Blue whale probably is the heaviest animal ever, discovery reveals

A FOSSILISED whale previously thought to have been the heaviest animal that ever lived is now thought to have weighed less than a blue whale.

The 17-metre creature, which was believed to have had very dense bones, was initially thought to have weighed as much as 340 tons. But American scientists have downgraded its weight – because it wouldn’t have been able to survive or swim if it weighed as much as once thought.

In a study published in the journal

the mammal, which lived 40 million years ago and was given the name

has been slimmed down, and is thought to have weighed less than half the largest blue whales.

The first vertebra of the sea giant was discovered in Peru’s Ica River Valley more than a decade ago. It belonged to an extinct group of early whales called the Basilosaurids.

Scientists found its bones to be unusually dense. Mammal bones normally have a solid exterior and a spongy or hollow centre, but some have a solid bone centre that makes them extremely dense and heavy. In aquatic animals, heavy bones offset buoyancy from body fat and blubber, allowing them to maintain a buoyancy in water or – as in the hippopotamus – to walk on river beds.

Perucetus bones were found to have extensive in-filling and extra growth of bone on the outside as well; a condition called pachyostosis that is also found in some present day aquatic mammals, such as manatees.

Scientists had estimated its body mass to have weighed between 180 metric tons and 340 metric tons – or more than 23 double-decker buses. This was heavy – as or heavier – than the biggest blue whales ever known, even though it was considerably shorter at 17 metres long. However, palaeontologists at the University of California (UC) Davis and the Smithsonian Institution dispute these weights and insist such estimates would have made the Perucetus impossibly dense.