Small heads, large bodies, and a slow metabolism — these are the characteristics that make us think of dinosaurs as dull, lethargic and cold-blooded giants. However, this image seems to be deceiving. These giant saurians that have been extinct for 65 million years may have been high-performance models of evolution. Researchers have now determined that the body temperature of some large herbivorous dinosaurs was between 36 and 38 degrees Celsius.