TAXONOMY OF RUDIST BIVALVES FROM UPPER CRETACEOUS STRATA, MISSISSIPPI EMBAYMENT, USA

Rudist bivalve taxonomy and paleoecology have been analyzed for many Upper Cretaceous localities within the Caribbean Basin, but rudist investigations from the Mississippi Embayment have not yet been conducted. Our objectives are to examine rudists from the Campanian and Maastrichtian of the Mississippi Embayment - the Selma Group in the east including the Mooreville, Demopolis, Ripley, and Prairie Bluff formations, and the Taylor Group in the west inclusive of the Ozan and Marlbrook formations.

Of 205 specimens from the Mississippi Museum of Natural Science and the Alabama Museum of Natural History, 183 were identified to family rank. The Campanian Mooreville and Demopolis formations contained 149 and 15 specimens, respectively, and the Ozan and Marlbrook formations contained four and one specimen, respectively. The Maastrichtian Ripley and Prairie Bluff formations contained three and 26 rudists, respectively. The family Radiolitidae dominates the fauna, with 147 specimens, followed by Hippuritidae at 26, Monopleuridae with five, and Caprinidae at two. Ninety-five specimens were identified to genus, with common genera from the embayment - Biradiolites, Radiolites, Durania, and Parastroma - also well-represented in Caribbean strata. Rudist specimens are preserved primarily as partial lower or attached valves. Epibionts are present on the exterior and interior of 36/205 specimens. Continued investigation of the taxonomy and paleoecology of these rudists will allow for comparison of Mississippi Embayment to Caribbean data to gain a broader, regional perspective on the evolutionary history of this unique group.