Post-Miocene Shift in Stereotypic Naticid Predation on Confamilial Prey from the Mid-Atlantic Shelf: Coevolution with Dangerous Prey

Of More than 4000 specimens of the naticid gastropods Euspira heros (Say) and Neverita duplicata (Say) from southern New Jersey, the lower Pleistocene of North Carolina, upper Miocene of Maryland, and the lower Miocene of Delaware, subsamples with complete and incomplete boreholes (n = 613) were compared for borehole-site stereotypy, prey size-selectivity, prey profitability, and prey effectiveness. In confamilial encounters, adaptation of naticid predators is evidenced by a shift in borehole-site stereotypy on the body whorl toward the umbilicus during the last 18 my, particularly for N. duplicata. Inferentially, an umbilical drilling position enabled the base of the predator's foot to occlude the prey aperture and prevent egress of the dangerous prey's foot, thereby reducing the prey's escape potential. The tradeoff was that the umbilical site required the predator to drill through a thicker shell location.