An international team of paleontologists and Earth scientists has identified fossilized remains as a two-clawed therizinosaur. The fossils were unearthed more than a decade ago in Mongolia. Their paper is published in the journal iScience.
In 2012, a team of researchers from the Mongolian Academy of Sciences unearthed the fossilized remains of a therizinosaur—a two-legged dinosaur known for its long claws—in the Gobi desert. For several years, the fossils remained in storage. In this new study, the researchers analyzed the fossils and discovered the largest three-dimensional preserved dinosaur claws ever found.
The fossil set included both of the dinosaur’s arms, including claws, part of its pelvis and much of its backbone, and they are three-dimensional, not flat outlines in rock. The fossils date to approximately 90 million years ago and belong to a previously unknown dinosaur, thus representing a new species. The researchers gave it the name Duonychus tsogtbaatari. They suggest it likely would have been approximately 3 meters long and weighed approximately 270 kilograms.
The researchers note that it is the first known therizinosaur species to have just two fingers—all the others have three. The claws are approximately 30 centimeters long, and show evidence of a keratin sheath. Because keratin decays quickly, it is not usually fossilized. The paleontologists say it was a stroke of good luck that the fossils were preserved in 3D, noting that they give a much clearer picture of what the dinosaur would have looked like when alive.
The team suggests the reason the dinosaur had just two claws was likely due to its manner of eating. Two claws suggest vegetation was pulled down and thrust into the mouth. Two claws, they note, would have made each claw stronger than if there were three, allowing the dinosaur to grab thicker branches.
More information: Yoshitsugu Kobayashi et al, Didactyl therizinosaur with a preserved keratinous claw from the Late Cretaceous of Mongolia, iScience (2025). DOI: 10.1016/j.isci.2025.112141. www.cell.com/iscience/fulltext … 2589-0042(25)00401-8
Journal information: iScience
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