Investigating Heterochrony in the Fossil Record: A Geochemical, Morphometric, and Phylogenetic Study of Thecideidina (Brachiopoda), Triassic-Recent.

Carlson Heterochrony，发育速度和时间变化的进化结果，被认为是进化发生的最重要的手段之一。完全记录异时性需要了解生长速度、系统发育关系以及推测的祖先和后代的个体发育大小和形状变化。这项研究的目的是了解异时性在腕足类起源和进化中的作用，腕足类是一类鲜为人知的小型底栖、胶结、泛热带、神秘的无脊椎动物，具有长期的化石记录(三叠纪)和新颖的形态。我们将使用基于简约的、形态系统发育的方法来建立强有力的假说，以证明这些甲壳虫物种和属之间的关系，以及甲壳虫与其他有关节的腕足类之间的关系。我们将通过分析连续贝壳生长层的微量样品的氧同位素组成来记录甲硫氨酸的生长速度，以量化整个个体发育过程中的大小-年龄-生长关系。最后，我们将利用多变量形态计量学方法来记录伴随个体发育尺寸增加而发生的形状变化，并描述观察到的成虫形态的范围。系统发育、地球化学和形态计量学的结果将被结合起来，以检验异时性是否以及以何种方式对这些环磷酰胺的起源和进化负责。这项研究的结果将提供化石记录中罕见的、严格的异时性测试，考虑到所有三个主要组成部分：系统发育关系、生长速度以及形状和大小的变化。

9902984CarlsonHeterochrony, the evolutionary consequences of changes in the rate and timing of development, is considered to be one of the most important means by which evolution occurs. Documenting heterochrony fully requires knowledge of growth rates, phylogenetic relationships, and ontogenetic size and shape change for putative ancestors and descendants. The goal of this study is to understand the role of heterochrony in the origin and evolution of thecideidine brachiopods, a poorly understood group of small, benthic, cemented, pan-tropical, cryptic invertebrates with a long fossil record (Triassic - Recent) and novel morphologies. We will use parsimony-based, morphologic phylogenetic methods to develop robust hypotheses of relationship among thecideidine species and genera, and of thecideidines to other articulated brachiopods. We will document thecideidine growth rates by analyzing the oxygen isotopic composition of microsamples of successive shell growth layers, to quantify size-age-growth relationships throughout ontogeny. Finally, we will utilize multivariate morphometric methods to chronicle shape change that accompanies ontogenetic size increase and characterizes the range of observed adult morphologies. Phylogenetic, geochemical, and morphometric results will be combined to test whether, and in what ways, heterochrony is responsible for the origin and evolution of thecideidines. The results of this study will provide a rare, rigorous test of heterochrony in the fossil record by accounting for all three primary components: phylogenetic relationship, growth rate, and shape and size change.