| Sound transmission in archaic and modern whales: anatomical adaptations for underwater hearing. | |
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MedLine Citation:
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PMID: 17516434 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The whale ear, initially designed for hearing in air, became adapted for hearing underwater in less than ten million years of evolution. This study describes the evolution of underwater hearing in cetaceans, focusing on changes in sound transmission mechanisms. Measurements were made on 60 fossils of whole or partial skulls, isolated tympanics, middle ear ossicles, and mandibles from all six archaeocete families. Fossil data were compared with data on two families of modern mysticete whales and nine families of modern odontocete cetaceans, as well as five families of noncetacean mammals. Results show that the outer ear pinna and external auditory meatus were functionally replaced by the mandible and the mandibular fat pad, which posteriorly contacts the tympanic plate, the lateral wall of the bulla. Changes in the ear include thickening of the tympanic bulla medially, isolation of the tympanoperiotic complex by means of air sinuses, functional replacement of the tympanic membrane by a bony plate, and changes in ossicle shapes and orientation. Pakicetids, the earliest archaeocetes, had a land mammal ear for hearing in air, and used bone conduction underwater, aided by the heavy tympanic bulla. Remingtonocetids and protocetids were the first to display a genuine underwater ear where sound reached the inner ear through the mandibular fat pad, the tympanic plate, and the middle ear ossicles. Basilosaurids and dorudontids showed further aquatic adaptations of the ossicular chain and the acoustic isolation of the ear complex from the skull. The land mammal ear and the generalized modern whale ear are evolutionarily stable configurations, two ends of a process where the cetacean mandible might have been a keystone character. |
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Authors:
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Sirpa Nummela; J G M Thewissen; Sunil Bajpai; Taseer Hussain; Kishor Kumar |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Anatomical record (Hoboken, N.J. : 2007) Volume: 290 ISSN: 1932-8486 ISO Abbreviation: Anat Rec (Hoboken) Publication Date: 2007 Jun |
Date Detail:
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Created Date: 2007-05-28 Completed Date: 2007-07-03 Revised Date: 2009-12-16 |
Medline Journal Info:
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Nlm Unique ID: 101292775 Medline TA: Anat Rec (Hoboken) Country: United States |
Other Details:
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Languages: eng Pagination: 716-33 Citation Subset: IM |
Copyright Information:
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2007 Wiley-Liss, Inc. |
Affiliation:
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Department of Anatomy, Northeastern Ohio Universities College of Medicine, Rootstown, Ohio, USA. snummela@fastmail.fm |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adaptation, Physiological* Animals Ear* / anatomy & histology, physiology Evolution Fossils Hearing / physiology* Phonetics Sound Water Whales* / anatomy & histology, physiology |
| Chemical | |
Reg. No./Substance:
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7732-18-5/Water |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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