[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
         Order Clostridiales Prévot 1953 (Approved Lists 1980)
           Family Syntrophomonadaceae Zhao et al. 1993
             Genus Caldicellulosiruptor Rainey et al. 1995
               1 Caldicellulosiruptor kristjanssonii Bredholt et al. 1999
               2 Caldicellulosiruptor acetigenus (Nielsen et al. 1994) Onyenwoke et al. 2006
               3 Caldicellulosiruptor lactoaceticus Mladenovska et al. 1997
               4 Caldicellulosiruptor owensensis Huang et al. 1998
               5 Caldicellulosiruptor saccharolyticus Rainey et al. 1995