39-million-year-old extinct whale believed to be the heaviest mammal that ever lived

In terms of size, blue whales have long been regarded as world record-breakers. Scientists believe a prehistoric species of whale that swam in the oceans around 39 million years ago may have been the biggest mammal to ever exist. Thirteen years ago, a partial skeleton was discovered in the Ica desert on the southern coast of Peru. The remains, consisting of 13 vertebrae, four ribs, and one hip bone, were recently analyzed by researchers.

Their research, which was published in the journal Nature, indicates that this extinct whale, with body mass between 85 and 340 tonnes, may have been up to three times larger than a blue whale, which was previously believed to be the heaviest mammal ever to have existed.

The recently discovered species has been named Perucetus colossus by scientists, in recognition of both its massive size and the location of its discovery. According to Dr Eli Amson, a researcher at the State Museum of Natural History Stuttgart in Germany, the P colossus could possibly be the largest and heaviest animal discovered so far.

"In any case, it was at least as heavy as the blue whale. But the P. colossus we describe was not longer than the largest blue whales. We estimate the new species’ specimen to have been 17m-20m (56ft-66ft) long, while blue whales can reach 30m (98ft)," said Dr Eli Amson, according to reports. 

P. colossus is a member of the basilosaurid family, which are extinct cetaceans that belong to the same class of mammals as dolphins, whales, and porpoises. These creatures lived during the middle Eocene to the late Oligocene epoch, which was approximately 41 million to 23 million years ago.

A reconstruction of the P. colossus suggests it is two to three times heavier than the 25m (82ft) long blue whale skeleton on show at the Natural History Museum in London.

According to researchers, the tremendous bone mass of P. colossus is due to the presence of additional bone on the outer surface of the skeletal elements and the compact bone filling the inner cavities. According to the authors, these animals use extra weight to control their buoyancy and adjust their positioning when underwater. The researchers speculate that P. colossus may have been a slow swimmer and lived near the coast.