Early Evolution of Primitive Angiosperms in Cretaceous

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中层化石植物群。对这些组合中的中生化石的研究在了解被子植物在白垩纪历史上的系统分化模式方面取得了巨大的进展。在这项研究中，我想介绍一个来自东北亚和太平洋沿岸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出露的Futaba群露头采集的大量沉积物样本中分离出来的。双叶群的沉积物被认为是从哥尼亚纪早期到桑托纪晚期的沉积，并通过海洋无脊椎动物化石确定了很好的年代，这些化石也出现在双叶群的一些相中。含铂的沉积物来自双叶群中最低的浅川段，根据Over…中的海洋化石，测得科尼亚期早，大约比现在早百万年更多撒谎的Obisagawa成员。Asamigawa段的沉积被解释为由分选不良的砂岩和粉砂岩组成的冲积扇沉积。化石组合--我以采样点的名字命名为“神木高田组合”--包含保存完好的大孢子、孢子囊、针叶树枝、球果鳞片和被子植物花、果和种子。在蕨类植物中，裂叶蕨科的代表性较好，针叶植物包括各种推测的杉科植物，也可能包括其他科。综上所述，神木高叶植物组合包括保存完好的早期被子植物的化石花、果实和种子。根据中化石的证据，我得出的结论是，以神木塔巴组合为代表的环境中的早期科尼亚期植被，在丰度方面可能由针叶植物和被子植物主导，被子植物在物种方面可能更加多样化。现有的可暂时识别的分类群包括：樟科、金缕梅科、壳斗科、山茱蒲科、菊科，可能还有木兰科、木兰科和睡莲科。较少

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