Horns and Beaks
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Description

New findings on Triceratops, Iguanodon, and other related dinosaurs


Horns and Beaks completes Ken Carpenter's series on the major dinosaur types. As with his volumes on armored, carnivorous, and sauropodomorph dinosaurs, this book collects original and new information, reflecting the latest discoveries and research on these two groups of animals. The Ornithopods include Iguanodon, one of the first dinosaurs ever discovered and analyzed, and perhaps the most common and best-documented group, the hadrosaurs or "duckbilled dinosaurs." The Ceratopsians include Triceratops, known for its distinctive three-horned skull and protective collar.

Contributors are Michael K. Brett-Surman, Kathleen Brill, Kenneth Carpenter, Benjamin S. Creisler, Tony DiCroce, Andrew A. Farke, Peter M. Galton, David Gilpin, Thomas M. Lehman, Nate L. Murphy, Christopher J. Ott, Gregory S. Paul, Xabier Pereda Suberbiola, Albert Prieto-Marquez, Bruce Rothschild, José Ignacio Ruiz-Omeñaca, Darren H. Tanke, Mark Thompson, David Trexler, and Jonathan R. Wagner.


Contributors
Preface
Acknowledgments

I. Beaked Dinosaurs: The Ornithopods
1. Callovosaurus leedsi, the Earliest Dryosaurid Dinosaur (Ornithischia: Euornithopoda) from the Middle Jurassic of England
José Ignacio Ruiz-Omeñaca, Xabier Pereda Suberbiola, and Peter M. Galton
2. Teeth of Ornithischian Dinosaurs (Mostly Ornithopoda) from the Morrison Formation (Upper Jurassic) of the Western United States
Peter M. Galton
3. A Description of a New Ornithopod from the Lytle Member of the Purgatoire Formation (Lower Cretaceous) and a Reassessment of the Skull of Camptosaurus
Kathleen Brill and Kenneth Carpenter
4. Turning the Old into the New: A Separate Genus for the Gracile Iguanodont from the Wealden of England
Gregory S. Paul
5. A Possible New Basal Hadrosaur from the Lower Cretaceous Cedar Mountain Formation of Eastern Utah
David Gilpin, Tony DiCroce, and Kenneth Carpenter
6. Postcranial Osteology of the Hadrosaurid Dinosaur Brachylophosaurus canadensis from the Late Cretaceous of Montana
Albert Prieto-Marquez
7. "Leonardo," a Mummified Brachylophosaurus (Ornithischia: Hadrosauridae) from the Judith River Formation of Montana
Nate L. Murphy, David Trexler, and Mark Thompson
8. Discussion of Character Analysis of the Appendicular Anatomy in Campanian and Maastrichtian North American Hadrosaurids—Variation and Ontogeny
Michael K. Brett-Surman and Jonathan R. Wagner
9. Osteochondrosis in Late Cretaceous Hadrosauria: A Manifestation of Ontologic Failure
Bruce Rothschild and Darren H. Tanke
10. Deciphering Duckbills: A History in Nomenclature
Benjamin S. Creisler

II. Horned Dinosaurs: Ceratopsians
11. Cranial Anatomy and Biogeography of the First Leptoceratops gracilis (Dinosauria: Ornithischia) Specimens from the Hell Creek Formation, Southeast Montana
Christopher J. Ott
12. Cranial Osteology and Phylogenetic Relationships of the Chasmosaurine Ceratopsid Torosaurus latus
Andrew A. Farke
13. Growth and Population Age Structure in the Horned Dinosaur Chasmosaurus
Thomas M. Lehman
14. Bone Resorption, Bone Lesions, and Extracranial Fenestrae in Ceratopsid Dinosaurs: A Preliminary Assessment
Darren H. Tanke and Andrew A. Farke
15. "Bison" alticornis and O. C. Marsh's Early Views on Ceratopsians
Kenneth Carpenter

Index

Sujets

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Date de parution 14 novembre 2006
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Contributors are Michael K. Brett-Surman, Kathleen Brill, Kenneth Carpenter, Benjamin S. Creisler, Tony DiCroce, Andrew A. Farke, Peter M. Galton, David Gilpin, Thomas M. Lehman, Nate L. Murphy, Christopher J. Ott, Gregory S. Paul, Xabier Pereda Suberbiola, Albert Prieto-Marquez, Bruce Rothschild, José Ignacio Ruiz-Omeñaca, Darren H. Tanke, Mark Thompson, David Trexler, and Jonathan R. Wagner.


Contributors
Preface
Acknowledgments

I. Beaked Dinosaurs: The Ornithopods
1. Callovosaurus leedsi, the Earliest Dryosaurid Dinosaur (Ornithischia: Euornithopoda) from the Middle Jurassic of England
José Ignacio Ruiz-Omeñaca, Xabier Pereda Suberbiola, and Peter M. Galton
2. Teeth of Ornithischian Dinosaurs (Mostly Ornithopoda) from the Morrison Formation (Upper Jurassic) of the Western United States
Peter M. Galton
3. A Description of a New Ornithopod from the Lytle Member of the Purgatoire Formation (Lower Cretaceous) and a Reassessment of the Skull of Camptosaurus
Kathleen Brill and Kenneth Carpenter
4. Turning the Old into the New: A Separate Genus for the Gracile Iguanodont from the Wealden of England
Gregory S. Paul
5. A Possible New Basal Hadrosaur from the Lower Cretaceous Cedar Mountain Formation of Eastern Utah
David Gilpin, Tony DiCroce, and Kenneth Carpenter
6. Postcranial Osteology of the Hadrosaurid Dinosaur Brachylophosaurus canadensis from the Late Cretaceous of Montana
Albert Prieto-Marquez
7. "Leonardo," a Mummified Brachylophosaurus (Ornithischia: Hadrosauridae) from the Judith River Formation of Montana
Nate L. Murphy, David Trexler, and Mark Thompson
8. Discussion of Character Analysis of the Appendicular Anatomy in Campanian and Maastrichtian North American Hadrosaurids—Variation and Ontogeny
Michael K. Brett-Surman and Jonathan R. Wagner
9. Osteochondrosis in Late Cretaceous Hadrosauria: A Manifestation of Ontologic Failure
Bruce Rothschild and Darren H. Tanke
10. Deciphering Duckbills: A History in Nomenclature
Benjamin S. Creisler

II. Horned Dinosaurs: Ceratopsians
11. Cranial Anatomy and Biogeography of the First Leptoceratops gracilis (Dinosauria: Ornithischia) Specimens from the Hell Creek Formation, Southeast Montana
Christopher J. Ott
12. Cranial Osteology and Phylogenetic Relationships of the Chasmosaurine Ceratopsid Torosaurus latus
Andrew A. Farke
13. Growth and Population Age Structure in the Horned Dinosaur Chasmosaurus
Thomas M. Lehman
14. Bone Resorption, Bone Lesions, and Extracranial Fenestrae in Ceratopsid Dinosaurs: A Preliminary Assessment
Darren H. Tanke and Andrew A. Farke
15. "Bison" alticornis and O. C. Marsh's Early Views on Ceratopsians
Kenneth Carpenter

