The Morphologic History of Paleozoic-Triassic Ammonoids

小行星9706232 本次研究将围绕古生代-三叠纪菊石头足类的三个主要主题展开：1。使用每个分类单元21个字符集的主成分分析（PCA），分析含缝合线、全壳形态和形态多样性在空间和时间（泥盆纪-三叠纪）上的变化; 2.菊石缝合线复杂性随时间的演变，作为生物复杂性的单一特征度量，以及关于不同菊石分支中缝合线复杂性的演变; 3.灭绝事件对菊石形态空间、形态多样性和分类多样性的影响，主要集中在三个主要危机上：美国的灭绝事件;泥盆纪弗拉斯期/法门期、泥盆纪/石炭纪和二叠纪/三叠纪。 在菊石调查中，其范围是前所未有的，（a）其时间跨度（~190百万年）;（B）对所有627个古生代菊石属（212个泥盆纪，263个石炭纪，152个二叠纪）的综合处理加上一个额外的25-30属（75-100种）的三叠纪基底菊石的子集。 此外，为了精确地评估大灭绝的时间，并评估这些事件的易感性，持久性和壳形态型的复发，我们将进行PC分析的变化，总共700-750种（~150属）在CA。0.5-5我的间隔跨越每三个灭绝事件。 这项研究将是迄今为止对古生代和中生代早期头足类动物进行的最完整的形态测量处理。 它将为600多个菊石属和另外700多个物种生成一个21+字符的形态测量数据集，该数据集在分类学上是最新的，完整的和地层精确的。 PCA的时间步长分析将允许记录进化枝如何进化，形态多样性和丰富性的变化，以及它们如何应对生物危机。 这些结果将影响到宏观进化变化的解释，复杂性的演变，形态限制和灭绝事件对变异和多样性的影响，所有这些都在近2亿年的时间尺度上。

9706232 Saunders The proposed research will focus on three major themes concerning Paleozoic-Triassic ammonaid cephalopods: 1. Analysis of variation in suture-inclusive, whole-shell morphology and morhphologic diversity through space and time (Devonian-Triassic), using principal components analysis (PCA) of a 21-character set for each taxon; 2. The evolution of ammonoid suture complexity through time, as a single-character measure of biological complexity, and with respect to evolution of suture complexity in different ammonoid clades; and 3. The effects of extinction events on ammonoid morphospace, and on morphologic and taxonomic diversity, focusing on three major crises: the U. Devonian Frasnian/Famennian, the Devonian/Carboniferous, and the Permian/Triassic. The scope is unprecedented in ammonoid investigations, in terms of (a) its time span (~190 my); (b) the comprehensive treatment of all 627 Paleozoic ammonoid genera (212 Devonian, 263 Carboniferous, 152 Permian) plus an additional subset of 25-30 genera (75-100 species) of basal Triassic ammonoids. Additionally, in order to precisely evaluate the timing of major extinction's and to assess susceptibility, persistence, and recurrence of shell morphotypes to these events, we will undertake PC analysis of variation in a combined total of 700-750 species (~150 genera) present during the ca. 0.5-5 my intervals spanning each of the three extinction episodes. This research will be the most complete morphometric treatment of Paleozoic and early Mesozoic cephalopods ever undertaken. It will generate a 21+ character morphometric data-set for more than 600 ammonoid genera and an additional 700+ species that is taxonomically up-to-date, complete and stratigraphically precise. The time-stepped analysis by PCA will permit documentation of how clades evolved, changed in morphologic diversity and richness, and how they responded to biotic crises. The results will have bearing on the interpretation of macro-evolutionary change, the evo lution of complexity, the influence of morphologic constraints and extinction events on variation and diversity, all on a time scale of nearly 200 million years.