point (critical hydraulic graclient), rvhere the soil particles r-ro longer come into contact as a result ofpore-rvater pressllre, the soil fails. Boussinesq (1883) solved the problern of preclicting the distribution of stress at an1, point in a hornogeneous, elastic, isotropic niedium as the result of a point load applied at the surface. Boussinesq's elastic analvsis is represented by the follon'ing equatior.r:

o,='!-rn*fd' (1) Bor-rssinesq's equation shou's a point load (P), ivith o the vertical stress at point deptli e belor.v the load at a horizontal distance r frorn the line of

action. N{annir-rg (1999, 2004) applied Boussinesq's eqr-ration to help provide insight to the distribution of pressure n'ithin a',,olume of sediment, f ielding track features. The nraxin-mm zone of deformation (N{ZD) marks the zone of influence (or failure envelope) in track fornation, and Boussinesq's equation pror,'ides the theoreticai distribution of actual pressLlre in a i'olurne of sediment. Hou'ever, Boussinesq's theorr, relates to the distribution ofa static load at depth. A track is the resuit ofa dvnarnic load; therefore, the application of Boussinesq's theon, has its lirnitations. N{anning (2004), lvho usecl a reconstructed fbot to indent constnrcted sediments. shol','ed that the use of laboratorv-generated tracks can vield important inforrnation on dl,namic sediment faih-rre.

Laboratorv-simulated tracks can provide a quantitative approach to interpreting the morphologv and spatial distribr:tion of failure in a volunre of sediment, and the associatecl secliment cor-rditions and properties at the tirre of track formation (Allen 1997; Gatesl et al. 1999; N4anning 1999, 2004; \,tlildn 2003; N4il6n et a1. 2004). Thev might also help confirm or disprove track ancl track maker relationships, given the benefits of a closed svstem and knou'ing the experimental paraneters. A quantitative test for fossil dinosaur tracks is a difficult benchmark to achieve, giver-r there are rlanv r,ariables to account for, inch-rding moisture

Making Tracks in the Laboratory

content at the tine of track forrr-iation, n'eight of the dinosaur, trtre morphology of the dinosaur's foot, ancl the exact gait of dinosaur at the time of track formation. Althougl-r these variables can be rneasured in controlled laboratorv track sirnulations, a method to preclict these variables from a fossil track has i'et to be devised. This neans that the track data produced from laboratorl,sin-rrlations can onlv be used as a qualitative guide to the conditions prevailing, and the foot rrorpfrologv of the track naker, at the tirrie of track forrnation.

A sirrple erperimental setup can proi'ide a l-rr-rge ar.nount of data on the formation, presen'ation, and sr-rbseqnent morphologv of tracks. Man217

L) ffiry$i*i:: F

Eure l2.8. Track gener-

aiecl tn a saturatecl (31

2% moisture con-

tent),

ned

r

E

F

ning (i999, 2004) derelopecl a series of erperiments to cltaractcrize and reconstruct a number of sediments to indent ri'ith a standardized, recolr-

'l'hc resultant tracks coulcl be dissected and surfacc lavers conrpared to anv subsnrfzrce cieforrnation (trallsmitted strr-rcted tridactvl theropod foot.

nd. /Ai Ottarnrinf r>ut .,,.{^-^ (rdLA 1^-+,,,^ ilt9 talc +,--1. /gd(ulg, (B) Track at -1.3 cm. (C) f i ne -g ra

',',*#l''

sa

at -3.5 cm. (D) at -4.9 cm. (E) Track at -6.3 cm. (F) Side view of constructed sediTrack

Track

ment. All scale bars tn centimeters.

tracks) (Fig. 12.8). Fron-r tl're clata recor,'erecl frou'r the erpcrinrents, it uas possiblc to plot (lr'ith Petrel softn are) tracks in 3L) shou ing the spatial relationship of surface and subsr-rrface defomation 1F'ig. I2.9;. 'l'he \lZD on each track sur-

face (Fig. 12.9A) and the relatir,e position of digiis (Fig. 12.9B) \\'ere recorclecl ancl plottecl (see \'lanning 2004). With Petrel or other sLritable r.isualization packages, it ri':rs possible to clearlv shori the spatial relationship of the track lavers n'ithin :r lolunte of seclinent for the first tir-re. 'I he erpe rinental tracks indicated that the magnitude of the N'IZD and related sedinrentarv features is in proportion to thc load applied to an isotropic seclirner-rt (\{ar-u-ring 1999, 2004). Thc N{ZD n-rarks the naximum extent of deformation t'ithin a voluure of seclin-rent. A cross section of strch dcforrnation produces a distorted onion-sh:rped force buib of inflr-rence. 'l'he deformation of tl-re force bulb is a function of the dr,n:uric nature of track fornration, providing evidence of thc direction of loacl applied to a sediruent. The clistorted force bulb can be unclistortccl br plotting the cross section of a laboratorr-sirnLrlated or fossil track ort a nornralized axis (\{an1999). 'l'he resultant cross section through the force bulb resenrbles failure trpical of a static load, in effect conforrning thc Boussinesci (1883)

ning

indenter theorr'.

218

Phillip L. Mannrng

Laboratorr-gerrerated tracks can shoil'the potential for errors in the interpretation of fossil track n'rorphologv and geornetrv. This is ritost evldent il'hen using trackrvat's to calculate the speed at ivhich the track n-raker r'r,as rnor''ing at the time of track formation, n4ren tising crucial parameters clerived from track geonretrr,.

Alexander (1976) devised a rrethod to estirriate an animai's speed from its tracks that used the knou'n parameters of stricle length ()"), and estimated parameters such as hip height (h). His fonnula could then be applied to fossil tracku'avs. Alexander used a nondinensionai parameter, the Froude nurnber, to allorv ureaningful comparisons betr,r'een aninals of varl'ing size bv means of ph1'sical similariti theorr'(Dr,rncan 1953). Phvsicai simrlaritv theon,predicts that the movernents of anirnals of geornetricalli'sinrilar forrn, but of different sizes, u'ill be geornetricallv sinilar onlv r.vhen thev mo,"'e lvith the sarne Froude nunber (i.e., r',ten the squares of their speeds are proportional to their lir-rear dimensions). Geometricallv similar rnovements require equal i alues of )"//i-that is, stride length rnust also be proportional to their linear dinrension. Alexander (1976) used stride length (),) as the distance betu'een corresponding points on snccessive tracks of the sarle foot. His equation can be u'ritte n so that speed (u) can be estimated frorn the knor,r'n 'n'altres of l" and h can be rneasured accuratelv fron.r tracks. Hip height (h) rias estimated frorn Fl,, multiph,ing Fl, bi,4 to give h. u(D\0

25s0.5\11"1 67\h-1 17\

of Speed

(2)

Holl'el'er, he recognized that in manr bipedal dinosaurs, h clicl not conform to the rule of 'tFL; some were 3.6FL to 4.3FL (Alexancler 1976). Er,'en n'ith the potential pitfalls of Alexander's (1976) nethod, it has been adopted bv nanr' (Tucker and Burchette 1977;'l'hr-rlborn and \\/ade i979; Farlor,r, 1981;

Tracks as a Measure

Thulborn 1981, I98Z; Har-rbold 198+; Lockler.et al.

1996).

The assun-rption that a dinosaurs foot has a constant relationship to h rs possiblv u'rong for J reasons. First, the ft/FL ratio is unlikelv to account for T rov \noart Tran

Fiatro 1) Q Pafral nlat< of experimental tracks clearly show the 3D surfaces that combine to create a track. (A) MZD

nlnt< /R) D;^;t

^l^t.

showi ng spatia I

re I ati on

-

ship of digit position with depth.

219

variation in geometrv betrveen dinosaur taxa (Thulbom 1990). Second, the fi/FL ratio u'ould l-rave char-rged cluring grou'th, a function of allornetry (Thulborn 1990). Third and finallv, the h/FL asslrmes that i.r'hat is rneasured from the track represents the anirnal's actual foot length, something I will discuss further shorilv. Alexander (1976) did indicate that if h were overestimated by l0%, u rvotrld be underestir-natedbv ll%. However, to create even larger discrepancies is not difficr-rlt. For example, a fossil FL of 0.10 m would give a liip height (h) of approxirratel,v 0.4 m. Ho'uvever, if the true foot length were 0.07 m, h nould be calculated as 0.28 m, rreaning the speed (u) from a trackrvav rnight be underestimated by more than 25%. Sr-rch a discrepar-rcy can easilv arise from how a track is measr-rred or by being a transmitted feature rnisinterpreted as a sr-rrface trace. Laboratory track sirlir-rlations (Manr-ring 1999, 200'1) shou' that the length and rvidih of a track can vary within an individual track, n,ith the original sllrface track feature often less rvell defined than those transn-iitted. Overprir-rt (Thulborn 1990) features can also alter track parameters ln comparison to the original surface on lvhich the anirnal left its irace. Given that dinosaur FL, and in some cases FW, are key'pararreters used to calcr-rlate l-iip height in calculations of speeds from trackrvavs, here lies a prob-

lerr (Alexand er 1976; Lockley et al. 1983; Wliat is the tme track (foot) length?

Sanz et al. l9B5; Thr-rlborn 1989).

The variation in FL is a function of the relative position of a track laver to the force bLrlb (N1ZDifailure envelope) transnitted rvithin a vcrlttme of sedirnent. The deformation of sediment beneath a foot initiall-v expands then dininishes with depth, and u'ith it the track geometry and morphology alters rvith depth. Edward Hitchcock (i858), as discussed earlier, made an enonnolrs contribution to the earlv science of vertebrate ichnology,bv recognizing transmrtted tracks. His "fossil volumes" (Hitchcock I85B) still provide useful clata u'hen comparing laboratory-simulated tracks u'ith fossil tracks. The experrrr-rental tracks shorv clearlv holr, deforned tracks are transrnitted and drstorted, as \\'ere many of Hitchcock's tracks (Fig. 12.10). FL clecreases from a-c, increases fron'r c-d, and then decreases again fron-r d-f (Fig. 12.10). The red line (Fig. I2.10) follous this irend and gives clues to that illusive parameter, true foot lengtl-r, giver-r FL is a function of true foot length. Tracks a-c represent the entrance and exit traces ofthe foot as it sunk into to the sediment forming the surface track. 'Iiack c, alihough the smallest, is closet to the origir-ral sedimer-rt-foot interlace (the floor of the footprint) and r-night represent most closell' the original foot lengtir of the track maker. Tracks d and f are transmitted tracks, conforrning to the behavior expectecl for a force bulb, increasing and then decreasing in size beneatl-r irr-ipact of the foot (F-ig. IZ.l0). Civen thai the surface track (track a) featr,rre is r-iearly )7% larger than the potential true foot length (track c), there is significant room for error, depending on which track horizon lvas used to calcr,rlate foot length, hip height, and speed of the track maker. 'fhe critical parar-neter of FL needs defining to be useful to ichnologists. FL was defined as the distance between the rnost anterior point and the rnost 220

Phillio L. Mannrna

k ffi e.

,ffi

,.ffi

-dffi M

ffi

-ffit

a {.|: >+:

:ot t3g

{l){U €;nt

Track layer depth {mm} posterior point of the tr:rck, measured parallel to the long axis of the track (Leonardi 19E7; Thulborn and Wade l9E4). The eristing definition r-rnfortr-rnatelv has the greatest l'ariation in its pararneters with deptli because the N,IZD represents the maxinum erter-rt of a track. Hon'ei'er, if theropod FL r,vere defined as the length of digit III (Nlanning 1999, 2004), a closer approxirnation can be made of the true length of digit III, and in turn, a calcr-rlation of the total FL can be made. Hou'ever, this relies on an individual recorcling FL frorr surface tracks that displar,a clearly definable middle digit

(digit III) or clear skin inipressions (Currie et al. 1990), or can be defined bv the relative position of the track's force bulb (as discussed earlier). Laboraton'track sirnr-rlations have demonstratecl that FL variation is as much a ftrnction of sedin.rent as it is of the track rnaker's foot morphology ancl size (N{anning 1999, 200'+). For example, the Tbble l2.l charts the resuits from 11 laboratorr-gencrated tracks (N'Ianning 1999). The actual length of foot (template) is a knon'n quantitr', as are the sediment characteristics and condition at tlie time of track forrration. The same amount of force \\ras applied to the foot on each track run in the sarrie step cl'cle. The percentage variation from actual foot (template) length r'"'as calculated for the maximum and ninirriun track size recovered frorn strrlace and subsurface tracks. Tl're i'ariation in track paraneters n'ith depth lr,as dependeni on the noisture content and sedinent used. Track Il (Table 12.2) and Track 10 (Table 12.3) u'ere generatcd br the same experinrental setup and sedirrent, i,vith the onl1'r,ariation being moisture content. The fine-grained sand used for both experiments il'as inclented drv (n.roisturc content 1%1 and saturated

Figure'12.10.

track (' fossi I vol u me" ). Trark< a-h r-d

botto m s u r f a ces, respectively, of 3 layers that combtne to create a

single track volume. The

plotted track outlines (af) show variation in FL with depth. The gray line (tracks a and f) marks the posteriormost point of the track, with the arrow (track f) indicating the degree of anterior travel of the track feature with increasing depth.

Track ll (satnrated sediment) shon'ed a large variation in FL frorr surface laver I to basal laver 11 (Table 12.21. ftorn 17.5 to 9.0 crn, respectivelv, a r,ariation of some I9+.4%. The length iFl,) of track l1 rl,as then usecl to calculate fi. Accordinq to Alexander 19-6t. h was 36-65.2 cm, Irap

snd a-f

represent the top and

lnroistrrre corrterrt 1071.

T. rex Speed

Ornitho-

pus g raci I io r transmitted

221

MZD

Track

Digit lll

FL

Maximum Minimum Variation Comoared Maximum Minimum Variation Compared (cm)

(cm)

with Actual

1

19

12.3

152-98.4

1

I

19

4.7

152-37.6

1

j

2A

7.4

160-59.2

-

15.4

12.4

131.2-99.2

5

16.4

10

'r

6

17.8

7

1

Simulation

(%)

(cm)

(cm)

with Actual

6.5

9.5

137-78.9

5.5

10.2

128.7-84.7

13.5

9.7

112.1-80.5

14.8

12.5

122.8-103.8

2-80

13 5

10

112.1-83

4.5

132.4-36

15.2

12.5

126.2-103.8

8.5

14.8

148-118.4

15.3

13.4

127-111.2

8

24.7

14.5

197.6-116

18.2

11

1

9

23.6

6.3

188.8-50.4

16.4

9.2

136.12-76.4

10

21.5

7.5

172-60

16.3

10.2

135.3-84.7

11

17.6

9

140.8-72

14.3

11.9

118.7-98.8

Table 12.1. Variation in

Maximum Zone of Deformation (MZD) Track Length (FL) and Digit III Compared with True Track Length (Length of Foot Template) from lndivi d u a I Track 5i m u lations

Note.-The actual length of the foot template was 12.5 cm. The actual

length of digit lll was

12.1

cm.

31

.

51

(%)

.1-91 .3

Tl-rnlborn (1990) gives h as 405-99.97 ctn, and Locklev et al. (1983) give fi as 45-105 cr-n-a poteniial variation of 291.6%, depending on nhich track layer was used. 'l'his poter-rtial variation is clearly not restricted to laboratorv-generated tracks but is present in fossil tracks (Fig. 12.10). Track l0 (drv sediment) also exhibited a large variation in FL frorr surface layer 1to basal layer II ('fable 12.3), from 21.5 to 7.5 cm, respec, tivelv, a variation of sorne 286.6%. 'l'he length (FL) of track l0 n,as tlen used to calculate fi. Accorcling to Alexancler 0976), h ranged 30-81.6 crri, Thulborn (1990) gives h as ]3.7-122.i cm, and Lockler,et al. (1983) givc h as ]7.5-129 cm-a potential variation of $0%, r,vhich clepends or-r ri.hich track laver and h estirnate method are used. If a fossil trackivav erposed relativelv deep, transrnitted tracks, equir.'alent to la-ver II of track sirnulation l0 (Table 12.3), and the FL n,as usecl to calculate /i and in turn the speed at ivhich the ar-iinal was traveling (h1,-pothetical stride length of 2 m), then the follou,ing results are obtained:

L 2.

Using lon,er linrit estination of hip height (Alexander 1976) of 30 cm, Equation 2 gives a speed of 10.29 rn/s. Using the upper limit estimatior-r of hip height (Locklev et al. 1983) of 45 cm, Equaiion 2 gir,es a speed of 6.,1 rn/s.

if the fossil trackrval exposed tl-re equivalent of lar.er 5 of track sin.rulation l0 ('lbble l2.l) and the FL n,as used to calculate /z ancl il Hower,er,

tum the

spe ed at u'hich the animal u'as tra',,eling, the hvpothetical striclc length of Z m nou, reduces to 1.86 rn as a result of tl-re increased foot length encroaching into the stride length (Fig. l2.ll) nould gir.e the follori'ing

results:

222

Phillip

L Manning

Track

'11,

Dry Fine-Grained Sand

h in Relation to

FL

(E)

65.2

73.35-92.91

81.5-97.8

14.3

57.2

64.35-81.51

71.5-85.8

17.5

70

78.75-99.97

87.

12.7

50.8

57.15-72.39

63.5-76.2

-6.3

10.6

42.4

47.7-60.42

53-63.6

-8

q

36

40.5-51

45-54

FL (cm)

h (cm) =

1

0

16.3

3

-1.6

5

?a

7

-4.9

9

l. 2.

(1990)

Lockley et al. (1983) h (cm) = FL5-6

Depth (cm)

11

('1976) Thulborn

h (cm) = FL4 5*5.7

Alexander

Layer

FL4

3

Using lou'er linit estimation of hip height (Alexander 1976) of 86 cn, Equation 2 gives a speed of 2.65 mA. Using the upper limit estimation of hip height (Locklev et al. 1983) of 129 cm, Equation 2 gives a speed of 1.65 m/s.

A fossil trackrl,al', with tracks sirrilar to those transrnitted in track simulation 10 (Fig. 12.11), creates the potential difference in speed from varl'ing track laver depths from 1.65 m/s to 10.29 n-r/s, depending on r'vhich layer and hip height values are applied. 81'comparir-rg the NIZD foot length data frorn laboratorv track simtrlations (Manning 1999, 2004), there is significant variation in track geometrv between surface ai'rd transmitted tracks. Tiack sin'rulation 10 l-ras a','ariation of up to 286.6% and simulation li a variation of up to 194.4%. 'I'he onlv paraneter altered betu,een tl-re Z r','as rroisture content; sedirnent, foot morphology, force, etc., remained constant. The higli rnoisture content 01.2%) of track simuiation I1 ir-rclicates that the MZD is reduced with higher rnois-

ture contents; effectivelr,', the sediment's bulk densit_v is higher as a result of the increased rnoisture filling the pore spaces, increasing the shear strength. It is clear that a controlling factor in the forn-ration of track features is the re-

Track 10, Dry Fine-Grained Sand (E)

Depth

(cm)

h in Relation to Alexander (1976)

FL (cm)

(cm)=fr+

h

Thulborn

5-]

05

Table 12.2. Vailailon rn Hip Height (h) Due to

Depth and Method Chosen for Estimating Hip Height (h) for Laboratory Track Simulation 11

Abbreviation.-FL, foot length.

Table 12 3. Variation in

Hip Height (h) Due to Depth and Method Chosen for Estimating h for La bo ratory Track Si m u I a -

tion

1A

Abbreviation.-FL, foot length.

FL

(1990)

Lockley et al. (1983)

h(cm)=FL4.5-5.7 h(cm)=frS-O

1

0

20.4

81.6

91.8-116.3

102-122.4

3

-1.7

20.1

804

90.45-114.6

100.5-120.6

5

)1

21.5

86

96.75-122.5

107.5-129

7

-5.3

16.5

66

74.25-94

82.5-99

9

-6.87

11.5

46

51.7-65.5

57.5-69

11

-8.43

7.5

30

33.7-42.7

37.5-45

T. rex Speed

lrap

223

4.7 cms

Figure 12.1 1. Cross sec-

tion of trackway showing variation of FL and stride length with depth. Data from track simulation 10 (Table 72.3).

lationship betweer-r moisture ar-rcl density'that prevails in a volurne of sedinrent at the time of inclentation. FW car-r also be r,rsecl to calculate hip height (Thulborn and Wacle 1984; Lockle-v et al. 1986; Thulborn 1990). Horvever, FW also varies il.'ithin indirelation to the relative position to the trr-re track sr.rrface. Anall' sis of dinosaur tracks also indicated FL rvas more variable than IiW (Thulborrr and Wade 1984), and that FL i',as the least reliable indicator of foot size. FL and FW data (N,Ianning 1999) agreed rvith that of Tliuiborn and

l'idr,ral tracks

ir-r

Wade (1984), thus sr,rpporting sinallelu'ariation in FW n'hen compared u'ith FL ('l'able i2.'f). It is clear that FW rather than FL could be r-rsed q'hen calculating the speed of a clinosaur oIr the basis of measttred paraneters from tracku'avs. The use of F-W can be fi-rrther justified if a clear relationship betrveen FW ar-rcl hip height can be established. 'l'hulbonr and Wade (1984) proposed an index of footprint size (SI), r.r,hich thev calculated bv r-rsing the FW and F L of a fossil track (expressed in the sarne units of measurernell: 5l = (FL x FW)o

s

Thulborn and Wacle (l984t applied their index of footprint size to 57 fossil trackr,r'ays (Wintonopus) frorn tl'ie Middle Cretaceotts, Winton Formatiorr, Qr,reer-rs1and, Australia. Thev concluded that the footprir-rt size index (SI), based or-r tl-ie sarnple the sanplc of 5 t- \Yhionoprrs tracki.r'avs, \\:as the rnost reliable guide to estimating the size of track niaker. 'l'he data frorn laborator]-simulatecl tracks provides the ttt-tttsual situation il'here both the track size frorr eaci'r laver of a single track volttme and the actual foot length (ten-rplate length) of the track rnaker lr'ere knorl'n 224

Phillip

L Manning

MZD TW

MZD TL

Track

Maximum

Simulation

(cm)

(cm)

1

19

12.3

2

19

3

20

4

1E

5

Minimum

Variation Compared with

Variation

Maximum Minimum Compared with

(cm)

(cm)

Actual

152-98.4

19.4

to

157.1-129.6

4.7

152-37.6

to

12.3

129.6-99.6

7.4

160-59

17

5.5

137.7-44.6

12.4

131.2-99.2

15.9

14

128.8-113.4

16.4

10

1

.2-80

19.7

8.6

159.6-69.7

6

17.8

4.5

132.4-36

16.6

3.2

134.5-25.9

7

18.5

14.8

148-118.4

16.3

136

132-110.2

B

24.7

14.5

197.6-116

18.3

14

148.2-113.4

9

23.6

6.3

188.8-50 4

18.4

6

149-48.6

10

21.5

75

172-60

19.2

12

155.5-97.2

11

17.6

9

140.8-72

20.2

1

A

Actual

3

1

FL (%)

2

naker-ir-r tl-ris case, a prosthetic theropod dinosaur foot. The inclex of footprint size (SI) u'as applied to both the maximun'r (SI.l) and minimum (SI.2) N,IZD FL and N4ZD FW data frorn N{anning (1999) (Table I2.4). The SI ri'as calcr-rlated usinq the follou,ing equations:

= (maximum MZD FL x maximum MZD FW)0s $l.l = (mininlrrn N,{ZD FL x minin'rum N,IZD lrwli'; Sl 1

The SI results for the maximnm (SI.1) and rrinimum (SI.2) were not as close to actual SI foot size as predicted bv Thulborn and Wade (1984) (Table 12.5). Horvever, if the SI.l and SI.2 l'alues n'ere treated as maxirnum and mininum 'u.alues from a trackli av ar-rd fed back thror,rgh the SI formr-rlae, a different picture emergecl. SI.l and SI.2 in effect prol,ide an index of footprint size (SI) for ar-r inclividual track (SI.3): Sl.3 = (S1.1 x Sl.2)o

163.6-85.1

0.5

qtrantities (N{anning 1999). 1'his makes it possible to test u'hether the ir-idex of footprint size (SI) rnore closelv reflects the foot geometrv of the track

Table 12.4. Vailation in

Maximum Zone of Deformation (MZD)Track Length (TL) and Track Width (TW)Compared with the True Track Length within lndividual Track Simulations

Note.-The actual foot length template T8 is 12.5 cm, The actual foot width TAmnl2TA tXt< t/ 4am

s

The estirnated value of SI.3 provided a closer estimate to the original track maker's foot size (Table I2.5). Because the true foot length and foot lvidth rvere knorvn for the terrplate that il'ere used in the laboratorv simulations, it rl'as also possible to calculate tl're true index of footprint size SI (true SI), for comparison lr,ith SI.l, SI.2, and SI.3 (Table 12.5). SI.3 represented tlre footprint size index for a]l track lavers from an individual track and could be used to estirnate hip height fron a multitiered fossil or laboratorr,.5i-.rirt.d tracku,ar,' (if all track la1'ers u'ere recor,erable).

T. rex Speed Trap

FL (%)

225

Table 12.5. lndex of Footprint Size for Laboratory-

Track Simulation (cm)

Template*

Simulated Tracks Based on Data from Table 12.4

sr.1r

sr.2 +

st.3 s

1

19.2

14.03

16.41

2

17.45

7.6

| |.)L

3

18.44

6.38

'10.85

4

15.65

13.18

14.36

5

19.97

9.27

12.9

6

17.19

3.79

8.07

7

17.37

14.19

15.7

B

21.26

14.25

17.41

9

20.84

6.15

11.32

10

20.32

o i40

13.9

11

18.86

9.72

Abbreviations,-FL, track length; FW, track width. - FL = t2,5 cm; FW = 12.4 cm.

t

True Sl of T8 = (12.5 x 12.4)0.5 = 12.45 cm. f True Sl of TB = (12.5 x 12.4)0.5 = 12.45 cm. 5 True Sl of T8 = (12.5 x 12.4)0.5 = 12.45 cm.

t

J. )z+

The index of footprint size for the MZD fL (SI.1) shou,ed a percentage variation from the irr.re foot length of ITi.Z%-fi1.I7o, conparcdwith 76%197.6% variation in FL. The index of footprint size for the minirrr-rm MZD FL (SL2) shou,ed a percentage variation from the tnre foot length of 10.6%1I4.9%, con-rpared ,xith25.8%-162.9% variation in FL. However, the revised inethod for index of footprint size SL3, usir-rg the i,'alues for SI.l and SI.2, gave a percentage variation of only 64.8%-179.8% compared u'ith the tnre foot iength. The application of the index of footprint size (Tliulborr-r and Wade l9B4) to tl-re data from this studv suggests that it provicles an estimate for the percentage variation in track size in a sequence oftracks. Ifthe tracku'al'is a series of transmitted track features, u,ith tracks represented by the maximum size of the MZD, the /z generated u,ill be too high and the speed calculated fron-r the tracku'ai' too loll'. Hon ever, if the tracks are from a horizon that represents the minimum developrnent of the NIZD, it is possible that h u'ill be underestimated, and the speed calcr-rlaied ivould be too high. Bv cornbining the laboratorv-simr,rlated track data from SI.l and SI.2 to calculate SI.l (Table 12.5), a closer estin'rate of the track size can be made, allorving nearer estimates of /r. The FL generated using SLI (Table 12.5) gave an average of 18.6 cm, and for SI.2, tl-re average FL u,as 9.8 cn; horver.'er, SI.3 ga\re an average FL of ll.Z7 cm, the closest to the true SI FL (12.45 crn). The index of footprint size (SI) is onlv acclrrate if the tracks fron-r u,hich the rneasurements are taken closelv resernbie in size and proportion the original track rnaker's foot size parameters. Hou'ever, bv using the revised iechnique of SL3 (Table 12.i), it mav be possible to estirnate h frorn transrnitted tracks and sr:bseqr,rentlv calcr-rlate the speed from a trackr"'ay more accurately. The speed at r,vhich a dinosaur u'as traveling is an inportant variabie to assess ifthe potential ofthe 3D preservation oftracks is to be fully'utriized. The speed at nhich an anirnai travels directli" affects the tin-re a foot

226

Phillip

L Manning

remains on the grollnd (dr-rty factor) and the intensiil'and distribution of the load transrnitted in that gil,en time. 'l'hulborn (1990) suggested it u'as irrpossibie to calculate the duty factor for a dinosaur directly from its trackwa1'; hou,ever, a 3D approach to track subsurface cleformation cor-rld possiblv alter tl-ris. The anterior displacement of track features 'uvith increasing depth (F ig. 12.1 1) is a result of the phvsical properties of sedinent and the

dvnanic load encour-itered during track formation. The distribution of presslrre (load) over the sole of a foot correlates with the resultant subsurface track relief. If the track and associated features allow an estin-rate of

the cor-rditions prevailing at the tirne of track forn-ration, the subsurface deforn'iation could be coupled r,r'ith the calculated speed of a trackwar,- to enable an estimate of the dutv factor. 'l'he subsurface relief (contours) of the fossil track could provide a means to reconstruct the dynamic pressure distribution or,er the sole of a dinosaur's foot. This, coupled n ith a knor,vn speed, might provide insight into the amount of tine a dinosar:r's foot remainecl on the qronnd (dutv factor) dr-rring locon'rotion.

It

is clear that the use of

FL in calcr-rlations of speed frorn

a trackrva,v (Al-

Summary

erander 1976) should account for transmitted track features because ihey' can potei'rtiallv r,an'speed estimates bv I0-fold. The use of dinosaur tracks in corlparative mtrltivariate studies should be restricted to surface track features for comparisor-r ',vith otl'rer surface track features. f'he inclusion of transrnitted tracks in such studies invaliclates anv taxorrorric or osteological reiationships inferred as a result of the ciisparitv beti'"'een surface and subsurface track rnorphologi. Anv multivariate studv based on n'rorphological variabilitv in tracks and tracku'ay,s can onh'be viable if the lD variabilitv

of track rnorphologv is ur-iderstoocl. Iir:ture multivariate studies must approach the task of ur-rderstanding the 3D cornponents of a track before valid comparison can be n-rade u,ith other tracks li'itl-rin a JD franervork.

This chapter has opened a possible ichnotaxonornic can of rvorms. The shifting sands of time har.e disguised so rnuch of the process of track formation and preseru'ation tliat potentiallv verv little of a track rnakers foot norphologv might be faithfuliv locked in stone (Mar-rning 2004). Vertebrate ichr-rotaxa shor,rld reflect the n'iorphological differences resulting from behal'ior, not the affiniil,of an alleged track rnaker or artifacts of track forrnation and presenation (Nlanning 2004). What is clear is that the interpretation of fossil tracks requires the application of more robust quantitatir,e methodologies. I hope tl-iat if an illusive tracku'av of a trotting or rlrnning 7. rer is for-rnd in the future, its documentation and interpretation will r-rot fall into the potential traps disci-rssed in this chapter. Who knorvs-the ichnospecies could even be narred after a haclrosaur!

