A Review of the Fossil Record of New World Turtles of the Clade Pan-Trionychidae

Turtles of the clade Pan-Trionychidae have a rich, but fragmentary fossil record in the New World, ranging from the Late Cretaceous to the Holocene. The clade immigrated to North America from Asia no later than the Cenomanian. From the Campanian to the middle Eocene, pan-trionychid diversity in the New World was higher than it is today. In the Neogene, pan-trionychids inhabited southern North America and coastal regions of northern South America. Their range subsequently contracted, and extant New World pan-trionychids are now limited to the eastern third of temperate North America. The ecology of extinct pan-trionychids was likely similar to that of extant pan-trionychids, although novel feeding ecology has been hypothesized for some morphologically derived taxa. Current phylogenies of crown Trionychidae recognize two major clades, Cyclanorbinae and Trionychinae, but the placement of most fossil taxa remains poorly resolved relative to these two primary clades. A taxonomic review of 101 named New World taxa finds 31 nomina valida, 26 nomina invalida, 41 nomina dubia and 2 nomina nuda.