living organisms see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   Superkingdom Eukaryotae see Domain Eukaryota Chatton, 1925
     Kingdom Animalia Linnaeus, 1758 - animals
       Subkingdom Eumetazoa Butschli, 1910 see [unranked] Eumetazoa Bütschli, 1910
         Phylum Gnathostomulida Ax, 1956 - gnathostomulids
           Order Bursovaginoidea Sterrer, 1972
             Suborder Scleroperalia Sterrer, 1972
               1 Family Agnathiellidae Sterrer, 1972
               2 Family Mesognathariidae Sterrer, 1972
               3 Family Gnathostomariidae Sterrer, 1972
               4 Family Rastrognathiidae R.M. Kristensen & A. Nørrevang, 1977
               5 Family Problognathiidae Sterrer & Farris, 1975
               6 Family Onychognathiidae Sterrer, 1972
               7 Family Gnathostomulidae Sterrer, 1972