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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.
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 only two teeth, one of which forms the tusks in males. Gestation lasts 14–15 months in both species, and almost always results in a single calf.
In particular, the characteristic narwhal 'horn' is anatomically a tooth; the unidentified specimen lacked a single narwhal tusk, but its teeth were spiraled, like the tusk of a narwhal. [ 5 ] [ 3 ] The specimen had 18 teeth, an intermediate number when compared to the beluga (40 teeth) and the narwhal (one tooth).
Horn combs were common in the era before replacement by plastic, and are still made. Horn needle cases and other small boxes, particularly of water buffalo horn, are still made. One occasionally finds horn used as a material in antique snuff boxes. Horn strips for inlaying wood are a traditional technique.
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.
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 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 .
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.