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Mollusc Anatomy
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 invertebrate sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terreneuvian
The Terreneuvian is the lowermost and oldest Series (stratigraphy), series of the Cambrian geological System (stratigraphy), system. Its base is defined by the first appearance datum of the trace fossil ''Treptichnus pedum'' around million years ago. Its top is defined as the first appearance of trilobites in the stratigraphic record around million years ago. This series' name was formally accepted by the International Commission on Stratigraphy in 2007. The Fortunian Stage (stratigraphy), stage and presently unnamed Cambrian Cambrian Stage 2, Stage 2 are the stages within this series. The Terreneuvian corresponds to the pre-trilobite, trilobitic Cambrian. The name Terreneuvian is derived from ''Terre Neuve'', the French name for the island of Newfoundland (island), Newfoundland, Canada, where many rocks of this age are found, including the type section. GSSP The type locality (Global Boundary Stratotype Section and Point, GSSP) of the Terreneuvian is in Fortune Head, at the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthozanclus
''Orthrozanclus'' (from Greek + ( + ), "dawn scythe") is a genus of sea creatures known from two species, ''O. reburrus'' from the Middle Cambrian (~) Burgess shale and ''O. elongata'' from Early Cambrian (~) Maotianshan Shales. Animals in this genus were one to two centimeters long, with spikes protruding from their armored bodies. The placement of this genus into a specific family is not universally accepted. History of discovery Jean-Bernard Caron and Donald A. Jackson found a specimen in the Burgess Shale and in 2006 referred to it as "scleritomorph C" without a detailed description. In 2007 Caron and Simon Conway Morris published a description and named the fossil ''Orthrozanclus reburrus''. The genus name means "Dawn scythe" and derives from Greek, with the species name meaning "bristling hair" in Latin. The two known specimens of ''O. elongata'' were discovered from Maotianshan Shales, Maotianshan Shale in 2015 and 2016 and formally described the following year. Descrip ... [...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] |
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] |
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] |
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] |
Caudofoveata
Caudofoveata is a small class within the phylum Mollusca, also known as Chaetodermomorpha. The class is often combined with Solenogastres and termed Aplacophora, but some studies have cast doubt on the monophyly of this group. Anatomy Caudofoveata are worm-like molluscs ranging 0.02–10 cm in size, but one species, Chaetoderma felderi, can reach 36.5 cm. The foot is completely absent, and instead of a shell their mantle is covered in calcareous spines called sclerites. Ecology Caudofoveates live by burrowing through soft sediment, and feed by lying vertically in the sediment with just the mouthparts exposed and taking in passing organic detritus. During sexual reproduction, the female produces eggs which are fertilized and brooded, and then the larvae swim freely. Diet Caudofoveates are deposit feeders, or more selective detritivores or predators of foraminifera Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are unicellular organism, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solenogastres
The Solenogastres (less often referred to as Neomeniomorpha), common name, commonly known as solenogasters, are a class of small, worm-like, shell-less Mollusca, molluscs (Aplacophora), the other class being the Caudofoveata (Chaetodermomorpha).MolluscaBase eds. (2021). MolluscaBase. Solenogastres. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=2094 on 2021-04-14 Some recent literature and recent molecular evidence, indicates that the Aplacophora may be polyphyletic, and therefore some taxonomists may divide Solenogastres and Caudofoveata into separate classes. Morphology In contrast to many other mollusc classes, aplacophorans have no shell, and are instead covered by aragonite, aragonitic sclerites (calcareous wikt:spicule, spicules), which can be solid or hollow. These spicules can be arranged perpendicular to one another within the cuticle to form a skeleton, stick up to form a palisade, or can lie flat against th ... [...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] |
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] |
