A few
Euryarchaeotes thrive in thermal environments and some are extremely thermophilic; those with growth temperature optima over 80°C are called hyperthermophiles.
Two of these organisms,
Thermococcus and
Pyrococcus, show phenotypic properties very similar to those of hyperthermophilic
crenarchaeotes and form a distinct order: the
Thermococcales.
Taken from the text Brock Biology of Microorganisms (10th ed.). Madigan, M.T., Martinko, J.M., and Parker, J. 2003. Prentice Hall. 458p.