Ancient whale may have been heavier than blue whale

Scientists examining the bones of a 39 million-year-old ancient whale have concluded that it may have been heavier than a blue whale, up to now thought to be the heaviest creature ever to have lived on Earth.

The fossils of the whale , known as a basilosaurid, were discovered 13 years ago in southern Peru but it has taken years of research for this discovery to be made.

The whale (now named Perucetus colossus) was not particularly large, only around 20m long, and resembled more of a modern-day manatee than the baleen whales we are familiar with. Whales only began to reach their much larger sizes around four and a half million years ago.

Scientists have learnt that the bones of the whale were extremely dense, the result of a process called osteosclerosis, where the inner cavities are filled. This, and other unusual bone features, are thought to have helped the whale with buoyancy in the shallow waters it inhabited.

While obtaining an exact idea of its weight is difficult, it is thought it could have been between 85 and 320 tonnes. In comparison, before commercial whaling decimated their numbers, some blue whales could weigh around 200 tonnes.

Research paper:
Bianucci, G., Lambert, O., Urbina, M. et al. A heavyweight early whale pushes the boundaries of vertebrate morphology. Nature (2023). https://doi.org/10.1038/s41586-023-06381-1