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 Methanocorpusculaceae Zellner et al. 1989 Genus Methanocorpusculum Zellner et al. 1988