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