Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

James V. Remsen


The morphology of the lingual apparatus of three species of sandgrouse (Aves; Pteroclidae) has been described. All biomechanically important parts were included in the description, i.e., all muscles potentially involved in the functioning of the lingual apparatus, all skeletal parts, the salivary glands associated with the lingual apparatus, and the surface morphology of the oropharyngeal cavity. For each muscle its potential functions have been described. In a comparison with data from the literature of three other groups of birds it was found that the functional organization of the lingual apparatus of the sandgrouse is strikingly similar to the one found in plovers and pigeons. However, the functional organization in the chicken differs in several fundamental aspects from that in the other groups. These differences concern particularly those muscles involved in raising the intermandibular region. In the chicken, the M. intermandibularis and M. constrictor colli intermandibularis are connected to each other via a midventral raphe and thereby form a functional unit that raises the intermandibular region. The M. serpihyoideus extends deep to these two muscles and attaches to the basibranchial, thereby becoming a tongue retractor. In the sandgrouse, pigeons, and plovers, however, the M. intermandibularis is connected via a raphe to the M. serpihyoideus whereas the M. constrictor colli intermandibularis remains separate. In these three groups, the M. serpihyoideus is not a tongue retractor, because it has no attachment to the hyoid apparatus. In several other functional units have the sandgrouse, the pigeons, and the plovers also a similar organization, whereas the chicken differs fundamentally. It is suggested that the organization of these functional units represent different functional types. However, a broader survey over a larger number of taxa would have to be undertaken to determine the distribution of these types and to gain an understanding of their evolution.