Objectives of Study

vertebrates from the Western Interior of North America. These fossils provide important information on the distinc-tiveness of the southern vertebrates. Turtle fossils (388 specimens) were collected from 13 sites in the upper shale member of the Aguja Formation (late Campanian) of Big Bend. Turtles include: Baenidae indet., cf. Hoplochelys, Adocus, Basilemys, trionychids, and cf. Helopanoplia. The most abundant turtles are the trionychids (8 I%), with all others less than 10%; Adocus (6%), Basilemys (6%), baenid (5%) and kinostemoid (1%). The Aguja turtle assem-blage is similar, but possibly more diverse, than that of the contemporaneous Fruitland and Kirtland turtle fauna of New Mexico. Turtles are sensitive proxies to paleoclimatic change; higher turtle diversity has been shown to corre-spond to warmer climates. This trend continues in the Big Bend turtle record, and detailed paleoclimatic reconstruc-tions were compared with turtle diversity. The highest turtle diversity occurred in the late Campanian and the lowest diversity in the Maastrichtian