Warm-blooded animal

Warm-blooded animal, or homoiotherm, animal whose body temperature is not dependent on external temperature but is maintained at a constant level by internally generated metabolic heat. This constant temperature enables the chemical processes of the body, many of them temperature dependent, to be more efficient. Mammals and birds have developed this homoiothermy, and it is now believed that pterodactyls, therapsids, and many other extinct reptiles may also have been warm-blooded.