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Mollusks
Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The number of additional fossil species is estimated between 60,000 and 100,000, and the proportion of undescribed species is very high. Many taxa remain poorly studied. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat, as numerous groups are freshwater and even terrestrial species. The phylum is typically divided into 7 or 8 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known extant invertebrat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalopoda
A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles ( muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology. Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by ''Nautilus'' and ''Allonautilus''. In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been iden ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monoplacophora
Shell of Monoplacophora Monoplacophora , meaning "bearing one plate", is a polyphyletic class of molluscs with a cap-like shell, inhabiting deep sea environments. Extant representatives were not recognized as such until 1952; previously they were known only from the fossil record, and were thought to have become extinct 375 million years ago. Although the shell of many monoplacophorans is limpet-like in shape, they are not gastropods, nor do they have any close relation to gastropods. Definition Discussion about monoplacophorans is made difficult by the slippery definition of the taxon; some authors take it to refer to all non-gastropod molluscs with a single shell, or all single-shelled molluscs with serially repeated units; whereas other workers restrict the definition to cap-shaped forms, excluding spiral and other shapes of shell. The inclusion of the gastropod-like Bellerophontoidea within the group is also contentious. One attempt to resolve this confusion was to separ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helcionelloida
Helcionelloida is an extinct group of ancient molluscs (phylum Mollusca). These are the oldest known conchiferan molluscs, that is, they had a mineralised shell. Some members of this class were mistaken for Monoplacophorans. The class was erected by Peel in 1991. Anatomy These animals were torsion (gastropod), untorted and they had a coiled, cone-shaped shell. The majority of species were small (shells being about two millimeters in length and or diameter). Modern reconstructions depict them as resembling snails. The shells of some genera, particularly ''Yochelcionella'', also possessed a "Snorkel (anatomy), snorkel"-like opening which was most likely used for breathing. 2005 taxonomy The Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), taxonomy of the Gastropoda by Bouchet & Rocroi, 2005Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005. ''Classification and nomenclator of gastropod families''. Malacologia: International ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ruditapes Philippinarum
''Ruditapes philippinarum'', the Manila clam, is an edible species of saltwater clam in the family Veneridae, the Venus clams. Common names include Manila clam, Japanese littleneck clam, Japanese cockle, and Japanese carpet shell.Cohen, A.N. 2011''Venerupis philippinarum''.The Exotics Guide: Non-native Marine Species of the North American Pacific Coast. Center for Research on Aquatic Bioinvasions, Richmond, California, and San Francisco Estuary Institute, Oakland, California. Revised September 2011. In Japan, it is known as ''asari''. In Korea, it is known as ''bajirak''. The clam is commercially harvested, and is the second most important bivalvia, bivalve grown in aquaculture worldwide.Cordero, D., et alPopulation genetics of the Manila clam (Ruditapes philippinarum) introduced in North America and Europe.''Scientific Reports'' 7, Article number: 39745. 3 January 2017. Description The shell of ''Ruditapes philippinarum'' is elongate, oval, and sculptured with radiating ribs.Mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rostroconchia
The Rostroconchia is a class of extinct molluscs dating from the early Cambrian to the Late Permian. They were initially thought to be bivalves, but were later given their own class. They have a single shell in their larval stage, and the adult typically has a single, pseudo-bivalved shell enclosing the mantle and muscular foot. The anterior part of the shell probably pointed downward and had a gap from which the foot could probably emerge. Rostroconchs probably lived a sedentary semi- infaunal lifestyle. There were probably more than 1,000 species of members of this class. Approximately 3 dozen genera and an even greater number of species have been described. Generally, rostroconchs are small, less than two centimeters in length, but larger forms, found in United States Devonian limestones, can grow to a length of 15 cm. Morphology and lifestyle Externally, rostroconchs look much like bivalves and rostroconchs probably had an extendable muscular foot, indicated by a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dentalium (genus)
''Dentalium'' is a large genus of tooth shells or tusk shells, marine scaphopod molluscs in the family Dentaliidae. The genus contains 50 described species and about 50 extinct species.MolluscaBase eds. (2020). MolluscaBase. Dentalium Linnaeus, 1758. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=137886 on 2020-10-19 Etymology The scientific name of this genus comes from the Latin word ''dentis'', meaning ''tooth'', based on the tooth or tusk-shaped form of these molluscs. Description The mantle of ''Dentalium'' species is entirely within the shell. The foot extends from the larger end of the shell, and is used to burrow through the substrate. They position their head down in the substrate, with the apical end of the shell (at the rear of the animal's body) projecting up into the water. These molluscs live on seafloor sediment, feeding on microscopic organisms, detritus and foraminiferans. The shells are conical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scaphopoda
