Four-winged dinosaurs may be modern birds’ ancestors

New Scientist : How did modern bird flight develop? Did ground-dwelling animals try to jump higher off the ground? Or did tree-dwelling animals try to jump from trees? A group of researchers in China now believe the answer may be more complex, writes Michael Slezak for New Scientist. As early as 2003, Xing Xu of Linyi University in Shandong Province and colleagues first noticed some half-dozen fossils of flying dinosaurs that appeared to have a second set of wings on their hind legs. Since then, in a collection at the Shandong Tianyu Museum of Nature, they have found nearly 2000 complete early bird fossils, excavated 10â15 years ago, that have large feathers on their hind legs. In a study published online today in Science, they propose that the beginnings of flight may have started with ground-dwelling dinosaurs developing feathers on both their front and rear limbs. The process then moved up into trees, where dinosaurs such as Microraptor developed sharp claws for clinging to branches. Then, they say, the process moved back to the ground, where modern birds shed the second set of wings and strengthened their rear limbs by running. To further test the theory, Xu’s group plans to analyze more specimens and test the aerodynamics of the wings.