Scientists discover weird Mongolian dinosaur that wielded 'sharp, huge' claws

The specimen belonged to the group called Therizinosaurs, feathered ground-dwellers known for their huge claws, leaf-shaped teeth and long necks ending in small heads.

Scientists have discovered a new species of dinosaur in Mongolia's Gobi Desert. Called Duonychus tsogtbaatari, the dinosaur has 2-foot-long clawed fingers on each hand, one fewer than its fellow Therizinosauria.

Duonychus, which means “two claws” in Greek, stood about 10 feet tall and weighed roughly 570 pounds and belonged to the group of dinosaurs called Therizinosaurs, which were characterized by an odd set of traits: huge claws believed to have been used to shear leaves off trees, leaf-shaped teeth, backward-facing hip bones and a long neck ending in a small head, and it was covered in down and quill-like feathers.

“It kind of blew my mind,” the lead author of a study published Tuesday in the journal iScience, Yoshitsugu Kobayashi, an associate professor at the Hokkaido University Museum, told NBC News by email. “I felt this rush of excitement, like, ‘Wait… am I actually looking at something completely new here?’”

Therizinosaurs were already the “weirdest dinosaurs out there,” Kobayashi said. “Duonychus takes that weirdness and pushes it further. It’s like evolution said, ‘Let’s try something different,’ and just ran with it.”

Therizinosaurs lived in Asia and North America during the Cretaceous Period, 145 million to 66 million years ago.

Despite having only two claws, Duonychus was an “effective grasper” that could reach branches or swaths of vegetation up to nearly 5 inches in diameter.

“Dinosaurs weren’t just stuck in one body plan — they were constantly experimenting, evolving, doing weird stuff,” Kobayashi added, calling them “total oddballs.” 

A study co-author, Darla Zelenitsky, an associate professor at the University of Calgary in Canada, described Duonychus' claws as “sharp and huge,” about 1 foot long.

Duonychus would have used their claws to grasp and pull vegetation to the mouth during feeding, Zelenitsky said in an email Wednesday, adding that claws could also have had other functions, like self-defense or grappling.

Though Therizinosaurs were part of the theropod group, which included meat-eaters like Tyrannosaurus and Spinosaurus, Duonychus mainly ate leaves from large shrubs and trees.

The specimen was excavated in 2012 by researchers from the Mongolian Academy of Sciences' Institute of Paleontology from the Gobi Desert’s Bayanshiree Formation, which dates back 90 million years and is known for its exceptional diversity of Therizinosaurs.

The fossil was a partial skeleton without a skull and legs, but the hands were “exceptionally preserved,” according to the study. The Duonychus individual was not fully mature.

It’s a “great new discovery, and the two claws is interesting,” said Michael Benton, professor of vertebrate paleontology at the University of Bristol in the U.K., who was not involved in the study.

Dinosaurs used to have five fingers, just like human beings, but they quickly lost two over time, with most dinosaurs having three fingers, Benton said Wednesday.

“So, to go down to two was unusual,” he said.

The number of digits doesn’t matter when it comes to hooking and pulling, Benton said, adding that the third finger may have been an “encumbrance” due to its short length.

Fossil records of Therizinosauria are “notably abundant” in Cretaceous deposits across eastern Asia, particularly in Mongolia and China, according to the study.