Around 50 million years ago, modern-day New Zealand, Australia, South America, and Antarctica were part of a large, forested supercontinent called Gondwana. Temperatures exceeded the modern-day climate by more than 53 degrees Fahrenheit, supporting warm-adapted species of crocodiles, land turtles, and several types of bird. (Read: "Antarctica Was Once Covered in Forests. We Just Found One That Fossilized.")

On a section of what would later become New Zealand's South Island, an ecosystem of these diverse species clustered around the prehistoric Lake Manuherikia. In an area about the size of Prince Edward Island, they thrived for generations. But, as temperatures cooled and dried out the landmass, the flora and fauna began to die off. (Read more about ancient