procaryotes
   Domain Archaea Woese et al. 1990
     Phylum Euryarchaeota Garrity and Holt 2001
       Class Methanococci Boone 2001 nom. inval. see Class Methanococci Boone 2002
         Order Methanomicrobiales Balch and Wolfe 1981
           Family Methanomicrobiaceae Balch and Wolfe 1981
             1 Genus Methanomicrobium Balch and Wolfe 1981
             2 Genus Methanoculleus Maestrojuán et al. 1990
             3 Genus Methanofollis Zellner et al. 1999
             4 Genus Methanogenium Romesser et al. 1981
             5 Genus Methanolacinia Zellner et al. 1990
             6 Genus Methanoplanus Wildgruber et al. 1984