THE FAUNA AND PALEOECOLOGY OF THE LATE MIOCENE MOSS ACRES RACETRACK SITE, MARION COUNTY, FLORIDA by W. DAVID LAMBERT A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1994 ACKNOWLEDGEMENTS I would like to express my deep gratitude to Dr. 3. David Webb, chairman of my committee, without whose support and guidance this dissertation would have been impossible. I would also like to thank the other members of my advisory committee. Dr. Bruce MacFadden, Dr. Ronald Wolff, Dr. Crawford Holling, and Dr. John Eisenberg, and Dr. Douglas Jones for their support and assistance during the course of this study. Gary Morgan of the Florida Museum of Natural History provided indispensable help during this study, giving invaluable advice and assistance on different topics and endeavors too numerous to list here. This study could not have been conducted without the skilled and diligent work of vertebrate fossil preparator Russell McCarty and associated volunteers like Patrick Hilton, who performed numerous miracles in converting seemingless hopeless jumbles of bone fragments into specimens capable of revealing information about the animals that first owned them. I am indebted to all those who gave their time and effort in field crews from the Florida Museum of Natural History collecting Moss Acres Racetrack specimens; without their hard work, this study could not have even been contemplated. Of particular note in this regard are Gary Morgan, Art Poyer, Russell McCarty, and Erica Siemens, whose cooperation and tolerance made my field season at Moss Acres Racetrack in the spring of 1991 a great success. I gratefully acknowledge the time and effort donated 11 by John Claytor, who operated the backhoe used to reopen the site on a voluntary basis. Great thanks are due to John Schimfessel the owner of Moss Acres who first brought the , presence of fossils at this locality to the attention of the Florida Museum of Natural History, and then graciously allowed crews from the museum to work the site over the course of years. Similarly great thanks are also due to Linda and David Markgraf, who as later owners of the Moss Acres property allowed the site to be reopened with heavy machinery and the subsequent field work to occur. Laurie Walz created all specimen illustrations presented in the chapter on the giant otter Enhvdritherium Dr. Barbara Hansen of the . University of Minnesota kindly identified the pollen in the Moss Acres Racetrack sediment sample. Dr. McCartan of the United States Geological Survey performed an invaluable mineral analysis on the Moss Acres Racetrack clays. Both the University of Michigan and the Smithsonian Institution loaned me specimens indispensible to this study. The McKenna Foundation generously provided funds both for field work and a personal salary for one semester; without its support Moss Acres Racetrack could not have been reopened in 1991, and three extraordinary Amebelodon skulls would remain below the ground undiscovered. The R. Jerry Britt, Jr. Foundation provided funding for field work via the R. Jerry Britt, Jr. Paleobiology Award. The University of Chicago Press and the American Museum of Natural History Press both generously 111 provided me with permission to include copyrighted figures in this dissertation. Lastly, I wish to express my gratitude to the Florida Museum of Natural History, which provided me with access to innumerable and invaluable facilities and personnel during the conduction of this study; without its help, this study could not have been accomplished. IV TABLE OF CONTENTS page ACKNOWLEDGEMENTS ii LIST OF COLLECTION ABBREVIATIONS viii ABSTRACT ix CHAPTERS INTRODUCTION 1 1 2 THE GEOLOGY AND AGE OF THE MOSS ACRES RACETRACK SITE 7 Geology 7 Age 24 A REDIAGNOSIS OF AMEBELODON PROBOSCIDEA, 3 ( GOMPHOTHERIIDAE) AND A NEW SUBGENUS AND SPECIES, AMEBELODON KONOBELODON BRITTI FROM THE MOSS ( ) . ACRES RACETRACK SITE 28 Systematics 29 Description 32 The Rediagnosis of Amebelodon 44 Dentinal Rods 50 Biogeography and Chronology 56 4 THE OSTEOLOGY, ECOLOGY, AND PHYLOGENY OF THE GIANT OTTER ENHYDRITHERITTM TERRAENOVAE 58 Methods 61 Osteology 62 Paleoecology and Functional Morphology 96 Phylogeny 107 5 THE OSTEOLOGY OF THE GROUND SLOTH PLIOMETANASTES (XENARTHRA, MEGALONYCHIDAE) 116 Materials and Methods 118 Systematics 119 Description 120 The Evolution of Pliometanastes in North America 155 aq^ u. 6 THE OSTEOLOGY OF PEDTOMKRYX HEMPHTT.T.KN.qT.g (ARTIODACTYLA, DROMOMERYCIDAE AND THE ) PALEOECOLOGICAL SIGNIFICAMCE OF DWARFING IN "^^'E PEDIOMERYX LINEAGE 159 Materials and Methods 161 Systematics 1S2 Description 163 The Paleobiological Significance of Body Size Trends in Pedioraervx 177 7 A POPULATION OF APHELOPS MUTIIIS (PERISSODACTYLA, RHINOCERATIDAE) FROM THE MOSS ACRES RACETRACK SITE 184 Systematics 184 Osteology 189 Population Ecology 139 Social Structure 198 Diet: and Feeding Mode 203 8 A SUMMARY OF MISCELLANEOUS NON-MAMMAL AND MAMMAL TAXA FROM THE MOSS ACRES RACETRACK SITE.. 213 Class Chondrichthyes 213 Class Osteichthyes 215 Class Amphibia 215 Class Reptilia 215 Class Aves 