Protozoa Goldfuss, 1818 - protozoans
   Phylum Ciliophora Doflein, 1901 - ciliates
     Class Oligohymenophorea de Puytorac et al., 1974 - oligohymenophoreans
       Subclass Hymenostomatia (Delage & Hérouard, 1896) Cavalier-Smith, 1993 - hymenostome ciliates
         Order Astomatida Schewiakoff, 1896
         Order Hymenostomatida Delage & Hérouard, 1896 see Subclass Hymenostomatia (Delage & Hérouard, 1896) Cavalier-Smith, 1993
         Order Scuticociliatida Small, 1967 see Subclass Scuticociliatia (E.B. Small, 1967)