DISSERTATION RESEARCH: The Evolution of Breathing Mechanisms in the Archosauria

论文研究：始祖动物呼吸机制的进化（Dr. Farish Jenkins & Leon claessen）对脊椎动物呼吸系统起源的理解——不同的肺结构和呼吸机制是如何进化的——一直受到化石记录中软组织保存罕见的限制。这个问题可以通过采取一种综合的方法来解决，这种方法既包括对现存动物的观察，也包括对已灭绝物种保存下来的硬组织结构的调查。该项目将重点研究始祖目动物肺通气的进化，始祖目动物包括恐龙、鳄鱼和鸟类。现存的两种始祖动物，鸟类和鳄鱼，表现出明显的、看似独特的呼吸机制。鸟类的肺与非呼吸性气囊相互连接，空气通过固定大小的肺单向“循环”；鳄目动物有双向血流，还有一块辅助肺运动的肌肉。鸟类和鳄鱼的呼吸循环（吸气和呼气）的骨骼运动尚未被详细研究。这项工作将首次尝试将呼吸机制与骨骼特征的详细分析联系起来，特别是那些指示特定运动和限制运动的骨骼特征。这种综合方法代表了最有希望的基础，在此基础上追踪以始祖龙为代表的各种呼吸系统的进化。具体而言，本次调查将：1。通过x线摄影（活体动物的x线记录）分析鸟类和鳄鱼类动物躯干骨骼的呼吸运动学；2. 鉴定和追踪始祖动物化石记录中的骨学特征及其功能含义；3. 在系统发育背景下评估功能和结构数据（即根据从其他证据推断的进化关系）以理解进化模式。

Dissertation Research: Evolutions of Breathing Mechanisms in the Archosauria Dr. Farish Jenkins & Leon ClaessensAn understanding of the origin of vertebrate respiratory systems- how very different lung structures and breathing mechanisms evolved- has been constrained by the rarity of soft-tissue preservation in the fossil record. The problem may be circumvented by taking an integrative approach that employs both observations on living animals and a survey of hard tissue structures preserved in extinct forms. The project will focus on the evolution of lung ventilation in the Archosauria, a group of animals that includes dinosaurs, crocodilians and birds. The two living archosaurian groups, birds and crocodilians, exhibit distinct and seemingly unique respiratory mechanisms. Bird lungs are interconnected with non-respiratory air sacs, and air 'circulates' unidirectionally through lungs of fixed size; crocodilians have two-way flow and an accessory muscle that moves the lungs. The skeletal movements of the respiratory cycle (inhalation and exhalation) in birds and crocodilians have not been studied in detail. This work will represent the first attempt to correlate the mechanics of respiration with a detailed analysis of bony features, especially those that are indicators of specific movements and those that constrain movement. This combined approach represents the most promising basis on which to trace the evolution of diverse respiratory systems that is represented with the Archosauria. Specifically, this investigation will: 1. Analyze the respiratory kinematics of the trunk skeleton of birds and crocodilians through cineradiography (x-ray recording of living animals); 2. Identify and trace osteological (bony) characters and their functional implications within the archosaurian fossil record; 3. Assess the functional and structural data in a phylogenetic context (that is, in terms of evolutionary relationships inferred from other evidence) to understand evolutionary patterns.