EARLY EVOLUTION OF PRIMITIVE ANGIOSPERMS IN CRETACEOUS

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A preliminary description is provided of a new assemblage of plant fossils(the Kamikitaba mesofossil flora) from the Asamigawa Member of the Ashizawa Formation(lower Coniacian, Upper Cretaceous) exposed in Kamikitaba, Fukushima Prefecture, northeastern Honshu, Japan. The fossils are small, three-dimensional and charcoalified or lignitized(mesofossils) and yield exquisite structural details when studied with scanning electron microscopy. The Kamikitaba assemblage comprises the first record of this style of fossil plant preservation from the Cretaceous of eastern Asia. The flora complements and extends current knowledge of Cretaceous fossil plants from Japan and provides a basis for comparison with similar mesofossil assemblages from eastern North America and Europe. The fossil assemblage contains well-preserved angiosperm flowers, fruits, seeds, leaf fragments and wood, as well as shoots, leaves, pollen cones, cone scales and seeds of conifers. Extant taxa that can be recognized provisionally include : Lauraceae, Hamamelidaceae, Fagaceae, Cornales, Combretaceae, and probably Ericales, Magnoliaceae, Nymphaeales and Taxodiaceae. Leaf and rachis fragments of ferns, sporangia with in situ spores, and megaspores also document the presence of Selaginellaceae and Schizaeaceae.