The fossils help to show how cetaceans, including whales, dolphins and porpoises, might have evolved from artiodactyls — even-toed hoofed mammals — some 50 million years ago. The teeth hint that the wading creature still preferred terrestrial plants over fish, indicating that it probably took to water to get away from predators rather than in search of food.

More on this in Nature and a fascinating editorial from Carl Zimmer on The Loom