(c) Anthony K. Grafton 2003

Dinosaurs on the Wing

Have you heard about the discovery of the fossil of a four-winged dinosaur? Chinese scientists led by a man named Xing Xu recently discovered the fossil in rock that dates back to the early Cretaceous period (over 100 million years ago).

It is now widely agreed among biologists and paleontologists that birds evolved from dinosaurs. Research has shown that birds are most closely related to a group of dinosaurs known as the dromaeosaurs. The dromaeosaurs are part of the larger group of dinosaurs called the theropods, which were carnivorous and walked on two legs. In the last several years, new fossils and scientific studies have made it clear that feathers evolved among the theropods before the existence of birds or feathered flight.

Most people have heard of Archaeopteryx, one of the earliest fossilized species of bird known. The new, four-winged species discovered in China has been named Microraptor gui. It provides further evidence of the link between dinosaurs and birds. The new fossil clearly shows well-developed feathers on all four limbs of a dinosaur that was not quite a meter long.

One of the big questions in this area of paleontology has been whether feathered flight arose in tree-dwelling dinosaurs that started out by gliding, or in ground-dwelling dinosaurs that powered early flight by running. Although there is evidence to support both ideas, the new Microraptor fossil provides dramatic new evidence to support the idea that birds originated from gliding, tree-living dinosaurs.

One of the really interesting things about this find is that the existence of a four-winged, gliding dinosaur was predicted almost 90 years before the discovery of Microraptor. In 1915, a scientist named William Beebe speculated that feathered flight arose from gliding dinosaurs. He reasoned that somewhere along the line, a stage would have existed involving dinosaurs with feathers on both the arms and the legs. This new Microraptor fossil provides exciting confirmation of this idea.

Good science makes testable predictions. The predictions made by Beebe came from logical, knowledgeable deductions based on the scientific principles of evolution and developmental biology. Many advances in science have come from such careful, objective reasoning. Next week, Science Corner will discuss antimatter, something else that was predicted by a scientist before it was discovered.