Ammonites and the Other Cephalopods of the Pierre Seaway: Identification Guide (Fossils & Dinosaurs)

AMMONITES AND

THE OTHER CEPHALOPODS OF THE PmKKB SEAWAY IDENTIFICATION GUIDE

Authors Neal L. Larson Steven D. Jorgensen Robert A. Farrar Peter L. Larson

Photographer Ed Gerken

Exiteloceras

&I

Oxybeloceras

Hoploscaphites

Didymoceras

Placenticeras

Baculites

Pierre Seaway Ammonite Forms

OSCIEnCE BESS. Inc. T-ArlzoNI

© 1997Black Hills Institute of Geological Research, Inc.

ISBN 0-945005-25-3 (paper) ISBN

0-945005-34-2 (hardcover)

Library of Congress Catalog Number: �78211

Illustrations are by Dorothy Sigler Norton, NealL. Larson, and John R. Stacy. illustrations by John R. Stacy are courtesy of Dr. William Cobban.

Ed Gerken. are Dr. William Cobban, Dr. NeilLandman, and Dr. Karl Waage. All photographs are by Ed Gerken, except as noted. Book design by Neal L. Larson, Marion K. Zenker, Joe Small, and Ed Gerken. Computer Graphics by Marion Kathleen Zenker and

Content Specialists

Book transcribed by Marion K. Zenker. Cover design by Kim Ericsson. Production Manager was Amy Sorrell. Copyediting by Bernice Pettinato of Beehive Production Services. All Right<� Reserved. No part of this work may be reproduced by any mechanical, photographic, or electronic

process, or in the form of a phonographic recording,

nor may it be stored in a retrieval system, transmitted,

or otherwise copied for public or private use, without written permission of the authors.

Published by Geoscience Press, Inc.

P.O. Box 42948

Tucson, Arizona 85 33 7 2948 Printed in the United States of America 1098

765432

Publisher's Cataloging in Publication

(Prepared by Quality Boolcs, Inc.)

Ammonites and the other cephalopods of the Pierre Seaway : identification guide I NealL.Larson, [et al.]. p.cm.

Includes bibliographical references and index. ISBN0 94 -55 00 2 - 5-3 (paper) ISBN

0-945005-34-2 (hardcover)

l. Cephalopoda, Fossil. 2.·Paleontology-Cretaceous.

Paleontology-North America. Q E 806.C47

1997

I. Larson, Neal L. 564'.5'097

QBI%-40453

3.

T

book to

about the Western lnterior Cretaceous rocks

Dr. W. A. (Bill) Cobban, researcher,

be authors dedicate thi

and fossils, especially the Pierre Shale, than

geologist, and scientist with the U.S. Geologi­

any other individual in the world.

cal Survey in Denver, Colorado, since 1948.

Bill's interest in ammonites began as a high

school student collecting near Great Falls and

Yet it is not only ammonites ti·om the Western Interior that Bill has studied and de­ scribed. Ammonites from the Atlantic, Gulf,

Shelby, Montana, and continues to the present

and Pacific regions as well as ammonites from

day. Many well-deserved honors have been

Africa, South America, Europe, and Asia have

bestowed on Bill over the years. They include:

been objects of his research and subjects of his

the Meritorious Ser-

papers.

vice Award (1974)

wide-ranging research

and

the

Due to this

Distin­

and the excellence of

Service

his work, 1 2 species and

Award ( 1986), from

several genera of Ju­

guished

the U.S. Department

rassic and Cretaceous

of the lnterior; elec­

i n vertebrate fossils

tion as Fellow of the

have been named for

American Associa­

Bill by his colleagues

tion forlhe Advance­

in the United States,

ment

France, Japan, and Rus­

of

Science

sia.

(1982); the Distin­ guished Geologist

Bill has consis­

Award

tently and unselfishly

Pioneer

(1985)

from

the

shared his knowledge

Rocky

Mountain

with all interested col­

Section of the Soci­

lectors and researchers.

ety of Economic Pa­

In the process, he has

leontologists

and

taught skills and shared

Mineralogists; the

information that was not

Pa l e o n t o l o g i c a l

available at any univer­

Medal from the Pale­

sity anywhere in the

ontological Society

( 1985);

and

Dr.

William A.

the

(Bill)

Cobban

world. It is due, primarily, to Bill's

encour­

Raymond C. Moore Paleontology Medal

agement and assistance that this manuscript

awarded by the Society of Economic Paleon­

was attempted and finally completed. There­

tologists and Mineralogists (1990). Bill's approach of stratigraphy through

fore, on behalf of all the amateur, professional, and academic geologists and paleontologists

paleontology led to his organizing more than

who have been enriched by Bill's efforts. I say

70 different Cretaceous

thank you. Bill, this book is for you!

ammonite horizons

and his describing and naming over 100 new ammonite pecies from the Western Interior.

Dr. William Cobban probably knows more

NealL Larson, Vice Presidenl Black Hills Institute of Geological Rt>searclr. Inc. v

CONTENTS Foreword Preface Acknowledgments

::,;�� .

viii

lX

Xl

Introduction Geologic Setting

2

Chart: Position of the Pierre Shale

3

Extraterrestrial Phenomena

4

The Pierre Seaway

5

Maps of the Pierre Shale

6

Geology

10

Macrofossils

11

Chart: Ammonite Zones

12

Class Cephalopoda

14

Order Ammonoidea

L8

Family Baculitidae

19

Baculite Identification Guide

38

Family Collignoniceratidae

42

Family Desmoceratidae

44

Family Dip1omoceratidae

45

Family Nostoceratidae

49

Family Pachydiscidae

59

Family Placenticeratidae

62

Family Scaphitidae

71

Family Sphenodiscidae

91

Order Belemnitidea

93

Family Belemnitellidae

93

Order Nautiloidea

95

Family Nautilidae

96

Order Teuthidea

99

Family Kelaenidae

99

Family Trachyteuthidae

1 01

Macrofaunal List

103

Glossary

1 08

Bibliography

114

Index of Cephalopod Species

140

Charts of The Known Range of the Ammonite Species

144

Backword

146

About Black Hills Institute of Geological Research, Inc.

147

About The Black Hills Museum of Natural History

147

About The Authors

148

'

Fotmwotib ··.:..._

'"11e identification of ammonites and other 1 �ephalopod fossils has been a tremen­ dous, almost overwhelming challenge for sev­ eral reasons. First, there are numerous species

of cephalopods that appear to be very similar to each other. Many species have not yet been described, named, or properly placed among related forms. Second, the existing descrip­

tions are scattered through a vast array of literature, often in old, out-of-print publica­

tions, government agency or museum special publications, or otherwise not generally avail­ able. Also, there are relatively few experts to whom one may turn for help. Fossil cephalo­ pods have attracted human interest for centu­ ries and remain among the most popular fos­ sils today, yet there are few people who really know very much about them. This publication makes a quantum leap forward in solving some of these problems. It brings together, for the first time, the descrip­ tions and references for all of the known cepha­ lopod fossils representing a major geographi­ cal area and time span in North America, the Pierre Seaway that divided the continem dur­ ing the Cretaceous period. This work immedi­ ately solves the problem of the scattered litera­ tW'e by bringing these references and descrip­ tions together under one cover. However, it also contributes to solutions of the other two problems.

Having all recognized pecies in

one reference will greally facilitate the naming and description of yet unknown form . It will also make it possible for many people to be­ come familiar with and knowledgeable about this fa<;cinating group of organisms. Perhaps persons who formerly only admired these fos­ sils for their beauty will now be able to under­

nently qualified to write this book. They have worked closely with many if not most of the other authorities in the field; they have as­ sembled their own library of all of the pertinent literature; and, through their own extensive collections of fossil cephalopods and collabo­ ration with other collectors and collections, they have direct access to a major ponion of the best fossil cephalopod specimens avail­ able anywhere. Furthermore, these authors know how to help other people. They have not only spent innumerable hours trying to understand am­ monites and other fossil to increase their own knowledge, but they also invest an inordinate an1ounL of time and effort in helping others learn, ranging from elementary school chil­ dren and casually interested collectors to uni­ versity students, serious amateurs, and fellow professionals. From the ftrst day we met them, my wife and 1 were graciously offered their as istance in our understanding of ammonites. As a result, through the ensuing years, all the authors became close personal friends and are among our favorite colleagues. I and others from our university have taken numerous groups of students to the Black Hills Institute of Geological Research for tours and educa­ tion. While visiting the Black Hills Institute,

r have been frequently impressed at the num­ bers of chool children, people from the gen­ eral public, upper-level students, and profes­ sional paleontologists who come through their facility. Institute taffwillingly,eveneagerly, spend many hours explaining their favorite subject-fossils. This publication is an ex tenion, in print, of that outreach.

stand more about them and, hence, appreciate

James W. Grier, Professor ofZoology

them on an entirely new level.

North Dakota State Univer.�iry

The authors of this publication are among the few experts in the subject and are emiviii

Fargo, North Dakota

�

PREFACE·E��·�-�--

T

his book began as what appeared to be

suggested that we include the remaining six or

a fairly simple project in July of 1 993,

so cephalopods from the Pierre Seaway.

consolidating into one reference the descrip­

tive work on ammonites of the Pierre Shale.

I

consented, assuming it would be a three- or four-day project. Many months later we were

Yet even simple concepts can become incred­

still di covering and gathering new infonna­

ibly complex as you begin to explore them,

tion about these few

species.

One conse­

and thus complicate your work and your Life.

quence of this addition was an opportunity to

For example, I wanted to use everyday lan­

vi it with Dr. Cu11 Teichert (deceased), who

Part K, Treatise on the Mollusca 3

guage to describe the fossils in thi. book. It

completed

quickly became evident that using everyday

fo r the Geological Society of America in 1964.

language would often entail u ing 20 or more

Although Dr. Teichert was retired, in very

words instead of the one definitive scientific

poor health, and confined to a wheelchair, he

term. Consequently, when expedient, I cho e

managed to visit his old office at Harvard

to u e the scientific terms. That necessitated

University and rummage through his 30-year­

ary, containing definitions

old files to locate the Agassiz 1847 reference

compiling a glo

of the common morphological and geological

for the Family Nautilidae for us.

terms used in the cientifie description of cepha­

knowledge, this is the only publication about

Tn the

Nautilus that contains this reference in its

l op ods, for inclusion in the book.

To our

beginning, T planned to define the 50 or so

bibliob'Tapby. As we go to press, these remain­

described ammonite species and assumed the

ing cephalopod descriptions and discoveries

writing would rake one to three months. My

have become a major contribution to this work.

research, however, revealed nearly I 00 de­ scribed ammonite species. Who knew?

During the compiling of the information for this book, we were fortunate to have many

This project took hundreds of office hours,

cephalopod and mollusc collectors and re­

consuming a majority of Ed Gerken's, Robert

searchers from throughout North America visit

(Bob) Farrar's, M arion Zenker's, and my sched­

Black Hill ln. titute. Each person contributed

uled work hours. There were also many eve­

important information, ideas, and data to this

nings and weekend hours invested that kept

manu cript. Becau e of the discovery of so

me from my children and my wife, Brenda.

many undescribed species of cephalopods,

And, as the book grew, so did my family. Tn

many of which were uncovered while gather­

October of 1994, our daughter, Elisha, joined

ing the information in this book. it is clear that

her four brothers in our family.

within just a few years, it will need revision

Though that was not its purpose, my im­

and updating.

mersion in thi project has, at times, allowed

For me, the most interesting aspect of this

my mind to momentarily escape the le s pleac;­

project has been the research. Tt wac; when we

ant ordeals. related to a dino aur named "Sue,"

began to match the arrunonite descriptions

that have followed us over the pa<;t few years.

with the fossil ammonites, though, that the u·ue

After several years of research and writ­

purpose of this work became really clear. We

ing, with Bill Cobban's invaluable help, we

learned quickly not to accept all scientific

had nearly completed the text when Bob Farrar

literature as fact, because discrepancies were

lA

found in many scientific ammonite descrip­

the ammonite is a scaphite, baculite, or

tions.

placenticerac;, most people have had no avail­

Other consequences of our research

have been the discovery of more than a dozen

able source to consult for proper identifica­

new cephalopod species, the elimination of

tion.

several existing species names, and the serious

Although there are hundreds of scientific

questioning of at least one currently accepted

books and papers wriuen on the subject, very

ammonite genus.

few arc written for the amateur, or even the

The purpose of this work was to assemble

museum curator, that can help them make

descriptions of the more common ammonites

accurate and scientific identification of their

into one consolidated reference, as well as to

collections.

combine scattered source material, and create

This book was written with the help and

a comprehensive, bibliographic and faunal

advice of the top ammonite experts in this

listing for the Western Interior Pierre Seaway.

country. They read, reviewed, and commented

Not all of the ammonites are herein described,

on this manuscript throughout its many stages,

because after nearly ISO years of collecting

from its creation to what you now hold. We

and research on the cephalopods from the

sincerely hope that this book will serve as an

Pierre Seaway, there are still many yet to be

indispensable identification guide for you.

defined.

The specimens depicted in this book were

The number of cephalopod specimens that

primarily from two sources: The U.S. Geo­

have been collected from the Pierre Shale and

logical Survey (USGS), Denver, Colorado,

dispersed throughout the world must be stag­

and the Black Hills Institute of Geological

gering. Most popular localities for collecting

Research, Inc. (Bl-ll), Hill City, South Dakota.

invertebrate. within the Pierre Shale produce

The USGS specimens are designated by

thousands of ammonite specimens every year.

USNM numbers and are patt of the U.S. Na­

With the number of collectors who visit these

tional Museum's permanent collection. Tbey

localities annually and the fact that many of the

were photographed with the permission and

sites have been collected continuously for more

under the supervision of Dr. W. A. Cobban of

than I 00 years, you can begin to understand

the USGS. The Black Hills Institute of Geo­

why these ammonites are not rare, even though

logical Research specimens are designated by

good ammonites might be uncommon. Nearly every rock and mineral collection

BHl numbers a11d are part of that permanent collection. Some of these specimens may be

in this country, not to mention the amateur and

seen on exhibit at the Black Hills Museum of

museum fossil collections, have at least one

Natural History in HiU City, South Dakota.

ammonite from the Pierre Shale among their

The remaining photographs of specimens were

specimens. Most of these specimens are

used with the permi sion of the owner and are

misidentified or remain unlabeled. Whether

acknowledged with the photos. This project wac; fun and very educational for the authors. Our hope is that collectors and researcher

will also find it interesting and

helpful for many years to come. The authors welcome any suggestions, thoughts, or criti­ Anak/inoceras n. sp.

Drawing by John R. Stacy

cisms of this book that may help make it more enjoyable, useful, or readable.

Neal L. Larson X

ll Te thank Dr. W. A. (Bill) Cobban, Dr. \1 \1 Neil Landman, and Dr. Karl Waage

GeorgeBurg,Dr. Ray A., Dorothy, andJapheth

for reviewing this manuscript and adding their

Boyce, Earl Brockelsby (deceased), Donely

valuable sugge Lions and comment

to the

Darnell. Barry Brown, Ed and Ava Cole,

text. Thanks also to Dorothy Sigler Norton

Howard (Bud) Ehrle, Bruce Ellison, Steve

Special thanks go to David Anderson,

and John Stacy for their artwork and Ed Gerken

Haire, Rev. Harry Heidt, Lonnie Holsworth

for his wonderful photography and his many

( deceased), James A .

hours on the computer formatting. typing, and

Jorgensen. John Larson, Neal C . and Gert

inserting the image .

Larson. Jim Michaud, Doroth y and Richard

In addition. the authors thank the U.S.

Honert, D a l l a s

Norton, Wayne Olson (deceased), Don Par­

Geological Survey for its long-term commit­

sons, Paul and Winifred Reutter (both de­

ment to the study ofthe North American West­

cca ed), Bill and Jean Roberts (both deceased).

ern Interior Pierre Seaway during the Ia t 140-

Jordan Sawdo, Jim Schoon, Dean and Donna

plus years.

Their findings have been made

Talty, Tom Trask, Leon Theisen, Kurt Triscori,

public in papers. bulletin . monograph , and

Tom Wooden. Helen Wright, and AI (de­

maps. Of this e teemed group of geologists.

ceased) andJune Zeitner. These are the people

none has been more helpful than Dr. William

who opened the doors, showed us the way,

(Bill) Cobban of the U.S. Geological Sur\'ey,

donated specimens for our research, supported

who for over 20 year. has shared his knowl­

our interest, and even our obsession with

edge, wi dom. and friendship with us. Other

the e wonderful creatures.

scientists who un elfishly bared their rime.

In addition. we thank all the ranchers who

advice, and wi dom are: Dr. Karl Waage of the

opened their lands to us and others for collect­

Yale Peabody Mu eum, New Haven. Con­

ing. as well as the numerous collectors who

necticut: Dr.

eil Landman of the American

have shared their finds with us.

arural Hi tory. New York; Dr.

Thanks also to Joe Small, editor of the

Karl Hirsch (deceased) of the University of

Fossil News. a monthly journal of amateur

Colorado atBoulder: Dr. WilliamJame (Jim)

paleontology, for all of his help on the layout

Kennedy of University of Oxford in England:

and suggestion to improve readability.

Museum of

and Dr. Jim and Joyce Grier from North Da­ kota State University in Fargo.

A very pecial thank you to Brenda Larson, \\ho put up with Neal through all of the hours, weeks. and year

that went into this book,

when he could often think of nothing else. And fmally, particular thanks is given to Marion Zenker, who typed this manuscript many. many times. created numerous dia­

grams and drawing�. and also suffered the erratic temperaments of the authors with grace. Thank you! NealL Larson

Roben A. Farrar

Steven D. Jorgensen Peter L Larson

xi

INTKODUCTIJiJN :•::-

Placenticeras intercalare

(after Meek, 1876)

T

he Pierre Shale and its macrofauna have been studied for more than 150 years. F. B.

Meek collected, figured. and described many of the common invertebrate fossils. His

1876 monograph.

InvenebraJe Cretaceous and Teniary Fossils of the Upper Missnuri

Country, is the mo t comprehensive reference for Pierre Shale invertebrate fos sils to date ,

.

Since that time, many others have published works on the cephalopods, gastropods. pelet:y­ pods, arthropods, and other invertebrates. A large variety of vertebrates has a Iso been reported.

Despite scores of publications on the geology and fauna, many specimens await description

.

The rapid erosion of the shale expo es large numbers of fos its each year. and the continued coUe cting of this material will undoubtedly yield new taxa.

GEoLOGIC :'{ SEJim, �a .

D

·'

�

uring the Campanian and Maastrichtian

water (200-300m), possibly the deepest part

Stages of the Late Cretaceou!>,the West­

of the seaway. The eastern Colorado and west­

em Interior epicontinental ea covered an elon­

ern

gated,asymmetrical trough. The westernbound­

water depths of 100-200m. The easternplat­

Kansas ''hingeline" represent outer shelf

ary of this Cretaceous basin extended from west­

form,in eastern Kansas, Nebraska, and Iowa,

ern Arizona h t rough western Utah,central Idaho.

probably was rarely covered by more than 100

western Montana,and north into the Canadian

meters of water at maximum transgression.

Arctic. The tectonically active Sevier Orogenic

Gill and Cobban (1966a) state that at Red Bird, Wyoming, the

Bell contributed enormous quan­

Gammon

Ferruginous and Sharon Springs

titie. of coar.e-grained, clastic

Members of the Pierre Shale ap­

material to the rapidly subsiding

pear to have been deposited in

westernportion of the ba.in.

le s than 200m of water, while

The easternedge of the basin

sub equent members of the

can be traced to we.tern Minne­ sota anc.l Iowa. The fine-grained

Pierre Shale were deposited in

sediment,low rates of deposition,

more than 200m of water. Fora­

and thin su·atigraphic units indi­

miniferal data at Red Bird, Wyo­

cate a limited sediment source on

ming, indicate a water depth

the easternside of the basin. The

ranging from 120m to les. than 15m (Mello, 1969).

north end of the seaway wa open

Gill and Cobban ( 1973) pre­

to the boreal region of northern Canada and Greenland,while the

sent a detailed discussion of the

south end of the seaway was con­

depositional environments of the Pierre Shale and its equivalents

nected to the Texas Gulf Coast

in the

area. Marine vertebrates and in­

Dakotas, Wyoming. and

Montana. Across this vast area,

vertebrates migrated into and out of the Western lnterior from both

the lithologies range from

of these regions.

nonmarine and nearshore arena­ ceous clastics ro fine-grained il­

Various re earchers have in­ vestigated the po

lite-montmorillonite marine

·ible depth of

shales. Bentonite beds,of vary-

the epicontinental seaway,in gen­ eral,and the Pierre Seaway spe­ cifically. Kauffman (1977) states

Didymoceras nebrascense DraWing by John R. Stacy

ing thicknesses, can be

traced

aero s hundreds,and sometimes thousand ,of square miles in this

that the shallow-water marine, marginal marine, and coastal-plain coar e­

area. These bentonites are valuable correlation

grajned clastics,deposited on the western shore­

markers in the Western Interior because the tiny

line,were deposie l d in water less than 50m deep.

sanidine and zircon cry tals,which occur in the

ln western Colorado. New Mexico.and parts

bentonites, have been used o l radiometrically

of eastern Utah, h l e Mancos and Lewi

Shale

date the variou members of the Pierre Shale.

appear to have been deposited in deep. quiet

2

i\mmnniti'S and til� ntlrer Ct!!phalnpods ofth� Pierr� S�away

PosiTION oF THE PIERRE SHALE IN GEOLOGIC TIME

ERA

PERIOD

EPOCH

- 66.5 MY

0 N 0

00 ;:;l 0

�

u

00

��5

�

�

� �

u

FORMATION

r---"T"

u �

STAGE

71.5

�� �

z � :z

�

�

�

�

< = 00

:;g \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \

� � � �

�

=.c

82MY

References:

Dyman, T. S.: Mete\\ether. E. A: Molenaar. C. M.; Obrado\ich.J. D.: Wt:imer, R. 1.: and Bryant, W. A

Geological Society of America 1983.

1994.

Figurt!: Farrar, N. Larson, 11)94 Computer Graphic: M. Zenker

3

'

.

ExTKATERRESTKI�� E

vcr since I 980,when Louis and Walter Alvarezstunned the scien tific commu­

ni ty wi h t h t eir as teroid impact theory,a search

even older Sharon Springs Member. It appears that the Pierre Shale,below the unconformity a t the base of the Crow Creek Member ,has been

has been underway to locate the crater blasted

more deeply eroded in sou h t eastern Sou h t Da­

hy the exta r terrestrial body hypothesized to have

kota

impacted the Earth at the end of the Cretaceous.

westernareas.

bringing to an end the reign of the dinosaurs and the ammoni tes. Two impac t features that

(nearer the

Manson site) than in more

Another possible e ffect of the impact and resul it ng tsunami is the absence of Didymoceras

appear o t have been

srevensoni and any

created a t or near the

fossil molluscan or

end of the

Creta­

oh t er distinguishable

ceous include the

fo sils throughout the

Didymoceras stevensoni Range Zone

Chicxulub structure, of the

entire

Yucatan Pen­

insula on the Gulf of Mexico, and

in Norh t Dakota. South

th e

Dakota, or Nebraska.

Manson s rt ucture in

As far away as West­

Iowa. The Chicxulub

ern

Sou th

Dakota

structure is thought to

there is a noticeable

more closely coin­

absence of fauna be­

cide with the Creta­ ccous-TeJ lt ary (K-T)

boundary (64.4 MYA),

Comet Hyakutake Photo by 0. Richard Norton. Science Graph1cs

while the Manson s rt ucture is older (73.8

MYA)

the Didy­ moceras nehrascense

tween Range

Zone and the

Exriloceras jenneyi Range Zone on the north­

and occurred during the it me of the deposition

em. eastern. and southern flanks of the Black

of the Didymoceras srevensoni Range Zone of

Hill . The tsunami could have left the seaway

the Pierre Shale. lze tr et al. ( 1993)reported tha t

uninhabitable or it may have destroyed all evi­

the base of h t e

dence of life in the e area . However,the fauna

Crow Creek Member of the

Pierre Shale in eastern Sou h t Dako ta contain

is remarkably n i tact and abundant on the wes ­ t

shocked quartz grains,presumably derived from

emand northwestern flanks of the Black Hills,

the Manson impact ejec ta,based on radiomet­

indicating that there must have been orne struc­

ric data and proximity. Possible evidence of the erosive force of a

u t re that pro tected or shielded them from the force o f the t unarnl. I t i. geological events such as this that make

tsunami produced by h t e Manson impact is the regional, angular unconformity present at the

the investigations of the geology and paleontol­

base of the Crow Creek Member of the Pierre

ogy of the Pierre Shale in teresting,challenging.

Shale. ln Lyman County. South Dakota, the

and exciting. With continued research into the

unconformity occurs be w t een the Crow Creek

Manson impact structure and associated geol­ ogy,a more informed and clearer picture will

Member and the underlying Gregory Member. Fru h t er eas , t in Yankton County. South Dakota. erosion hao; completely removed h t e Gregory

develop that may prove the incredible force of this impact.

Member and the unconformity lie on top of the 4

Ammonites and the uther Cephalopods ufthe Piure Seawa)

-

Tnt:

PIERRE .�E�WA� ·.

T

hroughout the Cretaceous Period, t h e Western i nterior Seaway made a series of transgressions and regressions into the West­ �m Interior Basin of North America Even though the seaway wac; open to the Arctic Ocean, there i no evidence in the fo it record to sug­ gest a cold environmenL A wide variety of life was supported by three major ecological areas within the seaway-a cool northern boreal zone, a mild central zone, and a warm southern tethian Lone. Ammonite diversity seemed to reach its peak within the temperate zones of the seaway which extended from what is pre ent-day northern New Mexico through southern Canada. Many differ­ ent types of cephalopods nourished in these waters, but heteromorph ammonites predomi­ nated. Ocean warming and cooling plus rapid

nuctuations of oxygen content and salinity caused changes i n the lithologic deposition and life forms in the seaway. Many extinctions occurred during these episodes, but new forms of ammo­ nites arrived and Oourished. The new forms probably came most often from the Gulf Coast, but some probably also arrived via the northern corridor to Greenland or to the Arctic Ocean. The Baculires obtusus Zone, of middle Campanian age, coincides with the maximum expanse of the seaway. Many transgression and regres ion followed the Baculites obtusus transgression. The seaway never again covered such a large area, and it tin ally succumbed to the continental uplift and eli appeared ncar the end of the Maastrichtian.

Oxybeloceras sp. DraWing by John R. Stacy

EXPLANATIO

OF SUBSEQUE T PIERRE

SEAWAY MAPS

Plotting the shoreline of an ancient seaway is difficull and often impreci e work. We are grateful that Dr. William Cobban undertook to plot the west coast of thi seaway. using ammo­ nite zones from New Mexico to Canada as hi guides. His calculation probably follow quite closely the western shoreline of the Pierre Sea­ way at its greatest incursion. Glaciation and

few mall outcrops remain. however, suggesting that the eastern edge of the seaway may have extended well into present-day low a and Minneota. Judging from the foraminifera and an ammonite found in glacial till, the northern boundary was probably open to what is now Greenland. Exposures of marine outcrops in the 'orthwest Territory and the Yukon inclicate that

erosion have nearly obliterated all traces of the seaway' northern and eastern boundaries. A

at its greate t extent the Pierre Seaway probably opened to the Arctic Ocean to the north. 5

PIERRE SHALE MAR£NE AGE OUTCROPS

Present Day North America

Referenccs:

U. S. Geolo11ical Survey stale geolo gi cal ma ps : Canadian Gcolog�cal Survey Provancial geological map� & map of !he Arctic: American

Association of Petroleum Geologists

6

tate geological highway �I�apS.

Ammonites and the mlrer Cephalopods of rluo Pierre Seawa-.

F1gure: N. Larson, 1994

Computer graphiCS: M. Zenker

WESTERN INTERIOR PIERRE SEAWAY OF NORTH AMERICA Regressions and Transgressions during Upper Cretaceous Period

I "1'-

'- '1 I I 1;. I

Baculires obuma time

appro:timatel} 80 MYA

References.

Cohb:m. W.A.: Men:v.c:tbcr. E. A.: Fouch. I. D.: and ObradoHch.J. 0.. 1994.

