procaryotes Domain Archaea Woese et al. 1990 Phylum Crenarchaeota Garrity and Holt 2001 Class Thermoprotei Reysenbach 2001 see Class Thermoprotei Reysenbach 2002 Order Sulfolobales Stetter 1989 Family Sulfolobaceae Stetter 1989 Genus Metallosphaera Huber et al. 1989