Data from: The Fezouata Shale Formation biota is typical for the high latitudes of the early Ordovician – a quantitative approach

The Fezouata Shale Formation has dramatically impacted our understanding of early Ordovician marine ecosystems before the Great Ordovician Biodiversification Event (GOBE), thanks to the abundance and quality of exceptionally preserved animals within. Systematic work has noted that the shelly fossil sub-assemblages of the Fezouata Shale biota are typical of open-marine deposits from the Lower Ordovician, but no studies have tested the quantitative validity of this statement. We extracted 491 occurrences of recalcitrant fossil genera from the Paleobiology Database to reconstruct 31 sub-assemblages, to explore the paleoecology of the Fezouata Shale and other contemporary, high-latitude (66°S – 90°S) deposits from the Lower Ordovician (485.4 Ma – 470 Ma) and test the interpretation that the Fezouata Shale biota is typical for an Ordovician open-marine environment. Sørensen’s dissimilarity metrics and Wilcoxon tests indicate that the sub-assemblages of the Tremadocian-aged lower Fezouata Shale are approximately 20 percent more heterogenous than the Floian-aged upper Fezouata Shale. Dissimilarity metrics and visualization suggests that while the lower Fezouata and upper Fezouata share faunal components, the two sections have distinct faunas. We find that the faunal composition of the lower Fezouata Shale is comparable with other Tremadocian-aged sub-assemblages from high latitudes, suggesting that it is typical for an early Ordovician open-marine environment. We also find differences in faunal composition between Tremadocian- and Floian-aged deposits. Our results corroborate previous field-based and qualitative systematic studies that concluded that the shelly assemblages of the Fezouata Shale are comparable with those of other Lower Ordovician deposits from high latitudes. This establishes the first quantitative baseline for examining the composition and variability within the assemblages of the Fezouata Shale which will be key to future studies attempting to discern the degree to which it can inform our understanding of marine ecosystems just before the start of the GOBE.费佐塔页岩组（Fezouata Shale Formation）凭借其产出丰富且保存质量极佳的特异埋藏动物，极大地改变了我们对奥陶纪生物大辐射事件（Great Ordovician Biodiversification Event, GOBE）之前早奥陶世海洋生态系统的认知。分类学研究指出，费佐塔页岩生物群的带壳化石亚组合，与下奥陶统开阔海沉积的化石组合特征典型一致，但尚无研究验证这一结论的定量有效性。我们从古生物学数据库（Paleobiology Database）中提取了491个抗腐烂化石属的出现记录，重构了31个亚组合，以此探究费佐塔页岩以及其他同期早奥陶世（4.854亿年至4.70亿年前）高纬度（南纬66°至90°）沉积的古生态学特征，并验证“费佐塔页岩生物群是奥陶纪开阔海环境典型生物组合”这一解释。索伦森相异度指标（Sørensen’s dissimilarity metrics）与威尔科克森检验（Wilcoxon tests）结果显示，特雷马多克世期下部费佐塔页岩的亚组合异质性，较弗洛阶期上部费佐塔页岩高出约20%。相异度指标与可视化分析表明，尽管上下部费佐塔页岩共享部分动物群组成，但二者拥有截然不同的动物群。我们发现，下部费佐塔页岩的动物群组成，与其他高纬度特雷马多克世期亚组合具有可比性，这表明其符合早奥陶世开阔海环境的典型特征。同时我们还发现，特雷马多克世期与弗洛阶期沉积的动物群组成存在差异。本研究结果佐证了此前基于野外实地与定性分类学的研究结论，即费佐塔页岩的带壳化石组合，与其他高纬度下奥陶统沉积的化石组合具有可比性。本研究建立了首个用于分析费佐塔页岩生物群组成与变异性的定量基准，这将为后续研究厘清其在多大程度上能够帮助我们认识奥陶纪生物大辐射事件启动前夕的海洋生态系统，提供关键支撑。