Inoceramus

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Inoceramus
Fossil range: Cretaceous

Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Subclass:	Pteriomorphia
Order:	Praecardioida
Family:	Inoceramidae
Genus:	Inoceramus Sowerby, 1814

Species

Several, including:
Inoceramus bellvuensis
Inoceramus biformis
Inoceramus comancheanus
Inoceramus dakotensis
Inoceramus perplexus
Inoceramus pictus
Inoceramus proximus
Inoceramus triangularis
(but see below)

Inoceramus is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus Pteria.

The species of Inoceramus enjoyed a worldwide distribution during the Cretaceous period. Many examples are found in the Pierre shale of the Western Interior Seaway in North America. Inoceramus can also be found abundantly in the Cretaceous Gault Clay that underlies London. Other locations for this fossil include Vancouver Island, British Columbia, Canada; Texas, Tennessee, California and Alaska, USA; Spain, France, and Germany.

The clam had a thick shell paved with "prisms" of calcite deposited perpendicular to the surface, which gave it a pearly luster in life. Most species have prominent growth lines which appear as raised semicircles concentric to the growing edge of the shell. Paleontologists suggest that the giant size of some species was an adaptation for life in the murky bottom waters, with a correspondingly large gill area that would have allowed the animal to cope with oxygen-deficient waters.

The number of valid species is disputed. The taxonomy of the inoceramids is also disputed, with genera such as Platyceramus sometimes classified as subgenus within Inoceramus.