Differentiation between the traces of predation of muricids and naticids in Spanish Pliocene Chlamys

Abstract

The statistical analysis of holes drilled in species of the bivalve genus Chlamys from localities in the Lower Pliocene of Southern Spain throws light on aspects of muricid and naticid predation. Discriminant function analysis was found to be a useful means of identifying the nature of boreholes, with but slight errors of identification for known specimens. In particular, significant differences in relationships between predators and prey could be established. The question as to whether preferred locations of boreholes occur could be answered affirmatively for muricids. Also for muricids, the majority of the observed boreholes (74.1%) are concentrated to the region fo the adductor muscle: such a relationship could not be definitely proven for naticids (36.9% within the adduetor muscle field). An association between the site of the prey and predator could only be demonstrated for naticids in connexion with prey of several species and genera. There is a strong association between the size of the prey and the site chosen for drilling for both groups of predators. There is indecisive evidence for a correlation between the location and size a drillhole for naticids, but probably not for muricids. The strategy of seleetion of a drilling site by muricids seems to• be to weaken the function of the adductor muscle in the monomyarian Chlamys, hence facilitating access to the víscera. In general, multivariate analytical procedures, and especiaIly the method of canonical correlations, were found lo aid greatly the interpretation of the quantitative observations.