We report a new Cretaceous multituberculate mammal with 3D auditory bones preserved. Along with other fossil and extant mammals, the unequivocal auditory bones display features potentially representing ancestral phenotypes of the mammalian middle ear. These phenotypes show that the ectotympanic and the malleus-incus complex changed notably during their retreating from the dentary at various evolutionary stages and suggest convergent evolution of some features to extant mammals. In contrast, the incudomalleolar joint was conservative in having a braced hinge configuration, which narrows the morphological gap between the quadroarticular jaw joint of non-mammalian cynodonts and the incudomalleolar articulations of extant mammals. The saddle-shaped and abutting malleus-incus complexes in therians and monotremes, respectively, could have evolved from the braced hinge joint independently. The evolutionary changes recorded in the Mesozoic mammals are largely consistent with the middle ear morphogenesis during the ontogeny of extant mammals, supporting the relation between evolution and development.

中文翻译：

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基于早白垩世热河哺乳动物探索哺乳动物中耳的祖先表型和进化发育


我们报告了一种新的白垩纪多瘤哺乳动物，保留了 3D 听觉骨骼。与其他化石和现存哺乳动物一样，明确的听骨显示出可能代表哺乳动物中耳祖先表型的特征。这些表型表明，外鼓室和锤骨-砧骨复合体在各个进化阶段从齿骨撤退的过程中发生了显着变化，并表明某些特征与现存哺乳动物的趋同进化。相比之下，顶踝关节在具有支撑铰链配置方面是保守的，这缩小了非哺乳动物犬齿兽的四关节颌关节与现存哺乳动物的顶踝关节之间的形态差距。兽类和单孔类动物的马鞍形和邻接锤骨-砧骨复合体可能是从支撑铰链关节独立进化而来的。中生代哺乳动物记录的进化变化与现存哺乳动物个体发育过程中的中耳形态发生基本一致，支持了进化与发育之间的关系。