New simulations of pterosaur flight reveal why these winged reptiles never reached monstrously large proportions: Tricky take-offs. Not that they were small by any means; some species had wingspans of up to 10 meters and weighed hundreds of kilograms. But a pterosaur with a wingspan of 12 meters or more would be permanently grounded.
Combining engineering with analyses of biological systems, Colin Palmer of Bristol University and Mike Habib from the University of Southern California used 3D imaging of fossils to create a computer model pterosaur with a small, six-meter wingspan and wings made of flexible membrane. They scaled this guy up to create nine-meter and 12-meter wingspan models, which helped the duo estimate the wing strength, flexibility, flying speed, and power that would be required for flight.
Even the most massive pterosaur modeled could sustain flight just fine, using powered flight sporadically to find air currents that allowed for smooth gliding. This behemoth could even slow down properly for safe landings. Take-offs, however, were another story.
Unlike birds who propel themselves by running and flapping their wings, the anatomy of pterosaurs suggests that they used both their arms and legs to push themselves off the ground. This four-limbed maneuver is called the “quadrupedal launch.” When the simulated wingspans reached a dozen meters—and the animal approached 400 kilograms—the push-off force required was just too great to get it off the ground.
"Getting into the air ultimately limited pterosaur size,” Palmer explains in a news release. “Even with their unique four legged launch technique, the iron laws of physics eventually caught up with these all time giants of the cretaceous skies.”
The findings were presented at the Society of Vertebrate Paleontology meeting in Berlin this week.
Images: Mark Witton
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