Extinct Colossus Is Not the Heaviest Creature of All Time; Weird Whale’s Weight Was Overestimated [Study]

The extinct whale, Perucetus colossus, was initially believed to be the heaviest. However, a team of researchers argued that it was true.

Perucetus Colossus Not the Heaviest, Largest Creature

Researchers revealed the 39-million-year-old Peruvian whale, Perucetepus colossus, last year. Its estimated body mass ranges from 187,000 to 750,000 pounds (85,000 to 340,000 kilograms), possibly double that of a blue whale (Balaenoptera musculus).

In a new study, the researchers deduced that the initial team had greatly exaggerated the animal's weight, asserting that if the species had weighed as much as their highest estimate had suggested, it would have been too dense to float in the water.

"With their weight, this animal could not stay at the surface," lead author Ryosuke Motani, a paleobiologist at the University of California, Davis, explained. "This animal would have been swimming vertically up all the time, which is impossible."

In addition to cross-examining the original study, Motani and his colleague Nicholas Pyenson-the curator of fossil marine mammals at the Smithsonian National Museum of Natural History-created 3D models of a P. colossus and a blue whale and varied their assumptions on the computation of weight.

They discovered that blue whales can weigh up to 600,000 pounds (270,000 kg), while P. colossus was closer to 130,000 to 250,000 pounds (60,000 to 113,000 kg). The extinct P. colossus is smaller and substantially heavier than the contemporary blue whale in the comparative image.

Eli Amson, a paleontologist and curator of ancient mammals at the Stuttgart State Museum of Natural History in Germany, was the primary author of the first P. colossus study. He told Live Science that he stands by all of his team's initial conclusions and that their broad range was a cautious estimate.

They knew it was coming because Amson and another author from the 2023 study reviewed the new research before it was published. He pointed out that the study only produced varied estimates based on its data rather than discovering real errors in its study.

Before the new study's release, Amson and his colleague raised several reservations about it. Specifically, they pointed out that the authors' estimation of mass and volume was based on an artist reconstruction from their earlier research, which, according to Amson, wasn't created with the creature's volume in mind.

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**What Is Perucetus Colossus?**

With over 100 feet and a weight of around 200 tons, the blue whale has long been considered the largest mammal in history. However, paleontologists have discovered an enormous cetacean that may have been even heavier and shorter than previously thought. This species lived more than 37 million years ago near the coast of ancient Peru.

Paleontologist Giovanni Bianucci and associates at the University of Pisa named the ancient whale Perucetus colossus, which may have weighed over 300 tons. Mario Urbina, a paleontologist from the National University of San Marcos and co-author of the paper, discovered the fragmentary skeleton 13 years ago among the rocks of the Ica Valley in southern Peru. The bones were so big that they resembled stones; therefore, the discovery was not immediately striking.

The researchers unearthed 13 vertebrae, four ribs, and a portion of the hip among the fossils from the Ica Valley. According to the structure of the bones and the time the animal was swimming off the coast of South America, the whale was a relative of Basilosaurus, a fully aquatic whale with a large snout full of cutting and piercing teeth. Amson and colleagues estimated the behemoth's size by comparing the known bones of Perucacetus with the more complete skeletons of both extinct and extant whales.

Even though it was not very long, Perucetus had to weigh much. The fossils found have significant pachyosteosclerosis, a disorder characterized by the thick, dense bones of manatees and other early whales. Marine mammals with such robust bones can maintain their submerged weight without becoming too heavy on the surface.