Abstract
The evolution of the vertebrate auditory organ was reviewed. In addition to equilibrium and gravitational tasks, sensory epithelia of otolith organ have responded to oscillations of water. The otolith organ such as saccule and lagena evolved into the auditory organ in fish. For terrestrial animals, hearing airborne sounds required the creation of specialized anatomical structures. The middle ear, the periotic canal and the basilar papilla have evolved in the auditory organ of terrestrial animals. In whales, air-adapted auditory organ had to be reorganized to hear water-borne sounds. The pinnae and external auditory canals were lost, and the middle and inner ear capsules fused to form tympano-periotic complex. Sound is conveyed to the middle ear by specialized fatty tissues in the jaw region.
