Predation intensity in an Eocene molluscan assemblage from southeastern Nigeria

Abstract

A quantitative assessment of naticid and muricid borings in mainly small (<10mm) gastropod and bivalve shells from the Ameki Formation (Eocene) shows that the degree of shell ornamentation appears to have played a significant role in predation intensity. It was observed in gastropods that a smooth shell is preferred by predators to an ornamented one. In bivalves a growth-lined shell is preferred to either a ribbed or a mixed one (growth lines and ribs present) and a ribbed shell is preferred to a mixed shell. It is suggested that the predation intensity was controlled by the predator-defensive adaptation. The favoured predator food source during the Eocene in Nigeria was bivalves, as far as shown by fossil shells.