Winging it: an unusual approach to flight - Coelurosauravus evolved new skeletal elements to support wings made of skin - Brief Article

Science News, March 8, 1997 by Richard Monastersky

Ever desperate to leave the ground, humans will strap just about anything to their bodies and leap into the air. Hence the sports of hang gliding, skydiving, and bungee jumping, to name but a few extreme rites of flight.

Animals make do with just a few alterations of their basic skeleton. For instance, birds have a modified arm and hand, while bats rely on skin stretched over greatly elongated fingers.

A reptile from Earth's distant past developed a unique flying apparatus. Instead of fashioning a wing from its existing skeleton, this ancient creature evolved completely new bones to spread wings made of skin, according to a study of a newly discovered fossil.

"This is really without parallel in any other gliding or actively flying animal-the fact that they actually developed new skeletal elements to support the wing," says Hans-Dieter Sues of the Royal Ontario Museum in Toronto. Sues collaborated with Eberhard Frey and Wolfgang Munk of the State Museum for Natural History in Karlsruhe, Germany. They describe their work in the March 7 Science.

The animal, called Coelurosauravus, lived during the late Permian period, more than 250 million years ago, making it the oldest known flying vertebrate. About as long as a small squirrel, this reptile had at least 22 slender bones extending outward and back from each side of its chest. The bones supported a foldable wing, much like a Japanese fan.

Scientists initially discovered fossils of Coelurosauravus in the early 1900s but until now had failed to decipher the creature's secret. The first paleontologists to study Coelurosauravus discovered the thin wing bones but removed them, thinking they were fish structures that had somehow been superimposed, says Robert L. Carroll of McGill University in Montreal. Later, a different paleontologist misidentified it as a dinosaur.

Carroll made his own mistakes while studying a Coelurosauravus fossil from Madagascar in the 1970s. He surmised that the wing bones were elongated ribs, sticking out perpendicular to the backbone in a design reminiscent of the modern gliding lizard Draco.

A recently discovered Coelurosauravus fossil from Germany, however, reveals that the wing bones were not part of the ribs, report Sues and his colleagues. Much more complete than previous specimens, the new fossil shows that the wing rods were bony structures growing out of the skin; they did not attach to the rest of the skeleton, the researchers say.

"They corrected a lot of mistakes I made and others made," says Carroll. "It's really a startlingly different kind of flying animal."

Unlike birds and bats, Coelurosauravus could not truly fly because it lacked muscles to flap its wings. Nonetheless, it may have covered long distances by gliding from trees. Draco can sail 30 meters in one leap.