Human Origins: The Fossil Record

3rd ed. By Clark Spencer Larsen, Robert H. Matter, and Daniel L. Gebo. Prospect Heights, IL: Waveland Press. 1998. 225 pp. ISBN 1-57766-002-1. $18.95 (paper).     

The Fossil Record of Shell Boring by Snails

The predatory boring habit common to many recent snails probablyarose first in the Polinicinae (Naticacea) during Upper Cretaceous(Cenomanian) times (100 million years B.P.) . In the fossilrecord the frequency of bored shells increasesgreatly in rocksof latest Cretaceous age and becomes more widespread duringearly Tertiary times coincident with the major diversificationof the primary groups of boring snails. The borings in these Cretaceous and Tertiary shells show thesame characteristics of preference of penetration in one pelecypodvalve rather than the other or in position of the boring siteon the shell that are found in recent shell assemblages. Borings in Paleozoic brachiopod shells (230–550 millionyears old) that have previously been attributed to gastropodpredation are herein attributed to other but unknown boringorganisms. In part these borings are not accepted as evidence of Paleozoicgastropod predation because it necessitates: (1) Postulationof the separate development of a boring habit ith its concomitantdevelopment of an accessory boring organ in a groupwhose descendantsare all herbivores, and (2) The development of such a habithundreds of millions of years before the appearance of any relativesof present day borers.