Index

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Horns and Beaks
LIFE OF THE PAST James O. Farlow, editor
Horns and Beaks
Ceratopsian and Ornithopod Dinosaurs
Edited by Kenneth Carpenter
INDIANA UNIVERSITY PRESS Bloomington and Indianapolis
This book is a publication of Indiana University Press 601 North Morton Street Bloommgton, IN 47404-3797 USA
http://iupress.indiana.edu
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© 2007 by Indiana University Press
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Library of Congress Cataloging-in-Publication Data
Horns and beaks : Ceratopsian and Ornithopod dinosaurs / edited by Kenneth Carpenter.           p. cm. — (Life of the past)     Includes bibliographical references and index.     ISBN 0-253-34817-X (cloth : alk. paper)   1. Ornithischia. 2. Ceratopsidae. I. Carpenter, Kenneth, 1949- II. Series.     QE862.O65H675 2007     567.914—dc22
2006016496
1 2 3 4 5 12 11 10 09 08 07
Contents
Contributors
Preface
Acknowledgments
PART ONE: Beaked Dinosaurs: The Ornithopods
1 • Callovosaurus leedsi , the Earliest Dryosaurid Dinosaur (Ornithischia: Euornithopoda) from the Middle Jurassic of England
José Ignacio Ruiz-Omeñaca, Xabier Pereda Suberbiola, and Peter M. Galton
2 • Teeth of Ornithischian Dinosaurs (Mostly Ornithopoda) from the Morrison Formation (Upper Jurassic) of the Western United States
Peter M. Galton
3 • A Description of a New Ornithopod from the Lytle Member of the Purgatoire Formation (Lower Cretaceous) and a Reassessment of the Skull of Camptosaurus
Kathleen Brill and Kenneth Carpenter
4 • Turning the Old into the New: A Separate Genus for the Gracile Iguanodont from the Wealden of England
Gregory S. Paul
5 • A Possible New Basal Hadrosaur from the Lower Cretaceous Cedar Mountain Formation of Eastern Utah
David Gilpin, Tony DiCroce, and Kenneth Carpenter
6 • Postcranial Osteology of the Hadrosaurid Dinosaur Brachylophosaurus canadensis from the Late Cretaceous of Montana
Albert Prieto-Marquez
7 • “Leonardo,” a Mummified Brachylophosaurus (Ornithischia: Hadrosauridae) from the Judith River Formation of Montana
Nate L. Murphy, David Trexler, and Mark Thompson
8 • Discussion of Character Analysis of the Appendicular Anatomy in Campanian and Maastrichtian North American Hadrosaurids—Variation and Ontogeny
Michael K. Brett-Surman and Jonathan R. Wagner
9 • Osteochondrosis in Late Cretaceous Hadrosauria: A Manifestation of Ontologic Failure
Bruce Rothschild and Darren H. Tanke
10 • Deciphering Duckbills: A History in Nomenclature
Benjamin S. Creisler
PART TWO: Horned Dinosaurs: Ceratopsians
11 • Cranial Anatomy and Biogeography of the First Leptoceratops gracilis (Dinosauria: Ornithischia) Specimens from the Hell Creek Formation, Southeast Montana
Christopher J. Ott
12 • Cranial Osteology and Phylogenetic Relationships of the Chasmosaurine Ceratopsid Torosaurus latus
Andrew A. Farke
13 • Growth and Population Age Structure in the Horned Dinosaur Chasmosaurus
Thomas M. Lehman
14 • Bone Resorption, Bone Lesions, and Extracranial Fenestrae in Ceratopsid Dinosaurs: A Preliminary Assessment
Darren H. Tanke and Andrew A. Farke
15 • “ Bison “ alticornis and O. C. Marsh’s Early Views on Ceratopsians
Kenneth Carpenter
Index
Contributors
Michael K. Brett-Surman, Department of Paleobiology, National Museum of Natural History, The Smithsonian Institution, 10th & Constitution Avenue, Washington, DC 20560 USA
Kathleen Brill, Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Blvd., Denver, CO 80205 USA
Kenneth Carpenter, Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Blvd., Denver, CO 80205 USA
Benjamin S. Creisler, 1705 Belmont 602, Seattle, WA 98122 USA
Tony DiCroce, Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Blvd., Denver, CO 80205 USA
Andrew A. Farke, Department of Anatomical Sciences, Stony Brook University, T8 040 Health Sciences Center, Stony Brook, NY 11794 USA
Peter M. Galton, College of Naturopathic Medicine, University of Bridgeport, Bridgeport, CT 06601 USA
David Gilpin, Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Blvd., Denver, CO 80205 USA
Thomas M. Lehman, Department of Geosciences, Texas Tech University, Lubbock, TX 79409 USA
Nate L. Murphy, Judith River Dinosaur Institute, P.O. Box 429, Malta, MT 59538 USA
Christopher J. Ott, University of Wisconsin-Madison Geology Museum, 1215 W Dayton St., Madison, WI 53706
Gregory S. Paul, 3109 N. Calvert St., Baltimore, MD 21218
Xabier Pereda Suberbiola, Universidad del País Vasco/EHU, Facultad de Ciencia y Tecnología, Departamento de Estratigrafía y Paleontología, Apdo. 644, 48080 Bilbao, Spain
Albert Prieto-Marquez, Department of Biological Science, Conradi Building, Florida State University, Tallahassee, FL 32306 USA
Bruce Rothschild, Arthritis Center of Northeast Ohio, 5500 Market St., Youngstown, OH 44512 USA
José Ignacio Ruiz-Omeñaca, Universidad de Zaragoza, Departamento de Ciencias de la Tierra, Area de Paleontología, 59 Zaragoza, Spain
Darren H. Tanke, Dinosaur Research Program, Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, Alberta T0J 0Y0 Canada
Mark Thompson, Judith River Dinosaur Institute, P.O. Box 429, Malta, MT 59538 USA
David Trexler, Two Medicine Dinosaur Center, P.O. Box 786, Bynum, MT 59419 USA
Jonathan R. Wagner, Jackson School of Geosciences, University of Texas at Austin, 1 University Station C1100, Austin, TX 78712-0254 USA
Preface
The past decade has seen a considerable amount of research done on dinosaurs. Some of the most exciting of this work has been presented in this series by Indiana University Press: The Armored Dinosaurs (2001), Mesozoic Vertebrate Life (2001, edited with Darren Tanke), The Carnivorous Dinosaurs (2005), and Thunder-Lizards (2005, edited with Virginia Tidwell). This volume is the last in the series of edited volumes and deals with current research in ornithischian dinosaurs other than the armored ones. Horns and Beaks presents some historical insights as well as some descriptive studies. As before, I hope there is a little of something for everyone.
Acknowledgments
This last in the series on the latest research in dinosaurs was made possible by the support of Jim Farlow and Bob Sloan, Indiana University Press. Thanks to Karen Hellekson, copyeditor, and Miki Bird, managing editor at Indiana University Press.
Thanks also to the contributing authors for their patience.
Part One Beaked Dinosaurs: The Ornithopods
1. Callovosaurus leedsi , the Earliest Dryosaurid Dinosaur (Ornithischia: Euornithopoda) from the Middle Jurassic of England
J OSÉ I GNACIO R UIZ -O MEÑACA , X ABIER P EREDA S UBERBIOLA , AND P ETER M. G ALTON
Abstract
Callovosaurus leedsi (Lydekker 1889), based on an isolated femur from the Oxford Clay (Middle Jurassic, Callovian) of Peterborough, England, is reinterpreted as a dryosaurid. It represents the oldest record of this poorly known group of ornithopods. Callovosaurus was previously regarded variously as a hypsilophodontid, camptosaurid, or iguanodontid, but the femur shows a combination of characters typical of dryosaurids: bowed shaft; proximally placed pendant fourth trochanter; pit for insertion of the M. caudifemoralis longus well developed and separated from the fourth trochanter; and anterior intercondylar groove. Further, the concave excavation posteriorly proximal to medial condyle meets the medial surface of the distal end at a sharp edge, and the lateral condyle is transversely reduced with a rounded ledge lateral to it. Callovosaurus differs from Dryosaurus and Valdosaurus in the more expanded, transversely flattened anterior trochanter. Moreover, it differs from Valdosaurus in the shallow anterior intercondylar groove and the very slightly concave internal surface of the distal end.
Introduction
Lydekker (1889) described a left femur from the Oxford Clay near Peterborough, England as a new species of Camptosaurus, C. leedsi. In addition to the original (BMNH R1993; collection of Mr. A. N. Leeds, purchased in 1892), Lydekker (1890) also mentioned a cast of the femur (BMNH R1608, made in 1888). Gilmore (1909: 290) noted that C. leedsi is similar to Camptosaurus , but “if referable at all to an American genus, its closest affinities, as indicated by the femur, are with Dryosaurus .” Galton (1972, 1974) placed C. leedsi in the Hypsilophodontidae as being closely related to Dryosaurus Marsh 1894 and the “Wealden hypsilophodont” (subsequently named Valdosaurus Galton 1977a). Later, Galton (1975) regarded C. leedsi as closer to Camptosaurus than to Dryosaurus , and assigned it to the Iguanodontidae as Camptosaurus (?) leedsi. Galton and Powell (1980: 437) listed several differences between the femur of C. leedsi and that of C. dispar and noted that “this femur should not be referred to the genus Camptosaurus and it probably represents a new genus.” Finally, Galton (1980a) made Camptosaurus leedsi Lydekker 1889 the type species of Callovosaurus Galton 1980a, and referred it to the Camptosauridae. Since then, Callovosaurus leedsi has been regarded as Iguanodontidae? indet. by Weishampel (1992) and as Iguanodontia nomen dubium by Norman and Weishampel (1992), but Norman (1998) listed it as a valid species of Camptosauridae. More recently, Mateus and Antunes (2001) considered Callovosaurus a nomen dubium.
Age and Provenance of Callovosaurus leedsi
Lydekker (1889, 1890) recorded the type locality of C. leedsi as near Peterborough, Cambridgeshire (formerly Northamptonshire). According to Leeds (1956; see Galton 1980a), the femur was found in a brick pit near Fletton. The horizon is from the Oxford Clay, Middle Jurassic in age. It was referred to the Oxfordian (Upper Jurassic) by Galton (1975; note that the age is Callovian in the abstract), but the bone-bearing layer is from the lower Oxford Clay, which is middle Callovian (probably from the Jason Zone; see Galton 1980a). C. leedsi has also been listed as coming from the upper Callovian (Galton 1977b, 1980b; Galton and Powell 1980) or the middle-upper Callovian (Weishampel 1992). Cox et al. (1992) renamed the lower Oxford Clay the Peterborough Member of the Oxford Clay Formation. In addition to Callovosaurus leedsi , the reptilian fauna of the Peterborough Member (mainly the Jason Zone) of the Peterborough district includes other dinosaurs and reptiles: stegosaur Lexovisaurus durobrivensis (Galton 1985), ankylosaur Sarcolestes leedsi (Galton 1983a), sauropod Cetiosauriscus leedsi (Woodward 1905), pterosaurs (Unwin 1996), plesiosaurs, ichthyosaurs, and crocodilians (see Benton and Spencer 1995; Martill 1988).
Institutional Abbreviations. BMNH, Natural History Museum [formerly the British Museum (Natural History)], London; MB, Museum für Naturkunde (formerly the Humboldt Museum für Naturkunde), Berlin; MNHN, Museum National d’Histoire Naturelle, Paris; SMC, Sedgwick Museum, University of Cambridge, Cambridge; YPM, Peabody Museum of Natural History, Yale University, New Haven, Connecticut.
Systematic Paleontology
Ornithischia Seeley 1888
Ornithopoda Marsh 1881
Iguanodontia Dollo 1888
Dryosauridae Milner and Norman 1984
Callovosaurus Galton 1980a
Type Species. Camptosaurus leedsi Lydekker 1889.
Diagnosis. As for the only species known.
Callovosaurus leedsi (Lydekker 1889)
Synonymy. For a summary, see Martill (1988).
Holotype. BMNH R1993, a left femur (cast, BMNH R1608).
Type Locality and Horizon. Fletton, near Peterborough, Cambridgeshire, England; Oxford Clay Formation, Peterborough Member (=lower Oxford Clay), Middle Jurassic, middle Callovian ( Jason Zone).
Revised Diagnosis. Broad, transversely flattened anterior trochanter (unexpanded, oval to roughly triangular in transverse section in Dryosaurus and Valdosaurus; closely pressed against the greater trochanter in Kangnasaurus ); shallow anterior intercondylar groove (deep in Valdosaurus and some specimens of Dryosaurus ); slightly concave medial surface to the distal end (flat in Valdosaurus and Kangnasaurus ; variable in Dryosaurus ).
Referred Material. Galton (1977a) referred an incomplete left tibia (SMC J.46889, collected in 1902) from Fletton to Dryosaurus (see Galton 1980a: 76, figs. 1g–i). Lhe specimen, which came from the same or a nearly locality to that of C. leedsi , has since been assigned to an indeterminate hypsilophodontid (Galton 1977b; Weishampel 1992), but Galton (1980b) pointed out that it may be referable to C. leedsi.
Description
The femur of Callovosaurus leedsi ( Figs. 1.1 – 1.2 ) has been briefly described and illustrated in several papers (Galton 1975, 1980a; Galton and Powell 1980; Gilmore 1909; Lydekker 1889, 1890), but it has never been described in detail. The specimen is 280 mm long, with maximum proximal and distal widths of 85 and 73 mm, and it belongs to a small ornithopod with an estimated total body length of about 2.5 m (Galton 1980a: table 1). The femur, originally complete, is now in three pieces that still fit together to give the whole bone, as illustrated ( Fig. 1.1 ) by Galton (1980a). As noted by Lydekker (1889), the specimen is damaged and the middle portion of the shaft has been lateromedially crushed, but the proximal and distal ends are well preserved. The shaft is bowed in lateral and medial views. The neck of the femur is perpendicular to the shaft. On the posterior surface of the head, there is a well-developed depression for the antitrochanter (Sereno 1991: 193; “ischial peduncle” of Galton 1980a). The anterior trochanter (i.e., “lesser” trochanter; see Carpenter and Kirkland 1998) is separated from the greater trochanter by a deep and wide cleft ( Figs. 1.1E , 1.2E ), which extends distally to the level of the base of the head in medial view ( Figs. 1.1C , 1.2C ), but it is slightly shallower laterally ( Figs. 1.1B , 1.2B ). The anterior trochanter is broad, being flattened transversely, and its proximal end is below the top of the greater trochanter. The pendant fourth trochanter is proximally placed (the value of the fourth trochanter index is probably close to 0.48 according to Galton 1980a: table 1), but it is distally incomplete. The pit for the attachment of the M. caudifemoralis longus is a big (38 mm high, 20 mm wide) and shallow oval depression, located anteriorly on the medial surface of the shaft (see Discussion). It is separated from the fourth trochanter and is well above the base of this process. The shallowness of this depression could be an artefact due to crushing of the shaft. Distally, the femur has well-developed anterior (extensor) and posterior (flexor) intercondylar grooves. The base of the incomplete posterior lateral (fibular) condyle is transversely reduced in width and internally offset with a rounded shelf external to it. Proximal to the posterior medial condyle, there is a prominent, concave striated excavation, which meets the adjacent medial surface as a sharp sloping edge (area probably for part of M. femorotibialis). The medial surface of the distal end is anteroposteriorly very slightly concave ( Figs. 1.1F , 1.2F ).


Figure 1.1. Callovosaurus leedsi (Lydekker 1889), holotype left femur BMNH R1993 in lateral (A), anterior (B), medial (C), posterior (D), proximal (E), and distal (F) views. A to D are stereopbotographs. Scale line represents 5 cm.