Figure: N. Larson, 1994 Computer graphics: M. Zenker 7

WESTERN INTERIOR PIERRE SEAWAY OF NORTH AMERICA Regressions and Transgressions during Upper Cretaceous Period

Baculires compressus time

approximaLely 73 MYA

References: Cohban. W. A.; Merewelher. E. A.: Fouch, T. D.: and Obradovich. J.D.. 1994.

!!

Ammonites 011d Lhe other Cephalopods of rlre Pierre Seaway

Figure: N. Larson, 1994 Computer graphics: M. Zenker

WES TERN lNTERlOR PIERRE SEAWAY OF NORTH AMERICA Regressions and Transgressions during Upper Cretaceous Period

I I I

'

/'-,..

I I

{,

\

\

I

I I I

I

I

-,..I

I

I

I I

Baculites clinolobaws time approximately 69 MYA

References: Cobban, W. A.; Merev.elher, E. A.: Fouch. T. D.; and Obradovich, J. 0., 199�.

Figure: N. Larson, 1994 Computer graphics: M. Zenker

9

T

h e Pie r e S hal eis l ar gely compo sed o f

Uppe r Cr etaceous roc k u nits of the W es tern

da rk-gray to blac kma rin es hale ran ging

n I t erior S eaway and h elped d ef ine 26di fere nt

from l ess h t an I ,000to 10,000f tin h t ic kne s .

ammo nit era nge zon es in h t e P ier e r Shal eand

The pre sence o fs lty, i andy . a nd calcar eou

a ge- equival ent roc ks o t da te. The r eco gnitio nof

u ni tswit hin h t ela rgely dar k- gray Pi erre Shal e ha . be en h t e bas is of formal m ember nam es,

u nravelin g h t e history and h t e st rat igrap hy of the

thes e zo ne s bas be en of ma jor m i po rtance n i

suc has h t e Gammon F erru gi nou s M emb er (i n­

P ierr e Shal e. Glenn R. Scot t a nd W lliam i A .

cludin g h te

Cobba n mapp ed h t e se ammoni te zones alo ng

Groa t Sands o t ne

B ed ), Sha ro n

Sp ri ngs M embe r, Mitten Blac k Shale M ember,

h t e Fro nt Ra nge from

Red Bi d r Sil y t Memb er ,and Mo num ent Hill and

no rthward to h t e Wyom ingbo rd er.

Kara B en o t nit ci M embe rs o f h t e B ac l k Hill ar ea ; and h t e Sha ro n Spri ngs, Gr ego ry , C o rw Cr eek, Dc Grey , Vcre ndry e, V ri gi n Cree k, Mobrid ge, and M issiouri

Du rin g Campan a i n and Maa st rich ita ntim es fluc tua tion si n sea l ev el caus ed cha ngesin the w e et rn (and pr esu rnably ea c;te m)mar gi nso fh te

El k Bu tte M embe rs o f the

Riv er vall ey o f Sou th D a kota.

out b centra l Colorado

seaway. Th ewest er nma rgi no fth e Pi erre Shal e i

of ten inter o t n gued wi th t err estrial d epo si st .

Nears hor e sands o t n eunit sin no rthern Colorado

O ne uch ter re str ai l '"ton gu e"i st he Campa nian

hav e giv en ris e o t suc h nam esa

Jud ti h Riv er Format o i n of cent ral Mon at na a nd

Hy gi ene, T erry .

La rm i er , Roc ky Rid ge,and Richard Sa nd sto ne Memb er so ft he P ier re S hal e. Themonoto ny of th e sh al eu nit sis bro ken by many hor izon s o f calca reou sand iro nsto ne co ncre iton . Ma ny of th ese co ncr etio ns contain fos sil s.

Du e to the

Alberta. D ur n i gla te Campani an itme, h t e sea­ way a ga in expa nd ed w estd e p o si in t gt be Bcarpaw Shal e of Mon a t na and

A berta l .

The m a rin e

B earpaw Shale i a time equ valent i o f theupp er part o fth e Pi err e Shal e. A st he Cr etaceous drew

di fficul y t reco gn zi in gs ructur t ein t he shal e,t he

to a c o l se, the P ier re Seaway be ga n to re c ed e

co nc e r tio nhor izons wi thdis tinc tiv efaunal a c;­

eas w t a rd y l a nd then sou h t eas w t ardly. Th e Pierr e

sembla ge s hav e been ex tremely m i por a t nt o t geolo gistswor kin gin the Pi err e S hale. Throu gh­

S eaway di sapp ea red by middl e Maa strich ita n tim e.

out the W est ern n I ter o i r, the o f siliz ed r ema ins

The Pie rre Shale r ests con formably o t di s­

of ammon ties ar eso numerous and wid espr ead,

co nfo rmably upon h t e Niobrara Forma iton, a

and thei rmorp holo gical diff erenc es so disc ern ­

y ellow o t gray wea therin glim estone o rc hal k.

bl i e, tha tby u sin g them, geolo gis tsand paleon­

Depos ited co nformably o n o t p of h t e Pi erre

o t lo gis tsca n separa teve ry h t ic k homo geneou

Shale i

the Fox Hills Fo rma iton,wh c i h isc hi efly

roc kunits into small er bio tra tigrap bic zo nes .

.ands o t neand sa ndy ·hal e h t at was depos ited at

T hes el m i i et d zo nes enable geolo gi ts o t locate

the ed ge o fth e seaway a si r ec ed ed from we t o t

h t em se lv es at h t esa n1epoint n i geolo gic tim e

east. Th eforma tio n si tim e rta nsgressiv e so that

acro ss grea t di stances

(sometime s m o re tha n

, 1 000mi apar t). D r. W lil a i m A. Cobban in­ v ested mor e t ha n 40 y ear . wor ki ng with the

ltl

llmmnt�itP< ,,,

h t etop of t he P ierr e Shal e in Wyomin g i sold er than th e o t p of th e P ier e r Shal e i nc entral Sou h t Da ko a t .

,,,,. nthl'r rf'nlurlnnnd< nfthe Pierrt' .'it'Ok'tt\

:-=-

l'1ACKOFOSsms

�he Pierre Shale is probably best known .1 for its remarkably well-preserved ammo­

abundant lobsters and crabs. Several localities in South Dakota produce small crabs in concre­

nites. These include the planispiral Placenticeras

tions (Dakoticancer). One site yields crabs and

.tnd a host of heteromorph forms such as

lobsters (Linuparus) in concretions and loose in

Baculites, Hoploscaphites, Jeletzkytes, 0\}'beloceras, Solenoceras, Exiteloceras, and Didymoceras. There are also a number of lesser

the shale. A concretion horizon in the Bearpaw

known and several known but undescribed am­

lobsters of the genera Hoploparia, Palaeo­ nephrops, and Linuparus. Other i nvertebrates

monites.

In certain horizons, ammonites are

Shale ( equivalent of the upper part of the Pienc Shale) in central Montana produces abundant

round in great numbers and often in an excellent

occasionally recovered include bryozoans, bra­

,tate of preservation with iridescent, nacreous

chiopods, and corals.

Eutrephoceras, probably

Vertebrate fossils are found throughout the

the ancestor of the present-day chambered nau­

Pierre Shale. They are preserved both in concre­

,hell material intact.

u l us, occurs abundantly in the later portions of

the Pierre Shale.

Other cephalopods. such as

11elemnites and squids, are rare.

Gastropods,

pelecypods, and scaphopods are abundant and .tre commonly well preserved. Although these

tions and loose in the shale.

Vertebrates are

common only in the Sharon Springs Member near the base of the formation.

Most of the

specimens found in this horizon are poorly pre­ served; consequently, excavation, preparation,

mollusks are typically best preserved in calcar­

and description of this fauna have been limited.

eous concretions, they also occur loose in the

Interest in this fauna has increased and extensive

,hale.

collecting projects have begun.

Echinoderms are rare m

the Pierre Shale, al­

rhough several echinoid genera and a brittle-star have been noted.

The

echinoids usually occur in concretions but have also

,-,

�/

::iffllfiilLt;2� C �· ��

ral History has been particularly active i n researc h i n g t h i s fauna. Documented vertebrates

Pteranodon ingens

heen found loose in the 'hale.

Ken Carpenter of the Denver Museum ofNatu-

(after Eaton 191 0)

One locality in

include mosasaurs, ple­ s i osaurs,

pterosaurs,

birds, ntrtles, and fish. Dinosaurs arc one of the

South Dakota has produced complete ophiaroids in compacted shale

more unusual faunal elements ofthe Pierre Shale,

units.

probably representingcarcasses that were washed

Althropods are uncommon in the Pierre

out to ea.

Shale; however. limited areas have produced

II

AMMONITE ZONES OF THE WESTERN Pierre Shale and Age

-g Stage •t: "' c..

�

u

�Vl <

Ammonite Zone ·

AGE (!

.lllArP"Ar

12

South Dakora South Dako1a Soulh DakOla Wyoming wr::,ung Montana S u F lanJ. Northern Flank ol Black Holl> Black Hillf6 Mossoun

(I

Jeletzkyu:> dorfi

..."'

?:

.3

�

Baculites elicui

� Low er

unnarnetl

>hale (pan)

Baclllitrs reesidei Baculites ctmeutus

....

@

;:J

;:J

8.

0..

u

�

u

0::: t.IJ c.. c..

�ITVTT •

73.35 ± 0.39

Raculites cnmpre>sus

�JJiiJl

c:

Didymoceras clll!yennen.te

74.76 ± 0.72

Exite/oceras jenneyi

� Mcm�r (pan)

Did ymncercu nebra.vcense Baculite.f scotri

:s

;:J z

�

< u

"'

:0

-o

�

(4

Baculites puplexu>

Baculites asperifonnis Baculites oblltSILf Baculites

..."' :l: 0

..J

Baculites

80.54 ± 0.55

sp. ("'l

sp. (•muoihl

Scaplrites hippocrepif Scaplrites lppocrepif u

m n

Member Siloy

-

MiiiCil

a; J:!

Member

Shale Member

O=mon r..._,.. \l<mb
.;::

Gregory Mernba"

f-Sharon Spring, Member

t

- ?-

:,:

.. J:!

"' u

�

.;::

ldembcr

Noolnnl I'm

(part)

Greg«y Memba

f--

-

Mitten Bllk'k

l'embina Member

Shal<

McmbtT

f-Sharun

Spring<> Member

Niolnrafm

2) Obradovich. J. D. 1993

g

3) The Baculites redwtcus zone may be lhe same a e as the Baculites gregoryen�is zone [Cohban written communication 1994]

4) Zone contains an early and late form of Baculites perplexus and is separated by Baculires gilbeni. 5) Gill and Cobban 1 972a

12

6) Cobban and Larson

7) Gill and Cobban 1965

Ammonite,f and the othu Cephulopnd.f ofthe Piurt' Seawav

Middle part

u

Niobrar• Formation (part)

Gommoo �

ilJliiiOI!I part)

...

c- ? -

81.71 ± 0.34 N- R

DeGrey .!! .2 Mcmbc:r "'

Crow Creel. Member

Black

f--

Scaplrires hippoaepis I

I) Gill and Cobban 1966a

c: Re
Sharon Springs Member

Bacu/ues mcleami

Shale

Member

u

MHlo
Baculites sp. (;moulh 'J'OC•esl

u

�t �-----

Memher

Baculites gregoryenm

-?-

l)eGrey

u

Unnamed �

J:!

Stloy

_ ? _

1-- � - ? ;;

Re
Ill

Baculitrs redwrcu.f

IUU Bentomtic: Member

lo>Aoc:r

Didymoceras stevemoni

z

f-onum e nt M

part

Member

Shale

I

u

Uppc::r

Odanah

Member

Member

ab>cn t

l:

\'em�

Unnamed

O>:ldron M:h (�

f--

unconfonrut)

I,..,�

Nebrnsk•

Unnamed Shale Mcmba

Member

1..,-.�� --;:;;;o;;o -

7 1 .3 ± 0.5

BaCIIIitesjerueni

Vl

-

Mobridge

Formation

Baculites baculus

m

.,. _

Creek

Raculites 11randis

Enslcm

�!i l Hill)o Formmon

Formauoo upper unnamed Fox Hill> shale

69.42 ± 0.37

Baculite> dirw/oha111;

Rij'J

Hell

North Dakota

(part)

INTERIOR PIERRE SEAWAY Equivalent Rock Units i\..tl� l , <1h Central

lJrUl

Furt Col

Member

Mcmlx!'r Salt

t-- ?-

./"

Lake Creek

- Member _

:.

-

I- ? -

Pueblo

Terry Ss.

Zone

tr:LGtlben 1897)

and

Sharon

Springs

Transnioo Memb
(pan)

u

5

Ru.�ty Zone


(part)

Member

Trans11Hlll Mcmba

Niobrara Formation (part)

Hardin

Formation

(part)

ContrJ.!

II

(11)

Eastend Eastend

Formation

Formation

Fox Hm< Fonnation

llearpaw

Bearpaw

Shale

Shale

unnamed Member

I- ? -

Lewis Shale

Pine

Bearpaw

Ridge

Shale

Sandstone

Odanah

Member

0.

5

·tf�

Wlllallled

0.

" marine e ... shale 0 "'2 " ,.

II �� 0

::.;

�

�

Ruck

>

�

"

�

River

FUnnalioo

Oldman

�

Formation

JudJth

"'

Formation

!l

River

� P:!rlmt:m Sandstone

Millwood

0:: Member Prutman

l'arlcman Sandstone

"

]

SaMstone

Foremost Fonnation

�

Steele

shale

�

� ....... .2 o... s.

� v

Teapot

Member

r,.-...

Sharon Sprin�

Southern

Shale

S:mdl.tooe

Buck

r---

Al'cfo

Mrutitoba

Albt:rta

Saskatchewan

Fox llills

Fonnation

Lewis

Tongue

c

"

e

&

! .E .>< 0

I"

8) Gill, Cobban and Schultz I972a I I ) Cobban 1955

(9

Hell Creek

Lance Formation

Lewis Shale

Fruitland

'

.><

Niobrara Farmalion (pwt)

Central

- -?--

tp

., r---

shale

Shale

Montana

Montana

Larnmie110.

Laoc< Fm.

Kirkland

-

Garfield Formation

Teepee

shale

Member

Niobmm �vnnation

-?-

Mount

-

s:mdstonc

rcc�11

Salt C

Fonnatioo

Hygiene ;;;

Member

llunter

Canyon Fonnation

and

�

wr:�ng

Fox Hms Fm.


Member

w2':n�g (pun)

I-

� "* � � � r--... t: " sa.nd.�mne

Sandstone

Sharon

Northeastern

shale

-;;

Springs

(

Unnam:d

Me m ber

Member

Colorndo

Rook Cli��·SanJuan�

//

Weskan

Utah Eastern

Sandstone

1:¥::

0::

New Mexico

Colomdo

Trinidad

sandslonc and shale

Unnamed

..

tinfR·

Transmoo

��

Creek \1ember

Colomdo

Culorndo

� .J::

"'

�"

:E.

-�"'

�"" � ";; S1raySs. ] ----.; ;---"' ..

t:!.

u

E 0

i: !;' :l ., :E.

0

Mancos

Shale

(pan)

Shale

-8 � = _,...

-

.bole

f--FishlOOlh

Claggen

Claggell

Shale

Shale

Member

Pakowki Shale

-

-

- - -

Eagle

Eagle

Sandstone Sand<Jone (pan) (pan)

Milk River

Sandstone

Member

N1obrard. Frn

shale

9) Gill and Cobban 1973

Ganunon

ft.mlgJIIOU.'J

Sand�tone

1---

12) Cobban Lwritten communication 1994]

*Ss is abbreviation for Sandstone

Pembina

(pan}

(pUil)

I 0) Gill,

Merewelher, and Cobban

13) McNeil and Caldwell 1981

1970

Illustration: W. Cobban and N. Larson.

Computer graphics: M. Zenker, 1996. 13

C

ephalopoda ar ethe larg est, mo st nt i eUi­

g ent ,and mo st a gil er epr esentat ivesof

th e Phylu m Mollu <.:a that ha veever il ved . Ce pha­ lopods (mean n j g h ead -foot )ha ve ext ernal or ­ gan s cons sting i of a di st nct i head with two la g re

eye .,a b eak.a f unn el,and a cir cle of ann. w th i

a pa ri ofpr eh ensil et entac les (o ften wi h t hooks

or .uck er s)around the mout h. They al so ha vea la g r e body ca vity that prot ects th einternal or ­ gan s such a sth e h erut.k d i n ey s, gills , sto ma ch, int est n i es, re producti ve organ s, rad ula, and a man tl e ca vity. All cephalopod s (w tih the ex cep­ tion of so me octopi )ha ve eith er an ext ernal sh ell

Cross Section of Chambered Nautilus

wh ere th eani mal nhab i ti sth e last cha mb er,or an

Illustration by D.S. Norton

int ernal sh ell that i slinearly cha mb er ed or re ­

ilis play fer vent courtshi p exhlb tions. i Extin ct

duc ed n i siz e. Ce phalo pod s ha ve b een di vid ed into two gro up s, Tetrabranc ruata (fou r-gillcd , ) wh ci h in ­ cl ud es th e ext ernal shell ed nautiloid and a m­ monoid , and th e Dibran chiata

(two-g lil ed),

cephalo pods ate a variety of food. Th es maller ty peswer ep ir mar ly i p ankton l emers,but as with all pr edatory an ima ls, they w ere o pportunisti c f eed ers, eating whate ver they w er eabl e to catch.

which incl ud es sq uid s.octo pi,and th eb ele m­

Th ediet of extant cephalopods consist sof plank­

nit e sor cuttl e fish . Shell ed ce pha o l pods ar eu ed

ton , <.:r ustacean s,and fi sh a sw ell a sother cepha ­

by b o i stratigrapher sto .e parate the t ruck Pal eo ­

lopod ..

zo ci and Mesozoi crock unit sinto small er , more

r eptil es, crusta ceans.and oth er <.:ephalo pods .

They , in tum, arc f ed upon by tish ,

Shell ed

con ci se bio stratigraphi c ,wn es. Mod ern ce pha ­

cephalo pod s ha ve th e a hility to

lopod sarc mo st ab undant in th e shallow (l ess

achi eve neutral b uoyan cy in wat er d ueto th eir

than I 00 m) coa stal ar eas of th e world s' o ceans.

cha mb er ed sh ell swh ich can b e fill ed w tih ga sor

Many c ephalopod s, as do other pr edator s, ha ve a high er metabol ci rate than most oth er n i vertebrat es. This enables th emto b e qu ick, ni mbl e swi mmer sthat can stalk pr ey and co m­

ca meral lf uid sto control the d epth to which th e ani mal sinks or ri ses. Nautilus ( Lat n i : nautilos mean s sa lor), i th e only

sur viving, external y l

sh ell ed ce phalo pod, even a p pear s in

mod ern

p et ewith f i shes fo r food. Th e mo llu scan f oot of

fiction. n I Ju les Vcme's l 870booktit lcd Twenry

th e sh elled and .o tf-bodied

Thousand Leagues Under the Sea, Vernena med

cephalo pod s ha s

Nautilus, an d ga ve it the

b een moditi ed nto i a funne l h ( yponorn e)that can

ills sub marine , th e

be pointed in d fi f er ent dir e ction..

chara ct eristi cso fthi sre markabl e ce phalopod.

Wh en th e

cephalopod takes wat er into the mant leca vity, ti

Sh elled c ephalo pod s do not ha ve ink sac s

then expe sl th ewat er o ut through th efunnel and

b ecaus eth ey ha vea protecti ve,hard , ext ernal,

by jet pro pul sion mo vesits elf in th eoppos ti e

chitinous sh ell. Leh man

dir ect o i n fro mthe dir ection in whi ch th e f unn el

( 196 9 )d d i d es cr be i what they belie ved to b eink

( 1967) and

Wet zel

sacs n i two dif fer ent a m monites. Land man and

point s. Cephalopod brain s ar e so w ell de veloped

oth ers,how e ver ,dispute thi s p ( ersonal co mmu­

h ! at th ey ar e capabl eof earn l ing and taking care

ni cat o i n, 19 9 4). Th e of , t externa l-bod ed i ce pha­

of th ei 1· young . 1 -l

Many typ es of cephalopod s

o l pod sty pi cal y l ha ve n i k sa cs that enabl ethe m

Ammonites Ollll the other Ct'phalopods of the Pierre Seaway

Ct A..,.., Ct t'ttAI.OI'ODA

"·-).

to hide from their enemies behind a self-gener­

Scaphites grew involute coils until nearly adult,

ated ink cloud. The earliest known fossil ink

when the living chamber became retracted from

sacs are from the Jurassic. Many modem squid,

the earlier whorls. Exiteloceras was planispiral,

culllefishcs, and octopi have the ability to make

but it is still considered a heteromorph because

rapid color changes with the aid of muscle­

the whorls do not come into contact. Baculites

controlled pigment-bearing cells. This muscle­

began as a coiled ammonitclla, but straightened

controlled color changing is unique to cephalo­

after only about one and one-half coils. All three

pods.

genera were probably relatively mobile and their

CEPHALOPOD EcoLoG�

A

neutral buoyancy would have allowed them to actively feed throughout the water column.

Solenoceras began as a typical coiled ssuming that the main body of the Pierre

Seaway ranged in depth from 15 to 200

arnmonitella and grew a straight limb that inex­

plicably turned 180° and grew back in the direc­

meters, a vast array of ecological niches existed.

tion of the ammonitella with the body chamber

Animal life in the sea would have evolved to

in contact alongside the pbragmocone.

inhabit the benthic or pelagic cnviTons of the

Oxybeloceras ammonitella was followed by one

seaway as best suited their particular needs or

and one-half to two open spiral whorls that

The

was easiest for them to exploit. It is possible that

retracted into a straight to slightly curved limb.

the highly buoyant, free-swimmingjuveniles of

Later ontogenetic stages of Oxybeloceras look

all cephalopod genera were dispersed by the

similar to those of Solenoceras. Depending on

surface currents of the seaway while they drifted

the species, the ammonitella of Didymoceras

with the other planktonic organisms living in the

was followed by straight or curved limbs that

sea. This would help explain how species were

changed to tight or loose helical coils and ended

able to quickly disperse across the seaway. Sub­

with a J-shaped or U-shaped body chamber.

adults probably migrated to the portion of the

Schooling behavior is almost always de­

water column that they would occupy as adults.

picted for Baculites as analogous to the modern

Juvenile cephalopods probably ate other

squid. There is no direct evidence for this be­

planktonic-sized organisms, both plant and ani­

havior in any of these genera.

mal. and were likewise consumed by larger

large numbers of individuals of some species

creatures.

All growth stages of cephalopods

However, the

would indicate vast schools, not only when spawning, but also when feeding opportunities presented themselves.

� v

Didymoceras, Oxy­

beloceras, and Solenoceras were not fast swim­ mers: consequently, they doubtless were benthic feeder , eating plankton, carrion, as well as

Evolute Involute Illustration by D.S. Norton

were subject to predation by marine reptiles.

larger. s low-moving or careless marine animals. Cretaceous nautiloids probably lived in the same shallow-water depths as the ammonites. Extant nautili are nocturnal and only move up in

birds. fish. crabs. squid, and larger ammonites.

the water column at night to feed. They prefer to

Menabites. Menuites. Pachydiscus and Placenticeras) con­

stay at deeper depths during daytin1e hours.

The planispiral genera (e.g .

.

,

tinued with their involute and evolute. overlap­

probably to avoid predators. In reef-slope habi­ tats, the nautilus is a bottom-dwelling or benthic

ping whorls lhroughom their lifetimes. but the

cavenger and predator. Modem adult nautili

heleromorphschanged their hape dramatically.

tend to tay in the same area they inhabited as 15

Cl AS� CL: FIIAI .Of'ODA

�':�

newborns and juveniles; most travel no more

the survival of the species. One male can im­

than 30 krn from their home territory.

Long­

pregnate several females, but the female must

tem1 habitats appear to be at about300 m deep or

wait out the gestation period imposed by nature

less in the water column, which limits damage to

before producing young. ln mature nautili, the male generally has a

the shell by flooding or implosion. Squids and octopi arc rapid swimmers using

slightly larger shell and a heavier visceral mass.

their tentacles or arms for catching and holding

Male nautilus shells are larger in diameter and

their prey. They are both benthic and pelagic

wider than those of the mature female.

dwellers that search the reefs and shallow seas

probable that sexual maturity is not reached until

for their food. These animals propel themselves

maximum growth is achieved. Some giant am­

by taking water into the mantle cavity and expel­

monites, however, surely must have attained

ling it through an organ called the funnel.

sexual maturity long before they reached maxi­

Preserved remains of fossil nautiloids are

It is

mum size. Another interesting phenomenon of the ex­

not nearly as abundant as those of the ammo­ This suggests that they were primarily

tant nautilus is that the female lays compara­

ably "schooled" as evidenced by the abundance

though nautilus has the ability to reproduce for

of their remains. The population densities of the

several years, i t is probably not capable of explo­

nautilus were never as large or diverse as the

sive reproduction.

ammonites. This is probably a result of their

reason Eutrephoceras has never been found in

nites.

solitary animals, whereas the ammo nites prob­

tively few eggs each year.

Therefore, even

That may be the primary

reproductive success, with a few large eggs laid

large enough numbers to be designated a Range

every year by the female. Due to the fine preser­

Zone fossil within the Pierre Seaway.

vation of cephalopods and other fauna through­

For more than 100 years, paleontologists

out the Pierre Seaway, we have been able to

assumed that ammonites were sexuaUy dimor­

learn a great deal about their habitat.

phic, but it was not until the 1950s and 1960s that

DIMORPHISM

I

IN

discoveries were made that support this assump­

CEr:ftALOP.ODS

tion. One of the most exciting finds regarding ammonite sexual dimorphism was tl1e discovery

t is important to the paleontologist and bio­ su·atigrapher to determine the gender of

cephalopods. If male and female differences are not identified, there may be twice as many spe­ cies described as actually Lived because each gender may have dramatically different body size and shell morphology. The extant

Nautilus (a living relative of

these ancient cephalopods) have been

tudied

for more than I 00 years and produce some interesting observations. Collections of speci­ mens of Nautilus from New Guinea and the Philippine Islands show that the percentage of males in the mature population ranges from 69% to 92%. This is a surprisingly large percentage of males because it is the female that guarantees

16

by Lehman i n 1 966 of preserved egg sacs i n the fossilized remains of a Jurassic ammonite macroconch. The macroconch or larger conch of ammonites has since been widely accepted as being the shell of the female. Shell size seems to be the most striking difference between the sexes i n ammonites. In the invertebrate world, and in nearly all molus.ks, females are ordinarily larger than males.

There are often strikingly

different male and female morphological forms. ln scaphit:ids, the macroconch (female) has a slight swelling just above the umbilicus in the body chamber.

This has been suggested by

Landman and others as the possible placement site of a brood chamber.

ln the Family

Scaphitidae, the macroconch body chamber in­ creases gradually in width but rapidly i n height.

Amnwnitel and the mher Cephalopods of the Pierre Seaway

�

CLA�� Ct f'tt '\1 <>I'ODA

However, in the microconch, the body chamber

and a lack of natural predators made conditions

;rows slowly in both height and width, but never

favorable for cephalopods to reproduce rapidly

.mains the ma<;s of the macroconch. Tubercle

because their fossil record indicates great numbers

placement, flank and venter width, and ribbing

of these animals inhabited the Pierre Seaway.

all factors when attempting to establish

If we are to accurately describe these marine

'110rphorypes. In the phows of the scaphitids. we

animals, it is important to correctly identify the

'how microconchs and macroconcbs together so

gender of individual specimens. So how does a

.uc

rhat the reader can see the extreme differences.

paleontologist determine the sex of a cephalo­

The fossil record indicates that the male-to­

pod? By studying not only the mature shells but

female ratio in ammonites was probably the

also the phragrnocones, and by keeping faunas

opposite of the extant

Nautilus.

thus providing

the number offemales necessary to make explo­ ,r ve

reproduction possible.

It is also believed

of specific areas separate for study, we may be able w distinguish sexual dimorphism from spe­ cie

differentiation.

lt is already known that

that because of the small ammonitella size in

suture patterns, shell shape, and shell growth are

..tmmonites, they may have laid hundreds or

similar i n immature forms of a species, regard­

thousands of eggs in a year, which may explain

less of gender. Studying all of these elements in

the great numbers of ammonites found pre­

concert w i l l help the scientist assign an accurate

-�rved in the Western Interior Pierre Seaway.

gender to a long-dead animal and ensure a more

Evidently, water temperature, salinity, depth.

accurate depiction of the species.

