A small feathered dinosaur called Sinosauropteryx sported a stripy tail, "bandit mask" across its eyes and a pale belly to help it blend into the background, according to new research.

Key points: Feathered Sinosauropteryx fossils were discovered in China in the mid-1990s

Feathered Sinosauropteryx fossils were discovered in China in the mid-1990s Palaeontologists claim dark feathers suggest signs of striped tail and 'bandit mask'

Palaeontologists claim dark feathers suggest signs of striped tail and 'bandit mask' Others disagree, stating the dark patches could be fossilised evidence of microbial action

Fiann Smithwick from the University of Bristol in the UK and colleagues examined colour patterns left in feathered fossilised specimens to reconstruct the diminutive dinosaur's colour scheme.

The researchers suggest the bird-like dinosaur that lived 130 million years ago had camouflaging patterns in order to escape being eaten.

But other scientists disagree.

Feathered fossil find

Sinosauropteryx was a metre-long carnivorous dinosaur that lived in the Cretaceous period in what is now the Liaoning province in China's northeast.

Its fossilised remains are among a slew of fossils that caused a stir when they were discovered in the 1990s, because they included preserved tissue in the form of early feathers, or protofeathers.



Like the feathers of modern birds, protofeathers contained pigment molecules including melanin — the molecule that darkens human skin, hair and eyes.

Melanin is also remarkably tough and doesn't break down easily.

"The melanin molecule is quite big and complex, and resistant to breaking down."

This toughness is the reason only dark feathers are preserved in the fossil record, Mr Smithwick said.

In a paper published in Current Biology today, Mr Smithwick and his colleagues mapped the dark feathers on three fossilised Sinosauropteryx specimens to reconstruct its patterned protofeather coat.

They concluded that it had a band of brown protofeathers around its eyes, like a blindfold. This, they wrote, could help reduce glare from nearby water.

It also sported a striped tail, perhaps to distract or confuse predators.

Reconstructed colour patterns of Sinosauropteryx showing its long stripy tail, countershaded body and bandit mask. ( Supplied: Fiann Smithwick )

They found dark feathers on the fossilised animals' back but none on the belly. When the animals were alive, the researchers suspected, those patches were covered in pale, melanin-free feathers which degraded after death.

Having a body with a paler belly — a camouflage pattern called countershading — allows animals that live out in the open to blend into the background.

So why brown protofeathers, and not black? Mr Smithwick points to modern animals.

"Ground-dwelling birds and mammals today are brown. The evidence stacks up that [Sinosauropteryx is] brown too."

Could it just be microbes?

However, these findings are not without controversy. And that's because figuring out the colour of extinct animals is not as straightforward as looking at fossilised remains.

Soon after an animal dies, microbes move in to start the decaying process. To further complicate matters, microbes can produce melanin too.

"[The brown areas] could be remnants of microbes associated with the decay of soft tissue," said Steve Salisbury, a palaeontologist from the University of Queensland.

They're the same size and similar shape to melanosomes, the packets that store melanin molecules in cells, he said.

"It's a big jump to say that pigmentation is why those parts are preserved."

Mary Schweitzer, a palaeontologist at North Carolina State University, also has doubts.

There is no evidence in the paper to support the presence of melanin or melanosomes in the fossil, she believes, other than the assumption that melanin is needed for feather preservation.

Also, the lack of preserved feathers on the fossils' underbelly doesn't necessarily mean they were pigment-free, either.

Modern birds sport a wide range of colours and hues but it cannot be assumed that melanin was the only pigment operating during the era of the dinosaurs any more that it is today, Professor Schweitzer said.

Fossil specimen of Sinosauropteryx with an interpretive drawing of the bones, stomach contents and darkly pigmented feathers. ( Supplied: Jakob Vinther and Fiann Smithwick )

Another explanation for the feather-free belly is the decay process, she added.

When an animal dies, the first part to rot is the gut, broken down by its own microbial populations.

This causes parts to explode from the belly, dragging skin and feathers away from the carcass.

The "bandit mask", too, isn't well defined. The smattering of feathers on the fossilised faces could have loosened from the top of the animal's head as its skin degraded.

And if Sinosauropteryx was masked, it doesn't necessarily mean it lived out in the open, near water, Professor Schweitzer said.

"The most iconic of bandit masked creatures, the raccoon, does not inhabit an open habitat. It prefers a deeply forested environment with access to trees."