A simulation picture of Linhenykus
Scientists have discovered a new dinosaur species whose members were similar in size to a parrot but only had one finger.
Scientists view that rare solitary digit as evidence that the evolution of dinosaurs was more complex than they first believed.
The new dinosaur was found in rocks formed from 84 million to 75 million years ago in Linhe, a city near the Yellow River.
The species belongs to a family within the carnivorous dinosaurian group theropods, which later gave rise to modern birds, according to Xu Xing of the Institute of Vertebrate Palaeontology and Paleoanthropology, which is under the Chinese Academy of Sciences.
The new dinosaur, called Linhenykus, "most likely grew to a few feet tall and weighed only as much as a large parrot", said Xu, who led the international team of scientists that discovered the species.
Unlike previously known types of theropods, this dinosaur is unusual in having hands with just one large claw, which may have been used to dig out insects like ants, said the scientists in a report to be published online on Tuesday in the journal Proceedings of the National Academy of Sciences.
The unusual physical attribute makes the specimen the only dinosaur known to have one finger. That uniqueness is what most piques the interest of scientists, Xu said.
He and others believe theropod dinosaurs started with five fingers but evolved in later forms to have only three fingers. Some eventually became birds.
Scientists think that, in the course of evolving into birds, various related dinosaur species gradually lost two of their five fingers, likely in response to changes in the environment.
But in recent decades, with the discovery of more theropods that, like the two-finger Tyrannosaurus, have fewer than three fingers, scientists have come to agree that the evolution of dinosaurs' hands was brought about more by random mutations than by basic adaptive evolution.
"The discovery of the one-fingered dinosaur only reconfirms the fact that digital reduction is a striking evolutionary phenomenon, far more complicated than we've expected," Xu said.
