Dreissena rostriformis distincta is a (possible) subspecies of freshwater mussel, an aquatic bivalve mollusk in the family Dreissenidae. It was originally described in 1897 as a variety of D. rostriformis by Andrusov (Andrusov, 1897: 273-276, pl. 14, figs. 18-24.)
The type locality was numerous localities in the Volga River, Caspian, Black and Marmara seas (both Recent and fossil).[1]
However, the exact taxonomy of the species within the genus Dreissensa is uncertain. As Kantor et al. commented, "...the Russian specialists on fresh-water molluscs appeared to be “splitters” comparing with their western colleagues. This sometimes leads to extreme differences in opinion on species number and taxonomy of some groups."[2]