The Real Science of Avatar

On Pandora: Thanator
Even the Na'vi don't mess with this rainforest predator, which inspired Sigourney Weaver's character to yell, "Run! Definitely, run!" The Thanator has armored black skin, a massive head covered with red and yellow quills, and — lest you mistake it for a friend — 9-inch teeth.

• In Honor of Earth Day: The Earth from Above