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Amerianna obesula Iredale, 1943


This genus is in need of revision, and the species concepts we have used have not been rigorously tested. This situation can only be resolved by additional molecular and morphological studies involving comprehensive sampling.

Diagnostic features

A very broad-shelled species with a raised ‘stepped’ spire, strongly angled whorls, and a wide aperture. Known only from the type.


Amerianna obesula Iredale, 1943

Common name: Obese Pouch Snail.

Class Gastropoda

Subclass Heterobranchia

Order Hygrophila

Superfamily Planorboidea

Family Planorbidae

Genus Amerianna Strand, 1928

Original name: Amerianna obesula Iredale, 1943 (new name for P. obesa Adams, non De Kay, 1843). Iredale, T. (1943) A basic list of the freshwater Mollusca of Australia Australian Zoologist 10: 188-230.

Type locality: Fitzroy River, Queensland.

Synonym: Physa (Ameria) obesa Adams,1861 (preoccupied).

State of taxonomy

The species of Amerianna require taxonomic revision - the classification presented here is modified but is based on shells alone.

Biology and ecology

Presumably lives on water weeds, wood etc., in ponds and billabongs. Feeds on algae and detritus. Egg mass a jelly strip containing many small eggs. Development direct.

Additional information on the biology and ecology of members of this family can be found in Fauna of Australia, vol. 5B, p. 1072-1074.


North-eastern coastal Queensland.


The status of this species is questionable. It appears to be known only from the type material. It is rather similar to Amerianna carinata and may be a synonym of that species.

Further reading

Baker, F. C. (1945). The molluscan family Planorbidae. Urbana USA, University of Illinois Press.

Beesley, P. L., Ross, G. J. B. & Wells, A., Eds. (1998). Mollusca: The Southern Synthesis. Parts A & B. Melbourne, CSIRO Publishing.

Hubendick, B. (1955). Phylogeny of the Planorbidae. Transactions of the Zoological Society of London 28: 453-542.

Walker, J. C. (1988). Classification of Australian buliniform planorbids (Mollusca: Pulmonata). Records of the Australian Museum 40: 61-89.