[organisms] see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   Domain Bacteria Woese et al. 1990 stat. inval. see Domain Bacteria Woese et al. 2024
     Phylum Firmicutes (Gibbons and Murray 1978) Garrity and Holt 2001 stat. inval. see Phylum Bacillota Gibbons and Murray 2021
       Class "Clostridia" "Garrity and Holt 2001" nom. nud. see Class Clostridia Rainey 2010
         Order Clostridiales Prévot 1953 (Approved Lists 1980) see Order Eubacteriales Buchanan 1917 (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