The whale with hooves and a tail

A BIZARRE proto-whale with tiny hooves is raising questions about how whales evolved from land-based animals into creatures that colonised the world’s oceans. The 42.6m-year-old fossilised remains of Peregocetus pacificus have been discovered in Peru—halfway around the world from where these giants are first thought to have appeared, in Asia, some 10m years earlier.

There were only two paths that P. pacificus or its ancestors could have taken to migrate from Asia to South America. It either swam across the Pacific or walked across Africa before swimming across the Atlantic. Both options would have been possible if P. pacificus had been fully adapted to an entirely marine life but this was not the case. The giant had four fully functioning hind limbs, robust enough to carry its weight; each digit was capped with a small hoof.

The specimen was discovered by Olivier Lambert at the Royal Belgian Institute of Natural Sciences. In Current Biology this week, Dr Lambert says his proto-whale had a secret tool at its disposal: a tail. The end of the tail is missing from the fossil, so he cannot say if it featured a fluke that would have helped propel it underwater. But the animal does have vertebrae with strong similarities to those of semiaquatic mammals like otters.

Dr Lambert theorises that ancestors of P. pacificus may have been able to ride Atlantic currents that ran from Africa towards South America. Such a journey would have been hard on an animal that was not entirely sea-worthy but he suspects that the tail would have made the saga survivable. And once arrived at its destination, the benefits of being deposited along a rich coastline with no competition would have been great indeed.

No other quadruped whale has ever been found in South America. And sadly, the singular fossil does not tell if it suffered the loneliness of a sole survivor, or if it found a mate to help populate its new territory.