The new dinosaur fossils, representing five different species from two rock sequences in north-eastern China, all have feathers or feather-like structures.

The new finds are ‘‘indisputably’’ older than archaeopteryx, the oldest known bird, and the scientists claim this provides exceptional evidence that birds evolved from dinosaurs.

The theory that birds evolved from dinosaurs has always been troubled by the absence of feathers more ancient than those on the famous archaeopteryx.

Addressing the annual meeting of the Society of Vertebrate Paleontologists in Bristol, Dr Xu Xing, one of the lead scientists behind the discovery, said: ‘‘These exceptional fossils provide us with evidence that has been missing until now. Now it all fits neatly into place and we have tied up some of the loose ends.’’

The oldest bird, archaeopteryx, was older than the feathered dinosaurs previously found. Therefore, critics claimed, feathered dinosaurs could not have been ancestral to birds.

But the new remains have confirmed that birds actually owe their ancestry to two-footed dinosaurs that lived millions of years ago.

The new feathered species were found in two separate rock formations – the tiaojishan, which would put the fossils at 168 to 151 million years old, and the daohugou formation, which would make them between 164 and 158 million years old.

Archaeopteryx lived 150 to 145 million years ago, so was significantly younger than these new dinosaurs, Dr Xing’s team said.

One of the dinosaurs, named anchiornis huxleyi, has extensive plumage and profusely feathered feet. Until now it was thought to be a primitive bird, but this opinion was based on an incomplete fossil.

The new, nearly complete specimen, which was discovered in Daxishan in China, gives a different picture, suggesting that anchiornis huxleyi is millions of years older than archaeopteryx and has both dinosaur and avian features. It is described as a dinosaur with long feathers covering its arms, tail and feet.

The plumage attachment is said to be especially important because it shows how bird-like dinosaurs developed skeletal and other features enabling them to have feathers.

Dr Xing, of the Chinese Academy of Science in Beijing, said their work, which is also published in the journal Nature, had provided important new information on the origins of birds and the evolution of feathers.

He went on: “This fossil provides confirmation that the bird-dinosaur hypothesis is correct and supports the idea that birds descended from theropod dinosaurs, the group of predatory dinosaurs that include allosaurus and velociraptor.”

Previous efforts to prove the missing link between dinosaurs and birds have been less successful.

In 1999, a fossil which had the tail of a dinosaur and the feathered wings of a bird was hailed by National Geographic as “a true missing link in the complex chain that connects dinosaurs to birds”.

But the archaeoraptor was later confirmed to be a fake which had been cobbled together by gluing the front half of an ancient fish-eating bird called Yanornis on to the tail of a small carnivorous dinosaur belonging to a group known as the dromaeosaurs.