Skull evolution and the terrestrialization and radiation of tetrapods

我们的建议汇集了世界级的专业知识和尖端方法来回答生命史上的一个关键问题：脊椎动物是如何征服这片土地的？我们通过检验四个关键假说来解决这个问题，这四个假说源于长期以来的断言，即选择作用于头骨，推动适应在水到陆地过渡期间改善陆地觅食。我们的方法提供了一种方法，可以从类比驱动的进化史断言转向基于机械原理的严格的可验证假说，并将为未来进化生物力学的研究设定基准。在它们历史的头2亿年里，脊椎动物过着水生生活。在3.85亿至3.5亿年前，它们进化出了一系列解剖特征，最终使脊椎动物征服了陆地。这种脊椎动物骨骼的重组创造了基本的四足动物身体规划，即一个统一的头部，活动的脖子、手臂和腿，脚趾和呼吸空气的肺。自那以后，这一计划一直存在，但需要修改，所有陆地脊椎动物都有同样的计划。50多年前有人提出，四足动物通过改变头盖骨和颌部肌肉，创造出一种更强大、更有效的结构，能够有力地咬人，以便在陆地上觅食。这种重组被视为它们随后辐射的关键，使四足动物能够通过以陆生植物、大型猎物和坚硬或坚硬的食物为食，扩展到新的生态位。有人提出，这些修改是以流体动力效率降低和咬合速度变慢为代价的，只能通过失去吸食和肋骨呼吸的进化来实现，从而将头骨从水上运动中解放出来，将猎物吸引到嘴里，将空气输送到肺部。这些想法在教科书中延续了几十年，但基于过时的头骨和下巴闭合肌肉的简单线条图，仍有待检验。我们现在有一个丰富和信息丰富的化石记录，记录了从水到陆地过渡过程中头骨形状的变化。然而，到目前为止，我们一直缺乏以定量、严格的方式检验这些假设的手段。在这项提案中，我们将确定头骨形状和功能的变化如何使脊椎动物能够在陆地环境中觅食，并记录导致它们征服陆地的进化变化和权衡的顺序。我们将结合古生物学和生物学的原理重建14个四足化石的头骨解剖结构。然后，将使用数学和力学原理来检验这一假设，即头骨解剖的变化导致四足头骨从流体力学流线型宽大扁平的头骨进化而来，这些头骨可以快速(但微弱)咬合结实的头骨，从而产生更有效、更有力的咬合。新的进化建模方法将评估对头骨强度或流体动力效率的选择如何影响四足动物头骨的进化。我们的项目将产生方法学上的进步，可以更广泛地应用于进化转变和辐射，并解决长期存在的将形式和功能联系在一起的问题。古生物学家、解剖学家、生物机械学家、进化和发育生物学家和工程师将从这项工作中受益，这将建立新的国际合作。它的视觉方面和对早期四足动物的关注将吸引普通公众，提供参与机会并引起媒体的兴趣。我们团队的成员是开发和验证重建和模拟化石生物体的肌肉骨骼解剖和功能的方法的领导者，并参与开发新的方法来模拟功能如何在深层形成形态。因此，将我们的知识和技能应用于生活史和我们的生活中的关键事件之一的时机已经成熟

Our proposal brings together world class expertise and cutting-edge methods to answer a key question in the history of life: how did vertebrates conquer the land? We address this question by testing four key hypotheses derived from long-standing assertions that selection acted upon the skull to drive adaptations for improved terrestrial feeding during the water to land transition. Our methods offer a means to shift away from analogy-driven assertions of evolutionary history towards rigorous testable hypotheses founded upon mechanical principles, and will set a benchmark for future studies in evolutionary biomechanics. For the first 200 million years of their history, vertebrates lived an aquatic existence. Between 385 and 350 million years ago they evolved a host of anatomical features that ultimately enabled vertebrates to conquer land. This reorganization of the vertebrate skeleton created the basic tetrapod body plan of a consolidated head with mobile neck, arms and legs with digits and air breathing lungs. This plan has persisted, subject to modification, ever since and is shared by all terrestrial vertebrates. It was proposed over 50 years ago that tetrapods modified their skull bones and jaw muscles to create a stronger and 'more efficient' structure, capable of forceful biting for feeding on land. This reorganization is seen as key to their subsequent radiations, enabling tetrapods to expand into new ecological niches by feeding on terrestrial plants, large prey and hard or tough food. It has been proposed that these modifications came at the cost of reduced hydrodynamic efficiency and a slower bite, and could only be achieved by the loss of suction feeding and the evolution of rib-based breathing, thus freeing the skull from its roles in aquatic locomotion, drawing prey into the mouth and pumping air into the lungs.These ideas have been perpetuated in textbooks for decades, yet are based on out-dated simple line drawings of skulls and jaw closing muscles, and remain to be tested. We now have a rich and informative fossil record that documents changes in skull shape across the water to land transition. However, until now, we have lacked the means to test these hypotheses in a quantitative, rigorous way. In this proposal we will determine how changes in skull form and function enabled vertebrates to feed in a terrestrial environment and document the sequence of evolutionary changes and trade-offs that lead to their conquering of land. We will integrate principles from palaeontology and biology to reconstruct skull anatomy in 14 fossil tetrapods. Mathematical and mechanical principles will then be used to test the hypothesis that changes to skull anatomy resulted in tetrapod skulls evolving from hydrodynamically streamlined broad, flat skulls that could deliver a rapid (but weak) bite to strongly built skulls that could produce a more effective, forceful bite. New evolutionary modelling methods will assess how selection for skull strength or hydrodynamic efficiency shaped the evolution of the tetrapod skull. Our project will produce methodological advances that can be applied more broadly to evolutionary transitions and radiations, and to address long standing questions linking form and function. Palaeontologists, anatomists, biomechanists, evolutionary and developmental biologists and engineers will benefit from this work, which will establish new international collaborations. Its visual aspect and focus on early tetrapods will appeal to the general public, offering engagement opportunities and generating media interest. Members of our team are leaders in developing and validating methods for reconstructing and simulating the musculoskeletal anatomy and function of fossil organisms and have been involved in developing new methods for modelling how function has shaped form in deep time. The time is therefore ripe to apply our knowledge and skills to one of the key events in the history of life and our ow