Kingdom Chlorobiota C.Jeffrey ex Doweld (2001) - plants see Subkingdom Viridiplantae Caval.-Sm. (1981)
   Subkingdom Pteridobiotina Britton & A. Br. (1896)
     Superdivision Cycadophytanae Doweld (2001) see Superphylum Cycadophytanae Doweld (2001)
       Division †Pteridospermatophyta Meyen
         Class †Lyginopteridopsida Novák (1961)
           Order †Lyginopteridales Havlena (1961)
             Family †Physostomataceae A.G. Long (1975) [monotypic]
               1 Genus †Physostoma Williamson (1875)