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 Archezoa Cavalier-Smith, 1983 see Infrakingdom Archezoa Cavalier-Smith, 1983
         Phylum Metamonada Grassé, 1952
           Genus Giardia Künstler, 1882
           1 retortamonads see [unranked] Retortamonadida Grassé, 1952
           2 diplomonads see [unranked] Diplomonadida Wenyon, 1926