Domain Eucaryota
   Subdomain Chlorota Doweld (2001)
     Kingdom Chlorobiota C.Jeffrey ex Doweld (2001) - plants see Subkingdom Viridiplantae Caval.-Sm. (1981)
       Subkingdom Pteridobiotina Britton & A. Br. (1896)
         Superphylum Cycadophytanae Doweld (2001)
           Phylum Cycadophyta Bessey (1907) see Subclass Cycadidae Pax (1894)
             Class †Phasmatocycadopsida Doweld (2001)
               Order †Gigantopteridales X.X.Li & Z.Q. Yao (1983)
                 1 Family †Emplectopteridaceae Wagner (1967)
                 2 Family †Spermopteridaceae Doweld (2001)
                 3 Family †Gigantopteridaceae Koidzumi (1936)