TRAGELAPHINI, Blyth, 1863

Farke, Andrew A., 2010, Evolution and functional morphology of the frontal sinuses in Bovidae (Mammalia: Artiodactyla), and implications for the evolution of cranial pneumaticity, Zoological Journal of the Linnean Society 159 (4), pp. 988-1014 : 1005

TRAGELAPHINI

Of the three taxa examined from this clade, only one displayed evidence of a true frontal sinus ( Taurotragus oryx ; Fig. 9A, B ). In this taxon, the frontal sinus is extremely restricted in size and extent. It originates from a large recess in the caudodorsal portion of the nasal cavity, is bordered by a distinct bony wall, and excavates a small volume of trabecular bone. The sinus does not extend to even the rostral border of the supraorbital canal, and is situated medial to the parasagittal plane containing the canal. The right and left sinuses do not meet along the midline. Tragelaphus strepsiceros shows a small recess in the equivalent region, but Tragelaphus scriptus lacks even this feature.

Tragelaphines are unique in the presence of a separate ‘cornual sinus’ within the very base of the horncores, extending only as far forward as the caudal margin of the orbits. All individuals of all three taxa examined for this study preserved this feature, which was observed both in CT scans and in sectioned horns. This sinus is not connected to the nasal cavities, and thus was almost certainly not pneumatic in origin. Instead, it may have been filled with fat or marrow in life. Rostrally, the cavities are lined by relatively smooth bone, but the bone surface becomes trabecular towards the caudal end. This contrasts sharply with the completely smooth bone lining of the pneumatic frontal sinus in other bovids.

Figures

Figure 9. Digital reconstructions from CT scan data of the skulls of Taurotragus oryx (A–B; YPM 10471), Aepyceros melampus (C–D; YPM 9597), Oreotragus oreotragus (E–F; AMNH 27827), and Pantholops hodgsonii (G–H; AMNH 55819), illustrating frontal sinuses and related anatomy. Skulls are shown in lateral (A, C, E, G) and dorsal (B, D, F, H) views. The boxed areas indicate the region of the skull that has been rendered partially transparent in order to visualize the anatomy of the frontal sinuses. The horn sheaths have not been rendered in A and B, and they are truncated in C–H. Scale bars: 5 cm.