WASHINGTON (Reuters) – Scientists have discovered fossils of a four-legged whale in the coastal desert of southern Peru, which flourished at sea and on land about 43 million years ago thanks to a discovery that illuminates a crucial step in the early evolution of cetaceans.
The recently discovered calf, Peregocetus, who lived about 43 million years ago, is photographed along the rocky coast of the Southeast Pacific in this undated artistic reconstruction obtained by Reuters on April 3, 2019. Alberto Gennari / Handout via REUTERS
The mammal, 13 meters long (4 meters), named Peregocetus pacificus, represents a crucial intermediate step before whales become fully adapted to a marine life, scientists said Thursday.
His four limbs were able to support his weight on land, which meant that Peregocetus could return to the rocky coast to rest and perhaps give birth while spending much of his time at sea. His feet and his hands had small hooves and were probably webbed to help with swimming. With long fingers and toes and relatively thin limbs, moving on the ground may not have been easy.
Its elongated snout and sturdy teeth – large incisors and canines to grasp, as well as grazing flesh molars – allowed Peregocetus to capture medium-sized prey like fish.
"We think that he was feeding in the water and that his locomotion under water was easier than on dry land," said the paleontologist of the Royal Institute of Natural Sciences from Belgium, Olivier Lambert, who directed the research published in the journal Current Biology.
"Some vertebrae in the tail region share strong similarities with semi-aquatic mammals such as otters, indicating that the tail was primarily used for underwater locomotion," Lambert added.
The origins of the evolution of whales were poorly understood until the 1990s, when fossils of the first whales were discovered. Various fossils have shown that whales evolved just over 50 million years ago in Pakistan and India from terrestrial mammals living in hooves, distantly related to hippopotamuses and the size of whales. a medium sized dog. It took them millions of years to spread around the world.
Peregocetus is the most complete quadruped whale skeleton outside India and Pakistan, and the first known in the Pacific and Southern Hemisphere.
According to Lambert, his presence in Peru suggests that quadruple whales have spread from South Asia to North Africa, then crossed the South Atlantic to reach the New World. Peregocetus shows that the first whales to reach the Americas still retained the ability to move on land.
Over time, the forelimbs of the cetaceans turned into fins. The hind limbs eventually become mere vestiges. It is only about 40 million years ago that the whale line has been transformed into marine animals and then into two groups of live cetaceans: baleen whales and toothed whales, such as dolphins and whales. the orcs.
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Report by Will Dunham; Edited by Sandra Maler