Mesogastropoda was for many years a traditional

taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...

group of

snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...

s, 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 ...

. The order was composed mostly of sea snails, but it also included some land snails and freshwater snails, all of which were

prosobranch Prosobranchia was a large Taxonomy (biology), taxonomic Class (biology), subclass of sea snails, land snails and freshwater snails. This taxon of gastropods dates back to the 1920s. It has however been proven to be polyphyly, polyphyletic (consis ...

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk 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 ...

s. This order was introduced by J. Thiele in his work from 1921, it and was used for many decades subsequently. Recent research in

malacology Malacology, from Ancient Greek μαλακός (''malakós''), meaning "soft", and λόγος (''lógos''), meaning "study", is the branch of invertebrate zoology that deals with the study of the Mollusca (molluscs or mollusks), the second-largest ...

however has made it clear that ''Mesogastropoda'' was not a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

, and because of that, the

is no longer included in modern classifications. Nonetheless, most of the standard texts and

field guide A field guide is a book designed to help the reader identify wildlife (flora or fauna or funga) or other objects of natural occurrence (e.g. rocks and minerals). It is generally designed to be brought into the " field" or local area where suc ...

s on mollusks date from the time period when this classification was still current, and therefore references to mesogastropods or Mesogastropoda are frequently encountered. The lower taxa that were traditionally contained in Mesogastropoda are now mostly placed in the superorder

Caenogastropoda Caenogastropoda is a taxonomic subclass of molluscs in the class Gastropoda. It is a large diverse group which are mostly sea snails and other marine gastropod mollusks, but also includes some freshwater snails and some land snails. The subcla ...

. A more detailed account of the taxonomy is given in the articles on

Gastropoda Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

and

Archaeogastropoda Archaeogastropoda (also known as Aspidobranchia) was a taxonomic order of snails used in older classifications of gastropods, i.e. snails and slugs. Archeogastropoda are primarily marine prosobranch gastropod mollusks, mainly herbivores, typica ...

, and a recent taxonomy is laid out in

Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005) The taxonomy of the Gastropoda as it was revised in 2005 by Philippe Bouchet and Jean-Pierre Rocroi is a system for the scientific classification of gastropod mollusks (Gastropods are a taxonomic class of animals which consists of snails and sl ...

Description

There are about 30,000 species that were included in this taxon. Most of them are to be found in the sea, but there are also numerous species in freshwater and even a few occur on land. Their shells have no mother-of-pearl or

nacre Nacre ( , ), also known as mother-of-pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer. It is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre is ...

. Most of these snails are

herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...

, but a few are

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s or

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

s. The

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...

has seven denticles (or small teeth), which are sometimes reduced. The Mesogastropoda are, in many ways, more developed than the

. Through torsion of the intestinal mass and a spiral movement of the body, the

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

, the

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

and the osphradium (which means sensory receptor, or olfactory organ) have disappeared on the right side. These organs exist only on the left side of the animal. The heart consists of only one atrium and one ventricle. The

nervous system In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...

is also more developed than in the Archeogastropods. The

ganglia A ganglion (: ganglia) is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system, this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system, there a ...

are connected with different organs through nerve pathways. In the Mesogastropoda, the excretory and the reproductive ducts are separated (in contrast with the most primitive prosobranchs). Many members produce egg capsules, containing one to more than 1,000 eggs.

Taxonomy

Here follows the taxonomy of the Mesogastropoda (according to the

ITIS The Integrated Taxonomic Information System (ITIS) is an American partnership of federal agencies designed to provide consistent and reliable information on the taxonomy of biological species. ITIS was originally formed in 1996 as an interagenc ...

) (which is no longer considered valid). The next taxonomy that was used was that of to Ponder & Lindberg, 1997. The current prevailing system of taxonomy is that of Bouchet & Rocroi, 2005.

Families

* Abyssochrysidae *

Aciculidae The Aciculidae are a family (biology), family of small land snails that have operculum (gastropod), opercula (an operculum is a little door that closes the shell when the animal retracts into it). In other words, Aciculidae are Terrestrial mollus ...

