华南早-中泥盆世四足形类形态学与古动物地理研究

The origin and early evolution of tetrapodomorphs (tetrapods plus their finned ancestry) is one of the major event in vertebrate history, which generates wide-spread interest among biologists, palaeontologists and as well as general public for centuries. Living tetrapods (limbed vertebrates) or land vertebrates, such as the frogs, turtles, birds, and mammals, are a subgroup of the tetrapod lineage (tetrapod total-group, or tetrapodomorphs). The lineage also includes finned (the closest known fish relatives to all the land vertebrates, including ourselves) and limbed tetrapods that are more closely related to living tetrapods than to living lungfishes. The discoveries of advanced (‘upper part’) finned stem-tetrapods (e.g., Panderichthys, Tiktaalik), have greatly improved our knowledge of the fin-to-limb transition for invading the land. However, a paucity of fossil data from the lower sector of the tetrapod stem-lineage obstructs profound understanding of the tetrapod origin. Recent HRCT study on the oldest finned stem-tetrapod Tungsenia from China lived in 410 million years ago leaded by the applicant depicted the plesiomorphic condition of the brain in the tetrapods, which indicate that some important brain modifications related to terrestrial life had occurred at the beginning of the tetrapod evolution. However, questions about the origin and early evolution of tetrapods, which concern with many groups of fish-like (i.e., finned) stem tetrapod taxa, remain poorly known. This project tackles the initial stage of tetrapod evolution, one of the significant knowledge gap in vertebrate history, by investigating the early representatives (‘lower part’) of finned stem-tetrapods, and thus resolving the ancestral condition for tetrapod origin. The project aims to leverage developments in computed tomography (CT) to virtually dissect finned stem-tetrapods, gaining new information from largely untapped—but character rich—anatomical systems (e.g., braincase) in understudied/undescribed forms from South China-East Gondwana to understand the evolutionary origin of tetrapod stem lineage.

四足形类包括四足动物与其亲缘关系最近的肉鳍鱼类，是探讨脊椎动物登陆的最关键类群，长期为古生物学与演化生物学界所关注。但至今对四足形类的起源和最早期演化研究十分有限，大量相关科学问题仍未厘清。本项目拟立足中国云南得天独厚的早-中泥盆世早期四足形类化石材料，结合澳大利亚同期相关化石，开展详细的形态学与比较解剖学研究，借助高精度断层扫描，同步辐射相衬扫描，三维打印等先进技术手段探查和重建化石内部结构，揭示早期四足形类重要特征的演化极向和获得序列，对四足形类系统演化及演化速率等进行深入分析，提出新的更有说服力的假说，并结合古地理和古环境背景，为早-中泥盆世时期华南板块与南方冈瓦纳大陆之间的古地理联系，四足形类的起源、早期四足形类的分布、扩散和区域演化，四足形类演化与早古生代环境演变的耦合关系等科学问题提供重要依据和新的假说。该研究将引起国际学术界对四足形类起源与早期演化以及相关古地理研究的更大关注

四足动物支系（又称四足形类，包括所有四足动物及与之密切相关的肉鳍鱼类）于晚泥盆世登陆，演化出包括人类在内的所有陆生脊椎动物，相关演化问题一直是古生物学研究的热点。长期以来，学界对四足动物支系早期演化的了解局限在中晚泥盆世，对该支系的早期化石代表研究十分有限，从而限制了对四足动物支系的起源、内部各类群系统关系，从水到陆适应特征的演化等关键问题的理解。本项目拟立足中国和澳大利亚得天独厚的四足动物支系早期化石材料，使用高精度断层扫描，3D打印等先进技术手段对多种早期四足形类内颅构造进行详细形态学与比较解剖学研究，从而揭示早期四足形类脑颅内部形态，探讨四足动物重要特征演化极向。在更大数据量分支系统学分析框架下，深入探讨四足形类的起源和早期分化、四足形类各主要类群演化关系、泥盆世华南板块与冈瓦纳大陆之间密切联系等国际学术界高度关注的课题。项目将有力带动国际上对四足形类起源、演化以及古地理等相关研究。