PaleoBios

A small smooth-shelled kinosternoid from the late Campanian Cerro del Pueblo Formation and the early Maastrichtian Canyon del Tule Formation of Coahuila, Mexico that is abundantly represented by isolated elements is described as Yelmochelys rosarioae gen. et sp. nov. A phylogenetic analysis concludes that Y. rosarioae is a representative of the stem lineage of the Kinosternidae. Inclusion of Y. rosarioae in Kinosternidae is supported by presence of a groove for the musk duct, the loss of the eleventh peripheral and twelfth marginal, reduced articulation between the plastron and carapace, and diamond-shaped vertebral scales. A basal position within Kinosternidae is indicated by the presence of distinct abdominal scales that meet at the midline and the presence of a relatively long costiform processes. The inclusion of Y. rosarioae in Kinosternidae supports the hypothesis that Kinosternidae and Dermatemydidae had diverged by the Late Campanian.