Did giant pterosaurs vault aloft like vampire bats?
点击量： 时间：2019-03-07 09:04:01
By Jeff Hecht If giant pterosaurs – the dinosaur-era, giraffe-sized winged reptiles – tried to fly like birds, they could not have got off the ground. Yet why would flightless pterosaurs retain giant wings instead of evolving vestigial ones like the ostrich? The answer, according to Mark Witton of the University of Portsmouth, UK, is that pterosaurs didn’t fly like birds. “We need to appreciate that pterosaurs had their own unique mechanisms of achieving flight,” he says. Pterosaurs have been extinct for 65 million years, and the largest fossils are incomplete, so there has been much argument as to how, or whether, they flew. Some have estimated that the largest weighed more than half a tonne, far more than the wings could have generated in lift. However, Witton and Mike Habib of Chatham University in Pittsburgh, Pennsylvania, have proposed that because they had short torsos, the largest pterosaurs weighed no more than 250 kilograms – and that their flight muscles were a massive 50 kilograms of that. Birds rely on the strength of their legs to leap into the air or run to gain speed for take-off. Pterosaurs walked on all four limbs, and Habib has developed an anatomical model to explore how they might have launched themselves using their small hind limbs and larger “arms” which formed part of their wings. The animal could have launched itself like a pole vaulter, pushing forward with its hind limbs and using its powerful arms to thrust it high enough into the air to stretch its wings and fly away. Vampire bats take off in this way. Witton and Habib say that wings of the giant pterosaurs were so powerful that the vaulting mechanism could have launched them from a small clearing without the need for a “runway” or a cliff to leap from. Instead of being fragile, marginal flyers, they say, pterosaurs could flap their wings to reach speeds of 120 kilometres per hour for a couple of minutes, then glide at 90 kilometres per hour, covering thousands of kilometres, says Witton. “Their skeletons are one of the most robust things that ever evolved.” Journal reference: PLoS One, DOI: 10.1371/journal.pone.0013982 When this article was originally posted, we incorrectly stated that Mike Habib is at Johns Hopkins University. More on these topics: