[Morphological basics of systematics of Eurycercidae Kurz, 1875 sensu Dumont et Silva-Briano, 1998 (Cladocera: Anomopoda) family].

We analyzed data from the literature and our own results to discover common principles underlying the systematics of the Eucercidae Kurz, 1875 sensu Dumont et Silva-Briano, 1998 (Cladocera: Anomopoda) family, which is represented only by the genus Eurycercus Baird, 1983. The appropriateness of using various diagnostic features for identification of species was evaluated. We estimated the accuracy of using age variability of different morphometric parameters for determination of species. It was demonstrated that using oligomerous structures is more effective for differentiation of species than counting the structures the number ofwhich can vary considerably. The independence of the Bullatifrons Frey, 1975 subgenus was found to be questionable.