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The discovery of two 130-million-year-old fossils are helping experts plug gaps in the evolutionary history of modern birds.

The fossilised wading birds, found in the Hebei province of northeastern China, had fan-shaped tail feathers and fused bones at the tips of its wings similar to birds alive today.

Named Archaeornithura meemannae, the pair predate the earliest record of the ornithuromorpha family by at least five million years.

Dubbed Archaeornithura meemannae, the species (illustrated) had fan-shaped tail feathers and fused bones at the tips of its wings similar to modern-day birds. The bird was part of a group known as ornithuromorpha and the fossil find predates the earliest record of this clade by five million years

The creatures had a small projection along the edge of their wings - a feature seen in modern birds which help them manouevre during flight - as well as long, featherless legs suggesting they belonged to a wading species.

Until now, the earliest known relative in this line of birds was found from the lower Cretaceous Yixian Formation 125 million years ago. 

This was the middle phase in the evolution of the Jehol Biota, quoted as 'the most important and diverse fossil avifauna known to science', according to Min Wang and Zhonghe Zhou from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing who made the discovery.

And A. meemannae's unique anatomy, that hints at a species already specialised for wading 130 million years ago, suggests that millions of years of evolution may have occurred prior to this creature. 

The fossils also had a small projection along the edge of its wings also seen in modern-day birds, which is designed to help them manouevre during flight, and relatively long, featherless legs suggesting it was a wading species (wing fossil pictured top and legs pictured bottom) 

Around 150 million years ago, a group of dinosaurs began developing feathered wings and learnt to fly. This group split into two - the ornithuromorphs, and the enantiornithines which later became extinct. This cladogram shows how the A. meemannae (illustrated) sits in this timeline, starting at the Archaeopteryx (top)

Around 150 million years ago, a group of dinosaurs began developing feathered wings and started to fly, but the exact timeline of this evolution is not clear.

This group of 'flying dinosaurs' split into two - the ornithuromorphs which are ancestors of modern birds, and the enantiornithines.

Enantiornithines are often referred to as 'opposite birds' because they had teeth, clawed wings and their shoulder joints were connected in an inverse way to ornithuromorphs. 

This second group became extinct at the end of the Cretaceous.

Dr Zhou said that ornithuromorphs were able evolve and thrive into more agile fliers at some point between Archaeopteryx around 150 million years ago, and 130 million years ago. 

But this leaves a 20-million-year evolutionary gap. 

Paleontologists are divided about how the ornithuromorphs were able to survive when the enantiornithines weren't.

And the A. meemannae fossils go some way to plugging this gap.  

Archaeornithura means 'ancient ornithuromorph,' and meemannae is said to be in honour of the Chinese paleontologist Meemann Chang. 

'Bird fossils are extremely rare in the Mesozoic fossil record, and until the wealth of specimens discovered from Early Cretaceous deposits in northeastern China, very little was known about the early evolution of birds,' explained the researchers. 

Archaeornithura means 'ancient ornithuromorph,' and meemannae is said to be in honour of the Chinese paleontologist Meemann Chang. The fossils were found in  Fengning in the Hebei province of China (marked)

The researchers said that the discovery of a new species belonging to the specialized clade of waders (fossils pictured) - the Hongshanornithidae - indicates that ornithuromorphs themselves were already quite specialised at this point in their evolution. This suggests older fossils may reveal additional species

'The Jehol Biota encapsulates a unique window into the biology and morphology of the oldest known avifauna; however, this fauna is clearly already well within the diversification of birds, given that both ornithothoracine clades are present. 

'Until now no ornithuromorphs had been described from the Huajiying Formation, which preserves very few fossil birds because diversity is low and geographic area is restricted, the Huajiying Formation is interpreted as the earliest stage in the diversification of the Jehol Biota.'

They added that the discovery of a new species belonging to the specialized clade of waders - the Hongshanornithidae - indicates that ornithuromorphs themselves were already quite specialised at this point in their evolution. 

'This also strongly supports inferences that this clade originated in a semi-aquatic environment,' the concluded.  

The findings are published in Nature Communications.