A gigantic prehistoric bird which could have been as big as an ostrich has been identified from a single jawbone which has lain undiscovered in a museum for several years, according to scientists.

Darren Naish, of the University of Portsmouth, said that the bird was estimated to have been between two and three metres tall, and lived around 85 million years ago in Kazakhstan.

It has been discovered from the fossil of a single jawbone which has been found in a Brussels museum.

Named Samrukia nessovi, it represents one of the largest birds known from the Cretaceous period, a time when dinosaurs roamed the earth.

The fossil is only the second giant, land-living bird species to be discovered in Cretaceous-aged rocks and the first to be found in Asia.

A previously recognised species, Gargantuavis philoinos, found in France, was named in 1998 but experts have argued over its identification. A paper published yesterday in Biology Letters suggests that the new Kazakh specimen confirms the presence of giant birds in the Cretaceous period.

Dr Naish said: “Since the 1850s we’ve known that numerous bird species lived during the age of the dinosaurs (known as the Mesozoic Era), but virtually all were crow-sized or smaller.

“We can now be really confident that Mesozoic terrestrial birds weren’t all thrush-sized or crow-sized animals – giant size definitely evolved in these animals and giant forms were living in at least two distinct regions.” If the newly-discovered bird flew, its wingspan was likely to have exceeded four metres, but Dr Naish said there was no way of knowing if it took to the skies or was flightless like an ostrich.