The identity and composition of the Euglenozoa

The taxon Euglenozoa was originally created to include the kinetoplastids and euglenids only. Subsequently, euglenozoan identity and/or affinities have been suggested for Diplonema, Stephanopogon, the Hemimastigophora and several even more poorly understood eukaryotes. The Euglenozoa have only ever been defined by circumscription and/or composition; attributes that change as taxa are added or removed. This paper seeks to refine and stabilise the concept of the Euglenozoa by redefining it as a clade identified by synapomorphy. It is proposed that the Euglenozoa be identified by the character 'heteromorphic (tubular and parallel) lattice paraxonemal rods'. Applying this definition, the Euglenozoa currently consists of four subgroups; euglenids, kinetoplastids, diplonemids (i.e. Diplonema and Rhynchopus) and Postgaardi. The reasons for the exclusion of Stephanopogon and the Hemimastigophora are also presented.