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 Annelida Lamarck, 1809 - segmented worms
           Class Hirudinoidea see Class Clitellata Michaelsen, 1919
             Subclass Hirudinea see Subclass Euhirudinea Lukin, 1956
               Order Arhynchobdellae see Order Arhynchobdellida Blanchard, 1894
                 1 Family Americobdellidae
                 2 Family Mesobdellidae
                 3 Family Hirudinidae Whitman, 1886
                 4 Family Haemopidae Sawyer, 1986
                 5 Family Xerobdellidae
                 6 Family Haemadipsidae Blanchard, 1893
                 7 Family Semiscolecidae
                 8 Family Erpobdellidae Blanchard, 1894
                 9 Family Gastrostomobdellidae Richardson, 1971