Tericinosaurus, a peculiar new species, is known to have only two fingers

Paleontologists excavated the fossilized remains of a new and rare Terazinosaurus dinosaur with atypical hands in Mongolia.

Duonychus tsogtbaatari He lived in what is now Mongolia during the late Cretaceous period, between 1995 and 90 million years ago.

The new species belongs to Teresino Sauriaa group of herbivorous or omnivorous theropod dinosaurs that lived in Asia and North America during the Cretaceous period.

“Therizinosauria is a clade of a rare herbivorous or omnivorous theropod dinosaur known from Cretaceous sediments in Asia and North America,” wrote paleontologist Yoshitsugu Kobayashi Yosh and his colleagues at the Hokkaido University Spine Museum on paper.

“This clade is most recognizable in the triductyl (three fingers) hand with three large clawless non-guals, as illustrated by its large body. Tericinosaurus From the latest Cretaceous period in Mongolia. ”

“Like a more primitive member of the clade Falkarius, Beipiaosaurusand JianChangosaurus There were relatively small Unguals compared to the more derived forms Ellianaurus, Nothronychusand in particular Tericinosaurus. ”

“As herbivorous or omnivorous theropods with long necks and small leaf-shaped teeth, their unusual evolution of hands may have played an important role in the feeding ecology of this clade.”

According to paleontologists, Duonychus tsogtbaatari is a medium sized terazinosaurus and estimates weight is about 260 kg.

This dinosaur fossil is Bien Series Formation Gobi Desert, Ömnögovi Province in southeastern Mongolia.

“The specimen was a six posterior joint vertebrae, six distinct sacral vertebrae with sacrum ribs, frontline coccyx, several dorsal ribs, partial left shoulder blade and coracoid, coracoid, umeri, ulnae, radi, rightan, right, right, pubest, right, right, right, right, right, right, right, right, right, the proximal end of left ischemia,” the researchers wrote.

Reconstructed skeletons and selected elements Duonychus tsogtbaatari. Image credits: Kobayashi et al. , doi: 10.1016/j.isci.2025.112141.

Duonychus tsogtbaatari Unlike other Tericinosaurus in that their hands only have two fingers, rather than three fingers.

“As for other Therizinosaurus, this new species is unique in having a definitive didigital hand,” the scientist wrote.

“The specimen also preserves the complete three-dimensional sheath, representing the keratinous claws, among non-Pallavian theropods.”

Well-preserved specimens Duonychus tsogtbaatari It provides insight into the functional aspects of that kind.

“Saved keratin nails based on abdominal curvature and nail attack angle Duonychus tsogtbaatari “The author writes, reveals features within the scope of scansorial (climbing), tenasorial (grappling).”

“Of these functions, herbivorous or omnivorous diet and body size Duonychus tsogtbaatariLike other terazinosaurus, it suggests the use of amps that helps grasp branches, such as chameleons and some mammals (e.g., Southern Tamandua, Alitant), or to grip, raise, or manipulate bait (e.g., bird birds).

“Even though there are only two functional numbers, Duonychus tsogtbaatari Given the extreme flexion at Ungual joints and the strong curvature of the keratin nails, it may have been an effective Glasper, a feature unknown in other terazinosaurus. ”

“Based on the shape and dimensions of the keratin nail dimensions, Duonychus tsogtbaatari They could have grabbed branches or herds of vegetation up to about 10 cm in diameter. TericinosaurusI’ll suggest that Duonychus tsogtbaatari Foraging behaviors may have been more selective. ”

“Manus Duonychus tsogtbaatariits powerful flexion and claw curvature further supports that the derived Therizinosaurus manus is likely to be provided in a rake or hook-and-pull function to bring vegetation into the mouth during feeding, as previously suggested. ”

“The claws usually have a dominant function for hook-and-pull foraging in the most derived Theresinosaurus, but these structures may also be used for other purposes such as territory, defense, courtship, and play.”

“In addition to the unexpected morphological diversity of the Manus of Telesinosaurus (i.e., director), Duonychus tsogtbaatari It reveals greater species richness of Tericinosaurus in the ecosystem of the Baiancily Formation than previously recognized,” they concluded.

Team’s paper It was published in the journal on March 25th Iscience.

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Yoshitug Kobayashi et al. Didictilteresinosaurus with keratinous nails preserved since the late Cretaceous period in the late Mongolia. IsciencePublished online on March 25th, 2025. doi:10.1016/j.isci.2025.112141