The Evolution Of Flight: The Microraptor Could Glide Over Short Distances Even Without Feathers

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Recent dinosaur fossil finds have produced more questions than answers about the early evolution of flight as dinosaurs, such as the microraptor, seem to have had feathers on their arms, tail and legs. In an attempt to learn more about the transition from dinosaurs to birds, researchers used a series of wind tunnel tests to examine the flight capabilities of the microraptor.

Wind tunnel tests revealed that the feathered arms, legs and tail of the microraptors let them glide over long distances. The microraptor is an early Cretaceous five-winged paravian, related more closely to birds than advanced theropods such as dromaeosaurids like the velociraptor.

Researchers from the University of Southampton in England were interested in learning more about the flight performance of the microraptor as it could shed more light on the evolution of flight, from gliding to flapping seen in modern birds. The microraptor, with its five wings, may serve to prove the theory that flight evolved through a tetrapteryx, or four-winged, phase, as first theorized by William Beebe.

The researchers constructed an anatomically accurate microraptor model and put it through a series of wind tunnel experiments and flight simulations. Based on these tests, the researchers believe the dinosaur was able to produce a lot of lift with its wings, allowing it to slowly glide over a short distance without losing much height. Two factors, wing shape and leg placement, which may have affected flight performance, did not have much effect on the microraptor’s ability to glide over a long distance. While the dinosaur did not have the most efficient method of flight it was still able to soar in the air due to the lift generated by its wings.

Co-author Gareth Dyke, from the University of Southampton, said in a statement, “Significant to the evolution of flight, we show that microraptor did not require a sophisticated, ‘modern’ wing morphology to undertake effective glides, as the high-lift coefficient regime is less dependent upon detail of wing morphology.” For microraptors, feathers were not necessary for gliding and may have served more for mating or some other purpose. According to Dyke, the results are consistent with the hypothesis that "symmetric ‘flight’ feathers first evolved in dinosaurs for non-aerodynamic functions, later being adapted to form aerodynamically capable surfaces."

The microraptor’s flight performance has led to new insight in the evolution of flight as dinosaurs did not need to be very aerodynamically efficient to achieve flight. The research was published in the journal Nature Communications. A video of the wind tunnel experiments can be viewed below.

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