A team of palaeontologists headed by experts from the University of Edinburgh has discovered a new species of toothless, two-fingered dinosaur.
Multiple complete skeletons of the feathered species – named Oksoko avarsan – have been unearthed in Mongolia’s Gobi Desert, providing critical clues about evolution.
The dinosaurs, which were omnivorous and grew to about two-metres long, thrived more than 68 million years ago.
They had two functional digits on the end of each forearm and had a large toothless beak similar to modern parrots.
According to the team, the fossils provide the first evidence of digit loss in the three-fingered dinosaur family known as oviraptors.
The new species had one less finger than its close relatives, suggesting an adaptability which enabled the animals to spread during the late Cretaceous period, researchers said.
The discovery that they could evolve forelimb adaptations suggests the group could alter their diets and lifestyles, and enabled them to diversify and multiply, the team claimed.
Dr Gregory Funston of the University of Edinburgh said: “Oksoko avarsan is interesting because the skeletons are very complete and the way they were preserved resting together shows that juveniles roamed together in groups.
“But more importantly, its two-fingered hand prompted us to look at the way the hand and forelimb changed throughout the evolution of oviraptors, which hadn’t been studied before.
“This revealed some unexpected trends that are a key piece in the puzzle of why oviraptors were so diverse before the extinction that killed the dinosaurs.”
According to the researchers, oviraptors gradually lost their third finger over the course of their evolutionary history as it first reduced in size and then disappeared altogether.
Image: The skeletons reveal interesting clues about dinosaur evoluton
The changes to the creatures’ arms and hands took place as they migrated to new geographic areas, specifically to what is now North America and the Gobi Desert.
Oksoko avarsan, like many other prehistoric species, also appeared to be very social as juveniles – with the remains of four young dinosaurs preserved resting together.
The study, published in the journal Royal Society Open Science, was funded by The Royal Society and the Natural Sciences and Engineering Council of Canada.
It also involved researchers from the University of Alberta and Philip J Currie Dinosaur Museum in Canada, Hokkaido University in Japan, and the Mongolian Academy of Sciences.