The figure of this month's MUSSELp Mussel of the Month is from Spix & Wagner's 19th century treatment of the freshwater Mollusca of Brazil. They actually favored two different names for the shell illustrated above: Unio caudatus and Diplodon furcatum! This potential confusion, however, is moot since the same species was described earlier by Schumacher under the name Prisodon obliquus.
Classification:
Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida
Superfamily Etherioidea Deshayes, 1830
Family Hyriidae Swainson, 1840
Subfamily Hyriinae s.s.
Tribe Hyriini
Genus Prisodon Schumacher, 1817
Species Prisodon obliquus Schumacher, 1817
(+ Unio caudatus + Diplodon furcatum, Spix & Wager, 1827)