Abstract:
: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 degrees 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.
journal_name
J Morpholjournal_title
Journal of morphologyauthors
Kinkel MD,Thewissen JG,Oelschläger HAdoi
10.1002/jmor.1044keywords:
subject
Has Abstractpub_date
2001-08-01 00:00:00pages
126-31issue
2eissn
0362-2525issn
1097-4687pii
10.1002/jmor.1044journal_volume
249pub_type
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