A New Species and Genus of Psammophilic Proseriata (Turbellaria, Otoplanidae) from Lake Baikal and Its Phylogenetic Relations as Revealed by 18S rRNA Sequence Data

An illustrated description of Boreusyrtis maksimovae gen. et sp. n., a representative of a new genus of Otoplanidae turbellarians (Proseriata) from Lake Baikal, is given. This flatworm shows a peculiar pattern of the ciliated epithelium of the rostral body end, a special morphology of the pharynx and copulative apparatus, and a distinguished topography of the sexual organs. A comparative morphological analysis of the Baikal otoplanid and related forms has allowed us to carry out their partial taxonomic revision, resulting in the isolation of a new genus Boreusyrtis Lukhnev et Timoshkin gen. n., to which, in addition to the endemic species, the morphologically similar species Pseudosyrtis neiswestnovae Riemann 1965 from the Elbe River was attributed. A molecular genetic analysis was carried out for the 18S rRNA gene, based on which a phylogenetic tree was constructed.