Domain Archaea Woese et al. 1990
   Phylum Euryarchaeota Garrity and Holt 2001
     Class Thermoplasmata Reysenbach 2001 see Class Thermoplasmata Reysenbach 2002
       Order Thermoplasmatales Reysenbach 2001 see Order Thermoplasmatales Reysenbach 2002
         1 Family Thermoplasmataceae Reysenbach 2001 see Family Thermoplasmataceae Reysenbach 2002
         2 Family Picrophilaceae Schleper et al. 1996