The earliest known fossil of a toothless bird that flew across the skies 120 million years ago has been dug up by scientists.

Researchers say their findings, published in Proceedings of the Royal Society B, suggest tooth loss was more common than expected in early avian development Photo: NATIONAL

The creature, named Zhongjianornis yangi, was about the size of a pigeon and was preserved in almost pristine condition in an ancient lake at Liaoning in north eastern China - suggesting it was an acquatic bird like ducks.

Its nearly complete adult skeleton - which had a long, pointed snout and toothless upper and lower jaws - sheds new light on the evolution of the beak.

It lived during a period known as the Early Cretaceous and now represents the most primitive bird ever discovered that had no teeth.

Researchers say their findings, published in Proceedings of the Royal Society B, suggest tooth loss was more common than expected in early avian development.

They say the bird beak appeared independently in several avian lineages, most likely as a response to selective pressure for weight reduction.

Zhongjianornis probably fed on fish, catching them on the wing from the surface layer of freshwater reservoirs.

It rested, and may even have nested, in canopies of abundant tropical vegetation. Unable to climb from the ground, it must have climbed tree trunks to get airborne.

Palaeontologist Dr Zhonghe Zhou, of the Chinese Academy of Sciences, Beijing, said: "Over 30 genera of Early Cretaceous birds have been reported in the last two decades from the Lower Cretaceous of northeastern China, documenting a burst of avian diversification that followed the appearance of the earliest bird Archaeopteryx.

"These early birds occur in association with hundreds of exceptionally preserved feathered dinosaurs, early mammals, pterosaurs, amphibians, flowered plants and insects.

"The new material is represented by a nearly complete and articulated skeleton. The new bird displays a combination of features that are unknown in any previously reported taxon; in particular, it represents the most basal avian that had completely lost teeth.

"The new discovery adds to our understanding of avian biodiversity in the Early Cretaceous. The skull is characterized by a pointed snout and toothless upper and lower jaws."

Unlike modern birds the magpie sized Archaeopteryx, which remains the earliest universally recognised bird and lived about 150 million years ago, had small teeth as well as a long bony tail.