Indonyus belongs to an ancient order of mammals that had two or four toes on each foot. Modern day representatives of the group include camels, pigs, and hippopotamuses.

The stable-oxygen-isotope composition of its teeth suggest that the animal spent much of its time in water.

Some have assumed that the ancestor of whales first took to the water to feed on fish but the latest evidence suggests otherwise.

"The new model is that initially they were small deer-like animals that took to the water to avoid predators," Professor Thewissen told BBC News. "Then they started living in water, and then they switched their diet to become carnivores."

Although the behaviour and habits of Indohyus appear somewhat strange, there is a modern day parallel in the African mousedeer (chevrotain).