Article: Traces and trends of predation, with special reference to bivalved animals [Palaeontology Review]
Predation is an ecological interaction which has had a profound impact on the course of organic evolution. Full understanding of this impact can come only when fossil traces of predation are interpreted properly and catalogued systematically. The most reliable traces are those left after unsuccessful attempts by predators to subjugate their prey.Although predation seems to have increased in evolutionary importance through the course of the Phanerozoic, gastropods and bivalved animals have generally differed in their response to it. Gastropods have tended to emphasize armour, whereas the chief defences of bivalved animals have been escape from and avoidance of predators. The reason for this difference in evolutionary response is hypothesized to lie in the consequences of shell damage. For gastropods, non-lethal damage probably does not increase susceptibility to other causes of death, but for many bivalved animals marginal valve damage increases detectability of the prey because metabolites leach from the soft tissues even when the valves are shut. Accordingly, most pelecypods have very low frequencies of shell repair, and their potential for evolving resistance to breakage is much smaller than that of gastropods.