Institut des Sciences de l'Evolution de Montpellier, département CHANGE, équipe Paléontologie, UMR 5554 Université de Montpellier, CNRS, IRD, EPHE, Place Eugène Bataillon, Montpellier Cedex 5, 34095, France.
Anat Rec (Hoboken). 2023 Nov;306(11):2791-2829. doi: 10.1002/ar.25206. Epub 2023 Apr 5.
Bats form a diverse group of mammals that are highly specialized in active flight and ultrasound echolocation. These specializations rely on adaptations that reflect on their morphoanatomy and have been tentatively linked to brain morphology and volumetry. Despite their small size and fragility, bat crania and natural braincase casts ("endocasts") have been preserved in the fossil record, which allows for investigating brain evolution and inferring paleobiology. Advances in imaging techniques have allowed virtual extraction of internal structures, assuming that the shape of the endocast reflects soft organ morphology. However, there is no direct correspondence between the endocast and internal structures because meninges and vascular tissues mark the inner braincase together with the brain they surround, resulting in a mosaic morphology of the endocast. The hypothesis suggesting that the endocast reflects the brain in terms of both external shape and volume has drastic implications when addressing brain evolution, but it has been rarely discussed. To date, only a single study addressed the correspondence between the brain and braincase in bats. Taking advantage of the advent of imaging techniques, we reviewed the anatomical, neuroanatomical, and angiological literature and compare this knowledge available on bat's braincase anatomy with anatomical observations using a sample of endocranial casts representing most modern bat families. Such comparison allows to propose a Chiroptera-scale nomenclature for future descriptions and comparisons among bat endocasts. Describing the imprints of the tissues surrounding the brain also allows to address to what extent brain features can be blurred or hidden (e.g., hypophysis, epiphysis, colliculi, flocculus). Furthermore, this approach encourages further study to formally test the proposed hypotheses.
蝙蝠是一种多样化的哺乳动物，它们在活跃的飞行和超声回声定位方面高度专业化。这些特化依赖于反映在它们的形态解剖学上的适应性，并且已经被初步与大脑形态和体积联系起来。尽管蝙蝠的颅骨和天然脑壳铸型（“内颅骨”）在化石记录中保存得很小且易碎，但它们允许研究大脑进化并推断古生物学。成像技术的进步允许对内部结构进行虚拟提取，假设内颅骨的形状反映了软组织的形态。然而，内颅骨与内部结构之间没有直接对应关系，因为脑膜和血管组织与它们所包围的大脑一起标记着内颅骨，导致内颅骨的形态呈镶嵌状。内颅骨在外部形状和体积方面反映大脑的假设在研究大脑进化时具有重大影响，但它很少被讨论。迄今为止，只有一项研究涉及蝙蝠的大脑和脑壳之间的对应关系。利用成像技术的出现，我们回顾了解剖学、神经解剖学和血管学文献，并将这些关于蝙蝠脑壳解剖学的知识与使用代表大多数现代蝙蝠科的内颅骨样本进行的解剖学观察进行了比较。这种比较允许为未来的描述和蝙蝠内颅骨之间的比较提出一个翼手目尺度的命名法。描述围绕大脑的组织的印痕也可以说明大脑特征在多大程度上可以模糊或隐藏（例如，脑垂体、松果体、神经节、小脑）。此外，这种方法鼓励进一步研究来正式检验所提出的假设。
