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The narwhal is a stocky cetacean with a relatively blunt snout, a large melon, and a shallow ridge in place of a dorsal fin. Males of this species have a large (1.5–3.0 m (4 ft 11 in – 9 ft 10 in)) long tusk, which is a protruding left canine thought to function as a weapon, a tool for feeding, in attracting mates or sensing water salinity.
Belugas can be found in the far north of the Atlantic and Pacific Oceans; the distribution of narwhals is restricted to the Arctic and Atlantic Oceans. Monodontids have a wide-ranging carnivorous diet, feeding on fish, molluscs, and small crustaceans. They have reduced teeth, with the beluga having numerous simple teeth, and the narwhal having ...
The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear.The adult human ear canal extends from the auricle to the eardrum and is about 2.5 centimetres (1 in) in length and 0.7 centimetres (0.3 in) in diameter.
The evolution of the mammalian middle ear appears to have occurred in two steps. A partial middle ear formed by the departure of postdentary bones from the dentary, and happened independently in the ancestors of monotremes and therians. The second step was the transition to a definite mammalian middle ear, and evolved independently at least ...
The ear canal of the outer ear is separated from the air-filled tympanic cavity of the middle ear by the eardrum. The middle ear contains the three small bones—the ossicles —involved in the transmission of sound, and is connected to the throat at the nasopharynx , via the pharyngeal opening of the Eustachian tube .
The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear). The mammalian middle ear contains three ossicles (malleus, incus, and stapes), which transfer the vibrations of the eardrum into waves in the fluid and membranes of the inner ear .
Giraffidae: Giraffids have a pair of skin covered bony bumps on their heads, called ossicones. Cervidae: Most deer have antlers, which are not true horns due to lacking a bone core and made of keratin. Rhinocerotidae: The "horns" of rhinos are made of keratin and lack a bone core.
Narwhal or Nostril whale (Monodon monoceros). Melville writes at length about this whale, which at the time was a well-known denizen of the polar seas. He describes the horn of the narwhal and speculates on its purpose. According to Melville, it is also known as the tusked whale, horned whale and the unicorn whale.