Experts debate over species of dino fossil

LONDON - A debate has been going on in the palaeontology world as scientists debate over classification of Raptorex - the pint-sized supposed precursor to Tyrannosaurus rex a 3-metre-long fossil that made headlines when its discovery was reported last year.

Rather than a miniature blueprint for tyrannosaurs and other giant dinosaurs in the same family, some palaeontologists contend that it is a juvenile specimen of Tarbosaurus - a dinosaur closely related to, and living at the same time as, Tyrannosaurus.

a team of researchers led by palaeontologist Paul Sereno of the University of Chicago, Illinois had classified Raptorex kriegsteini but Peter Larson, president of the Black Hills Institute of Geological Research, a private fossil excavation and supply company based in Hill City, South Dakota believes otherwise.

“Every feature about it says Tarbosaurus. It is exactly what I would have expected a baby Tarbosaurus to look like, including the correct number of tooth positions,” Nature quoted Larson as saying.

Another palaeontologist from the University of Oslo, Jorn Hurum, agreed with Larson. They also voiced concerns about the origin and age of the fossil. On the basis of two other fossils - a fish vertebra and a freshwater clam - found alongside the dinosaur fossil, the paper says that the specimen of Raptorex is of Chinese origin and about 125 million years old.

But the evidence is too vague given that the fish and clam fossils are widespread in time and geographic area, they said.

Larson suggested that the fossil could instead have come from known Mongolian Tarbosaurus beds dating from 70 million years ago.

However, Sereno has supporters too.

“I have not seen anything to justify the shadow of doubt,” said Thomas Carr, who works on tyrannosaurid dinosaurs at Carthage College in Kenosha, Wisconsin.

He said that there are specific physical characteristics, including the absence of a vertical ridge on the pelvis, that separate the specimen from other tyrannosaurids.

Sereno added that he stands by his conclusions, and noted that no one had “generated evidence” or “published a scientific paper” refuting them.

The issue is likely to cause a stir at the annual meeting of the Society of Vertebrate Palaeontology (SVP), being held in Pittsburgh, Pennsylvania, on 10-13 October. (ANI)