Dinosaur species discovered with just two claws, baffling scientists

With claws nearly the size of a human forearm and arms that looked like barbecue tongs, a recently discovered dinosaur is turning heads – and raising eyebrows.

Resembling a mashup of a sloth, a giraffe, and Edward Scissorhands, this unusual creature roamed the Earth millions of years ago. Thanks to an incredible fossil find in Mongolia, we are now getting a much clearer picture of its strange anatomy.

Discovery of a two-clawed dinosaur

The dinosaur, discovered by paleontologists from the University of Calgary and Mongolia’s Institute of Paleontology, has been named Duonychus tsogtbaatari in honor of its impressive claws. “Duonychus” means “two claws” in Greek.

What sets this find apart is the remarkable preservation of a claw sheath that is made of keratin, the same material as our fingernails. The sheath reveals that the dinosaur’s claw was much longer than its bone structure alone would suggest.

“It’s close to a foot (30 cm) in size,” said paleontologist Darla Zelenitsky, an associate professor at the University of Calgary in Canada. “This is by far the biggest claw preserved for a dinosaur that has that keratinous sheath on it.”

Big claws, but not so ferocious

Duonychus tsogtbaatari belonged to the therizinosaur group of dinosaurs, which is part of the broader theropod family. This family also includes Tyrannosaurus rex.

“Therizinosaurs were a group of herbivorous/omnivorous theropod dinosaurs that lived in Asia and North America during the Cretaceous Period. These theropods are notable for their three-fingered hands sporting large claw-like unguals,” noted the researchers.

Unlike most theropods, which were primarily carnivorous, therizinosaurs evolved into plant eaters, with adaptations such as a small head, a beak-like mouth, and leaf-shaped teeth suited for processing vegetation.

Their most striking characteristic was their massive claws, which could reach up to a meter in length and were likely used for defense and foraging.

Fossils of therizinosaurs, such as Therizinosaurus from Mongolia, have revealed a fascinating evolutionary history that connects them to other theropods, despite their unusual anatomy.

The therizinosaur lineage is closely related to feathered dinosaurs and even modern birds, with evidence suggesting that they were covered in feathers, which may have played a role in insulation or display.

A surprising discovery

“Here, we describe a new and unusual species of the therizinosaurid Duonychus tsogtbaatari, recovered from the lower Upper Cretaceous Bayanshiree Formation of the Gobi Desert of Mongolia,” wrote the researchers.

Standing about 10 feet (3 meters) tall and weighing around 573 pounds (260 kilograms), Duonychus likely used its massive claws to forage by grasping tree branches and pulling down vegetation.

Its hands had only two large fingers, which is an oddity among dinosaurs. While scientists believe those claws were mainly used to grab plants, they may have also served other purposes – like showing off or defending against threats.

“They weren’t predators, but they could defend themselves with those claws. They were big and very sharp,” said Zelenitsky.

Like sloths, but with attitude

The best modern comparison for these claws might be found in sloths, whose curved nails help them cling to tree limbs, noted Zelenitsky. But Duonychus adds a prehistoric twist.

The preservation of the keratin sheath is a rare scientific win. Most dinosaur fossils don’t include this detail, which makes the discovery particularly valuable.

“I’ve seen fragments from other specimens from the Gobi, but never a whole sheath like this,” said David Hone, a paleontologist at Queen Mary University of London, who was not part of the study.

“The kind of preservation here, which is common to the vast majority of dinosaur bearing formations, doesn’t usually preserve keratin.”

Hone emphasized that there’s a murky relationship between the bone and keratin structures, so this specimen helps scientists understand better how the claw really looked and functioned.

Two-clawed dinosaur with giant arms

Therizinosaurs are often compared to the character Edward Scissorhands, thanks to their long, scythe-like claws. Duonychus takes the comparison even further, with its two-fingered limbs.

“But this one is unique in having only two fingers on each of its giant arms, so they really do look like oversized tongs you might use when barbequing,” said Steve Brusatte, a professor of paleontology at the University of Edinburgh who was not involved in the study.

Two-fingered dinosaurs were relatively rare. While T. rex also had just two fingers, its stubby arms weren’t all that useful. In contrast, Duonychus used its limbs actively in daily life, especially when it came to feeding.

“But whereas T. rex probably wasn’t using its pathetic little arms for much, and definitely not for combat or subduing prey, these therizinosaurs were using them as an integral part of their feeding strategy,” said Brusatte.

A dinosaur like no other

The fossil was uncovered in Mongolia’s Gobi Desert and included not just the iconic claws but also parts of the spine, tail, hips, arms, and legs.

This gives paleontologists a much more complete view of the dinosaur’s overall structure. And like other therizinosaurs, it likely had feathers, adding yet another layer to its strange appearance.

“This is yet another example of a wonderful new dinosaur that we couldn’t have dreamed ever existed if we didn’t find its fossils,” said Brusatte.

From its sloth-like claws to its feathered body and awkward gait, Duonychus tsogtbaatari is a reminder that the past was far weirder – and far more interesting – than we might expect.

Details of the study were published in the online journal iScience.

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