November 16, 2010

Ancient Pterosaurs “˜Pole Vaulted’ Into Air

A new study finds that ancient pterosaurs took flight by "pole-vaulting" using all four of their limbs.

The winged reptiles vaulted over their wings, initially pushing off with their hind limbs and then thrusting themselves upwards with their strong arm muscles, the researchers said.

Pterosaurs roamed the Earth at the same time as the dinosaurs, existing from about 220 million to 65 million years ago from the Triassic Period until the end of the Cretaceous. 

The study's findings challenge previous beliefs that giant pterosaurs such as Pteranodon and azhdarchids were too heavy to fly. 

The study was conducted by Mark Witton at Portsmouth University in Britain and Michael Habib of Chatham University, Pennsylvania, who reassessed fossils of the massive pterosaur.

"Most birds take off either by running to pick up speed and jumping into the air before flapping wildly, or if they're small enough, they may simply launch themselves into the air from a standstill," Dr. Witton told BBC News.

"Previous theories suggested that giant pterosaurs were too big and heavy to perform either of these maneuvers."

There were doubts over whether the winged pterosaurs could have taken off using the same mechanisms as birds.

However, pterosaurs "were not birds; they were flying reptiles with a distinctly different skeletal structure, wing proportions and muscle mass," Dr. Witton explained.

"They would have achieved flight in a completely different way to birds and would have had a lower angle of take off and initial flight trajectory."

The scientists suggested that with such powerful forelimb muscles, the pterosaurs could easily have launched themselves into the air despite their massive size and weight.

"Instead of taking off with their legs alone, like birds, pterosaurs probably took off using all four of their limbs," said Dr. Habib.

"By using their arms as the main engines for launching instead of their legs, they use the flight muscles - the strongest in their bodies - to take off and that gives them potential to launch much greater weight into the air."

"When they were far enough off the ground, they could start flapping their wings before finding a thermal or another area of uplift to gain some altitude and glide off to wherever they wanted to go," he told BBC News.

Although the pterosaurs lived at the same time as the dinosaurs, they belonged to a different group of reptiles.  

Scientists had previously believed the largest pterosaurs may have had wingspans up to 40 feet wide, and weighed as much as 1,220 lbs. 

However, the scientists' reappraisal of pterosaur fossils suggests these numbers may have been overestimated. Rather, they claim that the largest pterosaur may have had 30 to 33 foot wingspans and weighed between 440 and 550 lbs.

The research was published in the journal PLoS One.  The full report can be viewed here.

Image Courtesy Mark Witton (http://www.flickr.com/photos/markwitton)