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 Platyhelminthes Gegenbaur, 1859 - flatworms
           Class Turbellaria Ehrenberg, 1831 - planarians see Subphylum Turbellaria Ehrenberg, 1831
             Order Catenulida Meixner, 1924 - catenulid flatworms
               1 Family Catenulidae Graff, 1905
               2 Family Stenostomidae Vejdovsky, 1880
               3 Family Chordariidae Marcus, 1945
               4 Family Tyrrheniellidae Riedl, 1959
               5 Family Retronectidae Sterrer & Rieger, 1974