PREDATION BY GASTROPODS ON OSTRACODES ACROSS THE PLIOCENE-PLEISTOCENE BOUNDARY, SOUTHEASTERN NORTH CAROLINA

The Pliocene-Pleistocene boundary in the Atlantic Coastal Plain of North America is characterized by a significant extinction of mollusks, including a decrease in predatory naticid gastropods that feed on clams by boring through the shell. As juveniles the gastropods also feed on ostracodes. Ostracodes were collected from three localities in southeastern North Carolina, one in the late Pliocene (3.0 Ma) Duplin Formation and two in the lower Pleistocene (2.5-1.9 Ma) Waccamaw Formation to determine if there was a change in predation on ostracodes as indicated by the presence of bore holes.

More than 300 specimens of ostracodes were identified and the number of bored valves tallied. Fourteen species were identified in the Duplin Formation at Natural Well, dominated by Malzella evexa and Hulingsina rugipustulosa; one valve (1.0 %) had unequivocal evidence of predatory borings. The lowest Pleistocene sample from Register Quarry contained seven species, the most abundant species are Bairdia laevicula and Microcytherura similis. Of these taxa, three are shared with the Duplin Formation; one specimen (1.1 %) was bored by gastropods. At Walker’s Bluff, the youngest locality, eight species were recognized, dominated by Anomocytheridea curta and Hulingsina ashermani; two species were found in common with Register Quarry and four were in common with Natural Well. Two valves (1.8 %) had bore holes. The fauna at Register Quarry in the lower Waccamaw Formation had more articulated ostracodes, approximately 50 % as compared to less than 10 % at the other two localities.

Across the Pliocene-Pleistocene boundary, assuming the same depositional setting, there is a decrease in ostracode diversity, but any change in predation as indicated by the relative frequency of bore holes produced by juvenile naticids is equivocal based on the difference in preservation and taxa recovered.

Additional authors: Wistort, Zachary, Over, D. Jeffrey, Geological Sciences, SUNY-Geneseo, and Dietl, Gregory, Paleontological Reserch Institution, Ithaca, NY.