File:Idonearca vulgaris (fossil bivalve) (Coon Creek Formation, Upper Cretaceous; Coon Creek site, McNairy County, Tennessee, USA) 5.jpg

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English: Idonearca vulgaris (Morton, 1830) - fossil bivalve shell from the Cretaceous of Tennessee. (external view of a left valve; ~7.7 centimeters across at its widest)

This species is also known as Cucullaea (Idonearca) vulgaris.

Orientation: anterior to the left; posterior at right; dorsal at top; ventral at bottom

Bivalves are bilaterally symmetrical molluscs having two calcareous, asymmetrical shells (valves) - they include the clams, oysters, and scallops. In most bivalves, the two shells are mirror images of each other (the major exception is the oysters). They occur in marine, estuarine, and freshwater environments. Bivalves are also known as pelecypods and lamellibranchiates.

Bivalves are sessile, benthic organisms - they occur on or below substrates. Most of them are filter-feeders, using siphons to bring in water, filter the water for tiny particles of food, then expel the used water. The majority of bivalves are infaunal - they burrow into unlithified sediments. In hard substrate environments, some forms make borings, in which the bivalve lives. Some groups are hard substrate encrusters, using a mineral cement to attach to rocks, shells, or wood.

The fossil record of bivalves is Cambrian to Recent. They are especially common in the post-Paleozoic fossil record.

This well-preserved, three-dimensional fossil bivalve shell is a false ark clam. It comes from a famous Cretaceous-aged marine deposit in western Tennessee called Coon Creek. Fossils there occur in a nearshore succession of lightly-cemented, glauconitic, clayey sands. During the Cretaceous, the lower and middle Mississippi River Valley region was below sea level - the ocean extended from Louisiana and Mississippi up north to Arkansas, western Tennessee, and the Illinois-Missouri-Kentucky tristate area.

Classification: Animalia, Mollusca, Bivalvia, Pteriomorphia, Arcoida, Arcoidea, Cucullaeidae

Stratigraphy: Coon Creek Formation (a.k.a. Coon Creek "Tongue" of the Ripley Formation), lower Maastrichtian Stage, upper Upper Cretaceous

Locality: Coon Creek site (apparently = exposures at the Coon Creek Science Center, along Hardin Graveyard Road, adjacent to Coon Creek), just northeast of the town of Leapwood, northeastern McNairy County, southwestern Tennessee, USA
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Source https://www.flickr.com/photos/47445767@N05/49615261343/
Author James St. John

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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/49615261343. It was reviewed on 14 October 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0.

14 October 2020

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current03:56, 14 October 2020Thumbnail for version as of 03:56, 14 October 20202,159 × 1,976 (5.01 MB)Ser Amantio di Nicolao (talk | contribs)Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/49615261343/ with UploadWizard

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