Massive extinct whale ‘may be heaviest animal that ever lived’

A 39M-yr-old whale, Perucetus colossus, may be the heaviest animal ever, weighing up to 375 tons. Its bones are much denser than a blue whale's, suggesting it lived in shallow, coastal waters. It was likely not the longest animal ever, but its feeding habits remain a mystery.

There could be a new contender for heaviest animal to ever live. While today's blue whale has long held the title, scientists have dug up fossils from an ancient giant that could tip the scales.

Researchers described the species — named Perucetus colossus, or “the colossal whale from Peru” — in the journal Nature on Wednesday. Each vertebra weighs over 220 pounds (100 kilograms) and its ribs measure nearly 5 feet (1.4 metres) long.

“It’s just exciting to see such a giant animal that’s so different from anything we know," said Hans Thewissen, a palaeontologist at Northeast Ohio Medical University who had no role in the research.

The bones were discovered more than a decade ago by Mario Urbina from the University of San Marcos’ Natural History Museum in Lima. An international team spent years digging them out from the side of a steep, rocky slope in the Ica desert, a region in Peru that was once underwater and is known for its rich marine fossils. The results: 13 vertebrae from the whale’s backbone, four ribs and a hip bone.

The massive fossils, which are 39 million years old, “are unlike anything I’ve ever seen,” said study author Alberto Collareta, a palaeontologist at Italy's University of Pisa.

After the excavations, the researchers used 3D scanners to study the surface of the bones and drilled into them to peek inside. They used the huge — but incomplete — skeleton to estimate the whale's size and weight, using modern marine mammals for comparison, said study author Eli Amson, a paleontologist at the State Museum of Natural History in Stuttgart, Germany.

They calculated that the ancient giant weighed somewhere between 94 and 375 tons (85 and 340 metric tons). The biggest blue whales found have been within that range — at around 200 tons (180 metric tons).