A Review of the Fossil Record of North American Turtles of the Clade Pan-Testudinoidea

Turtles of the clade Pan-Testudinoidea have a rich fossil record in North America, including the Caribbean, ranging from the late Paleocene to the Holocene. All earlier reports cannot be substantiated herein. The earliest members of this clade probably immigrated in multiple waves from Asia. Current phylogenies of crown Testudinoidea recognize four primary clades: Pan-Emydidae, Pan-Geoemydidae, Pan-Testudinidae, and the lineage leading to Platysternon megacephalum. An updated global phylogeny allows attribution of fossils to these lineages with confidence that allows the discernment of new diversity trends and biogeographic patterns. The diversity of North American Pan-Testudinidae increased consistently throughout the Cenozoic and reached its peak in the early Miocene. The extinction of many testudinids at the end of the Pleistocene, however, decreased tortoise diversity toward its extant levels. The diversity of North American Pan-Emydidae and Pan-Geoemydidae shows opposite patterns. Pan-Emydidae are remarkably diverse today, but their diversity was low in the Eocene and only increased dramatically from the Oligocene and onwards. Pan-Geoemydidae, on the other side, were diverse in the late Paleocene to Eocene, but their diversity decreases to their extremely low present levels starting with the Oligocene. A taxonomic review of 191 named North and Central American pan-testudinoid taxa finds 57 nomina valida, 69 nomina invalida, 64 nomina dubia, and 1 nomen nudum.