L. H. Bailey Hortorium, Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA.
Am J Bot. 2012 Aug;99(8):1356-74. doi: 10.3732/ajb.1200025. Epub 2012 Aug 1.
Herein, we name, describe, and illustrate new macrofossil material representing Eucalyptus (Myrtaceae: Myrtoideae, Eucalypteae) from the diverse early Eocene Laguna del Hunco (LH) flora of Chubut Province, Patagonia, Argentina. We explore the significance of these fossils in light of understanding the fossil record of eucalypts and the biogeography of the Eucalypteae.
Fossils representing vegetative and reproductive organs were collected from multiple LH localities over several field seasons. These specimens were prepared, photographed, and compared to extant Eucalyptus. Additional historical collections of Patagonian fossil Eucalyptus were also examined.
Vegetative and reproductive organs representing five different Eucalyptus taxa were identified in the LH paleoflora. One new taxon each representing leaves, flower buds, and infructescences with co-occurring, isolated capsules are described and named as new Eucalyptus species. Additionally, two flower types cf. Eucalyptus, represented by one specimen each, are illustrated and briefly described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus, although it also shares many similarities to the closely related genus Corymbia.
The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be definitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.
本文命名、描述并图示了产自阿根廷巴塔哥尼亚丘布特省多样化早始新世拉古纳德尔洪科（LH）植物群中新的大型叶化石材料，代表了桃金娘科（桃金娘目：桃金娘亚目、桉族）的桉树。我们根据桉树化石记录和桉族生物地理学来探讨这些化石的意义。
在多个 LH 地点，通过多个野外考察季节采集了代表营养器官和繁殖器官的化石。对这些标本进行了准备、拍摄，并与现存的桉树进行了比较。还对巴塔哥尼亚古化石桉树的其他历史标本进行了检查。
在 LH 古植物群中鉴定出代表五个不同桉树类群的营养器官和繁殖器官。描述并命名了五个新的分类群，每个分类群代表一片叶子、花蕾和带有共生、分离蒴果的果实。此外，还图示并简要描述了两个代表桉树的花型，每种各有一个标本。化石物种具有独特的特征，独立表明它们属于桉族。生殖材料在形态上与现存的桉树最为相似，尽管它也与密切相关的 Corymbia 属有许多相似之处。
LH 化石桉树材料是最近被命名和描述的少数桉树大型叶化石之一，也是目前可明确归入桉族的最古老的大型叶化石。它们也是唯一可信的描述发生在澳大利亚以外的桉树化石，并表明该类群曾经有更广泛的地理分布。
