Researchers said that 100 million years ago, Africa's Sahara was the "most dangerous place" in the history of Earth, where "a human time-traveller wouldn't last very long". Reviewing fossils from south-eastern Morocco, they found three of the largest known predatory dinosaurs roamed the area. Among them was the 26-foot-tall sabre-toothed Carcharodontosaurus, which had 8-inch-long serrated teeth.