Chordata Bateson, 1885 - chordates
   Class †Ostracophori
     Order †Heterostraci Lankester, 1868 - heterostracans see Subclass Heterostraci Lankester, 1868
       08 Family †Thelodontidae Jordan, 1905 (1856)
       09 Family †Psammosteidae Traquair, 1896
       10 Family †Astraspidae Eastman, 1917 [monotypic] see Family Astraspididae Eastman, 1917, nom. praeval.
       11 Family †Drepanaspidae [monotypic] see Family Psammosteidae Traquair, 1896
       12 Family †Ceraspidae Woodward, 1891, nom. illeg. [monotypic] see Family Pterichthyodidae Stensiö, 1948
       13 Family †Pteraspidae see Family Pteraspididae Claypole, 1885