Researchers Dispute Claim That Ancient Whale Was Heaviest Animal Ever

Last August, a team of paleontologists announced that they had discovered the fossilized bones of a gigantic ancient whale. Perucetus, as they named it, might have weighed over 200 tons, which would make it the heaviest animal that has ever lived.

But in a study published Thursday, a pair of scientists have challenged that bold claim. “The numbers don’t make any sense,” said Nicholas Pyenson, a paleontologist at the Smithsonian National Museum of Natural History and one of the authors of the new study.

In their new analysis, Dr. Pyenson and Ryosuke Motani, a paleontologist at the University of California, Davis, concluded that Perucetus probably weighed 60 to 70 tons, which would have made it about the size of a sperm whale.

They also analyzed fossils of blue whales and provided a new estimate of the weight of that species. They concluded that blue whales weigh up to 270 tons — much more than previous estimates, of up to 150 tons — which would make them far and away the heaviest known species in the history of the animal kingdom.

Perucetus first came to light in 2010, when Mario Urbina, a paleontologist at the Museum of Natural History at the National University of San Marcos in Lima, Peru, spotted a bone in a desert in southern Peru. He and his colleagues excavated 13 vertebrae, four ribs, and part of a pelvis.

The bones had many hallmarks of whales’ bones. But they were also astonishingly large and heavy. Dr. Urbina and his colleagues reconstructed the full skeleton of Perucetus by studying the much smaller whales that lived at the same time. They also drew inspiration from living manatees, which have dense skeletons that let them stay underwater to graze on sea grass.