New dinosaur species having knives for claws discovered in Japan's Hokkaido

Researchers from Japan's Hokkaido University and the Southern Methodist University in the US have confirmed finding the fossil of a new dinosaur species that roamed around Asia from the early to the late Cretaceous period- approximately 145 million to 66 million years ago. Belonging to the group Therizinosaurs, the newly found fossilised claw has been associated with the species named Paralitherizinosaurus japonicus. According to the experts from the Hokkaido University, the Therizinosaurs were first discovered in Asia as the fossil records in countries such as China and Mongolia are rich in their fossils. Fragments of their remains have also been reported from Japan.

Dinosaur which had knives for fingers

(Claw-shaped fossil of Paralitherizinosaurus japonicus; Image: Yoshitusgu Kobayashi/Hokkaido University)

One of the most intriguing features of the dinosaur was its vicious claws which had knives for fingers. However, the researchers have confirmed that they were not to slash their prey but to hook and pull vegetation to the mouth for grazing. The Therizinosaurs were a large group of dinosaurs that had hollow bones and three-toed limbs and were primarily herbivores.

Notably, the fossil was first discovered in 2008 in the Osoushinai Formation, which is a fossil-rich geological feature in Hokkaido's Nakagawa. Initially, the fossil was described as belonging to a manitoraptan dinosaur, and was believed to belong to a therizinosaur but "the lack of comparative data at the time made confirmation impracticable", Hokkaido University's official release said.

After a few years, the researchers revisited the fossil and classified the Paralitherizinosaurus japonicus, meaning 'reaper reptile by the sea from Japan', into two different classes- basal and derived therizinosaurs. A thorough analysis of their claws revealed that the claws of basal therizinosaurs are generalized and not for a specific use, while the claws of derived therizinosaurs were specialised to help in feeding itself. 

"Paralitherizinosaurus japonicus is the youngest occurrence of therizinosaur remains in Japan. Its discovery indicates that therizinosaurs in Asia existed over a much longer timescale, and a much larger geographical area, than previously known", the University said in a statement. Interestingly, it is also the first therizinosaur record from marine sediments in Asia and the finding suggests that some of the derived therizinosaurs were adapted to coastal environments.