Kingdom [Animalia] Linnaeus, 1758 - animals
   Subkingdom Metazoa Haeckel, 1874 see Kingdom Animalia Linnaeus, 1758
     Division Eumetazoa Butschli, 1910 see Subkingdom Eumetazoa Butschli, 1910
       Subdivision Bilateralia
         Phylum Platy-helminthes see Phylum Platyhelminthes Gegenbaur, 1859
           Class Gnathostomulida Riedl, 1969 see Phylum Gnathostomulida Ax, 1956
             Genus Pterognathia Sterrer, 1966
               Pterognathia simplex Sterrer, 1966 see Haplognathia simplex (Sterrer, 1966)