Could dino poo unlock answers to ancient bird mystery?

When you're looking for the answer to a puzzled from millions of years ago, sometimes the most unexpected of places can turn up with a clue – such as dinosaur poo.

An ancient lump of poo, holding a single feather, has provided palaeontologists with brand new information on a 66-million-year-old mystery.

Researchers say it could be the key to answering the question of why some birds were able to survive the great mass extinction event that wiped out most of the world's dinosaurs and other weren't.

Read on to find out more.

Scientist David DeMar Jr came across the golden nugget in the Hell Creek formation in northeastern Montana in the United States.

"I was crawling up a rocky outcrop collecting fish fossils when I came across a dark, reddish-brown nodule about half the size of a golf ball," he explained.

He said he "couldn't believe what [he] was seeing" when he spotted a tiny feather in the dung.

"It's such a beautiful, well-preserved feather, from such an unexpected source, and it's exciting that it could help us answer this huge question in paleontology," said lead author of the poop study Dr Jingmai O'Connor.

Jingmai, who is also known as the Punk Rock Paleontologist, said as far as she knew, "no one has ever thought to look for feathers or to study feathers in coprolites".

Coprolite is the word scientists use to describe fossilised faeces, or poo.

It turns out that one dinosaur's poop is a palaeontologist's treasure, as the dino dung contained multiple well-preserved feathers, some tiny fish scales and bird bones.

Jingmai believes the feathers and bones came from an aquatic bird.

"Most couldn't fly, and instead, they used their specialized feet to dive down into the water to hunt for things like fish."

Jingmai says that the birds, called hesperornithiforms, were close relatives of Neornithes birds, which survived the extinction event that wiped out so many dinosaurs.

Scientists had thought that the reason Neornithes survived was because they lived near water.

But the hesperornithiforms, despite being aquatic birds, didn't survive the mass extinction.

Jingmai thinks this could possibly be down to the differences in their feathers.

She thinks their more "primitive" feathers might have not kept the birds warm enough during the period of global cooling.

The lead author added that she hopes more scientists should start looking at fossilised poo for answers in the future.

"We only knew to look at this one because of how it happened to be split open, with the feather exposed—it was literally a lucky break," she said.

"I hope more scientists start CT scanning coprolites and taking a closer look at them to see what might be inside."