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 Methanomicrobiaceae Balch and Wolfe 1981 Genus Methanoplanus Wildgruber et al. 1984