Abstract As part of the most common eukaryotic fossils in early Ediacaran strata, acanthomorphic acritarchs are crucial for understanding the biostratigraphy and evolutionary dynamics of marine eukaryotes after the Marinoan global glaciation. Abundant and diverse acanthomorphic acritarchs have been reported from the Ediacaran Doushantuo Formation in the Yangtze Gorges area, South China, and different biozonation schemes have been proposed. However, these previously published biozones were based on biostratigraphic data compiled from different stratigraphic sections, with little effort to test whether these biozones can be consistently recognized at different sections, despite the fact that regional consistency is critical to a robust biostratigraphic framework. Also, the evolutionary pattern of the Doushantuo acritarchs has not been documented in detail, especially for acritarchs from the lowermost Doushantuo Formation, largely due to the perceived low taxonomic richness after the Marinoan global glaciation. In this study, we report silicified acanthomorphic acritarchs and other eukaryotic microfossils from chert nodules in the lower part (Member II) of the Doushantuo Formation at the Jiulongwan, Jinguadun, and Wuzhishan sections in the Yangtze Gorges area. From a total of 1547 acanthomorphic acritarch specimens found, 24 genera and 69 species have been identified, including two new genera (Annularidens gen. nov. and Crassimembrana gen. nov.), six new species (Annularidens inconditus gen. et sp. nov., Bispinosphaera vacua sp. nov., Crassimembrana crispans gen. et sp. nov., C. multitunica gen. et sp. nov., Distosphaera jinguadunensis sp. nov., and Mengeosphaera matryoshkaformis sp. nov.), five unnamed species (Annularidens sp., Mengeosphaera sp. 1, Mengeosphaera sp. 2, Sinosphaera sp., and Variomargosphaeridium sp.), and three possible new forms tentatively placed in open nomenclatures (Crassimembrana cf. C. crispans, Tanarium cf. T. conoideum, and Weissiella cf. W. grandistella). The high-resolution fossil occurrence and abundance data from the three sections reveal both spatial variations in acritarch composition, and stratigraphic similarities in acanthomorph range and abundance, indicating that acanthomorph taxa can be applied to biostratigraphic subdivision and correlation only if their stratigraphic records are thoroughly investigated at least at the regional scale. The FADs (first appearance data) of acanthomorph species such as Appendisphaera grandis, Appendisphaera heliaca n. comb., Ericiasphaera fibrilla, and Tianzhushania spinosa, as well as the relative abundance variations of certain taxa, are recognized as promising biostratigraphic markers in lower Doushantuo Formation. The new data also reveal a rapid diversification of marine eukaryotes, with taxonomic richness of acanthomorphs increasing to notable levels within probably ten million years after the termination of the Marinoan glaciation, followed by continuing increase in both taxonomic richness and evenness afterwards.

中文翻译：

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华南扬子三峡地区豆山沱组下段埃迪卡拉纪棘形动物的分布特征：演化与地层意义

摘要 作为早期埃迪卡拉纪地层中最常见的真核生物化石的一部分，棘形动物化石对于理解马里诺斯全球冰川作用后海洋真核生物的生物地层学和进化动力学至关重要。华南长江三峡地区埃迪卡拉纪陡山沱组已报道了丰富多样的棘形动物，并提出了不同的生物分区方案。然而，这些先前公布的生物区是基于从不同地层剖面汇编的生物地层数据，几乎没有努力测试这些生物区是否可以在不同剖面上得到一致识别，尽管区域一致性对于强大的生物地层框架至关重要。还，斗山沱群的演化模式尚未有详细记载，尤其是来自最下部的斗山沱组群，这主要是由于在马里诺全球冰川作用后人们认为分类丰富度较低。在这项研究中，我们报告了来自长江三峡地区九龙湾、金瓜墩和五指山剖面的豆山沱组下部（成员II）燧石结核的硅化棘形动物化石和其他真核微化石。从共发现的1547个棘形动物标本中，共鉴定出24属69种，其中包括2个新属（Annularidens gen. nov.和Crassimembrana gen. nov.）、6个新种（Annularidens inconditus gen. et sp. nov.）。 , Bispinosphaera vacua sp. nov., Crassimembranacrispans gen. et sp. nov., C. multitunica gen. et sp. nov., Distosphaera jinguadunensis sp. 11 月，和 Mengeosphaera matryoshkaformis sp。11 月）、五种未命名的物种（环孢菌属 sp.、Mengeosphaera sp. 1、Mengeosphaera sp. 2、Sinosphaera sp. 和 Variomargosphaeridium sp.），以及三种可能的新形式暂时置于开放命名法中（Crassimembrana cf. C.cripans， Tanarium cf. T. conoideum, 和 Weissiella cf. W. grandistella)。三个剖面的高分辨率化石产地和丰度数据揭示了acritarch组成的空间变化，以及棘形范围和丰度的地层相似性，表明棘形类群只有对其地层记录进行彻底调查才能应用于生物地层细分和对比至少在区域范围内。棘形动物物种的 FAD（首次出现数据），例如 Appendisphaera grandis、Appendisphaera heliaca n。comb.、Ericiasphaera fibrilla 和Tianzhushania spinosa 以及某些分类群的相对丰度变化被认为是下陡山沱组有希望的生物地层标记。新数据还揭示了海洋真核生物的快速多样化，在马里诺冰川结束后大约一千万年内，棘形动物的分类丰富度增加到显着水平，随后分类丰富度和均匀度持续增加。被认为是陡山沱组下段有前景的生物地层标志物。新数据还揭示了海洋真核生物的快速多样化，在马里诺冰川结束后大约一千万年内，棘形动物的分类丰富度增加到显着水平，随后分类丰富度和均匀度持续增加。被认为是陡山沱组下段有前景的生物地层标志物。新数据还揭示了海洋真核生物的快速多样化，在马里诺冰川结束后大约一千万年内，棘形动物的分类丰富度增加到显着水平，随后分类丰富度和均匀度持续增加。