It has long been suggested that the widely spaced nostrils of sphyrnid sharks may provide them with better directional localization of odors. We have compared the olfactory system morphology of sphyrnid sharks to their closely related carcharhinid relatives to see if this hypothesis is supported.

Most sphyrnid sharks possess a distinct prenarial groove on the anterior edge of the cephalofoil that serves to channel water from along the length of the groove into the nostrils. This effectively increases the swath of water that is sampled by the head of the sphyrnid sharks providing them with a higher probability of encountering an odor molecule. However, because odor is channeled from anywhere along the length of the prenarial groove, the effective separation distance between left and right sides is no different than in a carcharhinid shark.

The surface area of the lamellae that comprise the olfactory rosette was compared among sphyrnid and carcharhinid sharks. Although sphyrnids have a greater number of individual lamellae, the total surface area does not differ from the carcharhinids. The dorso-ventrally compressed cephalofoil of sphyrnids constrains the size of the rosette although the greater head width enables them to possess a greater number of smaller lamellae.