A long-extinct animal known as the Siberian unicorn — which was actually a long-horned rhinoceros — may have walked the Earth as recently as 29,000 years ago, at the same time as prehistoric humans, researchers say.

Until now, the Elasmotherium sibiricum was thought to have vanished 350,000 years ago.

But research published in the American Journal of Applied Science describes a far more recent discovery of a well-preserved skull in Kazakhstan in Central Asia.

Researchers from the Tomsk State University have suggested the skull dates to just 29,000 years ago.

Homo sapiens — the species of humans that exist today — evolved about 200,000 years ago.

In Western Siberia, where the new "unicorn" fossil was found, a human fossil found in 2008 was dated to 45,000 years ago, according to a study published in the journal Nature.

Skull likely belonged to 'a very large male'

The skull was found near the village of Kozhamzhar in the Pavlodar region of Kazakhstan, and was in relatively good shape, showing no signs of having been gnawed upon.

"Most likely, it was a very large male," paleontologist Andrey Shpanski of Tomsk State University said.

"The dimensions of this rhino today are the biggest of those described in the literature."

Researchers used radiocarbon dating to determine the creature's age, leading to theories of migration and refuge-seeking in southern corners of Western Siberia for these lumbering legends.

Siberian rhinos, which were likely vegetarians, have been described as weighing up to four tons and standing two-metres tall by nearly five-metres long.

Their habitat extended from the Don River to the east of modern Kazakhstan, said the study.

Dr Shpanski said the findings suggested other "mass radiocarbon studies" should be done to assess remains of mammals previously believed to have disappeared 50,000-100,000 years ago.

ABC/AFP