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 Methanosarcinales Boone et al. 2001 nom. inval. see Order Methanosarcinales Boone et al. 2002 Family Methanosarcinaceae Balch and Wolfe 1981 Genus Methanohalobium Zhilina and Zavarzin 1988