Narwhal has the strangest tooth in the sea

By Susan Milius, 13:29 PM May 1, 2014

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Sometimes called the unicorn of the sea, the male narwhal’s tusk is actually a tooth, and it grows directly through the whale’s upper lip instead of pushing the lip aside. It’s an exuberantly large version of a canine tooth that grows in a spiral; the only tooth known to do so. Otherwise narwhals are practically toothless, with only vestigial stubs that stop growing during development and rarely emerge into the mouth.

This extreme anatomy has captivated dentist Martin Nweeia, who...

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