"I was lucky to discover in Patagonia the remains of several theropod dinosaursthe advanced deinonychosaurians and kin, which are different from the abelisauroid range," Novas said.
This newer evidence suggests that deinonychosaurs were widely dispersed throughout the world before the northern and southern continents broke up and drifted apart, Novas said.
As the landmasses separated, populations of deinonychosaurs that descended from early ancestors in the Northern and Southern Hemispheres were similar, but not identical. As time passed, the differences between these populations grew more distinct.
"Patagonian deinonychosaurs represent branches that emerged early from the [family tree] of deinonychosaurs and do not belong to the specialized deinonychosaurs from Asia and North America," Novas said.
Holtz, the University of Maryland paleontologist, said he is not at all surprised at the worldwide distribution of the sickle-clawed dinosaurs.
He said fossil evidence shows that birds were present at least as early as the late Jurassic, a geologic period from 154 to 144 million years ago. If birds were present, then so, too, were deinonychosaurs, a sister group of birds, Holtz noted.
"And during the late Jurassic there was greater connection between the various landmasses, allowing for the spread of various land-dwelling groups," he said.
The paleontologist added that the discovery of Neuquenraptor shows that deinonychosaurs existed in Gondwana into the late Cretaceous.
It was in 1996, during an excavation of a giant plant-eating dinosaur known as a titanosaur, that Novas and his colleagues discovered the tiny foot bones of Neuquenraptor.
Originally, the paleontologists thought the theropod died while scavenging the carcass of the titanosaur. But further analysis of the surrounding sediments, together with the well-preserved state of the fossils, suggested their association was accidental.
"We interpret that Neuquenraptor was not scavenging the [titanosaur] carcass but [that] both were transported by a river until their respective burial in sandstone," said Novas, whose research was supported in part by a grant from the National Geographic Society's Committee for Research and Exploration.
In addition to Neuquenraptor, the Patagonia fossil site has yielded several other meat-eating dinosaur species new to science over the years. These include the ostrichlike Patagonykus puertai, the large and big-handed Megaraptor namunhuaiquii, and the birdlike Unenlagia comahuensis.
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