Giant pterosaur needed cliffs, downward-sloping runways to taxi, awkwardly take off into air

November 7, 2012, Texas Tech University
Quetzalcoatlus skeleton. Credit: Texas Tech University

(—It weighed about 155 pounds and had a 34-foot wingspan, close to the size of an F-16 fighter jet. A five-foot-long skull looked down from a standing height similar to that of a modern giraffe. By all measures, the ancient pterosaur Quetzalcoatlus was a Texas-sized giant of the air and created a frightening shadow as it soared across the sky.

It pushed the very boundaries of size to the brink and is considered the largest flying animal yet to be discovered. Any larger, and it would have had to walk. But its bulk caused researchers to wonder how such a heavy animal with relatively flimsy wings became airborne.

Sankar Chatterjee, Horn Professor of Geosciences and curator of at the Museum of Texas Tech University, will describe the of this animal on Wednesday (Nov. 7) during the annual meeting of the in Charlotte, N.C.

Using a computer simulation, Chatterjee and his colleagues unraveled the secrets of the flight for the massive pterosaur, discovered in the Big Bend area of Texas, which has captured the imagination of and public so profoundly.

"This animal probably flew like an or a frigate bird in that it could soar and glide very well," Chatterjee said. "It spent most of its time in the air. But when it comes to and landing, they're so awkward that they had to run. If it were taking off from a cliff, then it was OK. But if Quetzalcoatlus were on the ground, it probably had to find a sloping area like a river bank, and then run quickly on four feet, then two to pick up enough power to get into the air. It needed an area to taxi."

Speculation exists on what this animal looked like, Chatterjee said. Some researchers suggested recently that Quetzalcoatlus could have weighed up to 550 pounds and used as a catapult in the same manner of a common vampire bat to create a standing takeoff.

However, Chatterjee said that computer modeling proved what is possible for a tiny, lightweight, 1-ounce bat appeared impossible for an animal 10,000 times heavier.

Flight performance seems to degrade systematically with body size because power decreases with body size, he said. Above a particular size, the available power is insufficient and flapping flight is not possible. The animal would not be able to maintain height when flying at its maximum power speed and exert full power.

"Its enormous wings must have been difficult to manage," Chatterjee said. "Each wing had at least a 16-foot span, so during its full downstroke it would smash its wing resulting in crash landing. A standing takeoff of flying of such a heavy animal violates the laws of physics."

Like today's condors and other large birds, Quetzalcoatlus probably relied on updraft to remain in the air, Chatterjee said. It was a superb glider with a gliding angle close to two degrees and a cruising speed of 36 miles per hour. Their bones were entirely hollow, filled with air, lightweight and strong. This is how such a large animal could weigh so little and still grow to its enormous size.

The animal had high-aspect-ratio wings like those of modern seabirds, meaning the wings were long, narrow, flat and pointed. It soared in open airspace by exploiting thermals or wind gradient above the ocean surface. Trading for size, the wings were structurally weak for vigorous flapping, causing the pterosaur difficulty during ground takeoff.

"Sooner or later the animal would come to the ground, especially during foraging and nesting," Chatterjee said. "Like albatrosses and the Great Kori bustards, which weigh 20 to 40 pounds, ground takeoff was agonizing and embarrassing for Quetzalcoatlus. With a slight headwind and as little as a 10-degree downhill slope, an adult would be able to take off in a bipedal running start to pick up flying speed, just like a hang glider pilot. Once it got off the ground, the giant pterodactyl entered into thermal and soared like majestic masters of the air."

Explore further: Ancient Flying Pterosaur Also Sailed Seas (w/ Video)

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4.6 / 5 (5) Nov 07, 2012
The critter more likely than not would have recognized the greater ease of take-offs with a headwind, and would have preferred a habitat where a good stiff breeze was common, such as headlands. If the cliffs were not too high, it may even have climbed from sea level to a good take-off point.
3 / 5 (2) Nov 07, 2012
Great article, but please PhysOrg, for the sake of 90% of the World citizens, please add standard units of measure. I cannot imagine what 34 of my feet stacked together look like.

Better yet, have an automated tool add the converted units in brackets after your Imperial measures so the writer doesn't have any trouble. I can code it for you in 5 minutes (see? standard unit of time, not Swatch Beats) but come on.
5 / 5 (4) Nov 07, 2012
just remember a kilogram is approx 2.2 lbs and that a meter is 3 us feet. i do that when i read metric system measurements on science sites using the metric system. no offense meant but its pretty simple math to do in your head my friend.
5 / 5 (2) Nov 07, 2012
I've seen large gulls take off in a strong wind by holding onto a rock with their wings spread. Their wings generate enough lift for them to just let go, going from standing to gliding without leaping into the air, flapping, or needing a cliff.

This method would need a pretty strong wind to work for Quetzalcoatlus, maybe an updraft from a cliff as well. I'm guessing they wern't the most graceful of creatures on the ground, so they may have had a bit of trouble climbing a cliff.

So what did Quetzalcoatlus eat?
Could they spend 24/7 in the air, only landing to breed, like some albatross do?
not rated yet Nov 08, 2012
To: Jotaf. Part of any good technical education is learning to be familiar with a variety of units. There are many "SI" type units out there that are different from each other. I would suggest you brushing up on your education by learning the more common "english" units.
not rated yet Nov 08, 2012
Great article, but please PhysOrg, for the sake of 90% of the World citizens, please add standard units of measure.

Physorg doesn't author the articles. They are copied from the respective source sites. So appealing to physorg isn't going to help much, I'm afraid.

There are many "SI" type units out there that are different from each other. I would suggest you brushing up on your education by learning the more common "english" units.

The 'english' units aren't more common. Even american scientists use the SI units these days in their publications. (Only when talking to science journalists will they use the english units - because they know they have to dumb the stuff down for the readers)
not rated yet Nov 08, 2012
I didn't mean to say that the English units are more common than the SI units. What I meant is that there are some very common English units, like foot, pound, degrees F, etc. Those English units are more common than uncommon English units like furlongs, fortnights, stones and scores.
not rated yet Nov 12, 2012
Many land animals were bigger and heavier than most are now, including giant insects. I suspect the atmosphere was denser than it is now, so they could fly 'normally.
Rance Mohanitz
1 / 5 (1) Dec 23, 2012
Those English units are more common than uncommon English units like furlongs, fortnights, stones and scores.

The plural of score is score. Scores is a strip club ;-)

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