Abstract

Neotrigonia is a very active, free-living bivalve, yet its adult foot contains a rather extensive, though nonfunctional, byssal apparatus. Is this apparatus a phylogenetic residue, reduced from its form in a byssate adult ancestor, or does it function at an earlier stage of trigonian ontogeny? There is no firm evidence for the existence of a byssus in Mesozoic adult trigonians. Gould favors the hypothesis that the trigonian byssus is functional in juveniles for two reasons: Most, and perhaps all, bivalves are byssally attached in the post-larva and several prolong this habit into later juvenile stages. In the single juvenile specimen examined, the byssal organs were better developed than in adults.

You do not currently have access to this article.