A univalve, gasteropods, or even gastropod, come a big & virtually all successful class of mollusks, with 60,000-75,000 extant species known, comprising the snails and slugs as well as a vast total of marine & freshwater coinage. It occasionally have a easily-chiseled head with two or quartet centripetal tentacles, and the ventral foot, which gives the two their title (Greek gaster, stomach, and poda, feet). It is distinguished by torsion, a run in which the person coils to of these side when you took development.

Virtually all members have a shell, which is in a single piece & often coiled or even spiralled that ordinarily opens on a correct hand side (every bit viewed sustaining the plate apex pointing upward). Many metal money own an operculum that operates as a trapdoor to close the eggshell. This is ordinarily processed of the horny poop, however around occasionally shellfish these are chalky. Around a bit of members, a slugs, a eggshell is reduced or even scatty, & a person is streamlined thus its torsion is comparatively invisible.

When the right-known univalve come terrestrial, further than deuce thirds of a lot coinage sleep in a marine environment. Marine univalve include herbivores, detritus feeders, carnivores and a few ciliary feeders, where a radula is reduced or abstracted. the radula is normally adapted to the food that a mintage chow. A simplest univalve come a limpets and abalones, both herbivores that have their firm radulas to rasp at seaweeds on rocks. Several marine univalve come burrowers & stand siphons or even tubes that extend from either a mantle and sometimes a scale. These work when snorkels, enabling the fauna to prove my point to draw within a fluids todays containing oxygen and food into their bodies. the siphons come besides wont to detect prey from either a few feet away. These univalve breathe by having gills, but a select few freshwater coinage & nearly entirely terrestric metal money use developed lungs. When a univalve by using lungs entirely belong to 1 class action (Pulmonata), a univalve by using gills come paraphyletic.

Sea slugs come typically flashily coloured, either as a warning in case it is poisonous or even to camouflage them on the corals and seaweeds on which numerous of the mintage come discovered. Their gills come typically within the form of feathery plumes in their backs which produce to their more title, nudibranchs. Sea slug using smooth or even wartlike backs develop there is no seeable gill mechanisms & respiration can choose place directly through the skin. Two or three of the sea slugs come herbivores & a bit of come carnivores. Numerous own distinct dietetic preferences & regularly occur around association sustaining certain coinage.

Geological history

A 1st univalve were alone marine, sustaining a earliest representatives of the class action appearing in the Late Cambrian (Chippewaella, Strepsodiscus). Early Cambrian forms like Helcionella and Scenella are no hanker considered univalve, & a petite coiled Aldanella of earliest Cambrian time is probably non possibly the mollusk. Per Ordovician period the univalve were the varied class action present around the range of aquatic home ground. Normally, fossil gastropods from a rocks of the early Palaeozoic era are as well badly preserved for exact identification. Fossil univalve come less green when you took a Palaeozoic era than bivalves.

Virtually all of the univalve of the Palaeozoic era belong to primitive groups, two or three of which however hold out in todays world. Per Carboniferous period many of a shapes i personally look at withwithin residing univalve may be matched in the fossil record, however despite these similarities in appearance the majority one older forms are non directly related residing forms. It was in a period of the Mesozoic era that the root of several of the residing univalve evolved.

One of a earliest known terrestrial (land-living) univalve is Maturipupa which is obtained in the Coal Measures of the Carboniferous period within Europe, but relatives of a modern land snails come uncommon prior to the Cretaceous period when a familiar Helix first appeared.

Within rocks of the Mesozoic era univalve come slightly additional park when fossils, their casing typically swell preserved. Their fossils occur inside beds which were deposited inside two freshwater & marine environments. A "Purbeck Marble" of the Jurassic period and a "Sussex Marble" of the early Cretaceous cycle which each occur around southern England are limestones containing the tightly packed remains of the pool snail Viviparus.

Rocks of the Cenozoic era yield very prominent numerous univalve fossils, many one fossils existence closely related modern residing forms. A diversity of a univalve increased markedly at the beginning of this era, along therewith of the pelecypod.

Certainside trail-such as markings preserved in ancient sedimentary rocks come thought to use at times been mass produced by univalve crawling above a easy mud & sand. Although these trails come of debatable origin, a few of a two run resemble the trails manufactured by residing univalve in todays world.

