Ancient Glider: Dinosaur took to the air in biplane style

January 24, 2007 at 2:22 pm

Looks like Mother Nature beat the Wright Brothers to the punch. About 125 million years before the two airmen lifted off at Kitty Hawk in their biplane, a 1-meter-long dinosaur was swooping from tree to tree with the same arrangement of wings, a new study suggests.

FLIGHT PLAN. The secondary wings (arrows in main image) created when Microraptor gui held its feathered legs and feet below its body would have provided flight surfaces similar to those of a modern biplane. Inset: Schematic of left-side view shows dinosaur’s wings. PNAS

Four years ago, paleontologists described a species of feathered dinosaur from China that they named Microraptor gui (SN: 1/25/03, p. 51: Wings Aplenty: Dinosaur species had feathered hind limbs). A series of long feathers on the creature’s legs and feet led those scientists to speculate that the dinosaur splayed its hind limbs to create an extra, hind set of wings. Other researchers cast doubt on that idea, noting that hip joints permitting such flexibility aren’t found in any related dinosaur.

Now, a pair of scientists has come up with a four-winged flight posture that doesn’t require M. gui to be a contortionist. In the new scenario, the animal held its feathered legs and feet beneath the body, says Sankar Chatterjee, a paleontologist at Texas Tech University in Lubbock. This pose would place the secondary wings below and slightly behind the main wings, just like those in aerobatic biplanes. Chatterjee and his colleague R. Jack Templin, an aeronautical engineer from Ottawa, describe their analysis of the four-winged dinosaur online and in an upcoming Proceedings of the National Academy of Sciences.

The 19-centimeter-long feathers on the lower portions of M. gui‘s legs were asymmetric, with shafts positioned close to the feathers’ leading edges. Such a configuration helps a feather resist twisting when it generates aerodynamic lift, says Chatterjee.

If M. gui were to drop straight down from the top of a tall tree, its wings probably couldn’t have prevented significant injury or death, says Templin. However, computerized flight simulations suggest that by leaping horizontally from a tree at about 3 m per second, the dinosaur could have used its biplane configuration to gain lift and swoop to trees at least 40 m away.

Such an undulating glide path would have been the most energy-efficient way to move from tree to tree, says Chatterjee.

With lengthy feathers on its legs, M. gui wouldn’t have been graceful on the ground, says Chatterjee. That, plus a lack of large-muscle attachments on the creature’s sternum, suggests that the dinosaur didn’t have the power to take off from the ground.

The study by Chatterjee and Templin is “just the sort of creative analysis that’s needed to help figure out how such an unusual creature may have behaved,” says Richard O. Prum, a paleontologist at Yale University.