Anaklinoceras gordiale Drawing by John R. Stacy

17

A

mmonoidea is an extinct order of cepha­ lopods mat flourished in the later Pa­

leozoic and throughout the Mesozoic Era. bur

ammonite hell and visceral mass to maintain a particular orientation in the water (center o f buoyancy and center o f mass).

Period at the same time as the dinosaurs. They

AJJ ammonite began life as an embryonic shell stage called an ammonitella, which had a

are related to the extant and extinct forms of

diameter of approximately 1 mm and consisted

squid, octopi, and nautiloids.

of a coiled protoconch, one or more septa, and a

became extinct at the end of the Cretaceous

Their soft parte;

include a large head, arms or tentacles. and

body chamber.

internal organs. They also had ajaw mechanism

able to disperse throughout the seaway, along

These tiny animals were then

that includes the aptychus, which is occasionally

with other plankton, imply by movement of the

preserved. Anunooite shell shapes may be tightly

water currents until they became large enough to

or loosely coiled in a plane, tightly or loosely

colonize an area of the sea.

helically coiled, slightly curved, irregularly

The abundance and diversity of the Ammonoidea from rhe Pierre Shale bas pro­

curved, or straight. The Ammonoidea are characterized by an

vided collectors and cientists with an extensive

external, multichambered shell with septa that

ammonite fauna that is not yet completely de­

are connected by a tube structure called a

scribed. To date, there are nine known ammo­

siphuncle. The septa, at their intersection with

nite families, 28 described genera, and almost

the external shell, form complex, angular suture

100 described pecies from this single geologic

panerns. The septa and external

hell are com­

posed of alternating aragonite and conchiolin,

formation and its marine equivalents in the West­ ern Interior.

nacreous shell. Thi layered shell structure gave

The abundance and variety of beteromorph

the thin shell of the ammonite prut of its strength

ammonites makes rhis ancient seaway unique in

to withstand cru hing under extreme hydrostatic

the world. The excellent preservation of many

pressure.

ofthe ammonites and other ancient sea life in the

Septa created chambers in the

phragmocone that enabled these cephalopods to

Pierre Shale is rarely equaled but never sur­

maintain neutral bouyancy. Arrangcmentofthe

passed, if the geographic extent of the formation

buoyant hard shell and soft tissues enabled rhe

is considered.

The

living

ammonitella

[Dashed line indicates phragmocone position]

Ammonitella

Illustrations by D.S. Norton

cross section

18

FAMILY BACULITIDAE

G I LL,

1 87

I

�;_;�-_ J ,

The Baculit:idae are characterized by an amrnonitella followed by a straight to slightly curved

haft. Whorl section can be circular. ovate, elliptical, trigonal, or pear shaped with a flat venter. Ribs

consist of undulations or slight swellings on the flank and sometimes prominent ridges on the venter.

The degree of tapercan vary from low (nearly parallel venter and dorsum) to high (almost triangular).

Size ranges from small to quite large ( 120 em in length and greater). Eight genera of Baculites exist

throughout the world, but only two genera have been reported from the Pierre Shale. Baculitidae have a worldwide distribution from the Upper Albian through the Maastrichtian Stage.

A Baculite Life Restoration

dorsum

"'J

dorsal lappet -

b

bOdY cham

er

_

e phragmocon -

I

7

Illustrations by D.S. Norton

Genus Baculites Lamarck,

1799 baculus = a taft' + ites = a !>tone

This genu is comprised of a traight to lightly curved . hell except for the ammonitella, which

has one or two minute. planispiral coils.

The cro

eclion can be circular, ovate, elliptical,

compressed elliptical. or triangular. The adult apenure has a short, dorsal lappet and a longer, ventral

lappet rhat is traight to . lightly cur. ed dorsaJJy. The venter commonly hac; ribs, and the flanks may

be decorated by broad rib . rounded to concentric node or broad undulations. The degree of taper generally varies from 0° to 8°. but mo t pecie exhibit a degree of taper of about 2°. The suture ranges from imple in the early form to very complex at the time of Baculites rugosus. Individual species of Baculites are very important index fo

il

in rhe Pierre Shale. comprising 1 8 of the 26

ammonite zone . The following baculite description. arc listed in chronological order from the

olde t to the younge t Range Zone. AI o included are rhe other common species of Baculites. For identification purpo e . a moderate- or average- ize baculite has a diameter of approximately 2.5 to

5 em in a mature bod} chamber.

19

Baculites aquilaensis

Baculites haresi Rccside,

Reeside, 19 27

Baculites aquilaensis is distinguished by a

19 27

Baculites haresi has a very elliptical, well­

compressed ovate cross section, medium size

rounded cross section.

(generally smaller than Baculites obtusus), strong

mens the shell is as round on the venter ac; in the

and short arcuate ribbing that occupies only

dorsum.

about half of the flank and its early appearance of

slightly compressed venter. The shell is smooth,

In large, mature speci­

Younger specimens tend to have a

ribs. The prominent arcuate ribs occur about 2.5

although the ventral edge can be slightly ribbed.

per flank width. The venter i s slightly ribbed and

This specie occurs with

compressed, while the dorsum is smooth and

from the Eagle Sandstone, the Telegraph Creek

rounded. This pecics occurs with Scaphites hippocrepis in the basal Pierre Shale and its

Formation, the Steele Shale, the upper part of the

equivalents (the Steele Shale, Mancos Shale, the

Wyoming, South Dakota, Utah, and New Mexico.

Scaphites hippocrepis

Mancos Shale and the Pierre Shale of Montana,

Eagle Sandstone, and the Telegraph Creek For­ mation) i n Montana, Wyoming, South Dakota, Colorado, New Mexico, and Utah.

Baculites haresi

Side view USNMH 73298 7.6cm long

Baculites aquilaensis

Side view USNMH 73298 6.8cm long

Raculires aquilaensir

suture pattern

Baculites haresi

cross scc11on

�� 0 20

Ammonite� and the other Cephalopods ofthe Pil'rrl' St'away

suture pattern

Recstdc. 1927

cro�s section

0

FA�liL"r

-� '

B'\( lJI I I II >AI

Baculites sp. (smooth)

Baculites sp. (weak flank ribs)

Bacullles sp. (smooth) USGS D 3550 6.3 em long

Baculites sp. (weak flank ribs) USNM 23639 18 em long

This species is the first (oldc l) ofthc baculitcs

Directly above the Baculites sp. (smooth), in

a Range Zone fossil. Specimens

the Gammon Ferruginous Member of the Pierre

10 be used a

have an ovate cro s section and a low degree of

Shale and equivalent for-

taper. They are generally quite smooth on the

mations, is the unnamed

llanks, hence, the infor-

baculite,

mal name. ribbing.

(weak flank ribs).

The venter

can reveal some minor

Baculites sp.

1 smooth) reache

3 to 5

t:m in diameter and 15 to .10 em in length.

This

Baculites sp.

0

Gill & Cobban l973

lt is

characterized by low ar­ cuate ribs on the flank and a smooth to well­ sp. (weak flank ribs) is a moderate-sized baculite

�uccessive species up to

similar to its predecessor

Bacufites g regoryensis

in size, shape, taper, and

have

fairly

suture pattern. They are

�imple suture patterns.

reported from the Pierre

They have been reported

Shale and equivalent-age

from the Lower Pierre

formations in Colorado,

Shale andequivalem-age

Wyoming, South Dakota,

Enhanced View

and Montana.

rocks in Colorado, Mon­ tana, South Dakota, and

0

Gill & Cobban I '173

ribbed venter. Baculites

baculite and all of the

s i m i lar,

c:ross�JC>Il

Enhanced V1ew

Wyoming.

Bacufltes sp. (weak flank ribs)

Bacvlrtes sp. (smooth) USGS D 3550 cross sectJon 21

F'\�111 ' fiAt ULITIOAI.

-,'!"

Baculites obtusus

Meek, 1876

Baculites obtusus is a small- to moderate­

sized conch that has very little taper, an ovate

cross section, smooth to well-

Baculites mcleami Lande

, 19 40

Baculites mclearni bas a

moderate ovate cross section.

The species is characterized by

widely spaced, broad flank ribs,

ribbed venter, and nodelike

llank ribs or blunt nodes

and a smooth to weakly ribbed

for the shell diameter.

Its

bines features of the earlier

ity and has rectilinear lobes

Baculites asperifonnis in its ribs

venter. Baculites mcleami com­

spaced about every two ribs

Baculites obtusus and the later

suture isofaverage complex­

and low degree of taper. The

and saddles. This species is

suture pattern is moderately

found in the Sharon Springs Member of the Pierre Shale

complex. Specimens are found

Colorado, and New Mexico,

Springs Member and lower part

in the upper part of the Sharon

in South Dakota, Wyoming,

of the Mitten Member in Wyo­

as well as in the Claggeu

ming, South Dakota, and Colo­

Shale in Montana.

rado, and i n the Claggett Shale in Montana.

Baculites obtusus

Baculites obtusus

Baculites mcleami

USGS 02624

Ventral v1ew

USGS 06372

cross section

USGS 02624

cross section

Baculites mcleami

9.5 cm long

Ram/ires nhrusu�

Z#lf� rLs-v'Q �uturc panem

cro!>> seccion

22

Ammonites and tire other Ct'plralopods ofthe Pierrf' Seaway

35 cm long

Baculites mrleami

sumre pattern

vl�

Recside 1927

USGS 06372

Cobban 1962b

cro>s section

Baculites asperiformis

Meek. 187 6

Baculites sp. (smooth species)

Buculites asperifonnis also has

Baculites sp. (smooth species) is an un­

,mall degree of taper, ovate cross

named pecics found just above the top of the

�<�on, smoolh 10 well-ribbed ven­

Sharon Springs Member in eastern Wyoming. It

�- .111d rounded flank nodes spaced

has a low degree of taper, a

ut one for every distance of the

subelliptical cross section, and

�II diameter. Meek described i t as

is smooth on the flanks and ven­

ter. It i moderate 10 large in size

. mg "strong, oblique, nearly ,.....11ght ri dges or undulations, cx-

wi th a suture of average com­

A sim i l ar species of

�ndtng entirely across the sides."

plexity.

T�c suture is of average complex-

about the same age from Russia

This species has been found in

w as described as Bac:ulites

£i'c upper part of the Sharon Springs

cohbani K hak imo v in 1 976 and

\fember i n Kansas, Colorado, Wyo­

was supposed to be the name for

m t ng, and S o u t h Dakota, the

Baculites sp. (smooth species) . However, there is a noticeable

( .tgg:ett Shale of Momana, and in u e Lewi s Shale in New Mexico.

difference in the constrictions

on the middle lobe of the suture of the Russian form, which make this name, Baculites cobbani, doubtful for the spe­

Right Baculites asperiformts USGS 08224 27.5 cm long

cies in the Western Interior.

Baculttes sp. (smooth species) USGS 02140 cross sect100

Baculttes aspenformts USGS 08224 cross sect100 Raru/ites aspuijon11if

suture pattern

MeeL 1 876

cross section

0

Bacufttes sp. (smooth species) USGS 02140 14.3 em long

Baculires sp. (smooth species) suture pattern cro>> >t:clion

Gill & Cobban 1973 23

Baculites perplexus

Baculites gilberti Cobban,

Cobban. 1 962b

Bac:ulites perplexus has a gentle to low taper

1 962b

and a corrugated venter with smooth to weakly

Baculites gilberti is found between an early and late forrn of Baculites perp/exus. This mod­

sculptured flanks.

erate-sized baculite has a ribbed venter

The prominent ribs on the

venter average about four ribs for the shell diameter. The suture i s of average complexity. The species is larger than average size for the genus. Specimens have been found i n the Mitten Member of the Pierre Shale, around the Black Hills, in the Steele Shale in central Wyoming.

Baculites gtlberti

USGS 07804 9 em long

in the Claggett Member o1 the Cody Shale in south cen­ tral Montana, in the upper

with average spacing of six ribs per shell diam­

part of the Mancos Shale io

eter. Undulation on the flanks are spaced at two

northwest Colorado. in the

per shell diameter.

Pierre and Lewis Shales in

section in juveniles and an elliptical one in

New Mexico, and in equiva­

adults. The suture is s i m ilar to Baculires perplexus, but the ribbing on the venter is con­

lent strata in eastern Utah.

Tt has a subovate cross

In some areas there is an

siderably weaker and more closely spaced. It

upper and lower Range Zone

occurs in the upper part of the Mancos Shale in

of Baculites perplexus sepa­

northwest Colorado, in the "rusty t.one" of the

rated by

Pierre Shale i n Colorado and Wyoming, and in

Bac:ulites gilberri.

the Mitten and Red Bird Members of the Pierre Shale around the Black Hills. Baculites perplexus

Above: BHI 4763 9.5

em tong Left: BHI 4762

5.5 em tong

Baculttes gilbert!

USGS D7804 cross sec1ion

Baculttes perplexus USGS D6251 cross sectiOn

Barulites puple:rtiS

suture panem

crus.� sections

Cobban 1962b

24

Ammonites a111i the orhn Cephalopods uf tilt!

Baculite.f gilbent

suLUre pattern

Cobban 196211

Pierre Seawa\'

cross >ection

--�-

FAMILY BAtliii iii>At

Baculites gregoryensis

Cobban, 1 95 1 a

Baculites gregoryensis is a rapidly tapering,

'Tioderately sized ammo nite. lt has an oval cross -.:ction that is quite compressed on the ventra]

Baculites reduncus

Baculites reduncus is a rapidly tapering, moderately sized, curved ammonite.

edge. The flanks are smooth, and the venter can

ventral e d g e .

flanks are ornamented

corrugations, especially

•n larger specimens. The suture is fairly com-

Its cross

section is ovate, yet sljghtly compressed on the

'lJve slight ribbing

or

Cobban, 1 977

The

with broad arcuate ribs or undulations.

The

venter i s smooth to slightly ribbed.

The

suture is similar to that of Baculites gregory­

ensis. The species has been

found

in

the

lower part o f the Rock R i v e r Formation i n Baculi/es gregoryensis

Wyoming, i n

BHI 4163 6.5 em long

south­

western and central

plex and characterized by the lateral lobe being

South Dakota, and in

-:-onstricted just above its major branches.

equivalent-age rocks

Baculites gregmyensis is found in the Gregory

in Colorado.

\I ember of the Pierre Shale along the Missouri River in South Dakota. above the Mitten Mem­

Baculites reduncus

her on the northern and southern flanks of the

BHI 4760 12.5 em long

Black Hills, and in central Montana.

Baculites reduncus

Baculites gregoryensis

USGS D1 392 cross section

BHI 4163 cross secllon

Baculius gregoT)'ensis surure pallCm

Cobban 1951

croo;s section

Baculi1es reduncus

surure pattern

l-ross sections

Cobban 1 962b

25

Baculites scotti Cobban,

Baculites sp. (new species)

1 958a

Baculites scotli is gently tapering and of

Occurring with Baculites scotti is a baculite

average size. The cross section is

form that i. ovate in cross section, has a smooth

ovate yet slightJy compressed on

venter, and has broad ribs or arcuate swellings

the ventral edge. The flanks are

on the flanks. The broad

generally smooth to sl i g h t l y

ribs become almost like

Bac:ulites

a large cone-shaped tu­

scotli can be more complex than

bercle in the smaller

Baculites �regoryensis. Baculites scotti has been found in

node like. These ribs oc­

ribbed.

The sutw·e of

that of

specimens and appear

the Pierre Shale in New Mexico,

cur aboutonce forevery

Utah, Colorado, Wyoming, and

flank diameter. The su­

South Dakota, in the Mancos Shale

ture pattern is like that

in western Colorado; and in a ma­

of its contemporary,

rine tongue in the Judith River

Baculites scotti. This

Forn1ation in east central Mon­

species has been de­

tana.

scribed, but has not yet been published. This un­ published species oc­ c u r s throughout the Western Interior along with

Baculites scotti

BHI 4168 1 6 cm long

(new species) BHI 4671 2 em by 5 em long

BHI 4168 cross section

Baculites scorri

Baculites sp. (new species)

BHI 4671 3 em by 5 em long

CI'Ol..� <;eetions

� (9 Cobban 1958a

26

.

Baculites sp.

Bacutltes scant

suture pattern

Baculites scotti

AmmonirPS and tire orlrer Ceplraloporu of the Pierre Seawcry

(new species) BHI specimen cross section

Baculites sp.

FA�lll ' fil\< l l ll l i >AI

"•.

Baculites pseudovatus

Elias. 1933

Baculites crickmayi Wil liams,

Baculites pseudovatus i the Baculites found

has an ovate cross sec­

Didymoceras nebrascense. It is

conch in juveniles, and

cies that has a gentle taper, a

i n malUre adults. On

Baculites cricknwyi

predominant

tion, a rapidly tapering

throughout the Range Zone of a moderate to large-sized

a slowly tapering �hell

pe­

stoutovate cross section. smooth flanks on most

1930

larger pecimens, broad

pccimen , and

undulations ornament

the flank. The venter

smooth to weakly ribbed ven­

m a y be s m o o t h

ters. Larger specimens have un­

or

w e a k l y to s t r o ng l y

dulations on the flanks. The com­

ribbed. The

plex suture has the terminal

pecies i s

most often found with

branche of the lateral lobe con­

stricted at their base. Specimens

Didymoceras stevensoni

South Dakota, Wyoming, Ne­

rado. Wyoming, Mon­

New Mexico.

suture pattern of

in

have been found in Montana,

ew Mexico, Colo­

tana. and Canada. The

braska. Kansas. Colorado. and

Bac ­ ulites crickmayi is com­ plex and similar to that

of

Baculites pseu do ­ varus.

Bacvlltes pseudovatus

BHI 4162 22.5 cm long

Baculites crickmayi BHI 4165 19 em long

Bacul'les psei.Jdovatus BHI 4162 cross section

Baculllt-s ps�'tiiJI.S 'uture pancm

cross section

Baculites crickmayi BHI 4165 cross section

Baculir�s criclanayi �uture pattern

cross sections

Elia!o 1933

27

Baculites rugosus Cobban,

Baculites corrugatus Elias, 19

1 962a

Baculites rugosus ranges from a large, later­ ally compressed, rapidly tapering form to a smaller, stouter, more ovate form. The larger, more common variety has a flattened ovate cross section, strong ventral ribbing, and a very com­

Baculites corru�-:atus is found in the Didy­ moceras cheyennense Range Zone. Tt has a compressed to elliptical

plex suture pattern. This was the largest of the

cross section similar to,

Baculite species during Campanian time. The

yet more ovate than. the

smaller, immature specimens are more ovate in cross section, but

later Baculites com­ pressus. The venter has

as they grow, they

pronounced corrugations

flatten

on

the

that arc spaced about ev­

flank, and the ven­

ery five to seven ribs for the shell diameter. The

tral ribbing be­ comes very prom­

shell tapers slowly to

inent, with ribs

form a l o n g . nearly

spaced three to

straight shaft. The suture

four for the shell

pattern i s similar to

The

Baculites compressus,

species is associ­

but has an inclined sec­

ated with Exitel­

i� widely distrib­

ond lobe. Baculites corrugatus is found within the zone of Didy­ moceras cheyennense

uted from New

from New Mexico, Kan­

Mexico to Mon­

sas, Colorado, South Da­

diameter.

oceras jenneyi. Baculites rugosus

tana.

33

Baculites corrugatus BHI4161 1 4 em long

kota, Wyoming, and Baculites rugosus BHI 4169 22.5 em long

Montana.

Left

cross section Baculites corrugatus BHI 4161

cross section Baculites rugosus BHI 4170 43.5 em long

Bacu/ue.v rugosus

suture pattern

28

Baculites corrugarus cross sccrion

Ammonites and the orher Cephalopods of the Piure Seaway

suture

pattern

cro�� sections

FAMILY BACULITIDAE

-

•�'::'._

Baculites compressus Say,

1 820

Baculites compressus is the most abun­

dant ammonite in the middle Pierre Shale within South Dakota.

Tt is easy to identify

because of its very compressed (hence the name), elliptical cross section and smooth to weakly ribbed venter. Large specimens have slight undulations on the flank. The species tapers rapidly and can curve somewhat in juveniles.

It is almost straight in mature

adults. Baculites compressus has a very com­ plex suture pattern. Specimens can attain a large size and. within their zone, are the most prolific ammonite, if not the most abundant mollusk that is found.

The species ranges

from Colorado into Canada.

Bacvhtes compressus BHI 4159 cross sect100 BaroiJies compressus BHI 4159 17 an long Baculiz�s compr�.ssu.s

gn:nre pallem

Mecl J SI6

cross section

Baculites compressus BHI 4160 40 cm long

29

Baculites compressus var. robinsoni Cobban,

1 962a

Haculites compressus var. robinsoni was originally described as Baculites var. ornatus by

Robinson, 1 945. However, Cobban renamed it after Dr. Robinson because the type Baculites omatus was described by d'Orbigny, 1 947, from South America. Tills variety has a slight.ly greater degree of taper than that of Baculites compressus. The cross section is compressed to trigonal i n the immature specimen to nearly el liptical in mature specimens, but not as trigonal as Baculites cuneatus nor as compressed as Baculites compressus. The flanks are ornamented with broad arcuate undulations similar to those of

Baculites cuneatus, but occur at an earlier stage of growth. The suture pattern is less complex than that of either Baculites compressus or Baculites cuneatus.

Baculites compressus var. robinsoni occurs from the Baculites compressus and Baculites cunearus Zones of the Bearpaw Shale i n Saskatchewan. south­ western Alberta, and central Montana. The species has also been reported in the Pierre Shale of South Dakota. This is often the mo t abundant baculite found within the middle section of the Bearpaw Shale.

Above:

Bacullles compressus var. robinson/ with Baculltes compressus BH1 4756 41.5 em total length

Above:

Baculites compressus var. robinsoni BH1 4167 27 em long

Right: cross section

30

Ammonite� and the nrher Cephalopods ofthe Pierre Seawll)

Baru/ites cumprt!.uus var. robimoni pauem cro•� sections

surure

_,.�-

FAI' ll l ) BACIJIITI L>AC

Baculites undatus

Stephenson, 1 94 1

Baculites undarus has a stout elliptical to

Bf}culites cuneatus Cobban, Baculites cuneatus is large

The flanks have broad

for the genus. lt is mainly char­

J.rcuate ribs or undulations with an average spac­

acterized by its cuneiform or

mg of 1 .4 per shell diameter.

triangular cross section and

round cross section.

The venter is

hroad and also displays broad to fine ribbing.

narrow venter. When young,

The suture pattern i

the juveniles are often curved

much less complex than

that of its contemporaries, and is nearly identi­

with smooth flanks and a high

c a l to that o f Baculites

degree of taper. Upon matu­

baculus. Baculites undatus

rity they become fairly straight

is small in size for the ge­

with a low degree of taper.

nus, the diameter of an adult

Mature specimens have well­

specimen measuring one to

developed undulations on the

two inches.

flank and slight to moderate

This species was origi­

ribs on the venter. The species

nally described from the

has a very complex suture pat­

Nacatoch Sand of northeast­

tern l i ke that of Baculites

ern Texas and bas also been

compressus. Baculites cun­

found in Delaware. New Jer­

earus is very common from

sey, Tennessee, and Missis­

Colorado into Canada.

sippi.

1 962a

Cobban. 1973, re­

ported the occurrence of this Gulf Coast baculite within the Western Interior in New Baculites undatus

Above: BHI 4034 lateral view 1 1 .5 em high Below: USNM 182427 cross sectK>n

Mexico and north into north­ ern Colorado from the

Didymoceras cheyennense Zone through the Baculites

reesidei Zone. cently,

More re­

Baculites wzdatus

bas been reported from the

Baculites compressus and Baculites ctmeatus Zones in Meade and P e n n i n g tOn Counties in South Dakota.

Baculites cuneatus BHI 4158 cross

section

Bacu/ites cuneatus BHI 4158 49 em long

Baculit�s wularus suture pancm

Cobban 1973

� section

0

cross section

Cobban l%2a 31

Baculites reesidei

Baculites jenseni Cobban,

Elias, 1 933

1 962a

Baculites jenseni is large and has an ovate cross section. It is characterized by its low degree of taper, !>mooth flanks, and a dorsolat­ eral depression. Young adults have ribs on the ventral edge (about nine per shell diameter), but older more mature speci­ mens seem to be moother. The suture i similar to that of Baculites compressus. Speci­ mens have been recorded from

Baculites reesidei is very similar to Baculites compressus in shape but wilh a compressed trian­ gular cross section. and a slightly less complex suture pauern. Adults generally have a slight degree of taper, but young juvenile shells can taper rapidly. The ven­ tral edge has larger and wider spaced ribs that form slight corrugation that distinguish it from itc; predecessor, Baculites

the Pierre Shale of Colorado, South Dakota, and Wyoming, the Bearpaw Shale of Mon­ tana and Canada, and the Lewi Shale of Wyoming.

c:ompressus. Baculites reesidei has been re­ corded from Kansas, Colorado, W y o m i n g . South Dakota, Mon­ tana, Alberta, and Sas­ katchewan.

Left Baculites jenseni

BHI 4045 7.5 cm long

Baculires reestdel

BHI 4157 23cm long

Baculttes reesidei

BHI 4157

cross

seCIJOil

Left Baculites Jensem

USGSD8018 cross sectJon

Above: Baculttes jensem

BHI 4757 33cm long

Bantlires ree>idei

suture pattern

cross

cross secuons

Cobban l%2a

32

Anmzmures and rhe urher Cephalnpods af rile Pterre Seal•·ay

secuon

-,---

FAMILY BACULITIDAC

Baculites eli.asi Cobban,

1 958a

This species is described as an average-sized baculite with a low degree of taper, smooth flanks, a nearly smooth venter, and a very elliptical cross sec­ tion. Smaller specimens can be slightly curved and taper as much as 6°, whereas. the larger the specimen, the lower the angle of taper (as little as 1 '). The surure pattern is similar to but less complex than Baculites compressus. The pecies is common i n the Bearpaw and Pierre Shales of Montana. Saskatchewan, and Alberta, and i n the upper part of the Pierre Shale of Wyoming and Colorado. Abundanl bul poorly pre­ served specimens occur in the Virgin Creek Member of the Pierre Shale in the Missouri River valley in South Dakota and northeastern Nebraska. The species is also known from the Pierre Shale in southwestern North Dakota and from the Sail Grass Member of the Pierre Shale of western Kansas.

Baculites efiasi BHI 4173

11.5 em long

Right: Bacufltes ehasl BHI 4173 cross section BacuJites elias/ BHI 2090 4S cm long &culitn diasi surure panem

��4,�i'1 (9 Cobbdn 1958a

33

�.;,

FAMILY ISA< LILITIDAI'

Baculites baculus Meek and Hayden,

1 86 1

Baculites baculus can attain a large size and has a n elliptical to ovate cross section i n young juveniles. As it matures, the cross section can become circular to almo. t quare. Tt has nearly smooth flanks in juveniles, but as they increa-;e i n size, they develop low, broad lateral rib or undulations . Bacu/ites baculus has a very slight degree of taper except in the mailer pecimens. The suture pattern is simplified like that ofprc-gregoryensis baculites. The specie. appears to be a migrant from the Gulf Coast region and wao;; the ancestor oflater endemic species. lLc; ancestor seems to be Baculites undatus that ot:curs in rocks of a much earlier lime within the Western Tnterior. Baculites baculus has been found from Colorado to eastern Montana (Glendive area) and also in Alberta and S askatche wan .

Left: Side v�ew Baculites baculus BHI 4166 13.5 em long Above: cross section

Baculites baculus Above: BHI 4681 7.5 cm long Below: BHI 4680 7.6cm long

Bacuilres bacutus cross sectJons Lell BHI 4680 Roght BHI 4681

Racu/1/eJ barolus

�uturc pattern

cross

section

Meek and Ha)den 1 86 1

34

Ammonites and riot' othu Cephaloporu ofIM Piern: &cnun

Baculites grandis

Hall and Meek, 1 854

derived from the extremely large size of mature adults. Some specimens of Baculires grandis have been confinned at more than 100 em (over 3 ft) long, making this species one of the largest known within the Family Baculitidae in the world. The cross sect ion changes from Thi specie name i

nearly ovate in juveniles to almo t lrigonal in large adults. The flanks have very broad crescentic undulations, but smaller individuals do not show these undulations. The ven ter become

more pronounced or narrow in relationship to the robust flanks and

dorsum as the baculite mature . The maller the specimen, the greater the taper. More complete specimens also show similar to that of Baculites baculus.

light curvature.

