Bilateria Hatschek, 1888 - bilaterians see Subkingdom Bilateria Hatschek, 1888
   Spiralia Schleip, 1929 - spiralians see Superphylum Spiralia Schleip, 1929
     Platyzoa Ax, 1987 see [unranked] Spiralia Schleip, 1929
       Gnathifera Ahlrichs, 1995
         Phylum Syndermata Ahlrichs, 1995
           1 Class Monogononta Plate, 1889
           2.1 Class Bdelloidea Hudson, 1884
           2.2 Genus Seison Grube, 1859
           2.3 Acanthocephala Kohlreuther, 1771