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. 2024 [paraphyletic]
               Kingdom Methanobacteriati (Garrity and Holt 2023) Oren and Göker 2024
                 Phylum Methanobacteriotaᵀ Garrity and Holt 2023
                   01 Order "Candidatus Methanophagales" Borrel et al. 2021 [monotypic]
                   02 Class "Candidatus Hikarchaeia" Martijn et al. 2020 nom. pro-inval. [monotypic]
                   03 Class "Candidatus Methanofastidiosia" corrig. Nobu et al. 2020 [monotypic]
                   04 Class "Candidatus Methanoliparia" Borrel et al. 2021 [monotypic]
                   05 Class "Candidatus Ordosarchaeia" Zhao et al. 2024 nom. pro-inval. [monotypic]
                   06 Class "Candidatus Penumbrarchaeia" Maeke et al. 2025 nom. pro-inval. [monotypic]
                   07 Class "Candidatus Syntropharchaeia" Rinke et al. 2021 nom. pro-inval.
                   08 Class "Candidatus Thalassarchaeia" corrig. Martin-Cuadrado et al. 2015 nom. pro-inval. [monotypic]
                   09 Class Archaeoglobi Garrity and Holt 2002
                   10 Class Halobacteria Grant et al. 2002
                   11 Class Methanobacteriaᵀ Boone 2002 [monotypic]
                   12 Class Methanococci Boone 2002 [monotypic]
                   13 Class Methanonatronarchaeia Sorokin et al. 2018 [monotypic]
                   14 Class Methanopyri Garrity and Holt 2002 [monotypic]
                   15 Class Methanosarcinia Chuvochina et al. 2024
                   16 Class Thermococci Zillig and Reysenbach 2002 [monotypic]
                   17 Class Thermoplasmata Reysenbach 2002
                   18 Class "Methanomicrobia" Garrity et al. 2005 nom. inval.