There is no real consensus on the taxonomy of the helminths, differing textbooks showing different groupings, particularly with the nematodes. The term 'Helminth' itself contains a number of phyla, many of which are completely unrelated (for example the Annelids are much more closely related to the Arthropods than the Platyhelminthes, and the Nematodes appear to be even more distantly related). However, for convenience sake the term is still used to describe four groups with superficial similarities, the phyla Annelida, Platyhelminthes, Nematoda and Acanthocephala. A fifth group, the phylum Pentastomida (the Tongue worms) are not usually included here. The following taxonomy of the Helminths is that generally used, and is shown with particular reference to the schistosomes. The two most important phyla in terms of parasites infecting man are the Platyhelminthes (Digeneans and Cestodes), and the Nematodes. For more information of the true phylogenetic relationship between these organisms, see the University of Arizona's ' Tree of Life' pages, or the University of California Museum of Palaeontology Phylogeny Pages.
Click on above phyla for further information.