Chelicerata Heymons, 1901
   †Eurypterida Burmeister, 1843 - eurypterids
     †Eurypterina Burmeister, 1843
       †Diploperculata Lamsdell, Hoşgör & Selden, 2013
         Superfamily †Pterygotioidea Dunlop, Penney & Jekel, 2010, orth. inval. see Superfamily Pterygotoidea Clarke & Ruedemann, 1912
           1 Family †Hughmilleriidae Kjellesvig-Waering, 1951
           2 Family †Slimonidae orth. inval. see Family Slimoniidae Novojilov, 1962
           3 Family †Pterygotidae Clarke & Ruedemann, 1912