CLIFFORD, A.B.*; WITMER, L.M.: The Narial Anatomy of Hooded Seals (Cystophora cristata) with Respect to other Carnivora.

Male hooded seals (Phocidae: Cystophora cristata) have two inflatable devices, both of which involve modification of their narial and facial anatomy. 1) An inflatable integumentary bladder is formed as the elastic and hairy epithelium covering the narial region is inflated following closure of both nostrils. 2) The “red bladder” is formed as a highly elastic portion of the nasal septal mucosa is extruded out one nostril with the contralateral nostril shut. Both devices are used as visual displays, the first year round and the second during the mating season. The unique narial anatomy of adult male hooded seals was studied via CT scanning, dissection, and skeletonization of fresh heads. Comparisons involved similar studies of adult female and juvenile hooded seals, and adults of bearded seals, black bear, and coyote; skulls of other phocid and otariid species were examined. Among the anatomical specializations associated with this functional complex are expansion of the nasal vestibule, retraction of the bony naris, increased elasticity in the narial skin and membranous nasal septum, transformation of the nasal cartilages, elaboration of certain facial muscles that are inconspicuous in outgroups, and changes in numerous bony features. Adult female and juvenile hooded seals are skeletally more like adult males but the associated soft tissues are less developed. Oddly, the mechanism of nostril closure remains enigmatic. The functional anatomy of the hood is important in that it is the nominative attribute of the species; moreover, it has bearing on the general evolution of probosces in mammals and even on inferences of similar inflatable narial structures in extinct taxa such as hadrosaurian dinosaurs.