Domain Bacteria Woese et al. 1990
   Phylum Thermotogae Margulis and Schwartz 1998 - thermophilic fermenters see Phylum Thermotogae Reysenbach 2001
     Class Thermotogae Reysenbach 2001 see Class Thermotogae Reysenbach 2002
       Order Thermotogales Reysenbach 2001 see Order Thermotogales Reysenbach 2002
         Family Thermotogaceae Reysenbach 2001 see Family Thermotogaceae Reysenbach 2002
           Genus Fervidobacterium Patel et al. 1985
           Genus Geotoga Davey et al. 1993
           Genus Petrotoga Davey et al. 1993
           Genus Thermosipho Huber et al. 1989
           1 Genus Thermotoga Stetter and Huber 1986