What is the name of the elongated tooth that forms a narwhal’s tusk?

A narwhal’s tusk is usually an elongated left canine tooth.

The tusk grows from the upper jaw and spirals outward through the animal’s lip. In most narwhals, the left canine develops into the long tusk, which can reach about 3 metres. A smaller right canine may remain embedded, although some males develop two tusks.

The tusk is richly supplied with nerves and contains millions of microscopic channels. Researchers think it may help the narwhal sense changes in the surrounding water, while tusk displays may also play a role in social behaviour and competition between males.

Narwhals are Arctic toothed whales related to belugas. Their tusk is not a horn and is not made from keratin. It is a tooth with a hard outer layer and a living, sensitive interior, making the narwhal one of the most distinctive marine mammals.