When you hear the words "raptorial sperm whale" what do you think of? A warped Moby Dick? A SyFy original movie? The picture above? Go with Door #3.
A new paper in Nature titled "The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru" describes the discovery of one of the biggest predators to ever live - a whale eating whale. Whoa.
The newly discovered whale has been named Leviathan melvillei, a name loosely translated as 'Melville's sea monster.' The bones were discovered in Cerro Colorado in the Pisco-Ica Desert on the southern coast of Peru two years ago by paleontologists Olivier Lambert and Klaas Post and their team. The researchers were able to recover 75% of the whale's skull, including large fragments of jaws and several teeth. The huge whale (13.5-17.5 meters long) is thought to have lived and died about 12-13 million years ago and is most closely related to modern day sperm whales (Physeter macrocephalus). Today's sperm whales have small teeth (less than 26 cm), lack functional teeth in the upper jaw, and feed by suction - a morphology suited to a squiddy diet. Conversely, L. melvillei has large, interlocking teeth approximately 36 cm (15 in) long. The mouth itself is 3 meters (9 ft) long and just over 2 meters (7 ft) wide with a skull structure that suggests very powerful biting muscles. Put these traits together and you get an animal that hunts in a similar way to extant killer whales (Orcinus orca), using its teeth to capture prey and tear off flesh. Yum. L. melvillei is thought to have fed on medium-sized (7-10 m long) baleen whales and other large prey; it would have been an effective competitor with Megalodon (the giant shark of that age).
If you picture a sperm whale what do you see? Yeah, massive head and itty-bitty mouth (well, relatively at least). That big ole head is mostly forehead, a forehead that holds the "spermaceti organ." This organ is composed of a series of oil and wax reservoirs buttressed with massive partitions of connective tissue, and it's thought to help the whales dive deeply. The skull of L. melvillei exhibits a curved basin atop the snout which suggests that it also had this organ, even though it was not a specialized deep diver. So why have it? The authors suggest that the organ existed before modern sperm whales adapted to deep diving, probably for other functions such as echolocation and/or acoustic displays. Another possibility? Aggressive head-butting. Think underwater goats/rams. Wow. Well, there are records of at least two nineteenth-century whaling ships were sunk when large male whales punched holes in their sides with their foreheads, so the idea isn't too far out there. The underwater head-butting could have been used to show dominance in such situations as contests over females. Its just kinda fun to picture two huge whales swimming at each other at full speed and then crashing their heads together - imagine the wave off of that!
The massive cetacean is thought to have been driven to extinction by changes in its environment, namely its prey and the effects of climate cooling. At that time baleen whales were widely diverse and then underwent a significant changes in number, diversity, and size. Changes in prey are known to impact top predators in a drastic way - no prey means a predator must adapt or go extinct. L. melvillei's surviving relatives (Physeter, pygmy and dwarf sperm whales) are deep-diving, squid-eating specialists - a very different ecological niche than L. melvillei.
Here's the article:
Lambert, Olivier et al. (2010) The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru. Nature: 466, 105-108. (DOI: 10.1038/nature09067)
and here's some write-ups about it: