化石
Online ISSN : 2424-2632
Print ISSN : 0022-9202
ISSN-L : 0022-9202
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選択された号の論文の9件中1~9を表示しています
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日本古生物学会の一般社団法人への移行について
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  • 河村 愛, 河村 善也
    2025 年 117 巻 p. 5-18
    発行日: 2025/03/31
    公開日: 2025/03/31
    ジャーナル フリー
    The genus Ailuropoda includes the extant giant panda (A. melanoleuca) which is now restricted to small areas of high mountains in South China, and inhabits mainly bamboo forests there. This paper reviews chronospatial distributions of the genus in East Asia during the Quaternary on the basis of published data including recent ones. The genus comprises two species such as A. microta of the early Early Pleistocene and A. melanoleuca of the middle Early Pleistocene onward. The latter species includes two fossil subspecies such as A. m. wulingshanensis and A. m. baconi (= A. m. fovealis). We have made distribution maps of the genus in East Asia for the Early, Middle, and Late Pleistocene as well as for the Holocene, which indicate its chronospatial distribution. The maps show that the localities are almost restricted to the land area of South China and their distributions are much wider in all the periods of the Quaternary than the present-day distribution of A. melanoleuca. However, the localities are absent from the land areas of East Asia other than South China except those just north of the Qinling Mountains as well as from the prsent-day sea areas of East Asia where mammal fossils have obtained from some places on the seabed. In the Pleistocene fossil localities mapped, the genus is mostly associated with the extinct proboscideans (Stegodon, especially S. orientalis in the Middle and Late Pleistocene localities). S. orientalis has also occurred in the Middle Pleistocene of Honshu-Shikoku-Kyushu in mainland Japan. This fact indicates that S. orientalis immigrated from South China to Honshu-Shikoku-Kyushu in the Middle Pleistocene through a land bridge formed between them, but no fossil records of Ailuropoda are known from Honshu-Shikoku-Kyushu. It is inferred that continuous bamboo forests from South China were not formed on the land bridge, and Ailuroloda could not immigrate into Honshu-Shikoku-Kyushu.
論説
  • 吹本 樹, 近藤 康生, 中尾 賢一
    2025 年 117 巻 p. 19-31
    発行日: 2025/03/31
    公開日: 2025/03/31
    ジャーナル フリー
    Seasonal shell microgrowth history of a left valve of the bivalve, Mizuhopecten tokyoensis hokurikuensis from the Pleistocene under the Naruto Strait was analyzed by oxygen isotope analysis and by measuring the distance between adjoining lamellae. The oxygen isotope profile showed two high water temperature periods and two low water temperature periods, indicating that two years of seasonal variations in water temperature were recorded in this specimen. The profile shows an annual variation of 3.77‰ corresponding to 16.0℃ in water temperature, suggesting that the fossil locality under Naruto Strait was an inner bay like the Harimanada Sea at the time when the analyzed specimen inhabited the area. This suggestion is consistent with the fact that the fossil association with M. tokyoensis hokurikuensis includes inner bay and bay mouth bivalves, such as Ostrea denselamelosa, Fulvia mutica, Anadara broughtonii, and others. The results of the analysis showed that the distance between adjoining lamellae increased during the low water temperature period. Based on the result that annual rings were formed when water temperature was highest (mid-September), we estimated that the lamella formation started around mid-April to mid-June by counting the lamellae up to the first annual ring.
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