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
           Family †Pterygotidae Clarke & Ruedemann, 1912
             1 Genus †Acutiramus Ruedemann, 1935
             2 Genus †Ciurcopterus Tetlie & Briggs, 2009
             3 Genus †Erettopterus Salter, 1859
             4 Genus †Jaekelopterus Waterston, 1964
             5 Genus †Necrogammarus Woodward, 1870
             6 Genus †Pterygotus Agassiz, 1845