New fossils from the Oligocene of the southeastern U.S.A. support an ancient origin for the platylepadid turtle barnacles (Thoracica, Coronuloidea)

Alabamalepas cookei gen. et sp. nov. is described herein based on specimens from the lower Oligocene of the U.S. Gulf Coast and Atlantic Coastal Plain. This new taxon is significant as it represents the geologically oldest form that can be placed within Platylepadidae, an extant family of turtle barnacles (Cirripedia, Coronuloidea) whose fossil record is essentially Pleistocene. Alabamalepas cookei gen. et sp. nov. possesses a longitudinal strengthening ‘bolster’ such as is present on the wall plates of the living genera. Like the extant Cylindrolepas Pilsbry, 1916 and Calyptolepas Frick, Zardus & Lazo-Wasem, 2010, which Alabamalepas cookei gen. et sp. nov. most closely resembles in terms of general morphology, the early platylepadids may have dwelt on the carapace and plastron of sea turtles.