Scientists understand why vegan dinosaurs have huge claws

Paleontologists have described a new dinosaur from the therizinosaur group, the fossils of which were found in

Upper Cretaceous deposits of Japan aged from 83.6 to 72.1 Ma. The dinosaur was named Paralitherizinosaurus japonicus.

Therizinosaurs were a large grouppredominantly herbivorous theropod dinosaurs (dinosaurs with hollow bones and three-toed limbs). They were first discovered in Asia. As you know, in Asian countries such as China and Mongolia, there are a lot of fossils of therizinosaurs, in Japan they are not so common.

Scientists from Japan and the USA led by Prof.Yoshitsugu Kobayashi of the Hokkaido University Museum and Anthony R. Fiorillo of Southern Methodist University described a new therizinosaurid species from Japan. They also re-evaluated the function of the Therizinosaurus claws. The findings of scientists published in the journal Scientific Reports.

Claws and life reconstruction of Paralitherizinosaurus japonicus. Credit: Genya Masukawa

The fossil described in this work consists ofof a partial vertebra and part of the wrist and forefoot, originally collected in 2008 from the Osushinai Formation, Hokkaido. The remains were thought to be those of a Therizinosaurus. However, the lack of comparative data at the time made confirmation impossible.

With database update and technology developmentscientists conducted a comparative analysis of the claws of therizinosaurs, including data on a new species. It turned out that in advanced therizinosaurs, including P. japonicus, the flexor tubercle of the ungual phalanx, which serves as the site of attachment for the tendon of the deep flexor of the fingers, was smaller than in primitive ones. This confirms previous results: the claws of advanced therizinosaurs were less functional, that is, for example, they were not suitable for digging, but they were quite suitable for pulling tree branches to their mouths. Previously, scientists found that therizinosaurs were herbivores - this is indicated by small lanceolate teeth and a large intestine.

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