Department of Life Sciences, Silwood Park Campus, Imperial College London, London, UK.
Shark Measurements, London, UK.
Sci Rep. 2024 May 20;14(1):11471. doi: 10.1038/s41598-024-62004-3.
The neurocranium (braincase) is one of the defining vertebrate characters. Housing the brain and other key sensory organs, articulating with the jaws and contributing to the shape of the anteriormost portion of the body, the braincase is undoubtedly of great functional importance. Through studying relationships between braincase shape and ecology we can gain an improved understanding of form-function relationships in extant and fossil taxa. Elasmobranchii (sharks and rays) represent an important case study of vertebrate braincase diversity as their neurocranium is simplified and somewhat decoupled from other components of the cranium relative to other vertebrates. Little is known about the associations between ecology and braincase shape in this clade. In this study we report patterns of mosaic cranial evolution in Elasmobranchii that differ significantly from those present in other clades. The degree of evolutionary modularity also differs between Selachii and Batoidea. In both cases innovation in the jaw suspension appears to have driven shifts in patterns of integration and modularity, subsequently facilitating ecological diversification. Our results confirm the importance of water depth and biogeography as drivers of elasmobranch cranial diversity and indicate that skeletal articulation between the neurocranium and jaws represents a major constraint upon the evolution of braincase shape in vertebrates.
脑颅（颅腔）是脊椎动物的重要特征之一。脑颅容纳大脑和其他关键感觉器官，与颌骨相连，并对身体最前端的形状有一定影响，因此无疑具有重要的功能意义。通过研究脑颅形状与生态之间的关系，我们可以更好地了解现存和化石生物类群的形态与功能关系。板鳃亚纲（鲨鱼和鳐鱼）是脊椎动物脑颅多样性的一个重要研究案例，因为它们的脑颅相对于其他脊椎动物来说简化了，并且与颅骨的其他部分有些分离。关于这个类群中生态与脑颅形状之间的关联，我们知之甚少。在这项研究中，我们报告了板鳃亚纲中镶嵌式颅部进化的模式，这些模式与其他类群中的模式有显著差异。Selachii 和 Batoidea 之间的进化模块性程度也不同。在这两种情况下，颌骨悬挂系统的创新似乎推动了整合和模块性模式的转变，从而促进了生态多样化。我们的研究结果证实了水深和生物地理学对鲨鱼颅骨多样性的重要性，并表明脑颅形状在脊椎动物中的进化受到神经颅和颌骨之间骨骼连接的限制。
