Mussel of the

Page last updated
2 July 2008

Mussel of the Month

The July 2008 Mussel of the Month is Harmandia somboriensis. Harmandia is a genus of two species endemic to Indochina, although some authors have claimed the type species is merely a hyriid from South America.

Harmandia somboriensis
Top left: MNHN. Cochinchine (type, Harmandia somboriensis).
Top right: MNHN. Cochinchine (type, Harmandia castelneaui).
Bottom: Prisodon (Triplodon) corrugatus. MNHN. Brasil.

The genus Harmandia illustrates well the superficial similarity between some Indotropical unionids and Neotropical hyriids. The classical, conchological distinction among these lineages has been beak sculpture: hyriids (like Castalia) have radial beak sculpture. Or, it can be radial like in the South American Prisodon (Triplodon). But, there are southeast Asian genera with similar sculpture, such as Scabies and Harmandia. Based upon soft-anatomy, these genera can be place in the correct family, and these shell characters can be seen for what they are: misleading. This bears upon the diagnosis of fossil Hyriidae, especially those forms from the Triassic of North America, which other seem quite far out of range.

In the specific case of Harmandia, the type species, H. somboriensis, has only been known by two, small specimens from the Mekong River. Many authorities, like Haas (1969) and Simone (2006), have simply regarded Harmandia to actually be a Triplodon erroneously assigned to the Indotropics. Brandt (1974), however, claimed to have collected larger specimens of H. somboriensis in the Mekong. He also described a second species in the genus, H. munensis.


Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida

Superfamily UNIONOIDEA Rafinesque, 1820

Family UNIONIDAE Rafinesque, 1820

Genus Harmandia Rochebrune, 1882

Species Hardmandia somboriensis (Rochebrune, 1882)
[+ Harmandia castelneaui Rochebrune, 1904]

For more information about Harmandia and its confusion with Prisodon (Triplodon), check out:
  • Haas, F. 1969. Superfamilia Unionacea. Das Tierreich (Berlin) 88: 663 pp.
  • Brandt, R.A.M. 1974. The non-marine aquatic Mollusca of Thailand. Archiv für Molluskenkunde 105(1-4):1-423.
  • Simone, L.R.L. 2006. Land and Freshwater Molluscs of Brazil: An Illustrated Inventory of the Brazilian Malacofauna, Including Neighboring Regions of South America, Respect to the Terrestrial and Freshwater Ecosystems. EGB. Fapesp. São Paulo. 390 pp.
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