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Toxodontia of Salla, Bolivia (Late Oligocene) : Taxonomy, Systematics

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Toxodontia of Salla, Bolivia (Late Oligocene) : Taxonomy, Systematics TOXODONTIA OF SALLA, BOLIVIA (LATE TAXONOMY, OLIGOTFMFV SYSTEMATICS, AND FUNCTIONAL MORPHOLOGY By BRUCE J. SHOCKEY A DISSERTATION PRESENTED TO THE GRADUATF «;rFrr>r»T " OP plorida in LRmL OF THE tolSent REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1997 Copyright 1997 by Bruce J. Shockey ACKNOWLEDGEMENTS This project has received generous help from many individuals and several institutions for which I am exceedingly grateful. This support has come in several forms, including financial, intellectual, and moral. Financial support for the fieldwork at Salla the past few years has come by way of National Science Foundation grants to my major professor, Bruce J. MacFadden. Some exploratory fieldwork was financed by the Society of Vertebrate Paleontology by way of the Brian Patterson Memorial Award. I am grateful to Gary Morgan and Roger Portell for their expertise and company during my first field season at Salla. Museum studies were facilitated by several institutions that I had the pleasure of visiting. Rosendo Pascual and Marcelo Reguelo of the Museo de La Plata helped my visits to their institution be both productive and enjoyable. Jose Bonaparte and Adrian Ramos kindly facilitated the privilege of studying in the Ameghino Collection of the Museo Argentino de Ciencias Naturales "Bernardino Rivadavia," Buenos Aires. The American Museum of Natural History provided financial support via their Collections Study Grant. This work at the AMNH was also facilitated by Richard Tedford, Danny Bryant, and Mark Norrell. The Field Museum of Natural History provided support for my studies at their institution through the Dee Fund and the personal assistance of John Flynn, Bill Simpson, and Mark Alvery. iii My work in the Florida Museum of Natural History was supported by Dr. MacFadden and the staff of the Vertebrate Paleontology section. Russell McCarty, director of the prep lab, prepared many of the specimens that were described in this work. He was assisted by David Bunger, who prepared the notohippid skeleton. Many kindnesses were extended to me by my committee members which I appreciate, especially the informal discussions. In addition to serving on my committee, John Anderson and Ron Wolff supervised me when I served as a laboratory instructor for courses which they taught. Dr. MacFadden generously provided significant material, and moral support. Laurie Walz produced many of the figures in the first three chapters and served as a graphics advisor for figures that I produced in the later chapters. Ms. Walz also honored me by being a dear friend. Rebekkah McClean produced Figures 3.1 and 3.2 and Richard Cifelli provided a copy of Bryan Patterson's catalog of notohippids in the Ameghino Collection. Federico Anaya Daza helped in many ways. He provided leadership, labor, and camaraderie in the field and the lab. He facilitated the study of specimens under his care at the Museo Nacional de Historia Natural in La Paz, Bolivia and has generously lent many to our institution so that I could study these at leisure. My gratitude to these individuals and institutions is magnified by my surprise that such generosity was so common. IV 1 TABLE OF CONTENTS 2 ACKNOWLEDGEMENTS iii ABSTRACT viii 3 INTRODUCTION Overview History of South American Paleomammalogy 5 Exploration of Salla 18 Geography and Geology of Salla 23 MATERIALS, METHODS, AND DEFINITIONS 39 Materials 39 Dental Measures and Terminology 40 Statistics 51 Phylogenetic Analysis Locality Coordinates SYSTEMATIC PALEONTOLOGY 54 Order Notoungulata Roth, 1903 54 Suborder Toxodontia Owen, 1853 55 Family Leontiniidae Ameghino, 1895 56 Unnamed Leontiniid Genus 61 Small Leontiniid in Unnamed Genus (Species A) 62 Large Leontiniid (Species B) 69 Family Notohippidae Ameghino, 1894 77 Unnamed Notohippid Genus 80 Unnamed Notohippid Species 80 Eurygenium Ameghino, 1895 !11"1...'"86 Eurygenium sp. nov g7 Id^ynchippus sp., cf. R. brasiliensis Soria and Alvarenga, 1989 101 Family Toxodontidae Owen, 1845 ...............Z1O6 cf. Proadinotherium sp 1Q7 V 4 ONTOGENY OF TWO NOTOUNGULATES OF SALLA 113 Introduction 113 Juvenile Notungulates of Salla 117 Ontogeny and Evolution 134 Chapter Summery 135 5 FUNCTIONAL MORPHOLOGY AND FEEDING ECOLOGY 137 Introduction 137 Methods 144 Results 153 Discussion 167 Reconstruction of Diets of Toxodontia 175 Chapter Summery 182 5 COMPARATIVE AND FUNCTIONAL SKELETAL ANATOMY OF SOME MEDIUM-SIZED UNGULATES OF SALLA 184 Introduction 184 Materials and Methods 185 Comparative Postcranial Anatomy of Ungulates of Salla 188 Functional Significance 220 Chapter Summery 228 7 SYSTEMATICS OF ADVANCED TOXODONTIA 