Organisms in the order Desulfurococcales are the most thermophilic of all known
Archaea; those found in submarine volcanic habitats. These habitats include both shallow water thermal springs and deep-sea hydrothermal vents.
Taken from the text Brock Biology of Microorganisms (10th ed.). Madigan, M.T., Martinko, J.M., and Parker, J. 2003. Prentice Hall. 466p.