A palaeontological solution to the origin of the vertebrate pectoral girdle

脊椎动物胸带起源的古生物学解决方案

• 批准号: NE/X015335/1
• 负责人: Martin Brazeau
• 金额: $ 70.49万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX015335%2F1
• 关键词: palaeontological; solution; origin; vertebrate; pectoral

Paired fins were among the most critical anatomical innovations in vertebrate animals. These structures originated in the ancestors of jawed vertebrates more than 430 million years ago and formed the evolutionary foundation for all vertebrate limbs, including our own arms and legs. For over 150 years, evolutionary biologists have puzzled over the origins of these structures, which gave rise to a bewildering array of adaptations for movement, such as swimming, walking, running, climbing, digging, and flying. Developmental biologists and palaeontologists have worked vigorously to solve the mysterious origin of paired fins. However, a gaping morphological chasm lies between jawless fishes (which ancestrally lack paired fins) and jawed vertebrates (which possess two sets). Despite this, the question remains one of the foundational cases in the study of morphological novelty---how evolution generates completely new structures. Recent studies in developmental genetics have highlighted evidence that fins and girdles could have formed evolutionarily from a modified gill-supporting bone of an ancient ancestor. This revives a theory from the 19th century which fell out of favour because of a lack of fossil evidence. In this project, we will use the fossil record to document new evidence for the origin of the shoulder and paired pectoral fins of vertebrates from 430-400 million years ago. Underlying this project is the idea that the most critical fossils are not, in fact, absent. Instead, palaeontologists have overlooked crucial intermediate stages hidden in the anatomy of known fossil groups. These fossils show that the throat and gill arches were integral to the origin of the shoulder girdle. Through high-resolution 3D x-ray techniques, we will show that the skulls of jawless fishes near the origin of paired fins reveal precursors stages in the evolution of the head into a distinct skull and shoulder. Next, we will investigate a new finding showing that the oldest jawed fishes possessed a mobile linkage between the head and shoulder initially formed from a modified gill arch. We will use additional 3D techniques of exceptionally preserved fossils to describe how this mobile linkage began as a gill arch. We will then reveal how it became modified into a diverse array of bony joints between the head and shoulder that supported breathing and feeding. Our project will provide crucial insights into how pectoral fins evolved, allowing comparative developmental biologists to identify the genes that led to major evolutionary changes. Furthermore, it ties the origin of the shoulder girdle to profound transformations in the structures used for feeding and respiration during the origin of jaws. This will allow a critical, holistic understanding of how functional and anatomical changes are required across major evolutionary transitions.

成对的鳍是脊椎动物中最重要的解剖学创新之一。这些结构起源于4.3亿年前有颌脊椎动物的祖先，形成了所有脊椎动物四肢的进化基础，包括我们自己的手臂和腿。150多年来，进化生物学家一直对这些结构的起源感到困惑，这些结构产生了一系列令人眼花缭乱的运动适应，如游泳、行走、跑步、攀爬、挖掘和飞行。发育生物学家和古生物学家一直在努力解决成对鳍的神秘起源。然而，在无颌鱼类（祖先没有成对的鳍）和有颌脊椎动物（有两对鳍）之间存在着巨大的形态学鸿沟。尽管如此，这个问题仍然是形态学新颖性研究的基础案例之一——进化如何产生全新的结构。最近的发育遗传学研究表明，鳍和腰带可能是由远古祖先改良过的支撑腮的骨头进化而来的。这使19世纪的一个理论复活，这个理论由于缺乏化石证据而失宠。在这个项目中，我们将使用化石记录来记录4.3 -4亿年前脊椎动物肩膀和成对胸鳍起源的新证据。这个项目背后的想法是，事实上，最关键的化石并没有消失。相反，古生物学家忽略了隐藏在已知化石群解剖结构中的关键中间阶段。这些化石表明，喉弓和鳃弓与肩带的起源是不可分割的。通过高分辨率3D x射线技术，我们将展示无颌鱼的头骨在配对鳍的起源附近，揭示了头部进化成一个独特的头骨和肩膀的前体阶段。接下来，我们将研究一项新的发现，表明最古老的下颚鱼具有头部和肩部之间的移动联系，最初由改良的鳃弓形成。我们将使用额外的3D技术，特别保存化石来描述这种移动连接如何开始作为鳃弓。然后我们将揭示它是如何被改造成头部和肩部之间各种各样的骨关节来支持呼吸和进食的。我们的项目将提供关于胸鳍如何进化的重要见解，使比较发育生物学家能够识别导致重大进化变化的基因。此外，它将肩带的起源与颌骨起源期间用于进食和呼吸的结构的深刻转变联系起来。这将允许一个关键的，全面的理解功能和解剖变化是如何在主要的进化转变中需要的。