Semi-slug

Semi-slugs, also spelled semislugs, are land gastropods whose shells are too small for them to retract into, but not quite vestigial.^[1] The shell of some semi-slugs may not be easily visible on casual inspection, because the shell may be covered over with the mantle.

Side and top view of a Cryptella canariensis from the Canary Islands

Shell of Cryptella canariensis

An unidentified semi-slug from Uganda

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-slug species.^[2] There exist about 1,000 species of semi-slugs in comparison to about only 500 species of slugs.^[1]

Examples

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

• Palearctic and Nearctic
  • family Parmacellidae: Cryptella
  • family Vitrinidae: Eucobresia, Semilimax, Vitrina, Vitrinobrachium^[3]
• Asia - Pacific
  • family Ariophantidae: Parmarion, Ratnadvipia, Varadia
  • family Helicarionidae: Attenborougharion, Helicarion, Howearion, Ibycus, Parmellops, Ubiquitarion
  • Semi-slugs also exist but are exceptional in the Camaenidae.^[2]
• Neotropics
  • family Amphibulimidae: Amphibulima, Gaeotis^[2]
  • family Xanthonychidae: Cryptostrakon, Semiconchula, Xanthonyx^[2]
  • family Pleurodontidae: Coloniconcha prima^[2]
• Tropical Africa
  • family Urocyclidae: Gymnarion ^{[citation needed]}

See also

• "Leatherleaf slugs" - Veronicellidae