The developmental anatomy of the dorsal hindbrain in an elasmobranch fish, Leucoraja erinacea, is described. We focus on the cerebellum, which is a synapomorphy for gnathostomes. Cerebellar development in L. erinacea, a representative of the most basal gnathostome lineage, may be a proxy for the ancestral state of cerebellar development. We also focus on sensory processing regions termed ‘cerebellum-like’ structures due to common anatomical and physiological features with the cerebellum. These structures may be considered generatively homologous if they share common developmental features. To test this hypothesis, the morphological development of the cerebellum and cerebellum-like structures must first be described. Of particular importance is the development of common features, such as the molecular layer, which is the defining characteristic of these structures. The molecular layers of the cerebellum and cerebellum-like structures are supplied with parallel fiber axons from distinct granule cell populations. These are the lateral granule mass, the dorsal granular ridge, the medial granule mass, and the granular eminences of the cerebellum. Cerebellar and cerebellar-like development in L. erinacea is similar to development in other elasmobranchs. The temporal order in which these granule cell populations develop suggests an evolutionary history of duplication or expansion of an existing developmental event.

中文翻译：

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一条elasmobranch鱼（Leucoraja erinacea）背后脑的形态学发育。

描述了一种在弹性支bra鱼（Leucoraja erinacea）中背后脑的发育解剖。我们专注于小脑，这是脑蠕动的突触。erinacea的小脑发育是最基础的gnathostome谱系的代表，可能是小脑发育的祖先状态的代表。由于小脑具有常见的解剖学和生理学特征，我们也将注意力集中在被称为“小脑样”结构的感觉处理区域上。如果这些结构具有共同的发育特征，则可以认为它们是同源的。为了验证该假设，必须首先描述小脑和小脑样结构的形态发展。特别重要的是开发共同特征，例如分子层，这是这些结构的定义特征。小脑和小脑样结构的分子层由来自不同颗粒细胞群的平行纤维轴突提供。这些是外侧颗粒团，背侧颗粒脊，内侧颗粒团和小脑的颗粒隆起。erinacea的小脑和小脑样发育与其他弹性支的发育相似。这些颗粒细胞群发育的时间顺序暗示了现有发育事件的复制或扩展的进化历史。内侧颗粒团和小脑的颗粒隆起。erinacea的小脑和小脑样发育与其他弹性支的发育相似。这些颗粒细胞群发育的时间顺序暗示了现有发育事件的复制或扩展的进化历史。内侧颗粒团和小脑的颗粒隆起。erinacea的小脑和小脑样发育与其他弹性分支的发育相似。这些颗粒细胞群发育的时间顺序暗示了现有发育事件的复制或扩展的进化历史。