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1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteDuonychus tsogtbaatari looked like a nightmare from the Late Cretaceous: a heavily built theropod with a claw roughly 30 centimeters long. But its hands tell a more interesting story. This newly described Mongolian dinosaur had only two functional fingers, and researchers think those powerful claws were used mainly to hook, grasp, or pull vegetation—not to disembowel prey.
Duonychus tsogtbaatari looked like a nightmare from the Late Cretaceous: a heavily built theropod with a claw roughly 30 centimeters long. But its hands tell a more interesting story. This newly described Mongolian dinosaur had only two functional fingers, and researchers think those powerful claws were used mainly to hook, grasp, or pull vegetation—not to disembowel prey.
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What was discovered?
The fossil was found in 2012 in Mongolia’s Gobi region during work connected with construction of a water pipeline. Researchers later examined a partial, semi-articulated skeleton from the Bayanshiree Formation in Ömnögovi Province, southeastern Mongolia.
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Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →The Bayanshiree Formation dates to the lower Upper Cretaceous, approximately 90 million years ago. The specimen includes much of the backbone, parts of the pelvis, both forelimbs, and both hands. That combination is unusually informative because the hands are central to understanding how this animal lived.
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The dinosaur was formally named Duonychus tsogtbaatari in a scientific description published in iScience in 2025. The genus name refers to its two-digit hands. The species name honors Mongolian paleontologist Khishigjav Tsogtbaatar.
A two-fingered dinosaur in a mostly three-fingered group
Duonychus belonged to the therizinosaurs, an unusual branch of theropod dinosaurs. Theropods include famous predators such as Tyrannosaurus, but the group also includes modern birds and several lineages that evolved very different body shapes and diets.
Therizinosaurs are especially recognizable for their long necks, broad bodies, feathered coverings in some species, and enlarged hand claws. Many therizinosaurs had three-fingered hands. Duonychus is notable because each hand retained only two functional manual digits.
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This was not necessarily a completely isolated evolutionary oddity. The study treats digit reduction as part of a broader pattern that evolved independently in multiple theropod lineages. Losing a digit can be advantageous when the remaining digits become more specialized for bearing force, gripping, or manipulating food.
The claw had a rare keratinous sheath
The most visually striking part of the discovery is not just the claw’s size but its preservation. One claw retained a three-dimensional keratinous sheath over the underlying bone.
Keratin is the tough biological material found in human fingernails and hair. It normally decays long before fossilization, so preserved keratinous coverings are rare. A bony claw alone can give researchers an incomplete picture: in life, the keratin sheath would have extended and reshaped the visible claw beyond the bone.
The preserved sheath therefore offers a better estimate of the claw’s living outline. Reports describe the claw as approximately 30 centimeters—about a foot—long. It may represent the largest fully preserved dinosaur claw known, but that claim needs careful wording. Other dinosaurs, including Therizinosaurus, are known for claw bones that were longer.
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Were the claws for hunting?
Probably not, although claw shape alone cannot prove an animal’s diet.
The researchers’ functional interpretation is that Duonychus used its curved claws to hook, grasp, or pull vegetation toward its mouth. Two robust digits could have helped it apply force to thicker branches or other substantial plant material.
That makes the animal’s hands an example of a useful evolutionary contrast: equipment that looks predatory can serve a plant-feeding role. The claws would certainly have been dangerous weapons if used defensively, but their anatomy is also consistent with a specialized vegetation-grasping behavior.
The safest description is that Duonychus was probably herbivorous or possibly omnivorous, with evidence favoring plant handling rather than active predation. Scientists cannot observe its behavior directly, so terms such as “probably,” “may have,” and “consistent with” matter here.
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A broad comparison used in reporting is that therizinosaurs may have filled roles somewhat analogous to large sloths or pandas in the Cretaceous: plant-focused animals equipped to reach, pull, or process vegetation. That is an ecological analogy, not a claim that they were literally related to or behaved exactly like either modern animal.
How large was it?
Available estimates place Duonychus at roughly 3 meters long and approximately 260–270 kilograms. That is a substantial animal, but the measurements are estimates based on incomplete remains, not precise readings from a complete skeleton.
For that reason, it is misleading to call Duonychus the largest dinosaur in Mongolia or the largest therizinosaur. Its significance lies in the unusual combination of two-digit hands, powerful claws, and rare three-dimensional keratin preservation—not simply in body size.
