[Phylum] [Arthropoda] Siebold, 1848 - arthropods
   Chelicerata Heymons, 1901
     Euchelicerata Weygoldt & Paulus, 1979
       Xiphosura Latreille, 1802 - horseshoe crabs see Class Xiphosura Latreille, 1802
         Prosomapoda Lamsdell, 2013
           [Class] Xiphosura Latreille, 1802 [monotypic] - horseshoe crabs
             1 Genus †Lunataspis Rudkin, Young & Nowlan, 2008
             2 Genus †Maldybulakia Tesakov & Alekseev, 1998
             3 ?Genus †Willwerathia Størmer, 1969
             4 Family †Kasibelinuridae Pickett, 1993
             5 [Order] Xiphosurida Latreille, 1802
             6 Genus †Belinuropsis Matthew, 1910, incertae sedis