Figure 1.2. Callovosaurus leedsi (Lydekker 1889), holotype left femur BMNH R1993 in lateral (A), anterior (B), medial (C), posterior (D), proximal (E), and distal (F) views, a: anterior (=“lesser”) trochanter; ag: anterior intercondylar groove; c: broken edge of lateral condyle; d: depression for antitrochanter; e: sloping area delimited by sharp edge (area probably for part of M. femorotibialis); f: fourth trochanter; g: greater trochanter; h: head; ic: intertrochanteric cleft; lc: lateral (fibular) condyle; mc: medial (tibial) condyle; p: pit for insertion of M. caudifemoralis longus; rl: rounded ledge lateral to lateral condyle; s: slightly concave internal surface of the distal end. Broken bone indicated by cross-hatching. Scale bar = 5 cm.
Discussion
Callovosaurus as a Dryosaurid Ornithopod
Dryosaurids were small to medium sized (about 2–6 m in total length; see Heinrich et al. 1993), bipedal, cursorial ornithopods. They resemble Hypsilophodon and closely related forms in many respects and were for a long time placed within the Hypsilophodontidae (see Cooper 1985; Galton 1972, 1977a, 1981; Galton and Taquet 1982; Sternberg 1940). Following Milner and Norman (1984), Sues and Norman (1992) placed Dryosaurus (including Dysalotosaurus ) and Valdosaurus in a separate family, the Dryosauridae, as the sister group of all other iguanodontians (Sereno 1986). Sues and Norman (1992) diagnosed the Dryosauridae on the basis of five characters, including two femoral ones: deep extensor groove in distal articular end, and deep pit for insertion of M. caudifemoralis longus developed at base of fourth trochanter. Moreover, Ryan (1997) mentioned additional femoral features: anteriorly bowing shaft as seen in all small ornithopods; deep separation of the greater and anterior trochanters; and very well developed fourth trochanter.
The femur of Callovosaurus exhibits all of the above-mentioned characters and several others that are seen in both Dryosaurus and Valdosaurus (Galton 1977a, 1980b, 1981; Galton and Taquet 1982), i.e., proximally placed pendant fourth trochanter, and posteriorly a reduced lateral condyle with the internally placed condylid bordered by a shelf laterally, and a prominent excavation proximal to the medial condyle that meets the medial surface of the distal end as a sharp edge (Blows 1998; Galton 1981; BMNH specimens). The deep cleft between the greater and anterior trochanters is absent in Kangnasaurus (see Cooper 1985). The deep intertrochanteric cleft, which is present in Dryosaurus, Valdosaurus , and Callovosaurus , could be related to the more cursorial abilities of these forms. The cleft increases the surface for the insertion of the M. iliofemoralis (which connects the anterior trochanter to the middle part of the ilium; see Galton 1969) and probably allows for a faster response of this muscle. In the same way, the development of a large pit in all dryosaurids (although its depth is variable) for the M. caudifemoralis longus, which connects the femur to the anterior caudal vertebrae (Galton 1969), is probably another cursorial adaptation that provides a bigger area for muscular insertion.
The presence of a distinct anterior intercondylar groove on the distal end of the femur is a synapomorphy of Iguanodontia (Sereno 1986; Weishampel and Heinrich 1992) (=Dryomorpha of Norman 1998). This clade includes Tenontosaurus , dryosaurids, camptosaurids, iguanodontids, and hadrosauroids. Gasparinisaura cincosaltensis from the Late Cretaceous of Argentina has been regarded as a basal member of the Euiguanodontia (Coria and Salgado 1996a; Salgado et al. 1997), but its phylogenetic relationships are controversial. The femur does not possess an anterior intercondylar groove, and the fibular condylid is not internally offset but is continuous with the lateral surface of the distal end, so it is more similar to hypsilophodontids than to iguanodontians (see Norman 1998). However, following Coria and Salgado (1996a), Gasparinisaura shares a number of characters with the Dryosauridae and evolved iguanodontians, i.e., a well-developed brevis shelf on the ilium and a metatarsal I that is reduced or absent.
The femur of Callovosaurus differs significantly from those of “hypsilophodontids.” In Hypsilophodon foxii from the Upper Wealden (Barremian) of the Isle of Wight, England (BMNH collection, including BMNH R192a, R193, R195, R196, R2487, R8352; see Galton 1974), the anterior trochanter is slender and separated from the greater trochanter by a shallow cleft in medial view. However, some “hypsilophodontids” (a pectinate grade; see Scheetz 1998; Winkler et al. 1998), such as Othnielia rex , have a deep cleft (see Galton and Jensen 1973). The depression for the M. caudifemoralis longus is shallow in some femora of Hypsilophodon and deep in others, but is generally located close to the base of the fourth trochanter. Distally, the lateral and medial posterior condyles are almost equal in size, lacking the anterior intercondylar groove, the medial excavation, and its associated edge, and the medial surface of the distal end is convex (Galton 1974; Sues and Norman 1992).
Among the Iguanodontia, only dryosaurids have a femur with a proximally placed fourth trochanter. The fourth trochanter is located in the middle or on the distal part of the shaft in Tenontosaurus (Forster 1990), camptosaurids such as Camptosaurus (Gilmore 1909) and Draconyx (Mateus and Antunes 2001), iguanodontids such as Iguanodon (Norman 1980, 1986), Lurdusaurus (Taquet and Russell 1999), and Ouranosaurus (Taquet 1976), and all hadrosauroids (Godefroit et al. 1998; Weishampel and Horner 1992). This character may be related to large size.
On the other hand, Callovosaurus has a bowed femur in lateral view, as occurs in Dryosaurus, Valdosaurus, Kangnasaurus, Camptosaurus , and “hypsilophodontids,” but also in Lesothosaurus (Sereno 1991) and Heterodontosaurus (Santa Luca 1980). The shaft is straight or slightly curved in iguanodontids and nearly straight in hadrosauroids (Godefroit et al. 1998; Norman and Weishampel 1992).
As noted by Galton (1980a) and Galton and Powell (1980), the femur of Callovosaurus differs from that of Camptosaurus ( C. dispar ; see Gilmore 1909) in several respects. In Callovosaurus , the greater trochanter is proportionally narrower; the fourth trochanter is more proximally placed; the depression for the M. caudifemoralis longus is close to the base of the fourth trochanter; the distal end is not thickened anteriorly; and the anterior intercondylar groove is more shallow. A prominent excavation of the medial condyle and the associated prominent edge are present in both dryosaurids and Camptosaurus (Galton 1980b: fig. 3i; Gilmore 1909: figs. 33, 42.1), but it is absent in Iguanodon (see Blows 1998) and derived iguanodontians.
On the basis of femoral features, Callovosaurus leedsi is regarded as a dryosaurid rather than as a hypsilophodontid, camptosaurid, or iguanodontid as previously suggested.
Callovosaurus leedsi as a Valid Taxon of Dryosaurid
Following Sues and Norman (1992), the Dryosauridae comprises four taxa: Dryosaurus altus (Marsh 1878) from the Upper Jurassic Morrison Formation (Kimmeridgian-Tithonian) of the United States (see Galton 1981, 1983b, and references therein); Dryosaurus lettowvorbecki (Virchow 1919) from the Upper Jurassic of the Tendaguru Beds (Kimmeridgian) in Tanzania (see Galton 1981, 1983b; Janensch 1955); Valdosaurus canaliculatus (Galton 1975) from the Lower Cretaceous Wealden Beds (Hastings Sands, Wessex and Vectis Formations; Berriasian-Barremian) of southern England (see Galton 1975; Galton and Taquet 1982; Naish and Martill 2001); and Valdosaurus nigeriensis Galton and Taquet 1982 from the Lower Cretaceous Rhaz Formation (Aptian) of Niger (see Galton and Taquet 1982). Blows (1998) listed D. dextrapoda as part of the fauna of the Wessex Formation of the Isle of Wight, but this was an error (Blows in Naish and Martill 2001), and this taxon is a nomen nudum. Dryosaurus has also been described in the Late Jurassic (Kimmeridgian) of Normandy (Buffetaut and Cacheleux 1997) and Valdosaurus in the Early Cretaceous (Berriasian) of Romania (Benton et al. 1997; Galton and Taquet 1982), but these attributions are based on fragmentary remains.
Other records of dryosaurids include Kangnasaurus coetzeei Haughton 1915 from the Kalahari deposits of South Africa (Cooper 1985). The age of this dryosaurid is uncertain and has variably been considered pre-Aptian by Goodwin et al. 1999), Tithonian-Hauterivian according to Jacobs et al. (1996; although Jacobs 1997 later considered it as Late Cretaceous), and of “unknown age” by Forster (1997); we accept it was Early Cretaceous. K. coetzeei was regarded as a nomen dubium by Sues and Norman (1992), but pending a revision of the material, it is tentatively considered as valid in this work (see Cooper 1985). Other poorly known taxa from the Early Cretaceous of Spain, England, and the United States may also belong to the Dryosauridae (Ruiz-Omeñaca 2001 and work currently in progress). Unnamed dryosaurids from the Late Cretaceous (Campanian-Maastrichtian) are represented by fragmentary remains from New Zealand (Wiffen and Molnar 1989) and, tentatively, from good but undescribed cranial and postcranial material from Antarctica (Hooker et al. 1991). Loncosaurus argentinus Ameghino 1899 from the Late Cretaceous (Mata Amarilla Formation; see Novas 1997) of Argentina could be a dryosaurid because the femur has a pendant fourth trochanter proximally placed and a deep depression for the M. caudifemoralis longus (basitrochanteric fossa of Coria and Salgado 1996b). Unfortunately, the material is too incomplete for an accurate assignment, so it is regarded as belonging to an indeterminate ornithopod (nomen vanum sensu Coria and Salgado 1996b).
The femur is considered to be the most diagnostic postcranial bone for the identification of dryosaurids (Shepherd et al. 1977). The form of the anterior trochanter, the development of the cleft between the anterior and greater trochanters, the form and position of the pit for the insertion of the M. caudifemoralis longus, and the degree of development of the anterior intercondylar groove are useful features to discriminate among dryosaurid taxa.
The femur of Callovosaurus is similar to those of Dryosaurus ( D. altus: YPM 1876; D. lettowvorbecki: MB dy 36 and unpublished material BMNH R6861, R8350, R12277, R12278; see Galton 1977a, 1980b, 1981) and Valdosaurus ( V. canaliculatus: holotype individual BMNH R184, R185; Galton 1975; see Naish and Martill 2001: pl. 7, erroneously referred to as Hypsilophodon foxii; and V. nigeriensis: MNHN GDF 332; Galton and Taquet 1982: pl. 1). It differs in the following characters: more expanded, transversely flattened anterior trochanter (unexpanded, oval to roughly triangular in Dryosaurus and Valdosaurus ); shallow anterior intercondylar groove (deep in Valdosaurus and some specimens of Dryosaurus; see below); and very slightly concave medial surface of the distal end (flat in Valdosaurus and Kangnasaurus; flat or slightly concave in Dryosaurus; see Galton 1980b: figs. 1S-W; Galton 1981: figs. 13B, 14F, 15T, U).
The closest relative of Callovosaurus is Dryosaurus , but there are differences. D. lettowvorbecki , at least, has a smaller and deeper pit for the M. caudifemoralis longus, which is located higher on the shaft and further from the base of the fourth trochanter. Moreover, the anterior intercondylar groove is deeper in Dryosaurus than it is in Callovosaurus , although there are differences in depth in femora of both species of Dryosaurus , with a relatively shallow extensor groove in some femora and a deep one in others (see Galton 1980b: figs. 1S-W). Callovosaurus differs from Valdosaurus in the more distal position of the fourth trochanter (value of the fourth trochanter index 0.48 in Callovosaurus versus 0.41 in Valdosaurus ; Galton 1980a; Galton and Taquet 1982), and a shallower anterior intercondylar groove. Moreover, Callovosaurus leedsi differs from Valdosaurus nigeriensis in that the proximal end of the anterior trochanter is not below that of the greater trochanter and there is no separation between the insertion areas for the M. caudifemoralis longus and the M. caudifemoralis brevis (see Galton and Taquet 1982). Finally, Callovosaurus differs from Kangnasaurus in that the cleft between the anterior and greater trochanters is deep and the greater trochanter does not show the degree of parasagittal expansion seen in the South African dryosaurid (Cooper 1985).
Conclusion
Callovosaurus leedsi (Lydekker 1889) is based on a left femur from the Middle Jurassic (Callovian) Peterborough Member (=lower Oxford Clay) of the Oxford Clay Formation from near Peterborough, England. A reinterpretation of the specimen suggests that Gallovosaurus is more closely related to Dryosaurus and Valdosaurus than to either Hypsilophodon or Camptosaurus , and that it should be referred to the Dryosauridae. Therefore, it represents the oldest dryosaurid known to date.
Dryosaurid femora are characterized by the following combination of characters: bowed shaft (plesiomorphy); proximally placed pendant fourth trochanter (plesiomorphy?); anterior intercondylar groove (synapomorphy of Iguanodontia); well-developed pit for the insertion of the M. caudifemoralis longus (autapomorphy); and transversely reduced lateral condyle, with a condylid internally offset (synapomorphy of Iguanodontia). Dryosaurus, Valdosaurus , and Gallovosaurus have a deep cleft between the greater and anterior trochanters, in contrast to Kangnasaurus , and a proximal excavation to the medial condylar surface that makes a sharp edge with the medial surface of the distal end, as occurs in Camptosaurus. Finally, Gallovosaurus is probably plesiomorphic among dryosaurids in retaining a shallow anterior intercondylar groove and a slightly concave medial surface to the distal end.
Acknowledgments. We thank S. Chapman (BMNH) and Prof. P. Taquet (MNHN) for access to specimens. J. I. R.-O.’s research is supported by the project VECOBA (Ministerio de Ciencia y Tecnología of Spain; ref. BTE 2001–1746) and that of X. P. S. is supported by the Programa Ramón y Cajal of the Ministerio de Ciencia y Tecnología of Spain.
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2. Teeth of Ornithischian Dinosaurs (Mostly Ornithopoda) from the Morrison Formation (Upper Jurassic) of the Western United States
P ETER M. G ALTON
Abstract
Teeth of most ornithischian dinosaur genera from the Morrison Formation of the western United States are well known. These include four genera of Thyreophora, the polacanthid ankylosaurs Gargoyleosaurus and Mymoorapelta (only referred tooth of latter probably Ankylosauria incertae sedis), and the stegosaurid stegosaurs Hesperosaurus and Stegosaurus. Ornithopods include the Fruita heterodontosaurid, the “hypsilophodontids” Othnielosaurus n. gen. and Drinker , the dryosaurid Dryosaurus , and the camptosaurid Camptosaurus. The sixth ornithopod, Nanosaurus , was the first Morrison ornithischian to be described. Although based on barely determinate material, with only a poor mold of the teeth, it is probably a valid taxon. Isolated small teeth from Reed’s Quarry 9 at Como Bluff West, Wyoming, represent juveniles of many of these genera, including three Drinker -like cheek teeth that are tentatively referred to Nanosaurus.
Introduction
Marsh (1877a) described the enigmatic small ornithischian Nanosaurus agilis from Colorado from what would become the Morrison Formation, and since then, much has been published on Morrison ornithischians. Some of these publications include descriptions of the teeth, the characters of which are important in recognizing the different genera. This is especially true for the ornithopods, which represent six of the 10 ornithischian genera from the Morrison, making this the most diverse ornithopod fauna for the Jurassic. However, descriptions of the teeth are scattered through the scientific literature of several different countries, so for the first time, a well-illustrated short characterization of each of the tooth types is presented together (for detailed descriptions, see References Cited).


