TRACES OF PREDATION AND PARASITISM RECORDED IN EOCENE ECHINOIDS AND BRACHIOPODS FROM THE CASTLE HAYNE LIMESTONE, NORTH CAROLINA, USA

The Castle Hayne Limestone (Middle Eocene), located near Wilmington, North Carolina, is noted for its diverse macro-invertebrate fauna, including numerous, well-preserved echinoid tests and brachiopod shells. The most common species found are Plicatoria wilmingtonensis (Lyell and Sowerby) and Echinolampas appendiculata Emmons. These species, as well as other less-common species found, sometimes display circular holes in their test/shell that are indicative of biotic interactions, namely predation or parasitism. These trace fossils provide quantifiable data for this ecosystem of the interactions between numerous possible predators (or parasites) and two types of prey. Intensity of predation/parasitism and stereotypy of those traces (site-, taxon-, and size-specific interactions) are investigated using a collection recently acquired from the Castle Hayne/Ideal Cement and Rocky Point quarries. Placement and distribution of predation/parasitism traces on the echinoid test or brachiopod shell is quantified by dividing the test/shell into anatomically-defined sectors to determine if any anatomical correlatives are being targeted. This study demonstrates that fossil echinoids and brachiopods can provide a wealth of paleoecological information about predator-prey and parasite-host interactions. Echinoids, in particular, represent an important, if understudied, fossil system for testing the Escalation Hypothesis and, more generally, for evaluating evolutionary importance of ecological interactions. While the ecological interplay between echinoids and their enemies (e.g., drilling predators such as cassid gastropods and drilling parasites such as eulimid gastropods) is an important process in modern benthic ecosystems, a few workers have investigated such interactions in the fossil record.