• The feathers have barbs and blade-like barbules, but lack the central shaft present in modern bird feathers. (Royal Saskatchewan Museum (RSM/ R.C. McKellar))
A feathered dinosaur tail preserved in mid-cretaceous amber around 99-million years ago has been discovered in a market in Myanmar, shedding new light on the evolution of feathers.
By
Ellen Sima

12 Dec 2016 - 3:34 PM  UPDATED 12 Dec 2016 - 3:34 PM

For the first time, dinosaur bones and feathers have been found preserved together in amber. This groundbreaking finding was published in Current Biology.

"The new material preserves a tail consisting of eight vertebrae from a juvenile; these are surrounded by feathers that are preserved in 3D and with microscopic detail," says Ryan McKellar of the Royal Saskatchewan Museum in Canada.

McKellar is a part of the international team that worked with the specimen, whose exciting research suggests that the feathered tail belonged to a juvenile coelurosaur.

The Coelurosauria is a dinosaur clade that also includes tyrannosaurs, velociraptors and the ancestors of modern birds. But while it may have massive cousins, this specimen would have been closer to the size of a sparrow than Sharp Tooth. 

 

How can the team be sure the feathers belonged to a dinosaur?

It’s the tail that’s telling, says McKeller. "We can be sure of the source because the vertebrae are not fused into a rod or pygostyle as in modern birds and their closest relatives. Instead, the tail is long and flexible, with keels of feathers running down each side."

This distinction between the morphology of bird and dino-tails – fused versus flexible – meant the researchers could rule out the possibility that the feathers belonged to a prehistoric bird.

So while feathers of a similar age have been discovered in amber before, this is the first time that they can be definitively linked to a true dinosaur.

The colours of the feathers suggest that this distinctive tail was chestnut brown on top with a pale or white underside. 

 

To market to market to buy a … dinosaur feather?

If it weren’t for the good luck and sharp eyes of Lida Xing of China University of Geosciences, the study’s first author, this remarkable find might never have come to light.

Last year, Xing discovered the piece at an amber market in Myitkyina, a city in northern Myanmar. The material in the amber was thought to come from some sort of plant, and was destined to become a piece of jewelry or an ornament.

But Xing recognised the scientific importance of the specimen, convincing the Dexu Institute of Peleontology to snap it up for study – and their investment definitely paid off.

The research team used CT scanning and microscopic equipment to get a close look at the specimen, revealing stunning detail in three dimensions.

Many examples of dinosaur feathers in the fossil record are two-dimensional imprints compressed in stone. Because this specimen is preserved in amber, its feathers have better retained their shape, allowing scientists to study aspects of feather structure and evolution that can’t be determined from stone fossils.

"Amber pieces preserve tiny snapshots of ancient ecosystems, but they record microscopic details, three-dimensional arrangements, and labile tissues that are difficult to study in other settings," McKellar says. 

 

From dinosaurs to birds – what can this specimen tell us about the evolution of feathers?

Modern bird feathers have a central shaft or ‘rachis’ (the hard part running down the middle), with softer barbs branching off of it, and barbules branching off of them.

If you think of the rachis as the ‘trunk’ of the feather, then the barbs would be the branches, and the barbules the leaves.

While the amber-preserved dinosaur feathers have both barbs and barbules, they lack a well-developed rachis. This lends weight to the theory that feathers started off fluffy and flexible, with the hard central structures necessary for flight arising later.

So while the feathers wouldn’t have been useful for flight, they may have acted like fur and kept the young dinosaur warm and dry.

The researchers are now "eager to see how additional finds from this region will reshape our understanding of plumage and soft tissues in dinosaurs and other vertebrates."

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