Tree-hugger. Microraptor was probably small enough to scamper up trees with its sharp, curved claws.

Meet Microraptor, the Birdlike Dinosaur

Lumbering, long-necked sauropods like Diplodocus were some of the largest creatures that ever lived. Now Chinese paleontologists describe the smallest, at least of the dinosaurs: a Microraptor that would have easily rested in the palm of your hand. The lightweight, feathered creature reinforces the theory that birds evolved from dinosaurs.

Farmers in northeastern China unearthed Microraptor, and paleontologist Xu Xing of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing figured out what it was. As Xu studied the 125-million-year-old specimen, he noticed that the tail looked very familiar. In fact, it turned out to be an exact match for the tail on a fossil called Archaeoraptor, which National Geographic magazine had trumpeted as a "missing link" between birds and dinosaurs. Xu's discovery helped prove that Archaeoraptor is a composite assembled from pieces of two fossils: a primitive bird and a dinosaurian tail (Science, 14 April, p. 238).

After the chimera was exposed, Xu and his IVPP colleagues Zhonghe Zhou and Xiaolin Wang continued to study Microraptor. Based on its rodlike tail, the trio decided that Microraptor belongs to the dromaeosaurs, dinosaurs that many paleontologists consider to be the closest dinosaurian relatives of birds. The 39-centimeter-long Microraptor is also surrounded by carbonized impressions that resemble the contour feathers covering the bodies of modern birds. The feet, too, are very birdlike: The claws are curved and positioned in a way similar to Archaeopteryx, the oldest known bird, the researchers report in the 7 December issue of Nature.

Paleontologists aren't entirely sure what to make of those claws. Larry Witmer of Ohio University in Athens says the adaptation fits nicely with the idea that flight evolved not on the ground but in tree-dwelling animals--a minority view that he shares with Zhou and a handful of other paleontologists. But no one is sure about Microraptor's climbing habits. "Just because you have a curved claw doesn't mean you have to be up a tree," says Jim Clark of George Washington University in Washington, D.C.

Related sites

Evolution of flight exhibit

Arguments for the dinosaurian origin of birds