I thank Peter f,arson, Neal Larson, and Bob Farrar of tl-re Black Hills Institute of Ceologic Research (BHIGR) for organizing the 100 Years ofTyrantlosdltLls rex Si'rriposiurn in Hill Citv (2005). l'he BHIGR personnel u'ere perfect hosts and providecl access to their rionderfirl collections. A speciai T. rex Speed

Irap

Acknowledgments

227

thanks to Chris Ott, rvho

the instigator of tlie il{-role rex s'n'rrpositrm. Many thanks to Whitel' Hagadorn (Anrherst Coilege) for access to the Hitchcock fossil track collection (Pratt N{useun-r). Also rnanv t}ianks to ri,'as

Amherst College for their generous grant from the General Eastn-ian Fr-rnd to assist in mv research trip to the Pratt N{useum. I thank the Unir,'ersitv of Sheffield for a Hor-ne/EC Bursari'that made the research possible, and aiso N4ike Romano ancl Nlartin Whr,te. N'lan-v tfranks to Ernma Schachner for permissior-r to use the line drau.'ing of T. rex and to Richard Hartlel'for redrar,i'ing Figure 12.11. Thanks to Emma Finch for squeezing and rnanipulatir-rg data into Petrel. N4anr,'thanks to rn1 n'ife ancl clzrr-rghters, r.i'ho perrnit me the tin're to undertake this research. F inalli', a special thanks to N4arion Zenker (BHIGR), rvho kept chasing this chapter and finallr'fotrnd a strategic place to insert a rocket for rne to get it finished.

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-.

T. rex Speed Irap

231

ATLAS OF THE SKULL BONES OF TYRANNOSAURUS REX

13

Peter Larson

Tyrannosaurus rex was described bi,'Osborn in a series of papers at the beginning of the last century,(1905, 1906, 1912, 1916). His rvork r,"'as prirnarily based or-i 3 specirnens: the holotvpe (AN,{NH 973, nor,v CN4 9379), the holotl'pe for Dlnantosaurus (AN{NH 5866, norv BMNH R7994), rvhich u'as

Introduction

svrronl'mized ivith ?l rex in 1906, and AN'INH 5027, which provided mr,rch of tl-re description of the skull. Interestir-rg1r,, the designation of AMNH 5027 has recentlv come under scrutinl,; it nav actualll,'represent a second, unnarnecl species ofTyrannosaurus (P. Larson this volume). Molnar's (1991) treatise on the skull added greath'to Osborn's earlier descriptive work, and it also contained a section on arthrologl'. Nlolnar studied LACNI 23844, AMNH 5027, NIOR 008, and SDS\,I 12047.|n 1998 and in this volume, Molnar increased our understanding of skull rnechanics and musculature. This u'as follou'ed by Brochu's (2003) description of FMNH PRZOBl, including computed iomographv of the articulated skull, presented significant ner'v data and interpretations. Severai other inportant contributions to the skull of tyrannosaurids include Carr (1999) on craniofacial ontogenv, Cr-irrie (2003) on cranial anatorry of tvrannosaurid dinosaurs (particularlv Corgosaurus and Daspletosaurus), Currie et al. (2001) on skull structure, Hurrrm ancl Sabath (2003) on a comparison of Tarbosaurus and Tyrannosdurus, Carr and Williarrson (2004) on tr,'rannosaurid diversitv, and Carr et al. (2005) on a description of a new tyrannosar,rrid frorn Alaban-ra. Althor-rgh several new'fl,rannuaurus rex skulls are no\\r avaiiable for study', bv far the most significant is the disarticulated, undistorted skull of BHI l0l3 (see N. L. Larsorr tl-ris volume). For the first tirne, the individuals bones of the sktrll car-r be described and illustrate d for TyrannoEduruE rex. Tl-ris specimen n'as discnssed bl Hururri ancl Sabath (2003) in their comparison of TyrannosauruE rex and Tarbosaurus bataar. Smith (2005) also utilized BHI l0l3 in his n'ork describing the heterodont dentitior-i of7. rex. This sr,rbject r,r,as also discussed in some detail in Osborn (1916), N{olnar (1991), and Brochu (2003). P Larson (this volume) has utilized this specrrren in iris discr:ssion of an avianlike kinetic palate in T. rex. Here, I present the first ir-r-clepth supplemental description of the skull bones and illustrate them in rnultiple vier.vs in the supplemental CD-ROM, basecl prin-rarilv on Bl{l 1013, n'ith observations of other specir-r'rens.

Pren-raxillae:'fhe prerliaxillae of BHI 3033 are tvpical for Tyrannosauridae and for Trrannosat-LrtLs rer, bearing 4 alveoli. Details r-iot discrissed by OsAtlas

of the Skull

Bones

Dermal Skull Bones

233

born (1905, 1906, 19t2), \4olnar (1991), Broclru (200i), auci Hurum and Sabath (2001), br-rt r,isible ili BHI 3033, include a scallope d region of riclges on the articular surface shared b1'the iiglit and left prernaxillae. This scalloped region is centrallr'located dorsoverttralh'and is at the anterior border of the sutr-rre. Although nearll B0% of tl-ris strture is snooth, ligarnents attached to the scallopecl area cor-rld have restricted lateral movement along

this surface, in effect bonding the 2 prerraxillae into a single strttctural unit. Belor.v this scalloped area, the prenarillac separate, leaving a cleft in the articulation.'l'he significance of this cleft is unclcar, and it is not seen in the articulated FN,{NH PR20El (Brochr-r 20031, a robttst norphoti'pe (P Larson this voltin-re). The right premaxilla shon's erosiot't sttrrounding tl-re anterior portion of the fourth alveolus. This erosion is associated lr"ith tl-re deposition of spong)'bone. Osteomvelitis is the probable cattse of this pathologv. The palatal surfaces of the pren-raxillae:rlso bear a featurc analogous to the interdental platcs Osborn 1912) of the n'raxillae:rncl dentaries. Tliese rnterdentai plates are found at t1-re junctions of the alr'eoli. Ther are clepressed frorn tl're palatal surface of the prer-naxillae and separated frorn one another at the base br'large nutrient foramina. The articular srtrface of the prernaxillarrnr:rxillart'suture is srnooth, interrupted (in the ccnter of tl-ie lateral aspect) or-r11'bt the opening for the sr:bnarialis foramen (Carr 1999; Brochri 2003), r'r'hose borcier is shared b1' the 2 elements. 'l'l-re premaxillarv-rtasal articr,rlation is also quite srrooth, allorving dorsoi'entral rnol,ernent ri'hile rcstricting anteroposterior nloven-rent. It is probable that the pren-raxillae ttnit u'as at least passivelv kinetrc, r-r-rovable relative to the n-raxillae and nasals, providing shock-absorbing benefits for the premaxillar-v teeth. N,IAXILLAE: The rnaxillae of BHI 30ll bear 11 ah'eoli. This nunber is slrared with N{OR 980, althougl-i to d:rte, all other TNrannosaurus re.x specimens have 12 (P Larson this l'olume). The 2 maxillae of BHI 303J articulate near the front of the palate in a series of overlapping ridges rtot mer-rtioned br'' N{olnar (199i) or Brochr-r (2001). This is sirlilar to the conditioninTarbosaurusbataar (Hurum and Sabath 2003). lnTlrannosaurus, the antorbital fossa is a verv deep depression itt even the smallest individuals (i.e., BHI 'fl00 and LACN'I 23'15). 'l'he ventral border of tl-re alitorbital fossa and tl-re antorbital fenestra are coincident along rnr-rch of the ventral borcler of the antorbital fenestra. In most tvrannosaurs, like Gorgosaurus (TCN{ 2001.E9.1; Carr 1999),

Daspletosaurus (K|N'IP 91.16.500; Cttrrie 2007), Appalachiosaurus (RN'{N'I 6670;Cal:. et ai. 2005), ancl Nanohrarzirrrs (CN'INH 75'11, BN{RP 2001.'1.1; Bakker et al. 1988; L,arson in press), the ar-rtorbital fossa is shallorver thar-r T

rex, and a thin ridge of bone (the ventral antorbital naxillar1' ridge) rises along the dorsal rnargin of the postero'n'entral extension of the rnaxilla. It extends well past the last alveoltrs ancl passes under the jtrgal nhere it articulates to tl-re maxilla. In Gorgosaurus, Daspletosaunts, Appalachiosaurus, and Nanotl,ranrLus, the ventral borcler of the antorbital fenestra ancl the antorbital fossa are not coincident. The cor-rstriction at the base of the ','erltral antorbital

234

Peter Larson

naxillary ridge forn-rs the r,entrai border of the antorbital fossa, and the iop of the ridge is tl-re','entral border of the antorbital fenestra (Larsor.r in press) The n-raxillarv fenestra (the second antorbital fenesira of Osborn 1912) in Tyrannosaurus BHI 3033) and Tarbosaunts (Hururn and Sabath 2003) contacts the anterior and posterior border of the antorbital fossa. An additional opening betr.veen the maxillarv and antorbital fenestrae is found on both nraxiilae of BHI 3013, but is not seen in other specimens ofT. rex. A sirnilar openir-rg is seen in a Tarbosaurus specimert, ZPAL MgD-l/4, described by Hurun ancl Sabath (2001). This opening mav be the result of predepositional rveathering and breakage of an extremelv ihin area of bone. A iong, narro\r', and deep abrasion is ir-rcised into the lateral aspect of the left maxilla. This gouge is oriented dorsoventrally and is directlv above the third rraxillarl' tootl-r near the center of the mass of the maxilla. The abrasion ireasrires 12 cm lor-rg by 2 crr u'ide and is approximately I cnr deep at the center of the scar. There is evidence of neq,,bone grorvth, especiall1' near the ventrai end of the gouge, demonstrating that this rnark lvas made some days or rveeks before death. Several perforations rnar the anterior palatal shelf of the right rnaxilla. It could be that these are a result of postmortem rveathering or a fur-rgal infection. They do not seem to har,'e been cai-rsed by osteornl'elitis becar-rse

cancellous bone is not evident. The nasal-maxillarv suture is highlv scalloped on BHI 10J3. Interlocking fingers of bone prevent anv anterioposterior movement along this articulatior-r. l'here is, horvever, the possibilitv of lateral moven'ient, rvith tl-re nasal-maxillarv suture acting as a hinge, allor.ving the ventral portion of the maxilla to srving outu,ard. If such rnovement u'ere to occur, the interlockir-rg ridges of the rraxilla-rnaxilla palatal contact n'ould l-rave spread apart. Srich kinetic rnovemer-it rvould enhance the shock-absorbing abilities of the maxillae and teeth. Movement is also possible at the jugal-maxillary suture. Here the bones are joined b1,a tor-rgue (jugal) and groove (rnaxilla) joint. This loint allolvs anterioposterior slippage. LACHRvMALS: One of tl-ie characters uniting Tltrannosaurus ivith Tarbosaurus, but separating it frorr other tvrannosaurs, such as Daspletosaurus, CorgosatLrus, and Albertosdurus, is the abser-rce of a corneal process on the lachn'mal (Carr 1999; Carr ancl Williarnson 2004). Tl-ris character also separates Tyrannosaurus fronr Nanotyrannus (Larson in press). An additional character is the shape of the lachrymal: it is an inverted L shape ir-r Tyrarutosaurus, as it is inTarbosaurus, and T shaped irt Albertosar_rrus, ()orgosourusl Daspletosaurus (Carr et al. 2005), and Nanotyrannus (Larson in press).

In addition to the pneurnatic "lateral forarnen" mentionecl by Molnar BHI 3033 possess I additional pneumatic openings. The first of these pneumatopores lies anterior to the lateral foramen, near the froni of the lachrr.n-ral. It is on the dorsal rnargin of the antorbital fenestra and opens 'n'entrally. In n-redial l ieri', the lachrvrrals of BHI 1033 (1991), the lachn'mals of

expose 2 more pneun'ratic foramina. The rnedial lachrvmal pneumatopore (Larson in press) opens anterior to and at the dorsal rnargin of a thin ridge

Atlas of the Skull Bones

235

that descencls cliagonallv across the vertical ramus. This ridge terninates at the r,entral, anterior border of the vertical ratrus. fiinalli', a fourth pneumatopore (also nedial) mal' be found at the front of the horizontal ramus.

This pr-ieumatopore opens anteriorh'. The lachn'mals bareh'touch the ascending rarnus of the maxil1a, thus allou'ing rrovernent. Hot evet, the nasallachrl,mal articulation locks quite firmlv, rvith a somen'hat scallopecl surface on the meclial aspect of the horrzontal ranus of the lachrvrnal and a cleft on the lateral aspect of the horrzontal ranr-rs that receives tl're lachrl,rnal process of tire nasal (Hururn and Sabath 2003). The posterior srtrface at the junction of the liorizontal and i'ertical rami is sornervhat ball shaped. This ball inserts into a socket in the anterior sr-rrfacc of tlie frontals, strggestir-ig possible prokinesis, or lifting of the n'rtrzzle (Larsor-r and Donnan 2002). NASALS: As is the case n,ith all tvrannosar-rricls, the nasals of BHI l0l3 are fusecl. This fr-rsion, as lr'ell as latcral arching ar-icl the consistent thickness of the bone (2 clr.r or rrore over nearl)'ttre entire length of the nasals), provides an extremeh' strong structure for the dissemination of stress dei,'eloped dtrring feeding (see Ra1'field 2004). 'fhe nasal-frontal suture is a tongue (frontal) and groove (nasal) joint that allon's fore-ancl-aft uovement and nould

r.rot precl-rde prokinesis. posroRBI't-ALs: The niedial aspects of the postorbitals shou'a sl-rallorv centrai depression, or fossa. Other TtranrTosdurus specimens (BHI 't812, N,IOR 55t, ancl N4OR 9E0) also shou,tl-ris feature. N'Iuch deeper fossae are seen in Corgosaunts (TCNI2001.89.1), Daspletosaurus (Currie 2003), and

NanotNrarutus (Larson in press). 'lil'o paired, isolated osteodenns r'r'ere found associated n'ith the skull of BHI 3033 (Larson et al. I99B). T'hese derrnal elernents are analogous to the "postorbital rugositr'" noted as fusecl to the postorbitals of some robust Trrannosaurus specimens bv N,{olnar (1991), Larson (1994), and Brochu (2003). T),rannosaurus specimens n'ith fused postorbital rugosities include

N{OR 008,

BHI

F\'INH PR208l, BHI4182, and UWGNI

181

(NS 1565.26). On

3031, these loose postorbital nrgosities articulate rvith the postorbitals

on the lateral surface directlv aboi'e the orbit. The anterior snrface of the postorbitals (above the orbit) and the posierior surface of the horizclntal ramus of the lachryn'ials articr-rlate rvith p1'ramiclalll,shaped osteodemrs, or horns. T'hese l-rorns rvere fottnd as isolated elenents in BHI 3031. Thev u'ere noted bv Brochu (2003) as fused to the postorbitals in FN{NH PR2081 and u'ere thouglrt to be part of the postorbital rugositl' of N'lolnar (1991). It is clear from BHI 3033 (a set of isolated horns

found u'ith \'lOR 1125) that the','are independent dermal elements. These horns bridge the gap beti.veer-i the postorbital and tl-re 1ac1'rn'rr-ral. The postorbital-frontal sutr-rre is interfingered and allon's no movement. 'l'he joint betrveen the postorbital and the jugal is srnooth and plarvas also

nar, allovn'ing ciiagonal slippage. The postorbital-sqttan'iosal joint is ar-r expancling tongue ancl groove, rvhich allorl s fore-and-aft separation, altlior-rgh kinesis at this point is difficult to reconstruct. sQUANlosALS: The celitral portions of the anterior aspect of the sqr.ramosals are perforated bt' a large pneurnatopore (most clearl1'seen in BHI

236

Peter Larson

4100). This pneurnatopore is also present inTarbosaurus (Hururn and Sabath 2003), but it is absent inCorgosaurtLs,Nanottrannus (Larson in press), ancl Daspletoscurus (Currie 2003). f ust anterior of center, the lateral ventral borders of the V-shaped squarnosais are marked b,v a deep fold. This fold corresponcls to a cleep concavitr,on the sqtramosal process noted b1,'Molnar

(1991) on ihe qr-radratolugal.'l'hese 2 surfaces cotrld have been the origrn and insertion for a liganent connecting the 2 elen-rents (see Quadrato;r-rgals, belorl.). The articulation of ilie squarnosal rvith the exoccipital is fair\' flat and rnav have allou'ed lirnited sliding rnotion. The squamosal-quadrate joint is ivell cleveloped and is a double ball-in-socket (quadrate-in-sqlrarnosal) joint. The 2 balls are side b1'side ancl are connectecl bv a saddle that is reversed in tlie scluamosal. This joint gii,es great flexibilitv fore and aft, but

lirrits lllcral JUGALS:

rrroi'errrerrt

Both jugals have pathological, healed puncture rvour-rds (Lar-

son 2001). These may har,e been the result of face-biting behavior described bi"Ianke and Currie (1998). The injurl'to the left jugal is a circr-rlar hole, 1.5

crl

b1'2.5 crr, that penetrates at a point near thc origin of the cleft that receives the quadratojugal (here the jugal is approximatelv 4 crn thick). h-i me-

dial aspect, the perforation emerges, leavir-rg an opening 2.7 cm by I.5 crn. The injuri'to the right jrigal is locatecl just anterior of center of the ascending ramus, at the ventral terrliination of the postorbital-jugal joint. 'fhe lateral oper-ring measllres 2 crn br'2.5 cm. The medial exit is larger (3.5 cm bv 6.5 cm) and somer,r'hat triangular in sl-rape. N{oh'rar (1991) shorved that there is pnenmatic sinus in this area (also seen in BHI 3033) that separaies the lateral la1'er frorn the rnedial laver of bone. The larger exit hole mav be explained b1' tl-re thinness of that medial laver. Tl-re jugal-ectoptervgoid joint is snrooth, allon'ing palatal kinesis (see Larsson this volun're). The articr,rlation of tl-re lugal and the quadratojtrgal is also smooth, rriarkecl b1'the cleft mentioned above. A horizontal ridge on the laterai aspect ofthe jugal process ofthe quadratojugal fits into this cleft. Fore-ancl-aft movement of the qr-radratojr-rgal along this foint, with tire firn-rlr':rttached qr-radrate (see belorv) rockir-rg on the double ball-and-socket sqr,ramosal-quadrate joini described abol'e, lr,ould prodr-rce streptostvly. euADRAroJUGarS: '['he left quadratojugal is isolated, and the right one is firn'ilr' attached to the quadrate. Although Molnar (1991, p. 161) presurned that "no articulation n'ith the squamosal existed," there might have been a ligamental attachment (see Squamosals, above) that joined the 2 elernents. This ligamerrt could have acted as a tensile spring, returning tl-re quadrate-cpadratojugal to rest position after a streptostl4ic extension. Tlie quadratojr-rgal-quadrate articulation is somen'hat edentate, creating a nonmovable 1oint. This sr,rtnre also accor-rnts for the firm attachn'rent of the right quaclratojugal to the right quadrate in BHI 303J and other disarticuiated skulls (i.e., N4OR ll25). QUADRATES: The quaclrates of BHI 30ll are both preserved u,ith a small notch (l cm in diameter') on the dorsal eclge of the squarnosal process. This notch lies just anierior to the articulation n ith the quadrate. The notch probablv corresponds to a much larger notch (several centimeters in

A|ES 0l tne >Kuil

Bones

^23/

dianreter) for-rnd in Corgosaurus, Nanoh'rannus (Larson in press), Albertosdurus, and Daspletosaurus (Currie 2003).

The quadrate-pterygoid joint sr,rrfaces are smooth, allou'ing streptostyiy (hinted at bv Molnar 1991).The proximal end has a double articular surface (see Squamosals, above). This is sirnilar to the situation in Gorgosaurus (TCM 2001. 89. 1) and D aspletoscturus (Currie 2003), wherea s AlbertosaunLs (BHI 6214) and Nanotyrannus have only a single ball-in-socket articr-rlation. Although all t1'rannosaurs exhibit the capacitl'for streptostl'ly, it seems that it u.'as accoinplished in different rva,vs. The double condl'lar surface of the qr-radrates at the qtradrate-articular joint is oriented in such a \\'a)' that it forrns a kind of screr.v on the surface of the main joint for the opening and closing of the jarvs. As the jaws opened, this screw'lvould, in effect, widen the gape of the jaws by forcing the articulars awav frorn each other. Likewise, this screw r.vould bring the rear ofthe jaws back together again as the jau's closed (N{olnar l99l).

Palatal Complex

PTERycolDS: Both pterl'goids are complete.'l'he articulation u'ith the quadrate is discussed abol'e. The rear of the paiatal plate wraps over the basisphenoid, limiting posterior movement. Although the dorsal sr-rrface of the palatal plate of the ptervgoid is fairly smootl-r, little rnovement probably

occurred at the ecioptervgoid-ptervgoid joint, and the folding of ti-re quadrate process of the pter,vgoid blocked the ectopterygoid from movir-rg posteriorh' relative to the pter,vgoid. The folded posterior pterygoid-palatine foint allowed fore-and-aft novement but restricted lateral rnovernent. The snooth anterior pter;,goid-palatine joints allor,v fore-and-aft rnovement. The vomerine process of the ptervgoid is a smooth vertical blade that touches the palatine or-r its lateral surface ar-rd the \,'orrler on its medial surface The ptervgoid-vomer suture is bounded bv lateral extensior-rs of the bifurcate stern. These l-cm-deep lips lirnit foru'ard movement of the ptervgoid relative to the vomer. See Larsson (this volume) for a discussion of palatal kinesis. EPIPT'ERYGoIos: The epipiervgoids artictrlate on the anterior surface of the vertical quadrate process of the pierygoids. The epipter,vgoids of BHI )077 are similar to those described for Daspletosaurus (Cvrie 2003). The angle of the inverted V in BHI 3033 is, hou'ever, slightll'greater than that of Dasplatosaurus, and the concavity at the base, mentioned bv Currie (2001), is rnuch deeper inTyrannosaurus rex to such an extent that the 2 arms of the V are actuallv bifurcatecl. The nore rnedial n ing of the epipterygoid butts against the anterior nredial edge ofthe qtiadrate process of ihe pterygoid, continuing the curr,e, established bv the n'redial edge of the quadrate process. This butt joint restricts movement (other than folding) at the epipterygoicl-ptervgoid 1oint. Tfre rnore dorsal epipterl'goidlaterosphenoid articr,rlations are srnooth and i,vould allow rroven-rent dr-rring pala-

ial kinesis.

EcroprERycorls: The hook-shaped ectoptervgoicls of BHI J0Jl are perforated r.vith a large pneumatopore tvpical of theropods (NIoinar l99l). Carr et al. (2005) noted that the thick lip that bounds the pnetrn'ratopore 238

Peter Larson

linb of the ectoptervgoid contacts the ver-rtral rredial surface near the center of the jugal. The sr-nooth ectopterygoid-1ugal joint is critical for palatal kinesis (see Larsson this',,olume). pALAT'INES: The palatine u'as incompletelv described b1'Nlolnar (1991). Although both palatir-res are cornplete in BHI 3033, they u,ere someu,hat rveathered before burial, rnakir-rg a cornplete assessment difficult. BHI 4100, hor.vever, does ir-rclude an exceptionallv rvell-preserr.ed right palatine that aicls in the interpretation of BHI 3033. This palatine has a large pneumatopore on the central lateral sr-rrface near the articulation with the maxilla, which opens into a vast chamber. There is also a cleep pneumatic fossa directlv anterior to this pneurnatopore and of near-equal size. The palatines of Tyrannosaurus are much rnore inflated than those of Daspletosaurus (Cr-rrrie 2003; Carr etal. 2005),Albertosaurus (Carr etal. 2005),Gorgoscurus (TCN,I 2001.89.1),:rnd Nanoflrcnnus (BN'IRP 2002.4.I). However, their sinrilarity to Tarbosaurus (Hururr-i and Sabath 2003) coulcl ir-rdicate that this inflaiion is a was a character for Tyrannos(7urus. The anterior

fur-rction of size

.

'l'he palatine-maxilla joint

is slightlv grooved, with corresponding low tongues on tl-re opposing bones. This joint u'ould allow limited rrovernent fore ancl aft and would not preclude lateral rnoven-rent of the rnaxillae. The

palatines aiso contact the anterior rnedial surface of the lugals and the ventral rredial surface of the lachrl'rnals in a smooth joint that u'ould not restrict palatal kinesis or lateral nol'ernent. voNIER: 'l'he vorner of BHI lOJ3 rnatches Nlolnar's (1991) reconstructed description. The anterior rhomboid plate ir-r BHI 1033 is convex in dorsal aspect and concave ventrallr'. This rhomboid plate also sports a srnall healed puncture rvonnd near the base (Larson and Donnan 2002).

BHI j033 has a relativeli'con-rplete braincase that is n-rissing onl1,'the ventral portion of tl-re basicraniurn (as a result of predepositional weathering). As in FMNH PR20BI, the prefrontals are firmly affixed to the frontals (Brochu 2003). The subadr-rlt N'{OR1125 has loose prefrontals, and a mature individual of T. rex A (see N. L. Larson this l'olurne) preserves both frontals as disarticulated elernents. A l-realed puncture wound is located near the center of the supraoccipital crest of the left parietal. This 3-cm-diarneter hole perforates rvhat il'as originally 3 crl of dense bone. Imn-rediately above the perforation, a I2 cn bv 5 cr-n fragmer-rt of bone is rnissing fron-r the edge of the supraoccipital crest, presumabiv the result of the sarne incident causiltg the perfora-

Braincase, Including Skull Roof

tion (Larson 2001; Larson and Dor-rnan 2002).

Only the left articular was recovered fronr BHI 30ll; it was tightll, articulated to the left surangular. The articular surface of the ex-

ARTICULAR:

posed right articular-surangular suture shon's a great deal of interfi:rgering,

elininating the possibilitl'of rnoveruent at this suttrre. l,ikeu'ise, the nature of the articnlation lvith the prearticulars reveals that the articr-riar rvas firmly'locked into position in life. Atlas of the Skull Bones

Mandibles

PREARTICULAns: The prearticulars

mm in lateral

clin-rer-rsior-r

thin anteriorlv to approxin-ratelv

2

for the fir-ral thircl of their length. although thev

measllre an average of 8 cm in n,idth. Botlr of the prearticulars shon'srnail (several millirneters), possibli pathologic perforations near their anterior

terminations. ANGULARS: The angtrlars of

BHI

30J3 niatch N'loh'rar's (1991) descrip-

tion. The left angular shou's some minor remodelir-rg or-r the anterior most surface, correspor-rding to a puncturc r,r,ound (u'l-rere it articulates) on the left surangular. The spatulate posterior nediai surface articulates ri'ith the surangr,rlar dorsalll' and the prearticular ventralli'. Anteriorlv, the anguiar thins dorsoventrally and is sandri,'iched betri,een the dentar-v (laterallr') and the splenial (r'nedialh). A11 these surfaces are smooth and allorv fore-and-aft lnovelTlent. SURANGULARs: Both clarr-shaped surangulars shon' liealecl putrcture rvounds. The right slrrangular has a large, remoclelecl perforation just anterior to and tl're sarne size as the surar-rgular fenestra; a secor-id perforation is on the anterior eclge of this surangrilar. The left surangular is even more pathologic, u'ith 4 large perforations. A11 siron' evidence of healing. Thel' are rounded and thickened at the edges bv rernodeling. This is not unttsnal

forTyannosaurus, and perforations of this large, thin elernent are for,rnd ir nearh'everv preservecl surangular. FN{NH PRZO8l (Larson 2001), LACN'l 23844 (N{olnar 199}), ANINH >027 (Osborn 1916), N'{OR 555 (Horner and Lessern 1993), N,'IOR 008, N{OR 980, BHI 4E12, and BHI 6230 all sport extra perforations, thought to be er,idence of face biting (Tanke and Currie l99B; Larson 2001; Rothschilcl and N'loln:rr this voltrnte). DENTARIES: The dentaries each have l3 ah'eoli. Thev also botl-r exhibit pathologies. The right dentarr has a healed puncture, and a healed puncttrre and tear near the posterior rrargin.'l'here is also a 4.5 cn'r br' 1.5 cm erosior-r located 5 cm belon,the fifth alveolus. This erosion on the right der-rtarl'sl-iolr,s no l-realing or spong)'bonc and nav be er.idence of a fungal infection. The left dentarv sholr's a 4 crr br,' 1 cm abrasion locatecl 5 cm below the lJth alveolus. This abrasion does shou' evidence of nen,bone growth. Tl-re skull of Tyrannosaurus (and otl'rer theropocls) are often reconstructed lr,ith the svrlphr,sis of the lou'er jaris rvideli'separated, sometimes by as mr-rch as 30 cm (i.e., LACN.'I 27844). This seerns to be an attenipt to force the teeth of the lou'er jan,s to occlude n'ith those of the upper. Of corlrse, theropods are not crocodiles, and their teeth did not occltrde in life. Rather, tl-re teeth of the lolr'er jau's pass rnedial to those of the upper jau's as the jar,vs close. Evidence for this is presented bv \{olnar (1991, p. I43), r.vho noted, "The rnedial face of the maxilla bears a number of shailoiv depressions . . assnned to hal'e acconrnrodatcd the tooth cron,ns lof the dentari,'l when the rnor-rth lr'as closeci, as in alligaioroids." Thus, the s1'mph1'sis of the lou'er iarvs r'"'ere joinecl b-v a ligamentous attachmer-rt that allowed onii' limited no','ement for the purpose of absorbing the shock of teeth hitting bone. seLENIALS: Both splenials of BHI J0l3 are presened as separate elements shon'ing the lateral surface n'hich articulates against the dentarr''. A Peter Larson

ridge on the dorsal anterior surface of the splenial fits into and becomes part of the Meckelian groove of Osborrr (1912). This seems to indicate that there is no movement betr.r,een the dentan' and spler-rial. The dorsalrnost portion of the splenial covers the coronoid, jtist posterior to tl're last alveolus of the dentarl,'. CoRoNoIDS: Only the right coronoid nas recovered, but it was prein its entiretv. Molnar (1991, p. 155) accepted Osborn's (1912) interpretation of the coronoid as "a srnall triangular plate laving at tl-re antidorsal angle of the N{eckelian fossa." Horvever, because the coronoid passes belrind the splenial in AN,{NH 5027 (and in other articulated Tyrannosaurus lou'er jarvs), Osborn's interpretation n'as incorrect. The coronoid actuserved

ally cor-rtinues behind the splenial and or.'erlaps the interdental plates of the dentary in rvhat Osbonr (1912) called tl-re supradentary. Currie (2003), noting that the splenial and suprader-itary i.vere joined, and called the entrre structure a "coronoid-sr-rperdentary" in his description of Daspletosaurus. Hurun and Sabath (2003) referred to it as a "superdentarl'/coronoid." Brochu (2003) provides a long discussion about rvhether this elen.rent is a single bone (the coronoid) or 2 separate bones (the coronoid and sr,rpraden, tary) that fused cluring ontogenv. His argument tl-rat no immature tvrannosaur individuals displav these as separate elements seems to indicate thai thrs is a single elernent and there is no supradentarv. Certainlt,rnTyrannosaunrs

(BHI 3013, BHI 4812, N{OR 1125, FMNH PR208l, etc..J, DaspletoEd.urus (Currie 2003), Corgosaurus (TCM 2001.89.1), and Tarbosaurus (ZPAL MgDIi4; Hurum ancl Sabath 2003) the "coronoid-supradentarl/'is a single bone. The same is true for other theropods like Acroccnthosaurus (NCSN,l 14345) and the allosauroid Sinraptor (Cr-rrrie and Zhao 1993, p. 2055) rvhere this elernent is illustrated as a "ceratobranchial." Even irr the prosauropod Plateosaurus it has been interpretecl bl'Galton (1990) as a single element: the coronoid. Likervise, Romer illustrates the medial aspect of the lor,r,er jaw's of Labidosaurus (1956a), Kotlassia, Diadectes, Bradysaurus, Python, Peloneustes, Dimetrodon, andEdaphosduruE (1956b) as all possessing a coronoid ivith a thinning anterior projection that passes over the medial aspect of n-ruch of the tooth rou'-t}'re sane situation seen in theropods. It is for these reasorrs that the "coronoicl-supradentan " shoulcl sirnplv be referred to as the coronoid. The coronoid for BHI 303J closelv resembles tl-rat of Tarbosaurus, d,escribed b1'Hurun and Sabath (200i).

