FLIGHT came early and easily to pterosaurs. Unlike birds and bats, young pterosaurs could fly soon after hatching. The reptiles were also precise flyers capable of making exquisite landings, two fossil discoveries reveal.
Before they can fly, birds must develop flight feathers and grow to almost their adult size. Bats are born with only rudimentary limbs, so they must also grow to near-adult size before taking wing. Yet pterosaurs could fly almost immediately, when their wingspan was just 10 to 20 per cent the size of an adult鈥檚, says Dave Unwin of the Natural History Museum at Humboldt University in Berlin.
A fossilised egg discovered earlier this year in China (快猫短视频, 12 June, p 15) contains a young pterosaur with long wings tightly folded inside a shell just 5 centimetres in diameter, Unwin told the conference. The newly hatched animal would have had a 27-centimetre wingspan. That, and the fact that the long wing bones solidified while the animal was still in the shell, shows the young pterosaur would have hatched ready for flight.
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That means that young pterosaurs could survive on their own almost immediately, says Unwin, and just like crocodiles and turtles, adult pterosaurs would probably have laid their eggs on the ground and provided little parental care.
That idea fits with evidence that pterosaurs grew slowly 鈥� if young pterosaurs had to fend for themselves, most of their energy would have gone into flying and catching food, leaving little spare for growth. In contrast, Unwin says, 鈥渂irds or bats in the nest are all about growing鈥�. They need devoted parents who will feed them frequently so they can reach adult size and fly as quickly as possible. Relieved of this parental responsibility, some pterosaurs grew to a giant size. They could just keep growing, albeit slowly, because they only had themselves to feed. Birds and bats would have to spend years feeding their young if they were to reach a giant adult size before they could take wing.
A fossil trackway created by a landing pterosaur also shows they were highly agile flyers. Jean-Paul Billon-Bruyat, a palaeontologist from the Swiss state of Jura, says that the trackway, discovered in France, shows that the animal slowed its flight to touch down lightly on its hind feet, dragged its toes, and then made a short hop. It then put its front legs down so it could walk away on all fours. Ducks land in a similar way, and the trackway reveals that pterosaurs could control flight so precisely that they could drop gently to the ground on two legs with little forward momentum.
