Ariunculus
Ariunculus is a genus of air-breathing land slugs in the family Arionidae, the roundback slugs. Sometimes it has been considered as a subgenus of Arion, and sometimes the subgenus Ichnusarion has been raised to generic rank.
Etymology
The stem of Arion plus the suffix -unculus, which is a diminutive in Latin. Hence "little Arion". Pollonera justifies why "Ariunculus" is appropriate rather than "Arionculus".The subgenus name Ichnusarion is also based on "Arion", to which has been added "Ichnusa", a Latin name of Sardinia, where the single species of this subgenus is endemic.
Species
Only two species are currently recognised:subgenus AriuncululusAriunculus speziae Lessona, 1881 - type species of the genus; Italian Alps with one record in Switzerland
subgenus Ichnusarion Pollonera, 1890Ariunculus isselii Lessona & Pollonera, 1882 - Sardinia
Other species have been discounted as distinct members of the genus:A. mortilleti and A. camerani are considered synonyms of A. speziae ;A. moreleti is considered a species of Letourneuxia;A. pallaryi matches Letourneuxia numidica in its description;A. austriacus has been synonymised with Arion subfuscus;A. tricolor and A. nigratus are thought to have been misidentified juveniles of a large Arion;A. ischii was apparently a misprint for A. isselii.
Diagnostic characters
Genital characters that have been proposed as diagnostic of the genus are:- the genital pore is very anterior, anterior to the pneumostome;
- the atrium is large;
- the duct of the bursa copulatrix opens near the end of the epiphallus;
- the oviduct is long with two bends;
- the epiphallus blends imperceptibly with the vas deferens;
Ariunculus differs from Geomalacus, and is similar to Arion, in that the caudal gland is prominent and the mantle contains only calcareous granules rather than a shell plate.