Perucetus

The ancient whale that briefly took the blue whale's crown. Announced in 2023 from 13 enormous vertebrae, four ribs and a hip bone dug from the desert on Peru's southern coast, it lived nearly 40 million years ago and was estimated at about 20 meters and 180 tons, within a range of 85 to 340. A 2024 reanalysis argued that the original estimate overstated how much its thick, heavy bones added to its weight, since manatees, which have similar bones, carry light bodies for their skeletons. It put Perucetus at roughly 60 to 70 tons for a 17-meter animal, in the range of a sperm whale. Its giant bones are real; the record claim is not proven, and it shows how much a mass estimate depends on assumptions about flesh nobody can see.