The tusk of a narwhal is actually a long tooth that has grown beyond the jawline, erupting from the head of the animal and growing up to 9 feet (2.7 m). Like the teeth of other mammals, the tusk/tooth is made of ivory.
Known as the “Sea Unicorn” and “Unicorn of the Ocean” and just about any other unicorn allusion, the Narwhal (Monodon monoceros) is famous for it’s long, protruding tooth that appears to be a tusk or horn. The narwhal only has two teeth. In females, neither tooth extends beyond the gumline. In males, however, the right tooth will typically remain embedded in the gum, but the left tooth will grow and extend out of the mouth in a spiral that can be up to 9 feet long (2.7 m). Occassionally the second tooth will grow beyond the jawline, and it isn’t uncommon to find a narwhal with two tusks, though they are rare.