Friis Else Marie, Pedersen Kaj Raunsgaard, Crane Peter R
Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden
Department of Geoscience, University of Aarhus, Aarhus, Denmark.
Proc Biol Sci. 2016 Dec 28;283(1845). doi: 10.1098/rspb.2016.1325.
Eudicots, the most diverse of the three major clades of living angiosperms, are first recognized in the latest Barremian-earliest Aptian. All Early Cretaceous forms appear to be related to species-poor lineages that diverged before the rise of core eudicots, which today comprise more than 70% of angiosperm species. Here, we report the discovery of a well-preserved flower, Caliciflora mauldinensis, from the earliest Late Cretaceous, with unequivocal core eudicot features, including five sepals, five petals and two whorls of stamens borne on the rim of a floral cup containing three free carpels. Pollen is tricolporate. Carpels mature into follicular fruitlets. This character combination suggests a phylogenetic position among rosids, but more specific assignment is precluded by complex patterns of character evolution among the very large number of potentially relevant extant taxa. The whorled floral organization is consistent with ideas that this stable pattern evolved early and was a prerequisite for more integrated patterns of floral architecture that evolved later. However, limited floral synorganization in Caliciflora and all earlier eudicot flowers recognized so far, calls into question hypotheses that substantial diversification of core eudicots had already occurred by the end of the Early Cretaceous.
真双子叶植物是现存被子植物三大主要分支中种类最多的，最早在晚巴列姆阶-早阿普第阶被识别出来。所有早白垩世的类群似乎都与在核心真双子叶植物兴起之前就已分化的物种较少的谱系有关，而如今核心真双子叶植物占被子植物物种的70%以上。在此，我们报告了一种保存完好的花——莫尔丁卡利花（Caliciflora mauldinensis）的发现，它来自晚白垩世最早期，具有明确的核心真双子叶植物特征，包括五片萼片、五片花瓣以及着生于包含三个离生心皮的花杯边缘的两轮雄蕊。花粉具三沟孔。心皮发育成蓇葖果小果。这种特征组合表明其在蔷薇类中的系统发育位置，但由于大量潜在相关现存类群中复杂的性状演化模式，无法进行更具体的分类。轮状花部结构与这样的观点一致，即这种稳定模式很早就已演化出来，并且是后来演化出的更整合的花部结构模式的前提条件。然而，卡利花以及目前为止所识别出的所有更早的真双子叶植物花中有限的花部协同组织，对早白垩世末期核心真双子叶植物已经发生大量多样化的假说提出了质疑。
