Fossil Testudinine Turtles of Florida, Genera Geochelone and Floridemys

Abstract

Recent paleontological work in Florida has made available a large series of fossil tortoises from one relatively small area. Two distinct species of tortoises of the genus Geochelone are represented in the known Pleistocene localities of the area, Geochelone crassiscutata (Leidy) and G. incisa (Hay). The only valid Pliocene species of this genus is Geochelone havi (Sellards). The Florida Miocene contains only Geochelone tedwhitei (Williams). These four species seem to represent two main evolutionary lines. Both lines are recognized as distinct subgenera, Hesperotestudo and Caudochelys; the latter is new G. incisa is the last representative of Hesperotestudo, a line possibly beginning with G. amphithorax (Cope) of the Oligocene of Colorado, and continuing through G. osborniana (Hay) and related forms of the late Tertiary. The new subgenus Caudochelys is represented in the Florida Pleistocene by G. crassiscutata. The subgenus can be traced from G. ligonia (Cope) of the Oligocene of Colorado through G. tedwhitei of the late Tertiary of Florida, and related species of middle and western North America. Floridemys nanus (Hay) is known only from the Florida Pliocene. Its relationships remain obscure.