Bigyra Cavalier-Smith, 1998
   Subphylum Opalozoa Cavalier-Smith, 1992
     Infraphylum Placidozoa Cavalier-Smith, 2013
       Superclass Opalinata Wenyon, 1926
         Class Opalinea Wenyon, 1926
           Order Opalinida Poche, 1913
             Family Opalinidae Claus, 1874
               1 Genus Cepedea Metcalf, 1920
               2 Genus Protoopalina Metcalf, 1918
               3 Genus Opalina Purkinje & Valentin, 1835