UNIVERSITY OF OKLAHOMA GRADUATE COLLEGE THE EVOLUTION OF EARLY TRIBOSPHENIC MAMMALS A DISSERTATION SUBMITTED TO THE GRADUATE FACULTY in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY By BRIAN MICHAEL DAVIS Norman, Oklahoma 2011 THE EVOLUTION OF EARLY TRIBOSPHENIC MAMMALS A DISSERTATION APPROVED FOR THE DEPARTMENT OF ZOOLOGY BY ______________________________ Dr. Richard Cifelli, Chair ______________________________ Dr. Laurie Vitt ______________________________ Dr. Nicholas Czaplewski ______________________________ Dr. Cynthia Gordon ______________________________ Dr. Stephen Westrop ______________________________ Dr. Richard Lupia © Copyright by BRIAN MICHAEL DAVIS 2011 All Rights Reserved. ACKNOWLEDGEMENTS I am deeply indebted to Dr. Richard Cifelli for his mentoring and friendship over the course of the past decade. I came to him with a year of college under my belt, and Rich immediately set me on a course to academic independence. His scholarship and immeasurable wit have been inspirations throughout my academic career. Also of special note is Dr. Cynthia Gordon, whom I have known for just as long. Cindy provided me with early guidance and, most importantly, teaching experience. She has been a model for that very important side of academia; for that, and for her friendship, I am grateful. I would also like to thank Dr. Nicholas Czaplewski for his accessibility and willingness to drop everything to discuss anything. Dr. Stephen Westrop has been highly instrumental in my understanding of phylogenetics and interpreting character evolution. Drs. Richard Lupia and Laurie Vitt have served as valued committee members, as well. My work could not have been possible without help and mentoring by the staff of the Department of Vertebrate Paleontology at the Sam Noble Oklahoma Museum of Natural History. Kyle Davies has taught me nearly everything I know about preparation techniques and lower vertebrate anatomy. Jeff Person and Jennifer Larsen have made specimen access and curation in the collections easier than could be imagined. Roger Burkhalter (Department of Invertebrate Paleontology) has also been invaluable; he has been willing to drop everything to help with specimen imaging and other requests. I would also like to thank the current and former graduate students and undergraduates I have had the pleasure of sharing this experience with. In particular, Dr. Brooke Haiar, Sarah Werning, Sally Pine, Dr. Jennifer Hargrave, Charles Baker, Andrew iv Thomas, Mandy McCoy, Kim Ferguson, and Cara McConnell have been helpful in both academic and social contexts. I would also like to single out Dr. Matt Dugas for his help in getting me to think in a broader biological context. I have been fortunate to receive funding from a number of sources throughout my graduate career, most notably from the departments of Zoology and Vertebrate Paleontology, and the Graduate Student Senate. I have also benefited from funding from the College of Arts and Sciences, the Graduate College (through a Robberson Grant), and the Geological Society of America (Stephen J. Gould Grant). SEM work at the OMNH was made possible through a National Science Foundation grant, NSF DBI-010156. Of special mention is Dr. William Matthews, chair of the Department of Zoology, for his patience in providing me access to extended support through teaching assistantships. Above all, I would like to thank my wife Erin. She has been consistently the most patient and encouraging influence in my life, and I could not have reached the finish line without her. v TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................... iv LIST OF TABLES ............................................................................................................. ix LIST OF ILLUSTRATIONS .............................................................................................. x ABSTRACT ...................................................................................................................... xii PREFACE ........................................................................................................................... 1 INTRODUCTION .............................................................................................................. 2 CHAPTER 1—A NOVEL INTERPRETATION OF THE TRIBOSPHENIDAN MAMMAL SLAUGHTERIA ERUPTENS FROM THE LOWER CRETACEOUS TRINITY GROUP, AND IMPLICATIONS FOR DENTAL FORMULA IN EARLY MAMMALS....................................................................................................................... 6 ABSTRACT .................................................................................................................... 7 INTRODUCTION .......................................................................................................... 7 SYSTEMATIC PALEONTOLOGY ............................................................................ 11 Slaughteria eruptens Butler, 1978 ............................................................................ 11 DISCUSSION ............................................................................................................... 18 Identification of tooth loci in Slaughteria ................................................................. 18 Implications for dental formula and tooth replacement in basal Tribosphenida ...... 21 CONCLUSIONS........................................................................................................... 25 ACKNOWLEDGMENTS ............................................................................................ 26 LITERATURE CITED ................................................................................................. 26 FIGURE CAPTIONS.................................................................................................... 32 CHAPTER 2—EVOLUTION OF THE TRIBOSPHENIC MOLAR PATTERN IN EARLY MAMMALS, WITH COMMENTS ON THE“DUAL-ORIGIN” HYPOTHESIS................................................................................................................. 37 ABSTRACT .................................................................................................................. 38 INTRODUCTION ........................................................................................................ 38 MORPHOLOGICAL BACKGROUND ....................................................................... 41 KUEHNEOTHERIUM AS STRUCTURALLY ANCESTRAL ................................... 46 ELONGATION OF THE TALONID: THE AMPHITHERIIDAE .............................. 47 THE “PERAMURAN” STAGE ................................................................................... 50 EARLY TRIBOSPHENIDANS: THE AEGIALODONTID STAGE ......................... 53 THE “DUAL-ORIGIN” OF TRIBOSPHENIC MAMMALS ...................................... 57 The Australosphenida ............................................................................................... 60 CONCLUSIONS........................................................................................................... 68 ACKNOWLEDGMENTS ............................................................................................ 70 LITERATURE CITED ................................................................................................. 71 FIGURE CAPTIONS.................................................................................................... 80 vi CHAPTER 3—REAPPRAISAL OF THE TRIBOSPHENIDAN MAMMALS FROM THE TRINITY GROUP (APTIAN-ALBIAN) OF TEXAS AND OKLAHOMA .................................................................................................................. 94 ABSTRACT .................................................................................................................. 94 INTRODUCTION ........................................................................................................ 95 MATERIALS ................................................................................................................ 98 SYSTEMATIC PALEONTOLOGY ............................................................................ 98 Atokatheridium boreni .............................................................................................. 99 Oklatheridium szalayi ............................................................................................. 102 Oklatheridium minax .............................................................................................. 104 Oklatheridium sp. .................................................................................................... 106 Pappotherium pattersoni ........................................................................................ 109 Holoclemensia texana ............................................................................................. 113 Holoclemensia sp. ................................................................................................... 119 Kermackia texana ................................................................................................... 119 Slaughteria eruptens ............................................................................................... 124 Gen. et sp. indet. ..................................................................................................... 126 DISCUSSION ............................................................................................................. 128 Holoclemensia as a eutherian