I I * . ..' w~~~~l~~~WASATC~IAN v I . ' I-# MAMMALIAN FAUNA FRCI.1 T~LEOCENE ,%* ' - -*.*aze . ,,:$%?"- ?A -- OF NORTHWESTERN WYO~~~B'S: COMPOSITION AND OY!ERSITY IN A I mtnm- --LYtm SI;L-'LED HIGH-FL00-lj-,, r--R" --- PAPERS ON PALEONTOLOGY-RECENT NUMBERS 18. Ostracods of the Middle Devonian Silica Formation (Volumes I and 11) by Robert V. Kesling and Ruth B. Chilman 19. Late Pleistocene Cold-blooded Vertebrate Faunas from the Mid-Continental United States. I. Reptilia: Testudines, Crocodilia. by Robert E. Preston 20. The Maple Block Knoll Reef in the Bush Bay Dolostone (Silurian, Engadine Group), Northern Peninsula of Michigan by Allan M. Johnson, Robert V. Kesling, Richard T. Lilienthal, and Harry 0. Sorensen 21. A Synopsis of Fossil Grasshopper Mice, Genus Onychomys, and their Relationships to Recent Species by Michael D. Carleton and Ralph E. Eshelman 22. Systematics of the Fissiculate Blastoidea by D. Bradford Macur& 23. Epizoans on the Brachiopod Paraspirijer bownockeri (Stewart) from the Middle Devonian of Ohio by Diana K. Sparks, Richard D. Hoare, and Robert V. Kesling 24. Early Cenozoic Paleontology and Stratigraphy of the Bighorn Basin, Wyoming by Philip D. Gingerich (ed.) and others 25. Dimorphic Middle Devonian Paleocopan Ostracoda of the Great Lakes Region by Robert V. Kesling and Ruth B. Chilman 26. The Clarkforkian Land-Mammal Age and Mammalian Faunal Composition across the Paleocene-Eocene Boundary by Kenneth D. Rose 27. Evolutionary History of Microsyopoidea (Mammalia, ?Primates) and the Relationship between Plesiadapiformes and Primates by Gregg F. Gunnel1 28. New Earliest Wasatchian Mammalian Fauna from the Eocene of Northwestern Wyoming: Composition and Diversity in a Rarely Sampled High-Floodplain Assemblage by Philip D. Gingerich Museum of Paleontology The University of Michigan Ann Arbor, Michigan 48 109 NEW EARLIEST WASATCHIAN MAMMALIAN FAUNA FROM THE EOCENE OF NORTHWESTERN WYOMING: COMPOSITION AND DIVERSITY IN A RARELY SAMPLED HIGH-FLOODPLAIN ASSEMBLAGE Frontispiece: Aerial photograph of badlands at the south end of Polecat Bench. Red beds in the right half of the photograph are University of Michigan locality SC-67, yielding most specimens described here. Locality SC-308 is in red beds in the left center of the photograph, and locality SC-121 is in red beds at the left margin of the photograph. Clarks Fork Basin and Beartooth Mountains lie in the left distance. NEW EARLIEST WASATCHIAN MAMMALIAN FAUNA FROM THE EOCENE OF NORTHWESTERN WYOMING: COMPOSITION AND DIVERSITY IN A RARELY SftltlWLw t-ttwt=i=LOODPLAN ASSEMBLAGE PHILIPD. GINGERICH Museum of Paleontology The University of Michigan Ann Arbor, Michigan 48109-1079 UNIVERSITY OF MICHIGAN PAPERS ON PALEONTOLOGY NO. 28 Papers on Paleontology No. 28 Museum of Paleontology The University of Michigan Ann Arbor, Michigan 48 109 Philip D. Gingerich, Director Dedicated to the Memory of PROFESSOR JOHN A. DORR, JR. 1922 - 1986 Jack's interest was an important stimulus in much of this work. Published November 30, 1989 TABLE OF CONTENTS Frontispiece .................................... ii Carnivora ............................37 ... Rodentia ............................ 40 Titlepage .....................................111 Condylarthra .........................40 Artiodactyla .......................... 56 Table of Contents ................................v Perissodactyla ........................58 Edentata ............................. 63 List of Figures .................................. vi Incertae sedis .........................64 .................................. List of Tables vii IV . Composition and diversity .................. 67 Faunal composition at the family level ....... 67 Abstract ....................................... ix Principal components analysis ...........68 Change through time ...................69 I . Introduction............................... 1 Clarkforkian and early Wasatchian land- Species diversity ........................ 69 mammal ages .......................... 2 Rank abundance of species ................70 Clarkforkian land-mammal age ............ 2 Change through time ...................72 Wasatchian land-mammal age ............ 3 Clarkforkian-Wasatchian boundary V . Paleoenvironmental interpretation ........... 75 sandstone .......................... 3 Sedimentology and paleosol development .....75 Discovery of earliest Wasatchian fauna and Sheet sandstone and mature paleosols .....75 localities ............................. 3 Basin model .......................... 75 Systematic protocol ....................... 4 Flora and fauna ......................... 77 Institutional abbreviations ..................5 Plants, invertebrates. fish. and reptiles ..... 77 Acknowledgments ........................ 