Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         [crown] Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
           Clade neomura Cavalier-Smith, 1987
             Domain Archaea Woese et al. 1990 [paraphyletic]
               Phylum Euryarchaeota Garrity and Holt 2001
                 Class Methanobacteria Boone 2002 [monotypic]
                   Order Methanobacterialesᵀ Balch and Wolfe 1981
                     Family Methanobacteriaceaeᵀ Barker 1956 (Approved Lists 1980)
                       Genus Methanobrevibacter Balch and Wolfe 1981
                         Methanobrevibacter smithii Balch and Wolfe 1981