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?]
             Phylum Aquificae Reysenbach 2001 [monotypic]
               Class Aquificaeᵀ Reysenbach 2002
                 Order Aquificalesᵀ Reysenbach 2002
                   Family Aquificaceaeᵀ Reysenbach 2002
                     Genus Hydrogenivirga Nakagawa et al. 2004
                       1 Hydrogenivirga caldilitorisᵀ Nakagawa et al. 2004
                       2 Hydrogenivirga okinawensis Nunoura et al. 2008