Collaborative Research: The Role of Development and Life History Traits in the Evolution of Ceratopsian Dinosaurs

角龙是最著名的恐龙分支之一，因为它们的相对丰富，以及头骨突触的显著多样性，如角和褶皱，诊断出更多派生的支系成员。巨人症是角龙进化的一种趋势，伴随着逐渐复杂的摄食机制和颅骨显示多样性的进化。异时性，特别是永久变态被认为是角鱼进化中的主要影响因素，以解释向大尺寸进化和晚期个体发育的高级形式的显示。同样，喂食装置明显的等级复杂性表明，通过个体发育和系统发育，特征整合的进化。所有这些进化假说都需要对角龙的发育和系统发育有详细的了解，但到目前为止，年龄估计一直是非常有限的和非量化的，严格依赖于详细的系统发育有限。在这项研究中，一种创新的基于组织切片和发育质量外推的化石发育分期方法与新的基于树的方法相结合，利用已建立的角龙系统学研究异时性和整合性。基于代表支系多样性的七个骨干分类群的良好采样生长系列，以及角毛虫的详细系统发育，我们将检查是否存在与生长策略相关的同形(异时性)发育时序的变化，以及特征块是否代表满足系统发育和个体发育受限标准的整合模块。这些定量研究将使我们能够评估先前关于异时性和整合在角龙进化中所起作用的假说。通过提供对个体发育中何时表达联配的量化理解，这项研究将有助于解决几个与基于幼年全貌的物种的有效性相关的分类学难题，并提供对角龙多样性的更准确的理解。广泛影响：这项研究代表了对一组众所周知的恐龙进化过程的新的综合探索。这项研究的新方法和结果有望广泛应用于人口生物学、发育生物学、宏观进化和Evo-Devo等领域，并将通过同行评议的期刊、在专业会议上的陈述和专业网站进行传播。两名研究生和两名本科生将通过这个项目接受培训，研究的各个方面将被纳入两个私人投资机构教授的大学课程。这两个私人投资机构都参与了自然历史博物馆展品的开发，这项研究的部分内容将被纳入两个正在进行的展览项目，以及相关的教育网站和节目。鉴于媒体对恐龙研究的兴趣，无疑将出现许多向公众传播这项工作成果的机会。

Ceratopsians are among the best known of dinosaur clades due to their relative abundance, and the remarkable diversity of cranial synapomorphies such as horns and frills that diagnose more derived members of the clade. Gigantism is a trend in ceratopsian evolution that is accompanied by the evolution of progressively more complex feeding mechanisms and cranial display diversity. Heterochrony, and in particular peramorphosis have been proposed as major influences in ceratopsian evolution to explain the evolution towards large size and late ontogenetic genesis of the display in advanced forms. Likewise, the apparent hierarchical complexity of the feeding apparatus suggests an evolution of character integration through both ontogeny and phylogeny. All of these evolutionary hypotheses require detailed knowledge of both the development and phylogeny of ceratopsian dinosaurs, but so far age estimates have been poorly constrained and non-quantified and rigorous reliance on detailed phylogenies limited.In this study, an innovative approach to developmentally staging fossils based onhistological sectioning and Developmental Mass extrapolation is combined with novel tree-based methods toward studying heterochrony and integration using a well established phylogeny of Ceratopsia. Based on well-sampled growth series of seven backbone taxa representing the diversity of the clade, and a detailed phylogeny of ceratopsians, we will examine whether there are correlated shifts in developmental timing of synapomorphies (heterochrony) relative to growth strategies, and also if blocks of characters represent integrated modules that fulfill criteria for being phylogenetically and ontogenetically constrained. These quantitative studies will allow us to evaluate previous hypotheses on the role heterochrony and integration have played in ceratopsian evolution.By providing a quantified understanding of when in ontogeny synapomorpies are expressed this research will help to resolve several taxonomic quandaries related to the validity of species based on juvenile holotypes and provide a more accurate understanding of ceratopsian diversity.Broader Impact: This research represents a new integrative exploration of evolutionary processes in a well-known group of dinosaurs. The novel methods and the results of this research promise to be widely applicable to fields as diverse as population biology, developmental biology, macroevolution and evo-devo, and will be disseminated through peer -reviewed journals, presentations at professional meetings and professional websites. Two graduate and two undergraduate students will be trained through this project, and aspects of the research will be incorporated into university courses taught by both PIs. Both PIs are involved with developing exhibits for natural history museum, and parts of this research will be incorporated into two ongoing exhibit projects, and associated educational web-sites and programming. Given the media interest in dinosaurresearch, many opportunities to disseminate results of this work to the public will no doubt arise.