A monograph of the Dimarcusidae (Platyhelminthes, Seriata, Tricladida)

Abstract

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.