Two early eudicot fossil flowers from the Kamikitaba assemblage (Coniacian, Late Cretaceous) in northeastern Japan
Two early eudicot fossil flowers from the Kamikitaba assemblage (Coniacian, Late Cretaceous) in northeastern Japan
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DOI：
10.1007/s10265-017-0945-1
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发表时间：
2017-05
影响因子：
2.8
通讯作者：
Masamichi Takahashi;P. Herendeen;Xianghui Xiao
中科院分区：
文献类型：
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作者：
Masamichi Takahashi;P. Herendeen;Xianghui Xiao
在日本双叶群的Kamikitaba地区（约89 MYBP，早Coniacian：晚白垩世）发现了两个新的可参考基岩级的化石分类群。这些经鉴定的中化石显示出保存完好的三维结构，并使用同步辐射x射线微断层扫描分析了它们的组成和内部结构。Cathiaria japonicasp。11月的果序由轴组成，轴上有三到四个果实。蒴果无梗，开裂，由一苞片包围的雌蕊组成。没有花被部分存在。雌蕊具单心皮，含有两个下垂的种子。心皮在下半部分和在上半部分重叠，花柱背面偏转具一大的，斜延的柱头。花粉粒为三棱形，具网状外壁。cathiaria的形态特征与归为熊科一致。（包括Didymelaceae）。Archaestella verticillatusgen。11月的花小，辐射对称，有花梗，两性，半下位，多心皮。花托是杯状的，周围的花被由几个花被片围绕边缘插入。雌蕊由十个对生的轮生组成，侧面合生，但上部不同的心皮具有明显的背凸，包括一个中心腔。花柱短，变成下弯具一腹下延柱头。种子每心皮约10，边缘，从室的宽，斜顶下垂。花粉粒为三棱形，外壁呈网状，与雌蕊有关。古星属植物的形态特征表明其可能与龙柏属植物基级的龙柏科有亲缘关系。该化石目前提供了该科的最早记录，并证明了晚白垩纪中期在欧亚大陆东部出现了Trochodendraceae。
Two new fossil taxa referable to the basal eudicot grade are described from the Kamikitaba locality (ca. 89 MYBP, early Coniacian: Late Cretaceous) of the Futaba Group in Japan. These charcoalified mesofossils exhibit well-preserved three-dimensional structure and were analyzed using synchrotron-radiation X-ray microtomography to document their composition and internal structure.Cathiaria japonicasp. nov. is represented by infructescence segments that consist of an axis bearing three to four fruits. The capsular fruits are sessile and dehiscent and consist of a gynoecium subtended by a bract. No perianth parts are present. The gynoecium is monocarpellate containing two pendulous seeds. The carpel is ascidiate in the lower half and conduplicate in the upper part, and the style is deflected abaxially with a large, obliquely decurrent stigma. Pollen grains are tricolpate with a reticulate exine. The morphological features ofCathiariaare consistent with an assignment to the Buxaceaes. l. (including Didymelaceae).Archaestella verticillatusgen. et sp. nov. is represented by flowers that are small, actinomorphic, pedicellate, bisexual, semi-inferior, and multicarpellate. The floral receptacle is cup shaped with a perigynous perianth consisting of several tepals inserted around the rim. The gynoecium consists of a whorl of ten conduplicate, laterally connate but distally distinct carpels with a conspicuous dorsal bulge, including a central cavity. The styles are short, becoming recurved with a ventrally decurrent stigma. Seeds are ca. 10 per carpel, marginal, pendulous from the broad, oblique summit of the locule. Pollen grains are tricolpate with a reticulate exine pattern, suggesting a relationship to eudicots. The morphological features ofArchaestellaindicate a possible relationship to Trochodendraceae in the basal grade of eudicots. The fossil currently provides the earliest record of the family and documents the presence of Trochodendraceae in eastern Eurasia during the middle part of the Late Cretaceous.