This species belongs to the Austropyrgus sparsus group, with members characterised by the following shell features: small to medium-sized shells, conical, with convex to slightly convex whorls. In females, the coiled oviduct is of an inverted U-shape or with two or more bends, loops or twists.
Austropyrgus tumidus differs from other members of the group in the following combination of characters: shell small, broad, with squat spire and straight to weakly-convex spire outline and convex whorls, inner lip of aperture narrowly to distinctly separated from parietal wall; inner marginal teeth with 17–19 cusps; more than ½ of pericardium in pallial roof; about ½ of prostate gland in pallial roof; rectum separate from capsule gland.
This species is found in sympatry with two other species of Austropyrgus (A. pusillus and A. glenelgensis) throughout its currently recognised range. The shell of this species differs from A. pusillus in its much larger and broader shell, and from A. glenelgensis in its smaller, more truncated shell. It is also similar in shell shape to A. exiguus, but larger and broader.
Austropyrgus tumidus Clark, Miller & Ponder, 2003
Class Gastropoda
Infraclass Caenogastropoda
Order Littorinida
Suborder Rissoidina
Superfamily Truncatelloidea
Family Tateidae
Genus Austropyrgus Cotton, 1942
Original name: Austropyrgus tumidus 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: Spring at Post and Rail North Camp, 5.4 km east of Battersleys Camp, Lower Glenelg National Park, Victoria.
In streams on water weeds, hard substrata (rocks etc.) and crawling on litter and sediment. Can be locally abundant. Assumed to feed by scraping bacteria and microalgae. Lay solitary capsules containing a single egg. Direct development.
This species is known from a few small springs and streams flowing into the lower part of the Glenelg River, western Victoria.
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.
