The argument over whether dinosaurs were warm-blooded 'endotherms', like today's mammals, or cold-blood 'ectotherms', like lizards, has raged almost since the day when the first fossils were classified more than a century ago. Endotherms have high metabolic rates to generate internal heat and can operate in a variety of outside temperatures. Lizards and other ectotherms, however, have to warm themselves up by lying in the sun.
Researchers who have analysed the chemical composition of bones from a well-preserved T. rex believe they have found the strongest evidence yet that dinosaurs, which ruled the world for 163 million years before becoming extinct 65 million years ago, were indeed warm-blooded.
By comparing phosphates from the bones in the trunk of the animal with bones taken from the extremities, such as legs, scientists from North Carolina State University in Raleigh, North Carolina, found the body temperature of T. rex remained fairly constant.
They also believe the temperature difference between the two parts of the animal was no more than 4C, about the same as the variation seen in a large warm- blooded mammal. Their findings are reported in the current issue of the scientific journal Science.