Procaryotic Genera Domain "Archaea" Woese et al. 1990 Phylum Euryarchaeota Garrity and Holt 2001 Class Methanococci Boone 2001 nom. inval. see Class Methanococci Boone 2002 Order Methanococcalesᵀ Balch and Wolfe 1981 Family Methanocaldococcaceae nom. inval. see Family Methanocaldococcaceae Whitman et al. 2002 Genus Methanocaldococcusᵀ Whitman 2001 nom. inval. see Genus Methanocaldococcus Whitman 2002