本文对贵州募役剖面长兴期腕足动物群进行了系统分类鉴定和古生态分析, 发现其与前人所报道的华南同时期腕足动物群存在着显著的差别, 以Spiriferellina为绝对优势属, 包含少量华南长兴期的常见分子, 如Fusichonetes、Araxathyris和Peltichia等。募役剖面的腕足类化石主要产自碎屑岩层位, 与华南同期碎屑岩相剖面的腕足动物群落相比, 该动物群中的优势分子个体较大、壳体较厚且发育较粗大的壳疹, 这可能与长兴期募役剖面动物群所处的特殊栖息地环境(浅水碳酸盐岩台地与深水硅质碎屑岩盆地之间的过渡地带)有关。二叠纪末期大规模的火山作用导致水体中碎屑物质含量增加, 影响腕足类的滤食效率, 而募役剖面清澈、水动力弱的水体环境, 为滤食性的腕足动物提供了有利的环境条件。最后, 通过与华南长兴期不同沉积相区腕足动物群落(六枝剖面、稻堆山剖面、中寨剖面、新民剖面、马家山剖面和仁村坪剖面群落)的对比分析, 发现募役剖面腕足动物群与毗邻的六枝剖面腕足动物群在属级组成上的相似度较高, 且过渡岩相栖息地环境下的腕足动物群在生物灭绝事件前也呈现出高优势度、低均匀度的群落结构特征, 指示海洋底栖生物群落已经先于二叠纪末期生物集群灭绝事件出现了早期危机信号。

This study reports a Changhsingian brachiopod fauna from the Muyi section (southern Guizhou), which is quite different from other previously reported contemporary brachiopod faunas from South China. This fauna is dominated by Spiriferellina, and contains several genera (e.g., Fusichonetes, Araxathyris and Peltichia) that are commonly found in coeval brachiopod faunas in South China. Compared with the brachiopod faunas from clastic facies of South China, this fauna is dominated by larger and thicker-shelled types with coarse punctae. This could be attributed to the unique paleoenvironment of the Muyi section, which was situated between the shallow-water carbonate platform and deep-water siliceous basin during the Changhsingian. During the end-Permian, massive volcanism resulted in the increased influx of clastic matter into the marine environment, which had a negative influence on the filtering mechanism of the brachiopods. Therefore, the paleoenvironment of the Muyi section with clean water and weak hydrodynamic condition became a relatively better habitat for the brachiopods. In addition, the Muyi brachiopod fauna shares similar composition with the adjacent Liuzhi brachiopod fauna. The Muyi fauna also demonstrates high dominance and low evenness in community structure, like other brachiopod faunas in South China. It may be inferred that the early warning signal had already existed in the benthic brachiopod communities prior to the end-Permian mass extinction.

国家自然科学基金(41902008)、中央高校基本业务费项目(2652018131, 00/800015A302)及现代古生物学和地层学国家重点实验室项目(223137, 223131)联合资助