Speaking to the Earth's incredible biodiversity, scientists have discovered that Cetaceans, the infraorder of aquatic mammals that includes a variety of dolphins and whales, originated from a small, four-legged, hoofed ancestor that could walk on land as well as swim.
Found amidst 42.6-million-year-old marine sediments along the coast of Peru, the ancient creature, named Peregocetus pacificus, rewrites the history of what is known about ancient cetaceans. While it was previously known that whales descended from land-based animals like the , these animals all existed in the Atlantic, often near the area now known as Pakistan.
"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," says Olivier Lambert of the Royal Belgian Institute of Natural Sciences, speaking in a .
The origins of the discovery of the four-legged whale date back to 2011, when study co-author Mario Urbina of Museo de Historia Natural-UNMSM, Peru, was part of an international team that discovered P. pacificus, whose name translates from Latin to mean "the traveling whale that reached the Pacific."
"When digging around the outcropping bones, we quickly realized that this was the skeleton of a quadrupedal whale, with both forelimbs and hind limbs," Lambert says. A study regarding the discovery of the creature in the journal Current Biology.
The sediment layers where the skeleton was positioned, known as microfossils, were crucial to determining the quadrupedal whale's age, around 42.6 million years ago. That would place it during the Eocene era, a time with unusually warm waters. Scientists say that "the last time that the Earth experienced a truly greenhouse climate," with heated waters that could offer an advantage to a warm-blooded swimming animal.
Tail included, the P. pacificus was likely around 13 feet (4 meters) long. Details in the skeleton, like the tail, suggest a great maneuverability on both land and sea. Certain parts of the tail call to mind the tails of otters and beavers, meaning that it's likely the tails played a large role in swimming.
Scientists believe that the creatures originated off the western coast of the African continent, and traveled along westward surface currents to reach South America. They were also helped by the fact that the two land masses were only half the distance apart that they are currently.
"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 says. Scientists believe that the ancient land whales could have gotten as far as North America, meaning that the hunt is on once again.