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Early Evolution of Primitive Angiosperms in Cretaceous

白垩纪原始被子植物的早期演化

基本信息

批准号：
15570076
负责人：
TAKAHASHI Masamichi
金额：
$ 1.79万
依托单位：
Niigata University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

Over the last 20 years, many Cretaceous mesofossil floras have been discovered in Europe, eastern North America and central America. Studies of the mesogossils in these assemblages have yielded dramatic progress in our understanding of pattens of systematic differentiation during the Cretaceous history of angiosperms.In this study, I would like to present a new Cretaceous mesofossil flora from northeastern Asia and the Pacific Rim. The mesofossils were isolated from bulk sediment samples collected from an outocrop of the Futaba Group exposed in Fukushima Prefecture in northeastern Japan. The sediments of the Futaba Group are thought to range in age from early Coniacian to late Santonian, and well dated by marine invertebrate fossils that also occur in some facies of the Futaba Group.The platn-bearing sediments are from the Asamigawa Member, the lowermost within the Futaba Group, and are dated as early Coniacian, about 89 million years before present, based on marine fossils in the over … More lying Obisagawa Member. The sedeiments of the Asamigawa Member are interpreted as an alluvial fan deposit comprising poorly-sorted sand stones and siltstones.The fossil assemblage, which I call "Kamikitaba assemblage" after the name of the sampling site, contains well preserved megaspores, sporangia, conifer shoots, cone scales, and angiosperm flowers, fruits and seeds. Among the ferns, the family Schizeaceae is well represented, and the conifers include a variety of presumed Taxoideae and perhaps other familes.In summary, the Kamikitaba assemblage includes well-preserved fossil flower, fruits and seed of early angiosperms. I concluded from the evidence of mesofossils, that the early Coniacian vegetation in the environments represented by the Kamikitaba assemblage, was probably dominated, in terms of abundance, by both conifers and angiosperms, with angiosperms probably more diverse in terms of species. Extant taxa that can be recognized provisionally include: Lauraceae, Hamamelidaceae, Fagaceae, Cornales, Combretaceae, and probably Ercales, Magnoliaceae and Nymphaeales. Less

在过去的20年里，在欧洲、北美东部和中美洲发现了许多白垩纪的中化石区系。对这些组合中的中胚层的研究使我们对白垩纪被子植物的系统分化模式的理解取得了重大进展。在这项研究中，我想介绍一种来自东北亚和环太平洋地区的新的白垩纪中化石植物群。这些中化石是从日本东北部福岛县暴露的双叶群露头的大块沉积物样本中分离出来的。双叶群沉积物的年代被认为从早Coniacian到晚sanantonian，并且在双叶群的一些相中也发现了海洋无脊椎动物化石。含台地的沉积物来自双叶群中最底层的浅川组，根据多卧的浅川组的海洋化石，其年代为早Coniacian，距今约8900万年。浅川段的沉积被解释为一个由差分选的砂岩和粉砂岩组成的冲积扇沉积。根据采样地点的名称，我将这个化石组合称为“Kamikitaba组合”，它包含保存完好的大孢子、孢子囊、针叶树芽、球果鳞片和被子植物的花、果实和种子。在蕨类植物中，裂科是很有代表性的，针叶树包括各种假定的杉科和其他科。综上所述，Kamikitaba组合包括保存完好的早期被子植物的花、果实和种子化石。我从中化石的证据中得出结论，在以Kamikitaba组合为代表的环境中，早期的Coniacian植被可能以针叶树和被子植物的丰度为主导，被子植物的种类可能更多样化。目前可以识别的分类群包括：樟科、金缕梅科、壳斗科、山茱萸科、combretacae科，可能还包括枫香科、木兰科和睡莲科。少