procaryotes
   Domain Archaea Woese et al. 1990
     Phylum Euryarchaeota Garrity and Holt 2001
       Class Methanopyri Garrity and Holt 2001 nom. inval. see Class Methanopyri Garrity and Holt 2002
         Order Methanopyrales Huber and Stetter 2001 nom. inval. see Order Methanopyrales Huber and Stetter 2002
           Family Methanopyraceae Huber and Stetter 2001 nom. inval. see Family Methanopyraceae Huber and Stetter 2002
             Genus Methanopyrus Kurr et al. 1992