What is Bivalve?
{{Taxobox | name = Bivalvia | fossil_range = [[Cambrian]] – Recent | image = CornishMussels.JPG | image_width = 230px | image_caption = Mussels in the intertidal zone in [[Cornwall]], England | regnum = [[Animal]]ia | phylum = [[Mollusca]] | classis = '''Bivalvia''' | classis_authority = [[Carolus Linnaeus|Linnaeus]], 1758 | subdivision_ranks = [[Subclass]]es | subdivision = }} [[File:Muscheln mit Sipho Nahaufnahme.jpg|thumb|right|230px|A large number of [[Veneridae|venerid]] bivalves with their [[Siphon (mollusc)|siphon]]s visible]] [[File:Tridacna gigas.001 - Aquarium Finisterrae.JPG|thumb|alt=Shell of the giant clam (''Tridacna gigas'')|Empty shell of the [[giant clam]] <br /> (''Tridacna gigas'')]] [[File:Sphenoceramus steenstrupi.jpg|thumb|right|200px|The world's largest clam (187 cms), a ''Sphenoceramus steenstrupi'' fossil from Greenland in the Geological Museum in Copenhagen]] The '''bivalves''' are a large class of [[mollusc]]s, also known as '''pelecypods'''. They have a hard [[calcareous]] [[Animal shell|shell]] made of two parts or 'valves'. The soft parts are inside the shell. The shell is usually [[bilateral symmetry|bilaterally symmetrical]]. There are over 30,000 [[species]] of bivalves, including the [[fossil]] species. There are about 9,200 living species in 1,260 [[genera]] and 106 [[Family (biology)|families]]. All of them live in the water, most of them in the [[sea]] or in [[brackish water]]. Some live in [[fresh water]]. All are [[filter feeder]]s: they lost their [[radula]] in the course of evolution. A few are carnivorous, eating much larger prey than the tiny micro[[algae]] eaten by other bivalves. The best known examples of bivalves are [[clam]]s, [[mussel]]s, [[scallop]]s and [[oyster]]s.<ref name=Pond>Ponder W.F. & Lindberg David R. 2008. ''Phylogeny and evolution of the Mollusca''. University of California Press. {{ISBN|0520-25092-3}}</ref> == Shell == Bivalves have two shells or valves connected by a hinge with [[hinge teeth]]. They are made of a [[calcareous]] [[mineral]], [[