[organisms] see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   Domain Bacteria Woese et al. 1990
     Phylum Firmicutes corrig. Gibbons and Murray 1978 (Approved Lists 1980)
       Class "Clostridia" Garrity et al. 2001 nom. ined. see Class Clostridia Rainey 2010
         1 Order Clostridiales Prévot 1953 (Approved Lists 1980)
         2 Order "Thermoanaerobacteriales" see Order Thermoanaerobacterales Wiegel, 2010
         3 Order Halanaerobiales corrig. Rainey and Zhilina 1995