Kingdom Animalia Linnaeus, 1758 - animals Phylum Arthropoda Siebold, 1848 - arthropods Subphylum Cheliceriformes Class Chelicerata Heymons, 1901 Subclass Merostomata Dana, 1852 - horseshoe crabs see Class Xiphosura Latreille, 1802 Order †Eurypterida Burmeister, 1843 - eurypterids Genus †Pterygotus Agassiz, 1845