Too heavy
Sometimes research is a useful corrective to conventional wisdom. When Dr Mark Witton, a Research Associate at Portsmouth University’s School of Earth & Environmental Sciences, and Dr Michael Habib of Chatham University, Pennsylvania, read that the largest pterosaurs were too big to fly, they knew something was missing. ‘Last year,’ says Dr Witton, ‘a study came out which said that no animal larger than 4 or 5 metres across the wings could fly, and could weigh no more than 40 kilograms. Then this year, another study came out that said that the largest pterosaurs weighed about half a ton and that would make them too heavy to fly.’

Wings
What seemed most unusual to Dr Witton, is that a pterosaur skeleton is ‘basically a pair of wings’ with a head on the front. And though they don’t have complete skeletons for the larger pterosaurs, their bodies seemed to be equally adapted for flying. ‘What’s happened in the studies suggesting that they couldn’t fly was more a misunderstanding of the mechanics of pterosaur flight, rather than their actual flight ability’ says Dr Witton.

Size and flight
Research by Dr Habib suggested that as pterosaurs get bigger, their arm bones increase in size dramatically. ‘If you scale up a small bird to a big bird, the wing bones are proportionately very similar, but that’s not the case with their leg bones at all. Their leg bones become very robust and strong and this appears to be related to take off.’ Whether it’s a pterosaur, an insect or bird, the speed and power for takeoff comes from walking limbs. This suggested to Dr Habib that pterosaurs are using their forelimbs to take off. ‘But’, says Dr. Witton, ‘he proposed this idea of the quadripedal launch, a ‘pole-vaulting’ idea. He made almost a throwaway comment in his paper saying that this may explain why some pterosaurs got so much larger than modern birds.’  In their recent paper, they explored the idea arguing that this is probably why pterosaurs can get so enormous. The largest fossil birds on record are about 7 metres across the wings, which is significantly smaller than the 10 metres across, and a quarter of a ton, which is what we think the larger pterosaurs weighed.’