''Inoceramus cuvieri'' is an extinct

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of the extinct genus ''

Inoceramus ''Inoceramus'' (Greek: translation "strong pot") is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus '' Pteria''. They lived from the Early Jurassic to l ...

'' of Bivalve mollusks that serves as an

index fossil Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bio ...

of chalky rocks of

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded b ...

age of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

Period in Europe and North America.

Description

''Inoceramus cuvieri'' are commonly found as brown shells, usually with some shine. Immature ''I. cuvieri'' are not as flat as other shells in the same rock, having a high hump for its umbo, and having much thinner growth lines. Immature thin shells appear as fragile as other bivalves found in the same rocks. Mature ''I. cuvieri'' are flat and can be around 1 meter in size, leaving much thicker shells.

Environment

''Inoceramus cuvieri'' lived in shallow, temperate, normal-salinity inland seaways where the bottom was calcareous mud, corresponding to the maximum depth and width of the Greenhorn sequence of the

Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, and the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses. The ancient sea ...

. The depths of as much as were far enough from shore for clear water and slow sedimentation, and the bottom deep enough for rare wave action disturbance. Fragments of shells from large individuals are encrusted by ''Ostrea congesta'', two ''

Serpula ''Serpula'' (also known as calcareous tubeworm, serpulid tubeworm, fanworm, or plume worm) is a genus of sessile, marine annelid tube worms that belongs to the family Serpulidae. Serpulid worms are very similar to tube worms of the closely re ...

'' species, and other sessile animals, reflecting that the shells of large ''Inoceramus'' floating on the mud were commonly the only hard surfaces available for colonization.

Distribution

''Inoceramus cuvieri'' are found throughout both middle Turonian Europe and the middle Turonian Western Interior Seaway. In the High Plains of North America, ''I. cuvieri'' is an index fossil of the chalky lower

Carlile Shale The Carlile Shale is a Turonian age Upper/Late Cretaceous series shale geologic formation in the central-western United States, including in the Great Plains region of Colorado, Kansas, Nebraska, New Mexico, North Dakota, South Dakota, ...

and upper Greenhorn Limestone and the corresponding bedding of the

Mancos Shale The Mancos Shale or Mancos Group is a Late Cretaceous (Upper Cretaceous) geologic formation of the Western United States. The Mancos Shale was first described by Cross and Purington in 1899 and was named for exposures near the town of Mancos, ...

, and shells of juveniles are particularly common in the

Fencepost limestone Fencepost limestone, Post Rock limestone, or Stone Post is a stone bed in the Great Plains notable for its historic use as fencing and construction material in north-central Kansas resulting in unique cultural expression. The source of this st ...

bed.

References

External links

Cretaceous Atlas of Ancient Life: Additional immature ''I. cuvieri'' images

Cretaceous Atlas of Ancient Life: Possible alternate source of thick, encrusted shells
Inoceramidae Turonian life Prehistoric bivalves Index fossils {{Cretaceous-animal-stub, add information on mature form, indexing use, citations, and global distribution.