Marine Mammals - Chapter 8 - Part II Cetaceans, Sirenians,...

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Chapter 8 - Part II Cetaceans, Sirenians, and Others
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The Cetaceans The Skull: Telescoped Has altered the size, shape, and relationship of many skull bones External narial opening migrated to dorsal position Braincase shortened Modifications in the maxilla in mysticetes and in both premaxilla and maxilla in odontocetes
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The skull: Odontocetes display asymmetry in cranial and facial bones (structures on right side larger than on left). Right side for sound production Left side adapted for respiration Odontocete skull variously ornamented River dolphins Beluga
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The Skull: Rostrum of odontocetes made of dense bone: Acoutic-related function Similar in compostion to tympanic bulla Mysticete skull has expanded facial region and an arched rostrum to accommodate the baleen plates. Greatly arched in balaenids.
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The Skull: All mysticetes have two unbranched nasal passages to paired blowholes. Odontocetes have a single nasal passage except the sperm whale which has two.
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The Skull: Odontocete facial structures complex. Perhaps for buoyancy control during dives. Ramming structures. Principal functions are feeding, respiration, and sound production and reception. Nasal plugs occlude bony nares and are used in respiration and sound production.
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The Skull: Large ovoid melon in facial region (8.17). Positioned off the the right side. Rests on pad of dense connective tissue on top of the bony rostrum of the skull. Melon and mandibular lipid tissues involved in sound production and reception Isovaleric acid Differences in biochemical of lipids of different ages of sperm whales » Echolocation not fully developed at birth?
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The Skull: Primitive vestigial melon in baleen whales. Original function was involved in respiration? Primitive ancestors could echolocate?
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The Skull: Sperm whales have spermaceti organ 30% of whale’s total length. 20% of its weight.
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This note was uploaded on 10/13/2008 for the course BIOL 4865 taught by Professor X during the Spring '08 term at University of New Brunswick.

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Marine Mammals - Chapter 8 - Part II Cetaceans, Sirenians,...

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