Univalve fossils will another time become confused by having ammonites or more shelled cephalopods. An case of this is Bellerophon from the limestones of the Carboniferous period in Europe which can be mistaken for the cephalopod mollusk.

Univalve come one of a groups that record a changes around animal from either a advance & retreat of a Ice Sheets when you took the Pleistocene epoch.

Taxonomy

A taxonomy of a Gastropoda is under constant revision, but supplementary & other the old taxonomy is existence abandoned. However terms when "opisthobranch" & "prosobranch" come however existence utilized inside the descriptive way (& there are no yearn when taxonomic group). In the way, you potty speak of a taxonomical jungle after i last down to the moo taxonomical levels. A taxonomy of the Gastropoda may be different from either creator to creator. However by having the arrival of DNA-sequencing, a further definite taxonomy of the higher taxonomical levels is to become potential in the nigh new.

Till recently there were quaternion subclasses. : Prosobranchia (gills in front of the heart). Opisthobranchia (gills to a right & behind the heart). Gymnomorpha (no plate) Pulmonata (with lungs instead of gills)

Based on data from a newly insights (Ponder & Lindberg, 1997), the taxonomy of the Gastropoda should be rewritten. Based on data from these authors, taxa potty sole become valid after defined within cladistic terms. In their opinion, the classification using the rigid placed of hierarchical levels is not necessary or suitable. Their thorough morphological analysis led to several cladistic trees, producing a single cladistic tree. A authors so provided list for the clades in this tree. Integrating their findings into the working taxonomy will be a admittedly challenge in the coming years. Now, these are impossible to give the classification of the Gastropoda that has uniform ranks & as well reflects todays usage.

Next occurs as projected classification, down to the level of superfamily.

Class Gastropoda ( Cuvier, 1797)

Incertæ sedis Order Bellerophontida (fossil) Order Mimospirina (fossil) Subclass Eogastropoda (Ponder & Lindberg, 1996) (earlier: Prosobranchia) Order Euomphalida first state Koninck 1881 (fossil) Superfamily Macluritoidea Superfamily Euomphaloidea Superfamily Platyceratoidea Order Patellogastropoda Lindberg,1986 (avowedly limpets) Suborder Patellina Van Ihering,1876 Superfamily Patelloidea Rafinesque, 1815 Suborder Nacellina Lindberg, 1988 Superfamily Acmaeoidea Carpenter, 1857 Superfamily Nacelloidea Thiele, 1891 Suborder Lepetopsina McLean, 1990 Superfamily Lepetopsoidea McLean, 1990

Subclass Orthogastropoda Ponder & Lindberg, 1996 (earlier Prosobranchia, Opisthobranchia)

Incertæ sedis Order Murchisoniina Cox & Knight, 1960 (fossil) Superfamily Murchisonioidea Koken, 1889 Superfamily Loxonematoidea Koken, 1889 Superfamily Lophospiroidea Wenz, 1938 Superfamily Straparollinoidea Grade Subulitoidea Lindström, 1884

Superorder Cocculiniformia Haszprunar, 1987 Superfamily Cocculinoidea Dall, 1882 Superfamily Lepetelloidea Dall, 1882 (deep sea limpets)

Superorder ‘Hot Vent Taxa' Ponder & Lindberg, 1997 Order Neomphaloida Sitnikova & Starobogatov, 1983 Superfamily Neomphaloidea McLean, 1981 (hydrothermal vents limpets) Superfamily Peltospiroidea McLean, 1989

Superorder Vetigastropoda Salvini-Plawen, 1989 (limpets) Superfamily Fissurelloidea Flemming, 1822 (keyhole limpets) Superfamily Haliotoidea Rafinesque, 1815 (abalones) Superfamily Lepetodriloidea McLean, 1988 (hydrothermal vent limpets) Superfamily Pleurotomarioidea Swainson, 1840 (slit layers) Superfamily Seguenzioidea Verrill, 1884 Superfamily Trochoidea Rafinesque, 1815 (top shells)

Superorder Neritaemorphi Koken, 1896 Order Cyrtoneritomorpha (fossil) Order Neritopsina Cox & Knight, 1960 Superfamily Neritoidea Lamarck, 1809

