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

角龙类是最著名的恐龙分支之一，因为它们的相对丰富，以及颅部突触形态的显着多样性，如角和褶边，可以诊断出该分支的更多衍生成员。巨人症是角龙类进化的一种趋势，伴随着逐渐复杂的进食机制和颅骨显示多样性的进化。异时性，特别是peramorphosis已被提出的主要影响角龙类的进化，以解释向大尺寸和晚期个体发育发生的先进形式的显示器的演变。同样地，喂食器明显的层级复杂性暗示了通过个体发育和生殖发育的性格整合的进化。所有这些进化假说都需要对角龙类恐龙的发育和进化过程有详细的了解，但到目前为止，年龄估计受到很大的限制，而且没有量化，严格依赖于详细的进化过程有限。一种基于组织切片和发育质量外推的化石发育分期的创新方法与新树相结合，基于方法研究异时性和整合使用良好的Ceratopsia系统发育。基于良好的采样增长系列的7个骨干类群代表的多样性的分支，和一个详细的ceratopsians，我们将研究是否有相关的变化，在发育时间的synapomorphies（异时性）相对于增长策略，也如果块字符代表集成模块，满足标准的发育和个体发育的限制。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类进化中所起作用的假设。通过提供对个体发育中突触型何时表达的定量理解，这项研究将有助于解决与基于幼年全型的物种有效性相关的几个分类学难题，并提供对角龙类多样性的更准确理解。这项研究代表了一个著名的恐龙群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种群生物学，发育生物学，宏观进化和进化-发育等领域，并将通过同行评审期刊，专业会议和专业网站上的演讲进行传播。两名研究生和两名本科生将通过这个项目进行培训，研究的各个方面将纳入两个PI教授的大学课程。这两个PI都参与了自然历史博物馆的展品开发，这项研究的一部分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编程。鉴于媒体对生物多样性研究的兴趣，毫无疑问，将有许多机会向公众传播这项工作的成果。

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.