Contribution to knowledge of the development and comparative morphogenesis of the nasal apparatus of the white pelican Pelecanus onocrotalus L. (Morphogenesis of the nasal capsule, the nasal epithelial tube and the organ of Jacobson in Sauropsida XII)
Slabý, O.
Folia Morphologica 33(1): 63-69
1985
ISSN/ISBN: 0015-5640 PMID: 3988177 Document Number: 248551
The question of the extent to which a highly adapted structure like the avian skull can develop still further is resolved in an advanced pelican (P. onocrotalus L.) embryo. Only quantitative developmental changes of a reduction type take place. The vestibule is atypical and short, so that paradoxically, it resembles more primitive conditions in reptiles, and the atrioturbinal is rudimentary. The input of the vestibule into the main cavity is simple and takes the form of a straightforward transition in a rostrocaudal direction. The choanal system is strikingly roomy. The concha, the aulax and the maxilloturbinal are rudimentary. Reduction thus occurs in both the olfactory and the respiratory region, but here it is compensated by marked development of the choanal systems; this is no doubt associated with obliteration of the nostril in Steganopodes. In the caudal parts the nasal capsule has a floor acting as a support for the spacious choanal system and forming a kind of ectochoanal cartilage. This morphogenesis of the nasal apparatus is compared with the development of the likewise reduced nasal apparatus of Phalacrocorax carbo L.