Evolution of the definitive mammalian middle ear (DMME) as a textbook example in vertebrate evolution has been extensively studied during the last 200 years. Fossils provide the direct evidence on evolutionary stages of the DMME, but because of delicacy of the miniscule ossicles, unequivocal evidence about them has always been rare. Recent work on a stem therian mammal (124 million years old) shows presence of the surangular bone in the basal mammals as a primitive feature and potentially retained in the embryonic stage of some extant mammals. The work also proposed that the DMME and mammalian jaw evolved in a modular fashion. It started as a highly integrated complex in structures and functions, the two modules were regulated by similar developmental genetic mechanisms and eventually decoupled under natural selection so that the physical constraint the two modules imposed on each other was removed, allowing future improvement of each module for better function.

中文翻译：

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制作哺乳动物的耳朵。在白垩纪干哺乳动物的新物种中发现哺乳动物中耳和下颌的模块化解耦

在过去的 200 年中，作为脊椎动物进化教科书示例的最终哺乳动物中耳 (DMME) 的进化得到了广泛的研究。化石提供了关于 DMME 进化阶段的直接证据，但由于微小的听小骨的精致，关于它们的明确证据一直很少见。最近对干兽类哺乳动物（1.24 亿年前）的研究表明，基底哺乳动物中存在 surangular 骨作为原始特征，并可能保留在一些现存哺乳动物的胚胎阶段。这项工作还提出，DMME 和哺乳动物的下巴是以模块化方式进化的。它最初是一个结构和功能高度集成的综合体，