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 Methanobacteria Boone 2001 nom. inval. see Class Methanobacteria Boone 2002
         Order Methanobacteriales Balch and Wolfe 1981
           1 Family Methanobacteriaceae Barker 1956 (Approved Lists 1980)
           2 Family Methanothermaceae Stetter 1982