T.rex is the only Tyrannosaurus species, say scientists

A group of scientists say the meat-eater dinosaur T.rex is the only species of Tyrannosaurus.

It follows a previous study which claimed otherwise.

Seven palaeontologists say a paper from March which concluded there were three Tyrannosaurus species does not have enough evidence for the claim.

The scientists criticised the work saying the authors did not use the right methods and measurements.

T.rex has been recognised as the single species of the genus Tyrannosaurus since the dinosaur was first described in 1905.

A genus is a broader grouping of related organisms than a species.

But in March, three researchers said they had concluded the T.rex should be split into three species after studying about 38 T.rex fossils.

The paper shook the palaeontology world and now a different group of scientists say they have proved it wrong.

Tyrannosaurus, part of a group called theropods that included all the meat-eating dinosaurs, had a massive head, but small arms.

The new study, which was published in the same scientific journal, looked at intra-species variation in thighbone thickness in four other meat-eating dinosaurs and 112 species of living birds, descendants of small feathered theropods.

It concluded the Tyrannosaurus variations were not unusual.

"The evidence needs to be convincing, and to suddenly divide such an iconic animal like T.rex, which has been known for over a hundred years, into different species requires a high burden of proof.

"It is true that there is variation in the size and shape of T.rex bones, but in our new study we show that this variation is minimal," said University of Edinburgh palaeontologist Steve Brusatte, a co-author of the new study published in the journal Evolutionary Biology.

This is unlikely to be the end of the dinosaur debate however, with the original researchers ready to defend their study.

Palaeontologist Gregory Paul told news organisation Reuters the new work by Brusatte and others was hastily done and "structured to defend T.rex" instead of exploring whether there could have been other species.

"We are open minded that there may be multiple species of Tyrannosaurus," Brusatte said. "We just need more and better fossils."