title: Morphology of the interorbital region of Saimiri sciureus.
abstract: The skull of the platyrrhine primate Saimiri sciureus is distinguished by a large interorbital fenestra. Juvenile skulls still show a bony interorbital septum with some small gaps. A morphogenetic study was undertaken to better understand the structures of the interorbital region, which represents a linkage between the base of the braincase and the nasal skeleton. Already in early ontogenetic stages a reduction of the posterior portion of the nasal capsule and of the cartilaginous interorbital septum are observed, resulting in the formation of a primary interorbital fenestra. A bony interorbital septum is mainly formed in perinatal age stages by ossification of the presphenoid and by medial fusion of the frontals; the primary interorbital fenestra is retained as a small opening. It only occurs in late juvenile stages when the definitive interorbital fenestra develops by by secondary transformation of bone into a membrane of dense connective tissue; this process is most probably caused by mechanical friction of the very closely approximated eyes of both sides.
mesh_terms: D000818:Animals; D002144:Callithrix / Q000033:anatomy & histology; D002427:Cebidae / Q000033:anatomy & histology*; D002428:Cebus / Q000033:anatomy & histology; D005333:Fetus / Q000033:anatomy & histology; D009300:Nasal Septum / Q000033:anatomy & histology; D009915:Orbit / Q000033:anatomy & histology; D010012:Osteogenesis; D012453:Saimiri / Q000033:anatomy & histology*; D012886:Skull / Q000033:anatomy & histology* / Q000254:growth & development