51.3 Saturday, Jan. 5 Evolution of the Frontal Sinuses in Bovidae FARKE, A.A.; Stony Brook Univ., New York email@example.com
Cranial pneumaticity is remarkably homoplastic, with independent pneumatization of some cranial bones occurring multiple times across mammals. The factors that drive pneumatization are unclear, however. Bovids, a clade of horned artiodactyls including sheep, goats, and cattle, present diverse frontal sinus morphologies and thus provide an ideal group in which to examine the evolution of cranial pneumaticity. In this preliminary study, frontal sinus volumes and other cranial metrics were quantified from cranial CT scans of 33 bovid species representing a range of phylogenetic, behavioral, and morphological diversity. Significant variation was seen in the extent of the frontal sinus, ranging from complete absence (cephalophines and Tragelaphus scriptus), to a frontal recess without significant pneumatization of the frontal (Oreotragus oreotragus, Pelea capreolus, Redunca fulvorufula, and Taurotragus oryx), to a large frontal sinus (all other bovids examined; e.g., Bison bison, Gazella thomsonii, Alcelaphus buselaphus). Phylogenetic mapping of characters suggests that the common ancestor of extant bovids had a frontal sinus, with independent losses having evolved in several clades. Phylogenetically independent contrasts were used to evaluate the relationships between several cranial variables and frontal sinus size. Statistically significant (p<0.05) correlations were observed between frontal sinus volume and horn size (r2=0.51), skull size (r2=0.64) and frontal size (r2=0.80), and a significant, but weak, correlation was observed between sinus volume and cranial ramming behavior (r2=0.23). These results suggest that both phylogeny and the morphology of the surrounding bones most strongly influence the presence and morphology of cranial sinuses.