Pterosaurs, such as pterodactyl, are some of the largest animals ever to have taken to the skies, but the first reptile aviators were clumsy flyers, only capable of travelling short distances, a study suggests. The research may also shed new light on the evolution of flight more generally.
Pterosaurs evolved around 245m years ago, and dominated the skies for more than 150m years, before dying out at the end of the Cretaceous period along with many of their dinosaur cousins. With long membranous wings stretching from the ankles to an elongated fourth finger, pterosaurs are considered the earliest vertebrates to have evolved powered flight. But what did these first flights look like?
Prof Chris Venditti, a lecturer in evolutionary biology at the University of Reading, and his colleagues estimated the wing size and body mass of various pterosaurs from their fossilised remains, and combined this with information about the metabolic rates of birds to calculate how much energy pterosaurs would have needed to fly, and how far they could have glided before dropping to the ground.
This revealed that, though airborne, the earliest pterosaurs are likely to have been ungainly aviators. “They would have been flying, but relatively clumsily. They may have been climbing up trees and flying from one trunk to another, but not flying very long distances and not very agile in their flight,” said Venditti, whose research was published in Nature.
Later pterosaurs were not only bigger, but their wings gradually became longer relative to their size, increasing their efficiency: “They would have been big and graceful flyers that soared through the air, maybe even migrating hundreds of kilometres,” Venditti said.
The research may also shed light on the evolution of flight in vertebrates more generally. Creatures like birds and bats arrived after the pterosaurs died out, and relatively little is known about how they took to the skies either.
“I think people assume that flying magically bursts on to the scene, but there’s a big energetic hill to overcome in order to fly,” said Venditti. “Here we see that that energetic hill was overcome, and then these animals continued to get better at it. I don’t think that’s known for birds, and it will be interesting to see whether this is a general phenomenon or not.”
Not all pterosaurs mastered the art of graceful flight, however. Venditti found that a group of gigantic Cretaceous pterosaurs called the azhdarchoids remained clumsy flyers with relatively short wings for their size - possibly because flight efficiency was less important to them than to other pterosaurs.
This included the enormous, North American pterosaur Quetzalcoatlus, which was as tall as a giraffe and as wide as a light aircraft. “There’s no doubt that they could fly, but they probably only did so when they had to,” Venditti said.
