procaryotes
   Domain Archaea Woese et al. 1990 stat. inval. see Domain Archaea Woese et al. 2024
     Phylum Euryarchaeota Garrity and Holt 2001
       Class Methanopyri Garrity and Holt 2001 nom. inval. [monotypic] see Class Methanopyri Garrity and Holt 2002
         1 Order Methanopyralesᵀ Huber and Stetter 2001 nom. inval. [monotypic] see Order Methanopyrales Huber and Stetter 2002