prokaryotes - bacteria see Domain Bacteria Woese et al. 1990
   Domain "Bacteria" Woese et al. 1990
     Phylum "Thermotogae" Reysenbach 2001 [monotypic]
       Class Thermotogae Reysenbach 2002
         Order Petrotogales Bhandari and Gupta 2014 [monotypic]
           Family Petrotogaceae Bhandari and Gupta 2014
             1 Genus Defluviitoga Ben Hania et al. 2012
             2 Genus Geotoga Davey et al. 1993
             3 Genus Marinitoga Wery et al. 2001
             4 Genus Oceanotoga Jayasinghearachchi and Lal 2011
             5 Genus Petrotoga Davey et al. 1993