Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         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. 2001 nom. inval.] see Family Methanocaldococcaceae Whitman et al. 2002
                       1 [Genus "Methanocaldococcus"ᵀ Whitman 2001 nom. inval.] see Genus Methanocaldococcus Whitman 2002
                       2 [Genus "Methanotorris" Whitman 2001 nom. inval.] see Genus Methanotorris Whitman 2002