This species belongs to the Austropyrgus cooma group, whose members are characterised by generally pupiform to conical, small to medium-sized shells, where the last whorl and base are evenly convex.
A. nanus differs from other members of the group in the following combination of characters: shell small, with convex spire outline; outer lip weakly thickened and without reflection; bursa copulatrix ovoid; capsule gland with anterior end tapering and compressed-oval in cross section.
This species is the smallest member of the genus and among the few that exhibit obvious sexual dimorphism in shell size, with the females significantly larger than the males.
Austropyrgus nanus Clark, Miller & Ponder, 2003
Class Gastropoda
Infraclass Caenogastropoda
Order Littorinida
Suborder Rissoidina
Superfamily Truncatelloidea
Family Tateidae
Genus Austropyrgus Cotton, 1942
Original name: Austropyrgus nanus Clark, Miller & Ponder, 2003. In Clark, S. A., Miller, A. C. & Ponder, W. F. (2003). Revision of the snail genus Austropyrgus (Gastropoda: Hydrobiidae): A morphostatic radiation of freshwater gastropods in southeastern Australia. Records of the Australian Museum Supplement 28: 1–109.
Type locality: Natural thermal spring, south of dam and pool, Hastings Thermal Springs, west of Hastings, Tasmania.
Occurs in warm water creeks fed by thermal springs, and can be extremely abundant throughout the very small area where it an be found crawling on all substrata. This species and A. solitarius are the only two tateids to be found in this habitat in Tasmania.
This species is found in a number of small warm water creeks (25°C) that are part of Hastings Hot Springs group, south-eastern Tasmania.
Most species of Austropyrgus are geographically isolated and have restricted ranges, and this one is no exception.
Clark, S. A., Miller, A. C. & Ponder, W. F. (2003). Revision of the snail genus Austropyrgus (Gastropoda: Hydrobiidae): a morphostatic radiation of freshwater gastropods in southeastern Australia. Records of the Australian Museum 28: 1–109.