'fhe disarticulatecl

skr-rll olTvrannosaurus

rel speciinen knorvn

as

BHI

30ll

Conclusion

preserves n-ran_v details not seen ir-r other specirnens. A close examinatior-r reveals details of tl-re air sac system that invade or leave its impressions on

uranl'of the bones of the skull. Pathologies-evidence of disease or healed injuries-found on some of the cranial elernents provide insight into behavior, slrch as intraspecific conibat (face biting) ancl the corrmonalitl, qf certain pathogens such as osteoml'elitis. And finallv, the exquisite preser\ration of the crar-iial joint surfaces on BHI 3033 opens the door to a more conplete analvsis of the capacitv for cranial krnesis irtTyrannosaurus rex.

Atlas of the Skull

Bones

241

[,inritecl discr,rssions of some aspects cranial kinesis inT. rex mal be found in Larson and Donnan (2002) and Larssorr (this r.'oiume).

Acknowledgments

I thank Neal Larson for taking the photographs of the indiviclual elements and Larr-v Shaffer for pl-rotographs of the assernbled skull and for tr.rrning them all into illustrations. The hours of labor involvecl in this process are rnan\', and mv talents leave much to be desired. Also l','orthr,of m1'r-rndving gratittrde are m\r colleagues, lvho protided :rccess to all the T. rex specimens involved in this research ar-rd I,r.'ho patientl_v tar-rght rne tyrannosaur osteologr'.

References Cited

Bakker, R. T., Williarrs, \'I., and Currie, P 1988. Nanotyrannus, a ne\v genus of prgrnr tr rarrrrosaur. from the Latest Cretaceous of Nlontana. Hunteria l()): 26.

Brochn, C. A. 2003. Osteologv of Tlrarunsau.rus rer; insights frorn a nearlv cor-nplete skeleton and high-resohrtion corrrputed tomographic analr,sis of the skLrll. /ournal of\/ertebrate Paleontologt Ilemoir 7: i-l18. Carr, 'I'. D. 1999. Craniofacial ontogenv in 'll rannosauridae (Dinosauria, Coelurosarrria). I our nal of Ve r tebrate Pale ontologl, 9( I ) :'f 97-5 20. Carr, T. D., and Williarrson, T. tr. 2004. Diversitv of Late N4aastrichtian Trvrannosauridae (Dir-rosauria: Theropoda) from u,estern North Arnerica. ZoologicaL lotLrnal of the Linneatt Societl, 142: 479-5?'.1. Carr, T. D., Williamson, T. E., and Schu irnnrer, D. R. 200i. A net,genus of tlrannosauricl fror.n the Late Creiaceous (\liddle Campanian) Denropolis Form:rtiorr of Alabarna. loLLrnal of \lertebrate Paleontologt 2;(1): 119-143. Currie, P I. 2003. Clranial anatornl'of t1'rannosaurid dinosaurs fronr the Late Cretaceous of Alberta, Canada. Acta Palaeontologia Polonica48(2): 19l-226. Currie, P J., and Zhao, X. J. 1991. A neu carnosaur (Dinosauria, Theropoda) fron the Jurassic of Xinjran, People s Reprrblic of China. Canadian lournal ofEarth Sciences 30: 2007-2081. Currie, P. |., Humnr, i. H.. ar-rd Sabath, K. 2003. Skull structure and er,olution in tvra nnosaurid d inosaurs. Acta Pal ae ontolo gi a Polonic a 48 (2) : 227 -23 L Galton, P. N'I. 1990. Basal Sauropodonorpha. P.720-144 in Weishampel, D., Dodson, P, ancl Osmlska. H. (eds.). The Dinosauria. Universitl'of 1

California Press, Berkelev. Horner, J. R., ancl l,essen, D. 1993. The Complete

T

rex. Simon

&

Schuster,

Nen'\brk. Hururn, ]. H., and Sabath, K. 2003. Giant theropod dinosaurs from Asia and North Anerica: skulls of Tarbosaurus bataar and'Ij,rannosaurus r?.f, compared. Acla Paleontctlogia Poktnica 48: 2, 161-190. Larsort, N. 1,., Farrar, R. A., and Shaffer, L. 1998. Neu, inforrnation on the osteologv of the skull of Tlranrtos(iurus rex. P. 68-69 in Wolberg, D. L., Sturnp, E., and Rosenberg, C. D. Dinolbst lnternational Proceedings. Acaclenv of Natural Sciences, Philadelphia. Larson P. L. 199'+. Tt,rannosaunLs sex. P ll9*155 in Rosenberg, G. D., ancl \\blberg, D. L. (eds.). Dino F'est. Paleontological Societv Special Publication No. 7. 1001 Paleopathologies in Ti'rarznos(iurL6 rex (in Japanese). DirLo Press 5: 26-35.

-

-. 242

Jn press. T/ra Case for Nanot.r'rannus.

DeKalb.

Peter Larsan

Northern Illinois LJniversitt' Press,

Donlan, K. 2002. Rex Appeal: The Atnazing Stort of Sue, tlrc Dinosaur tlnt Chatryed Scierrce, tlrc Lat, and \,Iy Life. Inr.isible Cities Press, N{ontpelier, \/'l'. Nlolnar, R. E. 1991.'l.he cranial rnorpl-rologv olTt,rannosaurtLs rex. Palaeontographica Abteilutg A 217: 137 -176. Osborn, H. F. 1905. Tt,rannosaurrLs, and other Cretaceorrs c:rnit'orous dinosaurs. Bulletin of the American \,Iuseum of Natural History 2l: 259-266. 1906. Tt,rannosatLrus, tJpper Cretaceous c:rrnivorous dinosaur. Bulletin of the American Museum of Natural History 22:281-296. 191 2 Crania of T1'ra nnosdurus and Allosaurus. N/lentoir of the American Museun of Natural History (n.s.) I: l-30. -. 1q16 Skeletal adaptations ofOntitholestes,Stnihiotnimus,Tlrdnnosaurus. Bulletin of the Anterican l,Iuseunt of Natural Historl' 3): 733-,- t-4. -Ravfield, E. 2004. Cranial rnechanics and feeding in"I'yrannosaurus rex. Pro,. ceedings of tlrc Ro,tal Society of London B 771: 145I-1459. Rorner, A S. 1956a. A Shorter \,lersion of the \lertebrate Bodt. W. B. Saunders, Philaclelphia. 1956b Osteologl, of the Reptiles. LJniversitv of Chicago Press, Chicago. Smith, |. B. 200t. Heterodontl, i:nTt,rannosaurus rer: ir.nplications for the taxo-. nolnic and sr,stenertic utilitr. of theropod dentitions.lournal of Yertebrate L,arson P L., and

Paleorttologt,

2

5

(4): 865-8E7.

Tanke, D. H., and Currie, P. J. 1998. Head-biting behavior ir.r theropod dinosaurs: paleopathological evidence. P. 167-18'l in Pdrez-lu{oreno, B. P, Holtz, T. J., Sanz, J. L., and Nloratalla, J. (eds.). Aspects of Tlrcropod Paleobiology,. Caia: Revista de Ceociencias, NluseuNacional de HistoriaNatural, Lisbon, 15.

Atlas of the Skull

Bones

243

Figure 14.1. Palatal as-

pect of Corvus with palatal bones labeled. Modified from Bock (1964,

fig

2B)

maxilla-palatine palatine

jugal bar pterygoid

quadrate

244

Hans C. E. Larsson

PALATAL KINESIS OF TYRANNOSAURUS REX

14

Hans C. E. Larsson

Cranial kinesis is n'iclespread throughout Gr-rathoston-rata. Although this clade is diagnosed br.'a cranial-mandibular joint, taxa as dil'erse as tiger sharks and tiger bitterns have complex cranial articulations that allow for intracranial kinesis. Onl1' a ferv taxa have con-rpletell' lost cranial kinesis,

lntroduction

such as amphibians, mammais (n'ith the exception of rabbits), turtles, and crocodiles. Crar-rial kinesis has at least 2 mechanical benefits. N1arrv chondricthvans l-rave hvostr.,lic jau's that l-rave a rnobile articulation onlv r,vith a h1'ornandibr-rla, lr'hich in turn l-ras a rnobile articulation rvith the braincase. 'I'hese articulations allow'for jarv protrusion frorr the neurocranium. N4ost osteichthr,an fishes have a sirnilar splanchnocranial kinetic jarv suspension. Hor,vel'er, tlieir dermatocranial bones augment jau,kinesis rvith maxillae that are free from the circumorbital bones and mobile lvith respect to thern and, in neoteleosts, a protrusible premaxilla (\Vestr-reat 2004). These derrnatocranial joints allow'the maxillae and premaxillae to be nanipulated in complex l-din-rensional excursions ar-rcl provide the range of jail' mechanics that reflect tlie high diversit), of teleost fishes. 'l-etrapods, on the other hand, appear to ha'"'e started life on land rl,ith relatir.'elv akinetic skulls. Nlost Paleozoic and all modern arrphibians appear to har.'e little to no cranial kinesis. Svnapsida continued this trend io the fused skuils exhibited b1'n'rodern mamnrals. The akinetic mammalian skull rlav har,'e been the result of providing a solid framervork for por.verfr-rl and complex masticatorl' muscles (revieu'ed in and references founcl rn Carroll l9B8). Presence of complex jarv rnr,rsculature has been cited as one correlate for the er..olution of the complex tooth nrorphologies present in

manmals. Reptiies are generalh' more conservative in tooth rnorphologri Ntlost have sirnple conelike teeth that range frorn straight conical ieeth to sl-rarply recurved, bladelike teeth. Notable exceptions include the manv herbi'"'orous and durophageous taxa.'I'he relativelv sirnple teeth of manv squarliates contrasts rvith sorne of the forms of cranial kinesis that thel' present. Nlost sqr:arrates have a kinetic quadrate that hinges on the undersurface ofthe squanosal. Presence of a mobile qr-radrate is called streptostyil'. A classic studv on varanids illuminated the cornpler motions the quadrate nakes dr-rring jarv opening:rnd closir-rg (Smith 1980). Quadrate rotation is translated into a series of other cranial rnotions that modify the position of the snout and palatal bones. Extreme 'u'ersiorrs of streptostr'lv are present in manv snakes, rvhere each quadrate can rlove independer-rtly of the other, providing a walkirrg

Palatal Kinesis

245

ratchet motion that lielps tractor prel'tonard their esophagus

uith palatal

teeth (Cundall 1983). Modern birds also erhibit streptost,vlic quadrates. Birds use quadrate rotation to provide the forces required to movc their upper jans in a sagittal piane independentlv from tlieir braincase.'l'he uppe r jarv is hinged or-r either nobile joints or over thin bone bridges that can bencl. 'l'he iocation ancl number of these joints varr', but the result is that the upper beak can mo\,e in either complex motions, as in nut-eating parrots, or sl'rock absorption. as in n'oodpeckers (Beecher 1957,1962: Bock 1964).'flie diversitv of beak krnesis in birds is onlr,'beginning to errerge, but research suggests that it is broad (Zr,rsi 1984).

The rnechanical driver for bird beak kinesis is a rotarv quadrate, similar to the streptostvlic condition of nost squamates, and a kinetic palate (Bock 1964). 'l'he pter,vgoicls contact the quacirates and receive parasagittal forces fron the quadrates to slicle the ptert'goid bones along a lnobile joint over an elongate basiptert'goid processes. The ptervgoids contact the palatines, n'hich

in turn contact the vorler to translate this propalinal n-rotion throughout tlre palate, and in turn to the r-naxillae and prerrarillae (Fig. 14.1). T'he palatir-res and vorner have a kineiic contact u'ith the paraspl'renoid. 'l'he distal quadrates also contact thin, elor-rgate jtrgal bars to translate rotational vectors of the quadrates directlt'to the lateral rnargins of the maxillae . The mechanical forces are generatecl and controllecl bv a complex set of ian' and palatal nuscles (Bock 1964).

Paleognathous ancl neognathous palates of nrodern bircls have long been used to diagnose ratites frorn all oil-rer birds, respectivelr' (NlcDon'ell 1948; Bock 196l; Gussekloo ancl Zu'eers 1999). Ratites are characterized bl' having large, robust palatal bones that appe ar nlore simiiar, in sotne respects, to a generalized repiile in n-rorphologl'than the gracile and elongate neognathor,rs palate. N1ajor clifferences betn'een the 2 palate fornis include the presence ofelongate posterolateral processes ofthe palatines to fortn the onlv contact li'ith the pterl'goid bones lateralh'in paleognaths. Neognaths have a n-rore tvpical paiatine-pteri'goid contact in the miclline of the palate. In botl-r forms, the vomer contacts the palatines, but the vomer of paleognaths is rela-

tivelv larger and rrore robust. Because of the osteological differences ancl some in 1'11'6 6f5s11'xlions, rnanv researchers have long suggcsted that paleognathous bircls have ur-rique cranial kinesis that is associatecl ivitl-r tl-reir pala-

tal rnorphologv (Hofer 1954; Simor-retta 1960; Bock 1963). Cussekloo and colleagues (2001) exanined clifferences bet'ni,een paleognathous and neognathous bird cranial kinetic patterns br calcr-rlating displacemer-rts of markecl joints ri,ithin intact bircl heads. Dispiacenents rvere calcr-rlated for a sei of paleognathotrs and neognathons bircls u'itl'r

closed bills and upper bills that ri'ere clorsali,v flered approxinatelv l0' from the horizontal plane. This rilngc \\,as use d to estinate the linkage arrangements r.vithin the norrnai range of upper bill kinesis. The results strggested the kinetic inotions r'i'ithin the entire set of paleo- ar-rd neognathous birds were qualitativelv sirnilar. The marked cliffcrences in palatal rnorphologl' betn'een the 2 avian clacles u'as not associated u'ith anv obr"otts difference in the linkages of bones uithin their skulls during palatal and 246

Hans C. E. Larsson

upper iaw kinesis (()ussekloo et al. 2001). The sirniiar kinetic patterns rvithin paieognathous and neognathes suggest their kinetic skulls evolved from a cornilron ancestor. The cornmon ancestrl' of modern bird crar-rial kinesis has been hvpothesized before, and some have suggested that fossii forms, such as Hesperornis, exhibited rhynchokinetic skulls that mav be ancestral to the diversity of niodern bird cranial kir-resis (Zr.r'eers et al. 1997; Zw.eers and Vanden Berge 1997). 'l'he evolution of the ar,ian kinetic skull frorri nonavian ancestors has never been explored. Part of the reasor-r mav be that adequateh preserr.'ed material is rare, and there are significant challenges to reconstructing biornechanical hvpotheses for fossil taxa. 'fo date, the possibilities of cranial kinesis ir-r dinosaurs have oirlv beer-r explorecl inlguanodon (Norrnan 1984) and iradrosatirs (Cuthbertson 2005). These studies strggested a remarkable mechanisrn of a laterai ercursion of the rnaxillae to efficientlv process tough plant

material. 'l'he imn'iediate ancestrv of birds lies rvithin theropod dinosar-rrs (Gauthier 1986; Sereno 1999). No nonai,'ian theropocl has been lii'potliesized to har,'e sigr-rificant crar-rial kinesis. Hou,ever, N,{olnar (1991) did acknoi,vledge thatTyrarLnosdurus rex mav har.e had lirnited streptost','lr'.

The purpose of this chapter is to explore a hvpothesis that T rex rnav have been capable of crar-rial kinesis, and to exarnine to nhat degree that kinesis rvas similar to the kinesis of birds. Previous lvorkers have suggested that T. rex nav have been capable of limited streptostr'lr' (N{olnar 1991). That streptostvlv is evinced bv the presence of an articular condt,le on the prorirnal end of the quadrate. Hon,er,er, the quadrate is integrated into the lorver temporal and palatal bones and reqi-rires further examination to describe rts possible role in being streptostvlic.

Tlre nrost complete and u'ell-preserved skull ofT. rex is housed in the Black Hills Institute (BHI). BHI l0ll has been given the vernacular title of Stan. The head skeleton is lacking onl,v a right articular, is virtuallr'undistorted, and is completelv disarticulated. N,{ore research casts of tl-ris specimen exrst in the u,orlcl than anv other theropod, u'hich has led Philip Currie to refer to this specimen as the Stan-dard of theropod cranial osteologr' (Currie, personal conrnunication 2005).

Exarnination of the infraterrporal region of BHI 30ll reveals a plausible case to begin modeling streptostvly for the specirnen. T\,rannosaurs and manv other theropods feattrre an arcuate anteroventral process on the quadratojugal (Fig. la 2A). This process articulates laterallv into a sir-nilarl1' arcnate prong and trougl-r on the posterior ramus of the jugal. Although this type of slot loint is commolt in reptile skulls, tl-re arcuate sl-rape of the joint is of particular ir-iterest. 'fhe ;oint is in close proxir-nitv to the qr:adrate. The dorsal head ofthe quadrate features a saddled surface that articulates r'vith tl-re surface of the sqr-rarr-rosal ri'ith probably a sl,novial joint. A "'entral synovial joint bet.,l'een the quadrate ancl squarnosal is present in most squamates, all birds, and e\,en in earlr.stage crocodr'li:rn embrvos (Larsson, rn preparation). 'fhe sin"rilar anatornv found in nonalian dinosaurs suggests Palatal Kinesis

Anatomy of T. rex Palatal Kinesis

quadrate

Figure 14.2. Right lateral aspect of Tyrannosaurus rex (BHl 3033) as reconstructed f ro m d i g i tized casts (A) and a detail of the right infratemporal region (B). Darker circle and radius represents the length of the

quadrate and its distal excursion path. Lighter circle and radius are the same as the darker curves but translated to overla p the a p p roxi mate axis of the anteroventral ramus of the quadratojugal.

quadratojugal

the presence of a sy'novial joint in these taxa during life

as

well. If tlie

quadrate is hypothesized io hal'e at least lirlited streptostvly, then the distal quadrate must s',l,ing with a circular excursior.r 'nl'itl-i a radius equivalent to the ler-rgth of the quadrate. If a circular excursior-t path is cor-rstructed r'vith such a radius and shifted to overlap the quadratojugal-jr-rgal contact, then the circle closelv foilows the arcr,rate path of the prong-and-trough articulation (Fig. 14.28). The congruence beti,l'een the qr-radrate's circular excursion and shape of the quadratojugal-jugal arcr-rate articulation suggests tl-rat if the quadrate u'ere streptostf iic, its motion could be accommodated b1'a n'robile joint r,vith the fugal. N,Ioreover, the articulation betlveen the quadratojugal and squamosal is never fr-rsecl ancl is ir-rsteacl a simple broadly'' overlapping planar joint, The thinness of the quadratojr-rgal in tl-ris regior-r suggests that this articulatior-r ma1'also have been mobile.

The possible

rnobility of the quadratojr-rgal with respect to the scluamosal and jugal effeciively isolates anv streptost\'lic motion of ihe quadrate to onh' the quadratojugal on the external surface ofthe skull. Internally; the quadrate articulates n'ith the pterygoid (Fig. 14.3). The articuiar surfaces betlveen the quaclrate and ptervgoid are broadl-v overlapping with robust grooves and ridges that rvor-rlcl probabll' }'rave been rather in'rmobiie in life.'fhe articulation is further stiffened b1'a modest groove on tire ventrolateral margin of the quadrate flange of the pterl'goid to recerve the ventral edge of the pterygoid flange of the cluaclraie. The ptery'goid articttlates witl-r tl-re braincase on the basipterrgoid processes. These processes are

248

Hans C. E. Larsson

Figure 14.3. Palatal as-

premaxilla

pect of Tyrannosaurus rex (BHl 3033) as reconstructed from d igitized

t1 ,.^.

1

.. _,i

I

casts. Palatal bones are

darkened from remainder of skull.

{ fi i,,.

maxilla

palatine

pterygoid

ectopterygoid

quadrate

basipterygoid process

eliiptical and i.r'or,rld have been capped n'itl-r cartilage. The pterygoids fit over the basipterygoid processes u'ith a rnitt-shaped cotvle that is open posteriorll'. The open end and loose fit of the articulation suggest some anteropostenor mobilit,v that would hal'e been osteologicalll' unlin-riied in the anterior direction. The pterygoids contact the ectopten'goids lateralll'and palatines anterioiaterallr'. Both these articr-rlations appear to be irnn-robile if the force on the contact rvas from a posterior vector. 'l'he ectoptervgoid rests in a saddle on

the lateral surface or-i the pterygoid that rvoulcl have lirnited anv posterior motion of the ectoptervgoid relatir,e to the ptervgoid. The posteron-reclial regior-r of the ectoptervgoid exhibits a robust process that butts into a receivirrg concavitl, near the anterior surface of the basiptervgoid cotyle of the ptervgoicl. There is no evidence of the articr-rlation retair-ring the ectoptervgoid in place should the pterygoid have been displaced posteriorlr'. In fact, tl-re artrcular surface is not rvell defined, suggesting that the ectopter_vgoid rnal'have had son.re degree of mobilitli perhaps swinging between somervhat dorsolateral to ventrolateral positions r.vhile remaining in contact r.vith the pterl'goid mediallri Laterally; the ectoptervgoids contact the rnedial surface of the jugals. 'I'his contact is does not exhibit any scarring on the jr-rgal and suggests

the capacity of some sliding motion betu'een the 2 bones. The palatines contact the ptervgoids in a blind-ended prong in groove foint. The contact provides a buttress from uhich the pter,vgoid n'ray hal'e pushed tl-re palatine :rnteriorlri Hou,'ever, like the ectopter,vgoid, there are Palatal Kinesis

249

appears to be

little osteologv keeping the palatinc in this tight articulation

shor-rld the pten goicl be clisplacccl poste riorl1. Anteriorh , the palatines contact the rnarillae in an approxin:rtell, 30o:rngle posterolateral to the sagittal plane (fig. 14 3) This contact is composed of broad striate riclges that extencl the length of the contact anci are parallel to one another. The delta-shapecl profile of the anterior rrargirr of both piil:rtines nedges against the maxillae. 'l'he vomer contacts thc antcrior ramus of the pterl,goids ri'ithin a tall

peg-in-socket joint. Tl're contact is sagittallv elongate, n ith the cor-icave pocket on the vonrer rcceir,ing the anteriorh'convex :rnterior rar-nus of il-re pterl'goid. Thc contact appears braced to har,e received anteriorlv directecl forces from the pterr,goids to mor,e the vorner anteriorlr,. Houer,er, like the other palaial contacts, the ptervgoid-\'onrer contact cloes not appear kr have a joint n,itli rluch strcngth to pull the r.oner posteriorlr'.

Tlre palatal bones of T. rex <1o not appear to bc rigidlr, corrnected to anr.' other bor-re in tl-re skull, n'ith the exception of the quadrates. The relative

Discussion

isolation suggests some kinesis ma'n'have been possible. Palatal kinesis appears to ha','e been limited in a horizontal plane and in a sagittal vector. On the basis of osteological anatorn\', anterior notion seems plausible. The ptervgoicl-basiptengoicl process articulation appears to havc been capable of propalinal motion. Tl-re ectopteri goid-ltrgal contact shorvs no inclication of sutures and suggests a dl'nanic articulation. The palatine-maxilla contact is delta shaped, and the surfaces contact along longitr-rdinal striae that do not seem to har.'e hindered a sliding motion. 'I'he vorner underlaps the palatal shelves of the rnaxillae r.r ithout sutnres or anr, other morphologr. that n'ould suggest irnn-robilitr'. Posterior triotion n'ould be necess:lr\,, of course, to return the palate to its posterior position. 'I'his rrotion does not have strong bone signatures and buttressing. Hon'ever, if less force n,as inflicted on the palatal joints,

thel' nav have remainecl in contact lr,ith the aid of ligan-rent attachments. If the quadrate u,as incleed capable of even limited streptost1l1,, then the anteroposterior excursion of the clistal quadrate appears to be accornrnodated bl. relativeh, loose-fitting quadratojugal-sqr-ran-rosal-jugal contacts and a palate that appcars to be capable of propalinal kinesis. All niodenl birds have streptostr'lic cluadrates that drir,e a palate n,ith propalir-ral kinesis.

Although birds lack an ectoptervgoid and hal,e significar-rtli,different skeletal anatomies of the ptervgoid, palatine, and voner, their palaial kinesis appears sinilar to the kinesis lrvpothesized for T. rex. Although this studv is irr no lva1,a test of palatal kir-resis in'1. rex, it does dernonstrate tl-iat the osteological anatomv of the quadrate and palate appears to have been capable of accommodating a kinetic palate sliding ir-r a propalinal vector. Further rvork is under r.r'a'n' to cxan-rine tliis rnodel u'ith l-dir-r-rensional kinematic rrodels to detemrine nhat effects a kinetic palate mav l-rar,e in the skull (Larsson and Larson, in preparation). The snor.tt probabiy' did not rno,"'e in a sagittal plane, as in birds, but perhaps other kinetics resultecl. The possibiliti'of palatal kinesis inT. rex has significant evolutionarv irnplications. Should at least son-ie of the kinenratic functions be homologons 250

Hans C. E. Larsson

(i.e., fotrnd to be present in the comrnon ancestral lineage) betu'een T rex kinetic bircl palate t'ill have had a lengthr,historv of origin. Such a deep histon' of bircl cranial kinesis has r-rot beer-r proposed before and deserves attention. Previous authors have suggested earlv birds strch as Hesperornis and Paralrcsperornis (Biahler et al. I9B8) and el'en Archaeopteryx (Verslur,s I9l2; Sirrpson 1946; Bock 1964) rnav have had an ancestral forn'r of noclern avian cranial kinesis. Others, hou'ever, har,e hr,pothancl n-iodern birds, then the

esized that Archaeoptertx possessed an akinetic skull (Simonetta 1960; Beecher 1962). Although some n'orkers had addressed the earlv stages of avian cranial kinesis r,r.'itl-rin birds (Zr,r'eers and Vanden Berge 1997; Zu'eers ei al. 1997), little attention has been paid to examining the e'u'olutionarv ongin of ar.ian cranial kinesis. Certainlr', as is generallv true for rlost paleontologicai questions, furthcr n'ork on u'ell-preserr.,ed fossils uill aid reconstructions of tl-re evolutionarl,origins of avian cranial kir-resis.

This ivork

l-ias been the prodr-rct of rnanv conversations on the topic r.vith Pete Larson, Phil Currie, Jorn Hururn, and stuclents in mv lab (the Deep Time Speciaiist$. 'fhis rvork lr'as supported bv funding from Canada Researcl-r Chairs, Natural Sciences and Engineering Research Council of Canada and Fonds qr-r6b6cois de la recherche sur la soci6t6 et culture.

\\i J. 1951. Feeding adaptations and sr,stematics in the avian order Piciformes. lotLnrcI of the Washington Acadetnl, of Science 43: 293-299. 1967. J'he bio-rrechanics of the bircl skull. Bulletin, Chicago Academt of

Beecher,

Acknowledgments

References Cited

Science l1: 10-31. -. Bial'rler, P, \.{artin, L. D., ancl Witnrer, L. \1. 19E8. Cranial kinesis in the Late Cretaceorrs birds Hesperornls ar.rd Parahesperontis. Aulr 105: I1I-I77.. Bock, W. J. 1963. The cr:rnial evidence for ratite affinities. P.79-i1 in Siblev, C. Cl., llicker,, ). J., and Hicker'. NI. B. (eds.) Proceedings of the 13th Internation

al

O rnithologic

al

C on gress.

American Ornithologists' Union, B:rton

RoLrge, F'L.

1964. Kinetics of the avian skull. /ournal of Nlorphobgy II4 I-42. Carroll, R. L. 1988. \tertebratePaleontologl,andEvohLtion. \\1. H. Freeman, New

-.

York.

Cunclall, D. 1983. Actir itv of head nuscles during feeding bt snakes, a cornparaIire rlrrdr. Anterican T,ooloyiql ]3: ?b3-396 Cuthbertson, R. 2005. IleconstiLrctirrg Bracltvlophosaurus canadensis (Haclrosaurin:re): nrorphological rer,ision ancl insight into hadrosaurs cheri'ing. P. 18 in Branian, D. R., Therrien, F., Koppelhus, E. B., ar.rd Tar,lor, \!l (eds.) Dlnosaur Park Stmposium. Special Publication of the Roval T\'rrell N1useum, l)mrnheller, Alberta, Canada. Gauthier, J. 19E6. Sar-rrischian nronophrlv and the origin of bircls. Pl-55 in Padian, K. k-d.t. The Origin of Birds and the Etolution oi Flight. N'lenroirs of the California Acadernr" of Science E. Gussekloo, S. \\i S., VosseLnan. NI. G., and Bout, R. G. 2001. Three dimensiorral kinenatics of skeletal elements in avian prokinetic and rhr,nchokinetic skulls cleterrninecl bv roentgen stereophotogrammetr\'. lournal of Experintental Biolog,r 204: \ i-35-L"44.

Palatal Kinesis

251

\\l S., and Z'"r'eers, G. A. 1999. The paleognathous ptervgoid-palatinum conpler. A true character? Netherland lournttl of Zctology 49:29-43. Hofer, H. 195'1. Neue Untersuchungen zLrr Kopf \lorphologie. P 104-i17 in Portnrarrrr, A., ar.rd Sutter, E. (eds.). Acfa Xl Congressus lnternationalis Ornithologici. Birkhauser Verlag, Basel. NtlcDon,ell, S. 1948. The bonv palate of birds. I. T'he Paleognathae. Auft 66:520549. Nlolnar, R. E. 1991. The cranial anaton-rv ofTyrannosaurus rex. Palaeontographica Abteilung A 217: 11 t--176. Non.nan, D. B. 1984. On the cranial n.rorphologv and evohrtion of ornithopod dinosaurs. S),rrpotir*, Zoological Societ y- of London 62: 521-546. Sin.ror.retta,A. NL 1960. On the mechanical inrplications of the ar,ian skull and their bearing on the evolutior-r and classification of birds. Quarterb Reviet,. of Biology 16 706*220. Gussekloo, S.

Simpson,G.G. 1946.Fossilpengr-rins.BulletinoftheAmericanMusetLmcfNatural History 87: 1-100. C. 1999. The ei'olution of dinosaurs. Science 281: 7137-2I1 ,-. Smith, K. K. 1980. llechanical significance of streptostvlr,in lizards. Nature 281:778-779. Westneat, M. Wl 2004. Evolution of levers and linkages in the feeding rnechanism of fi shes. Inte gratite and Contparative Biologt, 44 : 37 8-389. Verslu,vs, I. 1912. Das Streptost-vlie-Problem ancl die Bervegr-rng irn Schaclel ber Sereno. P.

Sanropsida. Zoologia I ahrbtLch, Sup pleme rt 15 (2) : 5 45 - ;- |6. Zusi, R. L. 1984. A functional and evolutionary an:rh'sis of rhvnchokinesis in birds. Srnilhsonian Contributions to Zoolog,t 395: l-'10. Zlr,eers, G. A., and Vanden Berge, J. Zoology 100: 181-202.

C.

1997. Birds at geological boundaries.

Zweers, G. A., Vanclen Berge, J. C., and Berkhoudt, H. 1997. Er.olutionarv patterns of a'n'ian trophic diversification . Zoology 100: 25-57.

