Abstract
Adult individuals of Echinochasmus pseudobeleocephalus n. sp. were obtained during an experimental study on trematodes' life cycle. An analysis of the morphometric characteristics of the developmental stages and involvement of first intermediate hosts, snails of the genus Boreoelona, in their life cycle, revealed the identity of the obtained trematodes to the European species Echinochasmus beleocephalus previously discovered in the south of the Russian Far East. However, an analysis of molecular data, in particular sequences of the 28S rRNA gene, showed that the Far Eastern trematodes examined do not belong to European E. beleocephalus despite their morphological similarities. An analysis of phylogenetic relationships within the family Echinochasmidae supported the status of E. pseudobeleocephalus n. sp. as an independent species. Our new data confirmed that the individuals attributed to Echinochasmus can be subdivided into two groups on the basis of the number of head-collar spines and the tail length in cercariae on an intergeneric level.