DRILLING PREDATION IN MOLLUSCAN ASSEMBLAGES OF THE LOWER WACCAMAW FORMATION (PLEISTOCENE) AT SNAKE ISLAND PIT IN NORTH CAROLINA
DFs for bivalves (# of complete drillholes divided by half of the whole specimens) ranged between 16% and 19% except for one sample at 25%. Much lower DFs were found for gastropods varying between 1% and 3% across the five samples. Total DFs were 19% for bivalves and 2% for gastropods with all samples combined. In each of the samples, fewer than 10 incomplete drillholes were documented for bivalves; no incomplete drillholes were recorded for gastropods. PE for bivalves based on all samples combined was 6.5%. UNCW DFs were 26% (bivalves) and 9% (gastropods) with only one incomplete drillhole noted.
Taxa drilled in these samples and their DFs are represented by Anadara (2%), Arcinella (24%), Astarte (35%), Caryocorbula (11%), Chama (4%), Conradostrea (13%), Cyclocardia (14%), Diplodonta (42%), Glycymeris (35%), Gouldia (23%), Laevicardium (6%), Lirophora (35%), and Plicatula (2%). Data from the UNCW sample revealed commonly drilled genera comprised Arcinella (53%), Diplodonta (43%), Glycymeris (40%), Laevicardium (26%), Lirophora (41%), and Plicatula (12%). Gastropods drilled in the GSU samples included Conus (2%), Crepidula (1%), and Olivella (5%). Both Conus (5%) and Crepidula (10%) were drilled in the UNCW sample. Fourteen other genera in the GSU samples and four other genera in the UNCW sample were drilled, but DFs were not calculated due to insufficient specimens (<10 individuals per genus).