The bones, dated to 12 to 13 million years ago, were spotted by Klaas Post of the Natuurhistorisch Museum Rotterdam, the Netherlands, in Peru's Ica desert. In homage to Herman Melville's Moby Dick, the beast has been named Leviathan melvillei.
The skull is a huge 3 metres long, says team member Olivier Lambert at the Royal Belgian Institute of Natural Sciences. The team estimates the whale would have been between 13 and 18 metres long, like a modern sperm whale.
What really surprised the researchers was the size of the whale's teeth. "Some of the biggest ones are 36 centimetres long and 12 centimetres wide, and are probably the biggest predatory teeth ever discovered," Lambert says.
Teeth made for hunting
Unlike the modern-day sperm whale, which feeds by suction, the giant whale had these massive teeth on both its upper and lower jaw. "We think the whale used these teeth to catch its prey," says Lambert, suggesting the whale fed in a similar way to modern killer whales. Today's sperm whales have much smaller teeth on the lower jaw only.
"The whale would certainly have been able to catch very large prey, like baleen whales, of which there were plenty in the locality," Lambert says. "We think it was feeding on medium-sized baleen whales, which were about 8 or 9 metres long."
Leviathan melvillei is thought to have co-ruled the ocean with the giant shark Carcharocles megalodon, whose fossils have been found in the same locality in Peru. Lambert and colleagues estimate that the shark was about 15 metres long - more or less the same size as the giant sperm whale.
It's unlikely that the two giants would have battled each other, says Lambert. "At such sizes, I think it would have been very dangerous for adults of both species to fight," he says. "I could more easily imagine an adult of one species attacking a juvenile of the other." {read on}