The order Ostreida includes the true oysters. One superfamily (Ostreacea) and two families are recognised within it. The two families are Ostreidae, the true oysters, and Gryphaeidae, the foam oysters.
The Arcida is an extant order of bivalve molluscs. This order dates back to the lower Ordovician period. They are distinguished from related groups, such as the mussels, by having a straight hinge to the shells, and the adductor muscles being of equal size. The duplivincular ligament, taxodont dentition, and a shell microstructure consisting of the outer crossed lamellar and inner complex crossed lamellar layers are defining characters of this order.
The Pteriida are an order of large and medium-sized marine bivalve mollusks. It includes five families, among them the Pteriidae.
Rudists are a group of extinct box-, tube- or ring-shaped marine heterodont bivalves belonging to the order Hippuritida that arose during the Late Jurassic and became so diverse during the Cretaceous that they were major reef-building organisms in the Tethys Ocean, until their complete extinction at the close of the Cretaceous.
The Pteriomorphia comprise a subclass of saltwater clams, marine bivalve molluscs. It contains several major orders, including the Arcida, Ostreida, Pectinida, Limida, Mytilida, and Pteriida. It also contains some extinct and probably basal families, such as the Evyanidae, Colpomyidae, Bakevelliidae, Cassianellidae, and Lithiotidae.
Palaeoheterodonta is a subclass of bivalve molluscs. It contains the extant orders Unionida and Trigoniida. They are distinguished by having the two halves of the shell be of equal size and shape, but by having the hinge teeth be in a single row, rather than separated into two groups, as they are in the clams and cockles.
Heterodonta is a taxonomic subclass of saltwater clams, marine bivalve molluscs. This subclass includes the edible clams, the cockles and the Venus clams.
Trigoniidae is a taxonomic family of saltwater clams, marine bivalve mollusks in the superfamily Trigonioidea. There is only one living genus, Neotrigonia, but in the geological past this family was well represented, widespread and common. The shells of species in this family are morphologically unusual, with very elaborate hinge teeth, and the exterior of the shell is highly ornamented.
Mytilida is an order of marine bivalve molluscs, commonly known as true mussels. There is one extant superfamily, the Mytiloidea, with a single extant family, the Mytilidae.
Anomalodesmata is an order of saltwater clams, marine bivalve molluscs. This grouping was formerly recognised as a taxonomic subclass. It is called a superorder in the current World Register of Marine Species, despite having no orders, to parallel it with sister taxon Imparidentia, which does have orders.
The Pectinoidea are a superfamily of marine bivalve molluscs, including the scallops and spiny oysters.
Protobranchia is a subclass of bivalve molluscs. It contains the extant orders Nuculanida, Nuculida, and Solemyida.
Pectinida is a taxonomic order of large and medium-sized saltwater clams, marine bivalve molluscs, commonly known as scallops and their allies. It is believed that they began evolutionarily in the late Middle Ordovician epoch; many species, of course, are still extant.
Poromyoidea is a superfamily of molluscs. It used to contain only the family Poromyidae, but now it also contains Cetoconchidae Ridewood, 1903, as CetoconchaDall, 1886 was removed from Poromyidae and given its own family, according to the World Register of Marine Species.
Trigoniida is an order of medium-sized saltwater clams, marine bivalve molluscs. Within the fossil record the occurrence of this order is widespread, ranging from the Devonian Period to Recent.
In May 2010, a new taxonomy of the Bivalvia was published in the journal Malacologia. The 2010 taxonomy is known as the Taxonomy of the Bivalvia . The 2010 taxonomy was published as Nomenclator of Bivalve Families with a Classification of Bivalve Families. This was a revised system for classifying bivalve mollusks such as clams, oysters, scallops, mussels and so on. In compiling this new taxonomy, the authors used a variety of phylogenetic information including molecular analysis, anatomical analysis, shell morphology and shell microstructure, as well as bio-geographic, paleobiogeographical and stratigraphic information.
Mytiloidea are a superfamily of small to large saltwater mussels, marine bivalve molluscs in the order Mytilida.
Lucinida is a taxonomic order of saltwater clams, marine bivalve molluscs.
Carditida is an order of marine bivalve clams.
Carditoidea is a superfamily of marine bivalve clams.
