Dinosaurs could have been hot to trot, sayUS scientists

Published on Tuesday 10 November 2009 21:57

LARGE two-legged dinosaurs, such as Tyrannosaurus rex, were energetic athletes with warm blood running through their veins, it was claimed today.

New evidence suggests that the ancient reptiles were endothermic – or warm-blooded – like their modern descendants, birds.

Far from being lumbering slow beasts, they were likely to have been agile and active.

But warm blood would have come at a price, because it requires more food. If food became scarce 65 million years ago, this could have been a contributory factor in their extinction.

US scientists, led by Dr Herman Pontzer at the University of Washington, based their findings on the estimated amount of energy dinosaurs must have expended in moving around.

Recent research by Dr Pontzer has shown the energy cost of walking and running is strongly associated with leg length. Hip height – the distance from the hip joint to the ground – can predict the observed cost of locomotion, with 98 per cent accuracy for a wide range of land animals.

Dr Pontzer's team applied this principle to an analysis of fossilised dinosaur leg bones.

The scientists also calculated the actual volume of leg muscle that dinosaurs would have had to activate in order to move.

After studying 14 species, the researchers concluded that simply walking and running required too much energy for larger bipedal dinosaurs to have been cold-blooded.

Having warm blood and a high metabolic rate may have contributed to the evolutionary success dinosaurs enjoyed for hundreds of millions of years throughout the Triassic, Jurassic and Cretaceous periods.