With two-fingered hands and long “nasty” claws, the Duonychus tsogtbaatari is certainly a strange sight.

Fossils of this dinosaur were recently unearthed in Mongolia’s Gobi Desert while a water pipeline was being constructed.

Scientists say the Duonychus was a member of a group of “some of the weirdest dinosaurs ever”.

So just how remarkable is this discovery?

What do we know?

Scientists say the Duonychus measured about 3 metres long and weighed roughly 260 kilograms.

Its claws measured about 30 centimetres long.

“These were big, sharp and nasty claws,” University of Calgary palaeontologist and study co-author Darla Zelenitsky said.

The dinosaur lived roughly 90 to 95 million years ago during the Cretaceous period, according to researchers.

The Cretaceous period is a geological period that lasted from about 143.1 million to 66 million years ago.

It was a medium-sized member of a group of awkward-looking dinosaurs called therizinosaurs.

These dinosaurs were known for their round torsos, long necks, small heads, bipedal stances, massive claws and coatings of feathers.

While therizinosaurs were part of the dinosaur grouping called “theropods” — which included all the meat-eaters such as Tyrannosaurus and Spinosaurus — they preferred to eat plants.

The Duonychus roamed a “semi-arid” environment with river channels.

It lived alongside other therizinosaurs and armoured, horned and duck-billed dinosaurs, plus a smaller forerunner of Tyrannosaurus called Alectrosaurus.

What sets the Duonychus apart?

Therizinosaurs, which inhabited Asia and North America, are distinguished by their large claws.

Until now, all known therizinosaurs had three fingers.

The Duonychus, however, is unique: it only had two, hence why its name means “two claw.”

Yoshitsugu Kobayashi, a palaeontologist at Hokkaido University Museum and lead author of the study, described therizinosaurs as “some of the weirdest dinosaurs ever”.

But Dr Kobayashi added the Duonychus took “that weirdness even further”.

“It had this short, two-fingered hand with claws like a raptor … but it used them to eat plants,” he said.

“It’s like evolution said, ‘Let’s try something totally new.’ And it worked.”

Why did it only have two claws?

While the claws may have served multiple functions, researchers say they were probably mainly used for yanking down branches to feed on leaves.

“They could have used the claws for other purposes as well, perhaps for grappling, defence, digging and maybe even recognising one’s own species — ‘Hey, look at me. I also have only two fingers,'” Dr Zelenitsky said.

Scientists said Duonychus was an example of “digit reduction” — losing fingers or toes through evolution.

They said the first land vertebrates had eight digits.

The earliest dinosaurs had hands with five fingers, just like us — but many dinosaur lineages experienced digit reduction over time.

“With dinosaurs that grasped vegetation during foraging, one would think more fingers would be better,” Dr Zelenitsky said.

“That was obviously not the case with Duonychus, as its hand construction with two fingers seemed to suit it just fine.”

“I suspect it may have had a specialised feeding behaviour or food source.”

Why is the Gobi Desert a hot spot for fossils?

The Gobi Desert, which spans a large area of Mongolia and Northern China, is known for being a prolific site for discovering dinosaur fossils from the Cretaceous period.

According to Tim Ziegler, Collection Manager at the Vertebrate Paleontology section of the Museum Victoria Research Institute, the abundance of fossils is due to many fossil-bearing rocks being easily accessible, and erosion.

“Because it is a desert, it experiences high erosion, and there’s little vegetation cover that would prevent you from seeing skeletons as they erode out,” Mr Ziegler told the ABC.

“More new dinosaurs are being discovered, described and named now than ever before in scientific history. And we are in a new renaissance for research in this area,” he added.

Was the skeleton well-preserved?

While the skeleton recovered was missing its skull and legs, scientists say the arms and hands were well-preserved.

In a “rare and notable” discovery, one of the claws had retained a sheath of keratin (the same material that’s in our fingernails and hair) in its outer covering.

“It requires very good preservation overall for that more fragile, delicate tissue, like keratin, to survive the process of burial and fossilisation,” Mr Ziegler said.

The keratin sheath on this dinosaur added more than 40 per cent to the claw’s length.

Dr Kobayashi said this keratin fossilisation was “incredibly rare”.

“It gives us an extraordinary window into how these dinosaurs actually used their hands in life,” he said.

“The hands are beautifully preserved and show a ton of detail, including fused wrist bones, stiff joints and the two massive claws.”

ABC/Reuters