NEW LATE PLIOCENE AGE ECHINOID FAUNA OF FLORIDA AND SOUTH CAROLINA

Three previously undescribed late Pliocene species of Echinoidea have been collected by the authors in the southeastern United States. Plagiobrissus sarae (Ciampaglio, Osborn and Weaver), from the Goose Creek Limestone of South Carolina, was recently formalized by the authors, and is now the largest described species of Spatangoid echinoid described from the Cenozoic of North America, and the first species of Plagiobrissus from the Pliocene of North America. Recent reviews of collections from the late Pliocene age Intracoastal Formation of the Florida panhandle, and Tamiami Formation of south Florida have uncovered specimens of Plagiobrissus sarae from these units as well. These occurrences greatly expand the distribution of this large late Pliocene age species from its type locality in South Carolina to south Florida, and the Florida Gulf Coast.

Three complete and numerous partial specimens of an undescribed species of the genus Schizaster are currently being described by the authors. Collected from the late Pliocene age Intracoastal Limestone of the Florida panhandle, these specimens represent the first occurrence of the genus Schizaster in the Pliocene of the southeastern United States, and expand the known echinoid fauna of the Intracoastal Formation to eight species, including: Genocidaris sp. , Arbacia improcera (Conrad), Clypeaster sunnilandensis (Kier), Encope aberrans (Martens), Encope macrophora (Ravenel), Echinocardium orthonotum (Conrad) and Plagiobrisus sarae (Ciampaglio, Osborn and Weaver).

Additionally, four specimens of a new species of the genus Arbacia have been collected from the late Pliocene age upper Goose Creek Limestone of South Carolina. These specimens have a very large, low test with the height equal to merely 39-41% the diameter of the test and tubercles present on alternating interambulacral plates adjacent to the ambulacral from slightly above the ambitus to the apical. These traits readily differentiate these specimens from Abracia improcera (Conrad), which resides in middle-late Pliocene strata below the occurrence of this species, and Arbacia waccamaw (Cooke) which resides in strata above this species.