Figure 2.1. Phylogenetic diagram of the Ornithischia for genera from the Morrison Formation of the western United States (genera listed on right side in order discussed in text), modified from Sereno (1998), who gives details and definitions of the higher taxa shown in the cladogram on the left. Pectinate depiction of “Hypsilophodontidae” based on Scheetz (1998, 1999) and Winkler et al. (1998).
In the last two decades, phylogenetic analyses have provided important information on the interrelationships of ornithischian dinosaurs, so because of this, the Morrison teeth are discussed within a phylogenetic framework ( Fig. 2.1 ; for further details, see Sereno 1986, 1997, 1998). The positions of the higher taxonomic categories used in the text are indicated on the left of Figure 2.1 and the genera recognized from the Morrison Formation of the western United States are listed on the right side in the same descending order as they are discussed in the text. Records of the genera that also occur outside of North America are discussed.
Many productive quarries are now known in the Morrison Formation (Upper Jurassic, Kimmeridgian-Tithonian, ~155–148 Ma; Turner and Peterson 1999) of the Western Interior of the United States, occurring in the Salt Wash Member and especially in the overlying Brushy Basin Member. The stratigraphic positions of most of the quarries mentioned in this chapter, with a list of the dinosaurs from each, are given by Turner and Peterson (1999), as is the range for each of the genera. More details, including the history and complete faunal lists for the vertebrates, are available for the quarries that produced most of the species mentioned in this paper, viz., those in the Garden Park Paleontological Resource Area north of Canon City, Fremont County, Colorado (Carpenter 1997, 1998, 2002; McIntosh 1990; Ostrom and McIntosh 1966, 1999), and especially those near Como, Albany County, Wyoming (Breithaupt 1997; McIntosh 1990; Ostrom and McIntosh 1966, 1999). Isolated small ornithischian teeth came from Reed’s Quarry 9 at Como Bluff, Albany County, Wyoming, and this is undoubtedly the richest single source of terrestrial vertebrate species discovered to date from the Jurassic (see Clemens et al. 1979; Gilmore 1909a; Ostrom and McIntosh 1966, 1999; Simpson 1926, 1929).
Institutional Abbreviations. AMNH: American Museum of Natural History, New York; BMNH: Natural History Museum (formerly the British Museum [Natural History]), London; BYU ESM: Earth Science Museum, Brigham Young University, Provo, Utah; CEUM: College of Eastern Utah Prehistoric Museum, Price; CM: Carnegie Museum of Natural History, Pittsburgh, Pennsylvania; DMNH: Denver Museum of Nature & Science (formerly Denver Museum of Natural History), Denver, Colorado; HMNH: Hayashibara Museum of Natural History, Okayama, Japan; LACM: Los Angeles County Museum, Los Angeles; MB: Berlin Museum für Naturkunde (formerly Humboldt Museum für Naturkunde), Berlin; MCZ: Museum of Comparative Zoology, Harvard University, Cambridge; OUMNH, Oxford University Museum of Natural History, Oxford; UCM: University of Colorado Museum, Boulder; USNM: National Museum of Natural History (formerly United States National Museum), Washington, D.C.; and YPM, Peabody Museum of Natural History, Yale University, New Haven, Connecticut.
Systematic Paleontology
Ornithischia Seeley 1887
Genasauria Sereno 1986
Thyreophora Nopsca 1915
Ankylosauria Osborn 1923
Polacanthidae Wieland 1911
Gargoyleosaurus parkpinorum Carpenter et al. 1998


Figure 2.2. Restoration in left lateral view of the skulls of Morrison ornithiscbians (A–C, E) and related species from the Upper Jurassic of East Africa (D) and England (F). (A) Polacanthid ankylosaur Gargoyleosaurus parkpinorum, after Carpenter et al. (1998). (B) stegosaurid stegosaur Stegosaurus stenops, from Galton (1997). Dryosaurid Dryosaurus, from Galton (1983b): (C) D. altus and (D) D. lettowvorbecki. Camptosaurid Camptosaurus: (E) C. amplus, from Marsh (1896), and (F) C. prestwichii, from Galton and Powell (1980). Scale bars = 5 cm.


Figure 2.3. Thyreopbora. Teeth of ankylosaurs (A–C) and stegosaur (D–F) from the Lower Cretaceous (A) and the Upper Jurassic of the western United States. (A) Cheek tooth of polacanthid Gastonia burgei, referred specimen CEUM 1307. A premaxillary (B) and a maxillary (C) tooth of Gargoyleosaurus parkinorum, holotype DMNH 27726. Cheek tooth of stegosaurid Hesperosaurus mjosi, holotype HMNH 001 in (D) buccal, (E) ?anterior, and (F) ?lingual views. Photographs supplied by Kirkland (A) and Carpenter (B–F). Scale bars = 0.5 mm (A), 5 mm (B, C), 2 mm (D–F).
This taxon of armored dinosaur, which is based on a skull ( Fig. 2.2A ; photos Kirkland et al. 1998: fig. 12) and associated postcrania (DMNH 27726), came from Bone Cabin Quarry West on the Medicine Bow Anticline, Albany County, Wyoming. It was described as an ankylosaurid but it is now included in the Polacanthidae in the phylogenetic analysis of the Ankylosauria by Carpenter (2001; see also Blows 2001). There are seven teeth in the premaxilla, 22–23 in the maxilla, and ~26 in the dentary. Although the teeth were not figured, Carpenter et al. (2001) noted that the premaxillary teeth are conical and slightly compressed with denticles along their margins ( Fig. 2.3B ), resembling those of the primitive stegosaur Huayangosaurus (Middle Jurassic, China; Sereno and Dong 1992). The simple leaf-shaped cheek teeth with slightly expanded bases ( Fig. 2.3C ) are similar to those of primitive ornithischians such as Lesothosaurus (Lower Jurassic, southern Africa; Sereno 1991). Carpenter (personal communication) notes that the premaxillary teeth look like those of the ornithopod Thescelosaurus (Upper Cretaceous, western North America; Galton 1974a), although slightly more compressed transversely, and the cheek teeth, which are plesiomorphic in lacking the bandlike cingulum and swollen crown of most ankylosaurs, quite closely resemble those of the ankylosaurs Sarcolestes (Middle Jurassic, England; Galton 1983a) and Gastonia ( Figs. 2.3A , 2.5A–C; Lower Cretaceous, Utah; Kirkland 1998).


Figure 2.4. Thyreopbora. Small cheek teeth from Reed’s Quarry 9, Como Bluff West, Wyoming. Stegosauridae incertae sedis: (A–C) YPM 1938, from Marsh (1896). (D–F) USNM 7474. Ankylosauria incertae sedis: (G–I), YPM 7453. Views: apical (C); the rest are uncertain — lingual or labial (A, D, F, G, I) and mesial or distal (B, E, H). Scale bars = 2 mm (A–C), 1 mm (D–I).