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Why this fossil matters to paleontologists
The specimen contributes to several areas of dinosaur research at once:
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- Hand evolution: The two-fingered hands provide evidence for how digit reduction occurred in a theropod lineage.
- Claw function: The shape and robust construction help test whether the claws were better suited to grasping vegetation than tearing flesh.
- Life appearance: The preserved keratin sheath gives a more realistic picture of the claw than the bony core alone.
- Fossil preservation: The three-dimensional preservation of a normally decay-prone structure provides clues about how unusual fossil material can survive.
- Mongolian paleontology: The find adds to the record of diverse Cretaceous ecosystems preserved in the Gobi region.
The discovery does not show that scientists have misunderstood all therizinosaurs, nor does it overturn dinosaur biology. Its value is more specific: it supplies an unusually informative data point for studying how a theropod hand became reduced and specialized.
From a pipeline excavation to a formal species
The path from discovery to publication took years. The remains were recovered in 2012, but fossil collection is only the beginning of paleontological work. Researchers must stabilize and prepare the specimen, identify the preserved bones, compare them with related animals, document its geological setting, and determine whether its anatomy justifies naming a new species.
In this case, the partial skeleton was important because it preserved both forelimbs and hands rather than a single isolated claw. Comparing the limbs, digits, claw bones, and surrounding skeleton allowed the researchers to interpret the hand as part of a functioning anatomical system.
A later correction to the 2025 publication supplied missing ZooBank registration information required for the formal nomenclatural acts. The correction provided identifiers for the publication, genus, and species. It did not change the study’s findings or conclusions.
What “two-clawed” does—and does not—mean
The name Duonychus can make it sound as though the animal had only two claws total. More precisely, the dinosaur had two functional manual digits on each hand, with each digit bearing a large claw. “Two-fingered” is therefore the clearest reader-friendly description.
The name also should not be taken as evidence that the dinosaur was automatically more dangerous than three-fingered relatives. The number of digits tells us about hand anatomy; it does not, by itself, reveal whether the animal hunted, scavenged, defended itself, or fed on plants.
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For budding fossil hunters
Duonychus was recovered through real fieldwork in Mongolia, followed by years of laboratory study. A dinosaur fossil excavation kit can offer children a small, educational version of the digging and preparation experience, but it is a toy or classroom activity—not genuine Mongolian fossil material and not a replica of Duonychus.
For a good learning activity, have children record what they uncover, sketch the “specimen,” distinguish the hard fossil-like material from its surrounding matrix, and explain which observations are direct evidence versus interpretation. That mirrors an important part of paleontology: a claw’s shape is observable, while its precise behavior must be inferred.
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Duonychus tsogtbaatari was a roughly 3-meter-long therizinosaur from southeastern Mongolia, formally described in 2025 from a fossil discovered in 2012. Its hands had two functional digits, and one approximately 30-centimeter claw preserved a rare keratinous sheath.
Despite its intimidating appearance, the best-supported interpretation is not that it was a giant clawed predator. Researchers suggest the claws helped it grasp or pull vegetation. The fossil’s real scientific importance is the evidence it provides about digit loss, specialized hand function, and exceptional preservation in the Cretaceous rocks of Mongolia.
Frequently Asked Questions
What was Duonychus tsogtbaatari?
Duonychus tsogtbaatari was a therizinosaurid theropod dinosaur formally described in 2025. It lived in what is now southeastern Mongolia during the Late Cretaceous, roughly 90 million years ago.
How many fingers did Duonychus have?
The known fossil indicates that each hand had two functional manual digits. One claw was approximately 30 centimeters long and preserved a rare keratinous sheath over the bony core.
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Researchers suggest that its strongly curved claws helped it hook, grasp, or pull vegetation toward its mouth. This is an anatomical inference, not a direct observation, and the evidence supports a probably herbivorous or possibly omnivorous animal rather than proving a strictly plant-only diet.
How big was the dinosaur?
Estimates place it at about 3 meters long and 260–270 kilograms. Because the skeleton is incomplete, these figures are approximate.
The Bottom Line
Duonychus tsogtbaatari was a two-fingered Mongolian therizinosaur with an approximately 30-centimeter keratin-covered claw. Its claws looked fearsome, but their anatomy was probably adapted for grasping and pulling vegetation rather than hunting prey.
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