5 Trends in the relative abundance of mammals .......................... 77 11 . Lithology and localities ...................... 7 High and low floodplain faunas ..........78 List of localities ........................ 7 Small species with large Clarkforkian or Wasatchian congeners ...............79 111 . Systematic paleontology .................... 15 Plantae ................................ 15 Cenogram of mammalian body size .........79 Dicotyledoneae ....................... 15 Mollusca ............................... 15 VI . Correlation with Europe and Asia ........... 83 Prosobranchia ........................ 15 Paleocene-Eocene boundary ............... 83 Pulmonata ........................... 18 Faunal similarity ........................ 83 Osteichthyes ............................ 19 Faunal succession in Europe ............... 84 Lepisosteiformes ......................19 Comparison of earliest Wasatchian species ....84 Amiifonnes ..........................19 New evidence on correlation of the Reptilia ................................20 Clarkforkian .........................85 ............................ Chelonia 20 Paleomagnetic stratigraphy ................86 Squamata ............................ 20 Crocodylia ...........................21 Aves .................................. 22 W . Origin of Artiodactyla. Hyaenodontidae. Mammalia .............................22 Perissodactyla. and Primates ................89 Multituberculata ...................... 22 Climate and geography ...................89 Marsupialia ..........................22 High floodplain and low floodplain Proprimates .......................... 23 environments .........................90 Primates ............................. 23 Tillodontia ...........................24 VIII .Conclusions ..............................91 Pantodonta ...........................29 Taeniodonta .......................... 30 Literature cited .................................93 Creodonts ........................... 31 LIST OF FIGURES 1. Map of earliest Wasatchian localities .............8 28 . Stratigraphic distribution of Clarkforkian and early 2 . Clarkforkian-Wasatchianboundary sandstone ......9 Wasatchian Chriacus ........................46 3 . Sourthwesterly dipping surface of boundary 29 . Dentition of Princetonia yalensis, new genus and sandstone ................................... 9 species .................................... 47 4 . Earliest Wasatchian locality SC-67 ............. 11 30 . Dentition of Hyopsodus loomisi ................ 48 5 . Principal collecting interval of locality SC-67 ..... 12 31 . Dentition of Ectocion parvus ..................50 6 . Stratigraphic section at locality SC-67 ........... 13 32 . Tooth size in Ectocionparvus, Ectocion 7 . Earliest Wasatchian locality SC-121............. 14 osbornianus, and Copecion davisi .............. 52 8 . Sizes of stony endocarps of Celtis phenacodorum . 18 33 . Stratigraphic distribution of Clarkforkian and early 9 . Freshwater and terrestrial mollusks ............. 18 Wasatchian Ectocion ......................... 53 10. Reconstructed plastron of Echmatemys .......... 20 34 . Dentary of Phenacodus cf . P . intermedius ........54 11. Tooth of xiphodont crocodilian Pristichampsus ....22 35 . Dentition of Copecion davisi, new genus and 12. Premolar of Ectypodus tardus .................. 22 species .................................... 55 13. Lower dentition of Cantius torresi .............. 24 36 . Dentition of Diacodexis ilicis, new species ....... 57 14. Stratigraphic distribution of early Wasatchian 37 . Stratigraphic distribution of early Wasatchian Cantius ................................... 25 Diacodexis ................................. 58 15. Lower dentition of Azygonyx gunnelli, new genus 38 . Dentition of Hyracotherium sandrae, new species . 59 and species ................................ 26 39 . Lophodonty in North American Hyracotherium 16. Postcranial remains of Azygonyx gunnelli ........ 28 sandrae and European Cymbalophus cuniculus .... 60 17. Stratigraphic distribution of early Wasatchian 40 . Skeleton of Hyracotherium sandrae ............. 61 Esthonychidae .............................. 29 41 . Stratigraphic distribution of early Wasatchian 18. Comparison of size, hypsodonty , and stylinodonty Hyracotherium ............................. 61 in Ectoganus ............................... 30 42 . Humerus of Palaeanodon nievelti, new species ....64 19. Dentition and tarsus of Dipsalidictis platypus ..... 3 1 43 . Stratigraphic distribution of Clarkforkian and 20 . Dentition of Arjia junnei, new species ........... 35 Wasatchian Palaeanodonta .................... 65 21 . Stratigraphic distribution of early Wasatchian 44 . Dentary of cf . Asiabradypus sp ................ 65 Afla .....................................