Superorder Caenogastropoda Cox, 1960 Order Architaenioglossa Haller, 1890 Superfamily Ampullarioidea J.E. Gray, 1824 Superfamily Cyclophoroidea J.E. Gray, 1847 (terrestrials) Order Sorbeoconcha Ponder & Lindberg, 1997 Suborder Discopoda P. Fischer, 1884 Superfamily Campaniloidea Douvillé, 1904 Superfamily Cerithioidea Férussac, 1822 Suborder Hypsogastropoda Ponder & Lindberg, 1997 Infraorder Littorinimorpha Golikov & Starobogatov, 1975 Superfamily Calyptraeoidea Lamarck, 1809 Superfamily Capuloidea J. Fleming, 1822 Superfamily Carinarioidea Blainville, 1818 Superfamily Cingulopsoidea Fretter & Patil, 1958 Superfamily Cypraeoidea Rafinesque, 1815 (cowries) Superfamily Ficoidea Meek, 1864 Superfamily Laubierinoidea Warén & Bouchet, 1990 Superfamily Littorinoidea (Youngsters), 1834 (periwinkles) Superfamily Naticoidea Forbes, 1838 (moonshell) Superfamily Rissooidea J.E. Gray, 1847 (Risso shells) (includes genus oncomelania, schistosomiasis transmission vector) Superfamily Stromboidea Rafinesque, 1815 (true conchs) Superfamily Tonnoidea Suter, 1913 Superfamily Trivioidea Troschel, 1863 Superfamily Vanikoroidea J.E. Gray, 1840 Superfamily Velutinoidea J.E. Gray, 1840 Superfamily Vermetoidea Rafinesque, 1815 (worm shells) Superfamily Xenophoroidea Troschel, 1852 (host layers) Infraorder Ptenoglossa J.E. Gray, 1853 Superfamily Eulimoidea Philippi, 1853 Superfamily Janthinoidea Lamarck, 1812 Superfamily Triphoroidea J.E. Gray, 1847 Infraorder Neogastropoda Thiele, 1929 Superfamily Buccinoidea (whelks, false tritions) Superfamily Cancellarioidea Forbes & Hanley, 1851 Superfamily Conoidea Rafinesque, 1815 Superfamily Muricoidea Rafinesque, 1815

Superorder Heterobranchia J.E. Gray, 1840 Order Heterostropha P. Fischer, 1885 Superfamily Architectonicoidea J.E. Gray, 1840 Superfamily Nerineoidea Zittel, 1873 (fossil) Superfamily Omalogyroidea G.O. Sars, 1878 Superfamily Pyramidelloidea J.E. Gray, 1840 Superfamily Rissoelloidea J.E. Gray, 1850 Superfamily Valvatoidea J.E. Gray, 1840 Order Opisthobranchia Milne-Edwards, 1848 Suborder Cephalaspidea P. Fischer, 1883 Superfamily Acteonoidea D'Orbigny, 1835 Superfamily Bulloidea Lamarck, 1801 Superfamily Cylindrobulloidea Thiele, 1931 (has to be involved in the Sacoglossa) Superfamily Diaphanoidea Odhner, 1914 Superfamily Haminoeoidea Pilsbry, 1895 Superfamily Philinoidea J.E. Gray, 1850 Superfamily Ringiculoidea Philippi, 1853 Suborder Sacoglossa Von Ihering, 1876 Superfamily Oxynooidea H. & A. Adams, 1854 Suborder Anaspidea P. Fischer, 1883 (sea hares) Superfamily Akeroidea Pilsbry, 1893 Superfamily Aplysioidea Lamarck, 1809 Suborder Notaspidea P. Fischer, 1883 Superfamily Tylodinoidea J.E. Gray, 1847 Superfamily Pleurobranchoidea Férussac, 1822 Suborder Thecosomata Blainville, 1824 (sea butterflies) Infraorder Euthecosomata Superfamily Limacinoidea Superfamily Cavolinioidea Infraorder Pseudothecosomata Superfamily Peraclidoidea Superfamily Cymbulioidea Suborder Gymnosomata Blainville, 1824 (sea angels) Family Clionidae Rafinesque, 1815 Family Cliopsidae Costa, 1873 Family Hydromylidae Pruvot-Fol, 1942 Family Laginiopsidae Pruvot-Fol, 1922 Family Notobranchaeidae Pelseneer, 1886 Family Pneumodermatidae Latreille, 1825 Family Thliptodontidae Kwietniewski, 1910

