The giant pterosaur Quetzalcoatlus may have sported a 34-foot wingspan, but it needed to taxi down a slope to take off, U.S. researchers say.

With that huge wingspan and a weight of 155 pounds the ancient flying reptile is the largest flying animal ever discovered -- any larger, and it would have had to walk, scientists at Texas Tech University say.

Researcher Sankar Chatterjee used computer simulations to find out how such a heavy animal with relatively flimsy wings could become airborne, TG daily reported Thursday.

"This animal probably flew like an albatross or a frigate bird in that it could soar and glide very well. It spent most of its time in the air. But when it comes to takeoff and landing, they're so awkward that they had to run," he said.

"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 riverbank, 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.

"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," Chatterjee said.

Like today's condors and other large birds, Quetzalcoatlus probably relied on updraft to remain in the air, he said.