Youngest Therizinosaur Fossil Found in Japan Actually Belongs To A New Dinosaur Species

Scientists have reported the fossil of a therizinosaur that was found in maritime sediments in Japan. This fossil is the first of its kind to be discovered in marine sediments anywhere in Asia.

Therizinosaurs were a large group of theropod dinosaurs (dinosaurs with hollow bones and three-toed limbs) that were mostly herbivorous. Fossil records from China and Mongolia, as well as Japan, are particularly rich in therizinosaurus fossils, which were initially discovered in Asia.

Professor Yoshitsugu Kobayashi of the Hokkaido University Museum and Anthony R. Fiorillo of Southern Methodist University (SMU) led a team of scientists from Japan and the United States to describe a new species of therizinosaurid from Japan and provide new insights into the function of therizinosaur claws. The research was published in the scientific journal Scientific Reports.

Ryuji Takasaki of Okayama University of Science, Tsogtbaatar Chinzorig of North Carolina State University and the Mongolian Academy of Sciences, and Yoshinori Hikida of the Nakagawa Museum of Natural History are among the study’s co-authors.

The fossil presented in this paper is made up of a partial vertebra, a partly wrist, and a partial forefoot that was collected in 2008 from the Osoushinai Formation in Nakagawa, Hokkaido. It was thought to belong to a therizinosaur at the time and was described as belonging to a Maniraptoran dinosaur. However, due to a dearth of comparable data at the time, confirmation was difficult.

Recent discoveries have led to a plethora of information that permits the classification of therizinosaurs based on the anatomy of the forefoot claws, therefore the scientists decided to revisit the specimen. This is the third therizinosaur discovered in Japan; however, the first two have yet to be identified. From the early Cretaceous to the Late Cretaceous, therizinosaurs lived in Asia. They had huge claws on their hands. Therizinosaurs are split into two groups based on the morphology of their claws, which is linked to their function.

The claws of Paralitherizinosaurus japonicus, a new species of therizinosaur from Japan, were compared to the claws of many other species of therizinosaur. Based on four shared, derived traits, the analysis of the data put P. japonicus in the same group as the derived therizinosaurs. An examination of the claw morphology, including the length and shape of the claw base, reveals that the claws of basic therizinosaurs are generalist and not specialized, whereas the claws of developed therizinosaurs were specialized to hook and draw plants to the mouth for grazing.

Therizinosaur fossils from Paralitherizinosaurus japonicus are the most recent to be discovered in Japan. Its discovery suggests that therizinosaurs lived in Asia for a significantly longer period of time and covered a much bigger geographical range than previously thought. It’s also the first therizinosaur found in Asian sea strata. This, together with a relic from Utah, USA, demonstrates that some of the therizinosaurs evolved to live in coastal habitats.

Fiorillo, a research professor in SMU’s Roy M. Huffington Department of Earth Sciences, a senior research fellow at SMU’s ISEM, and curator emeritus of the Perot Museum of Nature and Science, said, “This study also tells us how much more we still have to learn about the incredible history of life on Earth.”

Image Credit: Genya Masukawa

You were reading: Palaeontologists Just Found a New Dinosaur Species in Japan