腕足动物是古生代海洋中最重要的底栖生物类群之一, 然而该门类在二叠纪–三叠纪之交大灭绝中遭受巨大的打击, 在中、新生代海洋中被严重地边缘化。为了评价大灭绝对腕足类宏演化过程的影响, 本文聚焦于大灭绝后的复苏过程, 从多样性、壳饰演化、古地理区系三个方面分析全球腕足动物的复苏过程与模式。多样性统计表明, 腕足类的属级分异度大灭绝后大幅降低, 在安尼期快速上升, 并在诺利期达到三叠纪最高水平。相较于晚三叠世的新生分子, 多数早三叠世的新生属种消亡更快, 多为短延限分子。早三叠世至早侏罗世腕足类各个目的壳饰演化趋势迥异, 说明并非受同一因素控制; 壳饰的发育程度与被捕食压力并没有必然联系。相反, 不同腕足目自身的演化历史对壳饰变化具有更显著的影响。网络分析发现腕足类的古生物地理分区性在大灭绝后显著下降, 至奥伦尼克期才再次出现分异现象。中三叠世各地出现大量土著分子, 使腕足类古生物地理分异性更加明显, 甚至可能超过了大灭绝前的水平。
The Brachiopoda is one of the most important components in the Paleozoic benthic community. During the Permian-Triassic (P-Tr) mass extinction, many orders of this phylum were wiped out. Brachiopods became a marginal group in the Mesozoic and Cenozoic oceans. To investigate the effects of the P–Tr extinction on the macroevolution of this clade, we re-evaluated the diversity variations of global brachiopods during the Triassic, traced the evolutionary trend of the development of ornamentation of the Triassic and Early Jurassic elements, and analyzed the changes of brachiopod paleobiogeographic provincialisms before and after the extinction. Taxonomic diversity at the genus level abruptly declined across the P–Tr crisis, increased rapidly in the Anisian, and finally reached the highest level of the Triassic during the Norian. Compared with genera that originated in the Late Triassic, those originated in the Early Triassic are shorter in longevity. The novel ornamentation index was employed to evaluate the development of the ornamentation of brachiopods. The results show that the four main orders of the early Mesozoic brachiopods behaved differently in ornamental evolution, suggesting that their ornamental trajectories were not controlled by a common factor. Compared with the escalation-driven evolution, their evolutionary history played a more important role. The ornamentation development shows no significant relationship with the strengthened predation pressure, at least during the early Mesozoic. Network analysis indicates that the paleobiogeographic provincialism disappeared after the extinction, and re-emerged in the Olenekian. Along with the occurrence of many endemic elements during the Middle Triassic, the affinities of brachiopod faunas became much lower among various regions in the world.
国家自然科学基金(41821001, 41830323, 41930322)、教育部 111 项目(BP820004)和中国地质大学中央高校基本科研业务费联合资助