Like many biologists, the German biologist Oliver Zompro spends thousands of hours looking at specimens of dead animals. He found his first new species when he was twenty. By the age of thirty he had named dozens of wild new forms. While other people around him did crossword puzzles and drank lattes, he explored the world, one animal at a time.

Then, one day, things changed. He was looking through specimens when he found something more interesting than anything he had ever seen before. It was a fossil that looked like a cross between two different kinds of animals. It had the wrong mix of parts. It was--he would come to convince himself--a single individual of an entirely new order of beasts.