The Morphologic History of Paleozoic-Triassic Ammonoids

9706232.拟议的研究将集中在古生代-三叠纪菊科头足类动物的三个主要主题上：1.利用每个分类单元21个特征集的主成分分析，分析缝合线包含性、全壳形态和形态多样性随时间的变化(泥盆纪-三叠纪)；2.菊状线复杂性随时间的演变，作为生物复杂性的单特征量度，以及不同菊形支系中缝合线复杂性的演变；3.灭绝事件对菊石形态空间、形态和分类多样性的影响，重点讨论了三个主要危机：美国泥盆纪的弗拉斯期/法门期、泥盆纪/石炭纪和二叠纪/三叠纪。在菊石研究方面，其范围是前所未有的：(A)其时间跨度(约190我)；(B)对所有627个古生代菊石属(泥盆纪212个，石炭纪263个，二叠纪152个)的综合处理，以及额外的25-30属(75-100种)基础三叠纪菊石。此外，为了准确地评估大灭绝的时间和评估贝壳形态类型对这些事件的敏感性、持久性和重现性，我们将对大约0.5-5My间隔期间存在的700-750种(约150属)的贝壳形态类型进行PC分析，跨越三次灭绝事件的每一次。这项研究将是有史以来对古生代和早中生代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个物种生成一个21个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、在地层学上是精确的。PCA的时间步进式分析将允许记录支系如何进化、形态多样性和丰富度的变化，以及它们如何应对生物危机。这些结果将影响对宏观进化变化的解释、复杂性的演化、形态约束和灭绝事件对变异和多样性的影响，所有这些都是在近2亿年的时间尺度上进行的。

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.