The suture pattern is

Baculites grandis ranges from Colorado and

Kansas, and north into Montana

.

Bacu/rtas grand1s BHI 4171 cross secbOn

Baculites grandis BHI 4171 ventral view 1 6 cm long

8acJJiites grandis

Baculnes grandJs S Jotgensao collection 84 em long

suture pattern

cross sections

Hall and Meek 1855

35

F/\�111

y

15AC l/Lilll>/\1.:

·;,

Baculites clinolobatus

Elias, 1 933

These are the last of the large baculites from the Western Interior. The cross . ection is compressed ovate in younger conchs to more triangular in large adults. The angle of taper is low. Larger adults developed widely paced, low, broad undulation on the flank, whereas young individuals arc smooth. Baculites clinolobatus has a more complex suture pattern than Baculites grandis and somewhat resembles the uture of Baculitesgregoryensis. The species has been found in Kansas, Colorado, Wyoming, and South Dakota.

Left: Baculites dmo/obatus DMNH specimen (aduh) 28 em long Below: cross section

Buculitel clinolobarus

;uture pattern

c=

scctioru. Bacurtl es dmolobatus Above: BHI 4759 12.5cm long R1ght BHI 4758 20 cm long

3(1

Ammoniiel alld Ihc• other Cephalopod.f

OJ the Piure Seaway

...

FA�1 1 1 ' l�t\t l liTID/\1

Genus Pseudobaculites Cobban,

1 952b

pseudo = false + baculu.1 = a staff + ires = a stone

This genu has a straight bell with a rapid raperof generally 10° to 13°, an oval to elliptical whorl

section, and broad undulation on Lhe venter. Individual specimens are shaped more like t1attened cone than representative of the Family Baculitidae. The flanks are ·mooth to very ornate, with

�orne forms having nodes on rbe dorsal Jape of the flank. The genus differs dramatically from its contemporaries by having an unusually large . hell

with a very rapid taper and a complex suture

partem similar to Baculites compressus.

Pseudo­ baculites has been found in rocksofLateConiacian

Age in Wyoming. Utah, and Colorado, and late

Campanian rocks of Wyoming and Saskatchewan.

Pseudobaculites natosini (Robinson,

1 945)

This species has perhap· the largest body cham­

ber of any other species within the Family

Baculitidae, yet with its rapid taper i l never achieves a long i7e.

Pseudobaculires Jzawsini has been described from the Bacu/itesjenseni Zone of the Lewis Shale in central Wyoming. the

Baculites eliasi Zone of

the Pierre Shale in east cemral Wyoming, the Beacpaw Shale in Mon­

tana. the Pierre Shale of

north central Colorado,

and the Bearpa\\ Shale of

outhwestern Sa -

katcbe\\an (Cobban and Kenned)'. 1 994b).

PseutJobacUttes na1DSJni USGS 04508 24 an long

Pseudobaculites natosini 04508 aoss sec1Jon

USGS

37

BACULITE IDENTIFICATiON .:.1_ �

The authors have compiled this guide in the hopes of simplifying the process of identifying baculite specimens. The authors intend that thi

identification guide should be used in conjunction

with the preceding scientific descriptions. Please refer to them for additional information. The baculites are described as small, moderate, or large. A moderate-sized baculite is one that has a cross section of 2 to 5 em or l in. by 2 in. However, smaller and larger specimens of the same species are found becau e of the presence of juveniles and large adults. We have also described ventral and flank ornamentation with the brief descriptions of the bacul ites. These form of ornamentation are rarely present on juvenile specimens. Nearly all mature forms of baculites develop some sort of flank rib , and may also lose their ventral ribs. Very old baculitcs may lose all ornamentation and become more inflated. The cross sections arc aLo quite variable. Young, mature, and old baculites of the same species will vary to some degree. Different localities within the arne Range Zone might also produce slightly different ornamentation and cross section within the same specie . A low degree of taper i considered by the authors to be less than 2°, and a high degree of taper is 4° or more. Please consult the references if you have other questions concerning identification. The following identifications are organiL.ed from youngest to olde t form.

TypiCal suture pattern

) )

Baculites clinolobstus Elias, 1933 Elliptical to compressed trigonal cross section Generally smooth venter Smooth flanks developing undulations Low degree of taper Moderate to large

Bacu/ites grsndis Hall and Meek, 1854 Ovate to nearly trigonal cross section Smooth to broad ventral ribs Generally broad undulations with a ventrolateral depression Low to moderate degree of taper Large

) ) ) J�

oe

Ammonites and the th r Cephalopods of the Pierre Seaway

Baculites bscu/us Meek and Hayden, 1861 Ovate to circular 1n cross section Smooth to well-ribbed venter Smooth to undulated flanks Low degree ol taper Large

lllustrallons by N. Larson

B;\lt t t t t

- . . -;;

ltHNtttt
..

Typical suture pattem

0 0

Baculites e/iasi Cobban , 1958a Ovate cross section Smooth venter Smooth flanks Low degree of taper Moderate

) ) ) )

Baculites jenseni Cobban, 1962a Strongly ovate cross sectJon Ventral nbs averagtng mne to twelve per shell diameter Smooth flanks with ventrolateral depression Low degree of taper Moderate Bacul/tes reesldel Elias, 1933 Compressed cross section Ventral ribs averagmg seven to eight per shell diameter Smooth to weakly ribbed flanks Moderate degree of taper Moderate to large

0

Baculites cuneatus Cobban, 1962a Tngonal CfOSS section Strong ventral nbs, soc to nine per shell diameter Broad short lateral ribs, one to three per shell diameter H!Qh to low degree of taper Moderate to large

Bacu/ites compressus Say, 1820 Compressed cross sec1ton Smooth venter Smooth to weakly nbbed flanks H.gh to low degree of taper Moderate to large

Baculites corrugatus Elias. 1933 Compressed CfOSS section Prorrunent ventral ribs,five to seven per shell diameter Smooth flanks Slight degree of taper Moderate to large

8

))

Bacu/ites rugosus Cobban, 1962a Compressed cross sec1ton Strong ventral bs, n three to four per shell diameter Smooth to weakly ribbed flanks Htgh to low degree of taper

Moderate to large

39

15,,, L 1 ITr I r" N 1 1 t I< ,, l iON G UlllL

'J

Typical suture pattern

Bscu/ites crlckmayi Williams, 1930 Ovate cross secti0/1 Smooth to well-ribbed venter Sculpted flanks with broad undulations. about one per shell diameter Gentle taper Moderate

g 0

Bsculites pseudovatus Elias, 1933 Ovate cross section Smooth to weakly ribbed venter Smooth to weakly ribbed flanks Gentle taper Moderate

Baculites sp. (new species) Ovate cross section Nearly smooth venter Broad, almost nodelike ribs, one per shell dlluneter Gentle taper Moderate

j..//

0 122.22?! 40

Ammonites arul the other Cephalopods of the Pi�"� Seaway

Baculites scott/ Cobban, 1958a Compressed ovate cross section Smooth venter to slightly ribbed Smooth to slightly ribbed flanks Gentle taper Moderate

Baculites reduncus Cobban, 19n Ventrally compressed ovate cross section Smooth to slightly ribbed venter Broad arcuate flank ribs, about two per shell diameter Hlgh degree of taper Moderate Bsculites gregoryensis Cobban, 1951a Compressed elhptlcal cross section Slight to welkibbed venter Smooth flanks on Juveniles Slightly nbbed flanks on adults Hogh degree of taper Moderate

B\{ I

I III 11>1 "iTif

(

\ f l l)r,

!li,

Ut'IDI

Typteal suture pattern Bacu/ltes gilbert/ Cobban, 1962b

Subelliptical cross sect100 Prorrunent ventral ribs, about six per shell diameter Broad flank nbs, about two per shell diameter low degree of taper Moderate

Bacu/ltes perplexus Cobban, 1962b ElhptiCal cross section Promment ventral ribs, about four per shell diameter Smooth to weakly nbbed flanks low degree of taper Modelate

0 , __)___. 0 1.2....?.. J _____

Baculltes sp. (smooth) Subel'PliCal cross section Smooth 11enter Smooth Hanks low degree of taper Moderate Baculites asperlformis Meek, 1876 Ovate cross sectJon Smootn to weiJ.nl>bed venter

Strong, oblique undula!IOilS Of broad nbs, one per shefl diameter Low degree of taper Moderate

Bacu/ltes me/earn/ Landes, 1940 Moderate to ovate cross section Smooth to weakly ribbed venter

Widely spaced. broad flank ribs, about l11> per shell diameter Low

degree of taper Moderate

0 12.2.2.221

Baculites obtusus Meek, 1876 Ovate cross secoon Smoolh lo wel-nobed venter Node 'II! flanl( nbs. about two per shell diameter low degree of taper Moderate

Baculltes sp. (weak flank ribs) Rolm to ovate cross section Mlnor to well-ribbed venter

Broad arcuate ribs or swellings on flanks, about one per sheU diameter Moderate

0 '

J

Bacu/ites sp. (smooth species) Ovate cross sectJon Minor nobong on venter Smooth flanks Siogtll degree of taper Moderate

41

· ;r

FAMILY COLLIGNONICERATIDAE W RIGtiT:,-·AND The Family Collignoniceratidae i s characterized b y compressed oval to nearly square whorled forms of planispiral ammonites with a generally evolute umbilicus. The venter hac; a errated or notched keel with clavate-type node and tubercles or clavi along the ventrolateral shoulder. Ribs are dense to widely spaced, generally broad, and typically ornamented with tubercles, clavi, or bullae. The family is distributed worldwide from the Lower Turonian through the Middle Campanian.

Genus Menabites (Delawarella) Collignon.

1 948

Menabe = a Lown in Madagascar + ires = a stone This genus and subgenu. have moderately ovate to subrectangular whorl sections. Ornamenta­ tion consists of prominent umbilical and ventral shoulder tubercles on every rib. On adult forms, the ribs become more faint and generally display one or two row of tubercles. The ventral edge is slightly depressed on either side ofthe keel when it again forms a rounded ridge above the siphuncle. The genus and subgenus have been reported from France. Tunisia, Madagascar, New Jersey, and occasionally within the Western Interior of North America.

Menabites (Delawarella) danei (Young,

1 963)*

Menabires (Delawarella) danei is distingu.il>hed by trituberculate ornamentation, low, broad ribbing, an evolute umbilicus, and an oval to subrectangular whorl ection. The venter hac; a broad, shallow groove separating the ventral shoulder from the siphuncle ridge. There are nine to ten ribs

per whorl section that are prorsiradiate. broad. and coarse. with wide spacing. Tubercles arc present

on the umbilical shoulder, midflank, and on the ventral edge. Clavi are present on either side of the

siphuncle ridge. The specie has been found in the Gober Chalk and the Ozan Formation of Texas, the Ozan Formation of Arkansas, and is sparsely reported from the

Baculites obtusus Zone of the

Apache Creek Sandstone Member of the Pierre Shale near Pueblo. Colorado.

Side and ventral VIew Menabltes da!lel USNM 14571 13.3 em tugh

•

Parentheses enclosing the author's name indicate that his original description placed the species In a genus not currently accepted for that species. 42

Ammonites and the ather Ceplw/opods of the Pterre Seaway

,

FAMILY COLLIGI'IOI'UCERATIDAE

:'

Menabites (Delawarella) vanuxemi (Morton,

1 830)

This specie can be quite large (up to 17.5 em}, and it is generally compressed with a sub­ rectangular whorl ection. The umbilical wall i

hort and steep, and the flanks are flat to slightly

rounded. Ribbing is dense with 22 ro 23 umbilical bullae per whorl, giving rise to 35 or 36 straight, prorsiradiate rib . All the rib bear umbilical and ventral boulder rubercles, midl1ank tubercles, and ventral, marginal clavi. As in other Menabites, a mall hallow groove separates the ventral marginal clavi from the siphuncle ridge. This species is present in New Jersey. Texas. and the upper part of the Manco Shale in New Mexico.

Side and venter -

Merlabl:es vanuxetn� USNM 1 4543 1 2 an high

Genus Submorloniceras Spath. i.JJ

=

lm�er in ran

...

1 926

S. G \fono" + c�ras = hom

The de cription for thb genu close!} follows that of the family. Characteristics specific to this

d whorl -;e.ction. broad. rounded. inner flanks. flat outer flanks, and a flat venter genu are a compre. .e bordered. by rubercle with a light, rounded ridge over the iphuncle. The flanks have low, broad rib with lateral. vemrolateraJ, and umbilical

boulder rubercle . The species, Suhmortoniceras

tequesquirense (Young. 1963 ). bas been found in the upper �Janco Shale of New Mexico. The genus has al o been found in Africa Japan. Delaware. �ew Jerey. and Texas. We unfortunatel y do not have a photograph of Lhi. pecies.

43

�-

FA\IILY DESl\IOCERATIDAE ZITIEL.

1 895,.-

The Family Desmoceratidae is defined by thick, round nanks and planispiral coiling. The whorls are general Iy round, oval, or even spear-shaped (having pronounced keels). The flanks are generally smooth to weakly ribbed with occasional constrictions. The family occurs world\;Vide from the Lower Cretaceous through the Upper Cretaceous.

Genus Parapuzosia Nowak, para = near+ pu;;osia

1913

The genus commonly attains a size greater than 60 em. The umbilicus is moderately involute, and the umbilical walls are steep and high. Flanks are flat to slightly rounded with prominent primary and some secondary ribs on the inner whorls. The genus occurs from the Cenomanian through the Campanian in Africa. Europe. and North America.

Parapuzosia bradyi

Miller and Youngquist, 1946

This species is the largest known of all the ammonite species from North America. With verified reports of more than 137 em ( 4.5 ft) aero

and estimations of greater than 1 80 em (6 ft) across, this

ammonite was truly a giant. The whorl section is oval shaped: the umbilicu is moderately involute with steep, high walls. The flanks are generally smooth and rounded with ribs present on the inner whorls. The species has been found only in the upper part of the Eagle Sandstone of Big Hom County, Montana, and the upper part of the Cody Shale

(Sc:aphites hippocrepis Range Zones), Big

Hom County. Wyoming.

Parapuzosia bradyi Carol Cheatham, a rockhound from Greybull, Wyommg, Is shown standing next to the largest known ammonite from North Amenca, Parapuzosia bradyi. The photo is dated 1964. Th1s specimen was oollected from the Cody Shale near Greybull and 1s on display at the Greybull Museum. The specimen is miss1ng at least one·half whorl of body chamber. If complete, 1ts size would 1ncrease to over 6 feet across. Note also the 'smaller" specimen on the nghl. Photo oourtesy of Dr. Wilham Cobban.

44

Ammonite.! and thP other Cephalopods of the Pierre Seawll)

FAMILY DtPLOMOCERATIDAE S PATH,

l-�-2'6

Diplomoccratidae seems to be an offshoot of the Nostoceratidae family. They have loose coils tending to bilateral symmetry in one plane and develop fine to broad ribs with constrictions at different stage

of growth.

Some forms had ventrolateral tubercles or spines.

However, most

varietic did not pos es thi form of ornamentation. The family occur worldwide in the Upper Cretaceous from the Turonian through the Maastrichtian.

Genus Exiteloceras

Hyarr. 1 89 4

e:ciu/ = becommg exunct - cera.s = hom

Thi genu

is de. cribed a having too e. ellipticaJ, planispiral coiling and a subcompressed to

oval- haped whorl section.

Rib

are simple in the early

tage , becoming more complex with

branching and intercaJation in later tages. Nearly all of the ribs that eros the flanks and venter have tubercle and pines. The 'entercan be flat to rounded and the suture pattern i complex. The genus occur in the Campanian of the Western Interior Seaway and the Mount Laurel Sand of Delaware. There is also a repon of it po

ibly having been di covered in Colombia, South America.

Exitelocerasjenneyi (Whitfield. 1 87

7 )

Exireloceras jenneyi i the onl} described pecie for the genus, so the description follows that of the genus very close]). The pecies in the juvenile stage resembles a juvenile baculite with the small ammonitella followed by a nearly traighL. slightly ribbed . haft and angular to semicircular bends and loo·ely coiled limb not in contact with the adjacent whorls. Ribs are moderately coarse, generally rursiradiate. and mo t contain ventrolateral pine and tubercles.

£ritelocerasjenneyi has

been found in the Western Interior in the Pierre Shale of Montana, South Dakota, Wyoming, Colorado. and

ew Mexico: the Bearpaw Shale of Montana: the Manco Shale and the lies Formation

of Colorado: and the Lewi and Pierre Shale of ·ew Mexico.

ExltelocerasJ6f1f16Y! BH1 4149 7.6 an across

Exrteloceras Jenneyr BHI 4115 17 an Wide. 14 an high 45

·'

fMmY DwLO�JOCt::RATIDAE

Genus Glyptoxoceras

Spath, 1 925

glypto = curved + ceras = hom

This genus begins with an initial shaJiow coil (similar to baculitcs) followed by either loose elliptical to round coils within one plane or a helical spire of several whorls. The shell is small and apparently doc not exceed I 0 em in len!,Tth. The whorl section is oval, and the ribbing is generally rcctiradiate and sharp. Suture patterns are quite simple and the absence of nodes or tubercles make this genus quite distinctive.

Glyptoxoceras rubeyi (Reeside, The specimens of

1 927)

Glyptox.oceras rubeyi

(Reesidc, 1927) from the Pierre Seaway eem to have an absence of rib i n the early whorl , more distinct ribs in the middle whorls, and some sped­

mens have alma 1 an absence of rib on the last

portion of the shell. They have been reported from the lower half of the Pierre Shale on the western rim of the Black llills, from the Steele Shale of

G/yptoxoceras rubeyt

central Wyoming, and from the upper part of the

USNM 73292 2.3 em across

Mancos Shale in Moffat County, Colorado. Regarding this specie , W. A. Cobban (written communication. 1 994) tales: "This genus is i n need of revision inasmuch as i t includes species that have similar adult growth stages and ornament but very different juvenile !,rrowth stages. S pecirnens from the Gammon Ferruginous Member of the Pierre Shale

( Scaphites hippocrepis Ill) begin with a minute planispiral coil ( irnilar to that of

Baculites) followed by loose elliptical to circular whorls. Specimens from north Texac;. about the age of the Raculites obtusus Zone, begin as a small helix followed by loose circular whorls. Specimens from France (possibly about the age of Baculires mcleami or Baculires asperifonnis Zone) begin as a minute coil (like that of Baculites) followed by a straight, smooth shaft, then a narrow helix, and fmally the loa e, circular to elliptical. adult coils." Further research may find that

Glyptoxoceras may

repre ent more than one genus and that some may not belong in the Family Diplomoceratidae but perhap in the Family No toceratidae.

Glyptoxoceras rubeyl

USGS 03647 5 em across

46

Ammonites and the mher Cephalopods ofthe Pierre Seaway

fAMIIl DIPLOMOCERAnDAE

,· . · �t; Genus Solenoceras Conrad, solen

=

pipe + ceras = born

1 860

Solenoc:eras begins with an ammonitella simi­ lar to baculites and continues wilh a long, straight shaft that at one point turns 1 80• and bends back on itself, similar to a bobbypin. The whorl section is ovate to circular. Ribs arc quite distinct and gener­ ally lie perpendicular to or at slight angles to the shaft.

Small tubercle

and even

pines occur on

Solenoceras mortoni BHI 4019

1.5cm long

either side of the venter on nearly every rib.

Solenoceras is found from Africa to Europe to North America in lhe Campanian and Maa<;trichtian

Solenoceras have been Solenoceras crassum (described following): Solenoceras rexanum (Shumard, 1 86 1 ) is known to occur infre­ quently from Lhe Bac:ulites compressus through the Baculites reesidei Zones of Colorado; Solenoceras mortoni (Meek. 1876) was described from the Big Bend of the Missouri. probably within the Baculires gregoryensis Range Zone; andSolenoceras reesidei Stages.

Four species of

described from Lhe Pierre Shale:

Solenoceras sp. BHI specimen

7 em long

(Stephenson, 1 94 1 ) has been recorded from the

Baculites compressus and Baculires reesidei Zones of northern Colorado. The Solenoceras found asso­ ciated with Didynwceras nebrascense, Didymocems stevensoni, and E�itelocerasjenneyi are, at the time of lhis wriling. not published. The species found with Didymoceras nebrascense is pictured here as Solenoceras sp.

Solenoceras texanum

USGS 02825 3.1 em long

Left: So/enoceras sp. with Baculites pseudovatus BHI2146 Baeulite is 6.5 em long

47

f1\�lllY DIPLO�IOCERI\TIOI\E

.•

Solenoceras crassum (W h tif ei ld

. 1 877)

Solenoceras crassumfollows t he descrip tio no fthe genus . It si .however , qu tie lar ge for the spec ei s,h av ng i been re corded up o t 1 8.5 em inlength. Itbeg i ns w tih a n ammon itell a, anopen pl an si p ri al co il,a bro adly curved l mb, i two parallel,t ghtly i joined adult s baft c; joined by a t ghtly i co lied ,a cute elbow, and rurs ri ad ai te r bb i i ng onthe b ody ch a mber . E ach r b i bears at uber cle on either side o ft he ve nter. O ccurren ces n i th e P er i re Se aw ay are fr om the Didymoceras stevensonithrough the Exitelocerasjenneyi Ra nge Z ones from S outh Dakot a. Wyom ing. Co o l rado, and Mo nta na . It bac; also been re corded from C ol om­ b ai , South Ame rica .

Solenoceras crassum Dtdymoceras stevenson1 Zone 1 7 em long Japh Boyce photo

Genus Parasolenoceras Coll gi

no n, 1969

para = alongside + solen = pipe + l'eras = born

Parasolenocerasis ch aracter zi ed by two w dely i sep ar ated ,sm all par allel sha fts con ne cted by an elbow. The init ial sh aft, cons si t ing ofthe phragmo co ne . si re cta ng ul ar to cri cula r inwhorl se ct ion w tih l ow dist n i ct ribs. The elbow and se cond sha f t usua Jiy en compas the body chamber and are cir cular to comp e r ssed in whorl se ct ion. Ribs a re generally prors irad a i te on the ph ragmo cone , cr owded t orurs ri ad a i te at the elbow , and stra g i ht to prors ri adi ate on t he body chamber . Some tuber cles are present on e tiher s d i eof t be ve nter, although they aresm al L One spec es, i Parasolenoceras pulcher, Cobb an a nd

Kennedy, 1991a,

was f ound int he Baculites reesidei Zo ne in nort he rn Color ado . The ge nus h as also bee nrepo ned from the Gulf Coast of the Un tied St ates a nd M adagas car .

Parasolenoceras pulcher USGS476127 5.2 cm long

4R

Anurwmti'S and the other Cl'pha/opoth of the P�rre Seaway

FAMILY NosToct:RATIDAt: HYATI, The Family

1 894:> .�

ostocraridae i de cribed � helicoid

forms of regular or irregular coiling that can occur at early or late gro�Lh tages or anytime throughout its growth. Tubercle and spine are common along the venter and can be paired. irregular. a single fO\\. or completely lacking. Rib are generally broad. nar­ row. straight, and dense. They may also be fine and curved. show

Nostoceratids may

igns of uniform con. tricrions

during any point of their gT0\\-1h; this may be a re ult of gro"Lh topping or lowing down for a short period of time. There are ini tral (left) coiling and dex­ tral (right) coiling forms for nearly all the known pecie of the family . The) apparently de­ scended from the Albian Stage

Turrilitoides from England. The

Life reconstruction of a

family occurs from the Cen­

Didymoceras nebrascense

Family Nostoceratidae IUustration by D.S. Norton

omanian through the Maastrichtian Stage.

Genus Anaklinoceras Stephenson. arui.klin = lean on - ceras = hom

1941

This mall genu has an initial tapering pire of whorls that lies within the open body chamber. The ribbing i

trong and prominenL highlighted b) small rubercles. mostly on the body chamber.

Becau e of its mall ize. thi genu rna) often be O\'erlooked when concretion are being inspected.

The genu bas been found in Israel. Texas. Colorado. Ne� Jersey. and possibly also in South Dakota. Two

pecies ba\e been named. and an as yet unpub1i bed

pecies bas been reported from the

Baculiles scorri Range Zone of Colorado.

Anaklirwceras gordiale Kennedy and Cobban,

1992

Anaklinoceras gordiale has been found only in the Baculites compressus Zone of the Pierre Shale in Grand County, Colorado. It consists of a mall spireofabout31/:!coils urrounded by the body chamber that i in a planispiral coil. The ribs are widely spaced. rounded. and rectiradiate in the early whorl c; and rursiradiate for the remaining rib . Thi

pecie, i

mall and only reaches 2 em in size.

�ras gorrJi;JJe USNM 449783 2 an across

49

·�;:,

fAMILY NosrocrRAliOA[

Anaklinoceras rejlexum Stephenson,

1941

This species achieves a slightly larger size than Anaklinoceras gordiale, up to 3.5 em for macroconcbs and only about 2 em for microconch. . The phragmocone has about 4 to 41/2 coils set in a tapered spire and an i nverted J-shaped body chamber that wraps around the initial coi Is. Ribbing is inconspicuous in the early stage, but become stronger and more prominent throughout the growth of the shell. The venter is somewhat flat, and ventrolateral bullae and tubercles are present throughout most of the coiling. The specie has been found in the Baculites compressus Zone of the Pierre Shale, Grand County, Colorado; Texas, New Jersey, and Lrae!.

Front and rear vtew Anaklmoceras ref/exum

USNM 4451 1 1 4.7 em high

Genus Axonoceras Stephen axon

=

axle + ceras = hom

on, 1 94 1

The genus Awnoceras i determined by mall. loosely coiled, ymmetrical whorls within one plane and small, simple ribs with ventrolateral tubercles. Axonoceras i known from the Campanian of Angola, and Texas, Missis ·ippi. and Colorado.

Axonoceras compressum

Stephenson. 1 94 1

This species is a small (less than 3 em) plani piral ammonite with approximately three slightly eparated whorl . The whorl . ecrion is elliptical to ovate, and the ornamentation consi lS of numeroill> narrow, prorsiradiate. flexu­ ou rib . many of wruch have tubercle · or clavi as they cross the \entrolateral boulder. The venter is flat. and the surure patlem is simple. The species has been described from the Baculites compressus Zone of the Pierre Shale in the Kremmling area of Colomdo. Axonocer.iS compressum USGS 08093 2 cm across 50

Ammonite.! and the other Cephalopods ofrhe Piffre Seak'Q)

j,,

fA�IIIl NosTOCtKATIDAf

Genus Cirroceras

.

Conrad, 1 868

cirros = curl + ceras = hom

Cirroceras is described as having several helical whorls, not touching. and with a loose U-shaped

body chamber. lt ha den e. trong rib and tubercles along the flattened venter in either the entire length of the shell or only on the body chamber. The genu

has been found from the Campanian and Maastrichtian SLagc in western Europe. in

igeriaand Angola. and i n the

Gulf and Atlantic coasts of North America. British Colum­ bia, and only occasionally within the Pierre Seaway.

Cirroceras conradi (Morton. 1 84 1 ) has been found in the Western Interior in the Baculites cwrearus Range Zone near Kremmling, Colorado. Thespecies i s listedas Didynwceras conradi by Cobban and Kenned} ( in a yet unpublished manu cript). bUl tho.e authors now believe the

pecie�.

with its identical appear.mce ro the Gulf Coast pecimens. is better as igned to the genus

Cirroceras.

C1rroceras conradi USNM 16213

6.7 em across

Genus Didymoceras

Hyatt. 1 89-l did)""'''s = double .... ceras = born

The genu

Didymoceras as described by Hyatt con i

1 of loose helical spires that have circular

whorl ections. two TO\\. of paired or irregular tubercle along the venter, irregularly bifurcated ribs,

and a large

- hapcd body chamber. The genu coils sinistrally or dextrally.

Didynwceras has been

found in the Campanian and Maastrichtian Stage of North America, Europe, the Middle East, and Africa.

Didymoceras tortum (Meek and Hayden.

1 858)

This specie. has circular whorl sections and rib that are v. eak. on the dorsum and prorsiradiate,

strong. cocme. and imple (though they may branch) on the flanks and venter. Tubercles are present on the Larger v. horl and bullae on the early whorl . There is a tendency for an irregular positioning oftubercle and a presence of nontuberculate ventrolateral rib . Early growth has open helical whorls in contact v.ith each other.

