Chelicerata Heymons, 1901
   †Eurypterida Burmeister, 1843 - eurypterids
     †Eurypterina Burmeister, 1843
       Superfamily †Megalograptoidea Caster & Kjellesvig-Waering, 1955 [monotypic]
         Family †Megalograptidae Caster & Kjellesvig-Waering, 1955
           1 Genus †Echinognathus Walcott, 1882
           2 Genus †Megalograptus Miller, 1873