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New therizinosaurid dinosaur from the marine Osoushinai Formation (Upper Cretaceous, Japan) provides insight for function and evolution of therizinosaur claws

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Title: New therizinosaurid dinosaur from the marine Osoushinai Formation (Upper Cretaceous, Japan) provides insight for function and evolution of therizinosaur claws
Authors: Kobayashi, Yoshitsugu Browse this author →KAKEN DB
Takasaki, Ryuji Browse this author
Fiorillo, Anthony R. Browse this author
Chinzorig, Tsogtbaatar Browse this author
Hikida, Yoshinori Browse this author
Issue Date: 3-May-2022
Publisher: Nature Portfolio
Journal Title: Scientific reports
Volume: 12
Start Page: 7207
Publisher DOI: 10.1038/s41598-022-11063-5
Abstract: The record of therizinosaurs is rich in Asian countries such as Mongolia and China. Fragmentary therizinosaur specimens have been reported from the Lower and Upper Cretaceous deposits in Japan. One of these specimens, from the lower Campanian Osoushinai Formation in Nakagawa Town of Hokkaido Prefecture, was previously identified as a maniraptoran theropod dinosaur, possibly therizinosaur, but its taxonomic status remained unresolved. This study re-examines the specimen and provides a more detailed description and attempts to resolve its taxonomic status. Our study demonstrates that it is a new taxon, Paralitherizinosaurus japonicus gen. et sp. nov., because it shows a unique combination of characters in the metacarpal I and unguals. Our phylogenetic analysis places this new taxon within an unresolved clade of Therizinosauridae in the strict consensus tree. The 50% majority-rule consensus tree shows better resolution within Therizinosauridae, showing an unresolved monophyletic clade of Paralitherizinosaurus, Therizinosaurus, Suzhousaurus, and the Bissekty form. Geometric morphometric analysis suggests that Paralitherizinosaurus unguals most closely resemble Therizinosaurus unguals in being slender and has weak flexor tubercles. This study also shows an evolutionary trend in ungual shape, which associates a decrease in mechanical advantage, development of flexor tubercle, and hypothesized output (product of mechanical advantage and development of flexor tubercle) in derived therizinosaurs, supporting the hook-and-pull function of claws to bring vegetation to its mouth. Paralitherizinosaurus is the youngest therizinosaur from Japan and the first recovered from the marine deposits in Asia. This suggests a long temporal existence of therizinosaurs at the eastern edge of the Asian continent and adaptation of therizinosaurs to coastal environments.
Type: article
Appears in Collections:総合博物館 (The Hokkaido University Museum) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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