Narwhal (Monodon monoceros)
The narwhal is a marine mammal that is most closely related to beluga whales. These creatures are classed as near threatened due to hunting and climate change, but the data was insufficient to make population assessments until very recently, highlighting the need for research on them.
Their characteristic tusk is thought to have evolved as a secondary sexual characteristic as narwhals do not appear to use them for fighting or breaking Arctic ice. Because of its similarity to that of the mythical unicorn, the tusk was said to have magic powers in medieval times, allegedly curing victims of poisoning.