Dubbed Leviathan melvillei—an homage to Moby-Dick author Herman Melville—the recently unearthed fossil sea monster lived about 13 million years ago in waters atop what's now a Peruvian desert, according to a study published by the journal Nature on Wednesday.
Living alongside the largest sharks ever known, the raptorial—meaning actively hunting—whale measured about 60 feet (18 meters) in length, about as big as a modern male sperm whale.
But whereas modern sperm whales feed primarily on squid, Leviathan's large teeth—some of which measured more than a foot (36 centimeters) long—suggest the whale hunted more challenging prey, including perhaps its close whale relatives.
"It was probably a very powerful and frightening animal, so it fits well with the description Melville made of Moby-Dick," said lead study author Olivier Lambert, a paleontologist at the National Museum of Natural History in Paris.
As fearsome as Leviathan was, the whale may have met its match in Carcharodon megalodon, or the "megatooth shark," which lived at the same time and even the same region.
Megalodon was the largest shark that ever lived and possibly competed with Leviathan for other whales. "Maybe they were fighting," study leader Lambert said.
If the two mega-monsters did clash, it's unclear who would have won. "Clearly they both could have attacked each other's juveniles," but a match between two adults may have been less clear-cut, he added.
A Peruvian member of the study team stands among sand dunes in the desert where Leviathan mellvillei's fossils were found.
Study leader Lambert and his team think this Peruvian desert was once the bottom of a shallow, lagoon-like body of water home to many species of whales, dolphins, porpoises, seals, and sharks. "There was plenty of food for this animal," Lambert said of Leviathan.
Scientists think the giant sperm whale ambushed its prey like modern killer whales. But unlike killer whales, which must work together to hunt bigger prey, a solo Leviathan could have easily taken down another whale.
"With such a strong bite, we think it was possible for him to catch large prey alone," Lambert said.
Leviathan mellvillei's skull and jawbone, diagrammed above, boasted large teeth in both the top and bottom jaws—and enough room to accommodate a modern man.
By contrast, today's sperm whales have smaller teeth, which are mostly in their lower jaws—an adaption for hunting squid by suction.
Leviathan shows that "raptorial feeding had gotten to a really extreme size," said Jonathan Geisler, a whale evolution expert at the New York Institute of Technology, who was not involved in the discovery.
The idea that Leviathan fed on other whales is a "good inference," Geisler said. "But to really pin it down, we're going to need to find some whale bones with [Leviathan's] bite marks."
Some of those marked fossils, he added, might already be sitting in museum collections.