FARKE, A.A.; Stony Brook University, New York: Morphology and Variation of the Frontal Sinuses in Hartebeest (Mammalia: Bovidae)

A sample of ten hartebeest (Alcelaphus buselaphus and A. lichtensteinii) skulls, seven male and three female, were CT scanned in order to examine frontal sinus morphology. The volume of the sinuses averaged 409 ml for males (range of 263 ml to 500 ml) and 205 ml for females (range of 102 ml to 278 ml). Morphology of the sinuses is generally conservative across the sample. The sinus pneumatizes the frontal bone nearly exclusively, and the pedicle supporting the horns is fully pneumatized in both sexes. In all individuals, the sinuses surround the supraorbital canal, leaving the bony margins of the canal intact. The left and right frontal sinuses are separated completely by a bony midline septum, and additional septa may partially divide the left and right sinuses. Overall complexity of the sinuses (i.e., number of septa) is highly variable. No significant differences were detected between males and females, and no correlation exists between sinus complexity and sinus size. The frontal sinus enters the base of the horncores (forming a cornual diverticulum) in only one male; this diverticulum is quite small. The general lack of a cornual diverticulum is surprising, given that the horncores are commonly pneumatized in other bovids (e.g., Bison and Capra). This may offer some evidence against the idea that sinuses opportunistically expand in order to eliminate structurally unnecessary bone from the skull. Under this hypothesis, it might be expected that the horncores should be well pneumatized in Alcelaphus. Other, unknown, factors may be limiting the extent of pneumaticity in this taxon.