Preliminary comments on a phylogenetic study of the order Diphyllidea van Beneden in Carus, 1863

The basis for a preliminary analysis of the relationships within the monoph yletic Diphyllidea is outlined. Information on morphological characters and their interpretation within a phylogenetic context are presented. A cladis tic analysis at the species level was conducted based on a matrix of 21 mor phological characters. Character polarity was determined by taxonomic outgr oup analysis relative to the basal orders, Pseudophyllidea and Haplobothrii dea. The phylogeny for the diphyllideans was found to be poorly resolved ba sed on characters currently available for evaluation. Computer assisted cla distic analysis found three equally parsimonious trees with a consistency i ndex of 0.54. The topology of these trees shows that Ditrachybothridium mac rocephalum is the basal taxon and the putative sister group for species of Echinobothrium; Macrobothridium rhynchobati is grouped among species of Ech inobothrium. If the classification is to be consistent with this tree, M. r hynchobati should be included in the genus Echinobothrium. This observation should be carefully examined, considering the relative paucity of useful m orphological characters currently available for this group.