Perucetus colossus

The heaviest animal ever revealed: A giant ancient whale that lived 39 million years ago and weighed more than 340 tonnes may be the largest creature on record.

Perucetus colossus is presented in a new study led by paleontologist Eli Amson, at the State Museum of Natural History Stuttgart in Germany, exceeding that of any known mammal or aquatic vertebrate.

“It displays, to our knowledge, the highest degree of bone mass increase known to date, an adaptation associated with shallow diving.”

The fossil, found in Southern Peru, includes 13 vertebrae, four ribs and a hip bone from a basilosaurid whale researchers estimate would have weighed between 85 and 340 tonnes. At the higher end of that spectrum, the researchers say, the whale would have weighed more than a blue whale which is currently believed to be the heaviest animal ever to exist.

Perucetus colossus
Credit Giovanni Bianucci

Estimates of its size and weight, based on a partial skeleton, rival those of the blue whale, which was previously thought to be the heaviest animal ever to exist. The findings suggest that the trend toward gigantism in marine mammals may have begun earlier than previously thought.

The fossil record of cetaceans (a suborder of mammals that includes dolphins, whales, and porpoises) is of great importance when documenting the evolutionary history of mammalian life when some terrestrial animals were returning to the ocean. Previous records have identified adaptations to an aquatic lifestyle, which include a trend towards gigantism and an associated increase in body mass, although the peak body mass is thought to have been a relatively recent diversification.

source Scimex