Data from: An alternative interpretation of the Paleogene turtle Cardichelyon rogerwoodi as a hinged kinosternoid

<p><i>Cardichelyon rogerwoodi</i> is an enigmatic fossil turtle from the late Paleocene to early Eocene of North America. Previous analyses suggested affiliation with Testudinoidea, in particular the big-headed turtle <i>Platysternon megacephalum</i>, based on the presence of multiple musk-duct foramina and a large head. We here highlight previously undocumented characteristics for this turtle, notably the presence of short costiform processes, a rib-like axillary process, and a posterior plastral hinge. Phylogenetic analysis places <i>Cardichelyon rogerwoodi</i> within Testudinoidea but the exclusion of testudinoids suggest an affiliation with Dermatemydidae. Using consilience with external data we favor placement within Kinosternoidea. <i>Cardichelyon rogerwoodi</i> is therefore an aberrant, hinged kinosternoid that developed in situ in North America during the Paleocene long before the arrival of testudinoids on this continent in the early Eocene.</p>