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The new species Dugesia notogaea Sluys & Kawakatsu, sp. n. is described from Queensland, Australia, representing the first record of the genus Dugesia for that continent. A phylogenetic analysis of the 68 species of Dugesia resulted in the discovery of a new apomorphy for the genus, and a cladogram showing two major phyletic groups. The distributional range of one group has a western accent, whereas that of the other group has an eastern emphasis; the ranges of these two groups overlap in Africa and the Mediterranean region. We attempt to determine the ancestral area for both the Dugesiidae and Dugesia. A scenario for the historical biogeography of the genus Dugesia is discussed. In this scenario it is presumed that the geological history of the Australasian region enabled Dugesia's from southeast Asia to colonize northern Australia. © 1998 The Norwegian Academy of Science and Letters

The triclad family Dimarcusidae contains the species Rhodax evelinae, Opisthobursa mexicana, O. josephinae, Balliania thetisae and Mitchellia sarawakana. A comprehensive description is given of each of these species, covering external features, alimentary system, reproductive system, life cycle, ecology and distribution. Postulated apomorphies of the Dimarcusidae are (1) a penis bulb with gland cells, (2) horizontal orientation of female genital duct or bursal canal, combined with a dorsal opening of the common oviduct or diverticulum and (3) location of the ovaries at some distance posterior to the brain. The genera Rhodax, Opisthobursa and Mitchellia form a monophyletic group, the sistergroup being B. thetisae. The genera Rhodax and Opisthobursa share a sistergroup relationship. The Dimarcusidae should not be classified among the Maricola, Terricola or Paludicola. The family represents a fourth lineage within the Tricladida and is more closely related to the Paludicola and Terricola than to the Maricola.

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Hundreds of planarian species exist worldwide, representing a rich phenotypic diversity. This chapter presents an overview of the morphology and anatomy of various taxonomic groups of planarian flatworms, focusing on features enabling recognition and identification of the animals. The most recent view on the phylogenetic relationships of the planarians is presented, together with geographic distribution patterns of major groups of triclads. The chapter concludes with a brief methodological section outlining species identification on basis of anatomical features. In conjunction with the established laboratory model species, the phenotypic diversity of planarians provides rich opportunities for comparative studies, which this chapter aims to inspire.