Protozoa Goldfuss, 1818 - protozoans
   Phylum Ciliophora Doflein, 1901 - ciliates
     Class Polyhymenophorea - spirotrichs see Class Spirotrichea Bütschli, 1889
       Subclass Spirotrichia
         Order Heterotrichida Stein, 1859 - heterotrichs
         Order Hypotrichida Stein, 1859 - hypotrichs see Subclass Hypotrichia (Stein, 1859) Cavalier-Smith, 1993
         Order Odontostomatida Sawaya, 1940 - odontostomatids
         Order Oligotrichida Bütschli, 1889 see Subclass Oligotrichia Bütschli, 1889