Prehistoric bivalves

thumb|Rudist bivalve, Maurens Formation, Upper Cretaceous, southwestern France

Trigoniida is an order of medium-sized saltwater clams, marine bivalve molluscs. Within the fossil record the occurrence of this order is widespread, ranging from the Devonian Period to Recent.

Trigonioidea is superfamily of medium-sized saltwater clams, marine bivalve molluscs. Within the fossil record the occurrence of this superfamily is widespread, ranging from the Devonian Period to Recent.

Modiomorphida is an extinct order of fossil saltwater clams, marine bivalve molluscs.