IMPLICATIONS OF FOSSIL SHARK TEETH SPECIES IDENTIFIED FROM NORTH TOPSAIL BEACH, NORTH CAROLINA

North Topsail Beach is the northern part of an elongate barrier island along the modern North Carolina coast. Its northeastern shoreline (in Onslow County), from 34°27'N, 77°30'W to 34°32'N, 77°21'W (29-39 mi or 47-64 km N 55°E from Wilmington) yielded a number of fossil shark teeth, many too tiny and worn to be identified, but many others identifiable from previous literature catalogued by Al Robb III. What is the source of these fossils? From where might they be coming?

Overall, 300 shark teeth were identified, evenly split among thin (T), intermediate (I), and wide (W) shapes, [with common names in brackets], some species abundant (***, 80-90 specimens), others common (**, 35-45) or uncommon (*, 20-25), the rest rare (unmarked, 1-15). Nearly 50 specimens belong to 1 species previously reported only in Cretaceous deposits, presently extending to 85 mi (135 km) inland from the coast (**Scapanorhynchus texanus [no common name] T). Twice as many specimens in 6 species are recorded from Paleo-Eocene (and younger) sediments inland (*Galeocerdo aduncas [tiger shark] W; Hemipristis wyattdurhami [snaggletooth] W; Isurus oxyrhinchus [mako] T; Odontaspis [sand sharks] cuspidata, elegans T; Procarcharodon auriculatus [white shark] I). Roughly 150 specimens representing 5 species are known only from Mio-Pliocene strata nearest the coast, 10-60 mi (15-100 km) inland (*Carcharinus egertoni [requiem shark] W; Carcharodon (Carcharocles) megalodon [pre-great-white shark] I; Galeocerdo cuvier [tiger shark] W; *** Hemipristis serra [snaggletooth] W; ** Isurus desorii [mako] I).

The numerous shark teeth on North Topsail Beach might indicate erosion from a point source nearby. However, the 50-100-150 numbers progressively nearer the coastline suggest instead that the teeth represent normal erosion across the entire coastal plain, with the greatest proportion of the teeth coming from the youngest deposits nearest the coast.