Description: Noetia ponderosa (Say, 1822) - beachworn ponderous ark clam 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. This beachworn & eroded ponderous ark shell has numerous borings (click on the photo once or twice to zoom in). The structure at right is an encrusting Atlantic kittenpaw bivalve, Plicatula gibbosa. Classification: Animalia, Mollusca, Bivalvia, Pteriomorphia, Arcida, Arcidae (or Noetiidae) Locality: Lighthouse Point beach, southern shore of the eastern tip of Sanibel Island, Gulf of Mexico coast of southern Florida, USA. Date: 12 April 2020, 02:50. Source:
Noetia ponderosa (ponderous ark clam shell) (Sanibel Island, Florida, USA) 4. Author:
James St. John.
