For Immediate Release Contact: Greg Borzo (312) 665-7106 Drifting continents About 200 million years ago, all of the Earth’s land was amassed in one supercontinent called Pangaea. During the Middle and Late Jurassic, Pangaea split into two landmasses. Laurasia, composed of North America, Asia and Europe, drifted to the north; Gondwana, composed of the southern hemisphere continents plus India, drifted to the south. Until recently, dromaeosaurs (swift-running, bi-pedal, birdlike dinosaurs) have been found only in Cretaceous rocks of Asia and North America, northern continents that were part of Laurasia. (Laurasian dromaeosaurs include the famous Velociraptor from the Gobi Desert, the large Utahraptor from the American West, and the recently discovered Microraptor and Sinornithosaurus from China, both of which preserve amazing traces of bird-like plumage.) This distribution led scientists to believe that dromaeosaurs originated in Laurasia after it drifted apart from Gondwana. In the last few years, however, a handful of specimens of possible dromaeosaurs or early birds have been discovered on southern continents. Nevertheless, their incomplete preservation led to some ambiguity and debate regarding their identities. The new discovery provides definitive evidence that dromaeosaurs also lived in South America, which was part of Gondwana. As a result, dromaeosaurs must have originated when all of the continents were still assembled in a single landmass during the Jurassic as far back as 180 million years ago—much earlier than previously thought. Results of an analysis of evolutionary relationships of advanced theropods undertaken as part of this research indicate that the Gondwanan dromaeosaurs and Rahonavis, an animal previously considered to be a very primitive bird, actually constitute a separate branch of the dromaeosaurid family tree. This branch is distinct from Velociraptor and other Laurasian dromaeosaurids, including some of the famous feathered dinosaurs from China. Because Rahonavis has long and wing-like forelimbs, this finding could imply that flight may have evolved twice, once in birds and once among this group of Gondwanan dromaeosaurs. This evolutionary research is part of a larger, ongoing project to assemble the evolutionary family tree of dinosaurs (including birds), and their relatives, by a team of scientists that includes Makovicky and is funded by the National Science Foundation. Continue