PRELIMINARY NOTE ON MIDDLE CAMPANIAN (LATE CRETACEOUS) VERTEBRATES FROM DARLINGTON COUNTY, SOUTH CAROLINA

Several hours of collecting from highly fossiliferous Cretaceous sediment occurring in Darlington County, South Carolina, resulted in the discovery of a vertebrate assemblage that consists predominantly of elasmobranchs (primarily teeth, but also scales and fin spines). Teleosts, crocodilians, chelonians, and dinosaurs are represented by isolated teeth and bone/shell fragments, but of greater significance was the recovery of multituberculate and marsupial mammal teeth. Lithologically and palynologically the stratum can be identified as the Coachman Formation (calcareous nannofossil Zone CC 20, 78.8 to 77.2 Ma).

The Coachman Formation is typically only encountered in subsurface, and the Darlington County site provided a rare opportunity to collect macrofossils from this lithostratigraphic unit. The vertebrate fossils identified provide important clues as to the depositional environment that existed in South Carolina, the paleobiogeographic distributions of taxa within the Atlantic Coastal Plain, and the phylogenetic relationships of these taxa to those occurring in the Campanian throughout North America.

The Coachman vertebrate assemblage compares well to the known record from the Tar Heel Formation of North Carolina (also CC 20) and the upper Campanian Donoho Creek Formation (CC 22c) in Florence County, SC. However, the Tar Heel Formation contains abundant mosasaur material and fewer benthic elasmobranchs, indicating a more marine signal to the assemblage. Also, the greater variety and frequency of terrestrial and shallow-water taxa, as well as the abundance of large fossils (> 15 cm in length), indicate that the Coachman Formation accumulated closer to shore than the Donoho Creek Formation. In these respects, the Coachman Formation fossil assemblage is most similar to that from the Marshalltown Formation of New Jersey and could therefore be indicative of a barrier island coastal environment.