Early birds used four-winged system to fly, say scientists

WASHINGTON: Some primitive birds boasted four wings, before evolution led them to ditch their hind feathers in favor of webbed or scaly feet, scientists in China said recently. Previous research had uncovered the existence of bird-like dinosaurs with hind limb feathers, but evidence has remained slim in birds, which are widely believed to have evolved from dinosaurs. And even though the latest discovery documents new evidence of feathered feet in early birds, the question remains whether the plumes were actually a help or a hindrance in flight.
The Chinese scientists behind the study, published in the US journal Science, said the 11 newly described fossil specimens offer evidence the leg feathers were used as a part of a four-winged system for flying. Researchers found the new trove of data by poring over fossils at China's Shandong Tianyu Museum of Nature, said lead researcher Xing Xu, a well-known dinosaur researcher. The 11 birds come from five species and were relatively robust: larger than a crow but smaller than a turkey, according to Xu, a professor at the Key Laboratory of Vertebrate Evolution and Human Origin, Chinese Academy of Sciences.
One key specimen was a Sapeornis, a bird that was not previously believed to have hind feathers.
However, fossils held in the museum showed the creature with a fan of feathers on each heel, some as long as five centimeters (two inches). "We believe they were related to flight," Xu told AFP, describing the finding as "exciting" because ancient birds, with their delicate skeletons, have left behind few fossils for researchers to examine. The birds described in the study come from the Cretaceous period and flew some 121-125 million years ago, existing alongside dinosaurs, he said.
The back wings took the form of leg plumes and may have helped the creatures maneuver in the air while the arm wings flapped or stretched wide to soar, according to the study. The arrangement of the feathers, along with their stiff vanes, suggests they were "aerodynamic in function, providing lift, creating drag, and/or enhancing maneuverability, and thus played a role in flight," said the study. Researchers are continuing to hunt for details on the possible color of these feathers, and are crafting models to show exactly how they may have been used in flight, Xu said.
But other experts are not so sure that the foot-feathers were used to fly, but may have served other purposes like attracting mates.