Humans have learned a lot from birds, bats, and insects as we launched our own flying machines, but we've neglected to take lessons from extinct fliers. That's a mistake, some scientists believe, since pterosaurs were the largest animals ever to take to the skies, making their aerodynamics more relevant than the comparatively puny beasts of today.
"There's a lot of really cool stuff in the fossil record that goes unexplored because engineers generally don't look to paleontology when thinking about inspiration for flight,” said Dr Liz Martin-Silverstone (known online as gimpasaura) of the University of Bristol in a statement. "If we're only looking at modern animals for inspiration, we're really missing a large degree of the morphology out there and ignoring a lot of options that I think could be useful."
Many extinct species are known only from a handful of bones, restricting our knowledge of their movements to almost nothing. However, Martin-Silverstone points out that this is not always the case. "There are two or three absolutely amazingly preserved pterosaur fossils that let you see the different layers within the wing membrane, giving us insight into its fibrous components. Also, some fossils are preserved enough to show the wing attachments beneath the hip," she said.
It is unlikely pterosaurs could compete on speed with most modern birds, but they were probably efficient low-speed fliers and such adaptions for tight locations are relevant for vehicles designed for urban uses such as landing on the roofs of high-rise buildings.
In Trends in Ecology & Evolution, the researchers extend the case beyond pterosaurs, providing an extensive review of flight modes that differ substantially from living animals. Examples from the origins of birds include Yi qi, which combined feathers with bat-like membranes, and microraptors, which although not true fliers, used membranes on both fore- and hind-limbs for highly controlled gliding. Changyuraptor had tail and hind limb feathers much longer than modern counterparts, which are thought to have allowed them to control their speed when landing.
For larger animals, the launch can be as much of a challenge as staying airborne. Some big birds need a running start, just as airplanes have to get their speed up before taking off. However, despite some pterosaurs weighing almost 300 kilograms (650 pounds), co-author Dr Mike Habib of the National History Museum of Los Angeles County thinks the strength of their wing membranes and muscle attachments may have allowed them to spring into the air with a single bound.
"Today, something like a drone requires a flat surface to launch and is quite restricted on how it actually gets into the air. The unique launch physiology of pterosaurs might be able to help solve some of these problems," Martin-Silverstone said.
Pterosaurs must also have evolved stabilizing mechanisms to avoid the risk of being upended by a gust of wind, given the vast areas their wing membranes presented. We don't yet know how they did it, but Martin-Silverstone suggests the answers could prove useful for moves towards more personalized flying.
Perhaps the flying reptiles of the dinosaur era have been overlooked when it comes to aircraft design because they are seen as failures. If so, this would be a mistake. Pterosaurs survived for 160 million years, much longer than modern birds, and were beautifully adapted for the conditions they faced. Their aeronautics were not responsible for their unpreparedness for an asteroid strike.
Moreover, new pterosaur species are being discovered all the time, with four announced within a week last month, so the opportunities to learn are plentiful.