Chelicerata Heymons, 1901
   Scorpiones Koch, 1837 - scorpions
     Orthosternina Pocock, 1911 see Infraorder Orthosterni Pocock, 1911
       Superfamily Scorpionioidea Dunlop, Penney & Jekel, 2010, orth. inval. see Superfamily Scorpionoidea Latreille, 1802
         1 Family †Palaeopisthacanthidae Kjellesvig-Waering, 1986
         2 Genus †Compsoscorpius Petrunkevitch, 1949
         3 Family Pseudochactidae Gromov, 1998