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