Among the freshwater mussel family Margaritiferidae the Asian species are the least known. One of these, Margaritinopsis dahurica, occurs in the Amur River and Maritime province drainage systems of eastern Russia. A second taxon, M. sujfunensis, has been distinguished from M. dahurica on the basis of height/length ratio of the shell. The availability of several specimens assigned to these taxa has permitted a study of the shell and anatomy. Height/length ratios varied little within the sample and no clear pattern was discerned supporting a two species concept. Nevertheless, the shell characteristics of M. dahurica sensu lato clearly distinguish it from all other margaritiferid species. The anatomy of M. dahurica reveals that the species is correctly assigned to the Margaritiferidae.
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