Image by William James Warren, Science Faction/Corbis Images

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A radio-controlled model of Quetzalcoatlus northropi, digitally superimposed over a picture of the sun.

Image by William James Warren, Science Faction/Corbis Images

Giant Pterosaurs Could Fly 10,000 Miles Nonstop

Reptiles burned fat stores equal to a "good-size human" each trip, expert says.

Large pterosaurs may have been the frequent-flier champions of the dinosaur age, capable of soaring up to 10,000 miles (16,000 kilometers) at a stretch, scientists say (explore a prehistoric time line).

Currently paleontologists know of four species of giant pterosaur, some of which were as tall as giraffes and had wingspans of more than 30 feet (10 meters).

The huge animals likely relied on updrafts of warm air and wind currents to achieve their record distances, said study co-author Michael Habib, a paleontologist at Chatham University in Pittsburgh.

"They probably only flapped for a few minutes at a time ... and then their muscles had to recover," he said. "In between, they're going to use unpowered flight" and glide. (Related: "Toothy Texas Pterosaur Discovered; Soared Over Dallas.")

Even so, the winged reptiles would have needed to burn about 160 pounds (72 kilograms) worth of fat reserves per trip, Habib said.

"They're basically burning off the equivalent of a good-size human on each trip."

Bulky Pterosaurs Launched From All Fours

The new flight distance estimate for pterosaurs is based on the latest models of the ancient animals' wingspans, wing shapes, body masses, and fat capacities.

"The tricky part was deciding how much fuel they can carry," Habib said. For example, "migrating birds lose about 50 percent of their body weight during long migrations."

But the needs of pterosaurs may have been different, because their anatomy suggests they flew differently than modern-day birds. (Take an animal-migrations quiz.)

For instance, scientists had previously used the largest living bird, the wandering albatross, to model pterosaur flight. But "we don't expect [pterosaurs] to have the same flapping frequency as an albatross, nor do we expect that they soared the same way as an albatross," Habib said.

The 10,000-mile flight estimate may even be a little conservative, said Habib, who presented his work this week at the annual Society for Vertebrate Paleontology meeting in Pittsburgh.

"The lowest range estimates were about 5,000 miles (8,000 kilometers), while the highest were around 20,000 miles (32,000 kilometers)," he said. "In the middle range, where all the numbers lined up and I had high confidence, you get about 10,000 miles."

The findings would seem to contradict past studies that suggested large pterosaurs had problems just getting off the ground due to their massive sizes.

For example, Quetzalcoatlus northropi, a giant pterosaur that lived in what is now Texas 70 million years ago, is thought to be the largest flying creature that ever lived, weighing more than 400 pounds (200 kilograms). (See a picture of what Quetzalcoatlus might have looked like.)

Some scientists speculate this hefty species couldn't take off from the ground as birds do, but had to drop from trees or cliffs to take to the skies.

Instead, Habib and colleagues think that—like some modern bats—large pterosaurs may have used all four limbs to launch themselves into the air before flapping their wings.

"I'm pretty confident that pterosaurs didn't take off anything like a bird," Habib said.

Giant Pterosaurs Were Global "Superspecies"?

Overall, the new research "makes all of us think more about how [pterosaurs] might have functioned," said Alexander Kellner, a pterosaur expert at Brazil's National Museum in Rio de Janeiro. But Kellner has some doubts about the results.

That's because there are several things scientists still don't know about pterosaur body structure that could affect flight distance calculations, he said. One particularly well-preserved Chinese pterosaur fossil, for example, has wing membranes made up of multiple layers of structural fibers unlike anything found in a living animal.

"We are not sure what the composition of those [fibers] is, but we can say that they have a tremendous influence in the flight of those creatures," Kellner said in an email.

If Habib's calculations are correct, the results raise the possibility that large pterosaurs could crisscross entire continents or even fly between continents on a fairly regular basis. Unlike most species, which tend to be native to specific geographic regions, the dino-era fliers may have been well-traveled "superspecies" that called the entire globe their home.

"If [giant pterosaurs] could fly very far, that might change how scientists think about their distribution," Habib said.