See text Tridacnidae, common name the giant clams, is a taxonomic subfamily of very large saltwater clams, marine bivalve molluscs in the family Cardiidae, the cockles.

This subfamily contains the largest living bivalve species, including Tridacna gigas, the giant clam.

They inhabit coral reefs in warm seas in the Indo-Pacific region.

Most of these clams live in symbiosis with photosynthetic dinoflagellates (zooxanthellae), a type of photosymbiosis.

[5] Tridacinae originated in Western Europe during the Eocene, expanding eastwards towards Arabia by the Oligocene, and becoming established in its modern distribution in the Indo-Pacific during the Pliocene-Pleistocene.