The Avian Lingual and Laryngeal Apparatus Within the Context of the Head and Jaw Apparatus, with Comparisons to the Mammalian Condition: Functional Morphology and Biomechanics of Evaporative Cooling, Feeding, Drinking, and Vocalization

The lingual and laryngeal apparatus are the mobile and active organs within the oral cavity, which serves as a gateway to the respiratory and alimentary systems in terrestrial vertebrates. Both organs play multiple roles in alimentation and vocalization besides respiration, but their structures and functions differ fundamentally in birds and mammals, just as the skull and jaws differ fundamentally in these two vertebrate classes. Furthermore, the movements of the lingual and laryngeal apparatus are interdependent with each other and with the movements of the jaw apparatus in complex and little-understood ways. Therefore, rather than updating the existing numerous reviews of the diversity in lingual morphology of birds, this chapter will concentrate on the functional-morphological interdependences and interactions of the lingual and laryngeal apparatus with each other and with the skull and jaw apparatus. It will: 1. Briefly review the salient features of the mammalian head as a baseline against which to understand the uniqueness of the avian head 2. Describe general morphological features of the lingual and laryngeal apparatus within the context of the skull and jaw apparatus 3. Contrast some fundamental functional-morphological differences that exist among the jaw, lingual and laryngeal apparatus of birds 4. Provide models of the movements of the various parts of the lingual and laryngeal apparatus based on biomechanical analyses 5. Integrate these models with behaviors in thermoregulation, feeding, drinking, and vocalization 6. Briefly demonstrate how detailed morphological and functional analyses can be tested and expanded by using 3D visualization and animation 7. Place the provided data in an evolutionary framework