Mauritia, which was located in what is now the Indian Ocean, was a lost island that no person ever saw. That's because it vanished while dinosaurs walked Earth, long before humans existed. So how do we know it was ever there?
The story of Mauritia actually starts with Rodinia, an ancient supercontinent that once included all of the dry land on Earth. About 750 million years ago, Rodinia started to fragment, and one of the pieces that broke loose was Mauritia. It was a quarter of the size of present-day Madagascar.
Mauritia existed for a long time. But 85 million years ago, as Earth's land continued to shift, the microcontinent started to break up. Eventually, it vanished into the ocean.
But pieces of Mauritia may remain, possibly on the floor of the Indian Ocean. There's probably also some of the lost island deep down in Earth, about 6 miles (10 kilometers) below modern Mauritius, a much smaller volcanic island in the Indian Ocean that appeared 9 million years ago. In 2013, scientists who'd analyzed sand from its beaches discovered the presence of minerals that were much, much older — about the age that you'd expect to find in a continental crust. That led them to figure out that Mauritia had once existed [source: Morelle].