Unionoida

views updated

Unionoida (phylum Mollusca, class Bivalvia) An order of unequilateral, and generally equivalved, marine and non-marine bivalves whose shell shape and size is very variable and whose ornamentation is usually simple. The musculature is isomyarian to sub-isomyarian. The ligament is external and opisthodetic. The dentition is quite variable, forms having one or two teeth, some pseudotaxodont and some edentulous. They first appeared in the Upper Devonian.

About this article

Unionoida

Updated About encyclopedia.com content Print Article Share Article