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Hyridella aquilonalis (Iredale, 1934)

Diagnostic features

Shell elongate, oblong to dorso-ventrally compressed oval, posterior edge rounded with a well defined  posterior ridge, postero-dorsal margin bluntly angled and dorsal margin anterior to beaks slopes away strongly, anterior edge rounded, ventral margin flat. Valves flattened. Exterior of valves very dark olive, interior of valves bluish to bronze. Exterior sculpture of valves with growth lines and no traces of wrinkles. Reaches about 58 mm in length, height/length ratio less than 50%. This species differs from all other Hyridella species primarily in its very isolated occurrence in the Bloomfield River of far north Queensland – far north of the SE Australian populations of other Hyridella species and in its apparent lack of wrinkles near the shell beaks.

Classification

Hyridella aquilonalis (Iredale, 1934)

Class Bivalvia

Subclass Heteroconchia

Superorder Palaeoheterodonta

Order Unionida

Superfamily Unionoidea

Family Hyriidae

Subfamily: Hyriinae

Genus Hyridella Swainson, 1840

Original name: Rugoshyria aquilonalis Iredale, 1934. Iredale, T. (1934). The freshwater mussels of Australia. Australian Zoologist 8: 57-78 pls 3-6.

Type locality: Bloomfield River, Queensland.

State of taxonomy

The last major taxonomic revision of Australian freshwater mussels was by McMichael and Hiscock (1958).

Based on the available molecular results, Walker et al. (2014) pointed out that a re-assessment of Australian hyriids is needed.

Biology and ecology

Shallow burrower in silty sand/mud in streams and rivers. Suspension feeder. Larvae (glochidia) are brooded in the gills and, when released, become parasitic on fish gills before dropping to the sediment as young mussels.

Additional information on the biology and ecology of members of this family can be found in Fauna of Australia, vol. 5A, p. 296-298.

Distribution

Bloomfield River, northeast Queensland.

Notes

The identity of this species needs to be assessed. Only the holotype is known from this locality and, to our knowledge, the species has not been re-collected. McMichael & Hiscock (1958) thought that it might be related to Hyridella depressa. 

Further reading

Iredale, T. (1934). The freshwater mussels of Australia. Australian Zoologist 8: 57-78 pls 3-6.

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

Lamprell, K. & Healy, J. (1998). Bivalves of Australia, volume 2. Leiden, Backhuys Publishers.

McMichael, D. F. & Hiscock, I. D. (1958). A monograph of the freshwater mussels (Mollusca: Pelecypoda) of the Australian region. Australian Journal of Marine and Freshwater Research 9: 372-508.