Asian Scientist (Jul. 19, 2013) – A new study on saltwater crocodiles has thrown up new evidence suggesting that dinosaurs may be warm-blooded like birds and mammals, not cold-blooded like reptiles.
Although scientists have learnt a lot about dinosaurs from fossils, the question of whether dinosaurs were warm-blooded or cold-blooded is still a hotly debated topic simply because the fossils do not provide definitive evidence for either theory.
This new study, published in PLOS ONE, asked the question of whether a cold-blooded dinosaur could overpower a warm-blooded mammal of the same size.
To answer this question, Professor Roger Seymour, from the University of Adelaide, studied saltwater crocodiles which are cold-blooded reptiles with a reputation for being extremely powerful animals. Saltwater crocodiles can reach over a tonne in weight and have bodies which comprise about 50% muscle.
By analyzing blood and lactate measurements collected from crocodiles, Professor Seymour found that a 200 kg crocodile could produce only about 14% of the muscular power of a warm-blooded mammal at peak exercise, and this fraction seems to decrease at larger body sizes.
This suggests that cold-blooded dinosaurs would not have had the required muscular power to prey on other animals and dominate over mammals as they did throughout the Mesozoic period.
“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,” said Professor Seymour.
“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.”
His latest evidence adds to that of earlier work he did on blood flow to leg bones which concluded that the dinosaurs were possibly even more active than mammals.
Source: University of Adelaide; Photo: shvmoz/Flickr.
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