Later growth

stage. .ugge.t an opening or separation in

their v. horls from the earlier v. horl . and maintain

the

open

helicoid

coiling.

Did.vmoceras tonum i found in the Baculites gregoryensis Range Zone of Sout:h Dakota and Wyoming and in the Annona Chalk of Arkan as.

Dld)mocerns tont.Jm BHI <:108 7.5x 11.5cm

51

:''

fAMII v NosToet:RAnoAr.

Didymoceras cochleatum ( Meek and Hayden,

1 858)

Didymoceras cochleatum is characterized by a circular whorl section and a slowly broadening, loosely coiled helicoid conch. Ribs are low, simple, and rursiradiate, with two rows of tubercles, one midventer, and the other low on the outer whorl (base ofthe venter). Not all of the ribs have tubercles on the venter. but mo t exhibit this ornamenta­ tion. Didymoceras cochleatum occurs in the Baculires gregoryensis Range Zone in central South Dakota and i n the Annona Chalk of Howard County, Arkansas.

Oidymoceras cochleatum BHI · 4019 8 x 13 em

Didymoceras mortoni ( Hall and Meek,

1854)

Didymoceras mortoni differs from itc; contemporary Didymoceras tortum by its irregular positioning of tubercle on the ribs on the ventrolateral flank and by wider, stronger, straighter. and more distinct ribs on the flanks and venter. Initial coils are similar to Didymoceras tortum, but the whorls taper less or do not expand as rapidly as on Didynwceras tortum. Whereac; Didymoceras cochleatum is loosely coiled, Didymoceras mortoni bas narrow. loose whorls, and yet is tightly, heI icaJJy coiled in early stages. Tubercles are midventer and low on the base of the outer whorl, and the ribs are weakly rur iradiate. Oidymoceras mortoni occurs in the zone of Baculites gregoryensis, Baculites reduncus. and Baculites scotti of South Dakota. Wyoming. Colorado, and New Mexico, and in the Annona Chalk of Howard County. Arkansac;.

Didymoceras morlom cast of type AMNH 9550 3 em long

52

Ammonites and the other Cepholopnds of the Pierre Sea�
D1dymoceras mortoni BHI 4764 4 x 3.5cm

fA"IIL\ NosToCt::RAnDAI

� .,,

Didymoceras binodosum (Kennedy and Cobban, Thi

species begins with two open planispiraJ coil

1 993b)

in contact, followed by a slightly curved

slender shaft. The slender whorls then form a loa e elliptical whorl that descends into two loose,

circular, helical whorls on a low U- haped body chamber. Ribs are prorsiradiate to rectiradiate on

the early whorls and become rur iradiate on lhe lower two whorls and body chamber. This pecies exhibits obviou�. unusu­ ally deep, periodic constrictions

repeated every 25 to 30 ribs. There i

a well-defined venter

bordered by ventrolateral tu­ bercle on most of the ribs. The later two coils tend to have tu­ bercles or pines located slightly Dtdymoceras btnodosum 01 487H Steve Jorgensen collection 3cm across

D
above midventer and another row of tubercles or spines low on the base of the venter.

Didymoceras

binodosum i s found i n the Baculites scotti Range Zone of the Western lmerior in South Dakota, Wyoming, and Colorado; in lhe Annona Chalk near Yanc)'. Arkansas; and in the BergStrom Formation in south central Texas.

't)Q�c.

't'

'<)�C! o::,

,

o:.J o "..J Q

"t\. s. (J ""

,

11;1 1<� 'Y\ -n _,cty xt0:0::�oo o®

Didymoceras cf. arclziacianum (d'Orbigny,

1 842)

Thi specie is characterized by 1 1/2 to 2 lao ely coiled helical whorl in its initial growth, followed by 5 to 6 helical wborU. in contact with each other on a low. . lightly eparated body chamber.

Rib. are generally trong and rursiradiate. weak to faint on the dorsum. and trong and broad on the

flanks and venter_ Ribs are sometime paired aero

the flank. meering to form tubercles or spines

midway on the ventral edge. and looped between the e tubercles and another

Did)1noceras cf. archiacianum occurs in the Baculites scoui Range Zone in South Dakota. Wyommg. and Colorado. and shows distinct irnilaritie to DidyiTUJCeras archiacianwn from row, low on the outer whorl.

France. The authors believe enough difference.<; do exist. how­ ever, and

Didymoceras cf archiacianum will one day be

assigned a different pecie name.

Left speomen• Ddymoceras ct. arrnaa.anum Di 984E 8.2 ern high Right Oldymoceras ct. afCiliaaaf)(JfTI Di 12758 13..5 ern t»gi1 S. Jorgensen colecoon 53

fAMIL\ NosTOCERAnDAE

:.

Didymoceras nebrascense (Meek and Hayden,

1 856)

Didymoceras nebrascense typically consists of31h loo ely coiled. broad, helical whorls on a large, broad, U-shaped body chamber. Early whorls consist of an ammonitella followed by a nearly straight limb that bends back and gently tapers into a lightly curved limb in a loo e. elliptical, planispiral whorl. Middle growth is generally 2112 broad. almost circular, loose helical coil . The body chamber becomes quite robust as it form a U. Rib are prorsiradiate early. low. and faint. then become wider and more rursiradiate on the remaining whorls and body chamber. Ventrolateral tubercles or spine do not occur on every rib but eem to be on only every third or fourth one for most ofthe growth. The final one-half to two-thirds of the whml before the body chamber lacks tubercles. Tubercle. occur high and low on the ventrolateral boulder early. but slowly drop to midventer and low on the whorls until they fade out on the lower whorl. The body chamber ha<> prominent ventrolateral pines bordering the nearly nat venter. Macroconch body chamber height averages 1 5 em, with an overall height of 20 to 25 em. Microconch body chamber height averages 1 2 em. with an overall height of 14.5 to I 7 em. Macroconchs tend to have l arger and more robust phragrnocones and body chambe� than do the microconchs of the pecie. . Didymoceras nebrascense is prevalent throughout the Western Interior from New Mexico through nonheast Montarta. I! is also found in Delaware and in the Misha h Formation of l rae I.

AboYe Oldymoceras nebrascense wrth Solenoceras sp� Bacufttes pse00ova1u:s, and Scaphrtes 9 BHI4834 40 an long 25 an htgh

Dtdymoceras nebrascense BHI 4113

21.S cm h1gh

54

A11u110IIItes a11d the other Ct'phalopods oftht' Ptt''" St'<Jl4U)"

Dldymoceras nebrascense BH1 4112 7 cm across

f'APIILY NosTOct'.KATIDAI'

··,: .

Didynwceras stevensoni (Whitfield.

1 877)

Didymoceras ste\•ensoni is described. in early growth. as a loose. elliptical. or upside-down U-shape with an initially curved. gently enlarging haft on two lightly maller, loose helical whorls. These whorls grade into three broad helical whorls that are in contact with each other or nearl y so on a broad. hallow U-shaped body chamber. Ribs are broad and rectiradiate to rursiradiate . On the

earlier whorls and Limb . the rib-venterjunction exhibits tubercle for almost every rib; later in the growth. nonruberculate ribs are common. The venter or whorl flank is nearly flat and has two rows

oftubercle , one near the base ofthe whorl and the other at midflank ofthe ventral side. Didymoceras stevensoni differs fromDidynwceras nebrasunse by having a largernumberoftighter coiled, he I ical whorls (a spire) in the conch. the pre ence of' entrolateral tubercle on all whorls. coarser and more widely spaced ribbing. and a body chamber shaft that does not extend very far below Lhe whorls before the recurvarure in the fonn of a large U- haped hook. �1acroconchs are one-half to two-thirds the size of the macroconchs. This pe.cie vel) clo.ely re emble its predece sor. Didymoceras cf.

archiacianum. Didymoc:eras stevensoni is found i n the Western Interior from Colo­ rado, Wyoming. and Montana, as well as in Delaware.

DkJymoceras stevensoni

Left Microconch Right Macroconch 24.5 ern high Japh Boyce photo

55

••

fA•m\ NosTOCI.RATIDAE

Didymoceras cheyennense (Meek and Hayden,

1 856)

Didymoceras cheyennense is typically characterized as 2112 to 3 slender, loose helical whorls on a large J-shaped body chamber that has a very long shaft preceding the bend. Macroconch height averages about 20 to 2 1 em, and microconch height averages 1 4 to 1 5 em. Didymoceras cheyennense begins with an initial ammonitella and 1 112 open, yet touching, planispiral coils on a loose, slightly curved, elliptical whorl. The middle helical whorls enlarge slowly and are almost circular and yet not touching. The body chamber i fairly broad. with an initial haft that extends about 1 112 times the height of the initial whorls, then bendc; back to about one-half of that distance. and forms the aperture. The early ribs are ingular, prorsiradiate. and/or rectiradiate. and possess a double row of tubercles on either side of a nearly flat venter. Ribs on the middle whorls are strong and oblique, generally paired, rursiradiate on the venter and prorsiradiate on the top of the whorl. The ventrolateral tubercles tend to be on every other rib on the nearly flat venter. The ribs are broad on the body chamber. They are prorsiradiate at fir t. then recti radiate on the curve, and rursiradiate on the final part of the hook. The tubercles are generally paired but occasionally alternate on either side of the venter on the body chamber. Thi species i Interior Seaway from northern

found within the Western

ew Mexico to central and eac;tem

Montana. lL i al o present in the Mount Laurel Sand ofDelaware.

Left

Didymoceras cheyennense BHI 2139 21 an high

Right Didymoceras cheyennense BHI 2100 15 an high

56

Ammonites and the olher Cephalopods of the Pierre Seaway

Genus Nostoceras

Hyatt, 1 894

nostos = remm + ceras = hom

Nostoceras has acute angled, helical whorls in a tightly coiled spire on a loose U-shaped body chamber. Generally present are paired rows of tubercles on all or most ribs along the ventrolateral shoulder. The ribs are generall y strong and dense with or without some constrictions. This Campanian and Maastrichtian genus has been found i n Europe, Africa, North America, and Japan. Sev­ eral species have been found within the Western Tnterior. but for the most part, they are very un­ common. A few specimens of Nostoceras mono­ tuberculatum, Kennedy and Cobban ( 1 993b) (so named because they have only one row of ventro­ lateral tubercles), have been found i n the Didymoceras nebrascense Range Zone of Fall River County, South Dakota, and another specimen was found in the Did;mwceras stevensoni Range Zone Nostoceras monolllben::ulalum in the Cozzette Sandstone Member of the Mancos BHI2093 Shale. Pitkin County, Colorado. 4.3 em across

Genus Oxybeloceras

Hyau., 1900

OXJbel = eye of a needle ,. ceras = hom

At the time ofthi printing, the genus Oxybeloceras is in doubt and will most likely be changed. The type specimen for Oxybeloceras was OJ..)'beloceras crassum, and that species is probably only a large Solenoceras. The initial coil of Oxybeloceras is similar to that of Didymoceras cheyennense. Early stages of Oxybeloceras consist of an ammoniteUa and 1 112 open planispiral whorls i n contact with each other, followed by a long. lightly curved shaft that eventually bends back tightly on itself, leaving a small open tear-shaped area near the elbow. The long body chamber includes the elbow and the entire second shaft that bends back against the initial shafL The ribs are generally straight and perpendicular to the venter and the dorsum. Small tubercles or e\·en spines occur on the ribs along the ventrolateral shoulders. Oxybeloceras has been reponed from the We tern Interior and from Texas, Arkansas, and Delaware, as well as from Colombia South America In the Western Interior they have been found in Baculites gregoryensis. Baculites sconi, and Did)71wceras cheyennense Range Zones.

Oxybeloceras so. BHI 4111 Baculites scotti Range Zone 62cm long

57

:.••

fAMII.l Nostoa.RAnDA[

Oxybeloceras meekanum ( Whitfield.

1 877)

Oxybeloceras meekanum differs from the Baculite� scotri Range Zone Oxybeloceras by having a much shorter body chamber ratio ro the phragmacone size. The ribbing seems to be slightly les dense than on the earlier undescribed species. Oxybeloceras meekanum is also maller in size than irs predecessor. Following the initial coil . the slightly bent haft broadens rapidly with rursiradiate

ribbing throughouL Tubercles are pre em on all of the ribs on the ventrolateral shoulder. Oxybe/oceras

meekanum i found from northern New Mex..ico to Montana, including western

ebraska and South

Dakota within the Didymoceras cheyennense Range Zone.

Oxybe/oceras meelcanum BHI 4761 1 7 an long The lmtial coils of an Oxybeloceras meekanum. Photo IS greatly magn1fled, apprmumately 6 5 limes hfes1ze

5X

Ammonites and the other Cephalopods of the Pterre Se��>·ay

Oxybeloceras meekanum

BHI 4114 San long

FAI\'IILY PACHYDISCIDAE SPATH, Pachydi cidae include

1 92 2 ;,·

mall-. moderate-. and large-sized planispiral hells with a moderately,

evolute to involute umbilicus. The whorl section can be inflated to compres.ed with generally steep umbilical wall . At early ontogeneuc stage . lhey al o tend to have strong rectiradiate ribs at some

growlh stage. and mo t fonru generall) have rubercle above the umbilicus along the umbilical

shoulder. The family seems to have ari en 10 lhe Upper Albian and continued throughout the Maastrichtian Stage in all lhe hallo\\ Cretaceous seas of the world.

Genus .lfenuites Spath. �"'ll =

Thi

ammonite

ho\\

J 922

::.mall det.uled + it�s = a '>tone

lhe varied difference between the macroconch and the microconch.

Menuites is characterized b) moderately tm olute coiling. very broad. rounded

flanks, a we l l ­

rounded venter. and deep. rounded umbilical walls. Strong. \\ idely spaced ribs are present on the inner coils and at the apermre. M.icroconch of the genu po se s rubercles around lhe umbilical shoulder and ventrolateral tubercle on the li' ing chamber. whereru. the macroconch has smooth ventrolateral shoulders and eilher small umbilical tubercle or none. The genus has a worldwide di tribution and has been noted in Africa. India. Japan. Europe. ru. well as the Western Interior in North America.

�fenuites portlocki (Sharp.

1 85 - ) complexus (Hall and Meek. 1 856)

Menuiles ponlocki complexus follow the de criptton of the genu

in having strong ribs

(approximately 12 to 1 3 per one-half whorl in the pb:rag­ mocone) that radiate from me umbilicu

outward over the

flank. and the venters. orne connecting the rubercles and other ribs separating the ru­ bercles.

The macroconch

vary greatly with a larger size in mature adult and a lack of ornamentation with the exception of rib phragmocone.

on the

Microconchs ha,·e prominent rib

Menmtes ponlocki complexus has been found in the Baculires gregoryensis Zone in South Dakola.. the Red Bird Silty Member of the Pierre Shale. the Rock Ri\·er and ventrolateral and umbilical tubercle

.

Menuttes portlocki complexus Top Side view Bottom: Venter view Left BHI 4144. 3.3 em across Right BHI 4145, 3.3 em across

Formation in W;oming. and the Hygiene Sands10ne Memberofthe Pierre Shale in Colorado. the Manco Shale near Aspen. Colorado. and the Sego Sand­ stone in eastern t:tah.

59

FAMI LY pACI IYDISCIDA.I:':

,._

-

Menuites oralensis Cobban and Kennedy,

1 993a

Tbis ammonite also shows strong variation between the microconch and macroconch. The basic descriptions of this and Menuires portlocki complexus arc the same, but Menuires oralensis has 1 5 to 30 ribs per one-half whorl. The e ribs are difficult to see and irregular i n height. On microconchs the ribs are weak or absent on the living chamber, except near the aperture. The living chamber also possesses ventrolateral tubercles and umbilical bullae along the umbilical shoulder that parallel or alternate with each other on both sides of the venter. The macroconchs get much larger (up to 30 em) and lack ornamentation on the living chamber. Menuites oralensis occurs only in the Baculires scotti Range Zone of the Pierre Shale and equivalent-age rocks. The species has been reported from Colorado, South Dakota, Wyoming, and New Mexico.

Above and Left: Menwtes ora/ensJS

Left BHI 4147 (nucroconch) 9 em across RJQht BHI 2052 (macroconch) 12.5 em across

60

Ammonite� and the other Cephalopods of the

Pierre Semwry

F1\1'111

�

�···"""'

P'1\CHYDIS.CIDA.E

Genus Pachydiscus Zinel, pachy

The genu

==

thick + discus == disk

1 884

Pachydiscus i found worldwide. All the conchs within this genus have common

characteristic of moderate coiling. lightl) e\olute. and well-rounded flanks blending into a rounded venter. The umbilicus i weJI rounded and very deep. There is usually strong ribbing at some stage of growth and a tendency for tubercles. especially around the umbilical margin.

Pachydiscus has

worldwide distribution from the Upper Albian through Maastrichtian Stages.

Pachydiscus (Paclzydiscus) arkansanus {Stephenson,

194 1 )

This specie i the most common form o f large Pachydiscidae found within the Pierre Shale. Like all Pachydiscus, it i moderate!) evolwe \\ith rounded. deep umbilical waUs. The flanks and venter are well rounded.

Pachydiscus

has strong. prominent ribs on the flank crossing the venter and strong pri­ mary ribs rising above the umbilicus on

the

u m b i l ical

Pachydiscus

shoulder.

( Pachydiscus) ar­

kansanus can get quire large, prob­ ably greater than 60 em across. It has been recorded fTom the

Exiteloceras

jenneyi Range Zone through the Baculites compressus Range Zone in the Pierre Shale. The significant dif­ Side and edge VIew Pachyrftscus ct. hombye:nse BHI 4149 23.5 an across

ference

between

Pachydiscus

(Pachydiscus) arkansanus and Paclzydiscus

(Pachydiscus) cf.

oldhami is the more complex suture

panem of Pachydiscus ( Paclzydiscus) arkansanus. Pachydiscus ( Pachydiscus) cf. oldhami (Sharp, 1855) has been reported only from the We tern lnterior from the Baculites compressus Range Zone of the Bearpaw Shale in Montana. A ingle large phragmocone of Pachydiscus p. was found by Walter G. Camack. Pueblo. Colorado. from the Exireloceras jenneyi Range Zone in the Pierre Shale near Pueblo, Colorado (W. A. Cobban. wrinen com­ munication. 1994). and ar least one specimen of Pachydiscus cmarinae has been reponed from the Pierre Shale ne-ar Pueblo. Colorado. A couple of

specimen of Paclrydiscus cf. Jwmbyense Jone . 1 963

have been verified from the Baculires campres.sus and Baculires cuneaJLlS Range Zones of Meade and Pennington Counties of South Dakota

Cast of Pachydiscus catarn USGS speamen 21 an across

61

FAMILY PtAct:NTict:RATIDAt: HvATT,

l �.oo

The Family Placenticeratidae is characterized by mall to large. compre ed. planispiral shell . The umbilicus is moderately involute, flank

are

omewhat rounded. and the venter is flat or

sometimes grooved. Most possess some form of ribbing. which tends to be slightly rectiradiate swellings, but many forms have no ribbing. Placenticeratidae have world\\ ide distribution from the Upper Albian through the Maasrrichtian Stage .

flank

umbilical

shoulder

venter

tubercles

Shell Ornamentation of the Family Placenticeratidae Iustra:bon by N Larson

62

Ammonites and the other Ceplwlopods ofthe Pinre &aMOT

F 1\I'IILy f"LACl:NTIDF.RATIDAE

-·:�

Genus Hoplitoplacenticeras

S pat h, 1922

hoplito = heavily armed foot soldier + placenta = flat cake + ceras = hom

Th si ge nus isc haracter zi ed b ya s o mewhat co mpressed whor l se ct o i n, e vo lute u mb ili­ cus, fla t to s l g i ht y l rou nded f a l nks, a fla t ve nte r.a nd pro mine nt.stra g i ht to pros ri ad ai te r b i s that bea r two row o f ve ntr o a l tera l tu­ be rc e 1 s . The outer row o ftuberc e l s ma ybe o mewhat cla va et . Th i ge nus is ra re i n the Wester n I nter o i r. As ing el s pecime nassig ned to Hoplitoplacenticeras c . f Hoplitoplacentic­ eras coesfeldiense (Sch lute r, 1 867) va r.

schliiteri Mikhailo v. 195 1 ,was o f u nd int he Baculites asperifonnis Zo ne in l.be Steele S hal e insouth-ce ntra l W yo ming . Two other spec ­ i Abolle: cast of Hoplrtoplacenticeras wesfietdensts USNM 132373 82cm hl!fl

ee m o t be Hoplitoplacenticeras marrori (C oqua nd . 1 859) we re fo und in the Bawlites s p. (s mooth) Zo ne a nd Baculites obtusus Zo ne iothe Stee le S ha el a nd the S ha n­ me n that

no n Sa ndsto ne ince ntral a nd southe rn W yo­ ming (W. A. Cobba n. writte n co mmu nic a ­ tio n. 1 994).

Above: cast at Hop/iloplacenticeras marroli USGS specimen Shannon Sandslone 10.8 em high This specimen was GISCOVered 111 the center of a core

dnll sample and IS the finest representative of lh•s genus and speaes from the Pierre Seaway

63

'''J,�

FAMilY PLACI-:I'I rU>ERATII>At-:

Genus Placenticeras placenta

=

Meek, 1 870

flat c.:ake + ceras = born

The genus Placenticeras is characterized by a tightly coiled (moderately involute), lenticular (lens) shaped shell. The umbilicus is well rounded and moderately deep. The flanks are broad and convex and sometimes ornamented with ribs and tubercles along the umbilicus and midflank. The keel or venter is narrow and flat to slightly concave and protects the siphuncle which is near the surface of the shell. The suLUre pattern on Placenticeras is very complex with 10 to 14 divided, deep, narrow-necked saddles, lobes, and sinuses. Placenticeras has been recorded from less than 2 em u p to 90 em in diameter. The genus has a world-wide distribution, and specimens have been recovered from South Africa, lndia, Siberia, Europe, and North America. Their remains are abundant within the Western Interior of North America from New Mexico to Alberta.

Placenticeras sancarlosense Hyatt,

1 903

This species attains a moderate size for the genus of 24 em in diameter. The umbilicus is moderately evolute; the venter is rounded and wide. The umbilical wall is low but steep i n the juvenile stage and sloped in the mature adult. The umbilical shoulder has sparse, broad tubercles that radiate low, broad ribs. A distinguishing feature of Placenticeras sancar/osense is very prominent, ventrolateral tubercles that are evenly spaced on the ends of the primary and secondary ribs. This species has been found in the uppermost part of the Mancos Shale and the basal part of the Mesaverde Formation in the upper Rio Grande Valley of New Mexico.

Placenticeras sancarlosense

USNM 73379 Side and ventral views 1 5 em high

64

Ammonites and rhe nrher

Ceplw/opods of the Pierre Seaway

FAMII.Y PLACENTIDERATIDAE

..

'" �

Placenticeras guadalupae (Roemer,

1 852)

Placenticeras guadalupae has a thick. stout shell at all stages ofgrowth with a moderately evolute umbilicus. It attains a fairly large size for the genus of up to 32 em in diameter. The species is ornamented with several rows of nodes, one above the umbilical margin. one near the ventral edge, and finally, a row of small clavate tubercle along either side of the venter. The species becomes almost rectangular to circular in the whorl section of the adult form.

Ribs are broad and faint

Placenticeras guadalupae has been found in Texas, in the upper part of the Mancos Shale of east central Utah, and in lhe upper Rio Grande Valley of New Mexico.

Placenliceras guadalupe USNM 73381 14.5 em across left Side vtew Right Venter view

65

FAMILY PLACENTIDERATIDAE

.

1�.

Placenticeras planum

Hyatt, 1 903

Plac:enticeras planum is a pccics of medium si.le with the largest known specimens being no more than 25 em in diameter. The most distinguishing feature is its smooth venter. In early tages, the venter is at flrst �lightly concave, it then becomes flat, and finally rounds.

Placenticeras planum

has a double convex near-circular-shaped hell with a moderately involute umbilicus. It also may have tubercles aJong the umbilical shoulder. although some form. arc smooth. The suture pattern is simpler than that of Placenticeras meeki or Placenticeras intercalare. The . uture patlern increases

Placemiceras planum is found in thc lowcr part ofthe Pierre ShaJe on the western rim of the Black Hill in the Eagle in size to the third lateral lobe from the ventral side and then decreases beyond it.

,

Sandstone and Telegraph Creek Formation ofMontana and Wyoming, in the Mancos Shale ofcentral Utah, and in the uppermost Mancos Shale and lowermost Mesaverde Formation in nonhero New Mexico.

PlacentJCeras planum Cast of USGS specimen 20.3 em across

66

Ammonites and the other Cephalopods ofthe Pierre Sea...-ay

FAMILY PLACENTIDERATIDAE

-"'iJ,

Placenticeras pingue Kennedy, Cobban, and Landman,

1 996

This species displays a thick whorl section, nearly rounded venter, and a moderately evolute umbilicus. The name pingue means "fat" in Latin. This species name refers to the inflated or thick flanks. This form is similar to a later species, Placenriceras intercalare, with umbilical shoulder tubercles that each give rise to one or two low. prorsiradicate ribs. The ribs in turn form broad bullate s h aped tubercles that end about three-quarters of the distance from the umbilicus to the ventral edge. The venteral edge is flat early to rounded as i t matures, and low clavi Lend to alternate on either side of the venter. The suture pattern is significantly more simple than that of i ts descendant Placemiceras intercalare. There are 1 1 to 1 2 low lobes and saddles. The size appears not to exceed 27 em in diameter. The species has been found from the Baculites gregoryensis and the Baculites sconi Range Zone of South Dakota and Wyoming. -

Placenticeras pingue Above: BHI 4644 19 x 22 cm Right VeniJ'al view BHI 4646 1 9 cm high

67

-, _ j

FAMil ATIOAE . Y PLACE:I'ITIOE:K

Placenticeras meeki Bohm.

1898

Placenticeras meek:i follows closely the de cription of the genus. The distinguishing features are its smooth convex, broad, nearly unornamented flanks and smooth venter. Some specimens oc­ casionally possess small tubercles along the umbilical shoulder and some slight broad. low ribbing. Placenticeras meeki has a large size range up to 80 em in diameter. The narrow, concave venter i n the smaller specimens becomes more rounded in larger helJs. The species occurs in the Pierre Shale, sparsely in the Exirelocerasjenneyi Zone. and abundantly in the Didy­

moceras cheyennense lhrough Baculites cun­ eatus Range Zones throughout the West­ em Interior.

Plaamticeras meeki BHI4150, 19 em across Above: Flank vrew Right Ventral VIeW Below: Edge detail

68

Ammonit�s and the other Ceplwlopods ofdU! Piure Seaway

....

FAMILY PLACENTIUERATIDAE

Placenticeras intercalare Meek and Hayden. The obvious difference between this species and

1 860

Placenticeras meeki are its smaller size (up to

25 em). thicker whorl section, narrower flanks, and greater ornamentation. There arc two rows of well-defined tubercles on the nanks. one ncar the umbil icus and the second approximately two-thirds of the distance from the umbilicu toward the ventral edge. Minor broad. low, rounded ribs seem to

Placenticeras meeki and has Placenticeras illtercalare is distinguishable by having on

connect these tubercle . The venter is slightly wider than that of the small clavate tubercle

on both edges.

the average three clavi along the ventral edge between each pair of outer flank tubercles. It is difficult to distinguish between macroconcbs or rnicroconchs in

tbi

pecies, although the macroconchs seem to have more rounded, thicker flanks, whereas the microconchs seem to be more de­

Placenticeras intercalare is found primarily in the £Titelocerasjemzeyi through Baculites compressus Range

pre ed in the flanks.

Zones from New Mexico north into Canada.

P'.acentJoeras IIJtert:aJate BHI 41.16 16.5 an across Above. Aan ­ Right. Veotral VteW Below Edge delal BH speamen

1San across

69

•;.·

FAMILY P't.ACENTII>I�KATIDAE

Placenticeras costatum

Hyatt, 1 903

This speci es reprc enls the last reported occurrence of Placenticcras within the Western Interior. As with its predecessor, Placellficeras intercalare, this form has a thick whorl section, broad flanks, and prominent tubercles. There are generally two rows

of tubercles, one row above the umbilical

shoulder and the other about two-thirds the distance from the umbi Iicu to the ventral edge. This form differs from its predecessor both in the suture pattern and in its ventral edge. The three outer suture lobes are more constricted than those of Placenticeras illtercalare. The clavi, al on g either side of the ventral edge, number five between eacb pair of tubercle on the outer flank. The ribs are low, broad, and prorsi rad iate originating on the umbilical tubercles and splining into a pair of ribs that develop ,

into the conical-shaped tubercles furthest out on the flank. The species has been reported from the

/Jaculites cuneatus and Baculites reesidei Range Zones of Colorado, South Dakota, Montana, Cypress Hills of Sac;katchewan and possibly Alberta, and also in the Baculites reesidei Range Zone of New Mexico.

