procaryotes Domain Archaea Woese et al. 1990 Phylum Crenarchaeota Garrity and Holt 2001 Class Thermoprotei Reysenbach 2001 see Class Thermoprotei Reysenbach 2002 Order Desulfurococcales Huber and Stetter 2001 nom. inval. see Order Desulfurococcales Huber and Stetter 2002 Family Pyrodictiaceae Burggraf et al. 1997 Genus Hyperthermus Zillig et al. 1991