Phylogenetic Position and Morphological Characteristics of the Plagiorchioid Trematode, Skrjabinoplagiorchis polonicus (Soltys, 1957), a Parasite of Rodents

The genus <i>Skrjabinoplagiorchis</i> is monotypic, with <i>Skrjabinoplagiorchis polonicus</i> parasitizing rodents in the Western Palaearctic. This genus is classified within the family Plagiorchiidae; however, its taxonomic position remains unclear. In the present study, two species of digeneans, <i>S. polonicus</i> and <i>Rubenstrema exasperatum</i>, found in small mammals in the Middle Volga region (European Russia), were examined. We provide morphological descriptions of the studied trematodes complemented with a molecular phylogenetic analysis of partial sequences of the 28S rDNA gene, obtained for these helminths of mammals in Russia for the first time. Based on morphological data and the results of molecular phylogenetic analysis, we reassign the genus <i>Skrjabinoplagiorchis</i> from the subfamily Plagiorchiinae to the subfamily Omphalometrinae. Previously, digeneans of the subfamily Omphalometrinae were known only as parasites of insectivores of the order Eulipotyphla.