procaryotes
   Domain Archaea Woese et al. 1990
     Phylum Crenarchaeota Garrity and Holt 2001
       Class Thermoprotei Reysenbach 2001 see Class Thermoprotei Reysenbach 2002
         1 Order Thermoproteales Zillig and Stetter 1982
         2 Order Desulfurococcales Huber and Stetter 2001 nom. inval. see Order Desulfurococcales Huber and Stetter 2002
         3 Order Sulfolobales Stetter 1989