252

Hans C. E. Larsson

Figure

1

5.1. Restoration

of the M. adductor manu lae extern us su perf i cialis et medialis of Ty-

d ib

rannosaurus rex. J, jugal; postorbital; PO, QJ, qua-

Abbreviations: d ratoj uga

l, S, squa mosa |;

SA, surangular.

Ralph E.

Molnar

RECONSTRUCTION OF THE JAW MUSCULATURE OF TYRANNOSAURUS REX

15

Ralph E. Molnar

Tl-ris studt'is part of a series on the craniai norphologv olTyrannosaurus rex that originallv forn-red m1' Ph.D. dissertation at tl-re University of Cali-

fornia, l,os Angeles, tt I973. 'l'he descriptive and structr-rral analvtical parts have alreadv been published (N{olnar 1991, 2000) and present information relevani to this work. Since I973, a total of I reconstructions of the cranial mtrsctrlature of T. rex have appeared: Horner and l,essern (1993), Ushiyarna (1995), and Farlor,r'and Molnar (1995), the first 2 likelv done independentlv of the l97l dissertation. These reconstructions agree rvith that presented here. But no account of the reconstruction of the cranial n-rusculature of T. rex has appeared since 1971, although such a reconstruction had appeared more than 80 years ago (Adams l9l9). Paul (1988) published a reconstrtrction of the superficial musculatve of Alloscturus fragilis, inciucling the superficial jarv rruscles, and brieflr'discussed the jau'rruscuiature of theropods in general. The onli'other accourlt of the disposition and function of the jar,v musculatr:re of a large theropod is that of Mazzetta et al. (2000) for Carnotaurus sastrei. \'IATERIAL: Of the specimens of T. rex exarnined for tl-re dissertation (given in N4oh.rar 1991), onlv ANINH 5027, LACN4 2V844, and N{OR 008 proved useftrl for this studr'. AMNH 600 (.Allosaurus fragilis) ard AMNH 5747 (Corgosaurus libratus) also proi'ided significant inforn.ration. Further specimens were exarrined for this chapter: BHI 1031, BHI 4100, and BHI 6230, as n'ell as casts of N{OR 555, }lOR 980, and ZPAL MgD-l/4. The use of tlre ternt fenestra follou's that of \,{olnar (1991) in referring onll. to an apertnre, not also to the excavation (fossa) that mav surround cranial fenestrae. \'{ETHoDS: For modern organisms, description of the arrangement of muscles and the ir bonr,' attachrnents is a matter of carefnl dissection: it is

conceptually straightforward, ifrather less so in practice. For extinct tetrapods, the reconstruction of rnusculature is rnore difficult (unless one is so lucky as to have avail:rble one of the extrernely rare speciilens in wiricli some trace of the rnusculature is aciually preserved). Irnportant comments regarding the reconstructior-r of nrusculature in extinct organisrns are gil'en by Ostrom (1961). Before the 1970s, rruscles of extinct organisms were reconstructed bv analogv n'ith the arrangement of muscles ir-r seleciecl modern analogs. Basically this involr'ed conceptuallr locating the muscle attachments on the fossil rvith reference to selected points or landrnarks of

Jaw Musculature

Introduction

Origin

Insertion

Add. mand. ext. sup. med.

Smooth surfaces on squamosal and quadratojugal

Surangular facet

Add. mand. ext. prof.

Supratemporal fossa

Analogy with crocodilians

Add. mand. post.

Analogy with crocodilians and lizards

Analogy with crocodilians and lizards

Supratemporal fossa: analogy with birds and lizards

None

Ptorvnnidorr< rni

Analogy with crocodilians

Analogy with crocodilians and lizards

Ptpr\/nnidarq nnqt

Analogy with crocod,lians

None

Intramandibularis

None

None

Dep. mand.

Smooth surfaces on paroccipital

Smooth concavities on articulars

PcAr

rdntamnnr:li<

processes

laDle | ). | . Ktnos of LVtdence Used in Establishing Attachment Area

the norphologv of the appropriate bones; mriscle scars, lr'here thev can be discerned, are the best landrnarks (Table I5.i). Where mrtscle scars could not be discerned, rnuscles \\,ere asslrmed to att:rch to correspolrding parts of homologous elements. If, for example, a muscle extended frorn tire suprater-rporal fenestra to the clorsal margin of the surangular in the moclern analog, tl-ren this n,as its corlrse r'r'hen reconstructecl in the fossil (Table

li.1).

The critical feature is the selectior-i of appropriate analogs. 'l'here seerns iittle difficultv in extrapolating muscle strr.rcture among phr'logeneticallr,'closelv relate d forrns-sar', Alligator mississippiensis to Crocod,-lLLs porosus, and probablv to forn'rs as phr'leticallr. distant as Sebecus icaeorhinus. Hor'r'evcr, arbitrarv clccisions are inr,'olvecl lr'here the mnsclc scars are inclistinct, imperceptible, or substantiallr'clifferent in forrr. Tl-irs, for morpl-iologicallv clifferent or more distanth'related forrns, this rnettrod becomes

problerratic. In atterrpting to ertrapolate from A. mississippiensis to the dornestic dog, for example, tl-re r-rumber of arbitran.decisior.rs becornes nnrnar-rageablv large, the confidence in the result corresponclingh' small, so it nust be concluded that the one is not an acceptable rnodel for the other.

Thus, the ciroice of a rnodem ar-ialog rriust rel1, on ha','ing a sufficicnt nurrber of indepencler-rt osteological features in common to give cor-rfidence that the structure in cl,restion-l-rere the cranial skeleton-did in life function

as analogs to some desired level of sin'rilaritr'. In the case of ti'12trnosallrs and crocodilids, tiiese features inclucle sl-iarpll' pointed teeth, snouts long rclative to tl-re postorbiial part of the skull, ancl cliapsid postorbital cranial structure (probabli'more than a single feature). After choosing a nrodern analog, the muscle attachments are located, and it is ascert:tinecl r'r'hether or not nuscle scars (i.e., char:rcteristic indications on the surfaces of the bones to r'r'hich uuscles attach) are present, and if present, the positions and forms of these scars. In rr1'experience, muscle scars are often more casill,recognizecl bl'toucl-r (bv changes in the surface texture of bone) than bv sight. If scars are not present (or r-rot obvious)-rn other u,orcls. if the surtace r-rf the bone has:r texture that is unifonr across

Ralph E.

Molnar

the area of attachment and continues rvithout change into regions where other muscles or otirer tissues attach-then one can only appr6xillate the attachment site bv referer-rce to nearbr'landrr-iarks. If the n-roderr-r ar-ralog is judiciousl-v chosen, those scars seen on the fossil should be similar in posrtion and form to those of the analog. Ceneralli,; not all of the attachn-rent areas u'ill l-rave easih' recognizable scars, and some approximation of the location of the areas bv other landrnarks ivill be necessar\'. h-r principle, a second, logically ir-idependent course is to compare the forms of the indii'idual mnscle scars. 'lb use them in an independent fashion requires comparisorr of the forns of the scars, rather than the patterr-t of their placement. For exarnple, a straplike muscle n,ill leai,e scars that are long and narrow. Therefore, to reconstruct the position of a straplike mr-rscle, one needs to find relativelt.long, narron, scars for the origin and insertion. If scars of some other forrn are found, then either the muscle is placed in the rvrong position, or it is incorrectlr,' reconstructed as straplike. This method asslrmes tl-rat one alrcadt' has some notion of the nr-rscular form that car-r be r-rsed to identifl'the muscles that attached to the scars. Used rn isolation, this rrethod u'ould indicate where rruscles u,ere present, but it would proi'ide no clear guide as to their arrangernent. In other rvords, attachment sites might be four-rcl on different elements, br-rt wl-rich site on one elerrent corresponds to lvhich on the other reurains unknorvn. As pointed outbl'N4cCorvan (1986, and citations therein), italso sr-rffers frorn tl-re disadvantage that rliuscle scars are not aln'al's present or recognizable, even if the bonv surfaces are rvell presened. Tlius, at best, this n-retl-rod can be used as a partial check on the previous one, but it canr-rot itself provide a reconstruction of the rnusculature. So in reconstructing the rnusculature of an extit-rct tetrapod, sorle guidance from modern analogs is necessarr'. Lizards and crocodilians \\'ere n,idel,v considered as rnodels for dinosaurs before the 1970s. The relationship of theropod dinosaurs to bircis implies that these, too, rnav be poteniial models. Hor,r'er,er, the cranial structrrre of bircls is rnuch modified from those of large theropods, el'en those as closell related to birds as tvrannosauroids. 'l'he paitern of muscle scars ma)r be compared i,l'itl-r the pattern of muscles seen ir-r birds, crocodilians, or lizards to determine wllich is more similar to that olTyrannosauruE rex. For example, the M. addr,rctor rnandibulae externus profundus takes origin in lizards from the region of the posttcn-rporal fenestra, but in crocodilians from the region of tl-re supratemporal fenestra. In theropods, the posttemporal fenestra tends to be closed and lacking clear inclication of muscle attachment. However, there are inclications of rnr,rscle attachrnent arouncl the supratemporal fenestra. 'l'hus, here, crocodilians r,r'ere selected as the nrore appropriate model. On the other hand, tlie crocodilian NI. pseuclotemporalis originates from the laterosphenoid r,'entral to the sr-rpratemporal fenestra. In sorre birds (e.g., CepphtLs grylle, Gallus domesticus; Lakjer 1926), the NI. pseudoten-rporalis originates anterior to the N'1. acld. n-rancl. prof. fron-r tl'ie lateral side of the braincase in the region that is presurnablv hon-roiogous to the rnediai r.vall of the char-inel leaclir-rg to tl-re supratemporal fenestra in their theropocl ancestor. Thus, the N{. pseudoten-rporalis is located anterior to the M. add. law Musculature 257

mand. prof. As described in the appropriate section, inT. rex, the subdivision of the supratemporal fenestra suggests tl-rat the M. psei-rdotemporalis arose from this region anterior to the N{. add. mand. prof., and hence was located anterior to thai muscle. Here the pattern of these birds (and some lizards) seerns the more appropriate model. Bv rreans of such considerations, the 1aw rnuscle pattern of crocodilians \\,as chosen as a generallr.' appropriate guide, although the patterns seen in lizarcls (ancl birds) also pror ide rrsefrrl cornparisorrs. In tl-re living crocodilians, as in otl-ier tetrapods, the jarv musculature sometimes lear.'es characteristic muscle scars. Fleshv attachments are generalll, 611o smooth, flat, or nearl-v flat sttrfaces of bones. Such scars are sonetimes set off from the general surface bv a distinct rim or angr-rlation (as in the case of the M. adductor n'iandibtrlae externus superficialis et n-redialis insertion) and sometirres not (as r.vith the M. adductor n-randibu1ae posterior origin). Tendinous attachmenis tencl to arise from ridges along the sr-rrface of tl-re bone (as u'ith the crocodilian A tendon; Iordanskv 1964) or frorr sharp ridges of the element (as rvith the strrface tendon of the N{. pterl'goideus posterior). Bv r,rsing tl-rese indications of rnuscle attachrnent, together u ith the patterns of mr-rscle origin and insertion in living crocodilians, the jan, musculature of T. rex ltas been reconstructed. Reconstructions of the individual muscles and the musculature as a whole are presenied in a series of figures, u'hereas the text deals r.vith the ratior-rale for the reconstructions, the comparisons with living fonns, and the form and position of the muscle scars. McGoi,van (1986, and citations therein) found considerable variation in the pattern of muscles in the lr,ings and hind lirnbs of birds. Specificallv, he found that some muscies u'ere developed to different degrees on different sides of tl-re animal, or ir-r some cases, even absent on one sicle, as lvell as differentlv developed in different indivicluals of the same species. Exarnination of lacertilian cranial material in the Northern Arizona Universitr Quaternarl Studies Program collection showed that muscie scars of sin-rilar form r'r'ere present in conparable positions across a range of species (Chamaeleo calyptratus, C. melleri, C. oustaleti, C. parsoni, Ctenosaura pectinata, Furcifer pardalis, Hl,drosaurus amboensis, Iguana iguana, Polychrus gutturosus, and Tupinambis teguixin). However, thev ma1, var\, in details of form and degree of development, are nore prominent on larger specimens, and are not seen on specirnens smaller than 50 mm in length. The sinilarit,v of the muscle scars of both sides of the cranial skeletons of T. rex, exanined iogether r.r'ith consideratior-rs of feeding efficac1,, sr:ggests that individual variation u'as not a problem ir-r this str-idl'. Hor'"'ever. onlr' 3 specimens of T. rex lvere exarnined, ard so these resr-rlts should not be extended to other specimens u'ithout appropriate exarrination. The data on the origin ar-rd insertions of lacertilian jarv muscles are taken largelr from Lakjer (1926), Bolk et al. (1938), and Oelrich (1956). Some of the attachments u'ere verified in specimens of lguana iguana, Ctenosaura pectinata, and Yaranus kotnodoensis, but most of the data are from the literature. The data for the crocodiliar-r jarv musculature attachments are taken largelv from rry ou'n dissections of Alligator mississippien-

258

Ralph E.

Molnar

M. abductor mandibulae externus M. abductor mandibulae externus supereficialis et medialis (M. add. mand. ext. sup. med.) M. abductor mandibulae externus profundus (M. add. mand. ext. prof.) M. abductor mandibulae posterior (M add. mand. post.) M. abductor mandibulae internus M. pseudotemporalis M. pterygoideus anterior M. pterygoideus posterior M. intramandibularis

sls and Paleosuchus trigonatus. This has been supplerlented ',vith data on other genera taken fronl Iordansk,v (1964).

TERMINoLocv: The rnuscle terrrinologv r,rsed is that of Tage Lak;er

Table '1 5.2. Terminology Used in Description of Jaw

Abductors

(1926) for crocodilians, but lr'ith slight n'rodificatior-rs. I n'as unable to distin-

guish betu'een the NI. adductor rnandibulae externus superficialis and the M. aclductor r-nanclibulae externus nredialis in mv dissections of Alligator mississippiensis and Paleosuchus trigonatus. Even in lizards, these parts fuse and are thus difficult to distinguish (Oelrich 19>6; Fisher and Thru-rer 1970). Tlrese rruscles do not appear to have separate attachrnent scars in T. rex (aI-

thouglr tlrel' do in Allosaurus fragilis). Hence, I shall refer to this n'ruscle as the N,{. adductor niandibulae externus superficialis et rnedialis. The strr-rcture of the ptervgoid-quadrate region of the skull of T. rex differs cor-rsiderabll' from that of the crocodilians, and as a resuit, it is not feasible to treat the M. pterygoider-rs as divided into 4 portions, as Lakjcr did.'l'hr-rs, onl1, a N'{. p1s11. goideus anterior and a M. pterl'goideus posterior n'ill be distinguished here. The terminology that rvill be used for the jau' adductors (abbrel,iations used foilou'the full r-rame) is listecl in ]-able 15.2. Iordansky (1964) has pr-rblished a thorough description of the jar,r'mlrsculature and the associated tendons of the Crocodrlia. Previous r.r'orkers (Lakler 1926; Anderson 1936) had r-roted the existence of the zr,vischensehne (a large iendon sheet associated u,ith t}-re insertion of the M. pterygoideus anterior, N{. pseudotemporalis, and M. intramandibularis of crocodilian$ but had not condr-rcted the thorough, detailed investigation of the tendinous structure that lr,as r-rndertaken bl'lordanskv. Although reference u,ill be made to these structures, a descr\rtion of the tendons and tiieir terninologr,'li ill not be presented here because there is no el,idence for their occrlrrence inT. rex.

N{. ADDUCTOR N{ANDIBULAE EXTERNUS SUPERF'ICIALIS

E]' N{EDIALIS

(rrc. r5.r): Arnong living lizards, these 2 portions are distinguishable (but

Reconstructed Musculature

sonetimes n,ith difficulty: Oelrich 1956; Nash and Tanner 1970; Ai,ery ancl 'l'ar-rner l97l).'fhei,'usuall,v arise from the r,entral and internai surfaces of the supraten-rporal arch, and fibers also arise from the quadratojugal and the an-

terior surface of tlie quadrate (Lakler 1926; Oelricli 1956;

F

isher and Tanner

law Musculature

259

Figure 15.2. Cross section

through the anterior margin of the squamosal (dorsal) process of the quad ratojugal of Tyra n nosaurus rex in a plane perpendicular to the anterior margin (as indicated by line A of the lower d rawi ng). Ante ri o r is to the left. The anteroI atera I -faci ng su rface of the quadratojugal, between the diagonal bars, is that possibly giving origin to a part of the M. srlrl mand aYf

ITF

\

rn

med. Abbreviations: lTF, reg ion of i nf rate m po ra I fenestra; L, lateral surface; M, medial surface.

1970; Nash and Tanner 1970; Averl,and'l'anner 1971). Among living crocodilians, these 2 portions cannot be easill'distingr-rished (cf. Iordansky' i964) and are here considered as a single muscle. In the crocodilians, tl-ris n-mscle originates frorn the ventral surface of the quaclratojugal just above the infratemporal fenestra, with some fibers corning fron'i the posterior rvall (formed bv tl-re quadrate) of the channel ascending to the supraten-rporal

fenestra.

lnTyrannosaurus rex (AMNH 5027 and LACNI 27844), the concave anterior margin of the qr,radratojugal, rvhich bounds the posterior extensiorr of the ventral portion of the infraternporal fenestra, bears along the ver-rtral nrargin of the upper ramus a smooth surface extendir-rg posteriorlv frorr the margin of the fenestra over onto the lateral face of the elernent (Molnar 1991, pl. I, fig. 5). This surface is posteriorlv bounded b1' an abrupt rim (fig. 15.2). In N{OR 008, this rim bears mgosities, ar-rd in MOR 980, it is raised into a low but distinct lateral sl-relf. 'l'he rim separates the smooth surface adjacent to the fenestra from the roughened external bone surface. Uniquely, the quadratojugal of MOR 980 has a distinct rostroventralll'facing facet on the lorver rnargin of the upper ramus, r,l'hich, like the lateral shelf, is more marked or-r the right elernent. Because these features are on the lateral wall of the adductor cl-ramber, sirnilar in position to the area of origin of this rnuscle in rnodern crocodiiians, it is believed to represent part of the area of origin of the M. add. nrand. ext. sup. rned. The central portion of the squarnosal also posteriorll'bounds the posterior extensior-r of the upper portion of the infraternporal fenestra. Around the apex of this part of the fenestra, there is a srnooth surface on the squamosal Ralph E.

Molnar

extending frorn the margin of the fenestra over onto the lateral face of the -l'hrs element (Fig. I5.3), sirnilar to that of the rnargin of the quadratojugal. region is bounded posteriorh'bv marked, 16s,, obtuse ridges on both squamosals in AMNH 5027. as well as on those of N{OR 008 and N{OR 555. In BHI 1031, BHI 4100, and BHI 6210, the ridge on the dorsal ramus is developed ir-rto a sharp crest, forming tl're surface into a shallow r.'entrally facing trough. In MOR 555 (and ZPAL NIgD-ll4,Tyrannosaurus bataar), the crest has become a pronrinent lateral shelf. Because of the similarity in form to the quadratojugal feature just described, ancl because of its appropriate location, these features are also considered to be part of the origin of the Nll. add. nand. ext. sup. rnecl. The internal surface of the squamosal of MOR 4100 has a lou', oblique ridge parallel to the ventral edge of the upper rarrus, about I cm frorn the edge. This presumab\,marks the n-redial edge of the rruscle attachrnent. These features suggest that some fibers, presumabll' of the M. add. nand. ext. sr-rp. rned., mav aiso have originated from the rnedial surface of ihe quadratojugal-squamosal flar-rge betn,een the dorsal ar-rd ventral posterior extensions of the infratemporal fenestra. Or again, the mr-rscle may have been separated into dorsal and ventral parts. A structure roughly sirnilar

Figure 15.3. The origin scar

I

ae exte rn us su -

perficialis et medialis on the squamosal of Tyrannosaurus rex, left and

right sides.

lnsets

show

the attachment area in diagonal hatching. Some af fhi< raninn nn fho

right side appears to have been reconstructed in plaster. Photos of the Los Angeles County Museum of Natural History cast of AMNH 5027.

to this surface is also found on the quadratojugal of Allosaurus fragilis (AMNH 600) and arnong the other tl,rannosaurids, u'here it is r-rot as marked. (Because distinct scars that can be interpreted as representing both the M. add. mand. ext n.red. and the NI. add. rrand. ext. sllp. ma), be seen on the skuli ofA. fragilis in addition to this quadratojugal feature, the latter presumabiy does not mark the origin of or-re of these 2 portror-rs.1 The proposed area of origin of the M. add. rnand. ext. sup. nrecl. is based on the recognition of featnres tl-iat appear to be rnuscle scars and are in an approximately homologous position (posterior part of the lateral rvall of the adductor chanber) to the area of origin in living crocodilians. Thus, the M. add. rrand. ert. sup. med. in T. rer is assnmed to have arisen from the squan-rosal ai the posterodorsal corner of the infratemporal fenestra, as rveli as froni the internal surface of the supratemporal arch. This situation is essentialll'sirnilar to that described in hadrosaurs (Ostrom 1961). Additional fibers rr-ia1' have originated from the medial surface of the squan-rosal-quadratojugal flange and fronr the anterior rrargin of the quadratoiugal. These fibers u'or-rld be shorter than those originating fron the more dorsal infratenporal region ancl hence capable oflesser percentage exten-

Jaw Musculature

of the M. adductor

m a nd i bu

261

(

Figure 15.4. (A) Stereo-

nhnfnnranh af the in<ertion scar of the M. adductor mandibulae o\ tarnl t<
small inset shows the location of the scar on the mandible.

sion, in keeping n'itl-r thc decreased clistance betn'een the areas of origin and insertion, relatir.,e to that of the more dorsallr' attaching fibe rs. In the lir ing crococlilians, the NI. add. rnand. ert. sup. n-recl. inserts onto flat facet on the dorsal margir-r of the surangular. This is located jtist antea rior to the glenoid. Anrong the living lizards, fibers of these muscles insert both onto the bodenaponeurosis and the clorsal n-rargin of tl-re sr-rrangular, as n'ell as or-ito acljacer-rt bones (Lakjer 1926 Oelrich 1956; Fisher ancl Thnner 1970; Nash ancl 'lhnner 1970;Aven'and Thnner 1971). 1'lie clorsal margir-r of the sr,rrangular of T rex (A\'INI-I 5027, BHI 1033, BHI 4100, BHI 6230, L,ACM 2)814, and N'IOR 008) bears an anteroposteriorlv elongate facct (F'ig. 15.'f). This facet is bounclecl :rnterolateralh'by a lor,'' btrt distinct ridge and is composed of 2 ahrost-plane subfacets. The n-redial of thcse subfacets is alrrost horizorrtal in transverse section ancl slightll'convex upu,ard in parasagittal section. The lateral subfacct faces dorsolaterallr, and is sin'iilar to the medial in forrn. The angulation separating theni becomes indistinct posteriorl-v so that the subfacets fuse togetirer. Tl-ris feature probably represer-rts the area of insertion for the Ni. add. rrancl. ext. sup. mecl., ar.rd tl-re eristcncc of

the subfacets suggcsts that this nnrscle had a bipartite strncture anteriorli'. I{ou,e'"'er, the surangulars of BHI 'f100 and \tOR 008 do not shou, these subfaccts; instead, this region is sn'roothli convex. In BHI 3031, BHI 4100, and \,IOR 008, the rnedial edge of the fircet rises into a sharp crest, perl-raps indicating the cxistence of a tendor-r. This proposecl arca of insertion is basecl on tl're sirnilaritr,of botl-r the position and form of the putative nuscle scar to those seen itr modern crocodilians. Ralph E. Molnar

In ihe liF ing crocodilians, tliis muscle originates frorn around and wiihin the sr-rpraternporal fenestra, r,vhereas anong the lil'ing lizards, it originates frorn the region of the posttemporal fenestra (Lakler 1926; Oelricl-i I956; Fisher and Thrrner 1970; Nash and Tanner 1970; Avert'and Tanner 1971). In Tyrannosaurt$ re\ the snpratemporal fenestra is surrounded br'' a ror-rgl-rl1' bowl\,I. ADDUCTOR N,IANDIBULAE F,X'|ERNUS PROFUNDUS (rrC. r5.5):

shaped, smooth-surfaced supraternporal fossa, and the posttemporal fenestra

This is sirnilar to the condition in crocodilians, shallower ancl less borvllike in forrn. InT. rex, the suprateniporal fossa is deepest over the parietals, shallowing abruptlf in the frontal region. The parietal portion of the supratemporal fossa, as rvell as the snooth anterior face of the supraoccipitai crest, presurnabll'forrned the area of origin of the N,l. :rdd. rrancl. ext. prof. No clear delirniting rnark for ihis muscle could be found on the supraoccipital crest, although the rugose texis almost completely closed.

although there, the fossa

is

Figure 15.5. Sketch of the

left squamosal in dorsal view, based on BHI 4100. The proposed area of origin of the M. adductor ma nd i bu I ae extern us p ro fundus, based on BHI 3033 and 8H14100, is to the right of the dashed line. Anterior is to the right, Iateral to the top.

Scalebar=5cm.

ture along the dorsal margin strggests that this r,r'as not part of the area of flesl-rv origin. In ml'dissertation, I suggested that this muscle rnav also have taken origin from a flat surface on the dorsr-rm of the squarnosal. This seems to be correct, but not in the ser-rse intended in the dissertation, lr'here I had believed that the entire dorsal face n'right har.e given attachrnent to the muscle. N{ost of the dorsum appe ars to be too rough in texture for a muscle scar. Hoil'ever, Tom Carr (personal comnlunication) observed a crescentic smooth surface mediallv adjacent to the rnargin of the supratemporal fenestra on tl-ie squarnosals of BHI 3033 (and less clearlv on BHI 4100) that appears to have been a muscle attachrnent. Thr-rs, it seerris likelv that a portion of the M. add. nand. ext. prof. took origin frorn the dorsum of the sqtramosal.

N4ediallr', the parietals rise to forrn a sagittal crest that is mr-rch lou,er than the supraoccipitai crest. Hence, it rvoulcl seem that the antimeres of

this n-ruscle probabii'rnet across this crest.'l'he lateral surface of the parretal is sr-r-rootl-i all the riav to its ventral margin. This smooth surface continues dolvn across rnost of the posterodorsal portion of tl-ie lateral surface of the laterospher-roid and the anterodorsal corner of tl-re lateral surface of the prootic 1Fig. I i.71. The supratemporal fossa consists of 2 parts: first, the shallor'r'er frontal excavation anterior1.",, and second, a deeper posterior excavation bounded bi the parietal, the supraoccipital crest, and the arch

Jaw

Musculature

263

:

-. ,' ,'E "

' t:

:

' '::

: !:';1

11,.:;. .

":.::-"-

;.:

::!

$#"iir"....:*fu'.' ; '.: *srffiF.;.: .

Figure 15.6. Oblique anteroventrolateral view of the braincase of Tyran-

nosaurus rex, AMNH 51 17. Most of the lateral

r,:,,lir;;r:

ffi;ii

-,,,{^-^ ^l +1,^ ^^.;^+-l )ur /o!E ut LI lc yat IcLat

K

(labeled "Pa." on the

*

anan friennlo<

A

A

1oo

o+o

A

.l^

120 )

ont.

Dit.

20

aarna-

saurs; open circles, non-

400

ithom i mosa u r, no ntyrid coel u rosa u rs kom psog nath i ds, the r i zi nosau roi ds, ovi ra ptoro o rn

600

5aur5, dromaeosaurt; solid circles, ornithomimosau rs; so I i d tri a ng I es, ty ra n nosa u ri ds. Abb rev ia -

tions: Dil., Di lophosau-

rus wetherilli; Gig Giganotosaurus.

,

800

1000

1

200

1600

Skull Base Length (mm)

ra n n osa u

A

2

100

Ar

:^^ ts

odu E

5ao

||AA AA a

l'n- tr

.9 oou^^ =

A

.rd, Aar

a

6

A

'jP 9dFt@ _

A Gig

tr

LIU

Dit

trt

6 U-0

200

400

600

800

1000

1200

1400

1600

1800

2000

Skull Quadrate Length (mm)

B Thomas R. Holtz Jr

orbit diameter against skull base length (A) and skull quadrate length (B). Symbols as in Figure 20.2

2.5

2.7

log Skull Base Length (mm)

A

r) UV +n d iA

\J@

o

T

trLr

=

^io

AA

4l| L-]

U" mE) "fl-

1.4

rA v

o

o

Dit.

2.1

2.3

2.5

2.7

log Skull Quadrate Length (mm)

2.9

3.1

3.3

B

tive allometrv relati',,e to total body height, n'hile leg length grov,'s at positive allonetrl'. Plotting tl-re orbit diarneter verstrs the skull base length (Fig. 20.2A1 and skuli quadrate ier-rgth (Fig. 20.28) shorvs that orbit size increases as skull size increases. Furthermore. it can be seen that the orbit dian-reter size of tyrannosaurids is not at1'picallv snall, but is instead comparable to that of other large theropods (carnosarirs and ceratosaurs) of the same skull lerrgths. (The immense carnosarlr Ciganotosaunrs and the coelophl'soicl Dilophosaurus wetherilli, holr'er,er, do have orbit diarneters that plot rvell below those of other tl-reropocls of comparable skull length, and these taxa migl-it u'ell be characterized as beadl'-e1'ed.) Plotting the base l0 logaritl-rrns of orbit diarneter and skr-rll lengths (Fig. 20.3) allon,s for the calctrlation of the allonetric equation for these data. If the slope of the regression line of the plottecl clata is less than 1.0, the featr-rre in quesiion demonstrates negative allonetrv relatir,e to tl-re fcattrre against r,vhich it is plotted. The reduced major aris regression lines for theropod orbits have siopes of 0.44 (r'vhen plotted against skull base length) ancl 0.48 (rvhen plotted against skull quadrate length). Thus, orbit size has a fairll'large ObligateScavengrngHypothesis 375

negati\re allon'ietrv cornpared il,ith skull size

-or,

to put it a different r'va1; the

rest of tl-re skull grou's faster than the orbit size. Sin-rilar patterns can be seen

in the grori,th of inclii,iclual species of various dinosaurs (e.g., Carpenter et al. 1994; Horner and Currie 199'1; l,ong and \'Ic\amara 1995,1997; Carr and Williarnson 2004). Thus, tl-re orbits of tvrannosaurids are not r-rr-rexpectedly' sn'rall, brrt their srnaller relative size corrpared lvith those of Velociraptor (for example) is a product of allornetrr,. Additionallr', the e-ve functions as a photon-catchir-rg device. Although the orbit of a tvrannosauricl is srnaller in relative terrrs conpared n'ith skull length than in sn.r:rller theropods, it is still a much larger opening in absolr-rte ternrs. Indeed, the orbit diarneter of the largest measnred specimen of a tvrannosaurid, (TtrannosdurTts rex, F\'INH PR208l) is 120 rnr-n. Even though the actual aperture (pupil) oitheir e1'es',l,ould be srnaller than this I20-nrrn dianeter. tr rannosaurid e) es potentialll' had large light-catching surraces.

