* Bold entries are protoctist phyla. All species of Archaeprotists lack mitochondria. “Karyomastigont,” “kinetosome,” and “nucleus,” refer to relative proliferation of these organelles. Members of the phylum Archaeprotista group into one of three classes: Pelobiontid giant amoebae; Metamonads, which include three subclasses: Diplomonads (Giardia), Retortamonads (Retortamonas), and Oxymonads (such as Pyrsonympha and Saccinobaculus); and Parabasalia. The Class Parabasalia unites trichomonads, devescovinids, calonymphids, and hypermastigotes such as Trichonympha. The phylum Discomitochondria includes amoebomastigotes, kinetoplastids (Trypanosoma), euglenids, and pseudociliates (Stephanopogon). The Hemimastigophora comprise a new southern-hemisphere phylum of free-living mitochondriate protists (Foissner et al. 1988). Hemimastigophorans probably evolved from members of the kinetoplastid-euglenid taxon (Foissner and Foissner, 1993). If so, they represent a seventh example of release of the nucleus from the karyomastigont and subsequent kinetosome proliferation. The phylum Granuloreticulosa includes the shelled (Class Foraminifera) and unshelled (Class Reticulomyxa) foraminiferans. The phylum Zoomastigota includes five classes of single-celled, free-living and symbiotrophic mitochondriate protists; Jakobids, Bicosoecids, Proteromonads, Opalinids, and Choanomastigotes. Details of the biology are in the work by Margulis et al. (1993). A current phylogeny is depicted in Figure 2.

† Structure known but not demonstrated for all species at the electron microscopic level.