背景:菊科包括四个现存属(Hedyosmum,蛔虫,ChloranthusandSarcandra),都是简单的花朵。分子系统发育学表明,在被子植物进化过程中,菊科非常早期地分化,尽管它们与eudicots有什么关系,木兰,单子叶植物和角藻是不确定的。在白垩纪早期,人们早已认识到类似于A虫和Hedosmum的化石花粉,但是在过去的四十年中,基于其他类型化石的已灭绝的五竹科的证据急剧扩大,并为理解该科的进化做出了重要贡献。
方法:研究白垩纪化石,特别是来自葡萄牙和北美东部的早白垩纪中质化石,认识到各种各样的花朵,水果,种子,雄蕊花序和雄蕊灭绝的花序。这些早期的绿药包括与现存的Hedyosmum和Ascarina相关的形式,Chloranthus和Sarcandra进化枝。在白垩纪晚期,发生了几次与现存的Chloranthus有关的独特的雄性化石。金钱草科丰富而仍在扩展的白垩纪记录与非常稀疏的新生代记录形成对比,强调现存的四个属可能是相对性的,尽管该属内的物种形成可能发生在相对较近的时间。在这项研究中,我们描述了早白垩纪的三个新属,并总结了有关该群体灭绝多样性的最新知识。
结论:包括现存的Chlothanteae在内的进化谱系是多样化的,并且在早白垩纪中化石植物区系中大量存在,这些植物区系提供了被子植物生殖结构的一些最早证据。已灭绝的绿药,其中一些很明显属于菊科树冠组,填补了一些目前分离现有属的形态学空白,有助于阐明现存的金钱草科的一些不寻常特征是如何进化的,并表明金钱草科对于更精细地了解早期被子植物多样化的生态学和系统发育具有不成比例的重要性。
BACKGROUND: The Chloranthaceae comprise four extant genera (Hedyosmum, Ascarina, Chloranthus and Sarcandra), all with simple flowers. Molecular phylogenetics indicates that the Chloranthaceae diverged very early in angiosperm evolution, although how they are related to eudicots, magnoliids, monocots and Ceratophyllum is uncertain. Fossil pollen similar to that of Ascarina and Hedyosmum has long been recognized in the Early Cretaceous, but over the last four decades evidence of extinct Chloranthaceae based on other types of fossils has expanded dramatically and contributes significantly to understanding the evolution of the family.
METHODS: Studies of fossils from the Cretaceous, especially mesofossils of Early Cretaceous age from Portugal and eastern North America, recognized diverse flowers, fruits, seeds, staminate inflorescences and stamens of extinct chloranthoids. These early chloranthoids include forms related to extant Hedyosmum and also to the Ascarina, Chloranthus and Sarcandra clade. In the Late Cretaceous there are several occurrences of distinctive fossil androecia related to extant Chloranthus. The rich and still expanding Cretaceous record of Chloranthaceae contrasts with a very sparse Cenozoic record, emphasizing that the four extant genera are likely to be relictual, although speciation within the genera might have occurred in relatively recent times. In this study, we describe three new genera of Early Cretaceous chloranthoids and summarize current knowledge on the extinct diversity of the group.
CONCLUSIONS: The evolutionary lineage that includes extant Chloranthaceae is diverse and abundantly represented in Early Cretaceous mesofossil floras that provide some of the earliest evidence of angiosperm reproductive structures. Extinct chloranthoids, some of which are clearly in the Chloranthaceae crown group, fill some of the morphological gaps that currently separate the extant genera, help to illuminate how some of the unusual features of extant Chloranthaceae evolved and suggest that Chloranthaceae are of disproportionate importance for a more refined understanding of ecology and phylogeny of early angiosperm diversification.