BACKGROUND AND AIMS Cunoniaceae are woody plants with a distribution that suggests a complex history of Gondwanan vicariance, long-distance dispersal, diversification, and extinction. Only four out of c. 27 genera in Cunoniaceae are native to South America today, but the discovery of extinct species from Argentine Patagonia is providing new information about the history of this family in South America. METHODS We describe fossil flowers collected from early Danian (early Palaeocene, ~64 Mya) deposits of the Salamanca Formation. We compare them with similar flowers from extant and extinct species using published literature and herbarium specimens. We used simultaneous analysis of morphology and available chloroplast DNA sequences (trnL-F, rbcL, matK, trnH-psbA) to determine the probable relationship of these fossils to living Cunoniaceae and the co-occurring fossil species Lacinipetalum spectabilum. KEY RESULTS Cunoniantha bicarpellata gen. et sp. nov. is the second species of Cunoniaceae to be recognized among the flowers preserved in the Salamanca Formation. Cunoniantha flowers are pentamerous, complete, the anthers contain in-situ pollen, and the gynoecium is bicarpellate and syncarpous with two free styles. Phylogenetic analysis indicates that Cunoniantha belongs to crown-group Cunoniaceae among the core-Cunoniaceae clade; although it does not have obvious affinity with any tribe. Lacinipetalum spectabilum, also from the Salamanca Formation, belongs to the Cunoniaceae crown-group as well, but close to tribe Schizomerieae. CONCLUSIONS Our findings highlight the importance of west Gondwana in the evolution of Cunoniaceae during the early Palaeogene. The co-occurrence of Cunoniantha bicarpellata and Lacinipetalum spectabilum, belonging to different clades within Cunoniaceae, indicates that the diversification of crown-group Cunoniaceae was underway by 64 million years ago.

中文翻译：

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来自南美洲的古新世早期杉木科多样化的化石证据

背景和目的Cunoniaceae 是木本植物，其分布表明冈瓦纳古生物的复杂历史、远距离扩散、多样化和灭绝。c中只有四个。今天，Cunoniaceae 中的 27 个属原产于南美洲，但阿根廷巴塔哥尼亚灭绝物种的发现提供了有关该科在南美洲历史的新信息。方法 我们描述了从 Salamanca 组的早大年（早古新世，~64 Mya）沉积物中收集的化石花。我们使用已发表的文献和植物标本馆标本将它们与现存和灭绝物种的相似花朵进行比较。我们使用了形态学和可用叶绿体 DNA 序列（trnL-F、rbcL、matK、trnH-psbA) 以确定这些化石与现存的鼠尾草科和共同出现的化石物种 Lacinipetalum spectabilum 的可能关系。主要结果 Cunoniantha bicarpelata gen。等 sp. 十一月 是保存在萨拉曼卡组的花中第二个被确认的Cunoniaceae 物种。刺槐花五瓣，完整，花药含有原位花粉，雌蕊群为二心皮和合心体，有两种游离花柱。系统发育分析表明，刺槐属于杉科核心进化枝中的冠群杉科；虽然与任何部落都没有明显的亲缘关系。Lacinipetalum spectabilum 也来自Salamanca 组，也属于Cunoniaceae 冠群，但接近部落Schizomerieae。结论我们的研究结果强调了西冈瓦纳纪在古近纪早期在鼠尾草科进化中的重要性。Cunoniantha bicarpelata 和 Lacinipetalum spectabilum 的共生，属于杉科不同进化枝，表明冠群杉科的多样化在 6400 万年前就开始了。