A baenid turtle shell from the Mesaverde Formation (Campanian, Late Cretaceous) of Park County, Wyoming, USA

Abstract

The Mesaverde Formation of the Wind River and Bighorn basins of Wyoming preserves a rich yet relatively unstudied terrestrial and marine faunal assemblage dating to the Campanian. To date, turtles within the formation have been represented primarily by isolated fragments diagnostic only to broader clades. A baenid specimen from the lower third of the Mesaverde Formation in the northwestern Bighorn Basin of Park County, Wyoming, includes a partial carapace and plastron and is the most complete turtle specimen yet described from the formation. The entire carapace would have been around 450 mm long and 380 mm wide, indicating a fairly large individual. The preserved portions of the carapace are smooth and unornamented, and the overall oval dorsal profile of the shell is similar to taxa such as Neurankylus spp. The anterior plastral