Comparisons of class- and lower taxon-level patterns in naticid gastropod predation, Cretaceous to Pleistocene of the U.S. Coastal Plain

Predation by drilling gastropods provides evidence of predator–prey interactions usually lacking in the fossil record of other systems; the record of gastropod drilling has been used to test hypotheses concerning the role of ecology in evolution. Initial tests of the hypothesis of escalation employed assemblage-level estimates of drilling frequencies. Use of assemblage-level data to estimate predation intensities has been criticized because results based on such data may be confounded by varying relative abundances of prey taxa with different morphologies and adaptive syndromes. We tested the robustness of Cretaceous–Pleistocene temporal patterns previously derived from 28 Atlantic and Gulf Coastal Plain assemblages based on data for eight common bivalve and gastropod prey families and eleven additional long-ranging bivalve taxa of subfamily to species rank.Despite changing relative abundances of taxa through time, the general patterns of temporal change in drilling apparent at the assemblage level also occur within lower taxa. The assemblage-level pattern of fluctuating drilling frequencies, with peaks during the Paleocene to middle Eocene, early Oligocene, and middle Miocene to early Pliocene, was replicated for all families except noetiid bivalves and naticid gastropods. With occasional departures, the bivalve taxa at the subfamily to species rank also paralleled patterns for the assemblage as a whole. Statistically significant or nearly significant correlation coefficients between drilling frequencies of lucinids and crassatellids, arcids and crassatellids, carditids and crassatellaceans, and corbulids and arcids over time also indicate that drilling frequencies for these taxa changed synchronously.In contrast, “prey effectiveness” (effectiveness of prey defenses as measured by number of incomplete drill holes: total attempted holes) for lower taxa generally did not correspond to patterns at the assemblage level. All correlation coefficients for prey effectiveness for pairs of lower taxa were nonsignificant, suggesting that changes in prey effectiveness were not synchronized among taxa.Use of assemblage-level estimates in concert with analyses of lower taxa enables reconstruction of the history of predator–prey interactions and testing of hypotheses in evolutionary paleoecology. Assemblage-level estimates, at least in this study, appear to be reliable indicators of changes in the intensity of drilling predation through time. Changes in prey effectiveness appear to be more individualistic and may be affected by the evolutionary response of particular prey taxa to predators.