Bivalvia, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bivalves have no head and they lack some usual molluscan organs, like the radula and the odontophore. The class includes the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders. The gills have evolved into ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment, where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as the scallops and file shells, can swim. Shipworms bore into wood, clay, or stone and live inside these substances.
Scallop is a common name that encompasses various species of marine bivalve mollusks in the taxonomic family Pectinidae, the scallops. However, the common name "scallop" is also sometimes applied to species in other closely related families within the superfamily Pectinoidea, which also includes the thorny oysters.
Venerida is an order of mostly saltwater but also some freshwater bivalve molluscs. This order includes many familiar groups such as many clams that are valued for food and a number of freshwater bivalves.
A bivalve shell is part of the body, the exoskeleton or shell, of a bivalve mollusk. In life, the shell of this class of mollusks is composed of two hinged parts or valves. Bivalves are very common in essentially all aquatic locales, including saltwater, brackish water, and freshwater. The shells of bivalves commonly wash up on beaches and along the edges of lakes, rivers, and streams. Bivalves by definition possess two shells or valves, a "right valve" and a "left valve", that are joined by a ligament. The two valves usually articulate with one another using structures known as "teeth" which are situated along the hinge line. In many bivalve shells, the two valves are symmetrical along the hinge line—when truly symmetrical, such an animal is said to be equivalved; if the valves vary from each other in size or shape, inequivalved. If symmetrical front-to-back, the valves are said to be equilateral, and are otherwise considered inequilateral.
Anabarella is a species of bilaterally-flattened monoplacophoran mollusc, with a morphological similarity to the rostroconchs. Its shell preserves evidence of three mineralogical textures on its outer surface: it is polygonal near the crest of the shell, subsequently changing to both spiny and stepwise. Its internal microstructure is calcitic and semi-nacreous. Its name reflects its provenance from Anabar, Siberia. It has been interpreted as ancestral to the rostroconchs, and has been aligned to the Helcionellidae.
Fordilla is an extinct genus of early bivalves, one of two genera in the extinct family Fordillidae. The genus is known solely from Early Cambrian fossils found in North America, Greenland, Europe, the Middle East, and Asia. The genus currently contains three described species, Fordilla germanica, Fordilla sibirica, and the type species Fordilla troyensis.
Rhynchonelliformea is a major subphylum and clade of brachiopods. It is roughly equivalent to the former class Articulata, which was used previously in brachiopod taxonomy up until the 1990s. These so-called articulated brachiopods have many anatomical differences relative to "inarticulate" brachiopods of the subphyla Linguliformea and Craniformea. Articulates have hard calcium carbonate shells with tongue-and-groove hinge articulations and separate sets of simple opening and closing muscles.
Astarte borealis, or the northern astarte, is a species of bivalve mollusc in the family Astartidae. It can be found along the Atlantic coast of North America, ranging from Greenland to Massachusetts.
Pojetaia is an extinct genus of early bivalves, one of two genera in the extinct family Fordillidae. The genus is known solely from Early to Middle Cambrian fossils found in North America, Greenland, Europe, North Africa, Asia, and Australia. The genus currently contains two accepted species, Pojetaia runnegari, the type species, and Pojetaia sarhroensis, though up to seven species have been proposed. The genera Buluniella, Jellia, and Oryzoconcha are all considered synonyms of Pojetaia.
Tellimya ferruginosa is a species of small marine bivalve mollusc in the family Lasaeidae. It is found on the eastern side of the Atlantic Ocean.
Fordillidae is an extinct family of early bivalves and one of two families in the extinct superfamily Fordilloidea. The family is known from fossils of early to middle Cambrian age found in North America, Greenland, Europe, the Middle East, Asia, and Australia. The family currently contains two genera, Fordilla and Pojetaia, each with up to three described species. Due to the size and age of the fossil specimens, Fordillidae species are included as part of the Turkish Small shelly fauna.
Camya is an extinct genus of early bivalve and is the only genus in the extinct family Camyidae. The genus is known solely from early Middle Cambrian fossils found in Europe. The genus currently contains a solitary accepted species, Camya asy.
Tuarangia is a Cambrian shelly fossil interpreted as an early bivalve, though alternative classifications have been proposed and its systematic position remains controversial. It is the only genus in the extinct family Tuarangiidae and order Tuarangiida. The genus is known solely from Middle to Late Cambrian fossils found in Europe and New Zealand. The genus currently contains two accepted species, Tuarangia gravgaerdensis and the type species Tuarangia paparua.
Concavodonta is an extinct genus of early bivalve in the extinct family Praenuculidae. The genus is one of three genera in the subfamily Concavodontinae. Concavodonta is known solely from late Ordovician, Caradoc epoch, fossils found in Europe and South America. The genus currently contains three accepted species, Concavodonta imbricata, Concavodonta ovalis and the type species Concavodonta ponderata.
Hemiconcavodonta is an extinct genus of bivalve in the extinct family Praenuculidae. The genus is one of three genera in the subfamily Concavodontinae. Hemiconcavodonta is known solely from late Ordovician, Caradoc epoch, fossils found in South America. The genus currently contains a single accepted species, Hemiconcavodonta minuta.
Praenuculinae is an extinct subfamily of prehistoric bivalves in the family Praenuculidae. Praenuculinae species lived from the middle Ordovician through the late Devonian. Praenuculinae fossils are found in Europe, Africa, North America and South America, and species are thought to have been stationary attached to substrate in shallow infaunal marine water environments where they formed shells of an aragonite composition. The subfamily Praenuculinae was named by Teresa M. Sánchez in 1999.
Cucullaea labiata is a species of saltwater clam or ark shell, a marine bivalve mollusk in the family Cucullaeidae.
A hinge ligament is a crucial part of the anatomical structure of a bivalve shell, i.e. the shell of a bivalve mollusk. The shell of a bivalve has two valves and these are joined by the ligament at the dorsal edge of the shell. The ligament is made of a strong, flexible and elastic, fibrous, proteinaceous material which is usually pale brown, dark brown or black in color.
The adductor muscles are the main muscular system in bivalve mollusks. In many parts of the world, when people eat scallops, the adductor muscles are the only part of the animal which is eaten. Adductor muscles leave noticeable scars or marks on the interior of the shell's valves. Those marks are often used by scientists who are in the process of identifying empty shells to determine their correct taxonomic placement.
Ostreoidea is a taxonomic superfamily of bivalve marine mollusc, sometimes simply identified as oysters, containing two families. The ostreoids are characterized in part by the presence of a well developed axial rod. Anal flaps are known to exist within the family Ostreidae but not within the more-primitive Gryphaeidae. The scar from the adductor muscle is simple, with a single, central scar. In the majority, the right valve is less convex than the left.