PlacentJoeras costatum

BH14519 17 x 20 cm Above left: Side view Above nght Edge v1ew Left. Close-up VIew BHI 4520

70

Ammonites and the mhu Cephalopods uf the Pierre Seaway

FAMILY ScAPHITIDAE MEEK,

1 87 6

The Family Scaphiti dae i characlerized by its unique J-shaped body chamber_ H aving descended from an Albian and Turonian lineage, scaphites be­ carne more abundant and var­ ied throughout the Western Tnterior during the early Pierre Shale (Campanian). Conch size can vary from extreme!y small (less than 2 em) to quite large (greater than 1 5 em in length). The shell can be compre sed to inflated with a tightly coiled (involute) pbragmocone: the body chamber i not

>·

· �

curved over the phragmocone but rad1er drops

straight down until curving back toward the phragmocone at the aperture. Lateral ri bs are generally straight and branching . The ventrolateral ribs are also straight. Commonly, there are tubercles or bullae located al ong the umbilical shoulder and ventrolateral tu­ bercles located on the body chamber. The family ap­ pears to be mostly lim�������;., ited to the Albian through Maastrichtian

Cretaceous rnari ne sediments life Reconstruction of a Scaphite Ulustrallon by O.S Norton

of

the

northern hemisphere.

Sheri Ornamentation Family Scaphitidae Ulus!rabon by N

l..aJson

71

Genus Haresiceras

Reeside, 1927

after C. J. Hares + ceras = born

The djstinguishing features ofthi ammonite are a very involute phragmocone and tightly coiled body chamber. The whorl section is compre

ed and the venter is flat with ventrolateral nodes. The

ribs are slightly flexuous, fine, and widely spaced, with a forward bend. The surure pattern is complex and shows a typical scaph.ite pattern in the large size and form of the first lateral saddle. The three species of Haresiceras from the Pierre Seaway occur in the Gammon Ferruginous Member of the Pierre Shale on the northern flank of the Black Hill.

.

Haresiceras placentiforme Reeside, 1927, al o

occurs in the Telegraph Creek Formation in northwestern Wyoming and Cody Shale on the southeastern part of the Big Hom Basin.

Haresiceras natronense Ree, ide, 1927. has also been found

in the Cody Shale of western and central Wyoming and in the upper part of the Mancos Shale in northwestern Colorado. The genus occur within the

Scaphites hippocrepis Range Zones. and is

limited to the Western interior region of North America.

left Side and veotral view Haresiceras fisherl cast of USI'<M 73387 2.7 cm hogh

R�ght. Side and ventral vrew Hares�eeras natroense cast of USNM 1314S6 3.1 cm aaoss

lett Side and edge view HaresK:eras placentfforme cast of USNM 131483 2.6 an aaoss

72

Ammonites and the other Cl'piUJlopotb of IM Pierre Seaway

'..�

FAI'III. V S CAI.IIITIDAE

Genus Hoploscaphites hoplo

=

Nowak, 1 9 1 1

heavily anned foot soldier + skaphe = boat + ites = a �Lone

Hoploscaphites is small to medium sized for the family with compressed or flattened shells, tightly coiled ( involute) pbragmocone.

hallow umbilical walls. a shon. slightly curved body

chamber, and a lightly recurved hook. Ribs tend to be th.icker on the phragm.ocone and become more dense and fme on the body chamber, often bifurcating and bending back (rursiradiate) toward the phragmocone at rnidOank. Small ventrolateral tubercle are often present on the body chamber and

Hoploscaphite� eems to have its origin in Baculites obtusus Zone of Greenland and continues through the Jeler:kytes nehrascensis Zone of the Fox Hi I I Fonnation. Hoploscaphires i present in the Campanian and Maastrichtian of North may or may not be pre ent along the umbilical margin.

the

America and Europe.

Hoploscaphites gilli (Cobban

and Jeletzky, 1965)

Hoploscaphttes g

Left: BHJ 4116 (macrooonch) 5 em high

Right BHI 41 1 7 (I'TliCIOCOflCh) 4.5 em hiQh

Hoploscaphires gilli is a small- co medium-sized scaphitid (up to 41/2 em) that occurs in the Baculites perplexus th.rough the Didymoceras nebrascense Range Zones within the Pierre Shale. The shell i compre

ed (having a narrow whorl ection), and the body chamber is broad and large

and loosely coiled around the phragmocone in the macroconch. The microconch has a longer, straighter body chamber that eparates lhe phragmocone from the recurved book. The umbilical

walls are tapered and hallow. flanks are flat to semirounded, and the venter is very rounded and

blends into lhe flanks. The rib are more coarse on the phragmocone but become very fi ne and dense on the body chamber. Ventrolateral rubercles may be pre.em but are u ually absent. Macroconchs of the species tend to have a much \\rider flank and an umbilical swelling on the body chamber and are about 25 percent larger than the rnicroconch . 73

���b

FAMII.Y SCAt"HITIOAE

Hoploscaphites Landesi Riccardi, 1 9�3 This species ha. a relatively small shell (2-3 em). It is involute on the phragmoconc, with the body chamber extending slightly beyond the phragmocone, leaving only a slight gap near the

Hoploscaphttes IandeS/

Left: BHI 4118 (macroconch) Rtghl BHI 4119 (microconch)

Left: BHI 4118 (macrooonch) 4.2 an high Right BHI 4 1 1 9 (microoonch) 3.5 an high

aperture. Ribbing is coarse on the pbragmocone and becomes finer and more dense on the body chamber. There arc light bullae or tubercle along the umbilical margin and on the ventrolateral shoulder of the last part of the phragmocone and fJISt half of the bod} chamber. The macroconch is distinguished by its slightly larger size. wider flanks, and a light swelling above the umbilicus on the early part of the body chamber. Hoploscaphites landesi ha been found throughout the Western Interior Seaway in the upper part of the Didymoceras cheyennense Zone through the Baculites

c:uneatus Zone.

Hoploscaphites melloi Landman and Waage.

1993

This is a moderately sized shell with fine dense rib on all or most ofthe body chamber. Tts ventral ribs are also very fine and dense. Ribs tend to curve away from the bod} chamber along the umbilical margin, bifurcate, and bend back toward the body chamber. then at two-thirds the distance aero nank, they bend back toward the phragmocone. Thi

pccie i

the

'eT) compressed and similar to

Hoploscaphites nicolletii from the Fox Hills Formation. There are few or no 'entrolateral tubercles

and none around the umbilical margin. MicroconciD. are commonly one-half to rwo-thirds the i.le of the macroconch and have more promi­

nent ornamentation and a more e\.oJure um­ bilicus. The pede has been reponed in the upper part of the Mobridge Member of the Pierre Shale in north central South Dakota.

Hopioscaphltes meJioi {macroconch) BHI 4120 4 an high 74

Ammorllll'S and tht> orl�r Ct>phalopod.s ofw Pit>rrr Sl'Ol\ay

1 _••

FAMI LY SC API IITIDAE

Hoploscaphites nicolletii (Morton.

1 842) var.

saltgrassensis (Eiiao;. 1 933)

Eliru. figured and de cribed this variety from phragmocones and other fragments that he collected from the Pierre Shale in Wallace County. Kan ru., along with another scaphite, Jelet�J...yTes plenus. Recently identified specimens from the Pierre Shale in Daw on County. Montana, not only extend their range, but also give us some complete specimen for de cription. This is a moderately sized (up to 8 em). compressed, finely ribbed conch. The phragmacone tends to have prominent, straight primary rib , with secondary ribs between them. The body chamber U. lightly more inflated than the phragmocone with a trong recurved hook and prominent ventrolateral tubercles for nearly the entire length. The ribs of the body chamber are fine and become more dense toward the aperture. Hoploscaphltes niCOIIeiJI var saltgrassensis (macroconch) BHI 4705 8.5 x 7.5 cm Pholo courtesy ol Dr. Nell Landman

Hoploscaplzites birkelundi

Landman and Waage, 1993

The she11 is very compressed with a .trong recuned hook. The ribs are broad and low on the pbragmocone. becoming narro\\-er and more den e on the body chamber. Ventrolateral tubercle. start on the body chamber near the phragmocone and usually quit when the body chamber curve back toward the phragmocone. Some macroconchs and most microconchs have umbilical bullae. A with all HoploscaphiTe'i. the umbilicu i very involute. This species occurs with JeleT: :.kyzes dorfi. but to date bas only been found in the Fox: Hill Formation of Niobrara County, Wyoming. The pecie hould. however, occur throughout the Upper Pierre Shale above the BaculiTes clinolobarus Range Zone.

Hopioscaphites birlcefund• (maaoconcfl) left YPM 27170 6 x 4.7 em RJQht YPM 211 n 6.3 x 5.5 cm Photos counesy of Dr Nell Lanoman

75

FAMII.Y SCAI"IIITIDAE

.

Genus Jeletzkytes

�:

Riccardi, 1983

after J. A. Jele11.ky + ites = a stone

Jeletzkytes can occur as mall to large, moderately i nflated conchs. The phragmocone is involute and the body chamber has a short shaft that extends slightly beyond the phragmocone with a weak reeurved hook. The ribs are sparse and straight on the phragmocone but tend to bifurcate and bend slightly on the body chamber. There arc prominent ventrolateral nodes begiru1iog on the phragmo­ cone that fade away near the aperture on the body chamber. Most species also have at least another row of tubercles around the umbilical margin or extending midway on the tlank. Some species may also have two to three additional rows of tubercles on the flank starting on the phragmocone and fading away on the body chamber. The genus

Jeletzkytes eems to first appear in the Baculites

obtusus Zone and is present throughout the Maastrichtian. Fox Hills Formation, the last of the Cretaceous marine sediments in the Western Interior. l l i

found in Campanian and Maastrichtian

marine sediments in Europe and North America.

}eletzkytes nodosus

(Owen.

Jeletzlcytes nodosus Left. BHI 4121 (macrocondl) 9 em tugh

R1ght BHI 4122 (miCI'oconch) 7 em hiQh

1 852)

Ventral view left: BHI 4121 Right BHI 4122

Jeletzkytes nodosus is comparatively large for this family (up to I I em). This species is quite robust with a somewhat long haft on the body chamber and a moderate recurved aperture or hook.

The umbilical walls are well rounded to steep. Ribs are broad. prominent, and fairly straight with some bifurcation and bending. The most distinguishing characteristic for Jeler:.kytes

nod.osus in

microconch and macrocooch forms i its narrow, lightly rounded flank and a broad, rounded venter.

The whorl section is more robust than any other caphitid

except for Jeled:ytes crassus and Rhaeboceras subglobosum from the Pierre Seaway. Jelet:}cyres nodosus i further di tinguished

from other species by a prominent row of tubercle along the ventrolateral houlder and another near

the middle to the dorsal edge ofthe flanks. The venter width and the flank width at midbody chamber are of nearly equal size. Microconch and macroconchs differ primarily in the size and robustness of the body chamber. with the microconchs omewhat compre sed or narrower along the venter.

Jelet:kytes nodosus range from the Didymoceras cheyennense through the Baculires ctmeatus Range Zones. It has been found throughout the Western Interior Seaway and the Upper Campanian of the Gulf Coast. 76

Ammonites and tM olhu Ct>phtJfopod5 ofIM Ptt'Trt' St'tn.tl)

"!,

FAMILY SCAPIIITIDAE

]eletzkytes brevis

(Meek, 1 876)

Jelet-;.kytes brevis can have small to large shells (up to I 0 em) that are somewhat compressed to well rounded and inflated. The body chamber has a short shaft and a recurved hook that extends

slightly below the phragmocone. Ribs are thicker on the more robust forms and fmer and sharper

on the more compressed varieties. The ribs tend to bifurcate but remain fairly straight and prominent.

The ventrolateral shoulder has a prominent row of tubercles that begins on the phragmocone and can extend the entire distance of the body chamber. A second row of tubercle lie on the flank above the rounded umbilical shoulder to one-third of the distance on the flank. The flanks of Jeletzkytes

brevis tend to be only slightly rounded and quite wide compared to the narrow flanks of JeleiZkytes nodosus. Jeletzkytes brevis also is more compressed than Jeletd
a more flattened venter. The nank width is about 1 112 Limes the diameter of the venter at midbody

chamber. Microconchs tend to be about one-half to two-thirds the size of the macroconehs and much

more compressed. The pccie is found from the Didymoceras cheyennense Range Zone through the

Baculites reesidei Range Zone. JeletV.ytes brevis is common from Colorado through Alberta.

Jeletzkytes breVIs (2 111ews) Left: F47 BHI 4124 (macroconch) 8.5 em high Right: BHI 4123 (microconch) 6.6 em hrgh

77

,·�;

F AM II " SCAt"HITII>AI:

}eletzkytes "quadrangularis " (Meek and Hayden.

1 860)

(invalid species) This variety of Jeletzkytes has a small- to medium-size range, a nearly nattened venter, and somewhat compressed whorl section. Riccardi ( 1 983) assigned two ofthe paratypes and the holotype of this species to the microconch of Jelezkytes cf. brevis. However, the holotype appears to be a microconch ofJeletzkytes criptonodosus and one paratype appears to be a microconch of Jelerzkyres plenus. The pararype of Jeletzkytes plenus, from the Yellowstone River area, does appear to be a mieroconch of Jeletzkytes brevis. The um­ bilical walls are narrow and steep, and there is a row of nodes directly above the wal ls on the umbilical shoulders. There is another row of tubercles on the ventrolateral shoul­ der that usually starts where the body cham­ ber begins. Tbis "species" hac; been de­ scribed from microconchs only of other known species and should not be consid­ ered a distinct species. Je/etzkytes "quadrangularis " occurs with Jeletzkytes nodosus and Jeletzkytes brevis in the Didymoceras clzeyennense Range Zone through the Baculites cuneatus Range Zone. Side and Ventral view Jeletzkytes quadrangularis paratype

USNM 365 (actually Jeletzkyles plenus) 6.8 cm high

Jeletzkyles quadrangularis paratype

Ventral and Side view Jeletzkytes quadrangu/aris holotype

USNM 366 (actually Jeletzkytes brevis mK:roconch) 5.5 em high

USNM 366 (actually Jeletzkytes criptonodosus miCroconch) 5.5 em high

Side and Ventral view

78

Ammon/res and rhe nrlrer Cephalopods ofrhe Pierre Seaway

'<ell�-

FAMII.Y SCAI"HITIDAE

Jeletzkytes ''furnivali" Riccardi,

1 983

(doubtful species)

Jeletzkytes "fumivali" has flexuous ribs and a compressed whorl section that is subrounded to subrectangular. The bolotype of the species appears to be a m.icroconcb, but Riccardi did not assign a macroconcb to the species. This makes assignment as a distinct species doubtful . The authors feel thatJeletz/...ytes "fumi vali" is possibly a m.icroconch for an ac; yet undescribed Jeletzkytes macrucunch from the Baculites reesidei Range Zone. Tt has a short shaft extending just below the phragmocone and curving strongly back, leaving it slightly more open than Jeletzkytes brevis. The umbilical wall is curved and shows no swelling, flanks are flat and parallel, and the venter .is flat on the phragmocone to rounded on the body chamber. Rib tend to be Lhick and bifurcate on the phragmocone and on much of the body cham­ ber, but become finer as they near the aperture. A ventrolateral row of tubercles runs along the shoulder from the last part of the phragmocone to nearly the end of the body chamber where the tubercles become smaller. There is a row of nodes or small bullae that begin nearly at midflank on the phragmocone and move in just above the dorsum at the aperture. Riccardi tated thatJeletz/...ytes "furnivali "occurred from the Baculites compress us through the Baculites S1de and Ventral VIeW reesidei Range Zones of the Pierre Shale and Jeletzkytes fumivaliHolotype GSC 67093 age-equivalent rocks. 8.5 cm high

]eletzkytes crassus (Coryell and Salmon,

1 934)

This species of Jelet:J..ytes is the most robust and well rounded of all the species. It is also quite large (up to 1 2.5 em). The body chamber has a short shaft that quickly bend� back on the phragmocone. The venter is very wide and broad, almost as wide as the flank. The species has a steep umbilical wall and ijghtly rounded flanks. The ribs are bifurcated, prominent, and remain fairly straight. The ventrolateral shoulder has a row of small tubercles that arise early on the phragmocone and end at the aperture. There is also a row of nodes above the umbilical shoulder beginning ear1y on the phragmocone but fading out on the body chamber. The macroconch bas a large welling near the umbilicus on the early portion of the shaft. Microconchs are quite wide across the venter with narrow, slightly rounded flanks. and Side view Jeletzkytes crassus Left: BHI 4125 (maeroconeh) 9.7 em high Right: BHI 4126 (mieroconeh) 6.3 em high

79

q:

FAMILY ScAt•HITIUAt:

}eletzkytes crassus continued are ornamented with large, prominent tubercles. They are only one-quarter to one-half the size of the macroconchs. The maximum width of the venter is so wide, it is even wider than the flank width at the midbody chamber. Jeletzkytes crassus occurs commonly in the Baculites eliasi and Baculites

baculus Zones and equivalent rock units of the Pierre Shale from Kansas through Alberta and Saskatchewan. Jeletzkytes crassus

Side and venter view left: (macroconch) 10.2 across x 10.5 em high Right (microconch) 3.5 across x 6.6 em high Jim and Joyce Grier collection

]eletzkytes plenus ( Meek and Hayden,

1 860)

Jeletzkytes p/enus is a robu t pecies characterized by its steep umbilical wall, weU-rounded venter and llank.s, and large size (up to 1 1 em). This species bas fairly traigbt. medium to fine ribs that tend to bifurcate about two-thirds of the way out on the flanks. Tt also has small tubercle on the ventrolateral shoulder quite early on the phragmocone that continue almost all of the way to the aperture. There is an inner row of small lateral node or bullae above the umbilical shoulder that begin early on the phragmocone, but fade away on the body chamber. Occasionally, a third row of small tubercles is located rnidflank. on the body chamber. The microconch for tbis species is slightly compressed in whorl section, has flat to subrounded flanks, and is ornamented by small tubercles on -

�r

�

; �

�

' ·

.��

�- . :· F r

Side view Je/etzkytes plenus Left: BHI 4130 (macroconch) 8.5 em high Right: BHI 4129 (miCroconch) 5.6 em high !10

Ammonites and the other Cephalopodf of 1he Pierre Sea11.·ay

....

, .

'

�

,I

.1.

)

Ventral view Jeletzkytes plenus left: BHI 4130 Right: BHI 4129

" ·..,,

FAMII.Y SCAI"IIITIDiU':

]eletzkytes plenus continued the ventra] shoulder and above the umbilical shoul­ der. Macroconchs are broader across the venter than

.Jele1zkytes criptonodosus. but less robust than Jeletzkyres crassus. The fiank width is only slightly wider than that of the venrer.

The size ratio for

microconch to macroconch is about one to 1 wo or one

Jeletzkyles plenus is found in the upper part Baculites eliasi and Baculites baculus Range Zones. to three.

of the Pierre Shale. primarily in the

Jeletzkytes p/enus

(macroconch) BHI4128 10 cm across

]eletzkytes criptonodosus Riccardi,

1 983

This species is a medium-sized conch (up to 9 em) similar to Jeletzkyres brevis, but differs by sparser. more irregular ribbing, more complex suture pattern, and the presence of tubercles on the innermost whorls of the phragmocone. The umbil ical wall is steep to rounded with weakly curved to flat flanks and a broadly rounded venter. The lateral ribs are strong, rounded, and tend to pair from the lateral tubercles above the umbilicus toward the ventrolateral tubercles above the venter. Ribs tend to be very straight on the phragmocone to slightly curved on the body chamber. The venter to flank ratio follow that of Jeletzkytes brevis, being about

1 to 1 112 at midbody chamber. Macroconchs

Side VIew

Ventral view

Jeletzkytes cnptonodosus

Jeletzkytes criplonodosus

Left: BHI 4131 (macroconch) 7.8 em high Right BHI 4132 (miCroconch) 5.2 em high

Left: BHI 4131 Right: BHI 4132 81

"· ··

FA Mil. v ScAI"HJTJDA E

_ _

jeletzkytes criptonodosus continued arc large and compressed likc Jeletzkytes brevix, whereas the microconchs are small and compressed with much broader ribbing and larger ventrolateral tubercles, and are one-half LO one-third the size of the macroconchs

.

.leletzkytes criptonodosus

occurs primarily in lhe Baculites baculus Zone, but si rnilar specimens have been found as low as the

Baculites cunearus Zone.

Type Jeletzkytes crlptonodosus holotype GSC 67104 8.6 cm high

}eletzkytes dorfi

Landman and Waage,

Side v1ew Jeletzkytes dorfi Left: BHI 4133 (macroconch) 7.5 em high Right: BHI 4134 (microconch) 5.3 em high

1 993

Ventral view Left: BHI 4133 Right: BHI 4134

This species is of medium ·ize for the genu ( between 7 and 8.5 em for macroconch size). The shell is somewhat com pre sed, with a long tapering body chamber and a high apertural angle on the recurved hook. The umbilical wall is short and teep with slightly rounded flanks and an almost flat venter. Ribs arc strong and sparse on the phragmocone, becoming closer and finer near lhe aperture. lt has many closely spaced ventrolateral tubercles. and there is another faint row of tubercles above the umbilical margin to one-third of lhe distance of the flank.

The venter is rounded on the

phragmocone to fiat on the body chamber. The microconch for Jeler::,kytes dorfi is about one-half the size of the macroconch, with broad, widely spaced ribs, a compressed whorl section, and prominent tubercles along the ventral shoulder with minor tubercles on the umbilical region.

Jeler::,kytes doifi occurs above the Baculites clinolobatus Zone, in the Jelet;}..ytes dorfi Zone east of the Black Hills, and in lhe lowermost Fox Hills Formation, just west of the Black Hills in Wyoming.

82

Ammonites and the other Cephalopods of 1h� Pierre Seaway

. -c

FAMILY SCAPIUTII>A"

Genus Ponteixites

Warren. 1934

Ponrei.x = town in Saskatchewan

+

ites = a Mone

Ponteixites appear to be the dwarfed Maastrichtian descendant of the Campanian Rhaeboceras. Ponteixites is quite small and compressed in whorl cross section. lt hac; a slightly rounded, narrow umbilical wall, somewhat evolute, slightly rounded to flat flanks, and well-rounded yet narrow venter. The ribs are prominent, sparse, and well-rounded, with an average of two secondary ribs for every primary rib. The suture pattern is the same as for all scaphitids when the same-size specimens are compared. This genus is found only in the Maac;trichtian of the Western Interior.

Ponteixites robustus Warren, 1 934 Of the two described species, Ponteixires robustus is the more robust, both i n whorl section and in having broader, more prominent ribs on the flanks and on the venter. The umbilicus is moder­ ately evolute ( loosely coiled). Ponteixites mhustus tends to have straight to slightly bent primary ribs and a secondary rib for each primary one begin­ ning about the middle of the flank. The umbilical walls are shallow, and the flanks are slighlly rounded. Complete mature Ponteixites robustus

have a maximum diameter of 5.5 em. Ponteixites

robustus occurs i n the Baculites baculus and

Side and ventral view Ponteixites robustus BHI 3044 4 em across

Baculites eliasi Range Zones and is found in Montana, Wyoming, Alberta, and Saskatchewan.

Ponteixites gracilis

Warren, 1934

Ponteixites gracilis seems to be consistently smaller ( 1 .4 em to 2 em in diameter), more compressed, and slightly more tightly c o i l ed ( i nv o l u t e ) than Ponteixite.\'

robustus. The umbilical walls are also more shallow and the flanks contain a greater number of both primary and sec­ ondary ribs. The venter is wel l-rounded and has broad prominent ribs. This spe­ cies may actually be the microconch for

Ponteixites robustus since both occur in the same Range Zones and localities.

Side and ventral view Ponteixites gracilis BHI 628 2.2 em across 83

FAMILy SCAt"HITII>AE

.

Genus Rhaeboceras rhaibos

=

bent

Meek, I R76

+ ceras =

born

Rhaeboceras is a cap hi tid of medium to large size with involute inner whorls and a more loosely Ptwhydiscus. The whorl

coiled body chamber. The phragmocones tend to resemble finely ribbed

section is rounded to slightly compressed. The umbilical walls arc steep, the flanks arc slightly rounded, and the venter is very well rounded. Straight to slightly curved. bifurcating ribs are present on the flanks, and the venter has broad straight ribs. Tubercles may or may not be present above the umbilical margin and above the venter of the body chamber. The development of tubercles may help determine the gender (macroconch, microconch) of the ammonites. The genus Rhaeboceras may be limited to the Western Interior of North America.

Rhaeboceras halli

(Meek and Hayden. l 856)

Rhaeboceras halli is a fairly small (up to 1 5 em) and compressed variety of the genus. Its ribs are fine and closely spaced; some bifurcate about halfway up the flank with several frne secondary ribs arising in between the straight ones within the middle third of the flank. Tubercles or clavi may occur above the umbilical margin near the end of the phragmocone and on the body chamber. This species occurs infrequently in the upper part of the Pierre Shale, but is most common in tbe Baculite.\'

reesidei and Baculites jenseni Range Zones of Montana.

Side and ventral VIew Rhaeboceras halli

BHI 3044 14 em across

84

Ammonites a11d rite other Cephalopods ofthe Prerre Seawa)

·._;1;.

FAMILY ScAYHITIOAE

Rhaeboceras albertense (Warren.

1930)

Rhaeboceras albertense is a medium-size conch for the genus (up to 18 em), with an ovate to subrectangular whorl section and steep almost vertical umbilical walls. The whorl section near the end of the body chamber becomes nearly as wide as it is high. It differs from Rhaeboceras haiti by its straighter, coarser, and broader ribs, and also by its very prominent secondary ri bs that begin on the middle third of the flank and extend over the well-rounded venter. As in Rhaeboceras halli, tubercles or clavi may be present along the umbilical margin of the body chamber. The species occurs in the Baculires reesidei and Bacu/iresjenseni Range Zones in the Pierre Shale and its equivalents, primarily in Montana. Alberta, and Sa�katchewan.

Side and ventral view Rhaeboceras albertense

BHI4136 14 em across

Rhaeboceras subglobosum

(Whiteave , 1 885)

This specie is the large t (up to 30 em) and the most robust of the Rhaeboceras. The whorl section is almost round, the umbilical wall are very steep, and the tlanks and venter are very rounded. Broad, straight, primary, and secondary ribs decorate the t1anks and venter. There appear to be no tubercles or clavi. Its suture pattern is also the most com­ plex of all the Rhaeboceras.

The

species occurs primarily in the

Baculires reesidei and Baculire.\ jenseni Range Zones of Montana. A lberta, and Saskatchewan. Side and ventral view Rhaeboceras subglobosum

BHI4137 1 1 em across

85

-·

FAI' tii. Y Sc :AYHITIDAt:

Rhaeboceras coloradoense Cobban.

I 987

This species was assigned as the "noded" variant by Cobban when he wrote the description of the species. Out of all the species within this genus, this one has the most typical look of a scaphite. The species has a row of tubercles on the body chamber above the umbilical margin. It also has flattened flanks and a rather compressed cross ection. The ribs are prorsiradiate, flexuou . high. rounded, and evenly spaced. There are also secondary ribs in between the primary ribs on the body chamber. The species has been found in the Pierre Shale in the Baculites jenseni Range Zone in Colorado. and the Baculites eliasi Range Zone of Dawson County, Montana.

Side and ventral v1ews Rhaeboceras coloradoense

USNM 413046 4.5 em across

Side and ventral views Rhaeboceras coloradoense Holotype USNM 413044 8.2 em across

Rhaeboceras burkholderi Cobban,

1987

Rhaeboceras burkholderi is defined by a compressed cross section, flattened flanks, and a slightly flattened venter that is bordered by buUae. The ribbing i prorsiradiate and slightly flexuous, with the pri mary and secondary rigs giving rise to the bullate tubercles on the ventrolateral shoulder. The species is somewhat smaller than the other pecies, though only slightly smaller than Rhaeboceras coloradoense.

