Researchers identified a new dinosaur species from Mongolia’s Gobi Desert whose hands carried two enlarged clawed fingers rather than the three typical of related animals. Named Duonychus tsogtbaatari, the animal belonged to Therizinosauria, a group of feathered theropods known for long necks, small heads, leaf-shaped teeth and prominent claws.
The partial skeleton was excavated in 2012 by the Institute of Paleontology at the Mongolian Academy of Sciences. It came from the Bayanshiree Formation, a deposit dating to about 90 million years ago. Although the fossil lacked a skull and legs, its hands were preserved well enough to reveal the unusual digit arrangement. The individual had not yet reached full maturity. The Bayanshiree context also tied the hand to a formation already noted for an unusually varied assemblage of these dinosaurs.
A study describing the find appeared in the journal iScience. Study leader Yoshitsugu Kobayashi, who worked as an associate professor with Hokkaido University Museum, said the two-finger configuration was immediately striking. The genus name Duonychus refers to “two claws” in Greek.
Scientists estimated that the dinosaur stood around 10 feet tall and weighed approximately 570 pounds. Each complete clawed finger measured about 2 feet, while the claw itself was roughly 1 foot long. Despite the reduced digit count, researchers considered the hand capable of grasping vegetation approaching 5 inches in diameter.
That interpretation fits the feeding anatomy attributed to therizinosaurs. Though members of Theropoda, a broader lineage that also contained large predators such as Tyrannosaurus and Spinosaurus, Duonychus primarily consumed leaves from shrubs and trees. Study co-author Darla Zelenitsky of the University of Calgary said the animal probably drew vegetation toward its mouth with its claws. She also left open possible defensive or grappling uses.
During the Cretaceous, from 145 million to 66 million years ago, therizinosaurs ranged across parts of both the Asian and North American continents. Their remains are particularly common in eastern Asian deposits, including sites in Mongolia and China.
Michael Benton, a University of Bristol vertebrate paleontologist who was not involved in the research, called the discovery significant and noted the rarity of reducing the hand to two digits. Early dinosaurs had five fingers, while many later forms retained three. Benton suggested that a shortened third finger may no longer have helped with hooking and pulling, making its loss less consequential.
The fossil therefore offers more than a visually distinctive species. It shows that therizinosaurs could preserve an effective grasping function while altering the basic structure of the hand, broadening scientists’ picture of how this already unusual lineage diversified.
