Abstract Macroalgae play a crucial ecological and biogeochemical role in modern marine ecosystems. Although eukaryotic algae have a deep history within the Precambrian, most pre-Cryogenian alga fossils are microscopic and macroalga fossils are poorly documented during this period. Here we report a well-preserved assemblage of macroscopic and diversified carbonaceous compression fossils from the Tonian Shiwangzhuang Formation in western Shandong, North China. This assemblage consists of seventeen distinct morphotaxa, including eleven macroalgae, showing remarkable taxonomic diversity that is more diverse than many other Tonian macrofossil assemblages all over the world. Three taxa from the Shiwangzhuang assemblage show evidence of simple multicellularity with two of them consisting of giant cells and comparable to giant-celled green algae, and seven taxa with diagnostic transverse annulations are likely coenocytic algae. The Shiwangzhuang assemblage indicates that some eukaryotic clades had achieved macroscopic growth through simple multicellularity or coenocytism, paving the way, either ecologically or phylogenetically, for the eventual appearance of complex multicellularity. In addition, there are some biostratigraphically significant genera, including the Chuaria-Tawuia and Sinosabellidites-Protoarenicola-Pararenicola assemblages, indicating a Tonian age for the Shiwangzhuang Formation. This study also suggests that the Tonian diversity of multicellular or coenocytic macroalgae is probably underestimated, pending for a systematic and thorough investigation of Tonian macroscopic carbonaceous compressions. Macroalgae may have an initial ecological expansion, at least locally if not globally, in the Tonian Period.

中文翻译：

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华北鲁西托年石王庄组宏观多样的碳质压缩化石组合

摘要 大型藻类在现代海洋生态系统中起着至关重要的生态和生物地球化学作用。尽管真核藻类在前寒武纪有着悠久的历史，但大多数前低温纪的藻类化石都是微观的，而在此期间大型藻类化石的记录很少。在这里，我们报告了华北山东西部托年石王庄组保存完好的宏观和多样化碳质压缩化石组合。该组合由 17 种不同的形态分类群组成，包括 11 种大型藻类，显示出显着的分类多样性，比世界各地的许多其他托尼亚大型化石组合更加多样化。来自石王庄组合的三个分类群显示出简单的多细胞性证据，其中两个由巨细胞组成，可与巨细胞绿藻相媲美，7 个具有诊断性横向环化的分类群很可能是雌核藻类。石王庄组合表明，一些真核生物进化枝通过简单的多细胞或异核细胞实现了宏观生长，为复杂多细胞的最终出现在生态或系统发育方面铺平了道路。此外，还有一些在生物地层学上具有重要意义的属，包括 Chuaria-Tawuia 和 Sinosabellidites-Protoarenicola-Pararenicola 组合，表明石王庄组属于 Tonian 时代。这项研究还表明，多细胞或同核巨藻的托尼多样性可能被低估了，有待对托尼宏观碳质压缩进行系统和彻底的调查。大型藻类可能有初步的生态扩张，