To get around those limitations, Hirt and her colleagues looked at previously collected data for a wide variety of creatures, including ectotherms (so - called cold - blooded animals) as well as warm - blooded endotherms. (sciencemag.org)
Tuna, marlin and great white sharks heat up certain areas — swimming muscles, parts of their viscera and the eye and brain — but these regional endotherms can stay at lower depths only for short periods and must rise to warmer waters, unlike the deep - dwelling opah. (discovermagazine.com)
These rings are seen in dinosaurs, as well as in creatures such as lizards and crocodiles, whose body temperatures are regulated by the external environment, but have not often been observed in the bones of endotherms — creatures such as mammals that maintain high, constant body temperatures. (scientificamerican.com)