Veneroida

The Veneroida are a large order of bivalve mollusks, making up over 30% of all extant bivalve species. These marine, estuarine, and freshwater organisms are characterized by their equivalve shells, which typically have outer crossed-lamellar and inner complex crossed-lamellar layers. The hinge structure often features radiating cardinal and lateral teeth, though these can be weakly developed. Veneroida exhibit varied adductor muscle proportions and eulamellibranch ctenidia. Many species possess extensively fused mantle margins, often forming long siphons that aid in burrowing, a common habit for this order. Some Veneroida are epibyssate, attaching themselves to surfaces. This diverse group includes many species that are economically important as food sources, such as clams and cockles.123