志留纪潇湘脊椎动物群与有颌类早期分化研究

The Silurian Period heralded the rise and diversification of all groups of gnathostomes (jawed vertebrates) - the extinct placoderms and crown gnathostomes, the latter comprising two major lineages, namely Chondrichthyes (cartilaginous fishes) and Osteichthyes (bony fishes and tetrapods). The rise of jawed vertebrates from jawless ostracoderm fishes, the split of crown gnathostomes into Chondrichthyes and Osteichthyes, and the origin and early radiation of bony fishes are key transitions in vertebrate evolution. Recent findings from the Xiaoxiang Vertebrate Fauna (Silurian, Ludlow), e.g. Guiyu, Entelognathus, Megamastax, resulted in a series of major breakthroughs about the early evolution of fishes, and revealed the unexpected diversity of jawed vertebrates in the Silurian. This project aims to conduct extensive field investigations and excavations in the Silurian of Qujing, Yuanan, and hopes to enrich the diversity of the Xiaoxiang Vertebrate Fauna. The field works will be followed up by laboratory preparation and research to obtain critical information bearing on the origin and early diversification of gnathostomes. By exploiting the HRCT scanning facilities in IVPP, the project is to perform a phylogenetically broad comparative study among jawless galeaspids and early gnathostomes, the results of which can help to establish the sequences of character acquisition leading to the origin of crown ganathostomes, and to the origin of osteichthyans. Specifically, we will focus on placoderms, whose phylogenetic relationship is currently disputed due to the transitional forms from the Silurian of China. We will also investigate the faunal turnover between the Silurian Xiaoxiang Vertebrate Fauna and the Early Devonian Xitun Vertebrate Fauna. A solid phylogenetic scenario resulted from the planned project can also serve as a basis to investigate the interaction between major evolutionary events and environmental changes. The project will constitute a challenging and rewarding opportunity to bring about new breakthroughs in the study of the early diversification of gnathostomes, and related paleoecological issues.

围绕生物演化主题、立足我国得天独厚的早期脊椎动物化石资源优势(门类齐全、出现时代早、原始类型多)，深入探讨有颌类各大类群(“盾皮鱼纲”、软骨鱼纲和硬骨鱼纲)的起源与早期演化。通过采用高精度断层扫描、三维复原技术等手段，对新发现的（主要采自志留纪潇湘脊椎动物群层位）和已有的志留纪-早泥盆世有颌类化石开展细致的形态学与比较解剖学工作，完善有颌类各大类群的性状分析数据库，并丰富志留纪有颌类的多样性；在此基础上，深入开展有颌类的系统学研究，为揭示有颌类各大类群以及各大类群之间的系统发育关系提供更多有说服力的化石证据，从而完善有颌类的早期演化框架；通过对生物地层学、沉积学、地球化学等的综合研究，恢复云南曲靖志留纪-早泥盆世期间的古环境，揭示潇湘脊椎动物群与早泥盆世西屯脊椎动物群之间多样性演替关系,探讨有颌类早期分化的环境制约因素。该项目的实施将带动国际上对有颌类起源、早期演化以及相关古环境等的研究。

有颌类的起源与早期分化是重建有颌类演化之树的关键，对于脊椎动物演化的研究具有十分重要的意义。然而囿于早期有颌类化石材料的稀缺，有颌类的早期演化历史长期以来一直笼罩在迷雾之中，有关研究成为“生命之树”研究中的一个薄弱方向。云南曲靖等地发现的志留纪潇湘脊椎动物群和早泥盆世西屯脊椎动物群中大量的化石材料表明：华南特别是滇东是最有可能为解答有颌类起源及其内部各大类群分化问题提供关键证据的地区。. 项目围绕有颌类起源与早期演化这一主题，对已有及项目实施期间采获的硬骨鱼类、盾皮鱼类、软骨鱼类、盔甲鱼类的重要化石材料开展了详细的形态学研究，并在此基础上，结合能够填补形态缺环的重要化石发现，完善了盔甲鱼类与有颌类各大类群的性状分析数据库、深入开展了早期脊椎动物各大类群的系统发育分析研究，重建了有颌类早期演化框架。同时开展了生物地层学、沉积学、地球化学等的综合研究，进一步完善了华南特别是滇东地区志留纪-早泥盆世地层框架，初步阐明了志留纪-早泥盆世脊椎动物的生态环境、脊椎动物群演替过程及其与古环境的协同演变关系。. 项目执行以来，在华南特别是曲靖地区志留系-泥盆系中发现并采获大量保存绝佳的早期脊椎动物化石新材料，在硬骨鱼类、盾皮鱼类、软骨鱼类、盔甲鱼类的形态学与系统学研究中取得系列创新性科研成果，并在早期脊椎动物特别是有颌类的早期演化框架、有颌类早期分化的环境制约因素以及相关的生物地层学等方面取得了一些突破性科研成果及重要进展，圆满完成了项目的预期目标。迄今发表相关的标注论著38篇/部，其中专著1部、SCI论文28篇，包括NI论文6篇（含Science、Nature论文各1篇）。本项目实施期间取得的系列鱼化石新发现及重要科研进展，不仅为解答有颌类早期分化、潇湘脊椎动物群多样性研究等重要课题提供了有说服力的证据，而且推动了国际上早期脊椎动物起源、演化以及相关古环境等的研究，进一步巩固了我国在早期脊椎动物研究领域中的国际影响力。