Scaphopoda (plural scaphopods , from Ancient Greek σκᾰ́φης ''skáphē'' "boat" and πούς ''poús'' "foot"), whose members are also known as tusk shells or tooth shells, are a class of shelled marine invertebrates belonging to the phylum Mollusca with worldwide distribution and are the only class of exclusively infaunal marine molluscs. Shells of species within this class range in length (with ''Fissidentalium metivieri'' as the longest). Members of the order Dentaliida tend to be larger than those of the order Gadilida. These molluscs live in soft substrates offshore (usually not intertidally). Because of this subtidal habitat and the small size of most species, many beachcombers are unfamiliar with them; their shells are not as common or as easily visible in the beach drift as the shells of sea snails and clams. Molecular data suggest that the scaphopods are a sister group to the cephalopods, although higher-level molluscan phylogeny remains unresolved. Cl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kimberella
''Kimberella'' is an extinct genus of marine bilaterian known only from rocks of the Ediacaran period. The slug-like organism fed by scratching the microbial surface on which it dwelt in a manner similar to the gastropods, although its affinity with this group is contentious. Specimens were first found in Australia's Ediacara Hills, but recent research has concentrated on the numerous finds near the White Sea in Russia, which cover an interval of time from . As with many Ediacara biota, fossils from this time, its evolutionary relationships to other organisms are hotly debated. Paleontologists initially classified ''Kimberella'' as a type of Cubozoan, but, since 1997, features of its anatomy and its association with scratch marks resembling those made by a radula have been interpreted as signs that it may have been a mollusc. Although some paleontologists dispute its classification as a mollusc, it is generally accepted as being at least a bilaterian. The classification of ''Ki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiplacophora
Multiplacophora is a stem-group of chitons with a number of plates arranged in 7 rows along the body. They date to at least the Upper Cambrian, but two lower Cambrian fossil 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 preserve ...s- '' Ocruranus'' and '' Trachyplax'' - may extend the range downwards. Families and genera * Family Hercolepadidae Dzik, 1986 ** Genus '' Hercolepas'' Aurivillius, 1892 ** Genus '' Protobalanus'' Hall and Clarke, 1888 * Family Strobilepidae Hoare and Mapes, 1995 ** Genus '' Aenigmatectus'' Hoare and Mapes, 1996 ** Genus '' Deltaplax'' Puchalski, Johnson, Kauffman and Eernisse, 2009 ** Genus '' Diadeloplax'' Hoare and Mapes, 1995 ** Genus '' Hannestheronia'' Vinther, Jell, Kampouris, Carney, Racicot & Briggs, 2012 ** Genus '' Polysacos'' Vendrasco, Wood an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Qaleruaqia
''Qaleruaqia'', known only from the Aftenstjernesø Formation, Lauge Koch Land, North Greenland is considered the earliest fossil aculifera Aculifera (older name: Amphineura) is a clade of molluscs incorporating those groups that have no conch or shell, that is, the Polyplacophora, Caudofoveata and Solenogastres. For a summary, see It is a sister group to the Conchifera. Monophyly ...n. The type species, ''Q. sodermanorum'', was named and described in 2020. References {{Taxonbar, from1=Q96400549 Monotypic prehistoric chiton genera Cambrian molluscs Fossil taxa described in 2020 Cambrian genus extinctions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acaenoplax
''Acaenoplax'' is an extinct worm-shaped mollusc known from the Coalbrookdale Formation of Herefordshire, England. It lived in the Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ... period. It was a couple of centimetres long and half a centimetre wide, and comprises serially repeated units with seven or eight shells, and rings of 'spines'. Some of its characters are reminiscent of the polychaete worms, and the character combinations do not place it obviously in the stem of any modern mollusc group, but although it was originally interpreted as a polychaete, this position is untenable for a number of reasons. Morphology The organism resembles a bristled worm, but bears a number of shells on its upper surface. The first shell is cap-like, whereas the others are saddl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conchifera
Conchifera is a subphylum of the phylum Mollusca, containing five extant classes: Monoplacophora, Cephalopoda, Gastropoda, Bivalvia, and Scaphopoda. Conchiferans can bear a single shell as in snails and ammonites, a single pair of shells as in clams, or lack a shell as in slugs and squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also .... The other subphylum is Aculifera, the members of which are shellless or have a row of several plates. Non-monoplacophoran conchiferans emerged within the once-widespread Monoplacophora. The only descendant which retains its ancestral shape is the Tryblidiida. The monophyly of Conchifera is supported by molecular phylogenetic analysis. The relationships among the members of Conchifera are disputed. A grouping of Scaphopoda and Bivalv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
