The non-flowering plants of a near-polar forest in East Gondwana, Tasmania, Australia, during the Early Eocene Climatic Optimum

IF 2.4 2区生物学 Q2 PLANT SCIENCES American Journal of Botany Pub Date : 2024-08-27 DOI:10.1002/ajb2.16398

Miriam A. Slodownik

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Abstract

Premise

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.

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早始新世最佳气候时期澳大利亚塔斯马尼亚州东冈瓦纳近极地森林中的不开花植物。

前提：新生代麦格理港地层（MHF）拥有澳大利亚最古老、最南端的白垩纪后植物化石群。它与早始新世气候最适宜期（EECO）相吻合，并且早于澳大利亚从南极洲分裂出来的时间，为研究澳大利亚极地森林生物群落的多样性和范围，以及冈瓦纳分裂导致的澳大拉西亚和南美洲之间的植物分异提供了重要数据：方法：描述并系统分析了马弗跳森林新压制化石植物的微形态和大形态。对以前发表的非开花植物记录进行了回顾和修订。提供了大化石丰度数据。将该植物群与南半球其他早古新世植物群落进行了比较：结果：从宏化石记录中确定了 12 种非开花植物。针叶树包括Araucariaceae（Araucaria macrophylla、A. readiae、A. timkarikensis sp.Dacrycarpus linifolius 被指定为 D. mucronatus 的初级异名。其他成分还包括苏铁（Bowenia johnsonii，Zamiaceae）、蕨类植物（Komlopteris cenozoicus，Umkomasiaceae）和蕨类植物（Lygodium dinmorphyllum，Schizaeaceae）：化石群代表了一种针叶树种类繁多的近极地混交林。多个物种的形态和保存情况表明它们适应了高纬度地区的生活。大叶针叶树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。与阿根廷同时期生物群落的比较结果表明，EECO时期存在一个从澳大利亚南部穿过南极洲到达南美洲南部的环极生物群落。

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来源期刊

American Journal of Botany 生物-植物科学

CiteScore

4.90

自引率

6.70%

发文量

171

审稿时长

3 months

期刊介绍： The American Journal of Botany (AJB), the flagship journal of the Botanical Society of America (BSA), publishes peer-reviewed, innovative, significant research of interest to a wide audience of plant scientists in all areas of plant biology (structure, function, development, diversity, genetics, evolution, systematics), all levels of organization (molecular to ecosystem), and all plant groups and allied organisms (cyanobacteria, algae, fungi, and lichens). AJB requires authors to frame their research questions and discuss their results in terms of major questions of plant biology. In general, papers that are too narrowly focused, purely descriptive, natural history, broad surveys, or that contain only preliminary data will not be considered.