Chlorobiota C.Jeffrey ex Doweld (2001) - plants see Subkingdom Viridiplantae Caval.-Sm. (1981)
   Pteridobiotina Britton & A. Br. (1896)
     Cycadophytanae Doweld (2001) see Superphylum Cycadophytanae Doweld (2001)
       Cycadophyta Bessey (1907)
         †Cycadeoideales E.W.Berry (1916)
           †Williamsoniellaceae Nakai (1943)
             1 †Wielandella orth. inval. see Genus Wielandiella Nath. (1910)
             2 †Williamsoniella H.H.Thomas (1915)