Hind Limb Proportions find a p:.rrticttlar ecological significance to the small e1,es of |'rannosaurus, he is clear r.r'itl-r l-ris functional interpretaiion of the hir-rcl lirnb proportions of tvrant dinosaurs. Horner and col-

Although Horner (1994) could

r-iot

leagues (Horr-rer 1994, \997; Horner and Lessem 1993; Horner and Dobb 1997) observe that tr,rannosatrrids, unlike srnall theropods sttch as dromaeosanricls, have tibiae that are onll' as long or shorter than their femora. In moclern animals, a tibia/fernur ratio that is greater than I is often associated u,itli anim:rls adapted to mnning (Hildebrand i974; Coon'ibs 1978), u'hereas lon'er r.'alues are associated i,r"ith anirnals incapable of rur-rning. Horner and colleagues (Horner 1991, 1997; Horner and Lesserr 1993; Horner and Dobb 1997) argue that if t1'rannosaurs \vere incapable of rr-rn-

ning, thel' n'ould be ir-rcapable of chasing dow'n lil'e prev, and thr-rs n ould have been restricted to being sca\rengers. Before examining the tyrannosaurid cor-rclitior-r ir-r partictrlar, it should be pointed out that although there is a ger-reral trend for elongation of distal elerrents in more cursorial animals. tire absolute value of thc ratio or the

rnetatarsus/femur ratio does not scale directl1, u'ith speed across clades (Garland and janis 1993; Carrano 1999). For exan'iple, modern species of Equus tvpicallv har.e tibiae that are as short or shorter thar-i their femora (r'alues ranging fron-r 0.84 to I.00, average 0.92, for lB individuals; Holtz 1995), r'et thev are undeniabll'cursorial animals. In the present analisis, 2 aspects of tyrannosaurid lirnb proportions ri'ill bc examinecl. First, hou'do t1'rannosauricl hind limb proportiotts compare n,ith those of other theropods, particr-rlariv u'ith regards to a]lornetr\'? Seconcl, ho'uv do tt'rant dinosaur hind limb proportions conpare rl'ith those of their poter-rtial pre','itens, large-bodiecl ornithischians sttch as hadrosattrids and ceratopsids? Theropod limb proportions have been srtbiect to a number of previous str.rdies (Coombs i978; Gatesr' 1991; Holtz 1995; Gatesv and N'liddleton 1997; Christiansen 1997, 2000; Carrano 1999; Farlon'et al. 2000). Of par-

376

Thomas R. Holtz

Jr.

Figure 20.4 Plot of tibial

femur ratio against femur length for various theropod d i nosa u rs. Symbols. solid triangles with apex u pwa rd, ty ra n nosa u r i d s; sol id circles, orn ithom i mosaurs; open squares,

other theropods.

ticular interest are the stuclies of Holtz (1995), Gatesy and Nliddlctor-r (1997), Carrano (1999), and Firrlor.r' et ai. (2000), in rvhich tl-re hincl ]irnb proportions of different clades of theropods were colnpared ri,'ith each other. The prescnt anali'sis trpclatcs aspects of these w,orks. Figure 20.4 plots the ratio of the tibia length to fernur length ('l7F) agairrst femur length (r-rsed as a prox\r for bodv size) for r,arions theropod clinosaurs. Anong nonavian theropods, there is a decre:rse in T/F as fenrur ler-rgih increases (as noted by Gatesv 199i; Holtz 1995; and Carrano I999).

The hvpothesis that t1'rannos:mrids hai'e tibiae that are onlv

as lor-ig or shorter than their femora is not supportecl bv tl-re clata: this is tme for larger specirnens, bLrt not for srraller individuals of tvrant dinosatrrs. Indeed, the sn'rallest tvrannosaurs had T/F r,'alues as high as those of ornithomimosaurs (ger-rerallv regarded as anrong the sr,r,iftest of dinosatrrs; Barsbold and C)sm61ska i990) of the sar-ne fenroral length and higher than those of other

nontvrannosaur, nonornithomimosaur theropods of the sarne bodl'size. In fact, even the largest individual
phenonenon is courmon to rranl'groups of anirnals, including ungulate, carni'u'erous, and marsupial n-iammais, and manv groups of flightless birds

(lloltz 1995). For a given feniur lengtli, houever, tvrannosauricls and ornrthornirrids have a longer absolute (and thus relative) tibia and rretatarsus length than those ofother theropods. ObligateScavengingHypothesis

377

Figure 20.5. Plot of tibia (A) and metatarsus (B)

1

lengths against femur length for various thero-

pod taxa. Symbols as

1200

tn

Figure 20.4.

400

1

e

000 8oo

Oann .g

tr

4oo

600 800

1000

1400

1200

Femur Length (mm)

F

ooo

J

400

I

rnn

E

o

1600

A

^la Ala a lF':t r-41 r-l n

cd tr

[n_ Lr t_r-

G

=

zuv 100

600 800 1000 1200 Femur Length (mm)

1400

'1600

B

hr other r'r,ords, for a given femur iength, tvrannosauricls l-rave a longer clistal limb length than thosc of most otl-ier theropods. Sirrilarlt', tvrannosaurids and ornithomirricls of tlie sarre femur length irave cornparablc tibia ancl nretatarsal lengths. 'l'hr:s, for a given angle of rrotion of the fcmur, a tr,rannosaur coulcl cover more clistancc than an allosauroid, ceratosat1r, or other large-bodied tlieropod of the samc femur length. Becaltse clistancc cor"ered per r-rnit of time is the clefir-ritiorr of speed, all other things being equal, tl'rannosaurids shoulcl have been faster than artl' other coniparablv sizcd theropod (see also Carr:rno 1999). (Note that this does not consider, or c\,en require, a fully'sr-rspended phase during this fen-roral nlotion; Farlou' et al. 1995, 2000; Hritchinson and Garcia 2002; Hutchinson 200'1) These dzrta are consistent i'i'ith a nroclel in lvhich tl'rallnosattts ll'ere sri ifter than other potcntial competitors. Of more important col]cern, horvever, is hon' the lirnb proportions of tr,rannosaurids corrpare r'i'itli those of tlieir potential prcl'. Examittation of 378

Thomas R. Holtz lr.

Figure 20.6. Plot of tibia/

femur ratio against femur length for various western North American Late Cre-

.1

taceous dinosaur taxa. Symbols: solid triangles

E

+ .g tr

0.8

with apex upward, tyran-

o.o

nosaurids,' +, hadrosaurids

and other bipedal ornith-

o.4

i sch ia

o.2

sau

1200

Eoo

F

eoo

!

f,

AIF ,.,A^

;

J

A+ ++

000

C

"4

-XX ++x *,&Y A

Figure 20.7. Plot of tibia (A) and metatarsus (B)

lengths against femur for various western North American mid- to upper Campan ian d nosau r taxa Symbols as in Figure 20.6. r

+oo

600

F

soo

F

400

3 6

i

300

$

zoo

s),'

x, ceratopsians.

0

1

ns (pachyce ph a lo-

rs, Thesce I osa u ru

a

100

Obligate Scavenging Hypothesis

379

Figure 20.8. PIot of tibia (A) and metatarsus (B)

lengths against femur for various western North Am eri ca n M aastri chtia n dinosaur taxa. Symbols as in Figure 20.6.

A1

it',rr^+ ^-r4 +

E

E

c

ouu

X

c

Jo

XX

600

.g

i=

400

J

,+a 600

800

1000

1200

Femur Length (mm)

800

700

^

AA

Ano

^a^

E

i j

soo +oo

E o

300

=

200

o

.,x

+

100

+

0

600

800

1000

Femur Length (mm)

1200

1400

1

600

B

the TiF ratios of lvestern Nortl-r Arnerican f,ate Cretaceous ceratopsids, l-raclrosauricls, ancl other nonankr'losaurian ornithischials (Fig. 20.6) shor,r,s that these herbivores ha",e as lorv or lolve r'lJF scorcs as sl,mpatric tr''rannosaurids of the sarne ferntrr length. Indeed, the values for large haclrosauricls tencl to cluster u'ithin tlie clustcr of large tr,rant dinos:nrr specimens, ri'hiie ceratopsians have considerabiv sl.rorter T/F ratios. F igure 20.7 plots the tibia ancl metatarsus against femnr lengtl-r of ornithischians and tvrannosatrrids from the rnid- to upper Carnpar-rian stagc Judith River Group ancl its southr.r,estern U.S. stratigrapl-ric equivaler-rts. Figure 20.8 sholr,s the same for the younger N{aasirichtian stage fatu-ras of u'estern North America (e.g., Horseshoc Canvon, Hell Crcck, an
ral ler-rgth. Fnrtherrnore, the netatarsi of tvrannosaurids are rnuch lor-rger than those of ornithischians of the same bod1, size. 'fhr-rs, the total distal

linb lergth f

380

h;rr r cor

of tyrannosaurids is at least as long, anci t-vpically rruch longer, rlerrrnorarv orn itl r isclr ilrrs.

Thomas R. Holtz

Jr.

ltdt

tro

)l I I

PIAt 6t f tht)

(A) and metatarsus (B) 1200

lengths against femur for various western North American Late Cretaceous dinosaur taxa (combination of data from Figures 20.7 and 20.8). Symbols as in Figure 20.6.

E E

;

800

o

J .! i=

600 400

##.

700

-A

c E

-o

j

E a

aoo

-rl.fiiJ r T 'T

300

o

E

IA

I f-^f rr

2oo

AA a

+ +xdx

'100

0

1400

1600

B From this evidence, it is clear that tvrannosauricls ',vor,rld cover more ground for the sarre angle of femur motion than hadrosaurids and ceratopsids of the same body size. In other words, thev r,vould travel furtl-rer per unit of time (i.e., r,r'oulcl be faster) than their potential prev. Again, as before, ihis cloes not require a suspended phasc oir the part of tl-re tvrannosaurid. Linib proportions do not disn'riss the possibilit)'that t)'rannosaurids could or.ertake conternporary herbivores, ancl incleed they are consistent ',vith a model in which tvrant dinosaurs were faster than their potential prev. (Note that the above cliscussion does not take into acconnt the great disparity betn'ecn forelimb and hind lirnb length in cer:rtopsians. This might indicate that ceratopsids were necessarilr'slor.i'er than a ful\'bipedal dinosaur of similar hind iimb proportions, unless the forelinrbs noved r.vith faster steps than the hind limbs in order to keep pace.) To put ii another 11,21,, if (as Horner argues) the lorv T/F values of TyrcnnosdurtLs and its kin i,r'oulcl hinder them fron runnir-rg to catch tl-reir pre1,, the equally lou' or er.en lower T/F r,alues of hadrosaurids ancl ceratopsids',voulcl even more greath,hinder the abilitl'of these ornithischians in rururirrg fronz a pursuing tl,'r:rnnosaurid. Additionally, tvrannosaurids possessed an arctometatarsus, a moclifi cation of the foot that bion-rechanical :rnaivsis suggests \r'as rrrore effective at Obligate Scavenging Hypothesis

381

Figure 20.10. Tyrannosaurid arctometatarsus (A) compared with more primitive metatarsi of other theropods (B) and ornithischians (C, D). (A) Right pes of the tyrannosaurid Tarbosaurus, sh owi ng g raci I e p ropo rtions and pinched third metata rsa I co nd iti o n. (B) Right partial pes of the carnosaur Acrocantho-

saurus, showtng more primitive unpinched condition and broader foot. (C) Right pes of the hadrosaurid Edmontosaurus. (D) Right pes of the ceratopsid Centrosaurus. Scale bar = 100 mm

A

C

D

the distribution of forces of loconotion (Holtz I995) (Fig. 20.10). Recent analvses b1'Sr-rivelr'and Russell (2002, 2003) and Snivel)'et al. (2004) have dernonstrateci that this adaptation night additionalh' serve to resist torsional forces, allow'ing tl-rem to turn rrore rapidlv than thev might othern'ise rvithotrt risking mechanical failure of their narrow rnetaiarsi. Ceratopsids ancl l-raclrosaurids lack this adaptatiorr, or other morphological correlates n'ith rrore cursorial function (Coombs 1978; Carrano 1999). Short Arms T\,rant clinosaurs are characterized br,greatlv redr-rced ams (Russell 1970; N{olnar et al. 1990; Carpenter 1992; Holtz 2001, 2004; Lipkin and Carpenter this r,'olurne). Indeed, tvrannosaur arms are greatli' recluced in 2 different senses. First, all knolr,n tl,rannosaurids are functionallv didactvl: the1,possessed onlv 2 fingers. N'lore importantlv, the overall arrr length is quite sniall compared n'ith the bodr.,size. Iior example, the humerus of tvrannosaurs rs onlr, 0.26 to 0.10 times as long as the fer.nur, compared \\'ith 0.19 tn Allosaurus (Ciln-rorc 1920) and Afrovenator (Sereno et al. 1994), and 0.44 in Dilophosaurus (\Velles 1984). The giarrt allosauroicl AcrocanthosauruE lias a humerus/ferrur ratio of 0.29 (Cr-rrrie ancl Carpenter 2000). At present, the forelirnb of the largest allosauroids, Giganotosaurus and Carcharodontosaurus, are unknon'n or undescribed, so lve cannot determine rvhether tvrannosauricl arms are uncharacteristicalll' short cornpared t'ith other camivorons tlreropods of this size. (The theropo ds Deinocheirus andTherizinosaurus, both of the Nernegt Fornration of N,{ongolia, are large theropocls u,ith long forelinrbs. Hot'e','er, the forrrier is probabh'an ornithornimosaur and the latte

r a therizir-rosauroici, clacles of coehrrosarlr vu'hich n'ere n-rost likelv herbivo-

ror-rs

lRussell ar-rd Dong 1993; Barrett 2005; Kirkland et al. 2005].) Regardless of u'hether the arrrs of tvrannosaurids are uncharacteristi-

call1' sl-rort, the argnments of Horner and colleagues (Homer 1994, 1997; Horner and Lessem 1993; Horner and Dobb 1997) rernain r''alicl. Given the

reducccl size of these structures. it is difficult to envisiot't a rlettrod ir-r lvhich the forelinrb n'iight have been deployed in prev capture. Carpenter and Srrith (2001) and Carpenter (2002) denonstrate, on bionrechanical grounds, that these limbs r'r,ere forcefulh'clesigned btrt had a rrore limited rarrge of rnotion compared with Allosaurus ai-rd Deinont'chus.

Thomas R. Holtz

Jr.

Accepting that the forelinbs of T. rex or anl,tvrannosauricl make unlikely ippl6ments for seizing prev items, does this support tl-re argument of obligate scavcnging in the tr,rant dinosaurs? 'l'he rnechanics of predation can be dii,ided into 2 rliain components: prei,' acquisition and prel' dispatch. Amor-rg modern terrestrial predatorl'rrarnrnals, there are sonte taxa that use the forearrns ir.r prev captlrre (e.g., felid$, w'hile others clo not (hvaenids, canids). Feiids use clar,i's to accluire tl're prer.' and jan,s to clispatch them. The latter forn'is use the jari.'s as the primarv \\'eapons of prei capture as \\'ell as pre)'dispatch; tfre forelintbs, if trsecl at all, are primarilv used ir-r stabilizing the prey item nhile the jan's inflict the prirnarl,u'or-rnds. Carpenter and Smith (2001) support this fur-rction in the por.erful but sl-rort forel i nbs of Tt ranno s aur tt s. N'Iodern predator\,birds do not use their forelimbs (u'ings) as the primar\, wcapon of prev capture or dispatch. Instead, their hind lirrb is used as a prilnarv \\'eapon of prel'capture and dispatch (except for falcons, lvhicli during prel dispatci-r use their talons to hold the prer, but the beak to ser,'er the r.'ertebral colurnn) (Brou,'n and Amadon 1968; Cade 19E2; Hertel 1995). Ho',l,evet, the predatorl' techniques of flr'ing raptorial birds are ditficult to colrpare directlr u,ith those of ground-bouncl ar-rimals such as carniverous nammals or theropod dinosaurs. Thc extir-rct flightless carnivorous birds sucli as Diatryma and the larger pl'ronrsrhacids, horvel'er, rnight be nsed as more informative models

for tvrannosaurids. In Diatryma, the forelimb is extraordinarilv redtrcecl (Ntlatthen, and Grangcr 1917); in at least sorne of the phorusrhacids, the forelimb is short but apparentl,v qr-rite nrassi','e11, constructed ancl bore a clar,v (Chandler 1997). If thesc fcrrrrs ll'ere incleed predator\,, it is unlikell' that thel coulcl l-rar,'e used their forelirnbs in prev acqtrisition, and in Dlatryma, thet' r','ould hale becn r:nlikelr,to have been useful in prel'dispatch as lvell. Hon,ever, as lvith nonavian theropods, direct field obsen,ation of tl-re pred:rtor,v techniques (if an1') of tl-rese forms is clenied us. AltfioLrgh tr,rannosaurid arms mav have been used to stabilize the food iten'r (prel' or scavenged) rvhile feeding, thev seerli to have been too sl-rort to be used to capture prer'. Hor.r'ever, sone modern terrestrial predators (hvaenids and canicls) are capable of acquiring prev ll'ithout usir-rg therr forelimbs. Sirrilarlr', if Diatryma and phorusrl-racids n'ere predators, thev rlost likell'used their skulls alone rather than the forelinbs in prev capture. Thus, a forelimb incapable of prev capture does not obligate a carnlvore to a scavenging lifestvle, although it does eliminate sonie strategies for prev acquisition.

Incrassate Teeth

Tl,rannosaurid teeth are distinct from those of other tlpes of theropods, contra Feduccia (1996). N4ost theropod teetl-r have a nanow, lens-shaped cross section at the base, and the rnesial anci clistal carinae (bearing the serrations) ertencl up the front edge and cloiin the rear edge ofthe tooth. This condition is known as the ziphodont (sri'ord-toothed) conditior-r in the paleocrocodilian literature (e.g., Farlon'et al. 1991; Busber, 1995). 'I\,ran-

adigate Scavenging

Hypothesis

383

nosallricls, hor.r'ever, have lateral (r'narillari' ancl clentart') teeth that are exp:rnded basallv side to side, ancl tl-rcir carinae are offset fron-r the fror-rt ancl rear edges of the tooth. Such dentition has been terrned incrassate (Holtz. 2001, 2001, 2004), after the Latin incrassatus, "thickened." (One of rrany specics narnes Cope proposed for isolated tr,rannosauricl teeth ll'as Laelaps tncrdssdtus.)

Florner (1997) sr-rggestecl that t1'rannosaurids' incrassate tooth form nrav have been more associ:rted u'ith bone-cmnching abilitv, uhich l-rc correlated rvith scavengiirg, than rvith slashing flesh, ri'hich he associatecl il'ith predation. Other authors consider bone cnrnchilrg, or at least bor-re biting, to have been part of the feecling repertoire of tyrannosaurs but do not disrniss the possibilitv of :r predatorv life stlle for these theropods (Bakker 1986; Farlolr'and Brinknan 1987, 1994; Bakker et al. 1988;Abier 1992, 2001; Erickson and Olson 1996; Erickson et al. 1996; N{eers 1998, 2003; Carpenter 2000; Hururn alrd Currie 2000; Hurum ancl Sabatli 2003; Schubert and L.lngar 2005; Therrien et al. 2005). Confirrnation of the bonc-crutrching nature of tvrannclsaurid iarl's is revealecl in a coprolite from the latest N{aastricl-rtian Frenchman Fornatior-t of Saskatcheu'an (Chin et al. 1998). This specimen, almost certainlr'generatccl b-v T\,rannosaurus rer, contains the broken fragments of bortes of a medirrn.r-sizcd ornithischi:ur dinosaur. Furthcrmore, specinens ofEdmontosatLrus ctnnectens (Carpenter 2000) and Triceratops (Erickson and Olson 1996; Erickson et al. 1996; Happ this volune) clemonstrate T1'ranrnsattrus bite ruarks in u'hich a portion of ihe bone of the herbivore rvas remo'n'ed. Hyaenicls are bone-crunching specialists among thc large-bodied carnil'orons rnammals of tl-re rnodern u'orld, but as discussed above, all modern hr.aenicls are knou,n to

kill

prel', and the largest (Crocuta

crouia) obtains the

niajoritl, of its food in this r.nanncr. Bone cmnching is accomplished bv the rnolars and premolars in hl'aenicls (trlver l99E), but sr-rch a feecling rnode u'orild result in potentialli'risk to their canincs. Incleed, h1,2.tr'Ot do have thicker caninc tectl-r than found in nodern non-bone-cmnching dogs, but felids har,e canines of comparable morphorretric proportions to hvaeliids. Van \hlkenbr,rrgh and Ruff (1987) interpret the sirrilaritt' in canine dimensions of hr''aenids and felids not to similar feecling behaviors per se (big cats have not been obscrved to habituallv feecl on bones to the sanre degree as hvaenicls), but as aclaptations to resist contact r'vith bone during pre1,'capture or clispatch as lr,ell as cluring feeding. Furthermore, Van Valkenburgh and Ruff (1987) demonstrate that the bites of hvaenicls and felids ger-rerate grcater forces than those of ciinids, and thus teeth that are thicker (and, consecluently, more resistant to benclir-rg) would be less likell to fail as a rcsult of loads in

ant'direction rvould have

a selective adr,antage.

Thc rccent discor,erl' of theropods of comparable size to t)'rannosaurids allor.vs a comparison of giant ziphodont aud incr:rssate teeth. The subconical teeth ofspinosaurid theropods (tloltz 2003), u4rich also differ frorn the ziphodont condition, are considcrecl a third categorl'for this anal1'sis. Nllorphometric plots confirm that ty'rannosauricl and spinosaurid teeth differ from ziphoclont theropods ir-r l-raving greater base r.r'iclths compared u'ith

fore-aft base lengtl-r (Fig. 20.11A) and crou'n height (Fig. 20.llB). 384

Thomas R. Holtz

lr

Figure 20.1 1. Plot of tooth

45

width against forelength (A) and crown height B) for various theropod taxa. 9ymbase

40

^la ^

35 E

30

.l -A .-I

25

;

20

E

15

o

aft

A

T AX

r,o

I 1r

t^rl

a

bols: solid triangle, tyrannosaurids; x, typical

ziphodont theropods; open circle, spinosaurrds.

^o*#f

10

5

A

0

30

10

Fore-Aft Base Length (mm)

A 45 4A

^ f rl

35

1A

A

a^a a

a ts^{

!zc

E

X

Ezo o

Srs 10

r,*

5

0

020

60

80

base

120

100

140

Crown Height (mm)

B Van \hlkenburgh ar-rcl Ruff (1987) and Farlon, et al. (1991) converted tooth measr-rrernents into bending strength indices using beam theorl'. 'l'he present analysis follorved the calcuiations of Fariorv et al. and nsecl a rectangular cross-sectional moclel rather than an oval model for ziphodont ancl tvrannosaurid teeth. These values do not represent actual strength values, br-rt rather indices comparing the relative resistance of teeth to loads of r-rnit valLles.

When both the anteroposterior (AP: Fig. 20.12A) and rrediolateral (N'l[,: Irig. 20.128) ber-rding strength index are plotted against cron'n height, it is founcl that t\,'rannosar-rrid and spinosaurid teeth u,ere more resistant to

bending in either directions than ziphodont teeth. 'Ihis u,oulcl be consistent ii'ith a h\raenidlike bone-crunching habit for t1'rar-rt dinosaurs, but r,i oulcl also be consistent li ith the pattern seen in felicls compared u.,ith canids: a more poi,r,erful bite in tl'rannosaurs than in typical theropods, and better chance of accidental contact betr',,een tooth and bone. That tvrannosaurid teeth contactecl bone during feeding is evidenced bv various bones with deep furrou,s or punctures gene ratecl by tvrant clinosaur teeth (Horner and Lesserr 1993; Eirickson and Olson 1996; L,rickson a

O

bl ig

ate Scaveng i ng Hypothesis

an-

Figure 20.12. Plot of teroposterior (A) and me-

(B)bending strength indices against crown height for vailous theropod taxa. Symbols as in Figure 20.11. Tyrannosaurid teeth typicalty have higher bending strengths than those of other theropods with the diolateral

po

A

e

1oo

At

E

3 E 3

uo

A oo

^^lo ^

rA

g

E

.o

E

,o

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l\ 4^:1'^

X

X

same toath height. 0

140

160

A 180

5

A

160

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Iao !^^ oou E

€+o

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20 0

60

80

'100

120

140

160

Crown Height (mm)

B et al. I996; Carpenter 2000; Happ this volune) ancl bv the Frenchmarr coprolite (Cl'rin et al. I998). Horvevcr, the incrassate teeth of tyrannos:nlrs r.nav have also functior-recl during pre,v capture ancl dispatch. Hon-rer and colleagr-res (Horner 1994, 199i; Horner and Lessem 1993; Horner ancl Dobb 1997) argue that bec:ruse the forelirlbs of tr"rannosaurs cor-ild not be tused to capttrre prcv, the on11,' other likelf inrplernent to seize a victinr u'ould be the jar,r.'s-a viell'l fincl reasonable. Hor.r'er,'er, Horner fr,rrther argues that the teeth of tvrant dinosatrrs u'oulcl be likelv to fail during the stresses generated cluring prer. capture. As shor'vn here, the teeth of tr,rannosaurids lr,ere mechanically stronger than those of other tl-reropocls. Fr-rrthermore, Erickson et ai. (1996) have dernonstrated that tr,'rirnnosaurid teetli cotrlcl r,vithstand considerable stressful contact ivitli bone (see also Nleers 1998, 2003; Ra1'field et ai. 2001; Rai field 2004). 'flius, the data suggest that the teeth of TirarulosdLLrl$ rex and its kin rvor-rld have sufficient strength to absorb the rlechanical stresses generated bi' prev capture. It is n'orth noting that the tooth roots of tvrannosanrids ancl spiliosauricls are considerably' longer than those of ziphodont theropods. Whereas

Thomas R. Haltz.Jr.

ziphodonts iypicalll' have roots that are subequal to the crou'n height, t1' rannosaurids ancl spinosaurids have roots typicall y 150% to 200% of cror,vn height. These may serve to better anchor the teeth ancl clistribute stress against the lateral forces generated during predation and/or feeding that has a greater torsional component than vertical slicing.

As seen above, none ofthe features previouslv proposed as evidence ofan obiigate predatory life habit {or'I\,rannosaurus and other tvrant dinosaurs is in fact an indicator of such iimitatior-rs. 'l'he tr,'rannosaurid eve l-nay appear to be sn-rall in relative terms, but its apparent small sizc is drie to the allometrically faster grorvth of the rest of the skull. In fact, the absolute srze of the tl'rar-rnosaurid orbit is large. T\'rannosaurid linrb proportions do not indicate a necessarily slon'speed for these dinosaurs. Instead, tibia/ferr-rur

Discussion

ratios in these dinosar-rrs are higher than those of other large theropocls, and as higl-r as or higher than tl-reir potential prey. F-urtherrnore, the longer

distal limb length of tvrannosaurs conlpared with duckbills ar-rd horned dinosaurs of the same fen'rrr length stronglv suggests that tvrannosaurs were faster than these herbilores. Regardless of whether tvrannosarrrids were capable of a fully srlspended rurrrirrg phase or not, the el idence sugcould cover more ground per stricle than their potcntial pret, and so could overtake them in a chase. The greatlv reducecl forelirribs of t)'rannosatrrids most likell' served no function in prer,. capture, but could have been rlsed to stabilize the prey cluring dispatch. Holvel'er, some rnodern (hr,aenids and canids) do not use their limbs to captr-rre their prer', but insteacl seize thern ancl clispatch thern r.vith their jaws alone. The incrassate teeth of tyrannosaurids mav indicate a bone-crunching habit for ty'rant dinosaurs, but bone cmnching and predation are not mutuall_v exclusive behaviors in rrodern carnivores. Additionalll', strong teeth arc also for-rnd in rnodern predators as an adaptation to u'ithstand forceful bites and the gests that they

during precl:.rtion. Although this reanall'sis of the proposed obligate scavenging correlates does not support that h1'pothesis, it excludes certain pred:rtor_v behaviors frorn the tyrannosaurid repertoire, and it is cor-rsistent r.vith the findings of others. A catlike model, in which the forelimbs arc used in prev capture and a cornbination of il'ouncls generatecl by the raking hind limbs and a suffocating bite (Seidensticker and McDougal i993; Tirrner and Anton 1997), is exciuded because of the irnprobabilitv that t1'rannosaurids cotrlcl seize prel'll'itir their (relativelv) tinv arrns. Such a behar.ior rvould be more consistent il'ith dromaeosaurid dinosaurs, and indeecl nav be recordecl in the fanrous "fighting clinosaurs" specimens (Jerzvkielvicz et al. 1993, fig. ll; L-lnrvin et al. 1995; Carpentcr 2000; Holtz 2003). Siniilarli', a hau,klike moclel of predation, in lvhich the clau,'ecl talons lr,ere the prirnarv method of killing, is uniikelv because botl-r tl-re fore- and hind clan's of tvrannosaurids are relatively straight (Holtz I994, 2004). The han'klike forelimb clar.vs stresses generatecl

of allosauroid s,Tort,osatLrus, DryPtosatLrus) and sorne other large theropocls indicate that the clalr's nrav har.e served a sirnilar function, althougl-r these taxa presurrabll'lr,ould have also used their jaws in prer dispatch.

