Dr. Murai Éva szerk.: Parasitologia Hungarica 16. (Budapest, 1983)

PHYLOGENETIC RELATIONSHIPS OF DIPLODISCIDAE The major part of systematists agree in principle that the best classification is the one which reflects the natural relationships among the representatives of a group under study. Of the schools of systematics the cladistic approach to phylogenetic relationship outlined by HENNIG (1966) is the most profitable hypothesis. Accordingly, the natural classification should be based on monophylic groups which are deliminated by synapomorphous characters. The cladogram, which represents the estimated phylogenetic kinship, can also serve as a hypothesis on which biographical, chronistical and co-evolutionary considerations may be based. Adult diplodiscids share 11 characteristics in combination which distinguish them from other families of Diplodiscoidea. They are 1) one or two testes in the middle or posterior third of body, 2) vitellaria in lateral region, along caeca or at the zone of caecal end, 3) absence of genital sucker, 4) ovary at zone of caecal end, 5) uterus inter or extra caecal, 6) ventral sucker with or without accessory sucker, 7) pharynx with anterior sphincter, 8) spherical oesophageal bulb, 9) short or long caeca, 10) opening of excretory canal beyond that of LAURER's and 11) formula of epidermal cells of miracidia 6:6:4:2. Although some of these characters are also found is some species of other families of the Diplodiscoidea (out-group traits) but only those species possessing the above listed characters (in-group traits) belong, in the Diplodiscidae SKRJABIN, 1949 outlined in this paper. Derrnatemitrpma Fig. 19: Cladogram depicting phylogenetic relationships of genera Diplodiscidae