Suborder Nudibranchia Blainville, 1814 (sea slug) Infraorder Anthobranchia Férussac, 1819 Superfamily Doridoidea Rafinesque, 1815 Superfamily Doridoxoidea Bergh, 1900 Superfamily Onchidoridoidea Alder & Hancock, 1845 Superfamily Polyceroidea Alder & Hancock, 1845 Infraorder Cladobranchia Willan & Morton, 1984 Superfamily Dendronotoidea Allman, 1845 Superfamily Arminoidea Rafinesque, 1814 Superfamily Metarminoidea Odhner inside Franc, 1968 Superfamily Aeolidioidea J.E. Gray, 1827 Order Pulmonata Cuvier in Blainville, 1814 (pulmonates) Suborder Systellommatophora Pilsbry, 1948 Superfamily Onchidioidea Rafinesque, 1815 Superfamily Otinoidea H. & A. Adams, 1855 Superfamily Rathouisioidea Sarasin, 1889 Suborder Basommatophora Keferstearound in Bronn, 1864 (freshwater pulmonates, pool snails) Superfamily Acroloxoidea Thiele, 1931 Superfamily Amphiboloidea J.E. Gray, 1840 Superfamily Chilinoidea H. & A. Adams, 1855 Superfamily Glacidorboidea Ponder, 1986 Superfamily Lymnaeoidea Rafinesque, 1815 Superfamily Planorboidea Rafinesque, 1815 Superfamily Siphonarioidea J.E. Gray, 1840 Suborder Eupulmonata Haszprunar & Huber, 1990 Infraorder Acteophila Dall, 1885 (= formerly Archaeopulmonata) Superfamily Melampoidea Stimpson, 1851 Infraorder Trimusculiformes Minichev & Starobogatov, 1975 Superfamily Trimusculoidea Aught, 1959 Infraorder StylommatophorThe A. Schmidt, 1856 (land snails) Subinfraorder Orthurethra Superfamily Achatinelloidea Gulick, 1873 Superfamily Cochlicopoidea Pilsbry, 1900 Superfamily Partuloidea Pilsbry, 1900 Superfamily Pupilloidea Turton, 1831 Subinfraorder Sigmurethra Superfamily Acavoidea Pilsbry, 1895 Superfamily Achatinoidea Swainson, 1840 Superfamily Aillyoidea Baker, 1960 Superfamily Arionoidea J.E. Gray in Turnton, 1840 Superfamily Buliminoidea Clessin, 1879 Superfamily Camaenoidea Pilsbry, 1895 Superfamily Clausilioidea Mörch, 1864 Superfamily Dyakioidea Gude & Woodward, 1921 Superfamily Gastrodontoidea Tryon, 1866 Superfamily Helicoidea Rafinesque, 1815 Superfamily Helixarionoidea Bourguignat, 1877 Superfamily Limacoidea Rafinesque, 1815 Superfamily Oleacinoidea H. & A. Adams, 1855 Superfamily Orthalicoidea Albers-Martens, 1860 Superfamily Plectopylidoidea Moellendorf, 1900 Superfamily Polygyroidea Pilsbry, 1894 Superfamily Punctoidea Morse, 1864 Superfamily Rhytidoidea Pilsbry, 1893 Superfamily Sagdidoidera Pilsbry, 1895 Superfamily Staffordioidea Thiele, 1931 Superfamily Streptaxoidea J.E. Gray, 1806 Superfamily Strophocheiloidea Thiele, 1926 Superfamily Trigonochlamydoidea Hese, 1882 Superfamily Zonitoidea Mörch, 1864 ? Superfamily Athoracophoroidea P. Fischer, 1883 (= Tracheopulmonata) ? Superfamily Succineoidea Beck, 1837 (= Heterurethra)

More extant classes of the Mollusca come Bivalvia, Scaphopoda, Aplacophora, Polyplacophora, Monoplacophora and Cephalopoda.

Reference
Paul Jeffery. Suprageneric classification of class GASTROPODA. A Natural History Museum, London, 2001 Ponder & Lindberg, Towards a phylogeny of gastropod molluscs; an analysis using morphological characters. Zoological Journal of the Linnean Society, 119 83-2651; 1997