Gigantic New Species of Ancient Whale May Be Heaviest Animal Ever to Exist

A gigantic ancient whale has been uncovered by researchers—and it potentially represents the heaviest animal ever known to exist.

Weight estimates of the now-extinct whale species, named Perucetus colossus, rival, and even exceed, that of the blue whale, according to a study published in the journal Nature.

The blue whale has long been considered the largest known animal ever to have lived. It can grow up to around 100 feet in length and the largest specimens have weighed as much as 180 metric tonnes (198 tons).

But this title may now be under threat, with the Nature study authors estimating that P. colossus could have had a body mass of up anywhere between 85 and 340 tonnes (93 and 375 tons)—equaling or even surpassing that of the blue whale.

The newly-identified species is described based on the partial skeleton of one individual found in Southern Peru estimated to be about 39 million years old. The remains include 13 vertebrae, a few ribs and one hip bone.

"The bones, to put it bluntly, look like they come from another planet: they are huge and bloated," Eli Amson, an author of the Nature study with the Stuttgart State Museum of Natural History in Germany, told Newsweek.

The fossil was found in the Ica Desert, along the Peruvian coast, which can be considered an extension of the Atacama Desert—one of the most arid places on Earth.

Amson and his colleagues have known about the ancient whale fossils for 13 years now but it has taken a "very long time" and many field trips to collect all the huge bones, he said, hence why the species has only just been described.

Because only parts of the skeleton have been found, it is difficult to provide a precise idea of the whale's appearance—particularly the head, which remains a mystery—and overall physical characteristics. But based on a close relative, the researchers estimate its overall length to be between around 55 and 65 feet.

This would not be as long as the blue whale. But the researchers predict that P. colossus most likely had a heavier skeleton, weighing two to three times that of the blue whale. It was either as heavy overall or even heavier when taking the other body parts into account.

"We gave a range of estimates and took uncertainty into account in different ways," Amson said. "Our lower estimate, 85 tonnes, is very conservative. But that is still falling within the distribution of blue whales. That's why we are quite confident that we are in the ballpark of blue whale in terms of overall mass."

In fact, the researchers said that the species pushes the upper limit of skeletal mass in mammals, as well as aquatic vertebrates in general.

Given that the head of P. colossus remains a mystery, the researchers can only speculate with regards to its possible diet.

"Feeding on small fish is unlikely because Perucetus was most likely not an agile swimmer—can you imagine the inertia of such [a] tremendous body?" Amson said. "The head was most likely small, based on all other members of the family and [there is] no reason to think that it acquired the adaptations necessary to filter-feed.

"My personal favorite—but again, that is only speculation for now—is that it was a scavenger, feeding on underwater carcasses of some other large animal. What is quite clear, given the bone mass increase characterizing Perucetus, is that it was living on the coast, in shallow waters."

From a scientific perspective, probably the most important implication of the latest discovery concerns the evolution of cetaceans, the animal group that contains whales, dolphins and porpoises, and more generally that of extreme gigantism, Amson said.

So far, extreme gigantism in cetaceans, as seen in the baleen whales, like blue whales and gray whales, has been regarded as a relatively recent phenomenon (dated to around 5 million years ago) and also associated with offshore habits.

The latest findings, though, suggest that the trend toward gigantism in marine mammals may have begun earlier.

"Thanks to Perucetus, we now know that gigantic body masses have been reached 30 million years before previously assumed, and in a coastal environment," Amson said.

"The discovery of the new fossil hence shows us that the coastal environment can sustain such a gigantic animal, something we did not expect at all," he said. "More generally, this demonstrates that extreme gigantism can be acquired through a completely different evolutionary path as was known before—i.e., blue whales and sperm whales are open-sea inhabitants."