Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         [crown] Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
           Domain Bacteria Woese et al. 1990 [paraphyletic?]
             Superphylum Terrabacteria Battistuzzi et al. 2004
               Phylum Firmicutes corrig. Gibbons and Murray 1978 (Approved Lists 1980)
                 Class Clostridia Rainey 2010
                   Order Thermoanaerobacterales Wiegel 2010
                     1 Genus Caldanaerovirga Wagner et al. 2009, incertae sedis [monotypic]
                     2 Genus Caldicellulosiruptor Rainey et al. 1995, incertae sedis
                     3 Genus Syntrophaceticus Westerholm et al. 2011, incertae sedis
                     4 Genus Thermovorax Mäkinen et al. 2012, incertae sedis
                     5.1 Genus Mahella Bonilla Salinas et al. 2004, incertae sedis [monotypic]
                     5.2 Genus Thermoanaerobacterium Lee et al. 1993, incertae sedis
                     5.3 Genus Thermosediminibacter Lee et al. 2006, incertae sedis
                     5.4 Genus Thermovenabulum Zavarzina et al. 2002, incertae sedis [monotypic]
                     6 Family Thermoanaerobacteraceaeᵀ Wiegel 2010
                     7 Family Thermodesulfobiaceae Mori et al. 2004