New Mexico Geological Society Annual Spring Meeting — Abstracts

Nonmarine siliciclastic strata of the Upper Cretaceous McRae Formation are exposed in south-central New Mexico in Sierra County, primarily across the Cutter sag, between the Fra Cristobal Mountains and Caballo Mountains. Dinosaur fossils have been known from the Hall Lake Member for more than a century and have been long regarded as of late Maastrichtian (Lancian) age, but no other vertebrates have been reported. Recent collecting has recovered fragmentary but identifiable turtle fossils from the Hall Lake Member. These include several small carapace fragments referable to the paracryptodire genus Compsemys, which is a Campanian-Paleocene taxon. A small carapace fragment referable to Denazinemys or a similar, pustulose-textured baenid, which are known from the Campanian-Paleocene. A large turtle is represented by substantial portions of the carapace and plastron and is tentatively identified as a bothremydid based on the lack of fusion of the shell, the size and surface sculpture. Bothremydids are known from the Campanian and Maastrichtian of North America. In addition, an indeterminate frontal bone of a turtle was found. These turtles provide a lower limit on the age of the Hall Lake Member of Campanian and add to the sparse record of Late Cretaceous turtles in the southern portion of the Western Interior.