Basis for a Pelecypod Taxonomy
Pelecypods, bivalve molluscs, also known as bivalvia, can be subdivided into orders and suborders on basis of shell structure, hinge teeth, and type of gills. Those included in the Prionodesmata have shells that are prismatic and nacreous. Mantle lobes are separate, siphons poorly developed, hinge teeth lacking or unspecialized. Those included in the Teleodesmata have shells that are porcelaneous and in part nacreous. Mantle lobes are generally connected, siphons well developed, hinge teeth specialized. Gills, which help determine suborder, may be protobranch, filibranch, eulamellibranch or septabranch, going from the simplest and most primitive to the most advanced and evolved. Orders are determined largely on the basis of dentition, that is hinge teeth. Order with included suborders are: Taxodonta: hinge teeth numerous, subequal, and small. Includes the Nuculacea which have protobranch gills and the Arcacea which have fillibranch gills. Schizodonta: teeth large and distin