Bigyra Cavalier-Smith, 1998
   Subphylum Opalozoa Cavalier-Smith, 1992
     Infraphylum Placidozoa Cavalier-Smith, 2013
       Superclass Opalinata Wenyon, 1926
         Class Blastocystea Zierdt, 1978 [monotypic]
           Order Blastocystida Zierdt, 1978 [monotypic]
             Family Blastocystidae Jiang & He, 1993, nom. illeg. [monotypic]
               1 Genus Blastocystisᵀ Aléxéieff, 1911