Inoceramus

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

Gigantic specimen of Inoceramus steenstrupi 187 cm (74 in) across, found on the Nuussuaq Peninsula, Greenland

Weathered shell fragment of the closely related Cremnoceramus difformis, highlighting the orientation and texture of the calcite prisms of the Inoceramids.

Inoceramids had thick shells composed of "prisms" of calcite deposited perpendicular to the surface, and unweathered fossils commonly preserve the mother-of-pearl luster the shells had in life.[3] Most species have prominent growth lines which appear as raised semicircles concentric to the growing edge of the shell.[3]

In 1952, the huge specimen of Inoceramus steenstrupi 187 cm long, was found in Qilakitsoq, the Nuussuaq Peninsula, Greenland. This fossil is 83 Ma old, the Upper Santonian or Lower Campanian stage.[4] 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 survive in oxygen-deficient waters.[3]

The Western Interior Seaway that covered North America during the Cretaceous

Species of Inoceramus had a worldwide distribution during the Cretaceous and Jurassic periods (from 189.6 to 66.043 Ma).[1] 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,[3] British Columbia, Colombia (Hiló Formation, Tolima and La Frontera Formation, Boyacá, Cundinamarca and Huila),[5] Spain, France, Germany, Afghanistan, Albania, Algeria, Angola, Antarctica, Argentina, Australia, Austria, Brazil, Bulgaria, Canada (Alberta, Northwest Territories, Nunavut, Saskatchewan, Yukon), Chile, China, Cuba, the Czech Republic, Denmark, Ecuador, Egypt, Greenland, Hungary, India, Indian Ocean, Iran, Italy, Jamaica, Japan, Jordan, Kenya, Libya, Madagascar, Mexico, Morocco, Mozambique, Nepal, New Caledonia, New Zealand, Nigeria, Papua New Guinea, Peru, Poland, the Russian Federation, Saudi Arabia, Serbia and Montenegro, South Africa, Sweden, Switzerland, Tunisia, Turkey, Turkmenistan, the United Kingdom, United States (Alabama, Alaska, Arizona, Arkansas, California, Colorado, Delaware, Idaho, Iowa, Kansas, Maryland, Minnesota, Mississippi, Montana, Nebraska, New Jersey, New Mexico, North Carolina, North Dakota, Oregon, South Carolina, South Dakota, Tennessee, Texas, Utah, Washington, Wyoming), and Venezuela.[1]

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  Inoceramus from the Cretaceous of South Dakota
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  Inoceramus proximus
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  Inoceramus cuvieri
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  Inoceramus vancouverensis
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  Inoceramus hobetsensis

• Kennedy, W.J.; Kauffman, E.G.; Klinger, H.C. (1973). "Upper Cretaceous Invertebrate Faunas from Durban, South Africa". Geological Society of South Africa Transactions. 76 (2): 95–111.
• Klinger, H.C.; Kennedy, W.J. (1980). "Upper Cretaceous ammonites and inoceramids from the off-shore Alphard Group of South Africa". South African Museum. 82 (7): 293–320.
• Gebhardt, H. (2001). "Inoceramids, Didymotis and ammonites from the Nkalagu Formation type locakity (late Turonian to Coniacian, southern Nigeria): biostratigraphy and palaeoecologic implications". Neues Jahrbuch für Geologie und Paläontologie, Monatshefte. 2001 (4): 193–212. doi:10.1127/njgpm/2001/2001/193.
• El Qot, G.M. (2006). "Late Cretaceous macrofossils from Sinai, Egypt". Beringeria. 36: 3–163.

Wikimedia Commons has media related to Inoceramus.

• Upper Cretaceous Bivalvia of Alabama