A joint¹ team from the University of Kansas and Northeastern University in China says that it has settled the long-standing question of how bird flight began. In the Jan. 25 issue of Proceedings² of the National Academy of Sciences, the KU-China researchers push their research into the origins of bird flight and the early evolution of birds with decisive决定性的，坚定的 flight tests of a model of the four-winged gliding流畅的，滑行的 raptor猛禽，肉食鸟, called microraptor小盗龙.

The team is led by David Alexander, KU assistant professor of biology and an expert on modern animal flight. Alexander is joined by KU colleagues Larry Martin, David Burnham and Amanda Falk, along with Enpu Gong from Northeastern University in China, who are engaged in a comprehensive study of the functional⁴ morphology形态学，词态学 and ecology生态学 of early birds from China.

"We've done the scientific work and flight tests to show that microraptor was a very successful glider滑翔机," said Burnham. "In 2003, they found one that was so well-preserved that you could count the feathers on its wings."

A debate involving the KU scientists, recently documented by the PBS program "NOVA," had flared⁵ over the question of whether evidence supported the theory that animals developed flight as ground dwellers⁶居民, as a majority of paleontologists古生物学者 had asserted宣称，声称. But Martin and Burnham argue that flight originated above, in the trees. Such animals would have been gliders⁷. The researchers say that fossils of the hawk-sized microraptor shore up their theory.

"The controversy⁸ was that these animals couldn't spread their hind⁹-wings to glide," said Burnham. "But we've been able to articulate同关节连接，使相互连贯 the bones in their hip¹⁰ socket¹¹ 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样本 in Chinese museums.

These astonishingly令人惊讶地 preserved保藏的 fossils give a detailed¹³ image of the plumage翅膀，羽毛 in the gliding³ raptor and make possible the construction of an accurate model.

The fossils also show that an essentially¹⁴ sprawling蔓生的，不规则生长的 posture¹⁶ was a plausible貌似真实的 hind-limb wing position to provide stable flight with gliding parameters¹⁸参数，参量 better than those of modern "flying lemurs狐猴."

The competing "biplane复翼飞机 posture" advanced by other researchers suggested that an upright垂直的，正直的 stance provided for successful glides¹⁹. But the KU-China team argues that this stance required an impossibly heavy head to maintain a proper center of gravity. Furthermore, the presence of seven-inch-long flight feathers on the feet would prohibit any extended stay on the ground. Thus, microraptor must have been completely arboreal树木的.

"We decided²¹ that we would take the skeleton we had, put wings on it from the feather pattern and show that it could fly," said Burnham. "If others think that it was a terrestrial陆地的，陆生的 runner, they should make a model and put it on a treadmill踏车，跑步机 and show that it could run with those long feathers on its hind legs."

Successful flight tests were conducted in the open air and under more controlled conditions in the Anschutz Sports Pavilion at KU. A video of some of the tests is available at http://www.features.ku.edu/microraptors.Indeed, the KU-China team's work provides such strong support for the trees-down model for the origin of avian鸟类的 flight that the alternative terrestrial (ground up) origin now may be abandoned.

Researchers Martin, Burnham and Falk, along with Gong, recently made headlines for their discovery of a venom毒液，恶意-delivery system in sinornithosaurus中国鸟龙, a cousin of microraptor. A paper detailing that finding was published in PNAS美国国家科学院院刊 last month.