Washington, April 29 : A new study has suggested that animals heavier than 41 kilograms with wingspans greater than 16.7 feet wouldn't be able to flap fast enough to stay aloft, which indicates that giant Pterosaurs couldn't fly.

According to a report in National Geographic News, the conclusion casts serious doubt on the flying ability of large pterosaurs such as Quetzalcoatlus, thought to be one of the largest airborne animals of all time.

The late-Cretaceous creature may have weighed up to 551 pounds (250 kilograms) and had up to a 34.1-foot (10.4-meter) wingspan-nearly as wide as a schoolbus is long.

"I think that the giant pterosaurs could not stay aloft in an environment similar to the present," said study leader Katsufumi Sato, an associate professor at the University of Tokyo's Ocean Research Institute.

"Even if they could stay up, the bulky beasts would have had trouble getting off the ground in the first place," Sato said.

"Takeoff is the hardest task. I suppose they could not take off using only muscular efforts," he added.

For his research, Sato journeyed to the southern Indian Ocean to study the world's largest bird, the wandering albatross, and four smaller bird species.

All five species are considered to be soaring birds-flyers that use a strategy of gliding punctuated by sporadic flapping, as pterosaurs are generally thought to have flown.

The researcher outfitted 26 birds with tiny accelerometers, which collected data on their flapping speeds from takeoff to landing.

Comparing the data across species, Sato found that the flapping speeds required for a bird to take off and then stay cruising are linked to its body size.

He and his team calculate that 10 kilograms-the weight of a large wandering albatross-is the "pragmatic limit" for safe and sustainable flight in variable wind conditions.

Sato's findings also suggest that, in theory, a soaring flyer can weigh no more than 41 kilograms with a wingspan no wider than 16.7 feet.

According to Sato, it's possible heavy pterosaurs overcame their difficulties during takeoff by launching themselves from high places such as trees or cliffs.

But, if pterosaurs really were capable of sustained flight, "we must think about the possibility of drastic change in other environmental factors, such as much lighter gravity or much denser air over geological time," he said. (ANI)