Data from: Ecological consequences of the Guadalupian extinction and its role in the brachiopod-mollusk transition

The Guadalupian (middle Permian) extinction may have triggered substantial ecological restructuring in level-bottom communities, such as turnover in dominant brachiopod genera or a shift from abundant brachiopods to mollusks, despite comparatively minor taxonomic losses. However, ecological changes in relative abundance have been inferred from limited data; as a result, constraints on important shifts like the brachiopod-mollusk transition are imprecise. Here, I re-evaluate the magnitude of ecological shifts during the Guadalupian-Lopingian (G-L) interval by supplementing previous census counts of silicified assemblages with counts from non- silicified assemblages and global occurrence data, both sourced from the Paleobiology Database. Brachiopod occurrences are consistent with more pronounced faunal composition changes from the Guadalupian to Lopingian than among stages within those intervals, but only in Iran and South China, and not in Pakistan or a Tethys-wide dataset. In Iran and South China, Bray-Curtis dissimilarity values comparing occurrence frequencies between adjacent stages were elevated across the G- L transition, although other intervals exhibited similarly large shifts. However, genus occurrence frequencies were less strongly correlated or were anti-correlated across the G-L transition, suggesting moderate faunal turnover among dominant brachiopod genera. In contrast to previous inferences from silicified faunas, abundances of brachiopods, bivalves, and gastropods remained consistent from the Guadalupian to Lopingian in non-silicified local counts and global occurrences, implying that the brachiopod-mollusk shift did not occur until the end-Permian extinction. Ecological and taxonomic consequences were both minor in level-bottom settings, suggesting that severe environmental perturbations may not be necessary to explain biotic changes during the Guadalupian-Lopingian transition.

瓜德鲁普世（Guadalupian，中二叠世）灭绝事件可能引发了平底底栖群落（level-bottom communities）的大规模生态重组，例如优势腕足类（brachiopod）属的更替，或是从繁盛的腕足类向软体动物（mollusk）的转变，尽管其造成的分类群损失相对较小。然而，此前关于相对丰度的生态变化推论仅基于有限的数据；因此，对腕足类-软体动物转变这类关键转变的约束尚不精确。本文通过补充此前硅质化石组合（silicified assemblages）的普查统计数据，新增非硅质化石组合（non-silicified assemblages）的统计数据与均来自古生物学数据库（Paleobiology Database）的全球物种出现记录，重新评估了瓜德鲁普世-乐平世（G-L）间隔期的生态转变幅度。腕足类出现记录显示，相较于两个世内的各地质阶段，瓜德鲁普世至乐平世的动物群组成变化更为显著，但这一现象仅见于伊朗与华南地区，在巴基斯坦或全特提斯洋数据集中并未出现。在伊朗与华南地区，相邻阶段间出现频率对比的布莱-柯蒂斯相异度（Bray-Curtis dissimilarity）值在G-L过渡阶段有所升高，尽管其他间隔也出现过类似的大幅转变。不过，属级出现频率在G-L过渡阶段的相关性较弱，甚至呈负相关，表明优势腕足类属发生了中等程度的动物群更替（faunal turnover）。与此前基于硅质化石群的推论不同，在非硅质化石本地统计数据与全球出现记录中，腕足类、双壳类（bivalve）与腹足类（gastropod）的丰度在瓜德鲁普世至乐平世期间保持稳定，这意味着腕足类-软体动物转变直至二叠纪末灭绝事件才发生。平底底栖环境中的生态与分类学后果均较为轻微，这表明瓜德鲁普世-乐平世过渡期间的生物变化或许无需用剧烈的环境扰动来解释。