Monogenea in the light of new evidence and their position among platyhelminths.

Existing schemes of monogenean classification are examined. Modification of Monogenoidea class system is suggested with due regard for new data. Monogeneans are classified in 53 families from subclasses Polyonchoinea (4 supraorders, 6 orders and 19 families); Polystomationea (1 order, 2 families) and Oligonchoinea (2 supraorders, 3 orders and 32 families). Substantiation of taxonomical changes and comments on high level taxa structure are given. Cladistic views on flatworms classification are critically analyzed. The results obtained in this way are not entirely new; purely cladistic formalization and erroneous interpretation of generally accepted morphological notions will lead to incorrect conclusions.