Figure 2.5. Thyreopbora teeth. Isolated right maxillary tooth (inverted) of polacanthid ankylosaur Gastonia burgei (Lower Cretaceous, Utah) in (A) buccal, (B) apical, and (C) lingual views, from Kirkland (1998). Stegosaurid stegosaur Stegosaurus stenops, holotype USNM 4934, (D) most of dentition of right maxilla (plus some dentary teeth) in internal view, from Gilmore (1914). a: portion of lower jaw crushed up on outside of maxilla; b: maxilla; c: replacement teeth; d: anterior end (with further preparation in mid-1980s, the first tooth shown is now the fifth; see Fig. 6A); (E) right maxillary tooth 19 (inverted); (F) right dentary tooth 21. (G) Tooth of juvenile individual of Stegosaurus sp., YPM 1885, holotype of Diracodon laticeps, right dentary tooth 11 in lingual view (for photo in buccal view, see Carpenter and Galton 2001: fig. 4.16D). Isolated stegosaurid cheek tooth, AMNH 11524 from Reed’s Quarry 9, Como Bluff West, Wyoming, in labial or lingual (H, J) and mesial or distal views (I). Scale bars = 2 mm (A–C), 1 mm (E–J), ~10 mm (D).


Figure 2.6. (opposite page) Stegosaurid stegosaur Stegosaurus stenops, holotype USNM 4934, right jaws in internal (lingual) view. (A) Complete tooth row of right maxilla (plus some dentary teeth) after further preparation by A. Lewis in the mid-1980s (cf. Fig. 2.5D ). Note that lighting in (A) is from below, whereas in (B–D) the teeth are inverted to give normal lighting. (B) Dentary teeth 21 and 20 and maxillary tooth 20. (C, D) Maxillary teeth, unworn crown 17 (C) and crowns 9 and 8 showing wear surfaces (D). Heterodontosaurids: LACM 128258 from Fruita, Colorado, jaws with teeth, posterior part of right maxilla (E) and almost complete right dentary (F) in lateral view. (G) Middle right maxillary teeth in labial view, LACM 115747. Echinodon becklesii Owen 1861 from Lower Cretaceous of England: lectotype, a split slab: (H) part of left premaxilla and composite reconstruction of maxilla; anterior part (BMNH 48209) in lateral view combined with posterior part (BMNH 48210) in medial view (printed in reverse); the teeth of posterior block were aligned with impressions on the anterior block; (I) detail of anterior part of left maxilla BMNH 48209 in labial view to show first three teeth. Two-thirds of tooth row in labial view, posterior part of left dentary BMNH 46213 (J) and anterior part of right maxilla BMNH 48211 (K). (L) Nanosaurus agilis Marsh 1877a, lectotype YPM 1913a, latex cast of right dentary in lateral view, a: alveolus for caniniform tooth; c: small and large caniniform teeth. Scale bars = ~10 mm (A), 1 mm (B–K), 10 mm (L).
The other Morrison polacanthid is Mymoorapelta maysi Kirkland and Carpenter 1994 (Carpenter 2001), for which only parts of the skull are known but no teeth (Carpenter, personal communication), despite the abundance of postcranial material (Kirkland et al. 1998).
Ankylosauria incertae sedis
YPM 7453 ( Fig. 2.4G–I ), a small crown with a proportionally large bandlike cingulum from Reed’s Quarry 9 at Como Bluff, Wyoming, looks ankylosaurian rather than stegosaurian (and definitely not ornithopod). It is certainly not referable to Gargoyleosaurus , in which the cheek teeth lack a cingulum ( Fig. 2.3C ; Carpenter et al. 1998), so it may be from Mymoorapelta , but at the moment it is best identified as Ankylosauria incertae sedis. This tooth was collected in the 1880s, more than 100 years before the first ankylosaurs were recognized from the Morrison Formation by Kirkland and Carpenter (1994). In Europe, Jurassic ankylosaurs were first recognized in the 1980s, even though several specimens were described from England up to a hundred years earlier or more (see Galton 1980a, 1983a). In Sarcolestes (Middle Jurassic, England) the most anterior dentary tooth is caniniform with fine serrations perpendicular to the edge. Two associated but isolated teeth, resembling the caniniform of Sarcolestes and a cheek tooth of Gastonia ( Figs. 2.3A , 2.5A–C ), were described as the fabrosaurid ornithopod Gongbusaurus shiyii Dong et al. 1983 (early Late Jurassic, China; color photo in Dong and Milner 1988: 50). This taxon is a nomen dubium that is probably incertae sedis as Ankylosauria rather than Ornithopoda.
Stegosauria Marsh 1877b
Stegosauridae Marsh 1880
Stegosaurus stenops Marsh 1887
The type species of the plated dinosaur genus Stegosaurus, S. armatus Marsh 1877b, is based only on postcranial material (YPM 1950) from Lakes’s Quarry 5 at Morrison, Jefferson County, Colorado (Ostrom and McIntosh 1966, 1999; Carpenter 1998). It was figured for the first time by Carpenter and Galton (2001); the dentition as initially described by Marsh (1880) was based on premaxillae supposedly found with the holotype, but which turned out to be from the sauropod dinosaur Diplodocus (Carpenter and Galton 2001: 97; Marsh 1884). The holotype skeleton (YPM 1853; Carpenter and Galton 2001) of Stegosaurus ungulatus Marsh 1879 from Reed’s Quarry 12 at Como Bluff West, Wyoming, includes a partial skull but no teeth (Galton 2001). The almost complete holotype skeleton (USNM 4934; Gilmore 1914) of S. stenops Marsh 1887 from Felch Quarry 1 at Garden Park, Colorado (details in Evanoff and Carpenter 1998), has a complete skull ( Fig. 2.2B ), the teeth of which were described by Gilmore (1914) ( Fig. 2.5D ).
The premaxilla of Stegosaurus stenops is edentulous ( Fig. 2.2B ), and each maxilla and dentary has about 24 and 23 teeth, respectively, with little variation in form ( Figs. 2.5D–F , 2.6A–D ). The maxillary teeth have a transversely compressed, vertically striated crown, with the labial (=lateral or buccal) face slightly concave vertically and the lingual (—edial) face slightly convex. The apical denticle is median with the edge on either side bearing from four to seven denticles, each being rounded in cross section with a blunt point. Most of the crown is covered by striations formed by numerous fine subvertical and irregularly textured ridges. The base of the crown has a rounded cingulum that is more pronounced labially, and the root is long. The teeth show a slight degree of asymmetry when viewed in mesial (=anterior) or distal (=posterior) views, with the maxillary tooth crowns curving slightly lingually, as against slightly labially for dentary teeth. As a result, some of the opposing teeth came into direct occlusion so a few teeth have obliquely inclined tooth-to-tooth wear facets ( Figs. 2.5D, F , 2.6B, D ) (Barrett 2001). The undescribed teeth of a referred skull of S. stenops (DMNH 33365, Carpenter et al. 2001: fig. 3.4C ) from near the type quarry (Evanoff and Carpenter 1998) closely resemble those of the type skull (Carpenter, personal communication).
The holotype of Diracodon laticeps Marsh 1881, a nomen dubium, represents a juvenile individual of Stegosaurus sp., and it consists of two imperfect maxillae with a few teeth (YPM 1885; Carpenter and Galton 2001: 98–99, figs. 4.16, 4.17) from Reed’s Quarry 13 at Como Bluff East, Wyoming (details in Gilmore 1909b, 1914). The crowns of these teeth differ from those of adults in being more spherical with less prominent vertical striations ( Fig. 2.5G ).
Hesperosaurus mjosi Carpenter et al. 2001
The holotype (HMNH 001, cast as DNMH 29431) consists of a fairly complete disarticulated skull and skeleton, lacking the limbs, from the base of the Morrison Formation from near Buffalo, Johnson County, Wyoming. Hesperosaurus was described as being closer to Dacentrurus (Upper Jurassic, Western Europe; Galton 1985) than Stegosaurus but a more detailed cladistic analysis places it with Lexovisaurus (Middle Jurassic, Western Europe; Galton 1985) next to Stegosaurus (Galton and Upchurch 2004). The missing premaxilla of Hesperosaurus was presumably edentulous, the dentary is incomplete, and there are 20 alveoli in the maxilla. The cheek teeth are described as being proportionally larger, relative to skull size, but otherwise are similar to those of Stegosaurus (Carpenter et al. 2001). However, the tooth illustrated ( Fig. 2.3D–F ) differs from those of the type skull of S. stenops ( Figs. 2.5D–F , 2.6A–D ; also those of referred skull DMNH 33365, Carpenter, personal communication) in having coarse rounded subvertical ridges covering the apical half of the crown, one per marginal denticle, and the fine striations are only weakly developed.
Stegosauridae incertae sedis
There are quite a few small isolated cheek teeth in collections (AMNH, USNM, YPM) from Reed’s Quarry 9 at Como Bluff, Wyoming, that were originally identified as “juvenile Stegosaurus ,” and although this identification is usually incorrect, it may be true in a few cases. YPM 1938 ( Fig. 2.4A–C ), the tooth used by Marsh (1892, 1896, as S. ungulatus ) and by Gilmore (1914) to characterize the teeth of Stegosaurus , is obviously from a juvenile individual (as shown by size). It differs from the tooth crowns of the adult skull of S. stenops ( Figs. 2.5D–F , 2.6A–D ) in having less marginal denticles, each of which has a supporting vertical rounded ridge. It has no surface texture, possibly a juvenile character for Stegosaurus as in the ornithopod Othnielosaurus (see below), or it could be from Hesperosaurus (cf. Fig. 2.3D–F ). Another small tooth (USNM 7474, Fig. 2.4D–F ) is more convincing as a juvenile Stegosaurus , but both should be identified as Stegosauridae incertae sedis. The same is true for an isolated cheek tooth crown (AMNH 11524, Fig. 2.5H–J ) identified as Stegosaurus sp. by Galton (1990: fig. 21.4B–D; also Barrett 2001: fig. 2.7B ) of a rather different form from those of S. stenops ( Figs. 2.5D–F , 2.6A–D ), being more cone shaped than leaflike, with very prominent and irregular ridging and grooving, plus a proportionally larger cingulum.
Neornithischia Cooper 1985
Ornithopoda Marsh 1881
Heterodontosauridae Kuhn 1966
Fruita Jaws
Callison and Quimby (1984: fig. 3B, C) figured a femoral shaft and distal end of a tibia with an astragalus-calcaneum as those of a small fabrosaurid ornithischian dinosaur. The specimen is from the base of Brushy Basin Member in the Fruita Paleontological Area northwest of Grand Junction, Colorado (Evans 1996; Kirkland 1994, 1997). Later, on the basis of jaws with teeth, these and other bones were identified as Echinodon (Callison 1987; Galton 2002; Olshevsky and Ford 1994: 79, fig. 14), a small ornithischian represented by several jaws with teeth from the Lower Cretaceous of southern England (Galton 1978; Owen 1861). In recent years, Echinodon has been referred to the Heterodontosauridae (Barrett 1999; Galton 2002; Norman and Barrett 2002; Olshevsky and Ford 1994; Sereno 1991, 1997). The Fruita material is being described elsewhere as a new genus and the preserved limb bones (proximal portion of a humerus, femur, tibia, and fibula with astragalus-calcaneum) are very similar to those of Heterodontosaurus tucki (Lower Jurassic, South Africa; Galton 2002; Santa Luca 1980), as are the postcranial bones of an undescribed heterodontosaurid from the Kayenta Formation (Lower Jurassic, Arizona; Sereno 1986).
The Fruita teeth ( Figs. 2.6E–G , 2.7A–G ) and those of Echinodon ( Figs. 2.6H–K , 2.7H–K ; see Naish and Martill 2001: fig. 5.5A, B for photos of dentary teeth of BMNH 48215b, not Hypsilophodon as labeled) are superficially similar. However, there are five (versus three in Echinodon ) premaxillary teeth, the cheek crowns have a few secondary vertical ridges and rugosities (versus none), and the denticles of middle cheek teeth occupy over half of the apical part of the crown (versus less than a third) with an obtuse angle (versus acute) between the ridges (absent on some Fruita teeth; Fig. 2.7D, E ) that diverge from each side of the base of the crown to the most proximal denticle (ridges of same side overhang the root and converge to a point; Fig. 2.7F, K ). No maxillae from Fruita have the anterior part preserved, but a dentary has a large caniniform tooth ( Fig. 2.6F , another a large root in the alveolus), much as in the holotype maxilla of Echinodon ( Figs. 2.6H, I , 2.7H, I ). In Echinodon there are indications of a larger transversely crushed alveolus anteriorly in dentaries with this part preserved (contra Galton 2002).


