procaryotes
   Domain Archaea Woese et al. 1990 stat. inval. see Domain Archaea Woese et al. 2024
     Phylum Euryarchaeota Garrity and Holt 2002 stat. inval. see Kingdom Methanobacteriati (Garrity and Holt 2023) Oren and Göker 2024
       Class Methanococci Boone 2001 nom. inval. see Class Methanococci Boone 2002
         Order Methanococcales Balch and Wolfe 1981
           1 Family Methanococcaceae Balch and Wolfe 1981
           2 Family Methanocaldococcaceae Whitman et al. 2001 nom. inval. see Family Methanocaldococcaceae Whitman et al. 2002