GEOGRAPHIC RANGE EXTENSION AND PALEOBIOGEOGRAPHIC SIGNIFICANCE OF THE LATE CRETACEOUS KINOSTERNID TURTLE YELMOCHELYS

Yelmochelys rosarioae was recently described from the Cerro del Pueblo Formation (Campanian) in northeastern Mexico (Coahuila) and also reported from the nonmarine portion of the Cańon del Tule Formation (Maastrichtian), also in Coahuila. We report Yelmochelys from the Late Cretaceous (Campanian) Kaiparowits Formation of Utah. This is the most northern record of Yelmochelys, and its first USA record. The identification is based on the near identical nature of the available Kaiparowits material, consisting of 24 carapace fragments and six fragments of the hyoplastron and hypoplastron, to illustrated, anatomically equivalent elements of Yelmochelys from Mexico This large geographic range extension fits with that of many extant kinosternids, which demonstrate considerable ability to disperse over obstacles. Conversely, we believe the latitudinally intermediate Fruitland Formation (northwestern New Mexico) kinosternid material is not from Yelmochelys. Given the long temporal range reported for Yelmochelys, it is unlikely this is the result of an age difference. Instead, this likely reflects a change in environment of deposition. Thus, multiple extant kinosternids are known to inhabit the same or closely spaced geographic areas, but they normally inhabit different micro-habitats in the same area (e. g., one species may favor river banks, another lacustrine settings). We suggest this apparently disjunct distribution of Yelmochelys, with the gap in the Fruitland Formation and presence in the Cerro del Pueblo and Kaiparowits formations, results from the relatively inland paleoenvironment at both the type locality and of the Kaiparowits Formation. Thus, the Fruitland Formation kinosternid material represents a more lowland environment. This hypothesis will potentially be tested by further excavations in northwestern New Mexico in the overlying Hunter Wash Member of the Kirtland Formation, which has a more upland paleoecology. Current, supposed kinosternid material from the De-na-zin Member of the Kirtland Formation should be considered a probable dermatemydid and thus provides no test of this hypothesis. Yelmochelys has a southerly distribution from Utah to Mexico that may fit the pattern of a distinctive southern turtle fauna in the Campanian of the Western Interior basin.