Kingdom Protista (Haeckel, 1866) - protists
   Phylum Ciliophora Doflein, 1901 - ciliates
     Class Polyhymenophorea - spirotrichs see Class Spirotrichea Bütschli, 1889
       Subclass Spirotricha see Class Spirotrichea Bütschli, 1889
         1 Order Heterotrichida Stein, 1859 - heterotrichs
         2 Order Odontostomatida Sawaya, 1940 - odontostomatids
         3 Order Oligotricha Bütschli, 1889 - oligotrichs see Subclass Oligotrichia Bütschli, 1889
         4 Order Hypotrichida Stein, 1859 - hypotrichs see Subclass Hypotrichia (Stein, 1859) Cavalier-Smith, 1993