Patterns and processes in the evolution of morphological novelty in the amphibian skull

无论是过去还是现在，动物形态的巨大多样性都源于进化的转变。进化的转变，例如从鳍到四肢的转变，几个世纪以来一直吸引着博物学家的注意，并提供了建立进化生物学基本理论所需的观察结果，如自然选择（即，体面的修饰）、同源概念等。一个不太为人所知的转变特征是无尾猿头骨形态的起源。无尾动物（即青蛙、蝾螈和无尾动物）构成了陆地生活脊椎动物（=四足动物）二分法的一半，另一半是羊膜动物（哺乳动物、爬行动物和鸟类）。拟议的研究计划的目标是确定和理解发生在独特的无尾猿头骨形式起源中的进化事件。我推测，这种独特的无尾猿头骨形式，至少在一定程度上是青蛙、蝾螈和无尾猿共同起源过程中共同进化发展事件的结果。我将用互补的方法来解决这个假设，将古生物学数据与现存两栖动物的实验室实验数据综合起来。我还将进行实地考察，以检索新的化石材料，以帮助填补无尾猿化石记录的空白。新斯科舍省石炭纪是两栖动物进化的一个关键时期，已经产生了极为重要的化石，包括世界上最古老的羊膜动物和爬行动物。在过去的五年里，我在新斯科舍省的野外工作产生了大量新的重要发现，从而突出了加拿大的自然遗产，并增加了加拿大古生物学意义的一个方面。对这种新的、目前已知的材料的研究，将揭示出进化事件模式的新方面，这些进化事件导致了非samphibian头骨的形成。结合来自发育实验的数据将阐明这些进化模式背后的机制基础或过程。这项研究的结果将修订我们对这一重大四足动物转变的认识。传统上，无samsamphibians被认为是原始四足动物的代表，因此，经常被用来理解特征转换的本质和方向，这些特征转换似乎定义了羊膜动物的谱系。然而，考虑到化石记录，事实并非如此，这导致了对涉及它们的进化模式的误解。此外，本研究通过完成从深度到实时的项目，在多个层次上解决了有关动物多样性进化的速度和模式的基本问题。

Evolutionary transformations are responsible for the origin of the great diversity of animal form, past and present. Evolutionary transformations, such as the transformation from fins to limbs, have captured the attention of naturalists for centuries and have provided the observations needed to establish fundamental theories in evolutionary biology such as natural selection (i.e., decent with modification), the concept of homology, among others. One poorly understood transformation is that which characterizes the origin of the lissamphibian skull form. Lissamphibians (i.e., frogs, salamanders, and caecilians) comprise one half of the dichotomy of living, land-dwelling vertebrates (=tetrapods), the other half of the dichotomy being amniotes (mammals, reptiles and birds). The goal of the proposed research program is to identify and understand evolutionary events that took place in the origin of the distinct lissamphibian skull form. I HYPOTHESIZE that the distinct lissamphibian skull form is the result, at least in part, of shared evolutionary developmental events that took place during the common origin of frogs, salamanders and caecilians. I will address this hypothesis using complementary approaches, synthesizing paleontological data with that from lab-based experiments with living amphibians. I will also conduct fieldwork to retrieve new fossil material to help fill the gaps in the lissamphibian fossil record. The Carboniferous of Nova Scotia represents a critical time period in the evolution of amphibians and has already produced fossils of paramount significance, including the world's oldest amniote and reptile. My fieldwork in Nova Scotia has yielded a plethora of new important discoveries in the last five years, thereby highlighting Canada's natural heritage and adding a facet to Canada's paleontological significance. Study of this new, and currently known, material will reveal new aspects of the pattern of evolutionary events that gave rise to the lissamphibian skull form. Incorporation of data from developmental experiments will shed light on the mechanistic basis, or processes, underlying these evolutionary patterns. The results of this research will revise our understanding of this major tetrapod transformation. Traditionally, lissamphibians have been viewed as representatives of the primitive tetrapod condition, and, as such, are often used to understand the nature and direction of character transformations that seemingly define the well-studied amniote lineage. However, consideration of the fossil record reveals this is not the case, which has led to misinterpretations of evolutionary patterns involving them. Additionally, this research addresses fundamental questions concerning the tempo and mode of the evolution of animal diversity, on multiple hierarchical levels, through the completion of projects spanning Deep- to Real-time.