229 Introduction 229 Methods 231 Results and Discussion 238 Chapter Summery 242 8 FAUNA OF SALLA 244 9 SUMMARY 255 Summary of Past UF Work at Salla 255 Summary of Present Findings 256 VI APPENDICES A UNCATALOGED SPECIMENS OF MNHN-BOL 259 B PERISSODACTYL MORPHOMETRICS 260 C MASSES OF UNGULATES 261 LIST OF REFERENCES 262 BIOGRAPHICAL SKETCH 277 vii Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy TOXODONTIA OF SALLA, BOLIVIA (LATE OLIGOCENE): TAXONOMY, SYSTEMATICS, AND EUNCTIONAL MORPHOLOGY By Bruce J. Shockey August 1997 Chairman: Bruce J. MacFadden Major Department: Zoology The Salla Beds of Bolivia preserve a diverse sample of mammals that lived during the "Splendid Isolation" of South America. The fossil-bearing beds of Salla are known to be late Oligocene (ranging from about 27 to 24 million years ago), a time when the endemic mammals evolved advanced characters, such as high-crowned teeth and specialized locomotor adaptations, and when primates first appeared and rodents first diversified in South America. Though this fauna has received much attention in the literature, the most common order at Salla, Notoungulata, has been largely neglected. This work provides the first description of Toxodontia notoungulates from Salla, as well as a study of their ontogenetic development, functional anatomy, and phytogeny. The results of the alpha taxonomy indicate that the Toxodontia of Salla are different species from those of the classical Patagonian Deseadan localities. This difference is judged to be a result of the geographic differences rather than temporal ones since the lower (older) regions of Salla are contemporaneous with the younger Patagonian Deseadan localities. Most of Vlll the Toxodontia of Salla represent new species. Two, however, are known from other low-latitude Deseadan localities, but not from the high-latitude localities of Patagonia (Eurvgenium sp. is known from the Pataca Formation of Southern Bolivia and the Tremembre Formation of Brasil is the type locality for Rhychippus brasiliensis) . Four new species are described (two notohippids and two leontiniids) and a novel method of determining feeding ecology of extinct herbivores by use of a multivariate analysis of morphological features associated with feeding in extant ungulates is employed. Other discoveries in this work include the first descriptions of a notohippid skeleton, of the deciduous teeth of a notohippid and a mesotheriid, and the first description of the postcranial elements of the macraucheniid ? Coniopternium primitivum . This litoptern is shown to have the oldest "knee-lock" known, similar in principle to, but distinct from, that seen in horses. The Salla Beds provide a snapshot of life in Bolivia during the initiation of the building of the Andes. This fauna is shown to be more diverse, both in terms of species richness and morphological adaptations, than previously known. IX CHAPTER 1 INTRODUCTION Overview The Salla Beds are a late Oligocene mammal-bearing unit located in the Eastern Cordillera of the Andes of Bolivia (Hoffstetter, 1968; MacFadden et al. 1985). These beds lie in a mountane basin adjacent to the Aymaran village of Salla (pronounced "sal-ya" by its residents). It is universally accepted as being of the Deseadan South American Land Mammal Age (SALMA) and is generally considered to be late Oligocene (MacFadden et al., 1985; Kay et al., 1995; Flynn and Swisher, 1995), though some workers (Sempere et al., 1990; McRae, 1990) interpret its age as early Miocene. Salla had a diverse mammalian fauna and a number of works have been published regarding most of the orders of mammals present. Mammalian orders previously studied include the marsupials (Patterson and Marshall, 1978; Villarroel and Marshall, 1982; Hoffstetter and Petter, 1983; Wolff, 1984a), rodents (Hoffstetter and Lavocat, 1970; Lavocat, 1976; Patterson and Wood, 1982), primates (Hoffstetter, 1969; Wolff, 1984b; Rosenberger et al., 1991), litopterns (Cifelli and Soria, 1983a and 1983b) and the pyrothere (MacFadden and Frailey, 1984). The most common order of mammals at Salla, the Notoungulata, however, has been generally neglected in the literature. The only two works regarding Salla notoungulates are a description of the skeleton of Trachytherus speeazziniamis in an unpublished 1 2 masters thesis (Sydow, 1988) and an abstract regarding the skeleton of a notohippid referred to Eurygenium (Shockey, 1995). This study describes and discusses notoungulates of the suborder Toxodontia Owen 1853 in terms of their phylogeny, functional morphology, and ecology. It relies heavily upon the excellent collection of fossil mammals that have been acquired during UF-Bolivian expeditions to Salla which began in 1981. Currently, other investigators are studying the notoungulates from Salla. Ralph Hitz
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