The massive skull and jaw of a 13-million-year-old sperm whale has been discovered eroding from the windblown sands of a coastal desert of Peru.
The extinct cousin of the modern sperm whale is the first fossil to rival modern sperm whales in size — although this is a very different beast, say whale evolution experts.
"We could see it from very far," said paleontologist Olivier Lambert of the Muséum National d'Histoire Naturelle in Paris, France, who led the team which found the fossil.
The giant 3-meter (10-foot) skull of what's been dubbed Leviathan melvillei (in honor of the author of "Moby Dick") was found with teeth in its top and bottom jaws up to 36 centimeters (14 inches) long. The discovery is reported in the July 1 issue of the journal Nature.
Living sperm whales have teeth only in their lower jaws and are specialized to feed on giant squid, Lambert explained. They suck down squid like large spaghetti noodles rather than catch the prey with their teeth. The much toothier fossil sperm whales, however, may have eaten more like a outsized-orca, or killer whale: chomping great big bites out of its prey.
"These are very unusual attributes," said cetacea evolution expert Ewan Fordyce of the University of Otago in New Zealand. "It's remarkably big. That is unexpected."
Another sign that this ancient whale had a killer bite is the large hole in the skull to accommodate a large jaw muscle.
"This was a hunting predator that took chunks out of prey," said Fordyce.
It most likely fed on baleen whales, Lambert and his colleagues report, and lived in the same waters as the monster-sized shark called Carcharocles megalodon.
To learn more about its eating habits, Fordyce said it would be useful to look at the microscopic wear patterns on the teeth. If the wear lines are horizontal, it probably sucked in prey like today's whales. But if the wear lines are vertical, it would suggest a biter, like the orca.
"Many fossil sperm whales have been found in the past," said Lambert. "Most have been much smaller than modern sperm whales."
There have also been discoveries of isolated large sperm whale teeth fossils before, said Lambert. Those made it clear to researchers there was a bigger animal out there waiting to be found. And now they have found it.
"I think it's a great advance," said Fordyce of the discovery.
The fossil appears to also be a distant relative of today's sperm whales, said Fordyce, rather than a direct ancestor.