Preliminary observations on the morphology of the inner ear of the fetal narwhal (Monodon monoceros)

The inner ear of the narwhal (Monodon monoceros) was investigated on the basis of a complete series of microslides of an early fetus. In this well‐preserved specimen, the cochlea is about twice as large as the vestibular apparatus. The latter exhibits a high degree of specialization. Whereas the utriculus and sacculus are of normal size in comparison with those of other mammals, the semicircular canals are miniaturized but not obliterated, as in the case of some adult toothed whales. In comparison with other mammals, there is relatively little perilymphatic space around the vestibular organ, but the inner radius of the lymphatic ducts comes close to that of the adult human. Although there are some hints that the sensitivity of the vestibular system may be high in this species, detailed analysis of the adult narwhal ear is needed to confirm this inference.