Researchers have unearthed what could be the smallest fossil ever of an adult dinosaur: a crow-size creature that could help prove the theory that birds evolved from little dinosaurs.
The 125 million-year-old dinosaur, called Microraptor zhaoianus, appeared to have feathers and perch in trees, the researchers said. There is no evidence that it flew, though.
It lived about 20 million years after the first known bird, the Archaeopteryx. The Chinese researchers who made the discovery believe the two creatures had a common ancestor.
Like the hulking Tyrannosaurus, little Microraptor belongs to a group of dinosaurs known as theropods, meat eaters that walked on two legs. Many paleontologists believe birds evolved from theropod dinosaurs. But previous theropod fossils are bigger than typical birds, weakening the theory.
The researchers said the new fossil may ultimately help prove the theory that flight evolved in tree dwellers, rather than in ground animals. Paleontologist David Burnham at Kansas University said Microraptor fleshes out the dinosaurs-to-birds theory because it is a birdlike dinosaur that is "getting closer in size and age" to the first birds.
However, some researchers said it is hard to tell if the fossil really represents a full-grown adult. Even if it does, "it may still be a bit too big for the origination of flight," said another KU paleontologist, Larry Martin. He also said Microraptor's feet do not clearly show a grasping, birdlike toe.
The researchers, who reported their discovery in today's issue of the journal Nature, said it came from a rich fossil field in the Liaoning region of northeastern China.