Chelicerata Heymons, 1901
   Scorpiones Koch, 1837 - scorpions
     †Holosternina Kjellesvig-Waering, 1986
       Superfamily †Mesophonoidea Wills, 1910
         1 Family †Centromachidae Petrunkevitch, 1953
         2 Family †Gallioscorpionidae Lourenço & Gall, 2004 [monotypic]
         3 Family †Heloscorpionidae Kjellesvig-Waering, 1986 [monotypic]
         4 Family †Mazoniidae Petrunkevitch, 1913 [monotypic]
         5 Family †Mesophonidae Wills, 1910 [monotypic]
         6 Family †Willsiscorpionidae Kjellesvig-Waering, 1986 [monotypic]