Chelicerata Heymons, 1901 see Superclass Chelicerata Heymons, 1901 Euchelicerata Weygoldt & Paulus, 1979 [Class] Xiphosura Latreille, 1802 - horseshoe crabs 1 †"synziphosurines" 2 [Order] Xiphosurida Latreille, 1802