For the very first time, scientists have uncovered the remains of an ancient Pacific Ocean whale with four legs. If that doesn't sound strange enough, it also had hooves and an otter-like tail. The find gives us a fresh insight into the bizarre evolutionary history of the world’s largest mammals.
Fifty million years ago, small hooved land mammals no bigger than dogs began to adapt to spending time in water. Over the course of millions of years, these creatures evolved into vast legless mammals with strong flippers and tails, perfectly adapted to life at sea. The final result: modern whales.
Now, scientists have discovered the first evidence that four-legged whales once lived in the Pacific Ocean, telling us more about how these ancient cetaceans spread across the globe. The new species has been named Peregocetus pacificus, which means “the traveling whale that reached the Pacific”.
"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," said Olivier Lambert, of the Royal Belgian Institute of Natural Sciences, in a statement. Whales are thought to have first appeared in South Asia, before dispersing through the world’s seas.
The strange new whale, described as “otter-like”, had little hooves at the tip of its toes and fingers, and hip and limb structures that suggest it could walk. However, it also likely had a webbed tail and feet, which would have propelled it through the water.
During a field excavation to Playa Media Luna, a site in the coastal desert of southern Peru, an international team uncovered the strange animal’s bones. They describe the fossil in the journal Current Biology.
"When digging around the outcropping bones, we quickly realized that this was the skeleton of a quadrupedal whale, with both forelimbs and hind limbs," explained Lambert.
To work out when P. pacificus lived, the researchers analyzed microfossils found in the same sediment layers as the whale. They concluded that the creature lived about 42.6 million years ago, in the middle of an era known as the Eocene.
The whale would have been about 4 meters (13 feet) long, tail included. Perfectly adapted for swimming, its tail bones share similarities with those of beavers and otters – two critters that can both walk on land and glide through water with ease.
The fact that the fossil was found on the western coast of South America supports the idea that early whales headed to the New World via the South Atlantic from Africa’s western coast. Westward surface currents would have helped propel them to their destination, meanwhile the journey across the ocean would have been half as far as it is today. The researchers note that having reached South America, the animals would’ve headed north to colonize North American waters.
The researchers now hope to uncover even more amazing fossils from Peru. “We will keep searching in localities with layers as ancient, and even more ancient, than the ones of Playa Media Luna, so older amphibious cetaceans may be discovered in the future," Lambert said.