Clearly, it's named after the author of "Moby-Dick" because it seems like something out of fiction.
Here's a taste of the (pay-to-view) article in "Nature":
Here we report the discovery of a new giant sperm whale from the Middle Miocene of Peru (approximately 12–13 million years ago), Leviathan melvillei, described on the basis of a skull with teeth and mandible. With a 3-m-long head, very large upper and lower teeth (maximum diameter and length of 12 cm and greater than 36 cm, respectively), robust jaws and a temporal fossa considerably larger than in Physeter, this stem physeteroid represents one of the largest raptorial predators and, to our knowledge, the biggest tetrapod bite ever found. The appearance of gigantic raptorial sperm whales in the fossil record coincides with a phase of diversification and size-range increase of the baleen-bearing mysticetes in the Miocene. We propose that Leviathan fed mostly on high-energy content medium-size baleen whales. As a top predator, together with the contemporaneous giant shark Carcharocles megalodon, it probably had a profound impact on the structuring of Miocene marine communities.
Here's the video with a quick glimpse at this rorqual eater and its discovery in the Peruvian desert. (The full "Nature" video is here.)
Discover Magazine brings this monster, which had interlocking teeth on the skull and lower jaw, alive:
It’s perhaps no coincidence that the biggest shark in history – the mighty Megalodon – also appeared at the same time in the same part of the world. It too was thought to have hunted whales and many of its teeth have also been found at Cerro Colorado. For the moment, it’s hard to say if the two predators were direct competitors, since they may have swum in different parts of the Peruvian seas. Lambert speculates that the adults of either species could have eaten the young of the other but there’s no evidence for this yet....
The skull is beautifully adapted to capture large, powerful prey. The snout was short and wide, allowing it to bite more strongly with its front teeth and resist the struggles of its prey. Its temporal fossa – the shallow depression on the side of the skull – was enormous and could old huge jaw-closing muscles. The bite would have been the largest of any tetrapod (the animal group that includes mammals, birds, reptiles and amphibians). And the teeth were deeply embedded in the jaw bones for each support, and interlocked to give the animal a shearing, meat-carving bite. They were also angled forwards, giving Leviathan a better grip on prey with curved bodies.
The skull also creates a mystery. Sperm whales have a unique organ in their heads called the spermaceti, and Leviathan’s was particularly large. The spermaceti is full of a waxy substance that was originally thought to be the animal’s sperm (hence the name). Its purpose isn’t clear although there are many theories, all of which must now be considered in the light of Leviathan’s very different lifestyle.
This is one of those new chapters that are so thrilling to observe from their first moments, and I can't wait to find out more about Leviathan and his place in biological history.