Obl igate Scavenging Hypothesis

387

T\'rannosauricl anatonrl,' is consistent ri'ith sone rnodels of predation, hou,ever. The relativeh' elongate legs of tvrannosar-rrids suggest that tl'rev rvere faster than ttreir potential prer,., altl-rotrgh absolute speecls wotrld be difficult to deterrrine 'nvithor,rt a trackr,r'av recorcl. L,r'en though tl-re fore]irlbs of tr.rannosaurids li'ere srnall, their skr-rlls n'ere large ar-rd pori'erfulli'

built, and

(as shon,n abol'e) their teeth u'ere proportionall',, stronger and more resistant to ber-rclir-ig in r,arious directions than those of other theropocls. 'l'hesc clata are cor-rsistent rvith canid or ]'ryaenid models for tvranno-

saur predation: forms that run clor,r'n their prev anil use the jalvs for both prev captrrre and prev dispatch, and that use the forelin-rbs onh'for stabilization dr-rring prer,' dispatch and feeding, if at all. (Tl-ris arralogv clescribes the behar,'ior of hur-rtir-rg bv canids ar-rd hi'aenids against relatir''el1' large prer.. While pr-rrsuing small items, such as arthropods and small rodents, strch predators u'ill use their fcrrelimbs r.vhile pouncing on their victims. Horver,'er, even the rr-iost ardent supporter of active tl'rannosaurid predation noulci be unlikelv to suggest a co-votelike pounce ir-r the predator\,- reper-

toire of TyrarLnosaurus rex! ) Additional support for tl're hypothesis that t1'rannosaurids u'ere canidor hyaenidJike j:rn.capturir-rg predators can be four-rd in the roof of tvrant dinosaur rnotrths. T\''rannosaurids differ frorn other large-bociied theropods, r,iih the erception of spinosaurs (Taquet and Russell 1998; Sereno et al. 1998), ir-r thc possession of :r substantial ossified secondary palate (Holtz 1998, 2000, 2001, 2004;. Busber.(i995) has denionstrated biorneclianicaill' that the development of a large bon,v seconclan' palatc in tire skulis of crocodilians resulted in a morphologv more resistant to torsional forces tl'ran those of the ancestral crococlvlomorphs, rvhich had ziphodont teeth and a theropodJike skull forn.r (Russell ar-rcl Wu 1997). Sin ilarlr'', a tvpical theropod skull would be relatir,'eiv strong in r,ertical corrpressive loacls, but it rvoulcl lack solid support to resist strong torsional loads. 'l'he solid bonl'palate of tvrannosaurids, forn-red bv tl-re medial exter-rsions of the rliaxillae and prenraxillae and the greatlr,'expanded diamond-shaped anterior end of the vomer, lr,ould allow for greater resistance to torsional loads. As Moh-rar (2000) argues, horvever, the verticallv oriented niaxillae of trrannosaurids, as opposed to the rrore horizontally oriented maxillae of crocodilians, indicates that the primarv loading in these skulls ri'as still conrpressive. N{echanical (Erickson et al. 1996), theoretical (}leers 2003), and compnter-aiclecl mathematical (Ray,fielcl et al. 2001; Ra1'field 2004; Snivelr et al., personal corrrrunication) models of the skull olTl,r4nnotourus sr-rpport a por,i,erful bite for this theropod. Altl-rough the data are cor-rsistent u'ith this particular rnodel, thev dcr not derronstrate that tr,'rannosaurids lr'ere active predators. As noted previoush', such dernonstration is difficult evcn for extant carnir''ores, except bv direct observation. Adclitionallv, as noted above, a successfttl predatior-r attempt n,ould be difficult, if not inpossible, to distinguisl-r from a scavenging event on a carcass, particularlv if il-re traunas that produced the victirn's cleatl'r lvere not recorded in tl-re hard tissr-res. Hor.r'ever, there does appear to be direct fossil er"ider-rce for at least somc unsuccessftri predation events b1't,u-rannosatrrids. Carpenter (2000) Thomas R. Holtz

Jr.

has clescribed :r specimen of thc hadrosatrrid EdmontosarLrrLs dnnectens frorr.r the Hel1 Creek Forrnation of Montana.'l'his specimen demonstrates a pathological trarrrna in the caudal region: se','eral consecutir,'e neural spines are damaged and the central one shearecl off. Tl're shape of the lr,onnd rnatches tire shape of a theropod snout, and pits along this traurna are consistent in size, shape, and position with large theropod teeth. The hadrosaurid survir,'ecl this traurna, as evidenced bv subsequent regror,r'tli of bone in this region. 'l'his regrou,th ir-rdicates that the dtrckbill n'as alive at the tine of the attack. F1app (this r,olume) shorvs sinilar evidcr-rcc in the skr-rll of a specimen ofTriceratops horridus. At present, Trrannosaurus rex is the or-r11.knot'n iarge theropocl froni the Hell Creek Forrnation. It is conceilable that the n'ouncl w'as generatecl bv an as-vet-nnknou'n giant nontl,rannosaurid theropocl fronr the latest N{aastrichtian of n'cstern North Ame ric:r, but at pre sent, an adtrlt T. rex s the onl,l likely'cancliclate to have generated this trar-rma. Althotrgh this represents a tinl'sarrple size, these specirrens implv that a tyrannosaurid attackecl a livir-rg hadrosauricl and a living ceratopsid in separate instances. 'l'he data for tr.'rannosaurids rrav not support ths hl,pothesis for obligate scavengir-rg, but thev do not reject scavenging entirely from the behai. ior of t1'rant dinosaurs. Indeed, as Horner and colleagLres (Horner 1994, i997; Horner and Lessen 1993; Horner and Dobb 1997) and DeVault et al. (2003) correcth'poir-rt out, carrion represcnts a food resource that cloes not reqrlire the cnergy, spent in prev capture and dispatch. Furthermore, tvrant dinosarlrs \\,ere in an ercellent position to be effectil'e scavengersan excellent position literallr,, in that their great hcight rvould allorv them a mtrch rrore ertensive vieu,of the lanclscape in r,i'hicl-r to fir-rd carrion tl-ran rvor-rld srnaller carnivores (Farlor, 1994); and an ercellent position metaphoricallr', as their much larger boclv size migl-rt allolv thcn-r to easilv chasc the sn.raller dromaeosaurids, trooclontids, alcl other contenporarv carni\/ores a\vay frorn carcasses. Additionallr,, it rriar. be that different grou'th stages of tr,rannosauricls had diffcrent life habits (Russell 1970). Perhaps jui'enile tvrannosauricls \\'ere more acti."c prirsuit preclators, lr'liile adults obtained rrost of thcir foocl as c:irrion. Furtherrnore, the relatil,e frequcncv of predation to scilr. cnging niight har,'e ."'ariccl regionalh. Kmrrk (1972) obsen'ed that )2% ol the food of Serengeti populations ol CroctLta crocnta r.r'as frorn scavenged carcasses, ri,hile Ngorongoro populations of the same species sca',,cnged on|1,7% of tl-reir food.'l'here r.na1'have been seasonal variatior-r in the freqllencv of scavenging r,vithin species of tvrannosaurids: for cxanple, scavengilg might becone nore iniportant during drv seasons, or during seasons of ornithischian rnigrations. F-inalll', it rnav bc tl-rat certain species of t,vrannosaurid reliecl more on carrion than prev than did other species, as (for example) the living species of Hyaena has a greater fraction of carrion in their cliet than does the related Crocuta. I-loliever, these l-rypotheses perhaps require direct field obscrvatior.rs to test, ar-rcl thus the1, lgtnrrn speculations outsicle of currentlr, possible scientific inquir','. Finalh', although this short studv does not sr-rpport the hr,pothesis of obligate scavenging in t1'rannosaurids as currentlv framed, this hvpothesrs

Ob

I

igate Scaveng ng Hypothesis r

389

is

onll provisionallv rejected. Aclclitional lines

of evidence

nav indeed sup-

port the idea that tvrant dinosallrs \{:ere incapable of routinelr. killing to provicle thenseli'es with food. Untii such time, horvever, there is r-ro evidence to suggest that tvrannosarlrs \\'ere radicallv different ir-r diet fron-r living l:rrge-bodied carnivores, r.vhich obtain food both predation and scavenglng.

Conclusions

The hvpothesis of obligate scaverrging i:nT,-rannosaurus rex and other t1r;rnt dinosaurs is provisionallr' rejected. Previous morphological features suggested as cclrrclates of this hvpothetical life habit were not for-rnd to reject tl-re possibilitl'of predation in t-vrannosauricls. 'l'he apparent srnall size of tvrannosaurid orbits is an artifact of ailometru'; the hind iimbs of ti'rannosaurids are (rnlike their portral.ai in the obligate scavenger model) consistent u,ith a greatcr locomotor abilitv in these theropods than in their potential prel'; the short ams of tvrannosauricls mav have not been usccl ir-r prer,capture, but several living predator groups are kno'nvn to use their jau,s in seizing prel,; and the stont incrassate teeth of t1'rannosarlrs mav not havc bcen effective slashers, but w'ere n,ell briilt to rvithstand pou,erful loads. Tl-re ar-ratoml'of tvrant dinosaurs is inconsistent rvith cat- or hau'klike predator',, behaviors (ivhich necessitate the use of ciarvs in prev capture), but is consistent rvith canicl- or hl,aenidJike jan-capture rnodels. T'ire strong teeth and bonv palate of tvrant ciinosaurs u,ould allou' these dinosaurs to resist stronger tr."'isting loads, ancl occasional contact ith bone, "l than allosaurids or other tr,pical theropocls. Limited fossil evidence clocuments probabie unsuccessful predation attempts of this stvle bv tvrannosaurs. Although obligate scavenging is rejected as a nodel (pending additional evidcncc), tr,rannosaurids u'ouid be effective sca\rengers. It n:rv be that certain groivth stages, or regional or seasonal variations n'ithin species, or even lr,hole species, of tt'rant dinosaur relied rnore on scavenged food than killed prer,, but barring clirect field observation, testing these hvpotheses seerrrs irnpossible.

Acknowledgments

390

I thank the organize rs of the 100 Years of TJ,rannosaurus rex Sr,'mposium for inr,'iting rne to participate. I h:rve had (far too nanr'?) discussions on tr,rannosatrricl paleobiologv oi,er the vears n'ith r':rrious other lvorkers, and I n'oulcl like to acknon'ledge, among others, Bob Bakker, Kenneth Carpentcr, Philip Currie, Greg Erickson, fim Farlor,r,, Raiph N{ohrar, Scott Sanrpson, and Jack Ilorncr. Although our intcrpretatior-rs of the data rrav differ, such cliscussions have helped me to frame ml' studies of the tvrant dinosaurs. As ahr.':r1's, I acknon,ledge the researchers and other staff at various museurns for access to specimens in their collection o.,'er tl-re last decade ancl a half: Ted Daescl-rler, Acadernl' of Natural Sciences of Philadelphia; VIaik Norell ancl Charlotte Holton, American N{useum of Natural Histon'; Peter Larson :rnci Neal L. Larson, Black Hills \,{useum of Natural Historr'; Nlichael l-lenderson and Scott Wi]liams, Br-rrpec N'h,rseum of Naturai Histoi1,; Kieran Shephard, C:rnadian N'Inseum of Nature; N'{ichael Williams, Thomas R. Holtz

Jr.

Cleveland N{useurrr of Natural Historl'; Ker.rneth Carpenter, Dcnr.cr NILrseurl of Nature & Science; Williarri Simpson, Fielcl N{useum of Natural Historr'; David Whistler and Samuel N{cl-eod, l,os Angeles Countv N'ltrseum; N{ichael Brett-Surrran and the late Nichoias Hotton III. National Museum of NatLrral Historl,; N4akoto N,{an:rbe, National Science Nluseurn; Angela N{ilner ancl Sandra Chapman, the Natural Histori,N,Iusetrm; HansDieter Sues and Kevin Sevmour, Roval Ontar'o N{useum; Don Brir-rknan, Philip Currie, anci Jackie Wilke, Ror,al T\'rrell N'{useunr of Palaeontologl.; Sankar Chatterjee, N'Iuseum of 'l'eras Tech LJniversiti,'; N,lari' Ann 'l-urner and Cl-rristine Cliandier, Yale Peabocli' N.'luseum of Natural Historr'.

Abler, W L. 1992. The serrated teeth of tvrannosaLrricl dinosaurs, and biting structures of other auinrals. Paleobiologt' l8: 16 l -1 83. 2001. A kerf-ancl-clrill nodel of tlr:rnnosatrrid tooth serrations. P. 8.1-EC) in Tanke, D., and Carpenter, K. (eds.). \'l.esozoic\lertebrate Life. Indiana LIni-. versitv Press, Bloonrirrgton. Bakker, R. 1'. 1986. The DinosatLr Heresies. \\/illiam & \lorrou. Nerr,York. Bakker, R. T., \\rilliaLns, N{., and CLrrric, P J. 1988. Nanotyrannus, a ne\\.genus of pr"gmv tlrannosaur, from the latest Cretaceous of Nlontana. Htnteria 1(5):

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i\,iongolia: :rn oren iov of the stratigr:rphr, scdirrentarv geolog\', ancl paleontologv and conrparisons ri ith the tvpe localitv in the pre-Altai Clobi. Canacli cut I otLr tul oi Earth S c ietrces 30: 2 I Eti-2 195. Kirklancl, J.I.,7anno,1,. E., Sarnpson. S. D., Clark, J. NI., ancl DeBlieux. D. 200;. ,\ primitive therizirosauroid clinosaur frorn the ltarlr Cretrceous of Lltah. Na/ura -115: E'1-8,. KrrrLrk, H. 19i2.'I-he Sptted Ht'ena: A Studt' of Predation and Social Belnt'ior. []niversitv of Chicago Press, Chicago. 19;6 Feecling and social behar iorrr of the striped hr aena (H\aena tulga rls Desr ua rest). llasl Afrlca n \\I ildlife l ou ntal 14 : c) l - 1 1 1. -f,anrbe, t,. B. 1917. TIrc CretttceousTheropodotLs Dinosaur Gorgosarrrus. \lernoirs of the Oeological Survev of C:n:rda 100. L:rrson, P., ancl Donuan, K.2002. RerAppeal:Tlte AnnzingStort oiStLe,the Dir.rosaLrr thttt Changed Scierrce. tlte Latt. and \,Iy Life. Inr isible Cities Press, Nlontpelier, \"1'. Long, J. A., and r\{cNanrara, K. J. 1995. Heterochronv in dinosaLrr evolLriion. P. Ii1-16E in \Ic\arnara, K. J. ted.t. EvoLutionart'Charrye and Heterochront,. \\1ilev ancl Sols, \eri \brk. 1997 Ileteroclrronr': the kev to dinosarrr cvolution. P. 113 123 in \\lolberg D. L.. StLrnrp, E., ancl Rosenberg, G. D.l)hnfbst httenntiotnl Proceedings. - Acaclerul of Natr-rral Sciences, Philadelphia. \lalccr'. F,. A. 197+. Gigantic c:lrllos:tlrs of the [anri]v'lvrarurosauriclae (in Russian ri

ith English srllllni:lr\'). Soymestnaia Trudt I: I l2-l9l

ktgicheskaitt Ekspeditsiia

Sor,eslsfto-'\lori goL'skaia Paleonto.

Nlattheu', W. D.. and Clranger. \\l 1917. The skeleton ol Diatrt'ma, a gigantic bird fronr the Lori er llocene of Wloning. tstlletin of the Anterican l,'ItLseun of N atural Histort' 17 : 30i -776. NlcClouan, C. 1991. Dirutsaurs,Spitfires, rutclSeal)ragons. Hanarcl Lluiversitv Press, Caurbriclge, NI.\. N{eers, NI. B. 1998. EstiLrratiorr of nrarirrrunr bite force tnTtrarntctsaurus re.r ancl its relationship to the infere ncc of t'eeding behar ior. lournal of Yertebrate Paleontologt' I 8(Suppl. 3): 63'\.

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Jr.

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2003. \ilarirrrrrnr bite force iind prev stz.e of 'ltrannosdLrrus rex and their relationships to the inferencc of feeding behar,ior. Historical Biologt' 16: 1-12.

\{. G. 1,. 1996. Nlethodological ach'ances in capture, census, ancl tbodhabit stuclies of large African carnivores. P.223-212 in Clittlenan, i. L. (ed.). Canivore Bdntior, Ecolog1,, and Eyoftttion. Vol. 2. Cornell Llniyersitv Press, Ithaca, N\'. N,Iills, NI. Cl. L., ancl Biggs, H. C. 1993. Prev apportionment and relatcd ccological relationships betri.een large carnil'ores in Kruger National Park. P 253268 in Drrnstone, N., and Clorrnan, N,l. L. (eds.). \,Iatnnals as Predators. Zoological Societv of Lonclon Svmposiunr 65. Oxford Science Prrblications, Nlills,

Orford. 2000. Nlechanical factors in the design of the skull of Trrarmtsattrtts rex.

-

P l9l-218 irr P6rez-Nloreno, B. P.. Holtz,'l'. (eds.). Aspecfs of Theropod Paleobiologt.

J.. Sanz, J. 1,., ancl \loratal1a, J. Crtia: Revista de Geociencias. nrhL-

seu Nacional de Historitt Natural, Lisbrn, Ii. tr,lollar, IL. E., Krrrzarror', S. \'1., and l)ong, Z.-\,1. 1990. Carnosaurs. P 169-2t19 irr \\/eishampel, l)., Dodsor, P, and Osm6lska. Il. (eds.). 'flrc DinosaLLritt. L.lnirersitv of California Press, Bcrkeler'. Osens, NI. j., and Ou,errs, D. D. 1978. Feecling ecologv and its inflLrerrce on socral organization in broun hvenas (HlaeruJhrtulned, ThLrnberg) of the Cleritral Kalahari Desert. Last African \\'ildliie lournal 16: I I 3-l 3;. Radloff, F'. C).'I., and Du'lbit, j.'f. 201i4. Large predators and their prev in a southern African s:l\':lnila: a predator's size deterntines its prer,size range. lournal of Anintal Ecoloq 7):110-173. Ravfield, f . J. 200+. Cr:rnial nrechanics ancl feecling rnTtrannosarLnts rex. Proc ee din gs : B ir,,l o gic al S ci er rc e s 27 1 : i4 5 I -14i9. Rar'fielcl, Fl. J., Nonran, D. B., Horner, C. Cl., IIorner, J. R., Srnith, P \i,, 'l hornason, J. J., ancl LIpchLrrch, P 2001. Cranial design ancl firnction in a

large thcropocl clinosaur. Nafrrre .109: 1031-103-

A. P, ancl \\ir, X.-C. 1991. Thc Crocodr'lonrorpha at ancl betrrcen geological borrndarjes: the Baclen-Porvcll approach to change? Zorllogt, I}{J:

RLrssell.

164

182.

Rnssell, D. A. 1970. Tlrttnnosclurs front tl'Le Late Oretaceorts of \\'estern Canada. National Nluscunr Natr.rrai Scierces Publications in Palaeonkrlogr. l. RLrssell, D. A., ancl Do'g,2.-\{. l99l. The affiritics of a neri theropod fronr the .\lxa Desert, Inner \longolia, People s Republic of China. Canadian lottr-

rnl

of Eartlt Science

l0:

2107-2127.

Schrrriclt-Nielsen, K. 198-1. Scaling:\\'ht, Is Anin.tal Srzs So Important? Cantbridgc Llniversitv Press, Oanrbriclge. Schubert, B. \\i, and Llngar, P S. 1005. Wear facets and enarlel spalling rn tr. rarrrrosaurid dinosaurs. Acta Palaeontologica Pokn'Lica 50: 93-99. Seidensticker, )., ancl NlcDorrgal, C. 1993. Tiger predaton,behar,iour, ecologv and conserr.:rtjon. P. 105-12 j in DLrrrstone, N., and (lornan, NI. t-. ieds.). Nlarnnnls tts Predators. Zoological Societv of London SvrnposiLur 6i. Oxford Science PLrblications, Orforcl. Sereno, P C.. Beck, A. L., DLrtheil, D. B., Gaclo. 8., l,arsson, t1. C. E., Llon, (1. H., \{arcot, J. D., Rar-rhut, O. \\l \i. . Sadlier, R. \\i, Sidor, C. A., Varricchio, L). D., \\1jlson, Cl. P., and \\'ilsol, t. ,\. 1998. A long-snouted predatorv clinos:rur fronr Africa ancl the e\.ohltion of spinosaurid s. Science 282:1298-1102. Sereno, P. C., \\'ilson. J. A., Larsson, IL C. E., Dutlreil. D. 8., ancl Sues, H.-D. 199'1. Earlv Cretace ous clinosaurs froni the Sahara. Science 2 ji: 815-E,18.

O

bl ig ate Scaveng t ng Hy pothesis

Snivch, E., and Russell,A. 11 2002. The tlrarrnosauricl nretat:rrsus: bone strain rnd infcrrcd iig.rnrent function. Senckertbergiatn Lethaea El: r 3 80. 2003 .\ kinernatic lnoclel of tvrannosauricl arctonretatarsLrs function (D,nosarrria: 'l'heropodal. loLrrnal ctf Nlorplnlogt 25i: 215-221. -. Snir,elv, lr., Russell. A. P, ancl Poucll, G. L. 100+. Evolutionarv rnorphologl of the coelurosaurian arctonretatarsus: descriptive, morphometric and phrlogenetic approaches. Toctlctgical lournal of tlrc Linte att Society 142: j25-55). 'fac1uet, P, ancl RLrssell. D. A. 1998. Neu clata on spinosauricl clinosaurs fiont tite Flarlv Clretaccons of thc Sahara. Con'Lptes Renclus de I'Acaddnie des Sciertces Paris. Sciences de IaTerre et des Plandtes

32i:31i-1i7.

Therrien. F., Hcndcrson, D. \1., and Ruff, C. B. 2005. Bite nrc: triomechanical rnoclels of theropod merndibles ancl inrplications for'feeding hchatior. I'. 179-13; in Carpenter, K. (ed.). 'fhe Carnivorous DinoscttLrs.lndiana IIniversitr Press, Bloornington. 'lirrrrer. A., ancl ,'\nton, Ni. I99,-.The BigCats andTheir Fossil Rekttit'es: An l/ItLstrttted (hLide to Their Et ohLtion and Natural Histort. Colr.rrnbia Llnilersitv Pre ss. \e\\'\brk. 1995. Protocercttops tlnd\telociraptor Llrrriirr, D. \1., Pcrlc '\., and'liuerrtan, C. preservccl in irssociation: eviclence for predabrv behavior rn clrorrraeosaurid cli nosinrrs? l ou r n al oi \:er tebrat e Pale ontokt gt l 5 (Suppl. 3 ) : 5 ;,\-i 8.\. \'tn \/alkenbLrrgh, B., and Ruft-, C. B. 1987. Canine tooth strength and killiug

beh:rr,ior in large carnivores. lournal of' Zoologt' 212: 319-39 ,-. \\Ialker, F,. P i964 \Icrmtnals oitlrc\\hrld. Johns l{opkins Universitv Press, Baltimore, NID. \\'e lle s, S. l'. 1984. Diloplnstmrus v'etlrcrilli (Dinosarur ia, Theropoda): osteologr'

and cor npariso us. Palae

396

Thomas R. Haltz Jr

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ict grapl'Lic

Abte i lLng

A

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5

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8

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gure 21 .1 . Henry Fair:ield Osbarn's second F

:-^) )KC/ctdl -^ /)cu -1,^l^+^l /-^cj-^^u 'ct - ]- st-tct on of Tyrannosaurus rex teversed for conparison vtith Fig. 21.2), drawn by L. M Sterlino hased mosflv on AMNH 973 (now CM J|''

'','JI

9380) and including parts of AMNH 5866 (now BMNH R7994). Af-

ter Osborn (1906).

398

Donald

F.

Glut

TYRANNOSAURUS REX: A CENTU RY OF CELEBRITY Donald

F.

Glut

'lbdav the nane TlrdnnoEdurus rer is part of onr er,erlclar. lericon, as u,ell knor'r'n to tl-re public :rs the narnes of rrianv hunran celebrities. Chilclren not vet cognizant of the identitr,of persorrs in tl-re public eve often kno'nr,, and can even spell, the narne of this gigantic theropod clinosaur. Given paper ar-rcl pencil or modeling clar,, ther,c:rn even produce a recognizabie approxirration of T rex. h-or n'ell ovcr a clecade, onc of the most popular and belovecl rolc models alrong volrnger chilclrcn is a ptrrple, singirrg, dancing T),ranrLosatLrtLs rramecl Barner,, a character created for thc Public Broaclcasting St,steni. Incleecl, the fe:rrsorlie r.et charisnratic T rex h:rs

into a rr-rodcrn-clai' nultinedia icon. Or,er thc past centnrr', the fanriliar inage of TtrannosctLLrlts rex-atgrlablv the best knor.','n and most poprilar of clinosaurs among lavnren, as u'el1 as one of the clinosaurs rnost studiccl br, p:rleontologists-has appeared in l'irtuallr.o'erv popular \,enrle, incl:ding prose fiction, poetrr', rnotion prctures, radio ar-rcl television prograrns, theatrical presentations, comic books, evolr,'ecl

park exhibits, displar posters, tovs, g:rmes, nrodcl kits, foocl, and aclr,.ertrsirrg. \\'lrcrever tlre irrraqe of an rrrrinrrrl carr be rrsrd. T. re.r lrrs rrott likelr been there (e.g., sec Horner ancl f,cssem lggl; GlLrt 2001). Hon,er,er, before the rriidclle of the first decadc of the 20th centurr'. Tyrannosdt-rrus rer \\,:rs unknon'n.

In

1905, Her-rrr Fairfielcl Osborn, a professor and forrnder of the depart-

tnent of r.crtebrate paleor-rtologr at the Anrerican N,luseum of Naturai Historr' (AN'INI1), named the giant, Late Cretaceous carnivorous dinos:rur Tlrannoscu.rus rer (Osborn 1905). It ri,as founded on a partial skeleton chscovered in 1902 during a fielcl expedition r-rnder thc clirection of thc n-rusetum's chief fossil collector, Barnurn Brou'n, in the tlpper Cretaceous (N'laastrichtian) Hell Creek Fbrnation (then callecl Laramie Fbrmation) of D:rn,sorr Connti', irr northern \,{ontana. The same r,ear this initial paper n:rs n,ritten and ptrblishecl, addition:rl portior-rs of the specirren n.ere still being excar.atecl (Osborn 1905). Although both jari's and portions of tire

Lull, u'ho u as in chargc of the specir-nen's preparation, had not vet corr-ipletecl riork on those elctrtents. Consequentir', Osborn (190t) did not inclucle anr,cranial characters in his diagnosis of the ne\\' genus and tvpe spccies, nor did he figure the skull in detail. 'l'he next vear, Osborn ( 1906 ) publishecl a second paper on ll re.t, thrs one provicling better figures of tlre collectecl naterial. It r','as one of these illustratior-rs, as I ri'ill sl-rou belori', that constitr-rted thc basis for the first life skr,rll hacl alreadv been collected, Richard Sn'anrr

A Conn trtt af Colahritv

21 Introduction

restoratiorr of Ttrannosaurus rex in a stunnir-rg arrcl visuallv pou,erful painting that n'orrld gracltrallr' be reproclucccl in seenringlv countless popular

ptrblications, thcrcbr,shaping the public's conception of T. rex. This single n,ork of art n'otrlcl, for ahrost 3 decacles and belond, constitutc the acceptecl inragc of this clinosairr in the public eve. Iior a generation of people intcrcstecl in clinosaurs, this image wasTtrannos(1urus rex. Over the decades that folloil'ed, there u'otrlcl come a varietv of net' restoratiorrs, sorne based on e:rrlier artistic interpretations and sone more or less accurate than those that can'rc bcfore. All of those iniages contributed in shaping thc public's icleas as to iion'Jl rer m:rv have :rppearecl and :rlso hori, this giant c:rrnir,orous dinosaur

T. Rex in the

Public Eye

mal have behaled.

Bv 1905, the pr-rblic t,as alreadr,sa\'\'\'concerning the ongoing discoi,'eries of often spectacular dinosaur specimens, particul:rrlr those from the late 19th and earlr,20th centurics in North Anrerica. Houever, until thai vear, relativch'little information w'as ai'ailablc to scientist or lavr.nan conccrning vcrv large carnivorons clinosaurs. Ollv 2 r'err large North Anrerican theropods had bv that tirne been naned and clescribccl on thc basis of rcasonablv cornplete fossil nraterial: Lrtelaps (named bv E. D. Copc 1866, but latcr rcnamecl Dryptctsaurus) and A//osaurus (named bi'O. C. N,{arsh 1877). Consequentll,, tlre cliscovcrv olTtrannosaur"us, arl animal larger and more spectacular than the geologicallr olcler Allosaurus, \\'as a ne\\'s\\'orthv event. Clearlr', Osborn (1905, p. 2591 nas impressed bt"lt,rannosarirus '"r'hcn iic notcd that its size "gre:rth erceecls that of :rnv carnivorotrs lancl :rninal hitherto ciescribecl."

Osborn offered onlr a preliminarv clescription of T. rex, as n'ell as a brief, and bv todiir"s standards barelf infornrative, diagrosis basecl mostlv on size-related features. T\r'o of tlic feattrres \\'crc presuilrabll on observations made bv Banrurri Bronn: hnntems (unknori'n at the time) large and elongatc, artcl absence of dernral plates erroneotrsli' thought to be present ir Dt'namosatLrus intperiosis (nori'a junior svnolrvm of 7'. rex1. The :rrticle also provided the first, sonrcuh:rt conjectural skeletal reconstruction of T rer (Osborn I905, fig. 1) clran,n bi'Aurerican \'luseum of Natur:rl Flistorv p;rlcontologist Williarr Diller Nlatthen' (see Colbert 1992), a former prot6g6 of Osborn. 'l'he figure shon'ed the'L ren skeleton upright in left lateral vien,, :rlong n,ith the skeleton of Horno sapiens fcrr size corrparison. Al-

though the partiallr,preparecl skull cc,ruld not vet be figurecl in cletail, Osbonr did-perhaps significantlr, as I n,ill shori belori -rne ntion the alreaclr' prep:rrccl "supraorbital portion =lacrinral] of tlie frontal bone, extremeh, mgose, constituting:r horn above the orbit ren'sinrilar to that seen in A/f

losaurus" (C)sboni I905, p. 26);cl. Nladscn 1976, pl. 1). The prelirrinarv skull reconstructior-r inclucles a nunrber of in:rccuracies. N'lost notablr', the skull qas ciran,tr triangrrlar in profile, rather than rcctangtrlar, as shou'n bv later discor,crics. Thc triangular shape',ras partli' thc rcsult of the clcntarv being dr:rn'n too sl-rallon' cauclallr' (perhaps patternccl after thc
F.

Glut

the antorbital fenestra. Other inaccuracies in N{atthen"s drau'ing included the too-short neck and short cervical neural spines. Osborn (1906, fig. I) later presentccl a rer,'ised versiorr of the skull. 'fhis

illustration corrected se',,eral rnistakes, inch:ding deepening the latter por-

tion of tlie dentarr" ancl repositioning the lacrirnal. The orbit nas clrar.r,n lvith the verticallv narro\\' shape knoivn toda1,' (see also C)sborn's 1912 descripiion of the more complete skull of referred specimen AN,{NH

5027,

rvhich u,as discovered in 1905 and excavated bl,tlie American N,{useunr rrr I908). Osborn (1906, pl. 39) also incltidecl a revised skeletal reconstnrction (Fig. 21.1) dran,n br.L. N'I. Sterling, basecl on both AN,INH 971 and the refcrrccl specimen AN1NH 5866 (non'BN4NH R7994). In this version, the cervical vertebrae u.,ere correctlv depicted, adding ler-rgth ancl bulk to the neck. Assunring, albeit iircorrectlv, thatTyrannosdurus \\,as closell,related to tlre large L:rte Jr-rrassic carnosaur Allosaurus, a fine skeieton (ANINFI 4753) of rvhich had alreadv been nounted at the Arrerican \4useurn, Osborn (1905, 1906) based sorne of the rnissing parts on that genus ir-r both of his skeletal reconstmctions. Amor-rg Osborn's aims, as head of the nelr,lv established department of vertebrate pale ontologl', n,ere to enrich the Anerican N.,Iuseum's r,ertebrate fossils collections and to disseminate information about these extinct animals to the public. Because lavrnen do not, as a rule, read technical articles, Osborn sought another rneans of rnaking such inforrnation generalil, available. Osborn selectecl Charlcs R. Knight. n,ho u'as regarded as the prcrnier artist of ertinct life. Knight n'as colrnrissioned to recreate in painting ancl sculpture the various anirnals rvhose skeletons were being erl-ribited in the rnuseurn's'u'ertebrate fossils halls (e.g., see Dingus 1996). Knight, rvho had honed his skills under the guiclance of tr. D. Cope, n':rs a conscientious, fine artist, ancl also an amateur paleontologist. After Cope's de atli, Knight soon founcl hirnself under tire rrentorship of Osborn and rvorking closelv u,ith Barnnm Bron,n (Czerkas and Glut 1982). Irr arr attempt to quickh' make his cliscover], of Tyrannosatzrus knorvn to the public, Osborn had thc pelvis and legs of ANINH 973 mounted tbr displav (Anonvmor-rs 1910). fo acconpanv this erhibit, Osborn hacl Knight prepare a painting (Fig. 21.2) that ii'ould convev to rrruseurr visitors hou' this grcat anirral looked in life. Hou'ever, the skeletal reconstructions available to Knight published bv Osborn (1905, i906), incltrdecl errors: rnost notablr', the tail u,as too long (r,r'hen later mounted, the tail ofANlNH 5027 u':rs too long bv approrin.r:rtelr' 3 n, as pointed out bv Nen'rnan in 197u1. Also, the then unknou'lr r-nanlls n'as reconstructed as irt Allosaurus, n'ith l functional digits rather tlian tlie correct 2 (" g., Lanbe 1914; Carpenter and Smith 200i). Later, Osborn (1916), follor,r,ing Lan.rbe (1914) and also the i,erbal opinion of Charles Whitnev Giln-rore, agreed that the 'l-yrannosdurus nanus could eventualli' pror''e to be fr,rnctionalli' didact1,l lr'ith a r.estigial D III (see Lipkin and Carpenter this volurne). Although AN4NH 5027 ri,'as firsi mountecl u'ith a 3-fingered hand, it n'as reduced to 2 li'l-ren the skelcton u,'as renountecl in 1927 (R. A. l,ong, personal comnunic:rtion 2006; also photograpl-rs in Dingus 1996).

