Paleontologists discovered the fossilized remains of an enormous prehistoric bird that lived in Central Asia more than 65 million years ago and lived alongside dinosaurs.

The bird, called Samrukia nessovi after the mythical Kazakh Phoenix known as the samruk, lived in what is now modern Kazakhstan. The giant bird would have stood taller than an ostrich if it was flightless and if it flew would have a greater wingspan than the albatross.

The discovery, reported in the latest issue of Royal Society Biology Letter, challenged previous theories about the diversity of early birds.

"In fact, these big birds fit into the idea that the Cretaceous wasn't 'a non-avian dinosaurs-only theme park.' Sure, non-avian dinosaurs were important and big in ecological terms, but there was at least some space for other land animals," lead author of the paper, Darren Naish said in a report by Discovery News.

The findings were based on all that's left of the animal, a toothless lower jaw found in Late Cretaceous sediment in Kyzylorda, southern Kazakhstan.

The bones measure 275 millimetres long and the skull would have been 30 centimetres or a foot long. There wasn't enough evidence to determine whether the bird flew or not. But based on the remaining bones it would have stood close to 3 metres high if it was flightless. If it flew it would have had a wingspan of at least four metres.

Birds according to prevailing theory are believed to have been relatively small for tens of millions of years. The Samrukia nessovi would be the only second known large bird from the dinosaur era. The first large bird to be identified was Gargantuavis philoinos which lived in southern France 70 million years ago. Other bird fossils found during that time were crow-sized or smaller.

"So we can now be really confident that Mesozoic terrestrial birds weren't all thrush-sized or crow-sized animals," Naish said. "Giant size definitely evolved in these animals, and giant forms were living in at least two distinct regions. This fits into a larger, emerging picture: Mesozoic birds were ecologically diverse, with lots of overlap between them and modern groups."