NEW MARINE REPTILE REMAINS AND GREATLY EXPANDED DIVERSITY FROM THE LATE CRETACEOUS OF SOUTH CAROLINA

Despite two centuries of sporadic prospecting and research, the fossil marine reptile communities of the upper Cretaceous rocks of the South Carolina coastal plain have still not been thoroughly characterized. We greatly expand their known diversity with the study and description of one of the largest known relevant collections, consisting of over forty marine reptile teeth housed at the Mace Brown Museum of Natural History (Charleston SC) and hailing from the Campanian/Maastrichtian Donoho Creek and Peedee formations. Previous studies have confidently identified only turtles, indeterminate plesiosaurs, and the two mosasaurs Tylosaurus and Prognathodon. Careful morphological scrutiny (involving traits like shape, serration, carinal angle, dental faceting) and application of morphometric data comparisons permit many taxa never before reported from the state to be identified from this collection. These include the first plesiosaur remains from the state diagnostic below ordinal level, (Elasmosauridae indet.), the state’s first occurrence of Clidastes propython, and the South Carolina’s first Mosasaurus finds (including teeth likely from the gigantic apex predator M. hoffmanni). While these taxa are cosmopolitan and typical of many assemblages of this age, the collection also revealed several surprises. These include the furthest east occurrence ever documented of Mosasaurus missouriensis, a taxon associated with the Western Interior Seaway. No less interesting are extremely anomalous teeth assignable to no known species but somewhat resembling Prognathodon and “Liodon.” Therefore, while aspects of the fauna are typical and match expectations for the location and interval, others raise questions. Presence of M. missouriensis points to its widespread presence outside the Western Interior Seaway and Mississippi Embayment, in American epicontinental waters more broadly. The anomalous teeth, meanwhile, suggest that better material may eventually allow the description of new species in this little-prospected area. Thus, while this study marks a major milestone in understanding Cretaceous marine reptile faunas in a little-studied corner of the continent, it also demonstrates how much work remains to be done, and points to promise of future discoveries.