The

specie has been found in both the Pierre and Bearpaw Shales from the Baculires

reesidei through the Baculites eliasi Range Zones in Saskatchewan and Montana.

Side and rear view

Rhaeboceras burlcholden holotype

USNM 413047 5.7 em across

X6

Ammunitel and the other CephalopodJ of the P1erre Seaway

FAMILY SCAPIIITIDAE:

:'

,

Rhaeboceras mullananum (Meek and Hayden,

1 862)

As Cobban ( 1 987) notes on Rhaeboceras, the species was collected by Meek and Hayden about 20 odd miles beneath Fort Benton, Montana, which places it in the Santonian Age, Marias River Shale. That would make this specimen the earliest Rhaeboceras discovered. The form appears to be much later than Santonian and should be from the Campanian rocks of Montana. but only one specimen of this species (the type specimen) has been found to date. The authors believe that it came

from the Bearpaw Shale, o we felt obligated to include it in this publication.

Side and front view Cast of holotype Rhaeboceras mul/ananum

USNM t924 7.2 em across

!!7

•

FAMILY SCAPIIITIOAE

Genus Scaphites skaphe

:::

Parkinson. 1 8 1 1

a boal + ires = a

slone

This genus is described a being either compressed or robust. The phragmocone coiling is involute; the body chamber shaft may be either hon or moderately long, but it is not curved over the phragmocone. The aperture is somewhat constricted and u uaJJy has a long dorsal lappet. Ribs are generally recti radiate and branch or become intcrcalatory on the phragmocone. Tubercles on the umbilical and ventral shoulders are normally present on the body chamber. This genus has a worldwide distribution.

Scaphites hippocrepis Scaphites htppocrepts I

Left: Macroconch USNM 160280 Above: Microconch USNM 160271

Scaphites hippocrepts II

Left: Macroconch USNM 160297 Above: Microconch USNM 160292

Scaphites hippocrepis Ill

Left: Macroconch USNM 160331 Above: Microconch USNM 160308

88

Ammonites and rlre other Cephnlnpods ofthe Pierre St>01my

(DeKay, 1 827)

Scaphires hippocrepis is found in the up­ permost part of the Niobrara and in the lower part of the Pierre Shale, in the Eagle Sand­ stone, in the Cody Shale, and i n the Telegraph Creek Formation. Cobban ( 1 969) assigned the Roman numerals I, II. m to de ignate three subspecies. They are scaphitids of a small to below average size ( 1 - 1 112 in.) with a very loosely coiled body chamber simi lar to the earlier Turonian Age scaphites from the Carlile Fonnation. All types have prominent ventral ribs and sparse lateral ribs. They have ventrolateral tubercles on the body chamber and some near the umbilicus. Scaphites hip­ pocrepis 1, from the Niobrara and lowermost Pierre Shale. has the fewest ribs and tu­ bercles; Scaphites hippocrepis l l ofthe Pierre Shale has more ribs and ventrolateral tu­ bercles; and Scaphites hippocrepis m, al o from the Pierre Shale. is even more densely ribbed, and ha'i umbilical and midflank tu­ bercle and ventrolateral tubercles that ex­ tend onto the pbragmocone.

FAMILY SCAPIIITIOAJ::

'

;x

Genus Trachyscaphites Cobban and Scott, trachy = rough + skaphe = boat + ites = a stone

1 964

This genus has a very ornate conch of small to medium size. A multitude of tubercles, clavi, bullae, and ribs decorate this shell from early on the phragmocone through the body chamber. The phragmocone is very tightly coiled (involute), and the body chamber is straight and separates from the phragmocone before it bends back at the aperture. There are as many as five rows of tubercles on the flank of the phragmocone and body chamber that decrease in size from the venter toward the umbilicus. Ribs arc straight, tend to join and go between the tubercles from both sides, and are spaced very tightly.

This genus is similar to the scaphitid, Discoscaphites gulosus, of the Fox Hills

Formation. Trachyscaphites is limited to the Campanian of North America and Europe.

Trachyscaphites pulcherrimus (Roemer,

1 84 1 )

Trachyscaphites pulchenimus resembles the description of the genus very closely. The whorl section i s compressed to rounded, and the umbilical walls are steep. There are five rows of tubercles on each flank; two rows of ventrolateral tubercles parallel each other, typically a row of tubercles above the umbilical margin and general ly one to two more rows of tubercles between these sets. The tubercles get larger and even disappear on the body chamber, and ribs tend to join these tubercles i n straight lines. Trachy­ scaphites pulcherrimus is more slender, slightly more involute, and has a less-extended body chamber than any other species of

Trachyscuphites. Trachyscaphites pulcherrimus occurs in the Baculites perple.xus and Baculites gregoryensis Range Zones of the Pierre Shale in Colorado, Wyoming, and South Dakota.

Trachyscaphites putcherrfmus BHI2148 3.5 em across

Side and ventral view Trachyscaphites pulcherrimus

Jim Schoon collection 4.1 em high

89

Trachyscaphites redbirdensis Cobban and Scoll, 1964 Traclzyscaphites redbirdensis is a large species of up to 1 1 em high by over 5 em thick on the venter. It has a lung straight shaft on the body cham her and a strongly retracted hook. There are five rows of nodes on each flank, all almost equally spaced. All of the nodes are prominent, but the ventrolateral tubercles are the largest.

The

umbilical nodes arc somewhat bullate in form. There is also a row of nodes on either side of the

Trachyscaphi t es redbirdensis occur in the Redbird Silty Mem­

center of the venter. ber of Wyoming. Side and rear view

Trachyscaphites redbirdensis Holotype USNM 132309

9.6 em across

Trachyscaphites spiniger (SchlUter, 1 872) subspecies porchi (Adkins, 1 929) This species is a moderately large conch that differs from others of the genus by having four rows of nodes on each flank. There are also two rows of tubercles between the ventrolateral tubercles on the venter. The form is stout and robust, with a long separated body chamber and a trongly retracted aperture. The pecies hac; straight to slightly flexuous ribs that tend to join and separate the tubercles.

The species has been reported from Germany, Ru sia. Sweden. and Belgium.

Trachyscaphires spinigerporehi described and figured here has been found in Texas, Mon­ tana, Colorado, and Kansas. Trachyscaphttes sptmgersubspecies porchi Left: Internal mold USNM 132320 4.4 em across Cen1er: Rear view USNM 132319 4.7 em high Right: Internal mold USNM 132324 4.5 em across

Trachyscaphites praespiniger Cobban and

Scon,

1 964

Trachyscaphires praespiniger differs from the other pecies of Trachyscaphites by having only three and rarely four rows of nodes on each flank. Generally only the rnidlateral row persists to the aperture on the body chamber. The specie i moderate to large in ize, ranging between 8.5 ·

..._.,...-

�

and 1 3 em high. It is moderately robust on the ventral ide. The body chamber does not separate from the

Trachyscaphites redbirdensis or Trachyscaphires spinigerporehi. The species has been

whorls as much as on

reported from South Dakota, Montana, Wyoming, Colo­ rado. and Utah. Trachyscaphites praespimger

Left: Hototype USNM 132333 7.6 em high R1ght: USNM 132335 7.2 htgh 90

Ammonites and the' other Cephalopods ofthl' Pierrl' Seaway

FAMILY SPHENODISCIDAE HYATT,

..."... ''-'! 1

1}900

This family consists of small to large species that tend to have very involute or closed umbilici. The shell is compressed, lenticular, and planispiral, with a sharp or narrowly rounded venter. Some genera possess weak lateral and ventrolateral tubercles, and faint ribs or swellings. Spheoodiscidae have been found on every continent except Antarctica, from the Upper Campanian through the Maa<;trichtian.

Genus Sphenodiscus Meek,

1 876

spheno = a wedge + discus = a disk The genus Sphenodiscus has been described as a smooth planispiral. lenticular-shaped shell with a closed or involute umbilicus. The flanks are wide and very broadly convex, and the venter is narTow and acute.

Some species show low. broad, widely spaced ribs (or undulations) an<.l occasional

tubercles in early forms. The suture pattern is fairly simple, with about eleven or twelve rather short, deeply eli vided lobes. The genus attains a size of 50 em in the Timber Lake Member of the Fox I-lills Formation, but rare I y gets larger than 15 em in the Pierre Shale. Macroconchs are considerably larger than the microconchs, which tend to have prominent ribbing or undulations. The genus has heen recorded from western Europe. the Middle East, lndia, Madagascar, Mexko, Vene;.uela, and the U nited States. A Gulf Coast species, called Sphenodiscus pleurisepta (Conrad, 1 H57), is occasion­ ally found in the Baculires clinolobatus and possibly the Jeletzkytes dorft Range Zones of the Pierre Shale.

Sphenodiscus pleurisepta BHI 4148 1 3 cm across

'

FAMILY St>ttENOOISCIJ)I\1.;

Genus Coahuilites

�

Bose, 1927

Coahuila - A state of Mexico The shell of

Coahuilites is disc-shaped with an involute umbilicus. rounded to irregular

flanks. <md two distinct rows of tubercle . One row of tubercles is located on the midOank and the other is on the ventral shoulder. The venter i characterized by a sharp keel early that changes to almost rooOike, and then becomes nearly flat in mature individuals. The genus has been found from northern Mexico to Redbird. Wyoming.

Coahuilites sheltoni Bose.

1 927

This species of Coahuilires is the mo t abundantly found within the genus. The suture pattern seems to be the most distnguishing feature between this and the other described species of

Coahuilites. Because it is the only specie that has been found within the Western Interior. we will not explain those differences. The species portrayal follow clo ely the explanation of the genus.

Coahuilites sheltoni has been found in northern Mexico (Coahuila), Texas, Colorado ('!). and within Haculites clinobatus Range Zone of Wyoming.

the

Coahurliles she/toni

USMN 32152 Left: Side view 14.9 em high x 17.1 em across Right Ventral vtew Photo courtesy of Dr. Nell Landman 92

Ammonite.� and tire other CephalopodJ of the Pierre Si'UWUJ

B

elemnites were closely related to the modern-day squid, but had an elaborate internal shell including a phragmocone that resembles that of straight, externally shelled nautiloids of the

Paleozoic Epoch. These animals were probably rapid swi mmers that looked and behaved much like

A Life Reconstruction of a Belemnite [dashed line indicates hard internal shell - see illustration below]

Illustrations by D.S. No'rton

extant squids. Their bodies were shaped like a

water in the same manner as in ammonites and

torpedo with two lateral fins that could steer the

nautiH. The order appeared in the Triassic, but

belemnite as it swam. Like the squid, it would

flourished throughout the seas of the world dur­

propel itself through the water by taking water

ing the Mesozoic Epoch, and died out in the

into its mantle cavity and force it out through an

Eocene.

organ called a funneL All representatives in this order had ten equal or subequal arms with bookJets. The belemnites' hard, internal shell

fAl'tiLY BELEMNITELLIDAE PAVLOW,

1913

consisted of a guard or rostrum, a phragmocone,

The shell consists of a pen-shaped calcitic

The rostrum

rostrum or guard that covers the gas and fluid

a siphuncle, and a proostracum.

and proostracum were composed of concentri­

chambers of the phragmocone.

cally layered calcite that radiates from the ven­

closely follows the description of the order,

tral surface.

The rostrum encompassed the

characterized by a large phragmocone and a

phragmocone and the proostracum provided a

rapidly tapering rostrum. Members of the Fam­

bard dorsal protection for the internal organs of

ily Belemnitellidae have worldwide distribution

the body.

in rocks of the Cretaceous and Cenomanian

The phragmocone bad a siphuncle

whose purpose was to fill the chambers with gas

The family

through the Maastrichtian.

or fluids to achieve neutral buoyancy in the

proostracum guard or rostrum

A Specialized Belemnite Cross Section with Unsectioned Proostracum

93

-:_::;,:;_,

F'AMII. y BI:LIOMI'IITELLII>At-:

Genus Belemnitella d'Orbigny. 1 840 belemnon

=

a dan + telos or tela

=

end

The genus follows the description of the order and the family very closely. However, there is a lengthwise slit on the ventral side of the rostrum and a flattened ridge on the dorsal side. The phragmocone is distinguished by a minute bulb or protoconch at the apex or tip. The genus occurs sparingly throughout the Upper Cretaceous of the Atlantic Coast, Gulf Coac;t, and the Western fnterior Basin.

Belemnitella bulbosa Meek and Hayden, 1 856 The rostmm is slender, subcylindrical, and slightly expanded at the anterior end.

It has a

moderately distinct dorsaJ ridge and a phragmocone. The phragmocone is as long or slightly longer than the rostrum, but is rarely completely preserved. Its final chambers are greater in diameter than the rostrum. The phragmocone tapers at an angle of20" with an oval cross section. The septal walls curve slightly forward on the dorsal side. The species i found occasionally in the Upper Pierre Shale and more abundantly in the Fox Hills Formation.

Belemnitella bulbosa BHI4142 9.4 em long phragmacone

94

Ammunile� and the orhu Cephalopods ofthl' Pierre Seaway

T

he Order Nautiloidea is distinguished by

Today's Nautilus prefer cool or moderate

a curved to coiled external aragonitic

water temperatures between l 5°C and 22°C.

shell containing a phragmocone and a body

Water temperatures of greater than 27°C can ki II

chamber. The phragmocone is segmented into

the nautilus (Saunders and Landman, 1 9R7).

traight septa and

Extant Nautilus also have a very low metabolic

sutures. The nautiloids had a thicker shell than

rate and may go for weeks without eating while

many chamber

by nearly

that of their relatives, the ammonites, which may

remaining capable of very rapid swimming.

have enabled them to withstand crushing at deep

These same characteristics probably held true

oceanic depths and pressures. The chambers are

for the nautiloids of the Cretaceous since today· s

all connected as in Ammonoidea and Belem­

Nautilus appears to be closely related to the Eutrephoceras of North America. This order

nitidea by a tube called a siphuncle that provided gas or fluids to the chambers. Nautiloids are and

has had worldwide distribution and has been

were relatives of the squid and octopi, and re­

found in rocks from the mid-Devonian Period

sided in a hard sbeU that provided protection for

through to the present. The continuing presence

mass.

a living fossil.

their sofl part a well as buoyancy for their body

of this order allows the paleontologist to study

Extant Nautilus inhabit oceanic coastal areas to a depth of approximately 300 m. At night, they move up to a depth of approximately I 00 m to feed, breed, and lay eggs. Cretaccou Age nautiloids ap­ pear to have inhabited water of 100 m or less during most of their l ifespan. Differences between extant and Creta­ ceous Age nautiloid appear also in their egg-laying ca­ pacity. Present-day Nautilus lay about 1 0 eggs a year whereas their ance tral cous­ ins laid smaller eggs, prob­ ably in greater quantity, esti­ mated at between I 0 and 50 eggs per year (personal com­ munication, Landman 1 994).

A Living (extant) Nautilus Illustration by D.S. Norton

95

FAMILY NA.UTILIDAE DE BLAI NVILLE, ; ""::!: ]! 825 , The Family Nautilidae is briefly described as having a generally smooth shell, which is involute to slightly evolute. The whorl section is slightly compressed. The siphuncle is located in the center (along the median line of symmetry), but may vary ventrally or dorsally within the chambers. The suture is straight to sinuou . NautiJidae are found from the Upper Triassic to the Recent and on every continent.

Genus Eutrephoceras

Hyatt, 1 894

eutrephas = nourishing + ceras = born The shell of Eutrephoceras is smooth and generally subglobose or nearly rounded. The whorl section is kidney shaped and broadly rounded on the flanks and venter. The aperture is slightly curved. The shell is involute and the suture pattern is slightly sinuous. The placement of the siphuncle is the primary characteristic for identifying species within the Pierre Seaway. This genus is present from the Upper Jurassic through the M iocene in North America and Colombia, South America.

Eutrephoceras alcesence

Ree ide, 1 927

Eutrephoceras alcesence has a broadly rounded, stout shell, globose in juvenile stages to subglobose in the adult stage. The whorl section is nephritic (kidney haped) and the placement of the siphuncle is central to dorsocentral . The surface of the shell has distinct longitudinal lines on the venter and coarse growth lines on the remainder of the shell. This species attained a l arge size, reaching a diameter of 24 em. The ratio of height to width in the cross section ranges from 6 to 7.

Eutrephoceras alcesence is present in the Eagle Sandstone of Montana, the Telegraph Creek Formation, and the Upper Cody Shale of the Big Horn Basin in Montana and Wyoming, the Steele Shale of east central Utah and New Mexico, and the basal Mesaverde Formation in the upper Rio Grande region of New Mexico. Another species, Eutrephoceras rhomi Reeside, 1927, ha<; been reported very sparingly from the Eagle Sandstone ofMontana, but the authors believe this is probabl y synonymous with Eutrephoceras alcesense, and that the differences are only dimorphic.

Eutrephoceras dekayi ( Morton,

1 834)

Eutrephoceras dekayi has a broadly rounded, subglobo. e shell that i s involute. The shell expands rapidly, more than doubling in size with each complete whorl. The height to width ratio of this species hao; been calculated at 3 to 4. The septa are reniform or k.idneyshaped and the siphuncle is located one-third to one-fourth the distance from the dorsum or the inner wall. The shell surface of adult and medium-sized specimens is smooth with faint growth lines and s light longitudinal furrows or costae. The species is recorded from the Atlantic Coast, the Gu If Coast states, and the Pierre Shale and marine equivalents of the Western Interior from the Scaphites hippocrepis through the Baculires compressus Range Zone .

Side view Eutrephoceras dekayl BHI4152 3.5cm high

96

Ammrmires and rilt other Cephalopods of rile Pierre Seaway

Venter view BHI4151 6.5 em across

""f�

FAMILY NAUTILIDAE

Eutrephoceras "elegans" var. nebrascensis (Meek and Hayden, 1 862) The description for

Eutrephoceras "elegans" var. nebrascensis is a subglobose shell, broadly

rounded on the flanks and venter. The umbilicus is closed in young and medium-sized specimens, and the shell is involute at larger sizes. The whorl increases rapidly in size with about the same dimensions in width and height. The height to width ratio is 3.5 to 3 . The suture has a slight curve bending forward ncar the umbilicus, slightly backward on the sides, and slightly forward on the venter or periphery. The surface of the shell is smooth with distinct lines of growth and slight longitudinal costae. The placement of the siphuncle is about one-third the distance from the outside

Eutrephoceras "elegans " var. nebrascensis has been noted from the Didymoceras cheyennense through Baculites eliasi Range Zones and appears to be prolific within the Baculites compressus and Baculites cuneatus Range Zones of the

periphery.

Western Interior of North America. lieve

The authors be­

that

the

variety

nebrascensis should be el-

l

evated to species status. The species elegans is an English Cenomanian stage

Nautilus

of a different subfamily and Left: Side view Eutrephoceras •elegans• var.

BHI 4154 6.5 em

Right: Venter view

high

nebrascensis

BHI 4153 4 em across

Eutrephoceras dekayi var. montanaensis

genus that does not occur i n t h e Upper Cretaceous of North America.

(Meek,

1 876)

Eutrephoceras dekayi var. montanaensis has a subglobose, smooth shell. Whorl width does not generally increase as fast, allowing the height to be slightly greater than in the earlier forms. Tn this species, the height to width ratio is

4 to 3.5. Meek ( 1 876) believed that this variety should be a

separate species and the authors agree with this diagnosis. The p lacement of the siphuncle near the center of the cham­ bers is the most distinguishing feature of

Eutrephoceras dekayi montanaensis is most abundant within the Baculites baculus Zone, but this nautiloid.

var.

also appears slightly earlier and may range into the early Fox Hills Formation.

Eutrephoceras dekayi var. montanaensis

BHI4156 5.6 em high

Eutrephoceras dekayi var. montanaensis

BHI 4155 11 em high

97

·-�

FAMILY NAUTILIDAE

,

Eutrephoceras dekayi

Eutrephoceras alcesence

Eutrephoceras "e/egans" var. nebrascensis

Eutrephoceras dekayi var. montanaensis

Siphuncle Placement in the

Pierre Shale Nautiloids 98

Illustrations by D.S. Norton Ammonites and the other Cephalupotb of the Pierre Seaway

0

rder Teuthldea, the squidlike coleoids, is characterized by a reduced, inner shell that lacks a phragmocone. Young individuals of these recent and fossil coleoids have vestiges of

phragmocone-like septa that lack a siphuncle. This proostracum forms the principal part of the commonly calcified horny exoskeleton or gladius of the coleoid that has a spoon like or rounded shape at its anterior end. The preserved gladlus consisted of a hard, inner shell on the dorsum or top of the squid that served as a protective plate for the soft internal organs. The Teuthidea have wings or fins that vary in size and shape and are found protruding from the dorsal parts of the proostracum.

Fossil and extant teuthlds have four arm pairs and a pair of tentacles, although the fossil teuthids

and some recent forms sometimes lack hooks and have suckers, or suckers and feelers, on their tentacles. Today's squid, which inhabit coastal waters, are the d i rect descendants of earlier coleoids. Order Teuthidea has been found from the J urassic Age to the present.

FAMILY KELAENIDAE

N;�, , ·

-· �

(see Jeletzky, 1 966)

The Family Kelaenidae has a simple characteristic shape described thus: "the end of the pen is narrow and forms a guard and the posterior end is enlru·ged to form a gladius that spreads out lateraJJy into the conus·• (Jeletzky, 1 966). The Family Kelaenidae occurs worldwide from the Middle Jurassic through the Upper Cretaceous.

Genus Tusoteuthis ruso =

Logan, 1 898

? + reurhis = squid

According to Kru·J Waage (personal conm1Unlcation, 1 994), the genus follows the description of the family, but differ · greatly from the original Kelaeno ( Jurassic). Tusoteuthis is found within the Baculites ohtusus through the Baculites perplexus Range Zones of the Western Interior. Three specimens of a new species, and possibly a new genus. that have been reported from the Wasta, South Dakota area, originate from the

Baculites compressus through the Baculites reesidei Zones of the

PietTe Shale.

Tusoteuthis sp. BHI4138 21 e m long

99

�.

FAMII.Y KEI.AENIOAE

Tusoteuthis tonga

Logan, 1 898

(see also Nicholls and lsaak. 1 987) The gladius of Tusoteuthis longa is shaped like a spear point dirccLed Loward the posterior end of the animal. The shell is composed of fibrous radiating calcite in the conus, rhachis, and gladius. The rhachis converges in the shape of a pen with the point extending about halfway onto the gladiu . The conus is represented by a V-shaped anterior end and a broad rounded swelling over the posterior end of the glad ius. The rhaehis served as a guard over the mantle to provide support. The gladius acted as protection and support for the soft organs in the squid. The po tcrior end of Lhe gladius also formed a base for the steering fins. The species has been found in the Sharon Springs Member, the Gammon Ferruginous Member of the Pierre Shale in Wyoming, Nebraska. and South Dakota, the Pembina Member of the Pierre Shale i n southern Manitoba, and the Smokey Hill Chalk of Kansas.

proostracum

gladius conus

0 • •

..

•

�.

• • . -,

., • � .... �

Top View of Preserved Inner Shell

Tusoteuthis sp.

Drawn from BHI 4138 Illustrations by D.S. Norton

1 00

Ammonites and the other Cephalopotb ofthe Pierre Seaway

FAMILY TRACHYTEUTHIDAE NAEF,

_ -�

1 9 2:1

Trachyteuthids have a broad, sturdy, cuttlefish-like internal gladius that is strongly calcified and exhibits a knobby, dorsal texture. The gladius side and middle plates are curved and slightly offset, forming asymptotes; the coni (veins) are about one-half of the gladius length. The family has a worldwide distribution in the Jurassic and Cretaceous.

A Life Reconstruction of Actinosepia canadensis [hard internal gladius shown] See illustration below Illustration by D.S. Norton

Genus Actinosepia Whitcaves, aktinos

=

a ray + sepia

=

1 897

cuttlefish

Actinosepia canadensis Whiteaves,

1 897

Actinosepia has a broad, oval, arched gladius that is concave on the venter. The gladius expands forward like a fan from a rounded conus and reaches its maximum width at about one-third the length from the anterior end where it then remains nearly straight. Five longitudinal ribs radiate from the apex with the middle rib being the longest and the two outside rib being the shortest. The ribs project beyond the body of the gladius, giving the appearance of a duck's foot. The ventral side of the gladius is smooth and the dorsal view is ornamented with fme to coarse tubercles. Actinosepia canadensis is found in the Upper Campanian and Maastrichtian of Canada and i n the United States from Alaska

to Texas. The species has a length about 2 1 12 times the maximum width, or 1 8 to 30 em in adult specimen .

Gladius: Side view

Gladius: Top view

Actinosepia canadensis

Waage, 1 965 Illustration courtesy of Dr. Karl Waage 10 1

Didymoceras stevensoni Drawing by John A. Stacy

MACROFAUNA OF THE PIERRE SEAWA PHYLUM ANNELIDA

cf. Websteria sp.

Serpula cretacea

Micrabacia americana

Serpula marknwni

Micrabacia ? sp.

Serpula sp.

Tmchocyathus sp.

Omasaria sp. Diploconcha sp.

PHYLUM ECHINODERMATA Cla�s Echinoidea

PHYLUM ARTHROPODA Class Crustacea Order Decapoda Callianassa cheyennensis Dakoticancer overanus Diorariopus heartailensis Diorariopus dawsonensis

Order Cassiduloida Hardouinia raylori Order Spatangoida Hemiaster humphreysanus Hemiaster beecheri Order Cidaroida Eurysa/enia minima

Dromiopsis kimberlyae Ekalakia l.amberti Eom1midopsis cobbani Glaesnerella sp.

PHYLUM MOLLUSCA Class Cephalopoda Order Ammonoidea

Homo/apsis dawsonenss i

Anak/inoceras rejlexum

Homolopsis punctata

Anaklinoceras gordiale

Honwlop.1·is mendryki

Anaklinoceras sp.

Hoploparia bearpawensis

Axonoceras compressum

Hoploparia dawsonensis

Baculites aquilaensis

Hoploparia mickelsoni

Baculites haresi

Linuparus pustulosus

Baculites sp. smooth (Cobban)

Necrocarcinus pierrensis

Baculites sp. weak flank ribs (Cobban)

Necmt·arcinus davisi

Baculites obtusus

Necrocarcinus labeschei

Baculites mdeami

Notopocorystes (Eucorystes) eichhomi

Baculires asperiformis

Palaeonephrops browni

Baculites smooth species (Cobban)

Plagiophcha/mus sp.

Baculites gilberli

Protocallianassa russel/i

Baculites perplexus

Raninel/a oaheensis

Baculires gregoryensis

Rugafarius fredrichi

Baculiles reduncus

Sodakus tatankayotankaensis

Baculites scotti

Tetracarcinus subquadraws

Baculires sp. (new species)

Xanrhosia elegans

Baculites pseudovatus

Xanthosia elegans occidenralis

Bacu/ires crickmayi

Zygastmcarcinus griesi

Baculites rugosus

Zygastrocarcinus cardsmithi

Baculites corrugatus

Zygastrocarcinus mendryki

Baculites compressus Baculites compressus var. robinsoni

PHYLUM BRACHIOPODA Class Inarticulata Order Lingulida Lingula subspatulara

Baculites sp. Baculites cuneatus Baculites reesidei Baculites undatus Baculites jenseni

PHYLUM BRYOZOA

Baculites eliasi

Pyriporoid bryozoan

Baculires baculu.f

Mernbraniporoid bryozoan

Baculites grandis Baculites clinolobatus

PHYLUM COELENTERATA Class Anthozoa Order Scleractinia

Cirroceras conradi Coahuilites she/toni

103

Didymoceras cochleatum

Pseudobuculites natosoni

Didymoceras mortoni

Rhaeboceras subglobosum

Didymoceras tortum

Rhaeboceras coloradoense

Didymoceras binodosum

Rhaeboceras mullananum

Didymoceras cf. archiacianum

Rhaeboceras burkholderi

Didymoceras nebrascense

Rhaeboceras halli

Didymoceras stevensoni

Rhaeboceras albertense

Didymoceras cheyennense

Scaphites hippocrepis I

Scaphites hippocrepis II

Didymoceras sp.

Scaphites hippocrepis m

Glypwxoceras ruheyi Exiteloceras jenneyi

Solenoceras crassum

Haresiceras natronense

So/enoceras texanum

Haresiceras placentiforme

Solenoceras mortoni

Hoplitoplacemiceras cf. H. c:oe.\feldiense var. schliiteri

Solenoceras n. spp.

