FRONTAL SINUSES IN CARNIVORES

    My dissertation work focused on understanding how shape of hollow cavities inside mammal skulls, known as paranasal sinuses relates to skull function. Paranasal sinuses form when the tissue lining the nasal cavity invades surrounding bones including the maxilla, sphenoid, ethmoid, and frontal sinuses. Little is known about the function of frontal sinuses, which is mostly due to the fact that they are hidden inside of skulls, and were previously inaccessible without use of destructive methods.

 

​    Advanced imaging technologies, such as x-ray computed tomographic (CT) scanning, now make it possible to non-invasively study the skull’s interior. The leading hypothesis to explain the function of sinuses is that they are filling space where bone is mechanically unnecessary. Bone is an expensive tissue for our bodies to maintain, so being able to form sinuses in lieu of maintaining bone may be advantageous for energy conservation.

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    I used CT scans taken from museum specimens to visualize sinuses inside of skulls, and use specialized imaging software to construct volumetric models of sinuses from which I took measurements and provide much needed illustrations of sinus anatomy. To go from a physical museum specimen to an exact digital replica, first the skull is scanned by a CT scanner that produces hundreds of x-ray slices throughout the skull. Next I stack those slices together using specialized computer software, and can fill in the sinuses. Lastly, I can build a model of the original skull with the sinuses filled in, so that I can observe how they vary in size and shape among different species.

 

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    My research showed that there is remarkable diversity in sinus shape and presence among carnivores. Above are a few members of the cat, dog, and hyena families to give an example of how diverse frontal sinuses are among carnivorans. In carnivores, sinus morphology is related to skull size and shape, as well as diet related skull use and ecology, which suggestst that sinuses develop where bone is not structurally necessary.