Livyatan melvillei

Livyatan melvillei is an extinct species of physeteroid whale, which lived during the Miocene epoch, approximately 12-13 million years ago.

Discovery
In November 2008, fossil remains of Livyatan melvillei were discovered in the sediments of the Pisco formation at Cerro Colorado, 35 kilometres (22 mi) south-southwest of Ica, Peru.[2] The remains include a partially preserved skull with teeth and mandible.[2] Rotterdam Natural History Museum researcher Klaas Post stumbled across them on the final day of a field trip there in November 2008.[1] Post was part of an international team of palaeontologists.[3]

The fossils have been dated at 12–13 million years old and were prepared in Lima, Peru,[1] and are now part of the collection of the Natural History Museum there.

Etymology and nomenclature
Researchers originally assigned the English name of the biblical monster, Leviathan, to this prehistoric whale as Leviathan melvillei, dedicating the discovery to Herman Melville, author of Moby-Dick—the researchers behind the excavation of L. melvillei were all fans of this novel.[3] However, the scientific name Leviathan was a junior homonym of Leviathan Koch, 1841 for a genus of mastodon (see Leviathan in Wikispecies). Junior homonyms need to be replaced with new names, except under certain special circumstances (ICZN 1999 Article 60). In August 2010, the authors rectified this situation by coining a new genus name for the whale, Livyatan, from the original Hebrew spelling.

Description
Livyatan melvillei was 13.5 to 17.5 metres (44–57 ft) long, about the same as a modern adult male sperm whale.[2] The skull of Livyatan melvillei is 3 metres (10 ft) long.[2] Unlike the modern sperm whale, Physeter macrocephalus, L. melvillei had functional teeth in both its jaws.[2] The jaws of L. melvillei were robust and its temporal fossa was also considerably larger than in the modern-age sperm whale.[2] L. melvillei is one of the largest predators yet known, with whale experts using the phrase "the biggest tetrapod bite ever found" to explain their find.[2] The teeth of L. melvillei are up to 36 centimetres (1.18 ft) long and are thought to be the largest of any animal yet known.[2] Larger 'teeth' (tusks) are known, such as walrus and elephant tusks, but these are not used directly in eating.

Size
Two physeterids have been chosen by whale experts for comparison to estimate the size of L. melvillei.[2] The anatomy of Physeter macrocephalus yielded a total length (TL) of 13.5 m (= 44.3 feet) for L. melvillei,[2] and that of Zygophyseter varolai yielded a TL of 17.5 m (= 57.5 feet) for L. melvillei.

Skull structure
The fossil skull of L. melvillei has a curved basin which suggests it might have had a large spermaceti organ, a series of oil and wax reservoirs separated by connective tissue. This organ is thought to help modern sperm whales to dive deeply to feed. However, L. melvillei is likely to have hunted large prey near the surface, so it appears that this organ would have had other functions. Possible suggestions include echolocation, acoustic displays (with the spermaceti organ acting as a resonance chamber) or aggressive headbutting, possibly used against competing males in mating contests or to batter prey.