Procaryotic Genera
   Domain "Bacteria" Woese et al. 1990
     Phylum Aquificae Reysenbach 2001 [monotypic]
       Class Aquificae Reysenbach 2001 nom. inval. [monotypic] see Class Aquificae Reysenbach 2002
         Order Aquificalesᵀ Reysenbach 2001 nom. inval. see Order Aquificales Reysenbach 2002
           Family Aquificaceae Reysenbach 2001 nom. inval. see Family Aquificaceae Reysenbach 2002
             1 Genus Aquifexᵀ Huber and Stetter 1992
             2 Genus Calderobacterium Kryukov et al. 1984 see Genus Hydrogenobacter Kawasumi et al. 1984
             3 Genus Hydrogenobacter Kawasumi et al. 1984
             4 Genus Thermocrinis Huber et al. 1999