Hoplitoplacemiceras marroti

Solenoceras reesidei

Hop/oscaphites gilli

Sphenodiscus pleurisepta

Hoploscaphites landesi

Submortoniceras tequesquitense

Hoploscaphites nicolletii var. saltgrassensis

Trachyscaphites pulcherrimus

Hoploscaphite.1· melloi

Trachyscaphites redbirdensis

Hoploscaphites birkelundi

Trachyscaphites spiniger porchi

1eletzkytes rwdosus

Trachyscaphites praespiniger

Je/etzkytes brevis

Order Belemnitidea

Jeletzkytes quadrangularis

Belemnitella bulbosa

1eletzkytes cf. nodosus

Order Nautiloidea

Je/etzkytes Jurniva/i

Eutrephoceras aleesense

Jeletzkytes pienus

Eutrephoceras thomi

1eletzkytes crassus

Eutrephoceras dekayi

Jeletzkytes criptonodosus

Eutrephoceras "elegans " var. nebrascensis

1eletV...yres dorji

Eutrephoceras dekayi var. montanaensis

Menabites (Delaware/Ia) danei

Order Teuthidea

Menabites (Delawarella) vanuxemi

Actinosepia canadensis

Menuites oralensis Menuites port/ocki complexus Nostoceras aff. N. humile

Tusoteuthis tonga Class Gastropoda

Nostoceras aff. N. co/ubriformis Nos/IJceras monotuberculatum

Aceton cf. throckmortoni

Oxybeloceras sp.

Akera

Oxybeloceras crassum

Amuletum minor

Oxybeloceras meekanum Pachydiscus cf. oldhami

? sp.

Amauropsis ? sp.

Anchura nebrascensis ?

Pachydiscus arkansanus

Anchura haydeni

Puchydiscus catarinae

Anchura sublevis

Parapuzosia bradyi

Anisomyon borealis

Pachydiscus cf. hombyense

Anchura

? porva

Purasolenoceras pulcher

Anisomyon centrale

Placenticeras sancarlosense

Anisomyon pa.tellifonnis

Placemiceras guadalupae

Anisomyon subovatus

Placenticeras planum

Anisomyon alveolus

Placenticeras pingue

Anisomyon sexsu/catus

Placenriceras imercalare Plucenticeras meeki

Anomia sp.

Anomalofusus ? sp.

Placenticeras costatum

Astandes densarus

Pomeixites gracilis

Aporrhais biangulata

Ponteixites robustus

I 04

Acirsa (Hemiacirsa) n. sp.

Acmaea occidentalis

Ammonites and the other Cephalopods ofthe Pie"e Seaway

Alira ? nebrascensis fJel/ifusus ? n. sp. Belliscala ? n. sp. Bullopsis aff. B. crelacea Bullopsis n. sp. Capulus spangleri Cerilhioderma n. sp. Cerichiopsis (Cerithiella) n. sp. Closteriscus lenuilineatus Cryplorhylis cheyermensis Cryptorhytis flexicostata Cylichna cf. secalina Cylichna cf. incisa Cylichna sp. Drepanochilus evansi Drepanochilus scotti Drepanochilus nebrascensis Drepanochilus obesus Drepanochilus sp. Ellipsoscapha occidentalis Ellipsoscapha subcylindrica Ellipsoscapha aff. E. occidentalis Ellipsoscapha aff £. subcylindrica Ellipsoscapha n. sp. Eoacteon n. sp. Euspira obliquata Fasciolaria ? gracilenta Graphidula culbercsoni Graphidula cf. alieni Graphidula cf. obscura Gyrodes cf. spillmani Gyrodes subcarinatus Lomirosa n . sp. Lunaria sp. Lunaria subcrassa Margarita nebrascensis Margaritella flexisrriata Medionapus ? sp. Mesorhytis gracilenta Natica (Lunaria) concinna Nonacteonina sp. Nonacteonina attenuata Oligoprycha concinna Oligoprycha sp. Paladmete n. sp. Polinices concinna Polinices recrilabrum Polinices sp. Potamides n. sp. Promathilda (Clathrobaculus) n. sp. Pseudomaura paludinaeformis Pseudobuccinum nebrascense Pyrifusus ? sp. Pyropsis ? sp.

Pyropsis ? n. sp. Pyrifusus (Neptunel/a) newherryi Pyrifusus (Neptunella) inrercexws Rernera cf. stephensoni Rhombopsis ? sp. Rhombopsis newberryi Rhombopsis suhturritus Rhombopsis ? intertexcus Scobinodolus sp. Serrifusus dakotensis Spironema ? sp. Tornarellaea cretacea Trachytriton vinculum Turris (Surcula) minor Turritella ? sp. Vanikoropsis nebrascensis Vanikoropsis haydeni Vanikoropsis tuomeyarra Volutoderma ? clayworthyi Xenophora sp. Class Pelecypoda

Agerostrea mesencerica Anarina doddsi Anatina sp. Anomia flemingi Anomia raetiformis Anomia argentaria Anomia subtrigonalis Anomia cf. argentaria Anomia tellinaides Anomia sp. Anomia n. sp. Aphrodina ? sp. Astarte gregoria Astarte sp. Clisocolus moreauensis Corbula crassimarginata Crassatella subquadrata Crassatella sp. Crassostrea glabra Crenella cf. elegantula Crenella aff. C. microstriata Crenella sp. Cuspidaria grovensis Cuspidaria variabilis Cuspidaria ventricosa Cuspidaria moreauensis Cuspidaria sp. Cyclorisma ? sp. Cymbophora warrenana Cyrnhophora canonensis Cymbophora holrnesi Cymbophora gracilis Cymbophora sp.

105

Cymbophora.

n.

sp.

Modiolus cf. wrighti

Ethmocardium welleri

Nemodon sulcatinus

E xogyra costata

Nemodon adkinsi

Exogyra sp.

Nemodon eufaulensis

Gervillia sp.

Goniomya americana

Nemodon sp.

Nucula cancel/uta

Goniomya sp.

Nucula planimurginata

Goniochasma stimpsoni

Nucula fUJcatochana

ldonearca shumardi

Nucula subplana

Inoceramus pertenuis

Nucula cf. subplana

Inoceramus oblongus Inoceramus sublaevis

Nucula (Pectinucula) n. sp. Nuculana bisulcata

Inoceramus agdjakendensis

Nuculana evansi

Inoceramus subcompressus

Nuculana corbetensis

Inoceramus aff. /. proximus

Nuculana corsicana

Inoceramus az.erbaidjanen..vis

Nuculana sp.

Inoceramus convexus

Nymphalucina subundata

Inoceramus barabini

Nymphalucina occidentalis

Inoceramus aff. I. turgidus Inoceramus sublaevis Inoceramus sagensis Inoceramus tausiensis Inoceramus cf. I. shikotanensis Inoceramus tenuilineatus Inoceramus proximus

Nymphalucina sp.

Nymphalucina n. sp.

Openochasma cuneatum

Ostrea russelli

Ostrea cf. 0. russelli Ostrea sp.

Ostrea plumosa

Inoceramus canadensis

Ostrea cf. O. fa/cata

Inoceramus vanuxemi

Ostrea inomata

Inoceramus aff. /. penenuis

Oxytoma haydeni

Inoceramus mcshaniensis Inoceramusfumivali

Oxytoma nebrascana

Pachymya ? aurandi

Inoceramus palliseri

Panope berthoudi

Inoceramus subcircularis

Panope sp.

Inoceramus cf. I. proximus

Pecten (Chlamys) nebrascensis

Inoceramus mcleami

Pecten (Syncyclonena

Inoceramus cf. I. nebrascensis

Pecten (Amusium

?) simplicius ?) cf. danei

Inoceramus (Endocostea) sulcatus

Pecten (Co.mptonectes) sp.

Inoceramus cf. I. balticus

Periploma

Inoceramus typicus

Perrisonota protexta

? sp.

Inoceramus incurvus

Phelopteria linguaefonnis

Inoceramus cf. balchi

Phelopteria sublevis

Inoceramus fibrosus

Pholadomya hodgei

Leda pittensis Leda hindi

Pholadomya sp. Pinna lakesii

Legumen ellipticum

Pinna sp.

Legumen sp.

Protocardia rara

Lima pelagica

Protocardia subquadrata

Limatula aff. L acutilineata

Protocardia sp.

Limopsis parvula

Pteria petrosa

Limopsis sp.

Pseudoptera ? sp.

Lucina occidentalis

Pteria cf. parkensis

Lucina subundata

Pteria linguaefonnis

Modiolus uddeni

Pteria sp.

Modiolus aff. M. wenonah

1 06

Modiolus meeki

Dosiniopsis deweyi

Ammonites and the other Cephalopods of the Pierre Seaway

Pteria (Oxytoma) nebrascana

Solemya

o.

"Prosaurodon " pygmaeus

sp.

Spyridoceramusfibrosus Syncyclonema halli Syncyclonema

o.

Tancredia sp.

sp.

Bananogmius evolutus Order Elopiforroes Palaeoclupea dakotaensis Eloposis sp.

Tellina munda

Apsopelix minimus

Tellinimera scitula

Apsopelix berycinus

Tenea sp.

Pachyrhizodus caninus

cf. Tenuiptera sp. Thetiopsis circularis

Pachyrhizodus minimus Order Aulopifonnes

Thracia n. sp.

Cimolichthys nepahalica

Thyasira rostrata rostrata

Endwdus petrosus

Thyasira rostrata cracens

Encho®s gladiolus

Thyasira quadrula quadrula

Stratodus apicalis

Thyasira quadrula arrecta Thyasira triangulata Thyasira beauchampi beauchampi

Class Reptilia Order Chelonia

Thyasira beauchampi rex

Toxochelys latiremis

Thyasira advena advena

Archelon isc:hyros

Thyasira becca becca

Archelon marshi

Thyasira becca cobbani

Protostega sp.

Thyasira cantha Thyasira n. sp.

Veniella aff. V. conradi

Order Plesiosauria Dolicharhynchops osbomi Polycotylus latipinn.us

Veniella sp.

Ela.fmasaurus platyurus

Veniella humils i

Styxosaurus browni

Yoldia scitula

Hydralmosaurus serpentinus

Yoldia evansi Class Scapbopoda

Alzadasaurus pembertoni

Order Squamata

Cadulus obnutus

Platecarpus cf. P. somenensis

Dentalium gracile

Platecarpus icteric:us

Denlalium pauperculum

Platecarpus sp.

Dentalium sp.

Plioplatecarpus primaevus Plioplatecarpus sp.

PHYLUM CHORDATA Class Chondrichthyes Order Lamoifonnes

Prognalhodon crassartus Prognathodon overtoni Mosasau.rus missouriensis

Cretolamna appendiculata

Mosasau.rus conodon

Squalicorax cf. S. kmlpi

Globidms dalc.otenss i

Odontaspis sp.

Order Hybodontiformes Ptychodus sp. Order Chimaeriformes Jchthypriapis gliJdiiLs Class Osteichthyes

Order Pachyconnifonnes Protosphyrcuna gladius Protosphyrcuna gigas Order lchthyodectiformes Gillicus arcuatus lchthyodectes ctenodon Xiphactinus aw:lax icbthyodectid undet. Saurocephalus /anciformis

Saurodon /eanus

C/idostes propython Tylosaurus proriger Hainosaurus sp.

Order Pterosauria Pteranodon sp. Order Saurischia

omitbomimid gen. undet. Order Omithiscbia

hadrosaurid gen.. undet. ceralOpSi.an gen. undet.

Class Aves

Order Hesperornithiformes Hesperomis rega/is

hespel 01 oithifonn undet. Order Jcbthyornithiformes

/drtlryomis sp.

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Axonoceras compressum drawing by John R. Stacy

OF THE PIERRE SEAWAY Wim AurnoR REFERENcES* page

Phylum Mollu ca Cuvier, 1 797 Class Cephalopoda Cuvier, 1 797 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Order Ammonoidea Ziuel, 1884. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family BacuJitidae Gill, 1 87 1 Genus Baculites Lamarck, 1 799 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites aquilaensis Reeside, 1927 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites haresi Reeside, 1927 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites sp. (smooth) (unnamed) Gill and Cobban, 1973 . . . . . . . . . . . . . . . Baculites sp. (weak flank ribs) (unnamed) Gill and Cobban, 1973 . . . . . . . . Baculites obtusus Meek, 1876 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bacu/ites mclearni Landes, 1 940 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites asperiformis Meek, 1876 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites sp. (smooth species) (unnamed) Gill and Cobban, 1 966a . . . . . . . Baculites perplexus (early form) Cobban, 1 962b . . . . . . . . . . . . . . . . . . . . . . Baculites gilberti Cobban, 1 962b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites perplexus (late form) Cobban, 1 962b . . . . . . . . . . . . . . . . . . . . . . Baculites gregoryensis Cobban, 1 9 5 1 a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculires reduncus Cobban, 1977 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bacu.lites scotti Cobban, 1 958a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculires sp. (new species) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculires pseu.dovatus Elias, 1933 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites crickmayi Williams, 1930 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites rugosus Cobban, 1 962a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites corrugatus Elias, 1933 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites compressus Say, 1 820 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites compressus var. robinsoni Cobban, 1962a . . . . . . . . . . . . . . . . . . . Baculites undams Stephenson, 1941 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculires sp. (undescribed) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites cuneatus Cobban, 1 962a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites reesidei Elias, 1933 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites jenseni Cobban, 1 962a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites eliasi Cobban, 1958a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites bacu/us Meek and Hayden, 1 86 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites grandis Hall and Meek. 1855 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites meeki Elias, 1 933 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baculites clinolobatus Elias, 1933 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Pseudobaculites Cobban, 1 952b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pseudobaculites natosini (Robinson, 1945) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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14 18 19 19 20 20 21, 41 21, 41 22, 4 1 22, 4 1 23, 41 23, 41 24, 4 1 24, 4 1 24 25 40 25, 40 26, 40 26, 40 27, 40 27, 40 28, 39 28, 39 29, 39 30, 39 3 1 , 39

.

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31, 32, 32, 33, 34. 35,

39 39 39 39 38 38

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•

Family Collignoniceratidae Wright and Wright, 1 95 1 . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Menabites Collignon, 1 948. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Menabites (Delawarella) danei (Young, 1 963) . . . . . . . . . . . . . . . . . . . . . . . . Menabites (Delawarella) vanuxemi (Morton, 1830) . . . . . . . . . . . . . . . . . . . .

42 42 42 43

Genus Submortoniceras Spath. 1926. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Submortoniceras tequesquitense Young, 1 963. . . . . . . . . . . . . . . . . . . . . . . . .

43

Parentheses enclosing the author's name Indicate that his original descriptiOn placed the species 111 a genus not currently accepted for that species.

140

36, 38 37 37

Amnwniles and 1he CJiher CephaiCJpods ofthe Pierre Sea-..·U)·

43

page

Family Desmoceratidae Zittel, 1 895 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Parapuzosia Nowak, 1 9 l3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parapuzosia bradyi Miller and Youngquist, 1 946 . . . . . . . . . . . . . . . . . . . . .

. . .

Family Diplomoceratidae Spath, 1926 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Exiteloceras Hyatt, 1894 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exiteloceras jenneyi (Whitfield, 1877) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Glyptoxoceras Spath, 1925 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Glyptoxoceras rubeyi ( Reeside, 1927) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Parasolenoceras Collignon, 1 969 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parasolenoceras pulcher Cobban and Kennedy, 1 99 1 a . . . . . . . . . . . . . . . . . Genus Solenoceras Conrad, 1 860 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solenoceras crassurn (Whitfield, 1 877) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solenoceras sp. (undescribed) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solenoceras texanum (Shumard, 1 86 1 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solenoceras reesidei Stephenson, 1 94 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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44 44 44 45 45 45 46 46 48 48 47 48 47 47 47

Family Nostoceratidae Hyatt, 1 894 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Genus Anaklinoceras Stephenson, 1941 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Anaklinoceras gordiale Cobban, Kennedy, and Scott, 1992 . . . . . . . . . . . . . . 49 Anaklinoceras reflexum Stephenson. 1941 . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Genus Axonoceras Stephenson, 1941 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Axonoceras compressurn Stephenson, 1 94 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Genus Cirroceras Conrad, 1868 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1 Cirroceras conradi (Matton, 1 84 1 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1 Genus Didymoceras Hyatt, 1 894 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1 Didymoceras cochleatum (Meek and Hayden, 1858) . . . . . . . . . . . . . . . . . . 52 Didymoceras morcon.i (Meek and Hayden. 1 857) . . . . . . . . . . . . . . . . . . . . . 52 Didymoceras tortum (Meek and Hayden, 1 858) . . . . . . . . . . . . . . . . . . . . . . 51 53 Didymoceras binodosum ( Kennedy and Cobban, 1 993b) . . . . . . . . . . . . . . . Didymoceras cf. archiacian.um (d'Orbigny, 1 842) . . . . . . .. . 53 Didymoceras nebrascense (Meek and Hayden, 1 856) . . . . . . . . . 54 Didymoceras stevensoni (Whitfield, 1 877) . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Didymoceras cheyennen.se (Meek and Hayden, 1 856) . . . . . . . . . . . . . . . . . . 56 Didymoceras sp. (undescribed) .............. . . . . Genus Nostoceras Hyatt, 1 894 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Nostoceras monotuberculatum Kennedy and Cobban, 1993b . . . . . . . . . . . . 57 Nostoceras aff. N. colubriformes Stephenson, 1941 . . . . . . . . . . . . . . . . . . . Nostoceras aff. N. humile Stephenson, 1 94 1 . . . . . . . . . . . . . . . . . . . . . . . . . Genus Oxybeloceras Hyatt, 1 900 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Oxybeloceras sp. (undescribed) .. . ... .. . . . 58 Oxybeloceras meekanum (Whitfield, 1 877) . . . . . . . . . . . . . . . . . . . . . . . . . . 58 .

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Family Pacbydiscidae Spath, 1922 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Menuites Spath, 1922 .

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59 59 141

Menuites portlocki (Sharp, 1 855) complexus (Holland and Meek, 1 856) . . . . Menuites oralensis Cobban and Kennedy, 1993a . . . . . . . . . . . . . . . . . . . . . . Genus Pachydiscus Zittel, 1 884 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pachydiscus cf. oldhami ( Sharp, 1 855) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pachydiscus arkansanus (Stephenson, 194 1 ) . . . . . . . . . . . . . . . . . . . . . . . . . Pachydiscus cf. hombyense Jones, 1 963 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pachydiscus catarinae Anderson and Hanna, 1 935 . . . . . . . . . . . . . . . . . . . . Famil y Placenticeratidae Hyatt, 1 903 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hoplitoplacenticeras, Spath, 1922 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hoplitoplacenticeras cf. H. coesfeldiense (SchlUter, 1 872) var. schliiteri Mikhailov, 1 9 5 1 . . . . . . . . . . . . . . . . Hoplitoplacenticeras marroti (Coquand, 1 859) . . . . . . . . . . . . . . . . . . . . . . . Genus Placenticeras Meek, 1 870 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Placenticeras sancarlosense Hyatt, 1 903 . . . . . . . . . . . . . . . . . . . . . . . . . . . . Placenticeras guadalupae (Roemer, 1 849) . . . . . . . . . . . . . . . . . . . . . . . . . . . Placenticeras planum Hyatt, 1 903 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pfacenriceras pingue Kennedy, Cobban, and Landman. 1996 . . . . . . . . . . . . Placenticeras meeki (Bohm, 1 898) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Placenticeras intercafare (Meek and Hayden. 1 860) . . . . . . . . . . . . . . . . . . . Pfacenticeras costatum Hyatt, 1 903 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Genus

page

59 60 61 61 61 61 61 62 63

63 63 64 64 65 66 67 68 69 70

Family Scaphitidae Meek, 1876 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1 Genus Haresiceras Reeside, 1 927 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Haresiceras fischeri Reeside, 1 927 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Haresiceras natronense Reeside, 1927 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Haresiceras pfacentifonne Reeside, 1927 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Genus Hop/oscaphites Nowak, 1 9 1 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Hopfoscaphites gifli (Cobban and Jeletzky, 1965) . . . . . . . . . . . . . . . . . . . . . 73 Hoploscaphites sp. (undescribed) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hoploscaphites landesi Riccardi, 1 983 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Hoploscaphites me/Loi Landman and Waage, 1993. . . . . . . . . . . . . . . . . . . . . 74 Hoploscaphites nicolletii var. saltgrassensis (EHa , 1933) . . . . . . . . . . . . . . . 75 Hoploscaphites birkelundi Landman and Waage 1993 . . . . . . . . . . . . . . . . . . 75 Genus Jeletzkytes Riccardi, 1983 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Jeletzkytes sp. (undescribed) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jeletzkytes nodosus (Owen, 1 852) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Jeletzkytes cf. nodosus (Owen, 1 852) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jeletzkytes brevis (Meek, 1876) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 Jeletzkytes quadrangularis (Meek and Hayden, 1 860) [invalid] . . . . . . . . . . 78 Jeletzkytesfumivali Riccardi, 1983 [doubtful] . . . . . . . . . . . . . . . . . . . . . . . . 79 Jeletzf,:ytes crassus (Coryell and Salmon, 1 934) . . . . . . . . . . . . . . . . . . . . . . . 79, 80 Jeletzkytes plenus (Meek and Hayden, 1 860) . . . . . . . . . . . . . . . . . . . . . . . . . . 80, 8 1 Jefetzkytes criptonodosus Riccardi, 1983 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1 , 82 Je/etzkytes dorfl Landman and Waage, 1 993 . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Genus Ponteixites Warren. 1 934 83 Ponteixites gracilis Warren. 1934 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 .

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142

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Ammonites and rhe orher Cephalopods ofrhe Pierre Seaway

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page

Pontei.xites robustus Warren, 1934 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Rhaehoceras Meek, 1 876 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rhaeboceras halli (Meek and Hayden, 1 856) . . . . . . . . . . . . . . . . . . . . . . . . . Rhaeboceras albertense (Warren, 1 930) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rhaeboceras subglobosum (Whiteaves, 1 885) . . . . . . . . . . . . . . . . . . . . . . . . Rhaeboceras coloradoense Cobban, 1 987 . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rhaeboceras burkholderi Cobban, 1 987 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rhaeboceras mullananum (Meek and Hayden, 1 862) . . . . . . . . . . . . . . . . . . . Genus Scaphites Parkinson, 1 8 1 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scaphites hippocrepis 1 (DeKay, 1827) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scaphites hippocrepis !I (DeKay, 1 827). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scaphites hippocrepis III (DeKay, 1 827) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Trachyscaphites Cobban and Scott, 1964 . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trachyscaphites spiniger (Schluter, 1 872) ssp. porchi (Adkins, 1 929) . . . . . . Trachyscaphites praespiniger Cobban and Scou, 1 964 . . . . . . . . . . . . . . . . . . Trachyscaphites redbirdensis Cobban and Scott, 1964 . . . . . . . . . . . . . . . . . . Trachyscaphites pulcherrimus (Roemer, 1 84 1 ) . . . . . . . . . . . . . . . . . . . . . . . .

83 84 84 85 85 86 86 87 88 88 88 88 89 90 90 90 89

Famil y Sphenodiscidae Hyatt, 1 900 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1 Genus Coahuilites Bose, 1927 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Coahuilites she/toni Bose, 1927 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Genus Sphenodiscus Meek, 1 872. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1 Sphenodiscus pleurisepta (Conrad, 1 857 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Order Be1emnitidea Zittel. 1 895 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family Be1emniteillidae Pav1ow, 1 9 1 3 . . . . . . . . . . . . . . . . . . . . . . . . . Genus Belemnitella d'Orbigny, 1842. . . . . . . . . . . . . . . . . . . . . . . . . Belemnitella bulbosa Meek and Hayden, 1 856. . . . . . . . . . . .

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.......... .......... ... .. ..... ... ...... .

Order Nautilidea Agassiz, 1 847. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family Nauti lidae de Blainville, 1 825. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Genus Eutrephoceras Hyatt, 1 894. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eutrephoceras alcensense Reeside, 1927 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eutrephoceras dekayi Morton, 1 834 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eutrephoceras "elegans" var. nebrascensis (Meek and Hayden, 1 862) . . . . . Eutrephoceras dekayi var. montanaensis (Meek, 1876) . . . . . . . . . . . . . . . . .

93 93 94 94 95 96 96 96, 98 96, 98 97, 98 97, 98

Order Teuthidea Naef, 1 9 1 6 . 99 Family Ke1aenidae Naef, 1921 (see also Jeletzky, 1 966) . . . . . . . . . . . . . . . . . . . . . . . . 99 Genus Tusoteuthis Logan, 1 898 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Tusoteulhis longa Logan, 1 898 (see also Nicholls and Tsaak, 1987) . . . . . . . . 100 . . . . . . . . . . . . . . . . . . . 1 00 Tusoteuthis sp. (undescribed) . . . . . . . . .

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Family Trachyteulhidac Naef, 1 92 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 1 Genus Actinosepia Whiteaves, 1 897 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 I Actinosepia canadensis Whiteaves, 1 897 . . . . . . . . . . . . . . . . . . . . . . . . . . . I 0 I .

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ABOUT THE: AUTHORs

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Neal L. Larson is a South Dakota native and has been interested in ammonites since chi ldhood. His passion has been collecting, preparing, and studying Campanian and Maastrichtian Age ammonites from the Western Interior of North America as well as ammonites from all over the world. Neal served as a content specialist for Glen co Publishing in preparation of a ninth- and tenth­ grade level text titled, Biology, The Dynamics of Life. Presently, he is working on several different publications, both independently and with Dr. N. H. Landman, Dr. W. A. Cobban, Dr. W. J . Kennedy, and Steve Jorgensen. For twenty-plus years, Neal has been vice president o f the Black Hills Institute of Geological Research, Tnc., as well as a fossil collector and preparator with the Institute. As president of the Black Hills Museum of Natural History, he has spearheaded the efforts to purchase land for the museum site and establish an annual Natural History Days Festival in Hill City, South Dakota. He received a B . S. in Geology from S. D . S. M . & T. in 1977.

Steven D. Jorgensen grew up near Yankton, and now resides in Omaha, Nebraska. He has collected and studied ammonites for more than 25 years. Steve's primary interest is Upper Cretaceous ammonites, from the Turonian and Campanian Ages of the Western Interior of North America. He is also an Engineer-in-Trai ning (EIT), a Professional Geologi t (#1 30) in the State of Wyoming, and a Certified Professional Geologist (#9596) by the American Institute of Professional Geologists. H i s current research includes comparing the Carlile Shale ofthe Black Hills to the Carli le Shale in eastern South Dakota, with particular attention to the shark and ammonite taxa similarities and differences. Jorgensen received a B . S. in Geological Engineering from S. D. S. M . & T. in 1 977.

Robert A. Farrar, a native of the Cleveland, Ohio, area, developed his interest in fossils injunior high. Robert moved to South Dakota in 1973 to major in Geology at the South Dakota School of Mines & Technology, meeting Neal and Peter Larson, and Steve Jorgensen while all were college students. He has served as secretary/treasurer for the Black Hills Institute of Geolobrical Research, Tnc., since its incorporation in 1978. His previous publication credits include coauthorship with Peter L. Larson of What Is a Fossil? and Fossil Vertebrates ofthe White River Badlands. Robert's current research involves the study of Upper Cretaceous, Cenomanian Age, marine fishes of Lebanon and Pegmatite phosphate mineralogy.

Peter L. Larson has shared with his brother, Neal, a lifelong love for, and fascination with. ammonites. Together, they have amassed one of the finest collection of prepared and unprepared ammonite specimens in the world. Peter is the chief author of the institute's What Is It? series of educational posters and pamphlets including What Is an Ammonite? He is also the primary author of the institute's publications titled Fossil Vertebrates of the White River Badlands and The Pierre Shale and Its Macrofauna, a precursor of this publication. Peter is well known for his research paper., and popular articles on Tyrannosaurus rex and hi current research projects include a book-in­ progress on that tyrant king of the Cretaceous. President and founder of B lack Hills In titute of Geological Research, Tnc., he is also vice president of the Black Hills Museum of Natural HistOT) in Hill City, South Dakota. Pete received a B . S. in Geology from S. D. S . M . & T. in 1 974. and completed most of his Ma ters requirements.

14!!

Ammonites and the other Cephalopods ofthe Pierre Seaway