[Cranial morphology of an American siphonopid, Microcaecilia unicolor (Amphibia, Gymnophiona) and its functional interpretation].

The skull of Microcaecilia unicolor, american Siphonopidae (Amphibia, Gymnophiona), shows 3 notable morphological characteristics: The mandibular shortening, the verticalization of the retroarticular process, and the verticalization of the quadrate. They define a peculiar morphofunctional pattern, which seems to exist in dwarf forms moving in the complex root system of trees. These morphological characters, associated with modifications of the muscle depressor mandibulae, give functional advantages: A wider gaping of the mouth and the ability of the ingestion of preys which have a great cross-section. In keeping its macrophageous habits, Microcaecilia unicolor does not compete with other dwarf vertebrates living in the same environment and feeding on microinvertebrates.