plantenrijk Haeckel (1866) - plants
   [Division] Protophyta Sachs 1874 - primitive plants
     Class Schizomycetes Nägeli 1857 (Approved Lists 1980) - bacteria and related forms
       Order Eubacteriales Buchanan 1917 (Approved Lists 1980) see Order Clostridiales Prévot 1953 (Approved Lists 1980)
         Family Lactobacteriaceae
           Genus Methanococcus Kluyver and van Niel 1936 (Approved Lists 1980)