重庆北碚老龙洞二叠-三叠系界线层中的全脐螺侏儒化:环境突变中的机会群落?

A Dwarf Euomphalid Fauna from the Permian-Triassic Boundary in Laolongdong,Beibei,Chongqing:Opportunity Taxa Surviving the Disaster Event?

本文首次报道重庆北碚老龙洞剖面二叠-三叠系界线附近的全脐螺科的微型腹足类动物群。全脐螺科个体微小,多为盘形、圆锥形,具明显的脐,方解石质的壳壁。区分出研究层内的两类全脐螺,一类是碗形,脐宽而大,脐部深凹;壳壁厚度变化很大,螺环可能上有棱、角或瘤等装饰。另一类是胎壳呈平旋状,呈开放式旋绕;壳壁厚度均匀,未见装饰特征显示。全脐螺类为优势分子的群落在二叠纪末大绝灭事件后盛极一时,如此异常现象可能与浅海区在缺氧之后暂时改善为有氧环境有关,此后随着早三叠世腹足类的全面复苏,它们只能退居为极次要的角色。

This paper has reported for the first time an euomphalid microgastropod fauna from the Permian-Triassic boundary section at Laolongdong,Chongqing.The euomphalids are characterized by planispiral or trochiform shell,obvious umbilicus,and calcite composition of the shell.The euomphalid fauna flourished for a short period after the mass extinction,and its blooming might have been related to the resuming of aerobic environments after an anoxic period.However,in the following time,the abundance of euomphalids kept low and failed to play an important role in the recovery of gastropods in the Early Triassic.