EVOLUTION OF MAMMALIAN MIDDLE-EAR
EVOLUTION OF MAMMALIAN MIDDLE-EAR
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DOI：
10.1002/jmor.1051470404
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发表时间：
1975-01-01
影响因子：
1.5
通讯作者：
ALLIN, EF
中科院分区：
文献类型：
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作者：
ALLIN, EF
研究了哺乳动物类爬行动物和早期哺乳动物的下颌骨、悬臂骨和砧骨的结构和进化，试图确定哺乳动物鼓骨、锤骨和砧骨的前体在系统发育中如何、为什么以及何时在接受空气传播的声音中发挥作用。得出以下结论：在哺乳动物系统发育的任何阶段，都可能没有类似于“典型”现存爬行动物的中耳，中耳的后方鼓膜与距骨外相接触。犬齿动物和其他治疗者的鳞状沟，通常被认为有一个长长的外耳道，可能有下颌降肌。在治疗者中，充气室(Westoll的下颌隐窝)延伸到反射的椎板和角状突外侧面的凹陷(外窝)。蝶齿类也有类似的腔室，但翼肌占据了小的外颅窝。下颌窝浅层薄层组织作为鼓膜。在原始阶段，振动主要通过舌骨前角传递到踝骨，但在双齿齿目动物中，振动主要或仅从下颌传到或仅从下颌传到方骨，再传到距骨，反射的舌板是耳鼓的组成部分。在哺乳动物系统发育的治疗阶段，听觉适应是颌骨进化的一个重要方面。随着肌肉从牙后成分转移到牙体，随着牙后成分和方块的减少和松动，听觉效率和对更高声音频率的敏感度得到提高。这些变化是通过相关的修改而实现的，包括牙科的后部扩张。齿突鳞状突关节的建立使这些趋势得以延续，导致了明确的哺乳动物状况，听觉机制没有重大变化，除了大多数哺乳动物(不是单孔目动物)的角度，如鼓膜，最终成为一种非振动结构。
The structure and evolution of the mandible, suspensorium, and stapes of mammal‐like reptiles and early mammals are examined in an attempt to determine how, why, and when in phylogeny the precursors of the mammalian tympanic bone, malleus, and incus (postdentary jaw elements and quadrate) came to function in the reception of air‐borne sound. The following conclusions are reached.It is possible that at no stage in mammalian phylogeny was there a middle ear similar to that of “typical” living reptiles, with a postquadrate tympanic membrane contacted by an extrastapes. The squamosal sulcus of cynodonts and other therapsids, usually thought to have housed a long external acoustic meatus, possibly held a depressor mandibulae muscle.In therapsids an air‐filled chamber (recessus mandibularis of Westoll) extended deep to the reflected lamina and into the depression (external fossa) on the outer aspect of the angular element. A similar chamber was present in sphenacodontids but pterygoideus musculature occupied the small external fossa. The thin tissues superficial to the recessus mandibularis served as eardrum. Primitively, vibrations reached the stapes mainly via the anterior hyoid cornu, but in dicynodonts therocephalians, and cynodonts, vibrations passed mainly or exclusively from mandible to quadrate to stapes and the reflected lamina was a component of the eardrum.In the therapsid phase of mammalian phylogeny, auditory adaptation was an important aspect of jaw evolution. Auditory efficiency, and sensitivity to higher sound frequencies, were enhanced by diminution and loosening of the postdentary elements and quadrate, along with transference of musculature from postdentary elements to the dentary. These changes were made possible by associated modifications, including posterior expansion of the dentary. Establishment of a dentray‐squamosal articulation permitted continuation of these trends, leading to the definitive mammalian condition, with no major change in auditory mechanism except that in most mammals (not monotremes) the angular, as tympanic, eventually became a non‐vibrating structure.