Scientists at the University of Kansas and Northeastern University in China say they know how bird flight began.
The researchers write in an article published this week that flight tests of a model of a dromaeosaur called Microraptor gui establishes that the animals first flew by gliding from trees.
“We’ve done the scientific work and flight tests to show that microraptor was a very successful glider,” David Burnham, a KU paleontologist, said. “In 2003, they found one that was so well-preserved that you could count the feathers on its wings.”
Paleontologists have been engaged in a debate about whether available evidence supported the theory that animals developed flight as ground dwellers. Burnham and his KU colleague Larry Martin argue that flight originated from on high, in the trees, and that such animals would have been gliders. The researchers say that fossils of the hawk-sized microraptor shore up their theory.
“The controversy was that these animals couldn’t spread their hind-wings to glide,” Burnham said. “But we’ve been able to articulate the bones in their hip socket to show that they could fly.”
The new flight model created by Martin and Burnham comes directly from a skeleton composed of casts of the original bones of a microraptor and the preserved impressions of feathers from specimens in Chinese museums.
The fossils provide a detailed image of the plumage in the gliding raptor and make possible the construction of an accurate model. They also indicate that an essentially sprawling posture was a plausible hind-limb wing position to allow for stable flight.
The competing “biplane posture” advanced by other researchers suggested that an upright stance provided for successful glides. But the authors of the new study argue that this stance required an impossibly heavy head to maintain a proper center of gravity, that the presence of seven-inch-long flight feathers on the feet would prohibit an extended stay on the ground and that, as a consequence, Microraptor gui must have been completely arboreal.
“We decided that we would take the skeleton we had, put wings on it from the feather pattern and show that it could fly,” Burnham said. “If others think that it was a terrestrial runner, they should make a model and put it on a treadmill and show that it could run with those long feathers on its hind legs.”
The researchers conducted successful flight tests of the model, both in open air and under indoor controlled conditions, and documented the results in a video made available by KU.
The study is published in the Jan. 25 issue of Proceedings of the National Academy of Sciences.
The research team included Burnham, Martin, KU colleagues David Alexander and Amanda Falk and geologist Enpu Gong of China's Northeastern University.
The same team of scientists recently earned headlines after discovering that the skulls of another dromaeosaur family called sinornithosaurus included a venom-delivery system. Their paper detailing those findings was published in Proceedings of the National Academy of Sciences last month.
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