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Age determination of the oldest ichthyosauriform fossils

Research Project

Project/Area Number 19K04062
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeMulti-year Fund
Section一般
Review Section Basic Section 17050:Biogeosciences-related
Research InstitutionNational Museum of Nature and Science, Tokyo

Principal Investigator

Shigeta Yasunari  独立行政法人国立科学博物館, 地学研究部, グループ長 (30270408)

Project Period (FY) 2019-04-01 – 2022-03-31
Project Status Completed (Fiscal Year 2021)
Budget Amount *help
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2021: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2020: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Keywords三畳紀 / 魚竜 / 産出年代 / スパシアン期 / タイサウルス / ウタツサウルス / プリモーリエ / Spathian / 最古 / 魚竜類 / 年代 / 化石層序
Outline of Research at the Start

魚竜類は、三畳紀に出現してジュラ紀に大繁栄し、白亜紀のなかばに絶滅した海棲爬虫類である。高度に水棲適応した種を含み、収斂進化の典型例として知られている。三畳紀前期に陸棲爬虫類のいずれかが水棲に適応したと考えられており、最古級の化石は中国、日本、ロシア、タイなどの三畳紀前期のスパシアン期の地層から見つかっている。しかし、これら産出年代の詳細については必ずしも十分に明らかにされていない。本研究では、ロシア極東地域、三陸海岸地域、タイ南部地域のスパシアン期アンモナイトの高精度年代層序の確立により、魚竜類の産出年代を特定し、水棲適応の過程を明らかにする上で重要な年代データを提供する。

Outline of Final Research Achievements

The geological survey of the Lower Triassic in the Phatthalung area, southern Thailand and the Sanriku coast in Miyagi Prefecture reveals the following things: 1) the age of Thaisaurus is the early Spathian, suggesting it is one of the oldest known ichthyopterygians, 2) the age of Utatsusaurus is the middle Spathian. Studies of ichthyopterygian bones collected from South Primorye, Russian Far East show that 1) the age is the early Spathian, 2) it was highly aquatic adapted based on histological studies of the bones, 3) it represents one of the largest of early Spathian marine reptiles known to date. This study reveals that ichthyopterygians were highly aquatic adapted and diversified in the short period of the early Spathian.

Academic Significance and Societal Importance of the Research Achievements

本研究は、これまであまり注目されてこなかったタイ南部や極東ロシアの魚竜化石が最古級(前期スパシアン期)であり、特にロシア産魚竜の骨組織は高度な水棲適応を示し、また他の海生爬虫類に比べ体サイズが著しく大きいこと、などを明らかにした。これらの成果は、海生爬虫類の進化や水棲適応の過程を明らかにする上で重要なデータを提供するものである。また、本研究は、日本をはじめとするアジア諸国を発信源として海生爬虫類の初期進化という世界的に注目度の高い研究テーマをさらに展開するきっかけになると期待される。

Report

(4 results)
  • 2021 Annual Research Report   Final Research Report ( PDF )
  • 2020 Research-status Report
  • 2019 Research-status Report
  • Research Products

    (5 results)

All 2022 2020 Other

All Int'l Joint Research (1 results) Journal Article (4 results) (of which Int'l Joint Research: 3 results,  Peer Reviewed: 4 results,  Open Access: 1 results)

  • [Int'l Joint Research] Department of Mineral Resources(タイ)

    • Related Report
      2020 Research-status Report
  • [Journal Article] Early Triassic ichthyopterygian fossils from the Russian Far East2022

    • Author(s)
      Nakajima, Y., Shigeta, Y., Houssaye, A., Zakharov, Y. D., Popov, A. M., Sander, P. M.
    • Journal Title

      Scientific Reports

      Volume: 12 (5546) Issue: 1 Pages: 1-15

    • DOI

      10.1038/s41598-022-09481-6

    • Related Report
      2021 Annual Research Report
    • Peer Reviewed / Open Access / Int'l Joint Research
  • [Journal Article] Revision of early Spathian (late Olenekian, Early Triassic) ammonoids from the Osawa Formation at Akaushi in the Motoyoshi area, South Kitakami Belt, Northeast Japan2022

    • Author(s)
      Shigeta, Y.
    • Journal Title

      Paleontological Research

      Volume: -

    • Related Report
      2021 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Age of the Early Triassic ichthyopterygian Thaisaurus inferred from ammonoid biostratigraphy2020

    • Author(s)
      Tongtherm, K., Shigeta, Y., Sardsud, A., Sashida, K., Agematsu, S.
    • Journal Title

      Paleontological Research

      Volume: 24 Issue: 4 Pages: 276-284

    • DOI

      10.2517/2019pr022

    • NAID

      210000158547

    • Related Report
      2020 Research-status Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Discovery of the early Spathian (Early Triassic) ammonoid Marcouxia chaiburiensis at Khao Chingcho, Phatthalung Province, southern Thailand2020

    • Author(s)
      Tongtherm, K., Shigeta, Y., Sardsud, A., Sashida, K., Agematsu, S.
    • Journal Title

      Bulletin of the National Museum of Nature and Science, Series C

      Volume: 46 Pages: 61-66

    • Related Report
      2020 Research-status Report
    • Peer Reviewed / Int'l Joint Research

URL: 

Published: 2019-04-18   Modified: 2023-01-30  

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