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 Genus Opalina Purkinje & Valentin, 1835