Macrodasyida (Gastrotricha): a cladistic analysis of morphology

A cladistic analysis based on 33 morphological characters was performed for the 31 genera currently assigned to the order Macrodasyida (Gastrotricha). Outgroup analysis indicated that the order is monophyletic and that it is defined by the structure of the pharynx and the complex distribution of duo -gland adhesive organs. Of the 6 currently recognized families in Macrodasy ida, our analysis confirmed that 4 families are monophyletic: Dactylopodoli dae, Macrodasyidae, Thaumastodermatidae and Turbanellidae. Dactylopodolidae was further confirmed as the most basal family within the order based on t he retention of several plesiomorphies. The other three families have well- defined autapomorphies but will require further investigation to increase i nter- and intrafamilial phylogenetic resolution. Planodasyidae appeared to be a paraphyletic taxon with no obvious autapomorphies; genera clustered am ong members of a polyphyletic family, Lepidodasyidae. We recommend that fut ure research on macrodasyidan phylogeny focus on issues of comparative morp hology and ultrastructure in lesser-known taxa such as the Dactylopodolidae , and on the taxa Lepidodasyidae and Planodasyidae.