Mammalian faunal transition with the early diversification of eutherians in the Early Cretaceous Asia

• Project/Area Number: 16K17830
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Stratigraphy/Paleontology
• Research Institution: Ehime University
• Principal Investigator: Kusuhashi Nao 愛媛大学, 理工学研究科(理学系), 准教授 (70567479)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000); Fiscal Year 2019: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2018: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2017: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000); Fiscal Year 2016: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
• Keywords: 哺乳類 / 進化 / 中生代 / 白亜紀 / アジア / 多様性 / 東アジア / 真獣類 / 多丘歯類 / 真三錐歯類 / 多様化 / 層位・古生物学 / 古脊椎動物学 / 中生代哺乳類

Outline of Final Research Achievements

The project was intended to investigate mammalian faunal transition in Asia during the late Early Cretaceous, when an early diversification of eutherians occurred, I conducted fossil excavations in Fuxin area, Liaoning Province, northeastern China and taxonomic study on mammalian fossils from the Shahai and Fuxin formations.
Based on taxonomic study on newly discovered specimens as well as previously collected specimens, papers describing new species and specimens of eutriconodontans and multituberculates were published. I also published a paper of reexamination of previously described eutherian species. The full picture of the fossil assemblages from the Shahai and Fuxin formations is becoming clearer, and it gradually revealing the mammalian faunal transition in Asia during the late Early Cretaceous.

Academic Significance and Societal Importance of the Research Achievements

真獣類は現生哺乳類種数の90%以上を占めるグループで，中生代の中期ジュラ紀 (あるいは遅くとも前期白亜紀の中頃まで) に出現後，前期白亜紀の後半には初期の多様化を始めたらしいことが化石記録でわかってきた．真獣類の初期進化の中心であったと考えられるアジアにおいて，真獣類の多様化に伴い哺乳類相の構成がどのように変化したのかを知ることは，哺乳類の進化史を探るうえで重要なテーマである．現在その時代の様子を知ることができる化石群の調査を進めており，徐々に当時のアジアの哺乳類相変遷が明らかになりつつある．

Research Products

• [Int'l Joint Research] 中国科学院古脊椎動物與古人類研究所(中国)
• [Journal Article] New gobiconodontid (Eutriconodonta, Mammalia) from the Lower Cretaceous Shahai and Fuxin formations, Liaoning, China (2020)
  • Author(s): Kusuhashi, N., Wang, Y.-Q., Li, C.-K., and Jin, X.
  • Journal Title: Vertebrata PalAsiatica Volume: 58 Pages: 45-66
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] A new eobaatarid multituberculate (Mammalia) from the Lower Cretaceous Fuxin Formation, Fuxin-Jinzhou basin, Liaoning, northeastern China (2019)
  • Author(s): Kusuhashi, N., Wang, Y.-Q., and Jin, X.
  • Journal Title: Journal of Mammalian Evolution Volume: － Issue: 4 Pages: 605-623
  • DOI: 10.1007/s10914-019-09481-w
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Reappraisal of Endotherium niinomii Shikama, 1947, a eutherian mammal from the Lower Cretaceous Fuxin Formation, Fuxin-Jinzhou Basin, Liaoning, China (2018)
  • Author(s): Wang, Y.-Q., Kusuhashi, N., Jin, X., Li, C.-K., Setoguchi, T., Gao, C.-L., and Liu, J.-Y.
  • Journal Title: Vertebrata PalAsiatica Volume: 56 Pages: 180-192
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Reinvestigation of an Early Cretaceous eutherian mammal Endotherium niinomii (2016)
  • Author(s): Kusuhashi, N., Wang, Y.-Q., and Li, C.-K.
  • Organizer: 4th International Symposium of the IGCP 608, Cretaceous Ecosystems and Their Responses to Paleoenvironmental Changes in Asia and the Western Pacific
  • Place of Presentation: Novosibirsk, Russia
  • Year and Date: 2016-08-15
  • Int'l Joint Research