Nyasasaurus: Is It World's Oldest Dinosaur?

The first dinosaur to have walked the Earth may have been discovered by researchers in the corridors of London's Natural History Museum.

A mysterious fossil specimen that has been in the museum's collection for decades has now been identified as most likely coming from a dinosaur that lived about 245 million years ago - 10 to 15 million years earlier than any previously discovered examples.

It has been named Nyasasaurus parringtoni after southern Africa's Lake Nyasa, now called Lake Malawi, and Cambridge University's Rex Parrington, who collected the specimen at a site near the lake in the 1930s.

"It was a case of looking at the material with a fresh pair of eyes," Paul Barrett from the Natural History Museum, who worked on the study, said.

"This closes a gap in the fossil record and pushes back the existence of dinosaurs."

The London fossil was studied by researchers in the 1950s but no conclusion was reached and nothing was published.

"It was a mystery ... It just became this mythical animal," Mr Barrett added.

Two features of the London fossil, together with a similar sample subsequently spotted at the Iziko South African Museum in Cape Town, are strong evidence that the animal belongs with the dinosaurs, the researchers said.

The bone tissues in the upper arm show marks of rapid growth, common in dinosaurs.

They also have a feature known as an elongated deltopectoral crest that anchored the upper arm muscles which is unique to dinosaurs.

"Although we only know Nyasasaurus from fossil fragments, the anatomy of its upper arm bone and hips have features that are unique to dinosaurs, making us confident that we're dealing with an animal very close to dinosaur origin," Mr Barrett said.

The researchers believe Nyasasaurus probably stood upright, was one metre tall at the hip, and up to three metres long from head to tail.

Sterling Nesbitt, of the University of Washington, who led the study, published in the journal Biology Letters, said: "What's really neat about this specimen is that it has a lot of history.

"Found in the 30s, first described in the 1950s ... now 80 years later, we're putting it all together."