Morphological and phylogenetic changes of the hyobranchial apparatus from fishes to basal tetrapods.

需要鱼类在水中吸吮食物的水鳃（内脏骨骼）转变为一种能够以舌头为基础的陆地进食装置，这是四足动物进化的一个关键方面，但人们对它的了解仍然很少。本项目旨在恢复泥盆纪中晚期鱼类向四足动物过渡过程中水鳃的发育变化。必须解决的几个问题包括：(1)非四足动物的哪些水分支结构在基础四足动物中是保守的，(2)哪些是修改的，(3)在这些动物的不同谱系中，水分支是如何用于喂养和呼吸的？本项目将对古生代和中生代基生四足动物及其类鱼类亲缘动物的鳃部遗存进行形态学和系统发育研究。两种假设将得到验证：首先，基础四足动物保留了“鱼一样”的水鳃，并通过颚抓食陆地。在后来的进化过程中，水鳃的个体发生性重塑和可动舌骨架的形成，独立地出现在无水动物和羊膜动物的谱系中。其次，在四足动物的历史中，支持舌头的水分支的个体发育重构很早就开始了，保留“鱼状”的水分支是一种幼体特征。更好地了解水鳃动物的系统发育变化将大大提高我们对鱼类到四足动物的转变和脊椎动物陆生起源的理解。

The transformation of the hyobranchium (visceral skeleton) that requires fishes to suction feeding in water, to an apparatus that enables tongue-based terrestrial feeding, is a key aspect of the evolution of tetrapods, but is still poorly understood. The goal of this project is to recover the developmental changes of the hyobranchium during the fish-to-tetrapod transition in the Middle and Late Devonian. Several questions must be addressed including, (1) which structures of the hyobranchium of nontetrapods were conserved in basal tetrapods, (2) which were modified, and (3) how was the hyobranchium used for feeding and breathing in the different lineages of these animals? The project will focus on the morphological and phylogenetic investigation of the hyobranchial remains of Palaeozoic and Mesozoic basal tetrapods and their fish-like relatives. Two hypotheses will be tested: First, basal tetrapods retained a "fish-like" hyobranchium and fed on land by jaw prehension. Ontogenetic remodelling of the hyobranchium with the elaboration of a movable tongue skeleton evolved later in evolution, independently in the lineage leading to lissamphibians and to amniotes. Second, ontogenetic remodelling for a tongue-supporting hyobranchium evolved early in tetrapod history, and the retention of a "fish-like" hyobranchium is a paedomorphic trait. The better knowledge of phylogenetic changes of the hyobranchium would greatly improve our understanding of the fish-totetrapod transition and the origin of terrestriality in vertebrates.