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Rotation of middle ear ossicles during cetacean development
Author(s) -
Kinkel M.D.,
Thewissen J.G.M.,
Oelschläger H.A.
Publication year - 2001
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1044
Subject(s) - malleus , incus , ossicles , biology , middle ear , anatomy , ear ossicles , stapes
Cetacean middle ears are unique among mammals in that they have an elongated tympanic membrane, a greatly reduced manubrium mallei, and an incudal crus longum that is shorter than the crus breve. Elongation of the tympanic membrane and reduction of the manubrium is thought to be related to an evolutionary rotation of the incus and malleus out of the plane of the tympanic membrane. We examined if rotation also occurs during ontogeny by comparing the middle ears of two species of dolphins ( Delphinus delphis, Stenella attenuata ) at different stages of development. We observed that: the incus has the body and crural proportions as in terrestrial mammals early in development; the incudomallear complex rotates approximately 90° following ossification; the tympanic membrane is not elongated until relatively late in development. Therefore, some of the unique characteristics of the cetacean middle ear develop as modifications of an initially terrestrial‐like morphology. J. Morphol. 249:126–131, 2001. © 2001 Wiley‐Liss, Inc.