Quantification of ontogenetic change in Triassic ammonoids

中生代菊石具有复杂的缝合线和丰富的贝壳饰物，与古生代前人截然不同。通过拟议的项目，将引入个体发育过程中海螺特征的展开，作为对三叠纪菊石分类多样性和形态差异研究的补充。该项目的重点是菊石贝类生长的两个方面：(1)将利用傅立叶分析和主成分分析等定量方法，分析选定的特提斯和东太平洋三叠纪菊石组合的形态差异，并与具有代表性的古生代动物群进行比较。我们将测试菊石在二叠纪-三叠系边界附近急剧下降后，是否达到了与物种丰富的古生代组合相似的形态变化等级。这些研究将集中在海螺的形态特征上。(2)将对三叠纪菊螺的个体发育变化进行量化，目的是将个体发育过程与系统发育假说联系起来。将开发一种测量海螺形态个体发育变化的方法，作为研究菊科动物Evo Devo的工具。

Mesozoic ammonoids are, with their complex suture lines and rich inventory of shell ornaments, strikingly different from the Palaeozoic predecessors. With the proposed project, the unfolding of conch characters during ontogeny will be introduced as an additional dimension complementing studies of taxonomic diversity and morphological disparity in Triassic ammonoids. The project focuses on two aspects of ammonoid conch growth: (1) The morphological disparity of selected Tethyan and eastern Pacific assemblages of Triassic ammonoids will be analysed and compared with representative Palaeozoic faunas by using quantitative methods such as Fourier Analysis and Principal Component Analysis. We will test if the ammonoids, after their dramatic decline near the Permian-Triassic Boundary, reached similar grades of morphological variation as the species-rich Palaeozoic assemblages. These investigations will focus on the morphometric characters of the conchs. (2) The ontogenetic change of Triassic ammonoid conchs will be quantified with the aim to correlate ontogenetic processes with phylogenetic hypotheses. A method for measuring ontogenetic change in conch morphology will be developed as a tool for Evo Devo studies in ammonoids.