Semi-slugs, also spelled semislugs, are land gastropods whose shells are too small for them to retract into, but not quite

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

. The shell of some semi-slugs may not be easily visible on casual inspection, because the shell may be covered over with the mantle. This is a type of gastropod that is intermediate between a slug (without an external shell) and a land snail (with a large enough shell to retract completely into). There exist a number of gastropod families that have semi-slugs species.Breure A. S. H. (2010). "The rediscovery of a semi-slug: ''Coloniconcha prima'' Pilsbry, 1933 (Gastropoda, Pleurodontidae) from Hispaniola". '' Basteria'' 74(4-6): 78-86. There exist about 1,000 species of semi-slugs in comparison to about only 500 species of slugs.Burton D. W. (1982). "How to be sluggish". ''

Tuatara Tuatara (''Sphenodon punctatus'') are reptiles endemic to New Zealand. Despite their close resemblance to lizards, they are part of a distinct lineage, the order Rhynchocephalia. The name ''tuatara'' is derived from the Māori language and ...

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HTM

Examples

Semi-slugs have a worldwide distribution and have evolved in several families; genera include: *

Palearctic The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa. The realm consists of several bioregions: the Euro-Si ...

and

Nearctic The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface. The Nearctic realm covers most of North America, including Greenland, Central Florida, and the highlands of Mexico. The parts of North America ...

** family Parmacellidae: ''

Cryptella ''Cryptella'' is a genus of small-shelled slugs in the family Parmacellidae. Species Species in the genus ''Cryptella'' include: * ''Cryptella alegranzae'' Hutterer & Groh, 1991

'' ** family

Vitrinidae Vitrinidae is a family of small, air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Limacoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). MolluscaBase eds. (2021). MolluscaBas ...

: ''

Eucobresia ''Eucobresia'' is a genus of air-breathing land snails or semi-slugs, terrestrial pulmonate gastropod mollusks in the family Vitrinidae, the glass snails. Species Species within the genus ''Eucobresia'' include: * ''Eucobresia diaphana'' (D ...

, Semilimax, Vitrina,

Vitrinobrachium ''Vitrinobrachium'' is a genus of gastropods belonging to the family Vitrinidae Vitrinidae is a family of small, air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Limacoidea (according to the taxonomy o ...

'' * Asia - Pacific ** family Ariophantidae: ''

Parmarion ''Parmarion'' is a genus of air-breathing land semi-slugs, terrestrial pulmonate gastropod mollusks in the family Ariophantidae. ''Parmarion'' is the type genus of the Parmarioninae, which is a synonym of Ostracolethinae. Species of snails wit ...

'', '' Ratnadvipia, Varadia'' ** family

Helicarionidae Helicarionidae is a family of air-breathing land snails or semi-slugs, terrestrial pulmonate gastropod mollusks in the superfamily Helicarionoidea. Distribution The distribution of Helicarionidae includes the eastern Palearctic, Malagasy, ...

: '' Attenborougharion'', '' Helicarion'', ''

Howearion ''Howearion'' is a genus of two species of helicarionid semislugs that are endemic to Australia’s Lord Howe Island in the Tasman Sea. Species * ''Howearion belli'' Iredale, 1944 – beautiful semislug * ''Howearion hilli ''Howeario ...

'', ''

Ibycus Ibycus (; grc-gre, Ἴβυκος; ) was an Ancient Greek lyric poet, a citizen of Rhegium in Magna Graecia, probably active at Samos during the reign of the tyrant Polycrates and numbered by the scholars of Hellenistic Alexandria in the canon ...

'', ''

Parmellops ''Parmellops'' is a genus of two species of semislugs that are endemic to Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), A ...

'', '' Ubiquitarion'' ** Semi-slugs also exist but are exceptional in the

Camaenidae Camaenidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Helicoidea, the typical snails and their allies. This is one of the most diverse families in the clade Stylommatophora. Thes ...

. *

Neotropics The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In bi ...

** family

Amphibulimidae Amphibulimidae is a taxonomic family of land snails, semi-slugs, terrestrial pulmonate gastropod molluscs in the superfamily Orthalicoidea.Breure A. S. H. & Romero P. (2012). "Support and surprises: molecular phylogeny of the land snail super ...

: ''

Amphibulima ''Amphibulima'' is a genus of air-breathing land snails, a terrestrial pulmonate gastropod mollusks in the family Amphibulimidae.Breure A. S. H., Groenenberg D. S. J. & Schilthuizen M. (2010). "New insights in the phylogenetic relations withi ...

'', ''

Gaeotis ''Gaeotis'' is a genus of air-breathing land semi-slugs,Breure A. S. H. (2010). "The rediscovery of a semi-slug: ''Coloniconcha prima'' Pilsbry, 1933 (Gastropoda, Pleurodontidae) from Hispaniola". ''Basteria'' 74(4-6): 78-86. terrestrial animal, ...

'' ** family

Xanthonychidae Xanthonychidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Helicoidea. MolluscaBase eds. (2021). MolluscaBase. Xanthonychidae Strebel & Pfeffer, 1879. Accessed through: World Register of M ...

: '' Cryptostrakon'', '' Semiconchula,'' '' Xanthonyx'' ** family

Pleurodontidae Pleurodontidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Helicoidea. MolluscaBase eds. (2020). MolluscaBase. Pleurodontidae Ihering, 1912. Accessed through: World Register of Marine S ...

: ''

Coloniconcha prima ''Coloniconcha prima'' is a species of air-breathing semi-slug, a terrestrial animal, terrestrial pulmonate gastropod mollusk in the family Pleurodontidae.Breure A. S. H. (2010). "The rediscovery of a semi-slug: ''Coloniconcha prima'' Pilsbry, 19 ...

'' *

Tropical Africa Although tropical Africa is mostly familiar to the West for its rainforests, this biogeographic realm of Africa is far more diverse. While the tropics are thought of as regions with hot moist climates, which are caused by latitude and the tr ...

** family Urocyclidae: '' Gymnarion''

References

{{reflist Gastropod anatomy

Examples

See also

References