for National Geographic News
Using rock saws and a chisel, paleontologists working in Argentina's Rio Negro province have extracted the nearly complete skeleton of a rooster-size dinosaur.
The skeleton, from a group known as dromaesaurs, is about 90 million years old. Its presence in South America demonstrates that these birdlike dinosaurs probably arose much earlier than previously believed, according to the scientists who discovered the fossil.
What's more, the structure of the creature indicates it had feathers but did not fly, suggesting that the species might be a "missing link" in determining the origins of flight.
Until now dromaesaurs have been found only in the Northern Hemisphere. Paleontologists had assumed that the species arose after Pangea, the Earth's original landmass, separated into Laurasia to the north and Gondwana to the south.
But the new discovery means that dromaesaurs must have appeared before the landmasses separated, about 150 million years ago.
The recently unearthed fossil, probably that of an adult animal, is in excellent condition. Only a few bones from other partial discoveries were needed to complete a fully articulated skeleton.
All together, four separate Buitreraptor fossils have now been found in the same region. But the latest is the most complete, what paleontologists call the holotype, or definitive example of a species.
Fast Runner, Long Leaper
Several other species of northern dromaesaurs are known, including the feathered dinosaurs Microraptor and Sinornithaurus, both found in China.
The southern dromaesaur, Buitreraptor gonzalezorum, looks very different from its northern cousins. The paleontologists that found the latest Buitreraptor fossil believe it may actually represent a separate branch of the dromaesaurid family, named unenlagines.
The newly discovered animal is closely related to Velociraptor mongoliensis, the clever, fast-running predatory dinosaurs made famous in the movie Jurassic Park.
The dromaesaur had a long, beak-like snout; small widely spaced teeth; and a long tail. The odd proportions of its skull may have been an adaptation for hunting small burrowing mammals and reptiles, whose skeletons have been found near the remains of Buitreraptor.
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