Meeting Abstract
Fronto-nasal sinuses are common features in the skulls of many mammals, although their function is unclear. We used micro-CT scanning to analyze the 3D internal anatomy of fronto-nasal sinuses in 12 species across the two independent lineages of Old and New World porcupines (Hystricidae and Erethizontidae). Both lineages have convergently evolved large fronto-nasal sinuses that create a prominent dome shape to the skull, with the sinuses sometimes being comparable in volume to the rest of the cranium. The integuments of these domes are covered in anteriorly projecting quills in erethizontids and highly elongated display quills that form a “crest” in hystricids. The sinuses in most erethizontids are small and maintain a flat shape to the dorsal skull roof. Within this family, two independent evolutions of domed sinuses have occurred in the largest taxa. We found that the hystricid Trichys completely lacks a frontonasal sinus, but the more derived Atherurus contains a small but well defined sinus. Ontogenetic data demonstrates that the sinus in Hystrix africaeaustralis invades the maxilla, parietals, and squamosal bones, creating near full coverage of the dorsolateral cranium with sinuses. Both families demonstrate an evolutionary relationship between fronto-nasal sinus volume and body size, as seen in other mammals. The data herein provide some support for the hypothesis that mammals utilize fronto-nasal sinuses to maintain cranial shape when evolving larger body size, and their existence allows for co-option into novel structural roles. In porcupines, this novel function could be to provide a surface for quill attachment, with anatomical data as yet failing to support a novel physiological role.
