A new higher classification of planarian flatworms (Platyhelminthes, Tricladida)

Abstract

This paper presents a revised classification for the higher taxa within the Tricladida. A historical sketch is provided of the higher classificatory systems of triclad flatworms. As far as possible, the new classification is based on published phylogenetic studies. A phylogenetic tree generalizing currently available hypotheses on the higher-taxon relationships of the Tricladida forms the backbone of the new classification. There is no longer any room in formal classifications for the taxon names Terricola and Paludicola, previously used to indicate the suborders of freshwater and land planarians, respectively. It is a consequence of the new classification that the taxonomic rank of the terrestrial planarians is now at the level of family. A new diagnosis of this family is provided. The taxon name Continenticola denotes a monophyletic group consisting of the freshwater planarians and the terrestrial planarians. At this stage it is difficult to find unequivocal morphological apomorphies enabling a diagnosis for the Continenticola.

Keywords:

• Platyhelminthes
• Tricladida
• Terricola
• Paludicola
• Continenticola
• new classification

Acknowledgements

We are grateful to Dr J. van Tol (Naturalis, Leiden) for discussions on the interpretation of the International Code of Zoological Nomenclature. Dr L. Winsor (Townsville, Australia) is thanked for reading a draft of the paper.