In the old family tree, there are two major groups of dinosaurs: the bird-hipped ornithischian dinosaurs (such as duck-billed dinosaurs and stegosaurs) and the reptile-hipped saurischians, which include the theropods (such as Tyrannosaurus rex) and the sauropods (the long-necked, long-tailed herbivorous giants).
The new study completely reorganizes this setup. According to new analyses, theropods and ornithischians are more closely related than scientists previously thought, and both fit into a previously unknown group called Ornithoscelida, the researchers said.
The change may seem small, "as only a few branches are being reshuffled," said Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland, who was not involved in the study. "But because these are the big branches right near the root of the tree, changing them around is huge. It's saying that much of what we thought about the origins and early history of dinosaurs, going back to the late 1800s, is wrong."
In addition, their models echoed other research suggesting that early dinosaurs were both omnivorous and small, and used their hind legs for walking and two arms for grasping, the researchers said. The analysis also indicates, somewhat unexpectedly, that dinosaurs originated in the Northern Hemisphere, and not in Gondwana, a supercontinent that encompassed Africa, South America, Australia, Antarctica, the Indian subcontinent and the Arabian Peninsula more than 180 million years ago.
The study also bumps back the appearance of the first dinosaurs to 247 million years ago, which is older than the previously accepted date of between 245 million and 240 million years ago, Live Science previously reported.
More here
http://www.livescience.com/58374-updated-dinosaur-family-tree.html
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