Paleontologists announced the discovery of a new dinosaur species, Duonychus tsogtbaatari, in Mongolia in a study published in the journal iScience led by Yoshitsugu Kobayashi from Hokkaido University.
Duonychus tsogtbaatari lived approximately 90 million years ago and is notable for its unusually well-preserved claws. The fossil, unearthed in the Gobi Desert, includes parts of the spine, tail, hips, and limbs, providing researchers with insights into its physical characteristics, according to Scinexx.
Measuring over three meters in length and weighing around 270 kilograms, Duonychus tsogtbaatari was an impressive creature. Its most striking feature was its two curved claws about 30 centimeters long on each hand, equipped with preserved keratin sheaths—an exception in paleontology since keratin rarely fossilizes. "The best-preserved claw of Duonychus exhibits extreme curvature and increased length by more than 40% due to the keratin sheath," Scinexx reported.
The species is notable because it is the first known therizinosaur with only two fingers on each hand, breaking the common three-finger pattern in its family. This discovery exemplifies a phenomenon known as digital reduction, where species evolve to have fewer digits over time. Duonychus tsogtbaatari represents one of five known lineages that independently evolved to have only two fingers on each hand, contributing to the understanding of theropod evolution. The genus name Duonychus means "two claws" in Greek, referring to its unusual limbs.
"This is by far the largest three-dimensional claw found completely preserved," said Darla Zelenitsky, an associate professor at the University of Calgary and co-author of the study. The discovery of the intact keratin sheath provides a more accurate idea of the actual size and potential use of the claws, which researchers believe were used primarily for grasping vegetation.
Despite its fearsome appearance, Duonychus tsogtbaatari was not a carnivore but likely an herbivore or omnivore. It belonged to a group of theropods known as therizinosaurs, characterized by long necks, wide torsos, small skulls, feathers on the body, and huge claws on the hands. These dinosaurs used their powerful claws to pull down branches and feed on leaves, adapting to an arid landscape with scattered vegetation.
The discovery has sparked comparisons to sloths, giraffes, and even the iconic film character Edward Scissorhands, with researchers noting its bizarre appearance resembling a giant, pot-bellied sloth. "They look like large tongs you could use for a barbecue," said Steve Brusatte, a paleontologist.
Researchers do not rule out other uses of the claws, such as defense, digging, or display. "They were not carnivores, but they could definitely defend themselves with these claws," said Zelenitsky. "Evolution reduced that number in different lineages in independent ways," Infobae reported. The shape of the hands with only two fingers suggests a pattern of evolutionary specialization, even though more fingers might be advantageous for grasping vegetation.
The species name tsogtbaatari honors the Mongolian paleontologist Khishigjav Tsogtbaatar, recognizing his contributions to the field.
"This is another example of a wonderful new dinosaur, whose existence we would never have imagined if we hadn't found its fossils," said Steve Brusatte. "Finding a fingernail in such good condition is rare because fingernails usually decompose long before they can fossilize," Vice News reported.
"The preserved keratin shows how curved these claws could be. That provided a clear advantage to a dinosaur that was raking branches toward itself with such claws," said Stephan Lautenschlager, a paleontologist at the University of Birmingham.
In species like Duonychus, the transformation of the hands seems to have been an efficient response to specific dietary needs in an arid landscape with scattered vegetation. The anatomical change is not related to predation but to a functional adaptation to its environment and diet.
The article was written with the assistance of a news analysis system.