for National Geographic News
A newfound dinosaur species from Argentina suggests that fleet-footed, meat-eating dinosaurs with sickle-like claws on their hind feet roamed both the Southern and Northern Hemispheres through the end of the dinosaur age.
The new species, named Neuquenraptor argentinus, was about seven feet (two meters) long and similar in shape and size to Velociraptor mongoliensis, the smart, speedy, sickle-clawed dinosaurs immortalized in the movie Jurassic Park.
Both species were of the deinonychosaur group. Deinonychosaurs were in turn part of the theropod groupsmall, ferocious, bipedal, short-armed carnivores that were closely related to birds.
They were widely distributed throughout the Northern Hemisphere. But prior to the discovery of Neuquenraptor in northwestern Patagonia, fossil fragments only hinted that deinonychosaurs inhabited Gondwana, the supercontinent that about 160 million years ago began its split into the current southern continents.
"This is the first time in which we have firm and unquestionable evidencean almost complete hind foot," said Fernando Novas, a paleontologist with the Argentine Museum of Natural Sciences in Buenos Aires.
Novas and his colleagues describe Neuquenraptor in tomorrow's issue of the science journal Nature. The paleontologists say their discovery advances understanding of dinosaur evolution and diversification.
Neuquenraptor lived during the late Cretaceous, the geologic period from 89 to 65 million years ago. At the time, the southern continents were approaching their present-day positions, suggesting that the deinonychosaurs must have inhabited both hemispheres for millions of years, Novas said.
Thomas Holtz, a paleontologist at the University of Maryland in College Park who specializes in theropod dinosaurs, agreed with the researchers' conclusions. He said their discovery confirms that deinonychosaurs were present in the Southern Hemisphere during the Cretaceous period.
"This helps us better understand the South American Cretaceous faunas, and the diversity within Deinonychosauria," Holtz said.
Novas, the Argentine paleontologist, said evidence that deinonychosaurs and related theropods were present in the Southern Hemisphere during Cretaceous period is allowing paleontologists to "reinterpret the evolutionary history of predatory dinosaurs."
According to Novas, for several years the available fossil evidence suggested that Gondwana was populated almost exclusively by dinosaurs found nowhere else. Examples include the abelisauroids, a group of bizarre theropods represented by the horned, bull-like Carnotaurus and the claw-wielding Noasaurus, among other species.
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