Balrogus

Researchers unearthed a monster in the deeps of South America. It seems this massive creature found its origins in Africa, crossed the smaller Atlantic Ocean -- smaller 70 million years ago -- to crawl up into South America where it settled in the morass of jungles and swamps.

Assuming the asteroid hit the planet and killed the dinosaurs, this guy was unaffected. Somehow surviving the cataclysm that burnt off all the surface of the earth, set fire to the ozone, wiped out all the oxygene and killed everything…except for a couple hundred thousand species of animals and plants. Balrogus shook that off with no problem and continued to hunt and battle for dominance for millions of years.

Only recently discovered and named after Tolkien's monster, this thing might actually deserve the title. It was HUGE! That's an alligator head next to it.