224 Class Mammalia 224 9 THE TAPHONOMY OF THE MOSS ACRES RACETRACK SITE.. 239 Data 240 State of Bone Preservation 242 Bone Association 248 Bone Orientation 253 Faunal Biases 256 10 THE PALEOCLIMATE AND PALEOECOLOGY OF THE MOSS ACRES RACETRACK SITE 263 Paleoclimate 263 Flora 271 Fauna 282 VI oaae 11 SUMMARY AND CONCLUSIONS 322 rOiOGV - -) . Taphonomy 323 Fauna 324 Flora 326 Climate 326 Communi-y Ecology 326 Concluding Remarks 329 APPENDIX 1 A LIST OF POST-CRANIAL ELEMENTS REFERRED TO AMEBELODON KONOBELODON) 3RITTI FROM THE MOSS ACRES ( RACETRACK SITE IN THE COLLECTION OF THE FLORIDA MUSEUM OF NATURAL HISTORY 330 APPENDIX 2 PEDIOMERYX HEMPHTLLENSIS SPECIMENS FROM THE MOSS ACRES RACETRACK SITE IN THE COLLECTION OF THE FLORIDA MUSEUM OF NATURAL HISTORY 331 APPENDIX APHELOFS MUTILIS SPECIMENS FROM THE MOSS 3 ACRES RACETRACK IN THE COLLECTION OF THE FLORIDA MUSEUM OF NATURAL HISTORY 332 APPENDIX 4 FISH, REPTILE, AND BIRD SPECIMENS FROM THE MOSS ACRES RACETRACK SITE IN THE COLLECTION OF THE FLORIDA MUSEUM OF NATURAL HISTORY 333 APPENDIX MISCELLANEOUS MAMMAL SPECIMENS FROM THE MOSS 5 ACRES RACETPJVCK SITE IN THE COLLECTION OF THE FLORIDA MUSEUM OF NATURAL HISTORY 335 APPENDIX 6 HORSE (EQUIDAE) SPECIMENS FROM THE MOSS ACRES RACETRACK SITE IN THE COLLECTION OF THE FLORIDA MUSEUM OF NATURAL HISTORY 336 APPENDIX 7 LIST OF SPECIMENS RECOVERED FROM THE MOSS ACRES RACETRACK SITE DURING THE SPRING FIELD SEASON OF 1991, INCLUDING FIELD NUMBERS, DATE MEASURED, AND A DESCRIPTION OF SPECIMENS 338 APPENDIX POSITIONAL AND ORIENTATION DATA FOR 8 SELECTED SPECIMENS COLLECTED FROM THE MOSS ACRES RACETRACK SITE DURING THE FIELD SEASON OF SPRING 1991... 340 LITERATURE CITED 3 41 BIOGRAPHIC SKETCH 55 3 LIST OF COLLECTION ABBREVIATIONS (OTHER ABBREVIATIONS EXPLAINED IN THE TEXT) D.M.N.H.: Denver Museum of Natural History, Denver, Colorado K.U.M. University of Kansas, Lawrence, Kansas : MCZ Museum of Comparative Zoology, Cambridge, Massachusetts : T.M.M.: Texas Memorial Museum, Austin, Texas UP: Florida Museum of Natural History Collection of Paleontology, Gainesville, Florida UF(M): Florida Museum of Natural History Collection of Mammalogy, Gainesville, Florida UM-V: University of Michigan Vertebrate Paleontology Collection, Ann Arbor, Michigan UNSM: Nebraska State Museum, Lincoln, Nebraska USNM(M): Smithsonian Institution Mammalogy Collection, Washington D.C. Vlll Abstract of Dissertation Presented to the Graduate School of The University of Florida in Partial Fulfillment of the Requirements of the Degree of Docor of Philosophy THE FAUNA AND PALEOECOLOGY OF THE LATE MIOCENE MOSS ACRES RACETRACK SITE, MARION COUNTY, FLORIDA By W. David Lambert April, 1994 Chairman: Dr. S. David Webb Major Department: Zoology The Moss Acres Racetrack site represents an early Hemphillian age, clay-filled sinkhole in western Marion County, Florida, with a diverse biota, possibly containing more evidence for local biotic and climatic conditions than any other late Miocene locality on the Gulf Coastal Plain. The geology, taphonomy, fauna, palynoflora, and community ecology of this locality were all examined in this study. Geological and taphonomic evidence suggests that the fossil biota was preserved under strictly nonfluvial conditions in an isolated pond or lake, indicating that this assemblage represents a real community rather than a mixed- assemblage. The faunal description included detailed study of the following mammalian taxa: the gomphothere proboscidean Amebelodon Konobelodon britti (described as a new subgenus ( ) and species), the ground sloth Pliometanastes (represented by previously unknown limb elements), the giant otter Enhvdritherium (represented by a partial skeleton, the best bunodont otter specimen known) and the dromomerycid ruminant , Pediomervx hemohi llensis (including a partial skull with ix ly intact horn cores), and the rhinoceros Aoheloos ilis Other mammal taxa (including the horses) were mined in a cursory fashion only. Preliminary evidence gests the presence of a new species of the emydid turtle udemvs and a new species of Alligator within the Le petofauna. The palynoflora revealed a dominance by grass Y. oak suggesting a savanna landscape, with all other taxa : (map iividually forming minute portions of the flora. The floral n ;t resembles that of a modern warm temperate woodland in in southeastern United States, suggesting temperatures - re •dlar to those found in the region today. Rainfall patterns inconclusive, though the presence of a savanna landscape 5 y to jgests strong seasonal aridity. nd The nature of community interactions within the biota n its largely inconclusive. Terrestrial carnivores were 3 rtually absent, possibly a result of small sample size, until -dence for facilitative grazing like that found in modern ugh rican savannas was searched for, with the final results mg ambiguous. Amebelodon was shown to be a plausible ological analog for modern African elephants in savannas, earing woodlands to limit their spread into the grasslands Lng i thus encouraging and maintaining biotic diversity. of • i