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Duonychus

Say it: doo-ON-ih-kus

Name means: “two-clawed”1

Ate: PlantsOdd feathered dinosLate Cretaceous

Duonychus was a weird, plant-eating dinosaur with only two fingers on each hand, unlike most other meat-eating dinosaurs. It used its big, curved claws to grab branches and pull leaves close to its mouth. It lived in what is now Mongolia during the Late Cretaceous Period.1

Lived

100 to 84 million years ago5

Late Cretaceous

Fossils found in

Urlibe Khudak locality, Bayanshiree Formation, Gobi Desert, Mongolia5 1

Food

Plants5 1

Length

3 m2 3

estimate from press release

Weight

259 kg to 268 kg1 4

estimate from ulna and metacarpal II; individual not fully mature

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

How long was it?

How heavy was it?

as heavy as 9 big dogs

as long as 3 dogs nose to tailas long as 17 bananas end to endas heavy as 54 watermelons

How big was Duonychus compared to YOU?

Just maths in your browser. Nothing is saved or sent anywhere.

cool stuff

Fun facts

Duonychus is the first therizinosaur known to have only two fingers on each hand, instead of the usual three.1

The fossil includes a rare preserved keratinous claw, the hard material that covered the bone, which is almost never found in dinosaurs.1

Its name means 'two-clawed', and the species name honors Mongolian paleontologist Khishigjav Tsogtbaatar.1

Duonychus lived about 95 to 89 million years ago, during the Cenomanian to Santonian stages.1

The strong curve of its claws and high flexibility suggest it was a grasping animal, using its hands to pull down branches.1

Duonychus is a therizinosaur, a group of dinosaurs that, despite being meat-eater relatives, turned to eating plants.1

AI-made picture of Duonychus — An AI-made picture of how Duonychus might have looked, made by a computer from what scientists know. It is a guess: the real animal may have looked different, and nobody knows its true colours.

you asked

Most asked questions about Duonychus

?How big was Duonychus?

About 3 metres long and weighed around 260 kilograms.2

?What did Duonychus eat?

It was a plant-eater. It used its big, curved claws to grab branches and pull leaves to its mouth.2 1

?Why did Duonychus have only two fingers?

Scientists are not sure why, but it is the first therizinosaur known to have only two fingers on each hand instead of three. This helped it grasp vegetation.2 1

?Did Duonychus have feathers?

The fossil does not preserve feathers, but many therizinosaurs are thought to have had feathers. Duonychus was a theropod dinosaur, and many theropods had feathers.2

?When did Duonychus live?

It lived about 95 to 89 million years ago, during the Late Cretaceous Period.2 1

?Could Duonychus climb trees?

Probably not. Its claws were best for grasping branches and pulling them down to eat, not for climbing.1

Ask Rex about Duonychus

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Myth buster

Myth: Some people think Duonychus was a fast, fierce predator because it had big claws.

Truth: Actually, Duonychus was a plant-eater, and its claws were for grasping vegetation, not for hunting.1

For dino experts

Scientific name: Duonychus
Named by: Kobayashi et al. 20255
Group: Odd feathered dinos
Family / clade: Therizinosauridae5
Classification: Theropoda > Therizinosauria5
Age of the rocks: 100 to 84 million years (Cenomanian / Santonian)5
Rock formations: Baynshire5
Countries: Mongolia5
Fossil records: 1 in the Paleobiology Database5
Discovery: Duonychus was named by Kobayashi and colleagues in 2025, based on a partial skeleton found in the Gobi Desert, Mongolia. The fossil was collected from the Urlibe Khudak locality.5 1
Still debated: Scientists are still debating why Duonychus lost one finger, since most therizinosaurs had three. It might have helped it grasp branches more effectively.1

Where the facts come from

Didactyl therizinosaur with a preserved keratinous claw from the Late Cretaceous of Mongolia (pmc.ncbi.nlm.nih.gov)
Duonychus (Wikipedia) (Wikipedia)
Weird Mongolian dinosaur wielded 'big, sharp and nasty' claws (reuters.com)
Didactyl therizinosaur with a preserved keratinous claw from the Late Cretaceous of Mongolia: iScience (cell.com)
Duonychus in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

Every fact on this page has a number that points to its source. If we got something wrong, sorry, we are dino fans, not a science journal. Tell us at [email protected] and we will fix it.

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