[organisms] see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   Kingdom Animalia Linnaeus, 1758 - animals
     Branch Eumetazoa Butschli, 1910 see [unranked] Eumetazoa Bütschli, 1910
       Division Bilateria Hatschek, 1888 see Subkingdom Bilateria Hatschek, 1888
         Subdivision Protostomia Grobben, 1908 see Infrakingdom Protostomia Grobben, 1908
           Section Eucoelomata see Superphylum Eucoelomata
             Phylum Arthropoda Siebold, 1848 - arthropods
               Subphylum Chelicerata Heymons, 1901
                 Class Merostomata Dana, 1852 - horseshoe crabs see Class Xiphosura Latreille, 1802
                   Subclass †Eurypterida Burmeister, 1843 see Class Eurypterida Burmeister, 1843
                     Genus †Pterygotus Agassiz, 1845