Kingdom Protozoa Goldfuss, 1818 - protozoa
   Subkingdom Corticata Lankester, 1878 see Subkingdom Biciliata
     Infrakingdom Excavata T. Cavalier-Smith, 2002 see Supergroup Excavata Cavalier-Smith, 2002
       Superphylum Eozoa Cavalier-Smith, 1997 see Infrakingdom Eozoa Cavalier-Smith, 1997
         Phylum Metamonada Grassé, 1952
           Subphylum Trichozoa Cavalier-Smith, 1997
             Superclass Eopharyngia (Cavalier-Smith, 1993) Cavalier-Smith, 2003
               Class Trepomonadea Cavalier-Smith, 1993
                 Subclass Diplozoa (Dangeard, 1910) Cavalier-Smith, 1996 - diplomonads see Order Diplomonadida Wenyon, 1926
                   Order Distomatida Klebs, 1892 see Subfamily Hexamitinae Kent, 1880
                     Genus Spironucleus Lavier, 1936