DISSERTATION RESEARCH: Comparative ontogeny: dinosaur growth, development, and intraspecific variation

代谢率的变化往往伴随着生物功能和生态的重大进化转变。例子包括原始龙(鸟类及其近亲，约12,000种)和哺乳动物(约5,000种)的吸热(温血)进化和新陈代谢增强。高代谢率被认为是哺乳动物和始祖龙物种辐射的关键组成部分，因为它允许个体利用更广泛的环境和时间生态位(生活方式)。就它们的体型而言，现存的鸟类是所有脊椎动物中生长速度和新陈代谢最快的。鸟类的高代谢率也与高度管道化的发育有关，这从特定年龄的个体相对缺乏体型变化中可以看出。这项研究的主要目的是了解这些极端的生理和发育特化是如何在鸟类的恐龙祖先中产生的。这个项目将产生两个更广泛的重大影响。首先，这个项目产生的数据和解释将被纳入美国自然历史博物馆(AMNH)目前正在开发的一个展览的更新中，？我们中间的恐龙。这个展览是一个多媒体展示，展示了支持鸟类从非鸟类恐龙进化而来的假设的各种证据。它使用化石标本、模型、图形和互动来揭示许多典型鸟类特征的恐龙起源的最新发现。私人投资机构积极参与咨询展览的科学内容，连同相关的博物馆活动和广泛的在线活动，将接触到AMNH和全球许多其他机构每年500万参观者中的很大一部分。展览中的教育材料将接触到不同的学生群体，其中许多人来自纽约市服务不足的社区。其次，该项目极大地加强了AMNH古生物学实验室对化石组织进行组织学研究的基础设施。组织学技术培训将使PIS能够进一步培训AMNH工作人员和学生，开发实验室的人力资源，以支持未来几年涉及组织分析的项目。从恐龙的骨骼微结构计算恐龙的生长率(新陈代谢的替代指标)表明，向现代鸟类吸热的过渡不是一步到位的。例如，最早的鸟类比非鸟类爬行动物生长得快，但比它们现存的后代生长得慢。然而，鸟类最早的兽脚类恐龙祖先代谢率升高的原因尚不清楚。该项目试图填补这一知识空白，通过使用骨组织学(骨组织的微观组织检查)和大体形态来测量基于系统发育的兽脚亚目恐龙Coelophysis bauri的生长速度和个体发育渠化。由于它是仅有的从单个种群获得大量样本(数百个标本)的已灭绝恐龙之一，因此，对腔藻进行组织切片和生长曲线构建将有助于揭示一些最早分化的兽脚类恐龙的代谢状况，并提供一个框架，在此框架内可以评估鸟系始祖龙向快速生长和发育管道化的过渡。

Shifts in metabolic rates often accompany major evolutionary transitions in organismal function and ecology. Examples include the evolution of endothermy (warm-bloodedness) and elevated metabolism in archosaurs (birds and their close relatives, ~12,000 species) and mammals (~5,000 species). High metabolic rates are thought to be a key component of mammalian and archosaur species radiations, by allowing individuals to exploit a wider range of environmental and temporal niches (lifestyles). For their body size, extant birds have some of the highest growth rates and metabolisms of any vertebrates. High avian metabolic rates are also associated with highly canalized development, as seen in the relative lack of body size variation for individuals of a given age. The primary aim of this research is to understand how these extreme physiological and developmental specializations arose within the dinosaur ancestors of birds. This project will produce two major broader impacts. First, data and interpretations generated by this project will be incorporated into updates to an exhibit currently in development at the American Museum of Natural History (AMNH), ?Dinosaurs Among Us.? This exhibit is a multi-media showcase of the various lines of evidence supporting the hypothesis that birds evolved from non-avian dinosaurs. It uses fossil specimens, models, graphics, and interactives to reveal the latest findings about the dinosaurian origins of many typically avian traits. The PIs are actively involved in consulting on the scientific content of the exhibit, which, together with associated museum events and an extensive online presence, will reach a large portion of the 5 million annual visitors to AMNH and many others globally. Educational materials from the exhibit will reach a diverse group of students, many from underserved communities in New York City. Second, this project greatly enhances the infrastructure of the AMNH paleontology laboratory to conduct histological research on fossil tissues. Training in histological techniques will enable the PIs to further train AMNH staff and students, developing the human resources of the laboratory to support projects involving histological analysis for years to come. Calculation of dinosaur growth rates (a proxy for metabolism) from their bone microstructure has demonstrated that the transition to modern avian endothermy did not occur in a single step. The earliest birds, for example, grew more rapidly than non-avian reptiles, but more slowly than their extant descendants. However, the origin of elevated metabolic rates among the earliest theropod dinosaur ancestors of birds remains unknown. This project seeks to fill this gap in knowledge, by using bone histology (examination of the microscopic organization of bone tissue) and gross morphology to measure growth rate and ontogenetic canalization for a phylogenetically basal theropod dinosaur, Coelophysis bauri. As it is one of the only extinct dinosaurs with a large sample size (hundreds of specimens) available from single populations, histological sectioning and growth curve construction for Coelophysis bauri will shed light on the metabolic condition of some of the earliest diverging theropod dinosaurs, and provide a framework within which the transition to rapid growth rates and developmental canalization among bird-line archosaurs may be assessed.