Beyond the Sniffer: Frontal Sinuses in Carnivora

Abstract

Paranasal sinuses are some of the most poorly understood features of mammalian cranial anatomy. They are highly variable in presence and form among species, but their function is not well understood. The bestsupported explanations for the function of sinuses is that they opportunistically fill mechanically unnecessary space, but that in some cases, sinuses in combination with the configuration of the frontal bone may improve skull performance by increasing skull strength and dissipating stresses more evenly. We used CT technology to investigate patterns in frontal sinus size and shape disparity among three families of carnivores: Canidae, Felidae, and Hyaenidae. We provide some of the first quantitative data on sinus morphology for these three families, and employ a novel method to quantify the relationship between three-dimensional sinus shape and skull shape. As expected, frontal sinus size and shape were more strongly correlated with frontal bone size and shape than with the morphology of the skull as a whole. However, sinus morphology was also related to allometric differences among families that are linked to biomechanical function. Our results support the hypothesis that frontal sinuses most often opportunistically fill space that is mechanically unnecessary, and they can facilitate cranial shape changes that reduce stress during feeding. Moreover, we suggest that the ability to form frontal sinuses allows species to modify skull function without compromising the performance of more functionally constrained regions such as the nasal chamber (heat/water conservation, olfaction), and braincase (housing the brain and sensory structures).

Minor contributions of the maxillary sinus to the air-conditioning performance in macaque monkeys

“…Many hypotheses have been proposed based on comparative morphology approaches to explain the physiological or mechanical functions related to the paranasal sinus including the MS, e.g. cooling and regulation of the brain or orbital temperature, reactive reduction of the masticatory load on the cranium, acoustic modifications of nasalized voices, and air conditioning (Shea, 1977;Rae et al, 2003;Rae and Koppe, 2008;Curtis and Van Valkenburgh, 2014;Van Valkenburgh et al, 2014). The paranasal sinus is often thought to reduce the weight of the cranium and save bony materials by eliminating unnecessary bony resources (Rae and Koppe, 2004;Smith et al, 2005;Zollikofer and Weissmann, 2008).…”

Comparative analysis of the shape and size of the middle ear cavity of turtles reveals no correlation with habitat ecology

“…It represents a 3D shape in terms of a sum of 3D sines and cosines on a sphere (Brechb€ uhler et al 1995;Ritchie & Kemp, 1999) and captures details of curvature in more detail than geometric morphometrics (Shen & Makedon, 2006;Shen et al 2009). This method has been applied to studying shape variation in the paranasal sinuses of carnivores (Curtis & Van Valkenburgh, 2014) and the reproductive organs of insects (McPeek et al , 2011, among others.…”

Endocranial shape variation in the squirrel‐related clade and their fossil relatives using 3D geometric morphometrics: contributions of locomotion and phylogeny to brain shape

“…Geometric morphometrics (GM) encompasses a suite of methods for quantifying variation and change in shape (Zelditch, Swiderski & Sheets, ). Three‐Dimensional GM has been employed by paleontologists to examine the relationship between the shape of the bony labyrinth (Grohé et al ., ), cranial (Samuels, ; Samuels & Van Valkenburgh, ; Hautier, Lebrun & Cox, ; Curtis & Van Valkenburgh, ; Lu et al ., ), and postcranial (Milne, Vizcaíno & Fernicola, ) elements in association with variables such as phylogeny and ecology in mammals. Less common has been the use of GM to study cranial endocasts in mammals, although some recent studies have investigated endocranial shape variation within the genus Homo (Bruner, Manzi & Arsuaga, ), among carnivores (Ahrens, ; Iurino et al ., ), and in the species Equus caballus (Danilo et al ., ).…”