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