Odds being against such striking parallel evolution, paleontologists speculate that dromaeosaurs more likely originated more than 180 million years ago, before Pangaea broke apart.
Here's why that's important: About 200 million years ago, Earth had just one giant land mass called Pangea.
Toward the end of the Jurassic period, it split in two.
"Buitreraptor is one of those special fossils that tells a bigger story about the Earth's history and the timing of evolutionary events," said Peter Makovicky, curator of dinosaurs at The Field Museum.
"It not only provides definitive evidence for a more global distribution and a longer history for dromaeosaurs than was previously known, but also suggests that dromaeosaurs on northern and southern continents took different evolutionary routes after the landmasses that they had occupied, drifted apart." The Buitreraptor fossil was found in northwestern Patagonia (the southern end of the South America continent) about 700 miles southwest of Buenos Aires.
The discovery changes the understanding of when humans reached North America.
The study, to be published this week in the science journal Nature, said the numerous limb bones fragments of a young male mastodon found at the site show spiral fractures, indicating they were broken while fresh.
What we call Laurasia eventually became North America, Asia and Europe.
The other chunk Gondwana, developed into the continents of the Southern Hemisphere and India.
The new find suggests such raptors go back much further in time than previously thought.
Until recently, dromaeosaurs had been found only in Asia and North America and only in the Cretaceous period, which ran from 145 million to 65 million years ago.
C, hunting peoples had occupied most of North America, south of the glacial ice cap covering the northern part of North America.