乐平统长期以来一直很有希望成为上二叠统的国际标准 ,只因华南缺乏经过详细论证的乐平统底部层序而未能实现。通过近些年的研究 ,梅仕龙等建立了完整的瓜德鲁普统 -乐平统界线地层的牙形化石带等 ,促成乐平统被正式批准为上二叠统的国际标准 ,并使蓬莱滩剖面成为底界的最佳候选层型剖面。笔者等曾反复论述 Clarkina postbitteri带或 C.dukouensis带之底作为乐平统底界候选层位的优点和缺点。C.dukouensis的演进可以作为 Clarkina 属内渐变群的第一个基准面( datum) ,而且该种分布较广。然而 ,C.dukouensis在 C.postbitteri- C.dukouensis演化种系中的首现本身并无区域对比意义 ,因为 C. dukouensis的首现从未在其他地点发现 ,而首现的层位也不与全球性生物或环境变化的重要事件对应。C.postbitteri带之底接近前乐平统生物绝灭事件的顶峰层位以及在整合层序中厘定的重要层序界面。根据动物群和沉积变化容易进行国际对比这一优越性 ,使该带之底成为最有希望的界线。近些年来 ,国际二叠纪地层分会的工作方案一直将其作为乐平统底界。不过 ,C.postbitteri与祖先种之间的形态变化较显著 ,演化谱系需要充分论证。多年来 ,底界附近的牙形化石被归纳为两个组合带 ,即下部的 Neogondolella bitteri- N.liangshan For a long time, Lepingping had long been promising to become an international standard in the Upper Permian. It was not realized because South China lacked the detailed sequence of the Leping system. In recent years, Mesh Long established the complete Guadalupe - Luping line stratiform alveolar fossils, etc., which led to the official approval of the Leping system as the upper limit of the Permian’s international standard and to Penglai The best candidate layer profile with the beach profile becoming the bottom boundary. The author has repeatedly discussed the advantages and disadvantages of the Clarkina postbitteri band or C. dukouensis band as the candidate horizon of the Leping universal bottom. The evolution of C. dukouensis can be used as the first datum of Clarkina’s in-house gradient group, which is more widely distributed. However, the first manifestation of C. dukouensis in the C.postbitici- C. dukouensis evolutionary lineage is not intrinsically regional in its own right, since the first occurrence of C. dukouensis has never been found elsewhere and the first occurrence is not associated with Global biological or environmental changes correspond to the important events. The bottom of the C.postbitteri zone is close to the peak level of the Pre-Lepta bio-extinction event and the important sequence boundary determined in the integrated sequence. The superiority of international comparisons, based on fauna and sediment changes, makes the bottom of the band the most promising. In recent years, the work program of the international Permian strata has been regarded as the bottom of music. However, the morphological changes between C.postbitteri and ancestral species are significant, and the evolutionary pedigree needs to be fully demonstrated. For years, the dentate fossils near the bottom boundary have been grouped into two assemblages, the lower Neogondolella bitteri- N.liangshan