procaryotes
   Domain Archaea Woese et al. 1990
     Phylum Crenarchaeota Garrity and Holt 2001
       Class Thermoprotei Reysenbach 2001 see Class Thermoprotei Reysenbach 2002
         Order Thermoproteales Zillig and Stetter 1982
           Family Thermofilaceae Burggraf et al. 1997
             1 Genus Thermofilum Zillig and Gierl 1983