VOA常速英语:T. Rex Ancestor: Fearsome Features at Human Scale

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An international team of paleontologists has reported the discovery of a new species of dinosaur that is sort of a miniature version of the fearsome predator, Tyrannosaurus Rex.

You've seen T. Rex in the movies – six tons or so of killing and eating machine.

Well, now say 'hello' to T's older and smaller ancestor.

Paul Sereno of the University of Chicago writes about the new dinosaur in SciencExpress, the online counterpart of the journal Science.

"I'm describing a new species of tyrannosaur – something that's more primitive than the ones we're most familiar with, like Tyrannosaurus Rex, something that's twice as old, and something that comes from China."

The new dinosaur, named Raptorex, lived about 125 million years ago in an area that included what is now northeastern China.

Sereno says Raptorex was a miniature version of T. Rex – roughly human size, about three meters long and about the weight of a person – with many of the features that would define the bigger dinosaur tens of millions of years later.

"Basically it stole away, in one blow, all of the things that were special to the big guys, he said in a VOA interview. "We had thought that a lot of these things – like the short arms [with] two fingers, maybe the extra fast legs – these things were what evolved in the course of them becoming giants and basically taking over the large, predatory dinosaur role. But no, they're all present in pint-size Raptorex."

The fossil Raptorex skeleton came to Paul Sereno under rather unusual circumstances. A collector had bought it after it had been illicitly excavated. Normally that would mean that the context of the discovery would be lost, but in this case the bones came with part of the matrix, the rock in which it was found.

"And in that rock were fish vertebrae and clams the size of your palm stuck right next to the dinosaur bone, and sediment that was sandy and muddy and other kinds of clues and details just like the forensic data from a crime scene. So I knew that I could determine in a very restricted area where that dinosaur came from. And then, where it fits in, in time. And that was important."

Sereno persuaded the collector who brought it to him to donate Raptorex to science, and after further study it will be transferred to a museum in Inner Mongolia, near where the dinosaur lived.