The evolution of the mammalian jaw during the transition from non‐mammalian synapsids to crown mammals is a key event in vertebrate history and characterised by the gradual reduction of its individual bones into a single element and the concomitant transformation of the jaw joint and its incorporation into the middle ear complex. This osteological transformation is accompanied by a rearrangement and modification of the jaw adductor musculature, which is thought to have allowed the evolution of a more‐efficient masticatory system in comparison to the plesiomorphic synapsid condition. While osteological characters relating to this transition are well documented in the fossil record, the exact arrangement and modifications of the individual adductor muscles during the cynodont–mammaliaform transition have been debated for nearly a century.

中文翻译：

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哺乳动物颌内收肌复合体的形态演变

在从非哺乳动物突触类动物过渡到冠哺乳动物的过程中，哺乳动物颌骨的进化是脊椎动物历史上的一个关键事件，其特征是其个体骨骼逐渐减少为单一元素，并伴随着颌关节的转变及其并入中耳复合体。这种骨学转变伴随着下颌内收肌组织的重新排列和修饰，与拟形突触条件相比，这被认为允许更有效的咀嚼系统的进化。虽然与这种转变有关的骨学特征在化石记录中得到了很好的记录，但近一个世纪以来，人们一直在争论犬齿动物-哺乳动物转变过程中个体内收肌的确切排列和变化。