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Tyrannosaurs lived in the Southern Hemisphere, too

Australian fossils suggest the kin of T. rex dispersed globally

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1:42pm, March 25, 2010
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Paleontologists digging in Australia’s aptly named Dinosaur Cove have unearthed the first known fossils of a tyrannosaur from the Southern Hemisphere.

The fossils include the remains of just one 30-centimeter-long bone from the creature’s pelvic girdle, but certain features of that bone are seen only in tyrannosaurs, says Roger B.J. Benson and his colleagues report in the March 26 Science. Previously, all known fossils of the tyrannosaur lineage have been unearthed in the Northern Hemisphere.

The size and proportions of the pelvic bone suggest that the dinosaur, which lived around 110 million years ago, was approximately the size of an adult human and tipped the scales at around 80 kilograms. That’s around the same size as Raptorex, a tyrannosaur that lived in what is now China at about the same time.

The new find suggests that tyrannosaurs, fierce bipedal carnivores known for their short arms and massive jaws, could be found worldwide during at least part of their reign, says Benson, a vertebrate paleontologist at the University of Cambridge in England.

When the first tyrannosaurs evolved around 160 million years ago, dinosaurs and other creatures moved freely between northern and southern landmasses that were connected by various land bridges. Many paleontologists had suspected tyrannosaurs were part of that interchange, but no one had found evidence in the fossil record until now, says Thomas Holtz, Jr., a paleontologist at the University of Maryland in College Park.

Though it’s possible that convergent evolution could have produced a tyrannosaur-shaped bone in an unrelated species of dinosaur, Holtz notes, the bone has several features that are found only in tyrannosaurs. “If anyone had found this fossil in Asian or North American rocks of the same age, no one would doubt it came from a tyrannosaur,” he says.

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