The Dire Wolf, a fierce and powerful alpha predator in the savage ice age, was larger and more powerful than any modern-day wolf. Why did it suddenly perish while the smaller, weaker Gray Wolf survived? Go back in time as National Geographic examines the life and death of the greatest wolf ever to walk the earth.

Weighing up to 750 pounds, the Sabertooth dominated the primal landscape of the Americas for nearly two million years-then suddenly, and mysteriously, went extinct. National Geographic explores the world of the mighty Sabertooth, including how it lived, how it killed, and how it died.

The short-faced bear was twice the size of a grizzly and could outrun a horse. It roamed North America for almost 1 million years-then faded into extinction. See how this mighty creature lived, hunted and vanished.

Megalodon was the biggest predator ever to swim the oceans. And for 20 million years, this ferocious 50-ton shark with a 9-foot jaw and 7-inch serrated teeth terrorized the creatures of the seas. Now, nearly 2 million years after its extinction, a team of scientists is combining research on today's great white with the only Megalodon fossils ever found to unlock the mysteries of this apex predator.

Isolated from the rest of the world for millions of years, South America became home to creatures found nowhere else on Earth-and top of the food chain in this strange land were the aptly named Terror Birds. Capable of killing large prey with a single blow from their massive beaks, these feathered fiends were the only birds ever to become top predators on an entire continent.

Hyaenodon created a reign of terror by just using its head. Its powerful, razor sharp bite could dispatch a prey animal within seconds and left a mark in history that will never be matched.