Palaeontologists working in northwestern Patagonia have unearthed the nearly complete skeleton of a small dinosaur whose bird-like appearance suggests that flight may have evolved twice - not only in birds, but also among the prehistoric raptors of the southern hemisphere.
The newly-discovered fossil, of a rooster-sized carnivore known as a dromaeosaur, lived 95 million years ago and is the oldest raptor ever found in the southern continents. Its discovery may signal that dromaeosaurs are much older than previously thought.
"We're really just scratching the surface," said Peter Makovicky, dinosaur curator of Chicago's Field Museum and lead author of a report on the find published in the journal Nature. "The evidence is that we have a distinct lineage [ of dromaeosaurs] - the southern lineage."
Dr Makovicky and a team of Argentine palaeontologists led by Sebastian Apesteguia, of Argentina's Natural History Foundation, collected the fossil from a well-known site known as La Buitrera, (the vulture's nest), in Rio Negro province, southeast of Buenos Aires.
The team named the creature Buitreraptor gonzalezorum, after brothers Fabian and Jorge Gonzalez, who found the fossil.
Before buitreraptor, a few teeth and other bone fragments were the only dromaeosaur remains known in the southern hemisphere.
This scarcity contrasted sharply with the relatively abundant deposits in North America and Asia of such well known dromaeosaurs as velociraptor, utahraptor and smaller species unearthed in China. Palaeontologists generally regard the northern raptors, especially the Chinese fossils, as part of the evolutionary lineage that produced modern birds.
Archaeopteryx, regarded as the first true bird, is about 145 million years old, while the feathered raptors of Liaoning, China are dated at 130 million years.
While buitreraptor is considerably younger, its location deep in South America's southern cone suggests that dromaeosaurs may be 180 million years old, dating to the time when the earth's single land mass split into northern and southern pieces. Today's continental arrangement took form about 70 million years ago. - (LA Times-Washington Post service)