Figure 2.7. Heterodontosaurid specimens from Fruita, Colorado. Jaws with teeth in lateral view, LACM 128258, posterior part of right maxilla (A) and almost complete right dentary (B); maxillary teeth LACM 115747 (all inverted): middle right in labial view (C), posterior left in labial (D) and mesial views (E), middle left in distal (F) and labial views (G). Echinodon becklesii from Lower Cretaceous of England. (H) Reconstruction based on lectotype and paralectotypes BMNH 48209–15 (dentary caniniform tooth shed so not shown and there should probably be 10 instead of 11 maxillary teeth, cf. Fig. 2.6H ); tooth rows in labial view, anterior part of right maxilla BMNH 48211 (I) and right dentary BMNH 46213 (J). (K) Middle left maxillary tooth BMNH 48210 ( Fig. 2.6H , right end) in mesial view (inverted), after Owen (1861). Nanosaurus agilis Marsh 1878, (L) YPM 1913b, paralectotype, right ilium in lateral view; (M, N) YPM 1913a, lectotype, latex cast of right dentary in lateral view (M, cf. Fig. 2.6L ) and detail of tooth row (N). Plates (A, B) from Olshevesky and Ford (1994), (H-N) from Galton (1978). Scale bars = 5 mm (A, B, H–J, L–N), 1 mm (C–G, K).
Euornithopoda Sereno 1986
“Hypsilophodontidae” Dollo 1882
Basal ornithopods are commonly referred to the Hypsilophodontidae (e.g., Sereno 1998; Sues 1997; Sues and Norman 1990; Weishampel and Heinrich 1992). However, the cladistic analysis of Scheetz (1998, 1999) shows that this traditional broad based grouping is a pectinate grade ( Fig. 2.1 ). In addition, Winkler et al. (1998) indicate that morphological variation within a large population of a new ornithopod from the Lower Cretaceous of Fexas destabilizes the Hypsilophodontidae and that its members are best regarded as an array of successive sister groups to the Iguanodontia ( Fig. 2.1 ).
Othnielosaurus n.g.
O. consors (Marsh 1894)
Nanosaurus rex Marsh 1877c, the type species of Othnielia Galton 1977, is based on YPM 1875, a femur from Garden Park, Colorado. In a letter to Marsh, Felch mentions that it occurred higher than the main bone level at Quarry 1 (Carpenter, personal communication). Unfortunately, the holotype femur (Galton 1983b: fig. 6A-E; Galton and Jensen 1973a: pl. 3) has no autapomorphies, closely resembling the femur of the holotype skeleton of Drinker nisti (Bakker 1996: fig. 5), so Nanosaurus rex is a nomen dubium, as is Othnielia. However, the derived characters of Othnielia are mostly based on a partial referred skeleton with jaws (YPM 1882, Reed’s Quarry 7, Como Bluff West, Wyoming; Galton 1983b), the holotype of Laosaurus consors Marsh 1894, which is made the type species of Othnielosaurus n. gen. The referred partial skeleton of Othnielia rex from near Willow Springs, Emery County, Utah, is here referred to Othnielosaurus consors (Marsh 1894) (see Galton and Jensen 1973a as BYU ESM-163R; and Galton 1983b as MCZ 4454; but the latter now refers to a cast, with the original specimen as BYU ESM 163).


Figure 2.8. Othnielosaurus consors n. gen., YPM 1882 ( holotype of Laosaurus consors Marsh 1894) from Reed’s Quarry 7, Como Bluff West, Wyoming. Right maxillary tooth in lingual (A), distal (B), and labial views (C). Left maxillary tooth in lingual view (D). Right in situ maxillary tooth in labial view (E). Left in situ dentary tooth in lingual view (F). Left dentary tooth in mesial (G), labial (H), and lingual views (I). From Galton (1983b). Scale bar = 5 mm.
The holotype skeleton of Othnielosaurus consors , YPM 1882, includes jaws containing replacement teeth ( Figs. 2.8E, F , 2.10J, K ) plus associated loose functional teeth ( Figs. 2.8A–D, G–I , 2.9A–F ) (Galton 1983b). On maxillary crowns, the lingual face is nearly vertical, whereas the labial face is more inclined and extends further upward ( Figs. 2.8B, G , 2.9B, E , 2.11H, I ). This marked asymmetry of the maxillary teeth is also found in Drinker ( Fig. 2.11G ) and in nearly all other Upper Jurassic and Cretaceous ornithopods. However, the dentary tooth roots in Othnielosaurus (and Drinker ) are long and straight ( Fig. 2.9B ), lacking the outwardly convex curvature seen in Hypsilophodon ( Fig. 2.14C, D ; Lower Cretaceous, England; Galton 1974b), Dryosaurus ( Fig. 2.16C, E ), Camptosaurus ( Fig. 2.17B, H–J ), iguanodontids, and hadrosaurids (Bakker et al. 1990). The crowns of the cheek teeth are ornamented with a fine texture of pustules and beaded ridges that form irregular subvertical rows. This texture is more strongly developed on the convex surface. The cingulum is smooth and shiny.


Figure 2.9. Othnielosaurus consors n. gen., YPM 1882, bolotype of Laosaurus consors from Reed’s Quarry 7, Como Bluff West, Wyoming. (A–C) Left dentary tooth in lingual (A), mesial (B), and labial (C) views. (D–F) Left maxillary tooth in lingual (D), distal (E), and labial views (F). (G–I) Referred left dentary tooth of a juvenile individual AMNH 2372 (Cope Collection) from Wyoming in lingual (G), distal (H), and labial (I) views. Dryosaurus altus YPM 1876, lectotype of Laosaurus altus, from Reed’s Quarry 5, Como Bluff West, teeth in lingual view from anterior (J) and posterior (K) parts of right dentary. Scale bars = 1 mm (A–I), 5 mm (J, K).
The isolated premaxillary tooth AMNH 14328 ( Fig. 2.12O–Q , previously referred to Othnielia by Galton 1983b) has a reduced number of regular marginal denticles, rather than an unreduced number of irregular denticles as in Drinker ( Fig. 2.11B ), so this tooth may be referable to Othnielosaurus (certainly not ankylosaur Gargyleosaurus , Fig. 2.3B ).
Another premaxillary tooth (YPM 9522; Fig. 2.10L–N ) was referred to Othnielia by Galton (1983b), but given the uniform size of the marginal denticles compared to their irregular form in the holotype of its close relative Drinker ( Fig. 2.11B ), this referral may be incorrect. However, this tooth is similar to those of Gargoyleosaurus ( Fig. 2.3B ), so it is best identified as Ornithischia incertae sedis. The overall form of the crown of the dentary tooth AMNH 2372 ( Figs. 2.9G–I , 2.12A–C ) is almost identical to one from the holotype of Othnielosaurus consors ( Figs. 2.8G–I , 2.9A–C ), so although the enamel of the crown is smooth and shiny, and lacks surface ornamentation, this tooth can confidently be referred to Othnielosaurus. This referral is also true for the maxillary tooth AMNH 11526 ( Fig. 2.12D, E ), but it is more tentative for the other small teeth ( Fig. 2.10A–G ) that were referred to Othnielosaurus (as Othnielia rex ) by Galton (1983b).


Figure 2.10. Presumed juvenile individuals from Reed’s Quarry 9, Como Bluff West, Wyoming. Tentatively referred to Othnielosaurus consors, right dentary tooth YPM 7454 (YPM 7457 in Galton 1983b: 228) in lingual (A) and labial views (B). Right dentary tooth YPM 7452 in lingual (C) and labial views (D); left maxillary tooth YPM 7451 (inverted) in lingual (E), labial (F), and mesial views (G). Tentatively referred to Nanosaurus agilis, right maxillary tooth YPM 9524 (inverted) in labial (H) and lingual views (I). Othnielosaurus consors n. gen., in situ teeth of YPM 1882, holotype of Laosaurus consors from Reed’s Quarry 7, Como Bluff West, left dentary tooth in lingual view (J) and right maxillary tooth in lingual view (K). Ornithischia incertae sedis, left premaxillary tooth YPM 9522 in lingual (L), labial with sectional ventral (M), and mesial views (N). From Galton (1983b). Scale bars = 1 mm.


Figure 2.11. Drinker nisti, holotype from Como Bluff West, Wyoming, right premaxillary tooth in lingual view (A) with detail of distal edge (B); left anterior dentary tooth with complete tooth (C) and crown in labial (D) and distal views (E); right maxillary tooth (left reversed) in lingual (F) and distal views (G). Othnielosaurus consors, referred specimen UCM Field No. C-1–1984 from near Felch Quarry, Oil Creek, Colorado, right maxillary tooth in lingual (H) and distal views (I). Scale bars = 5 mm (A), 0.5 mm (B), 2 mm (C), 1 mm (D–I). From Bakker et al. (1990).


Figure 2.12. Small teeth of Othnielosaurus consors, left dentary tooth from Wyoming (Cope Collection), AMNH 2372 in lingual (A), distal (B), and labial views (C); left maxillary tooth (inverted) from Reed’s Quarry 9 at Como Bluff West, AMNH 11526 in labial (D), lingual (E), and distal views (F); left dentary USNM 5829 from Garden Park, Colorado, with replacement teeth, 13 in lingual view (G) and 10 in labial (H) and lingual views (I), and functional tooth 9 in labial view (J). Phyllodon henkeli from Upper Jurassic of Guimarota mine near Leira, Portugal, holotype right dentary tooth in lingual (K), mesial (L), labial (M), and distal views (N), after Thulborn (1973). Left premaxillary tooth from Reed’s Quarry 9 at Como Bluff West, AMNH 14328 in lingual (O), distal (P), and labial views (Q). From Galton (1983b). Broken surfaces unshaded. Scale bars = 1 mm.


Figure 2.13. Small cheek teeth of Nanosaurus agilis from Reed’s Quarry 9, Como Bluff West, Wyoming, right maxillary tooth YPM 9524 (YPM 9523 in Galton 1983b) in distal (A), lingual (B), mesial (C), and labial views (D); left maxillary tooth YPM 9523 (YPM 9524 in Galton 1983b) in distal (E), lingual (F), mesial (G), and labial views (H); right dentary tooth YPM 9525 in lingual (I), mesial (J), labial (K), and distal views (L). Broken surfaces unshaded in B, C, F, I–L, occlusal surface unshaded in E and F. Scale bar = 1 mm.


