目的:新生代麦格理港组(MHF)是澳大利亚最古老,最南端的后白垩纪植物化石组合之一。恰逢始新世早期气候最佳(EECO),并早于澳大利亚从南极洲分裂,它提供了关键数据来研究南极森林生物群落的多样性和范围,以及冈瓦纳分手导致的澳大利亚和南美之间的植物区系差异。
方法:描述并系统分析了来自MHF的新化石植物压缩的微观形态和宏观形态。对以前出版的非开花植物记录进行了审查和修订。提供了大化石丰度数据。将植物区系与南半球其他早期古近纪组合进行了比较。
结果:从大化石记录中鉴定出12种非开花植物。针叶树包括南洋菜科(南洋菜,A.readiae,A.timkarikensissp.11月。,和线性南洋菜),罗汉科(Acmopyleglabra,mucronatus,副罗汉松。11月。,和后叶。),和柏树科(Libocedrusmicroformis)。Dacryparpuslinifolius被指定为D.mucronatus的初级同义词。其他组件包括苏铁(Boweniajohnsonii,Zamiaceae),蕨类植物(Comlopteriscenozoicus,Umkomasiaceae),和一种蕨类植物(金麦草,五子花科)。
结论:化石组合代表了一个混合的近极地森林,针叶树具有高度多样性。几种物种的形态和保存表明对高纬度生活的适应。大叶和小叶针叶树的共存意味着复杂的,可能是开放的森林结构。与阿根廷同期组合的比较支持EECO期间的环极生物群落,从澳大利亚南部穿过南极洲到达南美洲南部。
OBJECTIVE: The Cenozoic Macquarie Harbour Formation (MHF) hosts one of the oldest and southernmost post-Cretaceous
fossil plant assemblages in Australia. Coinciding with the Early Eocene Climatic Optimum (EECO) and predating the breakup of Australia from Antarctica, it offers critical data to study the diversity and extent of the Austral Polar Forest Biome, and the floristic divergence between Australasia and South America resulting from the Gondwana breakup.
METHODS: The micromorphology and macromorphology of new
fossil plant compressions from the MHF were described and systematically analyzed. Previously published non-flowering plant records were reviewed and revised. Macrofossil abundance data were provided. The flora was compared with other early Paleogene assemblages from across the Southern Hemisphere.
RESULTS: Twelve species of non-flowering plants were identified from the macrofossil record. Conifers include Araucariaceae (Araucaria macrophylla, A. readiae, A. timkarikensis sp. nov., and Araucarioides linearis), Podocarpaceae (Acmopyle glabra, Dacrycarpus mucronatus, Podocarpus paralungatikensis sp. nov., and Retrophyllum sp.), and Cupressaceae (Libocedrus microformis). Dacrycarpus linifolius was designated a junior synonym of D. mucronatus. Further components include a cycad (Bowenia johnsonii, Zamiaceae), a pteridosperm (Komlopteris cenozoicus, Umkomasiaceae), and a fern (Lygodium dinmorphyllum, Schizaeaceae).
CONCLUSIONS: The
fossil assemblage represents a mixed near-polar forest with a high diversity of conifers. The morphology and preservation of several species indicate adaptations to life at high latitudes. The coexistence of large- and small-leaved conifers implies complex, possibly open forest structures. Comparisons with contemporaneous assemblages from Argentina support a circumpolar biome during the EECO, reaching from southern Australia across Antarctica to southern South America.