A dinosaur that lived between 160 and 151 million years ago could be the missing link between birds and dinosaurs. Scientists in Beijing announced yesterday that a four-winged creature called Anchiornis huxleyi could finally prove birds are descended from dinosaurs.
About the size of a big seagull, Anchiornis huxleyi is the oldest birdlike dinosaur ever discovered, which researcher Xing Xu and colleagues say makes this creature old enough to be a true precursor to birds. Other birdlike dinosaurs have come too late in the fossil record for scientists to be sure they were bird ancestors. As you can see from these sketches and images of the fossils themselves, Anchiornis huxleyi had long feathers on its arms and legs, suggesting that birds went through a phase of being four-winged before evolving into the current two-wing morphology.
According to a release about this discovery, which was published in Nature:
Anchiornis huxleyi was previously thought to be a primitive bird, but closer inspection reveals that it should be assigned to the Troodontidae - a group of dinosaurs closely related to birds. The authors date the fossil to the earliest Late Jurassic, meaning that it is the oldest bird-like dinosaur reported so far, and older than Archaeopteryx, the earliest known bird. They conclude that the presence of such a species at this time in the fossil record effectively disputes the argument that bird-like dinosaurs appeared too late to be the ancestors of birds.
via Nature [PDF]