Turtles of the total clade Pan-Chelydridae have a relatively sparse fossil record that reaches back to the Late Cretaceous (Santonian). The clade was only present in North America during the Cretaceous but spread along unclear routes to Asia and Europe during the Paleocene, only to go extinct on those continents by the end of the Pliocene. Final dispersal to South America took place at some time during the late Neogene. The ecology of stem chelydrids seems to have been similar to that of the extant Chelydra serpentina, although more primitive representatives were more molluscivorous as inferred from their broader triturating surfaces. Current phylogenies only recognize five internested clades: Pan-Chelydridae, Chelydridae, Chelydropsis, Chelydra and Macrochelys. A taxonomic review of the group concludes that of 31 named fossil taxa, 8 are nomina valida, 10 are nomina invalida, 9 are nomina dubia, 1 is a nomen nudum and 1 is a regular, unavailable name.