BOVINI, Gray, 1821

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 : 1000-1002

BOVINI

All bovines have relatively large frontal sinuses, differing somewhat in their extent and complexity.

Bison bison

The frontal sinuses ( Fig. 6C, D ) pneumatize the entire frontal bone in this taxon, as well as the entire parietal. The sinus extends immediately up to the suture between the squamous temporal and the parietal. The occipital receives a pneumatic diverticulum from the parietal portion of the frontal sinus in some specimens, although most of this bone remains unpneumatized in ontogenetically younger specimens (YPM 9022, as determined by sutural fusion and tooth wear). In the oldest specimens (YPM 9023, as indicated by the degree of sutural fusion and tooth wear), the frontal sinus extends up to the foramen magnum and the base of the paroccipital process, but not into the occipital condyles. The midline strut may be heavily remodelled and indistinct caudally. This condition is apparently associated with fusion of the interfrontal suture. No distinct supraorbital strut exists beyond the immediate area of the supraorbital canal. The sinus extends to the distal tip of the horncores in the specimens examined here, and is heavily strutted throughout.

Bos javanicus

The extent and morphology of the sinuses in this taxon are quite similar to those seen in Bison bison . The occipital sutures were not fused completely in the specimen that was studied here (AMNH 113755, although it did have complete eruption of the third molar), indicating that the supraoccipital, but not the exoccipital portion of the occipital bone, was pneumatized in this individual.

Bubalus

Bubalus depressicornis ( Fig. 6A, B ) and Bubalus mindorensis both have frontal sinuses of variable extent, possibly depending on age. The supraorbital canal is entirely enclosed by bone, but the supraorbital strut is not traceable for a great distance before it merges with a number of other, unrelated struts. Variability was seen in the pneumatization of the parietal and the extent of the pneumatization of the horncore in Bubalus mindorensis . In one specimen (AMNH 40046), only the basal portion of the horncore was pneumatized, and the sinus did not cross the frontoparietal suture into the parietal. In the other specimen (AMNH 99339), over two-thirds of the length of the horncore and the rostralmost portion of the parietal were pneumatized. The frontoparietal suture was somewhat less distinct in the latter specimen, as visualized through CT and on the original specimen. In Bubalus depressicornis , the sinus extended right up to the suture ( Fig. 6A ), but did not pneumatize the parietal in either of the specimens observed here.

Syncerus caffer

The frontal sinuses are quite extensive in this taxon, pneumatizing the parietal and potentially the occipital (the sutures were nearly completely fused on the specimen examined here, so it cannot be determined for certain). The basal third of the horncores are pneumatized. The midline strut remains sharply defined along most of its length, up until the former location of the frontoparietal suture. A distinct, enclosed supraorbital canal is present, but a discrete supraorbital strut cannot be identified because of the abundance of other struts within the sinus.

Figures

Figure 6. Digital reconstructions from computed tomography (CT) scan data of the skulls of Bubalus depressicornis (A–B; AMNH 152684), Bison bison (C–D; YPM 9023), and Budorcas taxicolor (E–F; AMNH 110476), illustrating frontal sinuses and related anatomy. Skulls are shown in lateral (B, C, E) and dorsal (A, D, F) 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 horns have been truncated in C–F. Scale bars: 5 cm.