The cetacean ear: form, frequency, and evolution

TitleThe cetacean ear: form, frequency, and evolution
Publication TypeBook Chapter
Year of Publication1993
AuthorsKetten, D. R.
EditorsThomas, J. A., R. A. Kastelein, and A. Y. Supin
Book TitleMarine Mammal Sensory Systems
PublisherPlenum Press
CityNew York
Call NumberDRK6788
Keywordsanatomy, auditory system, cochlea, cochlear implants, dolphins, ear, evolution, fossils, inner ear, marine mammals, middle ear, morphology, mysticetes, odontocetes, temporal bones, tympano-periotic bones, tympano-periotic complex

Cetaceans evolved from mesonychid condylarths, a cat-like, heaved carnivore, during the mammalian radiation, an explosive period of species development (Barnes et al., 1985; Lipps and Mitchell, 1976). In the Eocene, an amphibious condylarth entered the shallows of the warm, teeming Tethys Sea and stayed. This ancestral condylarth was equipped with a conventional land mammal ear. In the intervening 50 to 60 million years, auditory evolution paralleled that of the rest of the creature and the ancestral terrestrial ear underwent extraordinary modifications. As cetaceans developed into full, obligate aquatic mammals, unable to move, reproduce, or feed on land. their ears changed into highly effective transducers of water-borne sound. In fact, modern cetacean auditory systems are sufficiently specialized that they may no longer be able to encode air-borne signals.