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1 August 2022 Revision of Early Spathian (Late Olenekian, Early Triassic) Ammonoids from the Osawa Formation at Akaushi in the Motoyoshi Area, South Kitakami Belt, Northeast Japan
Yasunari Shigeta
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Abstract

A taxonomic revision of the ammonoid assemblage previously reported from the Osawa Formation at Akaushi in the Motoyoshi area, i.e., Columbites parisianus, Subcolumbites perrinismithi and Eophyllites cf. dieneri, leads to the conclusion that the fauna should be attributed to Hellenites tchernyschewiensis, H. inopinatus, Neocolumbites grammi, N. insignis, Procolumbites ussuriensis and P. subquadratus. In addition, this fauna also includes Deweveria kovalenkoi. Because these ammonoids are characteristic of the N. insignis Zone of South Primorye, Russian Far East, the lowest part of the Osawa Formation clearly correlates with the upper part of the lower Spathian (upper Olenekian, Lower Triassic), and the faunal similarity suggests that the South Kitakami Belt may have been located near South Primorye on the western side of the Panthalassa.

© by the Palaeontological Society of Japan
Yasunari Shigeta "Revision of Early Spathian (Late Olenekian, Early Triassic) Ammonoids from the Osawa Formation at Akaushi in the Motoyoshi Area, South Kitakami Belt, Northeast Japan," Paleontological Research 26(4), 405-419, (1 August 2022). https://doi.org/10.2517/PR210003
Received: 22 January 2021; Accepted: 27 May 2021; Published: 1 August 2022
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KEYWORDS
ammonoid
Osawa Formation
South Kitakami Belt
Spathian
Triassic
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