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

盘古大陆在中生代解体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，鳍鱼的动物群发生了戏剧性的变化。在这个时代之初，鳍鱼在系统发育上是多样化的，并由所有已知的放线蕨类主要支系(枝枝纲、软骨纲、Ginglymodi、HalecMori和Telebone)很好地代表。这些分支中的许多谱系在中生代结束时灭绝，放线蕨类发展成近单系的现代鱼类动物群，主要由硬骨鱼组成(约33.000个活种对14个种。Cladistians，29种。软骨菌，7种。只有一种盐生变型)。经过两个多世纪的研究，尽管与古生物学的其他领域相比，相对较少的专家做出了努力，但我们对中生代放线蕨类的演化速度和模式仍然知之甚少，甚至连放线蕨纲主要支系之间及其内部的系统发育关系也没有很好的了解。根据最近的一项研究，至少自侏罗纪晚期以来，气候变化一直是放线蕨类宏观演化的主要驱动力。然而，这项研究没有包括代表中生代鳍鱼主要类群的足够分类群，其中大多数在这个时代结束时已经灭绝。气候变化是导致这些血统灭绝的主要原因吗？在那些灭绝的谱系中，物种形成和灭绝的速度、特征进化和多样性的速度是多少？这些问题和许多其他问题仍有待回答。所谓的“系统发育比较方法”(PCM)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说。为了通过应用PCM研究中生代鳍鱼进化的宏观进化过程，已经计划了一系列项目，为这些方法的应用提供坚实的系统发育基础。其中，这份提案是献给哈勒科姆人的。对于一个活着的物种，弓鳍，从宏观进化的角度来看，有几个方面使海鞘形目动物特别有趣。盐生形态鱼类在中生代期间非常丰富和多样，特别是在今天的欧洲的侏罗纪，在此期间经历了重大的地理变化，包括丰富的海洋平台和临时的陆表海的发展。侏罗纪的盐生生物在生态上是多种多样的，包括像金枪鱼这样的快速游泳的捕食者，与现存的弓鳍非常相似的海底机会性食肉动物，以及许多更广义的营养形态的小型物种。已知的物种有很多，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.