Since the Earth's creation 4.5 billion years ago, the planet has been struck by a series of catastrophes, each pushing life to the edge of extinction. Again and again, dinosaurs found themselves victims of these catastrophes, but from each disaster came new life. While a dominant species was wiped out, hardier creatures survived and thrived, moving into the vacuum left by the extinction. In turn, these gigantic creatures took over the planet until they fell victim to another extinction.