Ray-finned fish evolution during the breakup of Pangaea: the Halecomorphi

中生代泛大陆分裂所产生的地理和气候变化直接影响了脊椎动物的进化。特别是鳍状鱼类的种群发生了巨大的变化。在这个时代的开始，鳍鱼在系统发育上是多样化的，所有已知的放光鳍鱼的主要分支（Cladistia, Chondrostei, Ginglymodi， Halecomorphi和Teleostei）都有很好的代表。这些分支中的许多分支在中生代末期灭绝，放光鳍鱼进化成几乎是单系的现代鱼类，主要由硬骨鱼组成（约33,000种，其中14种是硬骨鱼，29种是软骨鱼，7种是软骨鱼，只有一种是盐形鱼）。经过两个多世纪的研究，尽管与其他古生物学领域相比，相对较少的专家做出了努力，但我们对中生代放光翼类动物的进化速度和模式仍然知之甚少，甚至对放光翼类主要分支之间和内部的系统发育关系也知之甚少。根据最近的一项研究，至少从晚侏罗世以来，气候变化一直是放光翼龙宏观进化的主要驱动力。然而，这项研究没有包括足够的分类群，代表中生代鳐鱼的主要类群，其中大部分在这个时代结束时已经灭绝。气候变化是导致这些物种灭绝的主要原因吗？在那些已灭绝的谱系中，物种形成和灭绝、性状进化和多样化的速率是多少？这些和许多其他问题仍有待解答。所谓的“系统发育比较方法”（PCMs）是探索这些和其他古生物学问题的有力工具，但它们需要强有力的系统发育假设。为了研究中生代射线鳍鱼类的宏观进化过程，我们计划开展一系列项目，为这些方法的应用提供坚实的系统发育基础。其中，本提案是献给Halecomorphi的。就弓鳍这一单一物种而言，从宏观进化的角度来看，有几个方面使Halecomorphi特别有趣。在中生代，特别是今天欧洲的侏罗纪时期，盐形鱼类非常丰富和多样化，在这一时期，欧洲经历了重大的地理变化，包括丰富的海洋平台和暂时的陆表海的发展。侏罗纪的半形动物在生态学上是多种多样的，包括像金枪鱼这样的快速游动的捕食者，与现存的弓鳍非常相似的底栖机会性捕食者，以及许多更广义营养形态的小型物种。已知的种类很多，但它们的高级分类和系统发育关系存在争议。因此，本项目旨在用严格的系统发育方法解决这些鱼类的系统分类学问题。

The geographic and climatic changes produced by the breakup of Pangaea during the Mesozoic directly influenced the evolution of vertebrates. In particular, the faunas of ray-finned fishes changed dramatically. At the beginning of this Era, ray-finned fishes were phylogenetically diverse and well represented by all known actinopterygian major clades (Cladistia, Chondrostei, Ginglymodi, Halecomorphi, and Teleostei). Numerous lineages within these clades went extinct by the end of the Mesozoic and actinopterygians developed into the nearly monophyletic modern fish faunas, composed mostly by teleosts (~33.000 living species vs. 14 spp. cladistians, 29 spp. chondrosteans, 7 spp. ginglymodians, and only one halecomorph). After more than two centuries of research and despite the efforts of the relatively few specialists in contrast to other fields of palaeontology, we still know very little about the tempo and mode of Mesozoic actinopterygian evolution and not even the phylogenetic relationships between and within the major clades of Actinopterygii are well understood. According to a recent study, climate change had been the main driver of actinopterygian macroevolution at least since the Late Jurassic. However, this study does not include sufficient taxa representing the main groups of Mesozoic ray-finned fishes, most of which went extinct by the end of this Era. Was climate change a major driver of the extinction of those lineages? Which are the rates of speciation and extinction, trait evolution and diversification in those extinct lineages? These and many other questions remain to be answered. The so-called ‘phylogenetic comparative methods’ (PCMs) are powerful tools to explore these and other palaeobiological issues, but they require robust phylogenetic hypotheses. With the ultimate aim to study macroevolutionary processes in ray-finned fish evolution during the Mesozoic through the application of PCMs, a series of projects have been planned to provide solid phylogenetic grounds to allow the application of these methods. Amongst them, this proposal is dedicated to the Halecomorphi. With a single living species, the bowfin, several aspects make the Halecomorphi particularly interesting from the macro-evolutionary point of view. Halecomorph fishes were very abundant and diverse during the Mesozoic, in particular in the Jurassic of nowadays Europe, which was subjected to significant geographic changes during that time, including the development of rich marine platforms and temporary epicontinental seas. Jurassic halecomorphs are ecologically varied, including fast-swimming predators like tunas, demersal opportunistic feeders very similar to the living bowfin, and numerous small-sized species of more generalized trophic morphology. Numerous species are known, but their high-level taxonomy and phylogenetic relationships are controversial. Therefore, this project is aimed to solve the systematics of these fishes using rigorous phylogenetic methodology.