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 †Pachytestopsida Doweld (2001)
               Order †Pachytestales Doweld (2001)
                 Family †Stephanospermaceae Doweld (2001) [monotypic]
                   1 Genus †Stephanospermum Brongn. (1874)