This Massive Extinct Whale May Be the Heaviest Animal That Ever Lived

The newly discovered behemoth could unseat the blue whale for the title, but scientists can only make educated guesses about its weight

Drawing of very round, elongated whale beneath the waves, next to a much smaller swimming creature
An artist's interpretation of what Perucetus colossus would have looked like when it lived some 38 million years ago Alberto Gennari

The world has a new contender for the heaviest animal that ever lived: a whale that swam the oceans some 38 million years ago and likely weighed almost 400,000 pounds.

Scientists described the newly discovered extinct species, named Perucetus colossus, in a paper published Wednesday in the journal Nature. Based on their weight estimate of 180 metric tons, P. colossus would unseat the endangered blue whale, which has been the longstanding record-holder for the world’s heaviest creature. Still, determining an animal’s weight based solely on its fossilized remains is tricky, so not all scientists are ready to hand over the title just yet.

For reference, the gigantic creature likely weighed more than 30 African elephants combined, or about 5,000 people, as study co-author Giovanni Bianucci, a paleontologist at the University of Pisa in Italy, tells CNN’s Kristen Rogers.

Researchers gleaned as much as they could about P. colossus from studying fossilized bones found in the Ica valley of southern Peru. In total, paleontologists uncovered 13 vertebrae, four ribs and part of a pelvis from an area known as the Pisco Formation.

One reason for P. colossus’ heaviness was its bones, which were extremely dense—so dense that, when paleontologists first discovered them, they weren’t even sure that they were bones at all. The fossils looked more like rocks than anything.

“I was in front of something unlike anything I had ever seen,” says study co-author Alberto Collareta, also a paleontologist at the University of Pisa, to the Washington Post’s Dino Grandoni.

Researchers holding up huge whale vertebrae
The fossilized bones were so big and so dense that researchers were initially perplexed. Giovanni Bianucci

Their bone density would have helped P. colossus stay down near the ocean floor while feeding. And the species would’ve likely needed a little extra help to remain low in the water—unlike some whales that empty their lungs completely before diving, P. colossus probably dove with some amount of air still in its lungs. That’s how other inhabitants of shallow waters tend to dive, so researchers assumed the coastal-dwelling P. colossus might have done the same, reports Nature News’ Emma Morris.

Scientists say P. colossus was likely between 55 and 66 feet long, which would have made it shorter than today’s blue whales, which can grow up to 110 feet. It was likely shaped like a sausage and swam slowly by moving its body in undulating waves.

Each of the whale’s massive vertebrae weighed more than 200 pounds. But to estimate the animal’s total body mass, the researchers had to make an educated guess. For instance, since they haven’t found the creature’s skull, they don’t know what its head looked like. They also can’t tell how much blubber or muscle it had.

“Figuring out body weight for an extinct species is really, really hard,” says Nicholas Pyenson, a paleobiologist at Smithsonian’s National Museum of Natural History who was not involved in the study, to Nature News.

Based on the margin of error, Pyenson still believes the blue whale deserves the heavyweight trophy. But either way, he tells the publication, the discovery of P. colossus is “stupendous and very weird.”

“It’s just exciting to see such a giant animal that’s so different from anything we know,” says Hans Thewissen, a paleontologist at Northeast Ohio Medical University who was not involved in the research, to the Associated Press’ Maddie Burakoff.

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