"What would you get if you crossed a whale with a shark?" asks Sid Perkins. "Maybe something like Leviathan melvillei, a long-extinct, hypercarnivorous whale with teeth longer than any T. rex ever had." The mammal is a newly described sperm whale that lived between 12 million and 13 million years ago, according to Olivier Lambert, a vertebrate paleontologist at the National Museum of Natural History in Paris.