A Century of Celebrity

401

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this dinosaur, based on Osborn's 1 906 published ske I eta I reco nstru ctio n.

Courtesy Department

of

brary Servlces, American Museum of Natural Lr

History.

Clearlr', Knight basecl his 1906 paintirig of T. rer clirecth on tire figllre published bv Osborn that same ve:rr, becallse the painting :rpproximates a fleshed-or-rt rrirror image of the skeletal drari ing, complete ri'ith tridactr'l hands and o\.erh'long tail. As in the Sterling reconstruction (Osborn 1906), the tail is alrnost at gror-rncl lei'e I ancl the left leg is positioned slighth'back. F urthe rmore, the anirral is clepictecl in a ratl-rcr stationari', alrnost lcthargic position, appearing almost disinterestecl as it, significantlr' (see belolr.), tace s clcrri'n a f:rmilr of the horned dinosaur Triceratops (probabl1, because parts of a Triceratops frill had becr-i iound uith A\'{NH j866). Ctrriorrslr,, Knigl-it paintecl tl-re e1'e of'llrannoscturus a]rrost directh'below

the lacrim:rl hom. \\1h','Knight, nho n'orkccl closelr ',r'ith thc scientists and knerr aninral anatonn'u'e11, n'or:ld m:rke such an error is puzzling. It secrns unlikcll'that Knight, alreaclr,firrnlv r.rnder the mentorship of Osborn and u'orking closelr,n,ith Bron,n, u'or-ild hal'e folloried his former mcntor Cope in rrisiclentifving the theropod antorbital opening. C)nc suggestion for Knight's error is that the artist had refbrred to Osborn's (1905) original statement regarcling tl-re lacrirnai of T rer being positionecl above tlie orbit, and that no ore-Knight, Osborn, or Bron n-had noticed the error until the painting \\'as on exhibit.

Donald F Glut

Nonetheless, both Knight's painting ancl the skeletal clisplal'had an inn-rediate iinpact on the public rvhen the exhibit opened in 1910. A Nrew YorkTimes headline announced "'l'he Prize Fighter of Antiquitv Discorered and Restored" (see Horner ancl Lessem i993). Visitors to the exhibrt n'ere confronted b1' the partial remains clf a carnivorous animal that had never before been seen, ar.rcl the Knight painting conve.,.ed the irnage of this fantastic and spectacular beast, u'ith a hr-rge head, muscular bocl,v, ancl eaglelike hind feet-an animal suggesting a dragon or,rt of rn1'tir. hrdeed, visitors to the musenm found thernsell'es gaz.i.:.gat the partial remains and life restoration of a gigantic, terrifr,ing denizen of another age, r'et one, b1' virtue of its beir-rg extinct, that u'as non' a harrnless attraction.

The experience u,as heightened inrmensel-v u'hen, in 1915, the referred skeleton of T. rex, AMNH 5027, r,r.'as rliounted in an in-rposing vertical pose, and rvitl"r the hands, as in Knight's accompanl.ing painting, sporting 3 fingers (Fig ZLI).'l'he rnounted skeleton usecl a cast of the skull because the original n'as too heavv to be rnounted and so rvas displal'ed separatell,. 'l'he mount also trsed a cast of the lirnb elernents frorn AN{NH 973. As Osborn (1916, p.

762) stated, "Tyrannosaurus is the most superb carnir,orous mechanisrn among the terrestrial Vertebrata, in lvhich raptorial destructive pon,er and speed are combinecl; it represents the clin-rax in the evolutior-r of a series which began n'ith the relativelv small and slencler'liiassic carnivore Anchisdurus." As far as the public \\:as concerned, this skeleton, rl'ith its sktrll tou'eriiig almost to thc rnuseurn hall's ceiling, and u'ith Knight's painting reinforcing the terror, T rer was a real monster-albeit a safe one, as, being lor-rg clead, it was no longer a threat-ancl therein, I suggest, lal.this dinosaur's appeal.

A Century of Celebrity

Figure 21 .3. Skeleton

(AMNH 5027) as it was mounted and photonranhcrl in 191 5 Notc the i nco r rect u p ri g ht postu re, 3-fingered hands, and oveily long tail. Courtesy nanArtmanf nf lihrerv Services, American Museum of Natural Hrstory.

PhntnhvA F Andar
Figure 21 .4. Cover for the book America Before Man (1953) featuring L. b. rails s verston or Knight's 1906 Tyrannosaurus. Courtesy of the Viking Press.

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tirre of its cornplctior-r, Knight's trrriqne: it constituted the onli' life restoratio:n of 'ltranrLoscLttrus rex available to the scientist or the pr-rblic. Indeed, to rnanv pcoplc, cspeciallv those',r'ho n,ould never stand in the presence of thc skeletal r-nount, tl-re painting n'oulcl constitute their onli,' r"isual irriprcssion of T rer. As a r','ork of art, the p:rinting c:tnnot be criticized, except for the :rlre ach.st:rtecl errors. Nonetheless, this image-of the presunabh' slou-ruoving, 3-finHon'er,er, it rnust be stressed that at the

painting

n':rs

gered, arrd long-tailed T\,rctnnosaurus, n'itir its rrisplaced eles-bccatne, for clecacles, tlrc inage of this dinosaur. Osborn (1917) included n'hat seerrs to har,e been the first photographic rcprodrrctiori, in black ancl uhitc, of Knight's TlrrutnostttLrrLs p:rinting ur

Donald E Glut

The Origin and Eyolution of Lilb, a book conrprising a collection of that author's lectnres (also including photographs, taken in 1915 br A. L,. Anderson, of the mor,rnted AN,INH 5027; sce Osborn 1916, fig. l7). Science Press is credited in the book as havir-rg published these lecttrres the previolrs vear; hon'ever, thev apparentll' did not inchrde tlie Knight image (R. A. Long ancl f . S. N{clntosh, personal comrntiniczrtions 2006). Knight's painting rias republished nurnerous tirres over the succeecling vears ln both technical ancl popular articles (e.g., Brou'n 1919), textbooks (e.g., Schucl-rert ar-rcl Dunbar 1937), popular books (e.g., Colbert 19'15), books targeted at jr.rr,enile readers (e.g., Rcecl 1930), encvclopedia entries (e.g., Anonymous 1954), and elsen'here. Edn'in H. Colbert (1980, 1989), a proiific autl'ror and n'redia consultant as n'ell as a i'ertebrate paleontologist, authored nLurerolls technical papers and popular books about dinosaurs cluring his lengthl career. His first use of thc 1906 Knight painting n,as in I'he DinosaLLr tsooft, pr-rblished in 194j, n,hich, including a nnrrber of reprints, becarre a rliinor best seller, remaining the most popular and often-read book on the subject available to thc public into the earlr' 1960s. Colbert, in fact, continuecl to use that saine 1906 image as representative of ll rex in a nnmber of subsecltrent popular rn'ritings (e.g., see Colbert 1953, 1961). E'n'en as late as 1983, uanr'\'ears after the errors in Knight's paiirting had been recognized and correctecl in other restorations, Colbert included Knight's famous painting in one of his books. Particularlr cluring the l9i0s and i960s, Colbert n,as n'ell knon,n ancl u'ell regarclecl ar-nong clinosaur-informccl lavmert as the authoritl' on dinosaurs. His popular publications n,ere readilv ar,ailable ir-r bookstores, lnrlsellilr shops, and the public librarr', ancl his name \\'as well knori'n as authoritative outside of scientific circles. Consequentlr., inaccrrracies notn'ithstanding, Colbcrt's trse of thc Knight restoration g:rr,e it an implied ,.r.-,--^ .-..--*^. ,^dr. I ^f dlJlrru\ JLdl rrP vr Aside froni Colbert, r-nanv other w'riters frequentlr, ir-rcluclecl reclrann (and inferior) copies of Knight's 'I\,rannosatLrtLs (e.g., C. B. Fails for Baitr 1953), son-retimes u'ith onlv subtle changes (e.g., heacl or tail turned; Figs. 21.4 and 21.5). Not el'ervone, hon,evcr, rcacl books or articles abotrt dinosaurs,

Figure 21 .5. The geoI ly d isp laced Tyrannosaurus based on

g ra p h i ca

Knight's 906 painting, 1

accom pa ny i ng

" D i nosau r Hunting in the Gobi Desert," a popular article written by Roy Chapman Andrews for the November 1954 issue of Boys'

Life magazine.

A f anlt trv nf f alahrittt

Figure 21 .6. Knight's

1906 Tyrannosaurus nsinfinn rame< ln lifa courtesy of sculptor Mar ral f'laln;r'ln )n/'l .f^^-

motion animator Willis O'Brien, in the 1933 classic motion picture King Kong. Courtesy RKO Radio Pictures.

cr,cn those issued bv the popular press. Neverthelcss, Knight'.s imagerl,profouncllr' inflrrencecl icleas about T\'rannosatLrus rex in other r,enues. Perl-raps most inflrrentialh, the 1906 painting \\'as the sonrce naterial for sculptor N{arcel Delgado il'hen, arotrncl 1911, he n'as cornnrissiorecl bl RKO Radio Pictrrrcs to create a flcshecl-or-rt'Ilrannosar-rtLs ntodel that s'as to be brought

to lifc bi'special effccts naster Willis O'Bricn bi'stop-motion :rnination. The aninratiolr \\':ts intended for a nrotion pictr-rre entitled Creation. Althorrglr Creatknt n'as prerraturelv abortecl before Delgado's T rer could go through its anirrated nror,erncnts, ihc moclel n.as salvagecl for another RKO tolossrrl lrroiecl. KingKrnrqrl()13r.arrrovietirathctnrrtcrtrtirnrredi:rtelrrrl bor-office slrccess (e.g., see Goldner and Turner 1975; Glut 1978; Bern'

2002).'l'hanks to rrumerous tlieatrical ancl television rcissLres of the fih'r'r, and later throtrgh vicleotape ancl DVD releases, this secminglv lir,ing incarnation of Kniglrt's painting of T rex-mispiaced ere, 3-fingcrecl h:rnd, and all-bat-

tling the inraginarv giant prehistoric gorilla, Kong, has become a

classic

motion-picturc seqllence. Indeed, to man.,'pcoplc, this drarnatic image of 'l re.t-hissing, biting, and su ishing its tail like sorne gigantic scrpent-constrttrtes the \.erv essence of this great theropod dinosaur (Fig. 21.6). Although r.ariations on Knight s 1906 n,ork continuecl to appear and can 1et be sccn cvcrt toclav in varions rredia- and rnerchandise-rel:rted incarnations, it n'as anotlrer painting, created sorre 2 decades latcr b1,thc same artist, that hacl equal, if not rrore profotind, effect on popular culture. Betn,een 1926 Donald

F.

Glut

:!1it

and I911. Knightu'as commissioned by.the Field l,,ltrser-rm of Natr-rral Histon (r-ron' the Field \,{useum) to paint :r series of iarge murals portrar.,ing life through tirnc for the exhibit hall n'here sorne of its vertebrate fossil specirnens il ere displavecl. Arrong this se ries-regarded b_v both Knight ancl his ach.nirers as his magnum opus-\\'as a Late Cretaceous scene, compieted bi' 1928 (N. Currrnings, personal cornrrunication 2006) and perliaps the most farrous dinosatrr pairrting er.'er executed, depicting'hrc nnoEcLurus confronlingTriceratops (Czerkas and Glut 1982). This time, holle','er, there n'ere inrportant cliffererrccs from the 1906 l.ersion of T. rex. Knight portraved T rex n,ith its ei,es correctlr,placed, its hancls bcaring Z rather than 3 fingers, and, propheticalll, it seens, ih bodr'hclcl in a horizontal posture ri'ith the stil1 too long tail off the grouncl (a second T rex inclir,idual in the backgrotrnd is proppecl np in the stand;rrcl subvertical pose still fashionable at the time). N,{oreover, the scenario l-rad:rlso altcrecl. No longcr tl-re rather lethargic animals dcpicted in 1906. this

Figure 21 .7. Late Cretaceous mural, painted by Charles R. Knight circa 1928 for the Field Museum of Natural History,

featuring the classic Tyra n n osa u rus versus Trice rato ps sce n a ri o, possibly the best known and influential of any T. rex life restorations. Courtesy the Field Museum, negative CK9T. Photo by Ron

Iesta.

Figure 21 .S Tyrannosau-

UM,.IK, TNQACED 3V Ol-lrRO',3 tvff .rAcgs T!"{g rraCCtC,JS TVRAN SFiCLT HfflDTD -.-

rus based on Knight's Field Museum mural as it appeared in a comic book adaptation of the 1940 \1

motion picture One Mil-

tl I

in the Reg'lar Fellers

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407

Figure 2'1 .9. Another Tyrannosaurus Dased on

Knight's Field Museum mural hlong with an Apatosaurus and caveman) AnnDArAd

th fna

,,.b," ..'4 tq 'of, ,'$1

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science fiction motion

picture, Dinosaurus! Co u rtesy U n ive rsa | - I nte rnational Prctures.

T\,rdrLnosaurtLs ttncl'liiceratops \\'ere painted activelv charging touarcl olre an-

otlier in ri'hat pronised to be a violent conflict (F-ig. 21.7). Like its earlier pre de cessor, Knight'sT1,rorr,rntourus verslls Triceratops rntrral had lasting imp:rct on the public. The Field NlttseLtm solcl postcarcls of the painting, rcprocluced first in black and ufiite and, in later rears, full color. Not onlr.rioulcl rcproductions of this p:rinting beconre the nortn itt books about cxtir-rct anirnals (e.g., Knight's orin book, Bef-ore the Dawn of Historr, 1935 ), largelv supplanting the 1906 image in popLrlaritr', but it also rlculcl also becorre the image of T. rex niost often copiecl bv other artists and adapted to other rredia. Knight's ncn'arrci rnore accuratc Tl rer u'as soon recognizable in a varietv of publications, including popular dinosaur books, nrainstre arn ni:rg:rzines, ancl comic books (fig. 2l.8), ancl also tvran-

ro\ilrrr\ portrlrrt'd irr rrrotior pitlrrres'Fig. 11.9, An.rong such publications r,iere the cl-reapli printecl ancl purchasecl pulp nr:rgazines, ri'hich n'ere nass-clistribr:ted perioclicals clisplalcd at novsst:rnds n'ith luricl covcrs during the 1930s and 19'10s. Prolific pulp artist J. Allen St. fohn aclaptecl Kr-right's Field N.,{useum Tyrannosaurus lo rnanv of his rnagazine paintings and dran,ings during thosc clccaclcs, primarih' illustrating the fantastic fiction scribed bv adventure author Edgar

Rice Burroughs, the creator of Tarzan and other larger-thanJife heroes. T'his tradition of copving Knight u'as later inherited bv such St. John succcssors as Frank Frazetta in the 1960s and bel'ond (Glut I980, 2001). Some publications eve n created their ori n chirncras bv melcling ele rncnts fronr cliffcrcnt Knight paintings to create a ncn'u,hole ir-r.rage. \\'. \\l Robinson's (1934) childrcn's book, for erample, corribinecl Irene Robinson's redrari'tt (arrd reversed) head of Knigiit's F'ield N'lr-rscunt'li'rdrLnoscurrus u'ith the bodv of the one paintecl for the Arnerican N{useurn, again n'ith 3-fingcred hands (Fig. 21.101. Surelr', the Field \{usennr mural affected popLrlar cultLrre trcrrtcnclorrslr, rrot onlv in its phvsical portraval olTvrannosaurus, but also in its Donald F Glut

Figure 21 10 lrene Robinson combined the head from Knight's Field Museum Tyrannosaurus mural with the body from his 1906 Tyrannosa u rus pa i nti ng, resu lting in this composite image far W. W. Robinson's child ren's book Anci e nt

Animals of America (1934). Courtesy the Ward Ritchie Press.

in the public consciousness that this dinosaur ancl Tricerdlops were natural enerries that encountered, probablv frecluentlr', one establislrn-rent

battle (see Happ this volurre). Inadvertcntlv, the mural also led to a tlrird depiction olTyrannosaurus, u'hich, like its Knight inspiration, woulcl also have considerable influence on popular cr,rlture. hi 1933-1934, Chicago pla1,ed host to tl-re \Vorld's Fair. Dubbed A Centurv of Progress, the 2-r'ear errent r;i as held on grounds located u,itl-rir-r lr'alking clistance of the Fielcl N,hise unr. Arnong tl-re attractions u'as the Sinclair Dinosaur Exhibit, featuring life-size, rrechanicall'"'moving, 3-dimensional recreations of the figures based dircctlv on Knight's murals. Designed bv P. C. Alen for the Sinclair Refinir-rg Companr'(Anonl'mous 1966) under the another

ir-r

Figure 21 11. Based directly on Knight's Field Museum mural, this lifesize mechanical Tyrannosaurus rex figure appeared in the Sinclair Dinosaur Exhibit at the 1933-1934 Chicago World's Fair (A Century

of Progress).

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A Century of Celebrity

409

Figure 21 .12. The Sinclair

Dinosaur Exhibit Tyran-

nosaurus as photo-

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technical consnlt:rtion of Barnurrr Bron'rr. this suite of Nlesozoic charactcrs inclLrclecl, of conrse, the poptrlar Trrannosauruslfriceratops conflontation (althorrgh lhe'l)rannosaurus :rgain sported a 3-fingcrccl liand). h'i profiie, the Sincl:rir ll rer reserrbled its Z-clirricnsional inspir:rtion at the Field N'ltrsettni (Fig. 21.11). Hou'ever, it n':rs a three-c1r-rarter-r'iet photogr:rph (f ig. 21. I2) of the Sinclair T1'rarnrosaurus th:rt soon began appearing in r':rrious \renucs, including a series of sourcrtir Irerrspapers atrcl postcards from the \\Iorld's Fair. Seen in this aspect, hori'ever, the figure took on its ou'n tmiqtre and odcl appearance that der.'iated in variorts n'avs from Klight's profile vieil. N{ost notablr,, thc dinosaur lookecl unr-tstt:rllr' iiide in the hips ancl hincl legs, rihereas the heacl, seen front this angle, assurnecl a horselike shape. Nlore significantlv, that photograph ',i as the basis for a painting executed bi' artist Jan-res E. Allen for The Sinclair l)inosatLr Book, a free booklet (Fig. 21.13) promoting the oil cornp:rur.and providing inforrration abor.rt dinosattrs, revievn'ed and perhaps autitorecl bv B:rrtlrtrr-t Brou.'rr in 1914 (see listing in Chure and Nllclntosh 1989). The book u.'as sent out to schools and other targeted attcliences, altd eventualli'became a highlv collectible itern. Like the Knight mur:rl that inspirecl it, t-tt-trnerous copies of Allens painting (nanus again correctlr didactr'l) nere also re414

Danald

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Glut

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prirrted in nuine rotrs otl-rer pLrblicatio's. Again TrrannosatLrus

*,,as

clepicted

abotrtto engage its b''.r,,'tradition.l foelTriceratoEs, in corrbat. Also, ii'itl-i Knight's versio', Alicn's renditior of T. rexbecame foclder for

as

nulrcr_

?ltl :lrt"tlt

including St. John, n,ho aclaptecl it to their ori,n needs (Ghrt

1980). oddly, some artists like St. John, portra'als of 7'. rex, basecr them on

i'

later illtrstrating their ou n'side-

Alle''s three-quar-ter-"rp..tprint'ie\\' ing, res'lting in distorteci clepictions that onr' superficiarrr, ,.r.,i'trt.a

Knight's original lateral vieu. (F'ie. 2l.14t.

Neri'artistic orT. ix,.s.,alrr ri ith 3 fi'gers ancl basecl either 'ariatiors on the Alien painting or thrce-cprrartcr-r ierr photogrrpl,, of the worlcl,s Fair rnodel, subseqtrertlr cleb.ted in othcr ri icieh, acce ssibre

Amorrg tllese urts tlrc J\'rarrrrr,,s.lrrrirs prcscrrlccl irr tlrc rrritl_19?0s 'e^les. aI Dirrosarrr park in Rapid Citr, SD, on: ol1-syite of such figures made bv local sculptor FllnrettA Sulliran (F-ig 21.i5). cercbratedirs thc first fuli-scale cli,,orr.,, figures e'er rrade i'the L.rnitecl States for perrranert clisplar, tire

Di'osatrr

Park Tt'rannudLLrLLE ard kin inrprcssecr ,'iiitnrs if orr' for tireir size, u hile at the sarle tirrc boosting the Black Ilills toLrrist tracle.

collectors'starrps

r,r'ere also issr,red

br,thc Sinciair Refini'g conpar^.,

r':irious children's books, pulp rragazines, ancl conric books (sce Gltrt l9g0) that boasted r.'ariatio.s on Allen's ri,ork. co.rtecl a.ronq

the m'riacl iter's

A Century of Celebrity

Figure 21 .13. James

E.

Allen's painting of Tyrannosaurus rex, based on th ree - q ua rte r-vi ew

ph

oto -

graphs of the Sinclair Dinosaur Exhibit figure, prepared for The Sinclair

Dinosaur Book. This image was widely seen during the 1930s through 1 9 50s. Cou rtesy Si ncla ir Refining Company.

Figure 2'i .14. J. Allen St. John based this

Tyrannosaurus rex on James E. Allen's threeq ua rte r-vi

ew pa i nti ng,

producing, for a pulp magazine (1942), a new si d e

-view i nterp retatio n

that only slightly resembled Knight's original. Cou

rtesy Zi ff- Dav is

Pu

b

-

lishing Company.

inspired bv r\llen's painting n'ere, along with other prehistoric anirnals, the rex figurines tFig. 31.16) first issued circa 19'17 br Sell Rite Giftri,are (SRG) of 1'Nen York (see Cain ancl Fredericks 1999). Prirriarilv sold in nruseunr gift shops :rncl througli rnail-orcler adr,ertisernents printed in rnagazines, such as the Anerican N4trsetrnr's Natttral History, tlrese grecriislr, perenniallv poptrlar TrrdrtrtosdrLrtLs figurcs constitutecl, fcrr nearlv a ciecade, r'irtuallr.'the onlr' J-dinrensional incarnations of the clino-

healr; bronzc-coated leadT.

sarrr a"'ailable to the public. Tlie.u'n'ere availablc in botl-r large and sn-rall sizes,

again possessing 3-fingcrecl hancls but assuming a rather sqr-rattv posturc. 'l'hese figures, lr.llich u'ere :rlso put out in ceranric ancl plastic lersiotts, cottlcl still be purchased in recent vears ancl arc highlv collectible toclar'. Into the earlr' 1950s, those 3 most inflnential images ol'f\rarntosaurus

rer-the 2 Knight paintings 412

Donald

F.

Glut

and the Ailen painting-continued to pen'ade

.."1

popular culture. Bv that time, Knight (1942,1946), as both artist and author, had alreadi'pnblisl-rcd nc\\'dcpictions of T\,rannos(tLLTLLS in the popular National Ceographic MagazirLe and his book Life through the Ages. Knight's illustration in the latter, in r,i,hich 27. rex indivicluals n,alk sicle bv sicle, or-rc crouched, both apparentlr,readl to strike at eacl-r other, seeninglv echoes Osborn's (1913) aborted plan to rrount both ANINH 973 and AN4NH 5027 as if about to fight frrr possessiou of a carcass. Althotrgh Knight clid not significantli'cler,iate frorn his r.nnr:rl in regarcls to thc phvsical look of TyrarLnosaurus, he no'nv portraved the anin-ral in conflict w'ith anotlrcr of its kind rather than n'itli the ubiquitous Triceratops. 'l'hese r,r'onderful pieces of art, portrar,i:ngT. rex as a considerabll,more acti'u'e anirnal than suggestecl br,the 1906 painting,',r,ere n'iclelr.seen ancl iirfluential in their on'n right. Hon'ever, these later irnagcs clid not affect the public as strongll as had Knrght's e:rrlier w'orks. Incleed, the nrain inflnence on the public conscionsness regarding li. rcLnnos(TurLLl r"er c:lnre neither frorri Krright nor anvone associated ri ith Sinclair, but frorn Yale Univcrsitl. During the 19'10s, ariist Rudoiph F. Zallingcr. w'ho had been taught about extinct life bv p:rleontologists Richard Sn'ann

Lull

ancl

Ajfred S. Ronrer,

n,as persuacled to p:rint an erpansir,'e

Figure 21 15. Full-scale statues of Tyra n nosa u rus and its traditional foe, Triceratops, based on

the works of both Knight anrl Allan <ettlnfod htr

Emmett A. Sullivan for permanent display at Dinosaur Park in Rapid City, SD. Courtesy Travel Drvision, South Dakota De-

partment of Highways.

rrural, non'

knon'n as thc Age of Reptiles, to adorn an ernptv lvall of the r-rnir,ersitr,'s Peabodr'\'ftrsetrrn of Natural Historr'. T\,rannosaurtLs u'ould be featured prornlnentlv in the Cretaceous portion of the ilork. Zallinger u,orked on this mur:rl for about 5 r'ears, finishing it in 1947 and garnering a Pulitzer Prize for his visuallr'stunning cfforts (see Scullv et al. 1990; Debtrs and Debus 2002).

413

Figure 21 .16. The largesize Tyrannosaurus rex

figure put out during the

late 1940s by sRG (Sell Rite Giftware) and sold mainly through museum gift shops. Courtesy Mike Fredericks and Prehistoric Times magazine.

Zallinger's versiorr of T. rex cler,iatecl significantli' fronr Knight's versiorrs irr a nunrber of u avs. Nlost notablr., it had a sotuen'hat triangular head

and a potbellt,. The forclimbs, tiren knon'n onlv frorn the hturertts, r'nere restored too sn-rall, as ri'otrld be er''iclenced br future discoveries (Carpenter and Srnith 2001; Lipkin ancl Carpenter this volurric). Also, the giant c:rrni\'orc \\';rs shori'n standing:rs if motionless, t:ril on the grottncl, disinterestecl in the ntrnrerous Cretaceous aninrals sttrrounding it (F ig. 2l. U). Neverthe1css, it u as Zailinger's T. rex that inparted the strongest influence on popular ctrlttrre during the late 19iOs ancl earlr, 1960s, nrostlv thanks to a peri-

ociical.

In

lc)51,

the ertrenrelr popular Life \Iagazine included a

re'u'crsc-image (or floppecl) full-color reproduction of the sn-rall prelin'rinarr.

rtrrtlr Zrrllirrger p:rirrletl of tlre r\gc oF Reptiles irr its Septe rrrber - issrre. l lre :rctual mural could not be photographecl because sorne of the rluseum's rrrorrnted dinosaur skeletons obstructecl the caner:r's vien'. Llfa N'LJgctzurc uas prorninentlv displaved on virtu:rlh' ever\, nen'sstancl in the L.lnitecl

rrvriaci re aciers brought Zallinger's u'ork, 'I\'ranrLosatLrLL.s inclucled, into their hones. Again, a n ork of art rapidlv shapecl ancu' thc pr-rblic's an'areness of T rer, ri ith reproductions of Zallinger's painting (or portions of it) being pLrblishecl e lseu he re . \'alc profe ssor Carl O. Dunbar in 1955 incltrclcd both the Tallingcr '.i". rer ancl Knight's 1906 original in the neri eclition of his classic tertbook, Historical Ceology. N'lore significantlr', in tcnrrs of :rffe ctins public arvarcncss, Zallinger's \'rannosaurtLs u'as the tenrplatc for cotrntless other incanr:rtioris of this dinosaur during the 1950s ancl I960s, nranv of tlrern in conric books such as Dell Publishing Conpanr"s Turol<, Son of S/one ancl ACIG s (American Coniics Group) Forbidden \\'orlds (fig. 21.18), sorretimes, as had hapirenecl u'ith Allen's painting, recortstructing the original im:rgc as vicri'ed frorr diffcrent perspectives. Zallinger's restoration is easilr recognizable in the forrr of pe rfortner Tim Sml th rl'e aring :rn rrncorrvirrcirr g'I\'ranrLoscttLrus costrune {F ig. 21.19) macle br the BLrd \\IestSt:rtes, so

414

Donald

F.

Glut

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r.ore riakeup shop in the notior-r picture Trrc Lancl LrnkrLow,,releasecr br Universal-hrternation:rl in 1957. other preliistoric creatures i1 the ,r'otioi picturc, as r.r'ell as o'erali set design, *.cre also basecl o' the yale r''rar (cllirt 198']1, 2001; Ber^ 2002t. pcrriaps nost siqrificantlr; it w.as the rnoclcl for the first comrre rciallr' ,,,.rr-pro.l,r"e.l cri,ruia,r, tor s, ri.hich appearecr r' 1956, courtes'of the N{iller (Fig. 2r.20) ancr Marr (Fig. 2r.21) iompanics

(clut

l9B0;

cai'arcl

Freclericks r999). These rrerpe'si'e sr'all prastic

fig'res, *'hich could be p.rchased in cli'c stores arcl other places thnt solcl tor''s, alloried chiidren to inr,ent their ori.n preiristoric scenarios s:rnte tirtre being eclucatecl.

- othcr pop.lar,

ri]iile

at tire

'h,rannosaurrts

often-reprodLrcecl ir'ages of ret r-tate also influe'cecl otrr c.lt.re (Debus a'cl Deli.s 2002), although ri,itho't tirc "of sarne irnpact as th.se of K'iglit, ,{ilc'. and zaringer. one these is the

Figure 21 .17. Tyrannosaurus rex dominates the Late

us po rti o n

mural completed in 1947

by artist Rudolph F. Zallinger {or yale University's Peabody Museum of Natural H istory. Cou rtesy Peabody Museum of Natural History, Yale University.

rto.ochrorrc rcstoratiorr br British artist \.ear.e parker during the 1950s, first macle a'ailablc as a series of postc:rrcls iss.ecl br the Britiir N{.seurrr

A Century of Celebrity

C retace o

of the Age of Reptiles

/1tF

Figure 21 .18. Zallinger's Ty ra n n osa u ru s i nspi red

STORIES

many copycat drawings annearinn in enmir

Af,PEOYE' &Y Tl{*

t*rarc* r$.lE

:".

books during the 1950s

ltutltoxl?f

through 1960s. This version is revised to a threent tArf6r ttiortt Cat trl:actt

American Comics Group.

-

j,i; -**-*t..-.;<''r

'')!.',.:, ,', ', Str*Y?,,^;:t.l.rr' I -tdil",i",".r,'r* .",f:;-\1 :;ir; .', 1 ;::. "ll.J"fit

L -=,:;Yqffi

i It (Natr-rral I{istorv) (non tlic NatLrral Iliston'\lirseLrm, London), and srrbse qtrentlr incluclccl br \\1. E. Sn inton (lc)62) in his poptrlar-science book Dil1os(trLrs.

