The Morphologic History of Paleozoic-Triassic Ammonoids

拟开展的古生代-三叠纪氨壳类头足类研究主要集中在三个方面：利用主成分分析（PCA）对各分类单元的21个特征集进行包络、全壳形态和形态多样性的时空变化分析（泥盆纪-三叠纪）；2. 作为生物复杂性单一特征的氨系缝线复杂性随时间的演化，以及不同氨系分支缝线复杂性的演化；和3。灭绝事件对氨形态空间、形态和分类多样性的影响，重点关注三个主要危机：美国泥盆纪弗拉斯纪/法门纪、泥盆纪/石炭纪和二叠纪/三叠纪。这一范围在氨类研究中是前所未有的，就：(a)它的时间跨度（~190年）；(b)综合处理了627个古生代氨气属（泥盆纪212属、石炭纪263属、二叠纪152属）和另外25-30个基三叠纪氨气属（75-100种）。此外，为了准确地评估大灭绝的时间，并评估壳形态对这些事件的易感性、持久性和复发性，我们将对三次灭绝事件中约0.5- 5my间隔内出现的700-750种（约150属）的变异进行PC分析。本研究将是迄今为止对古生代和早中生代头足类动物进行的最完整的形态计量学研究。它将为600多个氨类属和700多个物种生成21多个特征的形态测量数据集，这些数据集在分类上是最新的，完整的，地层精确的。PCA的时间步进分析将允许记录枝是如何进化的，形态多样性和丰富度的变化，以及它们如何应对生物危机。这些结果将在近2亿年的时间尺度上对宏观进化变化、复杂性进化、形态约束和灭绝事件对变异和多样性的影响进行解释。

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.