Trigoniida is an

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

of medium-sized saltwater

clam Clam is a common name for several kinds of bivalve mollusc. The word is often applied only to those that are deemed edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds. Clams h ...

s, marine

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

s. Within the

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

the occurrence of this order is widespread, ranging from the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

Period to

Recent The Holocene () is the current geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Qu ...

. The diagnostic feature for the order is the unique and complex

dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiology ...

of the shell, (i.e. the interior hinge teeth that articulate the two valves). The dentition is particularly elaborate within the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Trigoniidae. Bieler, Carter, & Coan (2010) included the following families and superfamilies in Trigoniida. Taxa marked with a † are extinct with the only extant family in the order being Trigoniidae. Trigoniida *† Beichuanioidea Liu & Gu, 1988 **† Beichuaniidae Liu & Gu, 1988 *† Megatrigonioidea Van Hoepen, 1929 **† Megatrigoniidae Van Hoepen, 1929 **† Iotrigoniidae Savelive, 1958 **† Rutitrigoniidae Van Hoepen, 1929 *† Myophorelloidea Kobayashi, 1954 **† Myophorellidae Kobayashi, 1954 **† Buchotrigoniidae Leanza, 1993 **† Laevitrigoniidae Savelive, 1958 **† Vaugoniidae Kobayashi, 1954 * Trigonioidea

Lamarck Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck (; ), was a French naturalist, biologist, academic, and soldier. He was an early proponent of the idea that biolo ...

, 1819 ** Trigoniidae

, 1819 **† Eoschizodidae Newell & Boyd, 1975 (syn: Curtonotidae) **† Groeberellidae Pérez, Reyes, & Danborenea 1995 **† Myophoriidae Bronn, 1849 (syn: Cytherodontidae, Costatoriidae, Gruenewaldiidae) **† Prosogyrotrigoniidae Kobayashi, 1954 **† Scaphellinidae Newell & Ciriacks, 1962 **† Schizodidae Newell & Boyd, 1975 **† Sinodoridae Pojeta & Zhang, 1984

References

Extant Devonian first appearances Prehistoric bivalves Bivalve orders {{paleo-bivalve-stub