That hole is now being filled - thanks to narwhals, medium-size whales, endemic to the Arctic, known as unicorns of the seas because of the single, spiralling tusk found in males.

The narwhal has a single horn (actually a giant protruding tooth) and if unicorns existed in the sea, went the argument in medieval times, surely they also existed on land.

This is why you will never see Lady Gaga riding a unicorn. In fact, she'd be lucky if she got to split a milk shake with a narwhal.