In 2023, researchers in Peru made headlines when they unveiled what they believed to be the heaviest animal ever discovered. Named Perucetus colossus (or simply P. colossus), this ancient whale was described as having a massive, bloated body, a small head, and undersized fins. Estimates suggested it weighed an astounding 700,000 pounds, far surpassing the blue whale, which holds the modern record at up to 540,000 pounds.
The fossils of this prehistoric leviathan, thought to be around 40 million years old, were uncovered in Peru’s desert regions. Unlike typical spongy-looking bones, these specimens appeared unusually dense and inflated, causing initial confusion among scientists, who debated whether they were bones or rocks. Upon closer examination, the fossils were confirmed to be vertebrae, with each bone weighing approximately 220 pounds. Additional discoveries included ribs nearly five feet long. Altogether, the team unearthed 13 vertebrae, four ribs, and a fragment of the animal’s hip.
Based on these findings, researchers initially concluded that P. colossus was the heaviest animal to ever roam the Earth.
The discovery sparked widespread media coverage, with many marveling at the extraordinary size of this unusual whale.
A Revised Estimate
However, in February 2024, the scientific community reassessed its earlier calculations. New research suggested the weight estimates had been significantly overstated. Rather than being the heavyweight champion of all time, P. colossus was revealed to be, quite literally, big-boned.
Revised estimates place its weight at around 60 to 70 tons for a 17-meter individual and between 98 and 114 tons for a 20-meter specimen. While still an enormous creature, its maximum weight of approximately 228,000 pounds falls well short of the blue whale’s record-breaking 540,000 pounds (270 tons).
The Science Behind the Miscalculation
So, what led to the original overestimation? A new study, titled “Downsizing a Heavyweight: Factors and Methods That Revise Weight Estimates of the Giant Fossil Whale Perucetus colossus,” provided some answers.
The researchers behind the initial estimates used a novel approach, extrapolating the whale’s skeletal mass from the fossilized bones. They then calculated its total body mass by applying ratios observed in modern marine mammals like cetaceans and sirenians. While this method seemed reasonable at the time, the study pointed out flaws in their assumptions, particularly the idea of a fixed ratio between skeletal and body mass.
The new study noted that this earlier approach was based on “questionable assumptions” and described the resulting estimates as “unreasonable.” In simpler terms, the math didn’t add up.
An Artist’s Perspective
Despite the adjustments, the overall size estimates for P. colossus remain unchanged. Artist Cullen Townsend, who specializes in creating reconstructions of prehistoric creatures for institutions like the Natural History Museum of Los Angeles, emphasized the evolving nature of paleontology.
“What’s now being debated is the animal’s weight,” Townsend explained. “Our understanding of prehistoric animals is always evolving, as new discoveries and research reshape what we know. This isn’t unusual—it’s how science works. Our interpretations of Perucetus will likely continue to change as we learn more.”
Public Reactions
The revised weight of P. colossus sparked mixed reactions among enthusiasts. Members of the NatureWasMetal subreddit expressed both disappointment and acceptance.
One user, Kaam00s, commented, “Of course, Perucetus was going to be downsized. I’ll never trust these claims again.”
Another, Grouper3, added humorously, “All my hopes and dreams shattered. I lived for that chonky whale!”
Yet others found solace in the fact that the blue whale retains its title as the largest known animal to have ever lived. “We’re lucky to share the planet with such an incredible species,” wrote Time-Accident3809. “Let’s hope we don’t mess that up.”
In the ever-changing world of paleontology, P. colossus may have lost its title as the heaviest animal in history, but its discovery continues to shed light on the fascinating giants of the past.