Kingdom Bacteria Cavalier-Smith 2002 stat. inval. [paraphyletic?] - bacteria see Domain Bacteria Woese et al. 1990 stat. inval.
   Subkingdom Unibacteria Cavalier-Smith 2002 [paraphyletic?] see Domain Bacteria Woese et al. 1990 stat. inval.
     Division Archaebacteria Cavalier-Smith 2002 see Domain Archaea Woese et al. 1990 stat. inval.
       Subdivision Crenarchaeota Cavalier-Smith 2002 [monotypic] see Phylum Crenarchaeota Garrity and Holt 2002 stat. inval.
         Class Crenarchaeota Cavalier-Smith 2002 nom. rej. see Class Thermoprotei Reysenbach 2002
           1 Order Thermoprotealesᵀ Zillig and Stetter 1982
           2 Order Sulfolobales Stetter 1989
           3 Order Desulfurococcales Huber and Stetter 2001 nom. inval. see Order Desulfurococcales Huber and Stetter 2002
           4 Order Cenarchaeales Cavalier-Smith 2002 nom. inval., nom. rej. see Order Nitrosopumilales Qin et al. 2017