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Amerianna Strand, 1928

Disclaimer

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

Members of this genus have a sinistral, cylindrical carinate shell with a truncate to slightly raised spire. The body whorl is strongly keeled or with rounded shoulders.  The aperture is almost as long as the shell, angular posteriorly, narrowly curved anteriorly. Slight to distinct columellar fold. Surface usually smooth; some specimens, especially juveniles, with spiral rows of periostracal hairs. The copulatory organ is an unbranched (uniramous), pendant penis with a terminal or lateral pore; the bursa copulatrix is elongate. There are three ridges on the roof of pulmonary cavity and a rectal ridge (Walker 1988).

Classification

Class Gastropoda

Subclass Heterobranchia

Order Hygrophila

Superfamily Planorboidea

Family Planorbidae

Subfamily: Bulininae

Genus Amerianna Strand, 1928

Type species: Physa (America) carinata Adams, 1861 (=Amerianna carinata (Adams, 1861))

Original reference: Adams, H. (1861). Descriptions of a new genus and some new species of the shells from the collection of Hugh Cuming, Esq. Proceedings of the Zoological Society of London 1861: 143-145.

Type locality: Boyne River, Queensland.

Synonyms: Ameria H. Adams, 1861; Ameriella Cotton, 1943.

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

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.

Distribution

Northern regions of Australian mainland, New Guinea, Moluccas, Philippines.

Introduced into Java, Thailand, and Nigeria. The number of species and their distribution is uncertain.

Notes

Relatively small to medium-sized shells with a raised (stepped), flat or depressed spire. The top of the whorls are angled to keeled.

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.

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.

Iredale, T. (1943). A basic list of the fresh water Mollusca of Australia. Australian Zoologist 10: 188-230.

Iredale, T. (1944a). Guide to the freshwater shells of New South Wales. Part 2. Australian Naturalist (Sydney) 11: 113–127.

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