• asexual organisms;
  • Euglenaceae;
  • Euglenida;
  • Euglenophyta;
  • molecular phylogeny;
  • morphology;
  • Phacus;
  • rDNA;
  • sequence variability;
  • taxonomic revision

The establishment of epitypes (together with emended diagnoses) for seven species of Phacus Dujard. [Phacus oscillans G. A. Klebs, Phacus parvulus G. A. Klebs, Phacus pusillus Lemmerm., Phacus skujae Skvortzov, Phacus inflexus (Kisselew) Pochm., Phacus polytrophos Pochm., and Phacus smulkowskianus (Zakryś) Kusber] was achieved by literature studies, verification of morphological diagnostic features (cell size, cell shape), as well as molecular characters (SSU rDNA). The investigated Phacus species are mostly well distinguished morphologically, with an SSU rDNA interspecific sequence similarity of 95.1%–99.0% and an intraspecific sequence similarity of 99.0%–99.9%. Some of the phylogenetic relationships among the seven species have not been resolved, but the topology obtained indicates their assignment into two sister clades. The first clade is composed of two sister groups (P. parvulus and P. pusillus), while the second constitutes an assemblage of the remaining five species. The relationships between the clades remain unresolved.