The Current Status of the Free‐Living Heterotrophic Flagellates

The “flagellates” as a taxon has become obsolete and should be dispensed with. It is obsolete because it is not phylo‐genetically coherent. Adopting an ultrastructural perspective, it is argued that the flagellates exemplify an extreme case of paraphyly. Meaningful discussion of the evolution or ecology of flagellates can only emerge after we identify the monophyletic constituents of the flagellates. There are over 40 known types of heterotrophic flagellates and these should form the basis of a new understanding of flagellate diversity.