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 Methanococci Boone 2002 [monotypic]
                   Order Methanococcalesᵀ Balch and Wolfe 1981
                     Family Methanocaldococcaceae Whitman et al. 2002
                       Genus Methanocaldococcusᵀ Whitman 2002
                         1 Methanocaldococcus fervens (Jeanthon et al. 1999) Whitman 2002
                         2 Methanocaldococcus indicus L'Haridon et al. 2003
                         3 Methanocaldococcus infernus (Jeanthon et al. 1998) Whitman 2002
                         4 Methanocaldococcus jannaschii (Jones et al. 1984) Whitman 2002
                         5 Methanocaldococcus villosus Bellack et al. 2011
                         6 Methanocaldococcus vulcanius (Jeanthon et al. 1999) Whitman 2002