Aporrhaidae Aporrhaidae is a family of sea snails commonly called the "pelican's foot snails." The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005. ''Classif ...

Mörch, 1852 * Asterophilidae * Chondropomidae * Choristeidae (the original name Choristidae was a name to be emended to Choristeidae by the ICZN to remove homonymy with

Choristidae The Choristidae are a small (only eight species in three genera) family of scorpionflies known only from Australia. Their larvae are found in moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, ...

, a family of scorpionflies) *

Cingulopsidae Cingulopsidae is a family (biology), family of sea snails, marine (ocean), marine gastropod molluscs in the clade Littorinimorpha. According to Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), taxonomy of the Gastropoda by Bouchet & Rocroi ( ...

Cochlostomatidae Cochlostomatinae are a family of small land snails which have Operculum (gastropod), opercula and gills. These are Terrestrial molluscs, terrestrial gastropod mollusks in the superfamily Cyclophoroidea.Bouchet, P. (2015). Cochlostomatidae Kobelt, ...

* Diastomidae Cossman, 1895 * Fossaridae Trachel, 1861 *

Hydrococcidae Hydrococcidae is a family of small sea snails, marine gastropod molluscs in the clade Littorinimorpha Littorinimorpha is a large order of snails, gastropods, consisting primarily of sea snails ( marine species), but also including some fresh ...

Iravadiidae Iravadiidae is a family of small sea snails, marine gastropod molluscs in the superfamily Truncatelloidea and the clade Littorinimorpha Littorinimorpha is a large order of snails, gastropods, consisting primarily of sea snails ( marine speci ...

* Lacunidae Gill, 1871 *

Littorinidae The Littorinidae are a taxonomic family of over 200 species of sea snails, marine gastropod molluscs in the clade Littorinimorpha, commonly known as periwinkles and found worldwide. Names In English-speaking countries, gastropod molluscs from ...

Gray, 1840 *

Melanopsidae Melanopsidae, common name melanopsids, is a family of freshwater gastropods in the clade Sorbeoconcha. Species in this family are native to southern and eastern Europe, northern Africa, parts of the Middle East, New Zealand, and freshwater stre ...

* Micromelaniidae *

Omalaxidae †Omalaxidae is an extinct family of sea snails, marine gastropod molluscs in the clade Littorinimorpha Littorinimorpha is a large order of snails, gastropods, consisting primarily of sea snails ( marine species), but also including some fr ...

* Paedophoropodidae * Pilidae *

Pomatiopsidae Pomatiopsidae is a family of small, mainly freshwater snails, (some also occur in other habitats) that have gills and an operculum, aquatic gastropod mollusks in the superfamily Truncatelloidea (according to the taxonomy of the Gastropoda b ...

* Pseudosacculidae *

Stenothyridae Stenothyridae is a family (biology), family of small freshwater snails, snails with gills and an operculum (gastropod), operculum, Aquatic animal, aquatic gastropod molluscs in the superfamily Truncatelloidea. This family has no subfamilies. Di ...

* Stiliferidae *

Struthiolariidae Struthiolariidae is a family (biology), family of small to medium-sized sea snails, marine (ocean), marine gastropod molluscs in the superfamilia, superfamily Stromboidea.Bouchet, P.; Rosenberg, G. (2014). Struthiolariidae Gabb, 1868. Accessed th ...

* Syrnolopsidae * Trachysmidae * Trochaclisidae * Superfamily

Cyclophoroidea Cyclophoroidea is a superfamily of land snails with an operculum, terrestrial gastropods within the order Architaenioglossa, that belongs to the subclass Caenogastropoda.Bouchet, P.; Rosenberg, G.; Gofas, S. (2015). Cyclophoroidea Gray, 1847. ...

* Superfamily

Viviparoidea Viviparoidea is a taxonomic superfamily of freshwater snails, aquatic gastropod mollusks within the informal group Architaenioglossa, which belongs to the clade Caenogastropoda. The following two families have been recognized in the taxonomy o ...

References

* Thiele, J., 1929–1935. ''Handbuch der Systematischen Weichtierkunde''. 2 vols. 1154 p., 584 figs

External links

* {{Authority control Obsolete gastropod taxa