From: Andy Soos, ENN
Published November 24, 2010 10:33 AM

Pterodactyl Flight

Pterodactyl are not giant birds and indeed if they were, they might not even be able to fly based on standard theories of flight. Some have proposed that they vaulted and then glided on the winds. These ancient reptiles that flew over the heads of dinosaurs — were at their best in gentle tropical breezes, soaring over hillsides and coastlines or floating over land and sea on thermally driven air currents, according to new research from the University of Bristol. Pterodactyls) were too slow and flexible to use the stormy winds and waves of the southern ocean like the albatrosses of today states the research by Colin Palmer, an engineer turned paleontology PhD student in Bristol’s School of Earth Sciences.

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The anatomy of pterosaurs (pterodactyls) was highly modified from their reptilian ancestors for the demands of flight. Pterosaur bones were hollow and air filled, like the bones of birds. They had a keeled breastbone that was developed for the attachment of flight muscles and an enlarged brain that shows specialized features associated with flight.

Their slow flight and the variable geometry of their wings also enabled pterosaurs to land very gently, reducing the chance of breaking their paper- thin bones.  This helps to explain how they were able to become the largest flying animals ever known.  Some had wing spans over 30 feet and were far larger than other known flying creatures

Currently the bird with the largest wingspan is the albatross.  Their wingspan reaches 11 feet.  Albatrosses travel huge distances with two techniques used by many long-winged seabirds, dynamic soaring and slope soaring. Dynamic soaring involves repeatedly rising into wind and descending downwind thus gaining energy from the vertical wind gradient. Slope soaring uses the rising air on the windward side of large waves.  

Using his 40 years of experience in the engineering industry, Colin Palmer constructed models of pterosaur wing sections from thin, curved sheets of epoxy resin/carbon fiber composite and tested them in a wind tunnel.  These tests quantified the two-dimensional characteristics of pterosaur wings for the first time, showing that such creatures were significantly less aerodynamically efficient and were capable of flying at lower speeds than previously thought.

Colin Palmer said: “Pterosaur wings were adapted to a low-speed flight regime that minimizes sink rate.  This regime is unsuited to marine style dynamic soaring adopted by many seabirds which requires high flight speed coupled with high aerodynamic efficiency, but is well suited to thermal/slope soaring.  The low sink rate would have allowed pterosaurs to use the relatively weak thermal lift found over the sea.

"Since the bones of pterosaurs were thin-walled and thus highly susceptible to impact damage, the low-speed landing capability would have made an important contribution to avoiding injury and so helped to enable pterosaurs to attain much larger sizes than extant birds.  The trade-off would have been an extreme vulnerability to strong winds and turbulence, both in flight and on the ground, like that experienced by modern-day paragliders."

The research is published today in Proceedings of the Royal Society B.

For further information:  http://www.bristol.ac.uk/news/2010/7335.html

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