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]
           Clade neomura Cavalier-Smith, 1987
             Domain Archaea Woese et al. 1990 [paraphyletic]
               Phylum Euryarchaeota Garrity and Holt 2001
                 Class Thermococci Zillig and Reysenbach 2002 [monotypic]
                   Order Thermococcalesᵀ Zillig 1988 [monotypic]
                     Family Thermococcaceaeᵀ Zillig 1988
                       1 Genus Thermococcusᵀ Zillig 1983
                       2 Genus Palaeococcus Takai et al. 2000
                       3 Genus Pyrococcus Fiala and Stetter 1986