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 Methanospirillaceae see Family Methanospirillaceae Boone et al. 2002
             1 Genus Methanospirillum Ferry et al. 1974 (Approved Lists 1980)