eukaryotes see Domain Eukaryota Chatton, 1925
   Kingdom Protozoa Goldfuss, 1818 [paraphyletic] - protozoa
     Subkingdom Natozoa Cavalier-Smith, 2021 [paraphyletic]
       Infrakingdom Archezoa Cavalier-Smith, 1983 [monotypic] see Phylum Metamonada Grassé, 1952
         Phylum Metamonada Grassé, 1952
           Subphylum Trichozoa Cavalier-Smith, 1997
             Infraphylum Parabasalia Honigberg, 1973
               Class Trichomonadea Kirby, 1947
                 Genus Histomonas Tyzzer, 1920