More On Birds And Dinosaurs

How small can a dinosaur be? Until now, the answer was, about as big as a medium-size dog--the size of a velociraptor, the swift, ferocious predators that haunt the nightmares of modern humans who saw "Jurassic Park." But last week, in the journal Nature, three Chinese paleontologists reported finding a new species of theropod (the suborder of upright-walking carnivores that includes velociraptors and Tyrannosaurus) that was very much smaller--about 15 inches long, or roughly the size of a modern crow. "For a dinosaur, Microraptor zhaoianus is a very small dinosaur," says Luis Chiappe, head of vertebrate paleontology at the Los Angeles County Natural History Museum.

And a potentially important one, because the specimen may shed light on one of the hottest topics in paleontology, the evolutionary transformation of dinosaurs into birds. By coincidence, a different Chinese team reported in Science last week the discovery of a bird from the Early Cretaceous, Protopteryx fengningensis, with primitive feathers that seem halfway between reptilian scales and modern bird feathers. Similarly, Microraptor's teeth have features, such as a narrow "waist" between the root and crown, that seem to place them midway between birds and non-avian theropods. Its foot is birdlike, with an elongated toe that could have been used for grasping branches; one leading theory of the evolution of flight is that it began among tree-dwelling animals looking for a better way down than falling. "It adds to the enormous pool of data we have supporting the idea that birds evolved from meat-eating dinosaurs," says Chiappe.

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