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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.
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).
Horns usually have a curved or spiral shape, often with ridges or fluting. In many species, only males have horns. Horns start to grow soon after birth and continue to grow throughout the life of the animal (except in pronghorns, which shed the outer layer annually, but retain the bony core). Partial or deformed horns in livestock are called scurs.
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.
True horns are found mainly among: Ruminant artiodactyls. Antilocapridae ; Bovidae (cattle, goats, antelopes etc.). 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.
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.