You may have heard the saying, “Like a cold blooded reptile.” Well according to research at the University of Adelaide in Australia, that doesn’t apply to the ancient dinosaurs anymore.
In PLoS ONE Journal, Professor Roger Seymour of the University’s School of Earth and Environmental Sciences, says 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, which was 252 to 66 million years ago.
The era began in the wake of the Permian–Triassic extinction event, which is known as the largest well-documented mass extinction in the history of the Earth, and ended with the Cretaceous–Paleogene extinction event, another mass extinction where non-avian dinosaurs, as well as other plant and animal species were killed off.
The Mesozoic was a time of major tectonic, climate and evolutionary activity. The era had witnessed the gradual rifting of the supercontinent Pangaea into separate landmasses, (that would eventually move into their current positions we know them as today). The climate of the Mesozoic varied, alternating between warming and cooling periods. Overall, however, the Earth was hotter than it is today. This is also in line with Professor Seymour’s theory.
He indicates, “Some point out that a large saltwater crocodile can achieve a body temperature above 30°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.”
In his paper, Professor Seymour then questions how much muscular power could be produced by a crocodile-like dinosaur compared to a mammal-like dinosaur of the same size. Saltwater crocodiles reach over a ton in weight and are about 50% muscle, so they have a pretty big reputation for being powerful animals.
By drawing from blood and muscle lactate measurements collected by his collaborators at Monash University, University of California and Wildlife Management International in the Northern Territory, Professor Seymour was able to demonstrate that a 200 kg. crocodile can only produce about 14% of the muscular power of a mammal at peak exercise, and even this seems 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,” states Professor Seymour.
He goes on to say, “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.”
This still largely debated topic is argued both ways for our massive ancient friends. What do you think, were dinosaurs warm or cold?