Were Dinosaurs Warm Blooded?
July 19, 2013

Were Dinosaurs Warm-Blooded? New Research Indicates They Were

April Flowers for redOrbit.com - Your Universe Online

Modern reptiles are cold-blooded, and many researchers maintain dinosaurs were as well. New research from the University of Adelaide, however, suggests dinosaurs may have been warm-blooded like birds and mammals.

Professor Roger Seymour of UA's School of Earth and Environmental Sciences argues cold-blooded dinosaurs would have been unable to develop the necessary muscle power to prey on other animals and dominate over mammals as they did in the Mesozoic era.

"Much can be learned about dinosaurs from fossils but the question of whether dinosaurs were warm-blooded or cold-blooded is still hotly debated among scientists," says Seymour.

"Some point out that a large saltwater crocodile can achieve a body temperature above 30 degrees C by basking in the sun, and it can maintain the high temperature overnight simply by being large and slow to change temperature.

"They say that large, cold-blooded dinosaurs could have done the same and enjoyed a warm body temperature without the need to generate the heat in their own cells through burning food energy like warm-blooded animals."

Seymour's study, published in the open-access journal PLOS ONE, asks how much muscle power a crocodile-like dinosaur could have generated compared to a warm-blooded dinosaur of the same size.

Modern saltwater crocodiles can weigh over 2,000 pounds. Approximately 50 percent of their weight is muscles, making them extremely powerful animals.

Using blood and muscle lactate measurements collected by researchers at Monash University, University of California and Wildlife Management International in the Northern Territory, Seymour was able to show that a 440-pound crocodile produces approximately 14 percent of the muscular power of a mammal at peak exercise. What's more, this percentage appears to decrease at larger body sizes.

"The results further show that cold-blooded crocodiles lack not only the absolute power for exercise, but also the endurance, that are evident in warm-blooded mammals," Seymour explained.

"So, despite the impression that saltwater crocodiles are extremely powerful animals, a crocodile-like dinosaur could not compete well against a mammal-like dinosaur of the same size. Dinosaurs dominated over mammals in terrestrial ecosystems throughout the Mesozoic. To do that they must have had more muscular power and greater endurance than a crocodile-like physiology would have allowed."

Seymour's previous research concerned blood flow to leg bones, concluding that the dinosaurs were possibly even more active than mammals, adding to the evidence that dinosaurs were warm-blooded.