Word: eoraptor
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Dates: during 1990-1999
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...paleontologist named Paul Sereno of the University of Chicago has come closer than anyone else to finding out. In 1991, working with Argentine scientists in Ischigualasto Provincial Park at the edge of the Andes, he unearthed one of the oldest dinosaur fossils ever found. The animal, now known as Eoraptor, was a carnivore that dates from 230 million years ago. Like the much later Tyrannosaurus, the Eoraptor belonged to the saurischian, or lizard-hipped, category of dinosaurs. (The name refers to the arrangement of its pelvic bones; the other category of dinosaurs, which includes Stegosaurus and other herbivores, is labeled...
...Eoraptor has so many primitive features, including an exceptionally simple jaw, that Sereno thinks it probably originated just a short time after the ornithischians and saurischians diverged. Says Sereno: "Fifteen years ago, it was a radical idea to think that dinosaurs came from a common stem. Now we are just inches away from finding that stem...
Sereno is even more interested in the question of how dinosaurs managed to take over the world. One thing is clear from his Argentine excavations: it happened quickly. In Eoraptor's day, dinosaurs were rare. Ten million years later, however -- the blink of an eye in geologic terms -- many reptiles and crocodilians were in steep decline, while dinosaurs were headed toward dominance...
...dinosaur. "This fossil confirms our suspicions that dinosaurs began as small, carnivorous, bipedal animals," says Paul Sereno, an assistant professor of anatomy at Chicago and a leader of the expedition. "We are just a couple of steps away from the ancestor of all dinosaurs." The scientists named the find Eoraptor, or "dawn stealer," because it appeared at the dawn of the dinosaurs and, considering its modest size, probably used stealth rather than brute force to snatch small prey...
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