Bivalvia

Article By:

Rice, Michael A. Department of Fish, Animal and Veterinary Science, University of Rhode Island, Kingston, Rhode Island.

Last reviewed:May 2020

DOI:https://doi.org/10.1036/1097-8542.085800

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• Bivalvia, published October 2019:Download PDF Get Adobe Acrobat Reader

One of the main extant classes in the phylum Mollusca. Members of the molluscan class Bivalvia (formerly, Pelecypoda) are known commonly as bivalves and include clams, oysters, mussels, and scallops. All bivalves are aquatic, living at all depths of the sea and in brackish waters and freshwaters (Fig. 1). With more than 9000 living species, Bivalvia has a rich molluscan species diversity. Moreover, the total biomass of extant bivalves is quite great, with certain bivalve species being numerically dominant in many benthic ecosystems. The most primitive bivalves are infaunal, burrowing into soft sediments, but many families are epifaunal, attached to rocks or shells or residing on the sediment surface. Bivalves are well represented in the fossil record from the Early Paleozoic because of their calcareous shells. See also: Biodiversity; Ecosystem; Mollusca

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