Collaborative research: Robust estimation of biodiversity dynamics: Global versus regional patterns in the end Ordovician mass extinction of graptolites

点击翻译按钮获取中文摘要

Intellectual Merit- Ceratopsians are among the best known of dinosaur clades due to theirrelative abundance, and the remarkable diversity of cranial synapomorphies such as hornsand frills that diagnose more derived members of the clade. Gigantism is a trend inceratopsian evolution that is accompanied by the evolution of progressively morecomplex feeding mechanisms and cranial display diversity. Heterochrony, and inparticular peramorphosis have been proposed as major influences in ceratopsianevolution to explain the evolution towards large size and late ontogenetic genesis of thedisplay in advanced forms. Likewise, the apparent hierarchical complexity of the feedingapparatus suggests an evolution of character integration through both ontogeny andphylogeny. All of these evolutionary hypotheses require detailed knowledge of both thedevelopment and phylogeny of ceratopsian dinosaurs, but so far age estimates have beenpoorly constrained and non-quantified and rigorous reliance on detailed phylogenieslimited.In this study, an innovative approach to developmentally staging fossils based onhistological sectioning and Developmental Mass extrapolation is combined with noveltree-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 ofceratopsians, we will examine whether there are correlated shifts in developmental timingof synapomorphies (heterochrony) relative to growth strategies, and also if blocks ofcharacters represent integrated modules that fulfill criteria for being phylogenetically andontogenetically constrained. These quantitative studies will allow us to evaluate previoushypotheses on the role heterochrony and integration have played in ceratopsian evolution.By providing a quantified understanding of when in ontogeny synapomorpies areexpressed this research will help to resolve several taxonomic quandaries related to thevalidity of species based on juvenile holotypes and provide a more accurateunderstanding of ceratopsian diversity.Broader Impact: This research represents a new integrative exploration of evolutionaryprocesses in a well-known group of dinosaurs. The novel methods and the results of thisresearch promise to be widely applicable to fields as diverse as population biology,developmental biology, macroevolution and evo-devo, and will be disseminated throughpeer -reviewed journals, presentations at professional meetings and professional web-sites. 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 bothPIs. Both PIs are involved with developing exhibits for natural history museum, andparts of this research will be incorporated into two ongoing exhibit projects, andassociated educational web-sites and programming. Given the media interest in dinosaurresearch, many opportunities to disseminate results of this work to the public will nodoubt arise.