(CN) – The ancient ancestors of whales and dolphins once had four hoof-shod legs, according to a new study published Thursday.
Researchers found a four-legged whale in marine sediments in Peru that date back 42.3 million years, providing insight into the evolutionary antecedents of the marine mammals and their dispersal throughout the ancient world.
"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.
Most biologists hold that cetaceans, which include dolphins, whales and other marine mammals, originated in South Asia more than 50 million years ago and evolved from a small quadrupedal animal with hooves.
The whale found in Peru boasted hooves at the tips of its fingers and toes, and its leg and hip morphology suggested it was capable of walking on land. Yet, the creature also had long appendages at the tail and feet, similar to that of otters, that suggested it could swim adeptly as well.
The findings are published in the scientific journal Current Biology.
The discovery of the intact skeleton goes in large part to Mario Urbina of the Museo de Historia Natural in Peru, who first discovered the Playa Media Luna — a desert area close to the Pacific coast Urbina thought would be ideal for fossil hunting.
In 2011, Urbina and an international team of biologists went on a field expedition to the area, eventually leading to the excavation of the remains of an ancient whale since named Peregocetus pacificus. It means "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 said.
The team also used other fossil remnants found in the area to help date the skeleton at approximately 42 million years old, which means the creature roamed on land and sea during the middle Eocene.
The skeleton measured in at about 12 feet long. Several anatomical details indicated the creature was amphibious.
For instance, the vertebrae in the tail had similar features to that of the sea otter or a beaver, suggesting it used its tail to help propel it in the water.
Regarding the discovery and its pertinence to the creature’s dispersal along the ancient world, researchers say the combination of the geological era in which the creature lived and its discovery along the western coast of South America demonstrate that early cetaceans reached the Americas via the South Atlantic.
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