|
Arcida
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. Seven families are currently recognised within the order, including the well-known ark clams or ark shells in the family Arcidae. Taxonomy The order Arcida, as the suborder Arcacea, is included in the order Taxodonta by R.C. Moore, 1952,R.C, Moore, Pelecypods, Ch 10, Inverrtebrate Fossils, Moore, Lalicker, and Fischer. McGraw-Hill, 1952. characterised by simple hinge-line dentition consisting of small, numerous, similar hinge teeth, separate mantle lobes, poorly developed siphons, and filibranch gills. In 2010, Bieler, Carter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ark Clam
Ark clam is the common name for a family of small to large-sized saltwater clams or marine bivalve molluscs in the family Arcidae. Ark clams vary both in shape and size. They number about 200 species worldwide. The shells of ark clams are often white or cream, but in some species, the shell is striped with, tinted with, or completely colored, a rich brown. In life the shell of most species has a top shell layer that is thick brown periostracum affixed to the harder calcareous part of the shell. In some species such as '' Barbatia'', this outer horny covering is tufted at the end of the shell into something that resembles a beard, hence the name ''Barbatia'' or bearded one. The group is known as "ark shells" because species such as '' Arca'' have a large flat area between the umbones which, in an undamaged shell, somewhat resembles a deck, with the rest of the shell perhaps illustrating an ancient wooden boat such as Noah's ark is thought to have been. All ark shells have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anadara
''Anadara'' is a genus of saltwater bivalves, ark clams, in the family Arcidae. It is also called ''Scapharca''. This genus is known in the fossil record from the Cretaceous period to the Quaternary period (age range: 140.2 to 0.0 million years ago). These fossils have been found all over the world. Species The following species are recognised in the genus ''Anadara'': * '' Anadara adamsi'' * '' Anadara aequatorialis'' * '' Anadara aethiopica'' * ''Anadara aliena'' * ''Anadara ambigua'' * ''Anadara amicula'' * ''Anadara angicostata'' * ''Anadara antiquata'' (Linnaeus, 1758) * ''Anadara auriculata'' Lamarck * ''Anadara axelolssoni'' * ''Anadara bataviensis'' * ''Anadara biangulata'' * ''Anadara bifrons'' * ''Anadara bonplandiana'' * ''Anadara brasiliana'' (Lamarck, 1819) - incongruous ark * ''Anadara broughtonii'' ( Schrenck, 1867) * ''Anadara camerunensis'' * ''Anadara cepoides'' * '' Anadara chemnitzii'' (Philippi, 1851) - Chemnitz ark, triangular ark * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taxodont
Hinge teeth are part of the anatomical structure of the inner surface of a bivalve shell, i.e. the shell of a bivalve mollusk. Bivalves by definition have two valves, which are joined together by a strong and flexible ligament situated on the hinge line at the dorsal edge of the shell. In life, the shell needs to be able to open slightly to allow the foot and siphons to protrude, and then close again, without the valves moving out of alignment with one another. To make this possible, in most cases the two valves are articulated using an arrangement of structures known as hinge teeth (often referred to collectively as the "dentition"). Like the ligament, the hinge teeth are also situated along the hinge line of the shell, in most cases. In most families of bivalves, the two valves of the shell are almost perfectly symmetrical with one another along the hinge line, although the placement and shape of the teeth may differ slightly in the left valve and right valve in order for the tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pteriomorphia
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. This subclass of molluscs has lamellibranch gills, and is epibenthic. Some attach to the substrate using a byssus. The foot is reduced. The mantle margins are not fused. Gills are usually large and assist in feeding. This group includes the well known mussels, scallops, pen shells, and oysters. It also includes the only members of the class bivalvia to have rudimentary eyes. Photoreceptors Pteriomorphian bivalves possess five types of photoreceptors, each evolving independently and each associated with different clades within Pteriomorphia. There are cap eyespots, pigmented cups, compound eyes, concave mirror eyes, and invaginated e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taxodonta
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. They include 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. The shipworms bore into wood, clay, or stone and live inside these substances. The shell of a bivalve is composed of calcium c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
