An artist’s reconstruction of two Peregocetus whales. The presence of a tail fluke remains hypothetical. Image: A Gennari
Showing how little we know about ancient wildlife, scientists have discovered fossilised remains of a four-legged whale with otter-like features.
The family tree of whales charting back many millennia will have to be rewritten again with the discovery of a fossilised ancestor that once climbed the rocky outcrops along the coast of Peru.
Publishing its findings to Current Biology, an international team of researchers from Peru, France, Italy, the Netherlands and Belgium said the creature had four legs and was quite small.
The discovery was made in 42.6m-year-old marine sediment off the Peruvian coast and included the remains of small hooves at the tip of the whale’s fingers and toes – in addition to its hip and limb morphology – all of which suggests it could walk on land.
However, the fact it has a tail and feet with long, webbed appendages means it was a good swimmer, similar to an otter.
Olivier Lambert of the Royal Belgian Institute of Natural Sciences said that this discovery is of huge significance. “This is the first indisputable record of a quadrupedal whale skeleton for the whole Pacific Ocean, probably the oldest for the Americas, and the most complete outside India and Pakistan,” he said.
The international team first arrived at the location in 2011 after it was discovered to be a good site for fossils. During this time, they found the remains of the ancient whale they’ve since named Peregocetus pacifus, meaning ‘the travelling whale that reached the Pacific’.
Anatomical details of the skeleton allowed the team to determine that the creature could manoeuvre its large body – measuring four metres long – with relative ease. For example, features of the caudal vertebrae (in the tail) are reminiscent of those of beavers and otters, suggesting a significant contribution of the tail during swimming.
By calculating it to have existed 42.6m years ago, the team was able to say it strongly supports the hypothesis that early cetaceans reached the ‘New World’ across the South Atlantic, from the western coast of Africa to South America.
Helping them on their travels would have been westward surface currents and the fact that the distance between the two continents would have been half of what it is today. Eventually, having reached South America, the whales would have migrated northward to North America.
