Venerida

Venerids 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. In 2002, Gonzalo Giribet and Ward Wheeler suggested that the orders Myoida and Veneroida were not monophyletic. They have since been widely reorganised. ==Orders and families==

Order: Venerida • Superfamily: †Anthracosioidea • Family: †Anthracosiidae • Family: †Ferganoconchida • Family: †Shaanxiconchidae • Superfamily: Arcticoidea • Family: Arcticidae • Family: †Pollicidae • Family: Trapezidae • Family: †Veniellidae • Superfamily: Chamoidea • Family: Chamidae • Superfamily: Cyrenoidea • Family: Cyrenidae • Family: Cyrenoididae • Family: Glauconomidae • Superfamily: Glossoidea • Family: Glossidae • Family: Kelliellidae • Family: †Lutetiidae • Family: Vesicomyidae • Superfamily: Hemidonacoidea • Family: Hemidonacidae • Superfamily: Mactroidea • Family: Anatinellidae • Family: Cardiliidae • Family: Mactridae • Family: Mesodesmatidae • Superfamily: Galeommatoidea • Family: Galeommatidae • Family: Kellidae • Family: Lasaeidae • Family: Leptonidae • Family: Montacutidae • Superfamily: †Palaeanodontoidea • Family: †Palaeanodontidae • Superfamily: †Prilukielloidea • Family: †Prilukiellidae • Family: †Senderzoniellidae • Superfamily: Ungulinoidea • Family: Ungulinidae • Superfamily: Veneroidea • Family: †Isocyprinidae • Family: Neoleptonidae • Family: Veneridae ==References==