Dissertation Research: A Phylogenetic and Morphometric Analysis of Early Palezoic Archaeogastropods: An Examination of the Expansion of a Clade into Morphospace

古腹足类出现于晚寒武世， 快速辐射以涵盖广泛的形态。 这些 包括大多数与基本腹足类有关的形态类型 生命形式有些 后来发生了轻微的形态学放射， 壳层取向的变化。 因此，古腹足类动物 多个字符类型和形态级别，用于描述 随着时间的推移形态发生变化。 该项目包括系统发育和形态测量 分析了早古生代古腹足类。 这些方法 将被用来比较典型的形态距离 姐妹物种在三种不同形态空间中的差异： 1)一个基于12个“基本外壳”字符， 组的起源; 2）一个基于壳的取向，这并没有 直到晚奥陶世才在大多数亚群中出现; 3） 基于被认为具有基本功能的性格复合体， 效用 使用双折射来比较 在“早期”和“后期”外壳字符中的进化枝扩展将 提供有关分支间和分支内变异 更多地取决于进化枝辐射的时间（即， 外在因素）或角色状态的年龄 区分它们（即，内在因素）。 检查 特征复合体的形态空间中的系统发育模式将 从生物学角度描述古腹足类辐射 有意义的方式，也提供了一个额外的形态学 “水平”来测试进化枝的非随机排序。

The Archaeogastropoda appeared in the Late Cambrian and rapidly radiated to encompass a wide range of morphologies. These included most of the morphotypes associated with basic gastropod lifestyles. A minor morphologic radiation occurred later with changes in shell ornamentation. Archaeogastropods thus offer multiple character types and morphologic levels for describing changes through time in the patterns of morphology. This project includes both phylogenetic and morphometric analyses of Early Paleozoic archaeogastropods. These approaches will be used to compare typical morphological distances of differences between sister species in three different morphospaces: 1) one based upon twelve "basic-shell" characters appearing at the group's origin; 2) one based upon shell ornamentation, which did not appear in most subgroups until the Late Ordovician; and 3) one based upon character complexes thought to have a basic functional utility. Using ornamentation to compare the temporal patterns of clade expansion in both "early" and "later" shell characters will provide information on whether inter- and intraclade variation depend more on the time in which the clade radiated (i.e., extrinsic factors) or upon the ages of the character states distinguishing them (i.e., intrinsic factors). Examining phylogenetic patterns in a morphospace of character complexes will describe the archaeogastgropod radiation in a biologically more meaningful manner and also provide an additional morphologic "level" to test for non-random sorting of clades.