Figure 2.14. Hypsilophodon foxii from Lower Cretaceous of England. (A) Holotype skull BMNH R197 (see Galton 1974b), left maxillary tooth row and part of dentary row in lateral (labial) view (see Galton 1974b: fig. 2A; Naish and Martill 2001: pl. 3, fig. 1); left dentary teeth BMNH R196 in lingual view (B) and right dentary tooth BMNH R8367 in lingual (C) and labial views (D) (see Galton 1974b: fig. 15). Photographs from BMNH. Scale bars = 1 mm.


Figure 2.15. Dryosaurus altus from Como Bluff West, Wyoming; lectotype YPM 1876 from YPM Quarry 5, middle right maxillary tooth in labial (A) and lingual views (B); left dentary tooth with tooth-to-tooth wear surface in lingual (C) and labial views (D); right dentary teeth in lingual view — an anterior (E) and a posterior (F) tooth ( Fig. 2.9, K ). YPM 9521 from Reed’s Quarry 9, left maxillary tooth in labial (G) and lingual views (H). From Galton (1983 b). Scale bar = 5 mm.
Drinker nisti Bakker et al. 1990
Drinker is based on a partial skeleton of a subadult individual with parts of the jaws plus other specimens from Big Nose Quarry, Como Bluff West, Wyoming (Bakker et al. 1990; Bakker 1996: fig. 5). The mesial and distal keels of the premaxillary teeth are unusual in bearing complex asymmetrical denticles ( Fig. 2.11 A, B ). The cheek teeth ( Fig. 2.11C–G ) resemble those of Othnielosaurus ( Figs. 2.8 , 2.9A–F , 2.10J, K , 2.11H, I ), including the fine textured ornamentation that is not shown on the drawings. However, the marginal denticles of the mesial and distal edges of Drinker are much more complex, each consisting of a central cusplet and adjacent blades reinforced with ridges ( Fig. 2.11D–G ), and in addition, the cingulum of the distal half of the lingual base of the crown of maxillary teeth bears a prominent, sharp edge with three sharply pointed, conical cusps ( Fig. 2.11F, G ). In these respects the teeth resemble those of Phyllodon henkeli ( Fig. 2.12K–N ; Upper Jurassic, Portugal; Thulborn 1973; Rauhut 2001); in Othnielosaurus this area of the cingulum has only a slight swelling without a sharp edge or cusps ( Figs. 2.8A , 2.9D , 2.11H, I ).
Nanosaurus agilis Marsh 1877a
Nanosaurus agilis Marsh 1877a is regarded as Ornithischia incertae sedis by Sereno (1991) and as a nomen dubium by Sues and Norman (1990) because of the indeterminate nature of the teeth ( Figs. 2.6L , 2.7M, N ) and of the other bones of the syntype (YPM 1913; see Galton 1978; Huene and Lull 1908). However, the cleft between the slender anterior (=lesser; see Carpenter and Kirkland 1998) trochanter and the greater trochanter of the femur is very shallow, as in the Fruita heterodontosaurid (in which anterior trochanter is very swollen as in Heterodontosaurus; Galton 2002), rather than deep as in the other Morrison ornithopods. In addition, the high pointed form of the posterior end of the ilium in lateral view ( Fig. 2.7L ) is unique for Morrison ornithischians. Consequently, Nanosaurus agilis is the sixth Morrison ornithopod, the presence of which is possibly indicated by three teeth from Reed’s YPM Quarry 9 at Como Bluff, Wyoming.


Figure 2.16. Dryosaurus tooth rows. D. altus, skull CM 3392 ( Fig. 2.2C ) from Dinosaur National Monument, Utah, right maxillary teeth 13 to 5 in labial view (A) and left dentary teeth in labial (B) and lingual views (C). D. lettowvorbecki from Upper Jurassic of Tanzania, East Africa, MB dy B, right maxillary teeth in labial view (D) and right dentary teeth in lingual view (E). D. altus, YPM lost, paralectotype, isolated left maxillary tooth (inverted) in labial (F), lingual (G), mesial (H), and distal views (I). From Galton (1983b). Scale bars = 10 mm (A–C), 5 mm (D–F).
The left dentary tooth YPM 9524 ( Fig. 2.10H, I ) that Galton (1983b: 242, fig. 11G–I, pl. 4, figs. 27, 28 as YPM 9523) referred to Nanosaurus agilis was reidentified by Bakker et al. (1990) as an anterior maxillary tooth of Drinker nesti (presumably a right). Some of the apical marginal denticles show traces of a tripartite form ( Fig. 2.13B, D ), as does the somewhat similar holotype tooth of Phyllodon henkeli ( Fig. 2.12K–N , Upper Jurassic, Portugal; Rauhut 2001; Thulborn 1973), but lingually, the cingulum on the distal part has a very prominent edge that bears several denticles ( Fig. 2.13A, B ). However, the crown shape differs from the only figured maxillary tooth of Drinker ( Fig. 2.11D ) in being symmetrical in lingual or labial views ( Fig. 2.13B, D , as in Phyllodon Fig. 2.12K, M ), rather than being asymmetrical with a convex mesial edge (also in Othnielosaurus ). The second tooth, originally figured (but only as poor quality photographs) as a left maxillary tooth (YPM 9523; Galton 1983b: 242, pl. 4, figs. 29, 30 as YPM 9523), has a large tooth-to-tooth wear surface but it is even more distinctive ( Fig. 2.13E–H ). The third tooth, from the right dentary (YPM 9524, Fig. 2.13I–L ), resembles the dentary teeth of Othnielosaurus and Drinker , but differs from both because lingually the cingulum bears a thin edge on its distal part ( Fig. 2.13K, L ). These teeth may represent a new taxon distinct from Othnielosaurus and Drinker , but given that these are isolated teeth, they are tentatively referred to Nanosaurus agilis , the only Morrison ornithopod for which the exact form of the teeth is not known.


Figure 2.17. Camptosaurus teeth. C. dispar from Reed’s Quarry 13, West Como Bluff, Wyoming; left tooth rows of YPM 1886, left maxilla in labial view (A) and of dentary in labial (B) and lingual views (C), from Gilmore (1909a). YPM 1880,holotype of C. medius, 10th maxillary tooth (D–F) and fifth dentary tooth (G–I) in labial (D, G), distal (E, H), and lingual views (F, I), from Galton (1983b). (J) Camptosaurus hoggii, holotype BMNH R2998 from Lower Cretaceous of England, right mandible in medial view, from Owen (1874). Scale bars = 10 mm (A–C, J), 5 mm (D–I).


