[organisms] see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   Domain "Archaea" Woese et al. 1990
     Phylum "Euryarchaeota" Garrity and Holt 2001
       Class "Methanomicrobia"
         Order Methanomicrobiales Balch and Wolfe 1981
           Family Methanomicrobiaceae Balch and Wolfe 1981
             Genus Methanogenium Romesser et al. 1981
               1 Methanogenium cariaci Romesser et al. 1981
               2 Methanogenium frigidum Franzmann et al. 1997
               3 Methanogenium marinum Chong et al. 2003
               4 Methanogenium organophilum Widdel et al. 1989