Veneroida

Veneroida
	; Empty cockle shell, family Cardiidae
Scientific classification
Kingdom:	Animalia;
Phylum:	Mollusca;
Class:	Bivalvia;
Subclass:	Heterodonta;
Order:	Veneroida;
Families
	See text.

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The Veneroida or veneroids are an order of bivalve molluscs. They include some familiar forms such as saltwater clams and cockles, and a number of freshwater bivalves including zebra mussels.

Veneroids are generally thick-valved, equal valved, and isomyarian (that is, their adductor muscles are of equal size). Three main hinge teeth are characteristic of the subclass Heterodonta to which this order belongs. Many species are active rather than sessile. However they tend to be filter feeders, feeding through paired siphons, with a characteristic folded gill structure adapted to that way of life.

Recent work in molecular systematics has suggested that this order is not monophyletic. If this conclusion is sustained, the order will presumably be broken up in due course.