Starck J M
Eberhard-Karls-Universität Tübingen, Zoologisches Institut, Germany.
Adv Anat Embryol Cell Biol. 1995;131:1-137. doi: 10.1007/978-3-642-79592-3.
This study provides new anatomical data, morphometric measurements, and functional hypotheses about the middle ear of paleognathous and a basal neognathous bird. The introduction discusses current theoretical concepts and basic functional approaches in vertebrate morphology. A cautious and somewhat skeptical evaluation of the techniques used, errors made, and personal experience gained in this study forms the background of the interpretation of the structural data. The comparative discussion extracts phylogenetic information from the structural data. The external ear opening of paleognathous species is large and unprotected. The auricular feathers show no structural specialization and provide only incomplete opercularization. No muscles insert into the external ear opening. Special attention has been paid to modifications in the cassowary's skin. The skin of its head has developed cavernous blood sinuses that may be flooded and thus inflate the head during booming display. The external auditory meatus of paleognathous birds is large, bends ventrally, and reaches the tympanic membrane from the ventral side. No peculiarities can be described. The osteology of the tympanic region is described in detail. The fusion of all bony elements and the ossification of connective tissue are important features of the avian middle ear region. The fusion of bone is a necessary prerequisite for extended pneumatization. The ossification of connective tissue, however, complicates morphological description since it deviates from morphologically defined bones. Especially in the neognathous button quail, most of the ventral wall of the middle ear cavity consists of ossified connective tissue; it also includes elements of the extracolumella. The fixation of the eardrum to the bony wall of the tympanic cavity is described in detail. The fixation includes the kinetic quadrate and loose connective tissue in the ventro-lateral part of the middle ear cavity. Movements of the bill must change the tension of the eardrum and thus affect the hearing of birds. The recesses of the middle ear cavity have been investigated using X-ray computed tomography. Using this technique, subsequent three-dimensional reconstruction provides unusual and unique insights into the anatomy of such "nonstructures" as air-filled cavities. It has been shown that three tympanic recesses are a character shared by all birds. Of more functional importance is the interaural pathway provided by the anterior tympanic recess and connecting the contralateral middle ear cavities. This structure is present in all recent and mesozoic birds. It has been suggested that the interaural pathway might function as a sound pressure gradient receptor. Physiological data are controversial but in many cases supportive.(ABSTRACT TRUNCATED AT 400 WORDS)
本研究提供了关于古颚类和一种基部新颚类鸟类中耳的新解剖学数据、形态测量结果及功能假说。引言部分讨论了脊椎动物形态学中的当前理论概念和基本功能研究方法。对本研究中所使用的技术、出现的错误以及所获得的个人经验进行谨慎且略带怀疑的评估，构成了解释结构数据的背景。比较讨论从结构数据中提取系统发育信息。古颚类物种的外耳道开口大且无保护。耳羽无结构特化，仅提供不完全的耳盖作用。没有肌肉插入外耳道开口。对食火鸡皮肤的变化给予了特别关注。其头部皮肤形成了海绵状血窦，在鸣叫展示时可能会充血从而使头部膨胀。古颚类鸟类的外耳道大，向腹侧弯曲，从腹侧到达鼓膜。未发现特殊之处。详细描述了鼓膜区域的骨学特征。所有骨成分的融合以及结缔组织的骨化是鸟类中耳区域的重要特征。骨融合是广泛气腔化的必要前提。然而，结缔组织的骨化使形态学描述变得复杂，因为它偏离了形态学定义的骨骼。特别是在新颚类的纽扣鹌鹑中，中耳腔的大部分腹侧壁由骨化的结缔组织组成；它还包括额外柱骨的成分。详细描述了鼓膜与鼓室骨壁的固定情况。这种固定包括中耳腔腹外侧部分的动方骨和疏松结缔组织。喙的运动必定会改变鼓膜的张力，从而影响鸟类的听力。使用X射线计算机断层扫描对外中耳腔的隐窝进行了研究。利用这项技术，后续的三维重建为诸如气腔等“非结构”的解剖结构提供了不同寻常且独特的见解。研究表明，三个鼓膜隐窝是所有鸟类共有的特征。更具功能重要性的是由前鼓膜隐窝提供的耳间通路，它连接对侧中耳腔。这种结构存在于所有现生鸟类和中生代鸟类中。有人提出耳间通路可能作为声压梯度感受器发挥作用。生理学数据存在争议，但在许多情况下是支持性的。（摘要截取自400字）
