Friday, September 18, 2009

Mini Precursor to Tyrannosaurus rex.

The Washington Post (and other organizations) is reporting on a surprising find linking the ground-shaking Tyrannosaurus rex to a precursor that was maybe nine feet high, on a good day. The find, though, is problematic in non-palaeontological ways:
The new animal, based on a single fossil smuggled out of China and eventually sold to a private collector, has been named raptorex. It lived 125 million years ago in a lake-dotted region of northern China.

Raptorex had a big head, tiny forelimbs, and a body built for sprinting, just like T. rex. But this fossil is of a young adult dinosaur, nearly full-grown, that at maturity would have been only about 9 feet long, compared with about 40 feet for an adult T. rex, according to a paper published Thursday in the online edition of the journal Science. It would have weighed only 150 pounds. An adult T. rex could reach 13,000 pounds.
That it has seen the light of day is great. That we have no idea what its provenance is is not. More good sites have been ruined by careless dinosaur hunters than I can care to count. The jarring morphology of Raptorex is confusing though:
"No longer can we describe the big head, the powerful jaw muscles, the tiny forelimbs, the very fleet-footed hind limb, as features of the very large body size and the mega-predatory habits," said study co-author Steve Brusatte, a doctoral candidate at the American Museum of Natural History in New York.
It should be pointed out that this poses no problems for evolution or dinosaur research. It simply means that evolution proceeded on a slightly different course for Tyrannosaurus than we thought. It is still clear that the morphology found in Raptorex was carried over into descendant forms.

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