Dinocardium robustum (Atlantic giant cockle shell) (Sanibel Island or Cayo Costa Island, Florida, USA) 2

Description:

Description: English: Dinocardium robustum Lightfoot, 1786 - Atlantic giant cockle shell (modern) from Florida, USA. 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. In the close-up of the Atlantic giant cockle shell shown here, just left of center, there is an area of healed damage. The injury resulted in a temporary cessation of shell growth - note the well-demarcated growth line above the disturbed area. Classification: Animalia, Mollusca, Bivalvia, Heterodonta, Veneroida, Cardiidae Locality: beach on Sanibel Island or Cayo Costa Island, southwestern Florida, USA See info. at: en.wikipedia.org/wiki/Dinocardium_robustum. Date: 13 February 2017, 16:50:01. Source: https://www.flickr.com/photos/47445767@N05/33020482192/. Author: James St. John.