Hyaenodontidae (Creodonta, Mammalia) and the Position of Systematics in Evolutionary Biology by Paul David Polly B.A. (University of Texas at Austin) 1987 A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Paleontology in the GRADUATE DIVISION of the UNIVERSITY of CALIFORNIA at BERKELEY Committee in charge: Professor William A. Clemens, Chair Professor Kevin Padian Professor James L. Patton Professor F. Clark Howell 1993 Hyaenodontidae (Creodonta, Mammalia) and the Position of Systematics in Evolutionary Biology © 1993 by Paul David Polly To P. Reid Hamilton, in memory. iii TABLE OF CONTENTS Introduction ix Acknowledgments xi Chapter One--Revolution and Evolution in Taxonomy: Mammalian Classification Before and After Darwin 1 Introduction 2 The Beginning of Modern Taxonomy: Linnaeus and his Predecessors 5 Cuvier's Classification 10 Owen's Classification 18 Post-Darwinian Taxonomy: Revolution and Evolution in Classification 24 Kovalevskii's Classification 25 Huxley's Classification 28 Cope's Classification 33 Early 20th Century Taxonomy 42 Simpson and the Evolutionary Synthesis 46 A Box Model of Classification 48 The Content of Simpson's 1945 Classification 50 Conclusion 52 Acknowledgments 56 Bibliography 56 Figures 69 Chapter Two: Hyaenodontidae (Creodonta, Mammalia) from the Early Eocene Four Mile Fauna and Their Biostratigraphic Implications 78 Abstract 79 Introduction 79 Materials and Methods 80 iv Systematic Paleontology 80 The Four Mile Fauna and Wasatchian Biostratigraphic Zonation 84 Conclusion 86 Acknowledgments 86 Bibliography 86 Figures 87 Chapter Three: A New Genus Eurotherium (Creodonta, Mammalia) in Reference to Taxonomic Problems with Some Eocene Hyaenodontids from Eurasia (With B. Lange-Badré) 89 Résumé 90 Abstract 90 Version française abrégéé 90 Introduction 93 Acknowledgments 96 Bibliography 96 Table 3.1: Original and Current Usages of Genera and Species 99 Table 3.2: Species Currently Included in Genera Discussed in Text 101 Chapter Four: The skeleton of Gazinocyon vulpeculus n. gen. and comb. (Hyaenodontidae, Creodonta) and polyphyly of the Hyaenodontinae 102 Abstract 103 Introduction 103 Materials and Methods 104 Abbreviations 106 Systematic Paleontology 106 Description of new material 108 Skull and Dentition 108 v Axial Skeleton 112 Forelimb 113 Hindlimb 116 The Phylogenetic Position of Gazinocyon 121 Methods and Materials 125 Results 126 Discussion 131 Pterodontinae new subfamily 133 Hyaenodontinae Trouessart, 1885: revised description 135 Conclusion 136 Acknowledgments 138 Bibliography 139 Table 4.1: Measurements of the dentition of Gazinocyon vulpeculus 146 Table 4.2: List of species used in the determination of generic character states 148 Appendix 4.1: Characters Used in the phylogenetic analysis 151 Appendix 4.2: Data matrix 155 Figures 156 Chapter Five: The Basicranial Morphology of Hyaenodontidae (Creodonta, Mammalia) and its Phylogenetic Implications 166 Introduction 167 Abbreviations 169 Material and Methods 169 Development and General Morphology of the Basicranium 170 The Basicranium of Hyaenodon 171 The Basicranium of Tritemnodon 179 Morphological Variation in Hyaenodontid Ear Regions 182 vi Phylogenetic Analysis of Hyaenodontid Basicranial Characters 188 Conclusions 190 Acknowledgments 191 Bibliography 192 Table 5.1. Hyaenodontid species with preserved basicranial regions 199 Table 5.2: List of Basicranial Characters used in the phylogenetic analysis 201 Table 5.3: Data matrix used in the phylogenetic analysis 202 Figures 203 Chapter Six: Afterword: Some speculations on mammalian molar evolution in relation to development 212 Introduction 213 Sizing up the Situation 217 Mammalian Molar Crown Morphogenesis 219 Methods of Controlling Molar Morphogenesis 222 Complexity in Mammalian Molar Crown Patterns 226 Function and its Constraint in Mammalian Molar Evolution 230 An Example from Creodonta: The Evolution of Apterodon 231 Two Scenarios for Molar Evolution 242 Testing the Hypothesis 243 Conclusion 245 Acknowledgments 246 Bibliography 246 Figures 256 Appendix: Currently Recognized Species of Creodonta 268 Proviverrinae 269 Koholiinae 274 Hyaenodontinae 274 vii Pterodontinae 277 Other Hyaenodontine-like Creodonts 279 Limnocyoninae 280 Machaeroidinae 280 Oxyaeninae 281 Ambloctoninae 282 viii INTRODUCTION Systematics is a wide ranging field. It includes the naming of species, genera, and other taxonomic groups, the identification and interpretation of organisms and their remains, and analyses of the evolutionary relationships among groups. In all of these roles it touches many sub-disciplines of biology and geology. This dissertation is an exploration of all of these aspects of systematics. It is arranged as six separate papers, each of which deals with