Runway reveals how pterodactyls land
Palaeontologists have just identified the world's first known landing runway for a pterosaur.
This prehistoric flying reptile was so powerful that it needed several steps when landing to stop its forward momentum, according to a new study.
The trackway, described in the latest Proceedings of the Royal Society B, provides a rare look at how these dinosaur-era animals behaved. It reveals nearly every move the pterosaur made after it took to the Late Jurassic skies - 161 to 145 million years ago.
Upon landing, the pterodactyl first touched the ground with both clawed hind feet, according to the researchers.
"The initial claw impressions coming out of the first parallel set of prints show that the claws were dragged a bit along the ground as the animal came forward out of this first set," says co-author Professor Kevin Padian. "The fact that they're parallel shows that they're being impressed together."
Padian is curator of Museum of Palaeontology at the University of California at Berkeley.
He and colleagues Dr Jean-Michel Mazin and Jean-Paul Billon-Bruyat identified the pterosaur landing trackway after studying the fossilised footprints at the Late Jurassic site known as 'Pterosaur Beach', located near Crayssac, France.
Padian says Pterosaur Beach was once "the edge of a lagoon with a very gentle, almost imperceptible slope [with] light-colour fine mud on top of slightly coarser sands."
The researchers determined that after the pterosaur landed on this lagoon edge with both feet, dragging its clawed toes, it became slightly airborne before touching ground again with its hind feet.
Next, the pterosaur placed its winged forelimbs on the ground, took another short step with its back legs, adjusted its forelimbs and then began to walk off normally.
All of these moves appear in sequence on the trackway, illustrating how the flying reptile worked off its forward momentum.
Padian and his team believe this was not a large pterodactyl. The tracks suggest its feet were only around two inches long. Some pterosaurs were enormous, with wingspans up to 10 metres.
The pterosaur's landing resembled that of common merganser ducks and other modern birds. The pterodactyl was likely a powerful flyer with highly manoeuvrable wings and a developed capacity for flight control.
The findings confirm earlier speculation by R J Templin, retired head of the Canadian National Research Council's Aerodynamics Laboratory. He and his colleagues previously determined that pterosaurs possessed what they call "smart wings."
"The fourth finger could be moved backward considerably, morphing the wing shape to change speed," they concluded. "Wing anatomy also suggests they functioned as sophisticated flight sensor devices."
Templin and his team believe "these dragons of the air" could even teach today's aircraft designers a thing or two. Larger pterosaurs, weighing up to 70 kilograms, did have wingspans comparable to those of a small passenger jet.
What's now missing from the pterosaur picture is how these animals took off, but Padian already has some ideas.
"Two obvious choices are just jumping up and flapping, and running along and flapping," says Padian. "I suspect both were possible."