Klishko, O., M. Lopes-Lima, E. Froufe, A.E. Bogan, L. Vasiliev & L. Yanovich. 2017. Taxonomic reassessment of the freshwater mussel genus Unio (Bivalvia: Unionidae) in Russia and Ukraine based on morphological and molecular data. Zootaxa 4286(1): 93-112. Available electronically.
(click the figure number to see the cladogram)
+-- Nodularia_douglasiae
+--------+
| +-- Nodularia_breviconcha
--+
| +-------- Unio_tumidus
+--+
| +----- Unio_pictorum
+--+
| +-- Unio_nanus
+--+
+-- Unio_crassus