A new study has revealed that giant reptiles that lived in the dinosaur-era seas might have been warm-blooded.
Researchers found that ancient ocean predators could possibly control their body temperatures, which allowed for aggressive hunting, deep diving, and fast swimming over long distances.
"These marine reptiles were able to maintain a high body temperature independently of the water temperature where they lived, from tropical to cold-temperate oceanic domains," National Geographic News quoted study co-author Christophe Licuyer, a paleontologist at Universiti Claude Bernand Lyon 1 in France, as saying.
Although modern reptiles and fishes are cold blooded, the modern ocean's top predators like tuna and swordfish are to some degree warm-blooded - this made the team wonder if ancient marine reptiles might have been, too, Licuyer said.
Scientists studied the fossil teeth of fish that would have lived alongside these creatures, to determine the teeth's oxygen isotopes, which in turn indicate those of the blood - and hence animals' body temperatures. After comparing these results with oxygen-isotope compositions in modern-day fish, the team figured out the ocean temperatures of the ancient species' habitat.
The ancient reptiles' higher body temperatures also suggest the animals may have possessed heat-conservation systems, such as blubber layers and specialized blood circulation, said Ryosuke Motani, a vertebrate paleontologist at the University of California, Davis.
"From here we can really begin to investigate how this might have evolved," said Motani, who was not involved in the new research.
"These [sea reptiles] all came from land reptiles, who we're pretty sure were so-called cold-blooded, and it was probably the same when they started swimming. But over time it looks like homeothermy evolved, and so we need to figure out when that happened and why," he said.
"Maybe it evolved as they became better at cruising, or [because] there were changes in average temperature or in sea level."
The study will be published tomorrow in the journal Science. (ANI)