prokaryotes - bacteria see Domain Bacteria Woese et al. 1990
   Domain "Archaea" Woese et al. 1990
     Phylum "Euryarchaeota" Garrity and Holt 2001
       Class "Methanomicrobia"
         Order Methanomicrobiales Balch and Wolfe 1981
           Family Methanospirillaceae Boone et al. 2002 [monotypic]
             1 Genus Methanospirillum Ferry et al. 1974 (Approved Lists 1980)