Vertebrata Cuvier, 1812 - vertebrates
   Class Agnatha Cope, 1889 [paraphyletic]
     Subclass †Pteraspidomorphi Goodrich, 1909 see Class Pteraspidomorphi Goodrich, 1909
       Order †Heterostraci Lankester, 1868 - heterostracans see Subclass Heterostraci Lankester, 1868
         01 ?Family †Arandaspididae Ritchie & Gilbert-Tomlinson, 1977
         02 Family †Astraspidae [monotypic]
         03 Family †Eriptychiidae Tarlo, 1962 [monotypic]
         04 Family †Cyathaspididae Flower & Wayland-Smith, 1952
         05 Family †Amphiaspidae see Family Amphiaspididae
         06 Family †Corvaspidae Dineley, 1953 [monotypic] see Family Corvaspididae Dineley, 1953
         07 Family †Traquairaspididae
         08 Family †Pteraspidae see Family Pteraspididae Claypole, 1885
         09 Family †Cardipeltidae Bryant, 1933
         10 Family †Drepanaspidae see Family Psammosteidae Traquair, 1896