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]
           Domain Bacteria Woese et al. 1990 [paraphyletic?]
             Superphylum Terrabacteria Battistuzzi et al. 2004
               Phylum Firmicutes corrig. Gibbons and Murray 1978 (Approved Lists 1980)
                 Class Clostridia Rainey 2010
                   Order Clostridialesᵀ Prévot 1953 (Approved Lists 1980)
                     Family Peptostreptococcaceae Ezaki 2010
                       Genus Peptostreptococcusᵀ Kluyver and van Niel 1936 (Approved Lists 1980)
                         1 Peptostreptococcus anaerobiusᵀ (Natvig 1905) Kluyver and van Niel 1936 (Approved Lists 1980)
                         2 Peptostreptococcus stomatis Downes and Wade 2006
                         3 Peptostreptococcus russellii Whitehead et al. 2011