Figure 2.18. Camptosaurus teeth. C. dispar from Reed’s Quarry 13, West Como Bluff. (A, B) Teeth of right maxilla YPM 7416 in labial view; dentary teeth in lingual view, (C) teeth 8–5 (cf. Fig. 2.17C ) of left dentary YPM 1886 (C), of right dentary USNM 5819 (D) and of right dentary YPM 1877 (E). C. prestwichi, holotype OUMNH J3303 from Upper Jurassic of England, adjacent teeth on right maxilla in labial view (F) and lingual views of dentary teeth from left (G) and right sides (H). (I) Camptosaurus hoggii, holotype BMNH R2998 from Lower Cretaceous of England, right mandible in medial view. Scale bars = 5 mm (A–H), 10 mm (I).
Hypsilophodon -grade ornithopod
Genera with a Hypsilophodon grade of cheek teeth ( Fig. 2.14 ; Galton 1974b; Naish and Martill 2001) do not occur in the Morrison Formation. This is surprising because a worn dentary tooth of Hypsilophodon sp. is described by Thulborn (1973: fig. 26) from the Upper Jurassic (Kimmeridgian) of Portugal, and in addition, genera with a more advanced tooth form, Dryosaurus and Camptosaurus , do occur in the Morrison. Hypsilophodon foxii is plesiomorphic in retaining five premaxillary teeth (Galton 1974b; Naish and Martill 2001: pl. 4, figs. 1, 2). In the cheek teeth ( Fig. 2.14 ; Scheetz 1999), the roots are curved so the crowns are strongly angled relative to the root, the crown enamel is thicker on the more convex surface (labial for maxillary and lingual for dentary teeth) and thinner on the other, vertically concave surface ( Fig. 2.14D ) (rather than being uniformly enameled). In addition, the convex thickly enameled surface bears primary (through apical denticle to base of crown) and secondary ridges, with the primary ridge of the dentary teeth being extremely prominent ( Fig. 2.14C ), and very few denticles are supported by ridges. The maxillary teeth have tapering roots and lack a distinct neck between the crown and the root ( Fig. 2.14A ).
Iguanodontia Dollo 1888
Dryosauridae Milner and Norman 1984
Dryosaurus altus (Marsh 1878)
Laosaurus altus Marsh 1878, the type species of Dryosaurus Marsh 1894, is based on a fairly complete skeleton (YPM 1876), including partial jaws with teeth (Galton 1983b), from Reed’s Quarry 5, Como Bluff West, Wyoming; a complete skull ( Fig. 2.2C ) with most of the postcranial skeleton (CM 3392) came from Dinosaur National Monument, Utah (Galton 1981, 1983b; Gilmore 1925; for details on quarry, see Gilmore 1936; McIntosh 1977; West and Chure 1984).
The premaxilla of Dryosaurus is edentulous ( Fig. 2.2C, D ), as is also the case in Camptosaurus ( Fig. 2.2E, F ) and most other ornithopods, and the maxillary/dentary tooth counts for CM 3392 is 14/14 (it is 13/11 for Dryosaurus lettowvorbecki and 14–15/16 for Camptosaurus ). The cheek teeth ( Figs. 2.9 ], K, 2.15, 2.16; Galton 1983b) resemble those of Hypsilophodon in having a prominent median vertical ridge on the lingual aspect of the crowns of dentary teeth, but in addition, there is also a prominent median ridge on the labial aspect of the maxillary tooth crowns ( Figs. 2.15A, G , 16A, D, F, H ). Other differences from the cheek teeth of Hypsilophodon include the lack of a cingulum, the form of the crowns—lozenge shaped for dentary and high diamond shaped for maxillary teeth, and three ridge types for the lingual surface of dentary teeth (Galton 1983b; Scheetz 1999). Remains of juvenile individuals, including jaws with teeth, were described by Galton and Jensen (1973b) from near Uravan, Colorado, and since then, eight juveniles ranging from embryo (with eggshells and teeth) to subadults have been excavated from this site (Scheetz 1991). Carpenter (1994) described the partial skeleton of a baby Dryosaurus from Dinosaur National Monument, Utah, that includes a skull, but the teeth are not exposed.
The ornithopod Dysalotosaurus lettowvorbecki Virchow 1919 is represented by thousands of bones, including partially articulated skulls ( Fig. 2.2D ), jaws with teeth ( Fig. 2.15D, E ), and postcrania from the Middle Tendaguru Saurian Bed (Upper Kimmeridgian, Upper Jurassic) in Quarry Ig close to Tendaguru Hill near Kindope, 60 km northwest of the port of Lindi, Tanzania, East Africa (Galton 1981, 1983b; Heinrich 1999; Janensch 1955). However, a restudy of the Morrison material, including the only complete skull ( Fig. 2.2C ), indicates that the Tendaguru ornithopod is referable to Dryosaurus as D. lettowvorbecki (Galton 1977, 1981, 1983b). One difference in the teeth is that the primary ridges of some of the teeth in the CM Morrison skull have finer vertical ridges that are not present on the Tendaguru teeth ( Fig. 2.16A, C–E ). However, such fine ridges are not present on the type teeth ( Figs. 2.9J, K , 2.15A, C, E, F , 2.16F ), and because teeth with and without these ridges occur in the population of Hypsilophodon foxii ( Fig. 2.14 ), this is probably an individual variation for the CM skull.
Almost the complete anatomy is known for several specimens for each of these closely related species that, as a result, provide the best evidence to date for a connection between the faunas of the Morrison of western North America and the Tendaguru of East Africa. This land connection is particularly important because, in addition to extending west-east across what was Laurasia, the northern landmass present before the formation of the Atlantic Ocean, also extends between the Northern and Southern Hemispheres across what was Gondwanaland (Galton 1977, 1980b). The land connection between western North America and Europe is also supported by the presence of the Morrison ornithopod genus Camptosaurus in the Kimmeridgian (Upper Jurassic) and Berriasian (Lower Cretaceous) of England ( Figs. 2.2E, F , 2.17 , 2.18 ; see below), as well as by other similarities in mammals and other terrestrial vertebrates at these times from Britain and Portugal (Evans 1996; Evans and Chure 1999; Pérez-Moreno et al. 1999; Prothero and Estes 1980; Rauhut 2001, 2003).
Ankylopollexia Sereno 1986
Camptosauridae Marsh 1885a
Camptosaurus dispar (Marsh 1879)
Camptosaurus Marsh 1885b is based on Camptonotus dispar Marsh 1879, the holotype of which consists of a partial skeleton with no cranial bones or teeth (YPM 1877, Reed’s Quarry 13, Como Bluff East, Wyoming). Camptosaurus is represented by several species (see Gilmore 1909b), and although the European species have been worked on recently (see below), the American species are in need of revision. The holotypes of four species of Camptosaurus (C. dispar, C. medius, C. nanus, C. browni) all came from Reed’s Quarry 13 at Comp Bluff East, and given the amount of variation (age, sexual, and individual) present in the populations of other ornithopod species from one locality, e.g. Hypsilophodon foxii (Galton 1974b, 1980b; Naish and Martill 2001) and Dryosaurus lettowvorbecki (Galton 1981, 1983b; Janensch 1955), Galton and Powell (1980) tentatively referred all the Morrison material of Camptosaurus to one species, C. dispar (Marsh 1879). The main basis for the current reconstruction of the skull of Camptosaurus (Gilmore 1909b) is a large isolated partial skull, YPM 1887 from Garden of the Gods, Colorado City, Colorado. However, the referral of this skull to C. amplus (Marsh 1879) is in error because the holotype right pes (YPM 1879, Gilmore 1909b: pl. 17; Lakes’s Quarry 1A, Como Bluff West; Ostrom and McIntosh 1966, 1999) of this species is that of the common carnivorous Morrison theropod dinosaur Allosaurus fragilis (R. T. Bakker in Galton and Powell 1980: 412; Bakker 1998). Furthermore, the skull is regarded as that of an iguanodontid by Bakker (1998), and it is described as a new taxon of Lower Cretaceous iguanodontid by Brill and Carpenter (this volume). Camptosaurus medius Marsh 1894 is the first Morrison species in which the holotype partial skeleton (YPM 1880, Reed’s Quarry 13, Como Bluff East) includes cranial material with teeth. The more accurate cranial reconstruction of Camptosaurus medius ( Fig. 2.2E ) given by Marsh (1894, 1896, 1897) is mostly based on this specimen (contra Gilmore 1909b: 204; separate Marsh reconstructions for YPM 1880 and 1887 as pencil drawings in YPM, only ink version of former published); Brill and Carpenter (this volume) give a accurate reconstruction of the skull of C. dispar that is based on several different specimens, including YPM 1880.
The teeth of Camptosaurus dispar ( Figs. 2.17A–I , 2.18A–E ), like those of later iguanodontids and hadrosaurids of the Cretaceous, differ from those of Hypsilophodon and dryosaurids in the details of the medial surface of the tooth crown of the dentary teeth ( Figs. 2.17C, I, J , 2.18C–E ; Galton and Powell 1980; Norman and Barrett 2002). Here the primary ridge is reduced, distally offset, and separated by a shallow, vertical trough from a low and broad secondary ridge. Additionally, a number of tertiary ridges are developed from the base of the marginal denticles, as also occurs incipiently in Dryosaurus ( Figs. 2.9J , 2.15A, C, E–G , 2.16A, C–E ), and the roots of dentary teeth are squared ( Fig. 2.17G–I ), rather than being subcircular in cross section (Scheetz 1999).
Camptosaurus is represented in Europe by material that includes teeth from southern England: the holotypes of C. prestwichii (Hulke 1880), a partial skull and skeleton (OUMNH J3303) from the Lower Kimmeridge Clay (Lower Kimmeridgian, Upper Jurassic) of Cumnor near Oxford, Oxfordshire ( Figs. 2.3F , 2.18F–H ; Galton 1980b, 1980c; Galton and Powell 1980), and C. hoggii (Owen 1874), a mandible with teeth (BMNH R2998) from the Upper Purbeck Beds (Berriasian, Lower Cretaceous) near Swanage, Dorset ( Figs. 2.17J , 2.18I ; Norman and Barrett 2002).
Acknowledgments. I thank the following for all their assistance over the last 35 years that I have been working intermittently on ornithischians from the Morrison Formation: N. Colbert (deceased), E. S. Gaffney and M. A. Norell (AMNH); A. J. Chang (deceased), A. W. Milner, C. A. Walker and S. Chapman (BMNH); J. A. Jensen (deceased) and R. D. Scheetz (BYU ESM); D. Berman (CM); L. M. Chiappe, K. E. Campbell and S.A. McCleod (LACM); W.-D. Heinrich, J. Helms and H. Jaeger (deceased) (MB); F A. Jenkins, Jr. and C. R. Schaff (MCZ); J. P. Powell (OUMNH); M. Brett-Surman, N. Hotton (deceased) and R. Purdy (USNM); and D. Brinkman, L. K. Murray, J. H. Ostrom, and M. A. Turner (YPM). I thank George Callison for collecting the Fruita jaws and other material while at California State University at Long Beach (now retired to Fruita), Kenneth Carpenter (DMNS) for his personal communications and photographs ( Fig. 2.3B–F ), Sandra Chapman for photographs from the BMNH ( Figs. 2.6H–K , 2.14 ), and James Kirkland (Utah Geological Survey, Salt Lake City) for an update on the stratigraphic horizon at Fruita and a photograph ( Fig. 2.3A ); the remaining photographs were taken by the author, and all photographs are reproduced courtesy of the institution housing the specimens, as indicated by the specimen numbers in the captions.
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3. A Description of a New Ornithopod from the Lytle Member of the Purgatoire Formation (Lower Cretaceous) and a Reassessment of the Skull of Camptosaurus
K ATHLEEN B RILL AND K ENNETH C ARPENTER
Abstract
In 1878, James Kerr of Colorado College found a partial skull of an orthithopod in Garden of the Gods Park, El Paso County, Colorado. It was later given to O. C. Marsh at Yale College, who identified it as Camptosaurus and used it in the reconstruction and description of Camptosaurus. Because Marsh believed the specimen came from the Morrison Formation, it was assumed to be of Jurassic age. More recent study has shown that this specimen differs from Camptosaurus in several important respects. It is much larger with a longer, heavier, and rugose snout, a wider dorsal process on the maxilla, a smaller antorbital fenestra, and a stouter quadrate with a bulbous distal articulation. Many of these features are more similar to Iguanodon , but it differs from the North American species I. lakotaensis in that the snout is less massive, the external nares are more forwardly placed, and it possesses a short palpebral that projects over the orbit. Archival data, field investigations, and petrographic analysis lead us to believe that the locality is not in the Morrison Formation, but in the lower Lytle Member of the Purgatoire Formation (Dakota Group), which is of Aptian-Albian age. It is redescribed here as a new genus and species, Theiophytalia kerri.


Figure 3.1. Map of major sites where Camptosaurus and Theiophytalia kerri have been found; 1: type locality for Camptosaurus dispar at Quarry 13; 2: Bone Cabin Quarry; 3: Dinosaur National Monument; 4: Cleveland-Lloyd Quarry; 5: type locality for Theiophytalia kerri. Camptosaurus material has also been found at other localities not shown, but consist of a few bones.
Introduction
Camptosaurus is the largest known ornithopod from the Late Jurassic of Western Europe and the western United States, attaining a length of 6.7 m (Erickson 1988). In the Morrison Formation of the western United States, Camptosaurus is surprisingly rare, with most of the specimens coming from Dinosaur National Monument and Cleveland-Lloyd Quarry in Utah, and Bone Cabin Quarry and Quarry 13 (Como Bluff) in Wyoming ( Fig. 3.1 ). The largest collection of specimens is from Quarry 13, where a minimum of 10 individuals have been found based on femora. Gilmore (1909, 1912, 1925) made the most important descriptions of Camptosaurus , with subsequent comments by Galton (1980), Galton and Powell (1980), and Norman and Weishampel (1990).
Camptosaurus dispar was originally named Camptonotus dispar in December 1879 by O. C. Marsh for a collection of bones sent to him from Como Bluffs, Wyoming (Marsh 1879). The bones had been found a few months earlier, as recounted by William Reed: “We have today found an entirely new bone yard.... There is about two acres of ground that is full of bones” (Reed, letter to Marsh, September 4, 1879; the date is not August 1879, as recounted by Reed in Gilmore 1904: 198). Marsh changed the genus name in 1885 to Camptosaurus because Camptonotus was preoccupied (Marsh 1885). Marsh continued to receive material for another eight years and named Camptosaurus medius and Camptosaurus nanus from this material (Marsh 1894b). After the Quarry 13 material was transferred to the U.S. National Museum, Gilmore (1909) named Camptosaurus browni from one of the specimens. Galton (1980) has correctly synonymized all of the species with Camptosaurus dispar. Gilmore (1925: 387, 392–393) had previously suspected that possibility for some of the species:
it will certainly permit the suggestion that perhaps after all the observed differences represent sexual characters only, and that C. medius may be the female of one of the larger species of the genus ... While for the present it may be well to retain the last mentioned species [ C. browni ], after several years reflection and with a wider knowledge of dinosaurian anatomy, I am inclined to the opinion that no good reason ever existed for its establishment.


Figure 3.2. (A, B) First skull restoration of Camptosaurus dispar by Marsh in 1894 (repeated in Marsh 1896). (C, D) Gilmore (1909)-modified view of Marsh’s skull reconstruction of Camptosaurus, basing it more on YPM 1887. (E, F) Restoration of Camptosaurus based on USNM 5473, YPM 1880 and YPM 1886, and AMNH 6120.
The first skeletal restoration of Camptosaurus dispar was presented by Marsh in 1894a (repeated in Marsh 1896) using a skull reconstructed from the skull parts of C. “medius” (YPM 1880) and a partial skull (YPM 1887) referred to Camptosaurus amplus that he received from Colorado in 1886. This reconstructed skull was shown in more detail later that year (Marsh 1894b; repeated in Marsh 1896) and is presented in Figure 3.2A, B. Gilmore (1909) modified Marsh’s skull reconstruction of Camptosaurus ( Fig. 3.2C, D ) basing it more on the referred skull of C. amplus ( Figs. 3.4 , 3.5 ). At the time, Gilmore (1909) recognized that the skull of C. amplus (YPM 1887) was of a much larger individual than that

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