procaryotes
   Domain Archaea Woese et al. 1990
     Phylum Euryarchaeota Garrity and Holt 2001
       1 Class Methanobacteria Boone 2001 nom. inval. see Class Methanobacteria Boone 2002
       2 Class Methanococci Boone 2001 nom. inval. see Class Methanococci Boone 2002
       3 Class Halobacteria Grant et al. 2001 see Class Halobacteria Grant et al. 2002
       4 Class Thermoplasmata Reysenbach 2001 see Class Thermoplasmata Reysenbach 2002
       5 Class Thermococci Zillig and Reysenbach 2001 see Class Thermococci Zillig and Reysenbach 2002
       6 Class Archaeoglobi Garrity and Holt 2001 nom. inval. see Class Archaeoglobi Garrity and Holt 2002
       7 Class Methanopyri Garrity and Holt 2001 nom. inval. see Class Methanopyri Garrity and Holt 2002