Narwhal, the Unicorn of the Sea

The legendary narwhal is famous for its unicorn-like single tusk. The narwhal, or narwhale (Monodon monoceros) is the unicorn of the sea.

Photo by Glenn Williams (source)

Photo by Paul Nicklen (source)

These 3,500 lbs (1,600 kg) creatures have two teeth and in the males, the more prominent tooth grows out through the upper lips into a long swordlike, spiralled tusk that can reach 2.5 metres (8.8 feet) in length.

Photo by Paul Nicklen (source)

It is believed by some scientist that the tusk is prominent in mating rituals, perhaps used to impress females or to battle rival suitors.

A newborn narwhal calf. - Photo by Paul Nicklen. (source)

Females occasionally grow a small tusk and males have been seen with two, or none.

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A narwhal skull with double tusks at Natural History Museum, London. - Photo by adem80

Narwhals are inhabitants of Arctic coastal waters and rivers. They are related to bottlenose dolphins, belugas, harbor porpoises, and orcas.

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And here's the video.