wings 'key to their size'
Ancient flying reptiles called pterosaurs were adapted to fly in a
slow, controlled manner in gentle tropical breezes, researchers say.
Their conclusions are drawn from the first detailed aerodynamic study
of the wings, which suggests they did not evolve to fly fast and
powerfully in stormy winds.
The research, published in the Proceedings of the Royal Society, may
also explain how the creatures were able to become the largest flying
animals ever known. By landing slowly, the pterosaurs could avoid injury
and grow to much larger sizes than modern day birds. However, the
trade-off for their large size was a vulnerability to strong winds.
known as pterodactyls, these creatures lived at the time of the
dinosaurs. Some species are thought to have had wingspans of up to 10m.
Although there is a wealth of information about the bones of these
creatures - no one really knows how they flew. But a fresh look at the
problem by a 62 year-old former engineer in Bristol working on a PhD
thesis suggests that they glided gently on tropical breezes, soared by
hillsides and coastlines and floated on thermal air currents.
Colin Palmer had a simple idea that hadn't occurred to more eminent
palaeontologists: To build models of pterosaur wings and put them into a
"I come at this conclusion as an engineer rather than a
palaeotologist," Palmer told BBC News.
The results from the PhD study have been so impressive that they been
published in one of the Royal Society's prestigious scientific journals.
The front edge of the Pterosaur wing is bone. Palmer found in his wind
tunnel experiments that this caused drag. making it aerodynamically less
efficient than the wings of birds - which use feathers to create a
smoother leading edge. Palmer reasoned that pterosaurs flew in a slow,
controlled way, in particular when they came in to land. That would be
important to pterosaurs because they had very thin bones which,
according to Palmer, could break on landing.
It's thought that these creatures controlled their flight by
adjusting the curvature of their wings.This enabled them to generate
lift and so fly under control at lower speeds. The wind tunnel results
show that pterosaur wings were able to provide them with the soft
landing that their large, fragile bodies needed.
"This is the first time this has been done," says Palmer. "Previously
data has been taken from the aerodynamic literature and adapted it as
best they could to make predictions of pterosaur flight performance. Now
for the first time we've got data from (models of pterosaur wings).
Some palaeontologists had suggested that pterosaurs might have flown
like modern day albatrosses which fly very fast and efficiently in
strong winds. Albatrosses make use of a technique called dynamic soaring
where they make use of the strong winds and wind gradients in the
southern ocean. In order to do that you have to fly very fast and very
efficiently - neither of which pterosaurs were capable, according to the
wind tunnel data.Instead it shows they were much better adapted to
flying in at gentle breezes of the tropics and using the lift you get
from rising air currents as they come from the sea on to the land and
also the thermal lift you get in tropical areas.
Palmer commented: "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
Palmer says he's surprised and pleased that his first time effort at
academic research has been a hit.