Anothcr ricll-knonn inrage is thc painting nradc bl Czech:rrtist

Zclenek Btrrian in 1938, first pubiishecl decades l:rter br.Joseph August:r (1960) and then published ag:rin, slightlr re'n.isecl iAugusta 1912). .\lso rccciving nruch rlcclia attention ri'as the full-scale, totalli' r-rpriglrt, rnechanized (the lori'er jau rnovedl TlrautosaurrLs (Fig. 21.22) built

for tlie Sinclair Oil Corrpanr"s Dinoianci crhibit at the lc)6'1 Neri lbrk Worlcl's Firir bv the fonas Stuclios (Artonvurorts 1966; Cllut 1980; Debus :incl Debus 2002). A11 of the Sinclair clinosaur figtrres, like their 1930s prectrrsors. \\'ere nraclc ri'ith thc te chnical :rclvice of Barntrni Brou n shortlr before

416

Donald

F.

Glut

Tr*riweelM[Sm w,t{}*tr

fi$Y,q$!"$$

$fi$wtr $r$iT#

J*i;t{ Se#*iirY t il i t::::;:: :::,! ii!,r 1i:rti:l LLr":tl 1..:'t'. i !liUi 1: '_

his death in i963, and *'ith adclitional ontologist John H. Ostrorn. Scaled

'p

frorr

a

sc.lpt.re

irp.t

from peaboclr,\4trset', pale-

rr'corrpan'ori'er Louis pa'l l.rras,

this 7l rex subseqLrentl'took on its'adc or.r'n irnpressi'e lifc d.ring the 1960s, creatirg arrother l'a'e of T'rrlrltlosd.urLLE infl.erce o, poptrlar .i,1t,.,r.. constit.t_ ing rifiat todar' *o.ld be called an ideal photo op, trr. h.,g" fig.re becaurc a farniliar prop' ri'ith photographers posi,,g their lrun-ran ,,rn,tl, beforc tlie tou'ering giant. Aclr'ertisi'g agcncies .sed either photographs or art*.ork based on fonas'\\brld's Fair dinosaurs-u-rost often, tlie ,lr-irriornrrus rex_to pro_ rnote arrlthing from the Encv-clopedia Britannica (Fig. zr.27) to.raco bell

(Fig. 21 24). Sinclair pror.nire'tl'featured

its'*r,

'r. rex in sittclair ancJ the

Excitingwortd of Dinos(tLffs,,rriiclr,,.s ilr'stratecr *ith paintings that *,ere based on the Jonas statucs. 'l-he panrphlet *'as take. Lo,,re b, co-'ntiess'isi_ tors to the fair cluring 1964-1965 (l'ig. 21.25). plastic nodels of the .l rex solcl bl'r'ending rnachines at the fair and lat", i,r stores countr'r,,,icle soo' replacecJ in the older Alle'- and Zalli'ger-basecl fig.res made bi, SRG, \,Iiiler, ancl Ntlarr (l'-ig. 21.26). Additio'allr., copies of the r rex atrcrotler fig'res (also the snall-size protot'pe figtrres scufuted bi,Louis paul nJe clistrib'ted

Figure 2'1 .19. Tyrannosaurus rex awkwardly de

Cou

rnxstat-ue'e'e',-

Celebrity

redacio us

rtesy

Un

ive rsa | - I nter-

national Pictures.

tuallv carne to reside at the fiimous Lori,er cretaceous clinos:rnr tracksite near Glen Rose, TX' Fbr :r bricf tirre d,ri'g the i960s, the ir'age of T rex rriost seen b1'the public n'as that providecl br the |onas Studios. A Century of

p

Age of Reptiles mural.

fonas) among rnlrselllr)s and parks e'er ber.oncl LI S. borders (e.g., the calgart,zoo Prelristoric Park; see Glut iaS0t. 'l'he original \\brlcl s F'^i

T.

monstrates

behavior in this scene from The Land IJnknown. The prehistoric animals in this 1957 motion picture, as well as the flora, were based on imagery from Zallinger,s

417

Figure 21 .20. Waxy plas-

tic Tyrannosaurus rex hacad nn Tallinnar'< painting. Made by the Miller Company and originally issued in 1956, this and other prehistoilc animal figures in the Miller set constituted the first m ass- proo u ceo, co m me rcially sold toy dinosaurs. Cou rtesy M ike Fredericks and Prehistoric Times magazine.

Figure 21 .21. Made by the Marx Company, this Za | | i n ger- i n spi red, p lasti c Tyrannosaurus toy (known affectionately among collectors as the " potbe I I i ed Ty ra n n osa u rus rex") debuted in otme stores tn t956. Courtesy M i ke Fredericks

and Prehistoric Times magaztne.

418

Donald

F.

Glut

'l

g(

q,*

q

:*q:

Conseqtrentil', these varions versiorrs of T. rex inspired their share of nen,incarnations in the media and in merchandise. Although these T. rex restorations offerccl their ou,'n ar-ratomical inaccuracies, as pointed out br, Paul (1488t. ther rrere visuallv pon'erful, clranratic, ar-rcl kir-retic, ancl for those reasons strikingll' distinct fron-r tl-re rrore stoic lvorks preceding therrr. For such re:rsons, I (Glut 1972) selected the Parker T. rex as the clust jackct illLrstration for The Dinosattr Dictionary. The Parker, Burian, ancl fonas versions of Tlrannosdurus rex r,vere portraved ir-r the old-fashioned, inpossiblv upright-posed, tail-dragging modes.

Figure 21 .22. The Jonas Studios' towering Tyra nnosaurus rex mooet, scaled up from a sculpture by Louis Paul Jonas, tn a p hotog ra ph ta ke n sho rtl y

before bei ng transported from the Catskills to the 1964 New York World's Corporation.

A Century of Celebrity

419

THE MAGrc n00Rltrom The Tyrs.nt lfin{ Whri

is hsppoting? Did

dsud? No, it's somo&ing

Britannica

tht run xrdderdy alip tehind

a bugt

uu& rtraiger tiaro tb*t. Il'a a hr:ge

rrd bulgqy tyrrmo*aw-the biggeai.mat-eating dinooau thai srsr valked th* Earth! It wa* longer thrn a rcbool bus, Aid n'hsn it dood on itg hind leg& ita bcad leae ro high above the ground ilsi it eould lool over sall tillq. When n tyrannooaur, rometimer called f;rnrnroraxr?s rer, wat

llmgry, ii r*a hungry enough and big enougb to tat

even

anothc

dboeaur! lte jnwe were buge, and ita teolh wole sharp sith jaggod edg€6.

A:xl

wlranevu duq\ ocamed

1rl come ruddoniy or a cloud of tbe culr, all of tho other dimeaur* probahly skrtad runnhg, Tley tnew that a buge tyranno*er:r raigbt bc loonirg up nearby and *uiiisg oui the gunlighi. And when they wera clo*e eaough ta nr to oee ita long ahailo*, they rrare tod clo..l ao,

seamsd to hide the

?rlatb

Tynr*ww

Figure 21 .23. Advertise-

ment, which appeared in newspapers during the m i d - 9 60s, i ncorporati n g 1

the Jonas Studios' rnter-

pretation of Tyrannosaurus rex.

Not until relativel,v recent \''ears have life restorations of T rex been lurore al-latol-nicallv accurate, r,r,ith tl're bod,v posed horizontallv and taii off tl're grour-rcl. An'rong the first such restorations, if not the first, was the sculp-

ture bv Sr'lr,ia Nlassev (norv Czerkas) created during the late 1970s (Fig. 21.27) under tl-re gr-ridance of paleontologists RobertA. Long and Ralph E. Moh-rar (see Clut 1980, 19E2). Strbsequentlv, a ne\v breed of modern paleoartist-e.g., Robert T. Bakker, Stephcn A. Czerkas, Brian Franczak, John Cr,rrche, Mark Hallett, Douglas Her-rderson, Gregorv S. Paul-created rrrore correctly' restored versions of horv T. rex appeared and possibly beThese versions gradr-rallv replaced the older and outdated models,

l-ravccl.

not onlf in technical and popular publications, but also in merchandising (inch,rding a plethora of scientificalh accurate model assembly kit$ and other venues. Perhaps more than those of anv other paleoartist, Par-rl's (Fig. 21.28) ntrmerous life restorations of'I'. rex-dyn arnic as \\'ell as scientifically accur:ite -became the norrr, influencing a nen'generation of paleoartists, r.vhose draq'ings, paintings, and sculptures leave no question as to their rnain source of inspiration (see PaLrl I987). Without doubt, the single most impacting image on our culture by 'Iyrannosaurus re.x \\:as that portravecl in tl-re motion picture lurassic Park (1992) (Fig. 21.29), ll'hich',i,as based on the novel bv Michael Crichton. Procluccr-clirector Steven Spielberg raisccl the paradigrn for dinosaurs on screen br,brir-rging a consultant paleontologist, fohn R. Horner, onto the project. Horner $'orked closelv r,vith the special effects artists and iechrticians to enslrre tl-rat tl-re filn-r's Mesozoic anirnals rvere oresented rvith rea-

Donald E Glut

Sl'[email protected] TsC.e€'8rJS'Grl5: C-rs.a-

t,-: Oi€t

.4.: EilrO,l yaarg iq

Ftgure 21 .24. Another

Start your own authentic fossil $ollsctisn fmm TAC0 fALt

advertisement from the

nid-l960s based on the onas Stu d ios' saurus rex. J

Tyra n n o -

m$r**,"** sonable acclrrac\'. Thanks both to the lifelike anim'tronics clesignecr arcr built b' Stan winston and his tearn arcl to the proces, of .urrrp,,i.r-generated irragc^; the bar r'r'as sigrificantl'raised in nro'ie special effectf ri,rth the lurassic Parlr dirosatrrs seerrirglr,co'ring to life. Allou ing for a lust {e*,

rrinor cliscrepa'cies (nrostl'for clra'ratic efiect), tlre ,'o'ieirargerr, p"ul-

irispired T. rex arxl otfrer dinos,.rs airpearecl closer to ll{rat paleoiitologists belier.e abotrt di'osaurs tha' those of a'r. r'otion pict.re ,racle up 'tori rrrrtil llut lirrre. lurassic P,rrft u':rs an enormolls s.ccess

fro'

its first clal.of release arcl release. Ine',itablr,, 't'allr. the fihri iaunched a series of hit seq'els, as ri,eil as a pletrrora of authorized ancl irnitatior-r publications arcl merchandise. N,roreo'er, rts proneering special-effe cts u'o'k le d, either directh'or indirectlr; to s.cfr later *,ell-recei'ecl rvas e'e

seen

b' millio's of

ieri ers

i'

its

origi'al

A Century of Celebrity

Figure

2

rus rex

1

.25.Tyra n nosa u -

as

painted for the

pamphlet Sinclair and

the Exciting World of Dinosaurs, a souvenir item from the 1964 New York Woilds Fair. Courtesy Sinclair Refining Company.

421

Figure 21 .26. Miniature

reproduction of the Jonas Studios' Tyrannosaurus rex. These waxy plastic figures were originally sold in vending machines at the 1964-1965 New York World's Farr. Cou rtesy M i ke Fredericks

and Prehistoric Times magaztne.

Figure 21 .27. Sculpture by Sylvia Massey (now Czerkas) of Ty ra n nosa u -

rus rex made during the late 1970s, possibly the first modern life restoration of this dinosaur. Cou rtesy Sylvia Czerkas.

Photograph by Robin Robrn.

422

Donald E Glut

Ftdttr6

/ | )x

t lfa

ra
tion of Tyrannosaurus rex by the highly influential paleoartist Gregory S. Paul, prepared

for

his

book Predatory Dinosaurs of the World: A Complete Illustrated Guide (1988). Courtesy of Gregory S. Paul.

Figure 21 .29. Tyrannosaurus rex (life-size animatronics model by the Stan Winston studios), the first of its kind to be based on modern interpretations, as it appeared in lha nrnt tnr]hroakinn motion picture J u rassic Park (1992). Courtesy Universal Pictures and MCA. A Century of

Celebrity

423

l

ljjii.

tr"

rii:,li:

Figure 21 .30. The Tyran-

nosaurus rex skeleton (FMNH PR2081) known as 5ue, as mounted in 2000 at the Field Museum. Cnt rrfactt tho Fialr'l Alt t-

seum, negattve GN89677_47c. Photo by

lohn Weinstein.

424

projects as the 1999 Irnax motion picture T-Rex: Bctck to the Cretaceous, shon'n on enomrous screens in l-D, and the BBC s Wa//rlrLgwithDinosours (1999) and the Discoveri' Channel's When Dinosaurs Roarned Anrcrica (2001) telei'ision programs (see Berrl' 2002). As a resLrlt of ltLrassic Pcrft, r'ier,r'ers experienced, rnost of thern for the first time, a tnrer-to-realitl'idea of hon,T rex :rppe:rred in life (at least as far as it is understood todal), hou'the animal mav hat e molecl, arrcl ho',r' it could have behai'ecl. Thus, tl-ie public u'as alreadv primed to experier-rce the spectacular remains of the authentic anirnal ri'hen, after se'n,eral r'cars of ertensive legal ri'rangling and rredia coverage, Sue (e.g., see Latson ancl Donnan 2002)-the largest and best-preserr,ed, and one of the rrost complete, 'li rer Donald

F.

Glut

skeletor-rs

(I.'N{NH PR208i) r'et discor e red-lr as unle ilccl on tr{av

in the Field \'4useuur's grancl Stanle\ Field Hall rfig. 21.30).'l'his

2000, u'as the

17,

first tin're that an individual 'I\,rannosdtLrus spccimen :rrose to true celebritv status. Stre ir-nmediatelv became one of Clric:rgo's rnain tourist attractions. Thc ri orlcl :rncl its cultures are constauth changing. Also changing ovcr

tlie ccr-rttrn' after its discor,erf is T. rer. \\'ith the release of lurassic Park, ancl also thanks to the strbsequent imagerl it inspired, couplecl r,r'ith thc nori' global superstar notorietl of Sue, urost tomrer conceptions ofTyrannosar-Lrus rer (once so po\\,erfrll and scemingll, irnmutable) hai'e been erasecl. 'fhe ptrblic an,areness of this tvrant-lizard king has char-rgecl

fore.u'er.

I sincerelv th:rnk the following people ri.tro contributecl to, or in sorne other r.i,at'provided assistarce, rlaterials, or aclvice in, the r,,'riting of this chapter: Kenneth C:rrpenter, Den'u'er N'{useum of Nature & Science: Luis NI. Chiappe, Dinosaur Irrstitute, Natural Historv N.Iuseurr of Los Angele

s

Acknowledgments

Cotrntr'; Nina

Cumnings ancl Jerice Barrios, Photographv Departrnent, The Fielcl \'{riseurn; Alirn A. DebLrs, Hell Creek Creations; N{ike Frcclericks, Prelistoric Tinrcs magazinc; facques Cautl-rier, Pcabodv N4tiseum of Natural Historr; Yale Uni\rersit); Dean Hannotte; RobertA. Long; John S. \,lclntosh; Cregori'S. Paui; and :rlso the librarl; Nati-rral Historv Nilnseum of Los Angeles Countr'.

Anorrvrrcrrrs. 1910. The T),rannosattrus. lournal of the American N'Iuseun of Nat-

ural I'Iistort 10: 3-8.

-. -

i9t4. Tt'rtuutosaurus. P. 8679-8680 in Nlorse, I. 1,. ted.). Universal Stattdard Enct,clopedla. L.lniconr Publishers, \en York. 1966. A Creat Name in OiL Shrclair throtLgh !'ifit Years. F. \\l Dodge Cornparn'/\{cGrau Hill, Neu York.

Angnsta, J. 1960. Prel'Listoric Anirnals. Paul Hanilvu, London. 1972. Lifb before,\Iarz. American Fleritage Press, Neu'York. Baitr, E. C. l9;1. America belbre NIan. Viking Press, Ner.i York. -Bern', \'1. F. 2002. Tlrc Dirrcsaur Filntographt,. NlcFarland, Jefferson, NC. Bron,n, B. 1919, Hunting big ganie of other davs. Nafuonal Ceographic \,Iagazine 3 r=:401-429. 1934 'l'he Sinclair Dinosaur tsooft. Sirrclair Refining Companr'. D., Cair, ancl l"reclericks, NI. 1999. Dhtosaur Cctllectibles. Antique'frader Boor<s,

-

Norfolk.

\A.

Carpenter, K., and Snrith, NI. 2001. F'orelinrb osteologv and biomechanics of Tlrannosaurus rex.P.90 l16 in'lanke, D., ancl Carpenter, K. 1cds.1, ,\,Iesozoic Yertebrate Llfa. Indiana Llniversitl Press, Bloomington. Chrrrc, D. ]., ancl N'lcinbsh, J. S. 19E9. ABibliogrttpht of theDinosauria (,Exchtsite of the At'es1, 1677-1986. \'Iuseurrr of \Vestern Colorado, Paleontologv Serics L Colberi, Fl. H. 1945. Tlrc DinosatLr Boolr. Arnerican N.luseurn of Natural Historr,,

Neu York.

-. -

l9tl. Dinosaurs. Science Guide 70. American N'lLrseum of Natural Historv, Neu York. . 1961. DlnosarLrs:TlrcirDiscot'erl andTheir\\'ctrld. E. P Dutton, Neri York. 1980. AFossil-HtLnters Nofebooft. E. P Dutton. Neu York. 1983.

Dhnsaurs: Att lllustrated Histort.llarnrnoncl, \{apleri'ood, NJ.

A Century of Celebrity

References Cited

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Pliladelphia I8:

77

5-279.

Czerkas, S. N{., and Cllut, D. F. 1982. Dinosaurs, \'Iarnmoths and Cayemen: The Art of Charles R. Knight. E. P Dutton, Nen lbrk. Debtrs, A. A., and Debus, D. tr. 2002. Paleoimagert,: Tlrc Evoluticut of Dinosaurs ln Ar1. N4cFarland, Jefferson, NC.

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Scrapbook.'f Secarrcus, 1982.'fhe Neu Dinosaur Dictionarr,. The Citadel Press, Secauctrs, NJ. 2001. lurassic Classics. N{cFarland & Corripanl,, Jefferson, NC. -Colclner, O., ancl Turirer, G. E. 197t. Tlrc Makhtgof KingKong. A. S. Barnes, - Cranburr', N). NJ.

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Knight, C. R. 1935. Before the Dav,n of Historr. NIcGrarv-Hill Book Cornpany,, Nen York. 1912. Paracle of life through the ages. Natiotnl Ceographic Nlagazine 8I:

-

14t-184.

Lilb throush tlrc Ages. A. A. Knopf, Neu'York. On the forelinrb of ir carnir.orous dinosaur from the Beliv River -. Forrnatiorr of Alberta, and a nerr genus of Ceratopsia from the sarne hori-. zon, u'ith renarks on the integurrent of sone Cretaceous herbivorous dinosaurs. C)/tau,a Naturalist 2t-: I29-I35. Larson, P, arcl Donnan, K. 2002. Rex Appeal:'lhe Amazing Stort of Sue, the DinosatLr tlnt Changed Science, the Law, and NIy Life. Inr,'isible Cities Press, \{ontpelier, VT. \,ladsen, J H., ]r 1976. Alktsaurus fragilis: A Revised Osteologt. Utali Geological 19:16.

1914.

and \{iner:rl Survey Bulletin 109. \{arsh, O. C. 1877. Characters of the Oclontornithes, ri'ith notice of a ner,v allied gems. Arnerican lounrcl of Sciences, ser. l, 14: 85-87. Ner.r'man, B. H. 1970. Stance and gait in the flesh-eating TrrannosarLrus. Biological I oLLrnal of the Linnean Societt 2: I 19-123. Osborn, Fi. F. 1905. TyrannosatLrus and other Cretaceous carnivorous clinosaurs. Bulletin of the Americ an Musetnn of N atr-Lral History 2I: 259 265. 1906. Tlrd:tnosanLrus, llpper Cretaceous carnivorous dinosaur (second cornmrrrricartion). Bulletin ctf tlrc American Nluseurn of Natural Histort, 22:

-

-. -

I

t0-16t.

l9l 2 Crania of ?j'ra nnosaurus ancl A1/osourus . Nlemoirs of the Amer ican \,Iuseun of Natural Histort, n.s., l: l-J0. 1913 'I't'rannosauruy restoration and rnodel of the skeleton.BulletirLof the Arnerican Nluseunt ctf Natural Histort, 12: 9I-92. 1916. Skeletal adaptations of Ornitholestes, Struthiomintus, Tyranrtosaurus.

of the Arnerican Museum ctf Natural Histort'7i 761-77ir -. Bulletin 1917. 'I'he Origin and Et,cthttion of Life: On the'I'heort of Action, Reaction and lnteractiotl of Lnerg1,. Charles Scribner's Sons, Nerv York. -. Paul, G. S. 1987. The science and art ofrestoring the life appearance ofdinosaurs:rnd their relatives. P.4-19 in Czerk:rs, S. J., and Olson, E. C. (eds.).

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Dhnsaurs Past ttnd Presen.t, r'o1. l. \atrrr.r1 Hi:torr ,\hrseum of Los Angeles Cnrrrrtr. l,o. \rrgele'. 1988 Predatort' Dinosaurs ol tlrc \\|rld: -\ Corttplete llhLstrrtted Gttide. Sinron & Schuster, Neu York. -Reed. \\i N'I. 1930. Tlrc Earth Sam. H:rrcorrrt. Bracc, Neri York. for Rolrinson, \\l \\l l9l'+. Ancient Anintals of'Antcrica \\':rrd Ritcliie Press. l,os ,,\ngeles. SchLrchcrt, Cl., and Dunbar, C. O. 1937. Outlirrcs of Historical Geciogt. John \\/ilev & Sons, Noi \brk.

irrl

ed.

\'l,7allinger, R. F.. Hicker., 1,. J., and f)stronr, J. H. 1990. The Age of Reptiles: Tlrc Great Dinosaur l"hLral at Yale. Pcaboclv Nhrseurn of Natural I Iis-

ScLrllr,

torr',

Sllirton,

\eri Haven, CT. \\l E. 1962. I)irLostn-Lrs. -ltLrstees of the British N.,luseurn

(Natural FIrs-

torr'), London.

A Century of

Celebrity

427

INDEX

Achelosaurus,330 Acrocanthosaurus,24l, 382 Afrovenator,3S2

Coelophysis, 133, 142, 144,

152,

153, 154

Crocodylus porosus, 256

Albertosaurus,5T, 103, 104, 109-

111, 143, 145, 146, 149, 156, Daspletosaurus,55, 109, 110,233, 235, 238, 239, 284-286, 289, 234, 234, 236, 237, 238, 239, 291, 293, 299, 310, 311,316, 241, 287-289, 298, 310, 311, 325,326, 335-337; A. libra314, 319,323, 325-327,335337, D. torosus, 287, 292, 306, tus, 110, 306, 314, 319, 326; A.

megragracilis, 12; A. sarcoph- 314, 355 agus,289, 294, 296, 300, 308, Deinocheirus,3B2 Deinodon, 58, D. horridus, 57, 321 287 Alectrosaurus, 288, 309; A. olDeinonychus, 10, 148, 149, 166, seni,287,289 176, 382, D. antirrhopus, 272 Alioramus, 309, A. remotus, 287 Dilong, 143, 145, 146, 150, 287 Allosaurus, 107, 144, 147, 153, Dilophosaurus, 143, 144, 382; D 166, 310, 312, 314,316, 319, wetherilli, 374, 375 382,400,401, A. fragilis, 255, 259,261,289 Dinotyrannus,287, D. megragraAmargosaurus, 155 cilis, 12 Anchiceratops, 361 Diplodocus, 144, 373 Anchisaurus, 143 Dromaeosaurus albertensis, 280 Ankylosaurus,6, 337 Dryptosaurus,2BT, 387,400 Apatosaurus, 143, 144 Dynamosaurus imperiosus, 1, 6, Appalachiosaurus, 234, 287 57-59,79, 233,400 Archaeopteryx, 242, 31 B Aublysodon molnari, 2, 287 Edmontonia, 337 Aviatyrannis, 287 Edmontosaurus,20, 22, 35,42, 44, 382; E. annectens,72, Bambiraptor, 148, 149 104,298,355,364,384,389 Brachiosaurus,

143 155

Einosaurus,35S

Brachytrachelopan,

Carcharodontosaurus,

Eotyrannus, 148, E. lengi,2B7

384

Carnotaurus, 131, 133, 147, 149, 152, 158, 160, 315; C.

sastrei,

255 Centrosaurus,3S2

Ceratosaurus,5S, 142, 144, 153, 316,

377

Gallimimus, 145, Giganotosaurus,

149 147,

315,373-

375, 382

Gorgosaurus, l03, 104,

149,

Chasmosaurus, 330, 358; C. belli, 358, C. russelli,35B, C. irvenensis, 358, C. mariscalensis,

358 Chingkankousaurus,2BT

107-112,

114-116, 119, 122, 153, 168, 233-239, 241, 288,291,292, 294, 300, 310; G. lancensis, 108; G. libratus 255, 287, 2BB, 290, 355, 360, 370

Herrerasaurus ischigualastensis, 355, 377 429

Tyra n nosa u ri pus pi

Hesperornis, 247, 251

||

morei, 208,

249

lguanodon, 247

Tyrannosauropus, 208 Tyrannosaurus, 1, 2, 11, 30, 78,

Laelaps incrassatus, 384, 400

Liliensternus,

109, 131, 134, 143, 145-147, 149, 152,166,168, 170, 173,

144

75, 248, 286, 373, 425, 1

Maleevosaurus, 287

Manospondylus gigas, 1, 13, 37, 50,58 14, 20, 34, 103, 104, 107, 108, 115, 116, 234239, 309, 326, 338; N. Iancensis, 2, 83, 149, 110, 111, 112, 122,287

Nanotyrannus,

1 76, 178-1 82, B4-1 87, 212, 234-236, 239-242, 1

291-294, 296-298, 307, 381,

399-414,416,

1-3, 6,

8,9,

147,

69, 73, 83, 87, 93, 96,98, 1031 08, 1 0-1 7, 20-1 22, 24, 132, 133, 156-158, 160, 167, 1 69, 170, 192-195, 197-199,

ph

a

I

osau

Piatnizkysaurus,

147

Protoceratops, 333 Ricardoestes ia, 359

Saurolophus, 337 Scipionyx, 373 Shanshanosaurus, 287 Shantungosaurus, 337 S i a motyra n n us isa ne nsis, 287

leyT. rex, 16, Devil rex,

Sinraptor dongi, 241, 319, 355 Stokesosaurus, 287

Styracosaurus, 358 110,

237, 241, 382; T. bataar 103, 107, 111, 112, 233,234, 235,

239, 287, 288,370 Therizinosaurus, 382 Thescelosaurus, 20, 373, 379 Triceratops, 22, 44, 57, 63, 64, 78, 298, 327, 330, 331, 354-359, 361-365, 384, 389, 402, 407411,413

430

1

18,

Duffy,4, 26, 27, 38, 51, E D Cope, 5, 37; F-rex, 5,44, Fox,

Struthiomimus, 145, 147, 149, 315 Styg ive nato r mo I n a ri, 2

Troodon,151

1

254, 255, 257-278, 281-285, 287, 2BB, 294, 295, 299, 306, 309*31 1, 314, 316, 319, 323327, 329-331, 335, 337, 338, 340, 3s8-36s, 371, 372, 376, 377, 383, 384, 386, 388-390, 398-400, 402-41 6, 41 7-425, "007," 29; B-rex, 5,39, 122, Barney, 399; Barnum, 4, 31,' Black Beauty, 3, 16, 17, 51, 122, Bob, 39, 40, 96, Bowman, 4, 24, Bucky, 5,43,44, 51, 55, Crex, 5,40, County rex, 32, Cow-

Plateosaurus, 143, 241

Tarbosaurus, 10, 55, 104, 107,

1

201, 209, 210, 211, 213, 216, 227, 233, 238, 245, 247-250,

rus, 37 3 Pachyrhinosaurus, 330, 358 Parahesperornis, 242 Pentaceratops, 358 Pa chyce

11, 13, 15, 17, 18,

20-24, 28, 29, 31, 32, 34-37, 40-44,47, 50, 51, 55-60,63, 1

Ornithomimus, 57, 133, 145, 149, 152, O. grandis, 57

418,

bataar, 261, 306, 314, 319, 325, 326, 335, 337, T. rex, T.

4, 32, 35, Foxy Lady, 32, lvan, 5, 49, 51; Jane, 82, 83, 85, 86, 87, BB, 89, 110, 294, G-rex, 5,44; Hager rex, 3, 17, Henry, 122,' Huxley, 14, 15, 122; Monty, 4, 38, Mr. Zed, 23, Mr. Z, 23; Mud

Butte T. rex, 13, N-rex, 5, 44,' Ollie, 4, 35, 51, Otto, 5, 44, Peck's rex, 4, 33, 34, 51, 55, 74-76, 78, 79, 87, 122, Pete,4, 30, 31, 67, 69; Rex A, 35; Rex B,

4, 35,

Rex

C,4, 35, Samson, 4,

23, 51, 104, 105, 107, 108,

114,

115, 122, 295, Scotty,4, 28, 51; Stan, 4,9, 21, 22, 26, 36, 44,

194,195, 196, 198, 212,247, 289,295, Sfeven, 4, 29,30,38,Sue 3,9, 46, 51, 105,122,192,

21,44, 51, 55, 69, 774, 122, 196, 2BB, 425, Thomas, 5,47,48, 51; ker, 4, 34, 51, Triceratops-Alley T. rex, 35, Wankel rex, 3, 122; Wayne, 49; Wyrex, 5, 46, 47, 51, 55, 122, Z-rex 23,

:' '22,7. x,103, 104,105, ',, ^07, 108, 110, 111, 112, ": :i6, 122

17, 19, 20,

294,424, Tin18,

24,

Velociraptor, 148, 149, 333, 374, 375

Wintonopus, 224 Yangchuanosaurus, 316

lndex

431

ABOUT THE EDITORS

Peter Larson is founder and president of the Black I lills Institute of Geological Research in Hill Citv, SD. He and his staff have :rrnassed tlic largest rcsearch collection ol T. rex specinrens, incitrding "Stan," casts of n hich are seen ln mllseums arorrnd the uorld.

Kenneth Carpenter is the clinosaur paleontologist fbr the Denr,er N,lr-rseurrr of Natrrral Histort. He is autl-ror of F,ggs. Nests, andBrthyDinoscturs i2000), cclitor of 'l'lte Carnitorous DinosdlLrs (2005) andThe Armored DhtosatLrs (

2

00

1

), ancl co-ecl itor of T h utder -Li z ards : T he

S

aur

o

p o donrcrph

D ino

s

cnt r s

(riith Virginia Tiduc11,20(15) and l,Ieso:oic)lertebrate LilZ (nith Darrcr-r H. Tanke, 2{J0l). all n'ith hrcliarra LLiiversitr Press. He is also co-eclitor of Dinosaur Ststenntics; Dinosaur Eggs and Babies; and Tlrc Upper lurassic Nlorrison Fornrctiort.

,22

COLOPHON

'li'rannosaunls rcx, the'Ilrant Kiirg nas designccl at hrdiana LJnir.crsitr, Press br famison Cockerharn arrcl set in tr pe bv Nlike Kelsev at Inari Information Services. Junc Silar rias the projcct eclitor ancl Robert Sloan n'as tire sponsoring eclitor. J'he tert trpe is ltlectra, designccl br'\\'illianr,\. Dniggins in 1915, and the clisplav tr pe is F'rutiger, clesigned br Aclrian Frutiger in 1975. This book u'as printed br Sheridan Books, Inc.

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