作为中三叠世这一重要地质历史时段事件的重要时间坐标，牙形石生物地层能够确定重要地层界线，确定特殊产出化石的时代，为重要生物演化及环境事件提供标准时间坐标，有着非常重要的研究意义。然而与下三叠统约5个百万年内划分出的11个牙形石带相比，中三叠统约1千万年内仅划分出13个牙形石带，其精度仍需要提高。中三叠统内一些建带关键牙形石属种的首现也还需要更多精细研究。我国仍然缺少最新国际地层表中使用的一些中三叠统牙形石带的标准分子。因此，需要对我国中三叠统高精度牙形石生物地层进行详细研究。鉴于此，本项目拟选择在我国发育有良好的海相中三叠统的，有着良好的前人研究基础的，易于达到的云南、贵州、广西等地选择一些重要的剖面，进行牙形石样品连续采集工作，通过牙形石分类学、谱系研究，建立各剖面高精度的牙形石生物地层，从而建立我国中三叠统高精度的牙形石生物地层格架，为国际中三叠统地层表做出贡献。

As an important time scale of the key Middle Triassic Epoch, conodont biostratigraphy has important significances due to their roles in determining important stratigraphic boundaries and the age of special fossil bearing beds, providing standard time scale for the key biological evolution and environmental events. While comparing with the eleven conodont zones in the 5 Myr Lower Triassic, there are only thirteen conodont zones in the 10 Myr Middle Triassic. Hence, a more detailed conodont biostratigraphy of the Middle Triassic is needed. And, some key conodont species for the zonation need to be further studied for checking their first appearances. Additionally, some standard conodonts for the zonation in the Middle Triassic are still absence in China. In view of above, this project is planned to choose some important sections from the Yunnan, Guizhou and Guangxi areas, which has well preserved Middle Triassic strata, numerous previous researches and easy to access, to collect continuous conodont samples. Based on the designed conodont taxonomic and phylogenic work in this project, it is aimed to establish high-resolution conodont biostratigraphy of each section, accordingly, the high-resolution conodont biostratigraphy frame of the Middle Triassic, and contribute to the Geological Time Scale.