Résumé
Cardichelyon rogerwoodi 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
Platysternon megacephalum, 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 Cardichelyon rogerwoodi within Testudinoidea
but the exclusion of testudinoids suggest an affiliation with
Dermatemydidae. Using consilience with external data we favor placement
within Kinosternoidea. Cardichelyon rogerwoodi 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.