Zoology 10th Edition by Stephen Miller,John Harley

Exercise 15

Interpretations of lophotrochozoan phylogeny, based upon morphological and molecular data, seem to be leading to different conclusions. Taxonomists are working to sort out the differences in these interpretations and present a unified picture of the phylogeny of this very large and diverse group of phyla. The validity of the phylum Platyhelminthes is being reevaluated. The traditional class Turbellaria is paraphyletic and probably will be abandoned as a valid taxonomic group.
Explain why many zoologists doubt that Platyhelminthes is a valid phylum.
FIGURE 10.29 Phylogeny of the Lophotrochozoa. One interpretation of the phylogeny of the lophotrochozoa based on molecular and morophological data. Synapomorphies are based on Brusca and Brusca (2003). Invertebrates. Sinauer. Molecular-based relationships are based on Paps, J. et al. (2009). Lophotrochozoa internal phylogeny: new insights from an up-to-date analysis of nuclear ribosomal genes. Proc. R. Soc. B. 276(1660): 1245-1254. * Some molecular phylogenies show "Platyzoa" as a paraphyletic group. ** Turbellaria is a paraphyletic group.