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
         1 ?Genus Methanocalculus Ollivier et al. 1998
         2 Family Methanomicrobiaceae Balch and Wolfe 1981
         3 Family Methanocorpusculaceae Zellner et al. 1989
         4 Family Methanospirillaceae see Family Methanospirillaceae Boone et al. 2002