a different aspect. All of the papers are in some way connected with the systematics of the extinct Eutherian group Creodonta. The dissertation includes specific work on alpha-level systematics, legalistic nomenclature, phylogenetic systematics, and the history and philosophy of constructing classifications from an evolutionary or other "natural" framework. It also expands beyond the limits of pure systematics into other realms that systematics is only the necessary base upon which other work is based. These include biostratigraphy, functional morphology, and evolutionary theory. All of these aspects of systematics are explored through work on hyaenodontid creodonts. Creodonta is an extinct group of eutherian mammals. As currently delimited, the first creodonts appeared in the mid to late Paleocene and the last died in the latest Miocene. They lived in North America, Asia, Europe, and Africa and played the role of the dominant carnivore in terrestrial ecosystems on the continents for the first half of the Tertiary. They are a very diverse group with more than 200 species currently recognized (Appendix I). Unfortunately, they are very poorly studied. They were originally recognized as a distinct group by Edward Drinker Cope in 1874, and were studied intensively by him in the late 19th century and by W.D. Matthew in the early 20th. After Matthew, though, they have been given little treatment as phylogenetic interest shifted to earlier Mesozoic mammals. Creodonts are morphologically very primitive for eutherian ix mammals. They retain many primitive features of the dentition and skull of the earliest placentals. For this reason, they may prove very useful in solving the puzzle of deep branching within Eutheria. Before that, though, more must be known about variation and relationships within Creodonta. This dissertation goes a long way toward that end. The first chapter of the dissertation forms a backdrop for the successive chapters. It is an exploration of the historical relationship between classification and natural order. It concentrates on mammalian and creodont classification. The purpose of the second chapter is to update the identifications of the hyaenodontids from the Eocene Four Mile Fauna and to describe and illustrate material that is used in later chapters. The third chapter straightens out some confusion over the nomenclature of several Eocene Eurasian genera of hyaenodontids that are included in the phylogenetic analysis of the fourth chapter. The fourth chapter has the dual purpose of describing previously undescribed hyaenodontid postcranial material and using that information to form the basis of a phylogenetic analysis of the Hyaenodontidae. The fifth chapter is similar to the fourth, but deals with basicranial morphology of hyaenodontids. The final chapter is a synthesis of ideas from paleontology, systematics, embryology, and evolutionary theory to explain the multiple evolution of quadritubercular molars in mammalian history. Together these chapters represent many of the various manifestations of systematics mentioned above. x ACKNOWLEDGMENTS I would first like to thank my committee for reading and commenting on this dissertation. They spent many hours and their work improved it dramatically. I would also like to thank them for the many letters they have written for me and for being very supportive and easy to work with. I would like to thank Dr. C.B. Wood for first teaching me about mammalian molar function. I would like to thank Dr. Brigitte Lange-Badré for guidance in working with creodonts. Dr. Elmar Heizmann was kind enough to sponsor me for a Deutscher Akademischer Austauschdienst scholarship and as extremely helpful and hospitable to me during my stay in Germany. Dr. David Lindberg has also been very helpful and has provided many interesting discussions about much of the work presented in this dissertation. The late Dr. Allan Wilson inspired me to think about evolution and morphology in a new way. Dr. Tim Rowe has continually maintained an interest in my career and he and Dr. Chad Oliver receive credit for sparking my interest in this field. Wendy Olson, Michelle Koo, Francis Villablanca, Maria Orive, John Wakely, Jessica Theodor, Dan Garcia, Nancy Simmons, Anne Weil, Chris Bell, Mike Russell, Ken Warheit, Luo, Bob Dundas, and Chris Meyer have all been both helpful as fellow graduate students and made life more interesting. I would also like to especially thank Tina Rouse, Marlene Martinez, and Gayle Nelms for their love and support as founding members of the Dave Polly Fan Club. I would like to thank Jessica Theodor, editor of PaleoBios, and Brigitte Lange- Badré, my co-author on Chapter Three, for their permission to include the previously published and