Livyatan

Holotype and naming at the Museum of Natural History, Lima of National University of San Marcos In November 2008, a partially preserved skull with the teeth and lower jaw, the holotype specimen (MUSM 1676) of Livyatan melvillei, was discovered in the coastal desert of Peru in the sediments of the Pisco Formation, southwest of the city of Ica. Klaas Post, a researcher for the Natural History Museum Rotterdam in the Netherlands, stumbled across them on the final day of a field trip. The fossils were prepared in Lima, and are now part of the collection of the Museum of Natural History, Lima of National University of San Marcos. The discoverers originally assigned the English name of the biblical monster, Leviathan, to the whale as Leviathan melvillei. However, the scientific name Leviathan was preoccupied by Leviathan Koch, 1841, a junior synonym for the mastodon (Mammut). In August 2010, the authors rectified this situation by coining a new genus name for the whale, Livyatan, from the original Hebrew name of the monster. The species name melvillei is a reference to Herman Melville, author of the book Moby-Dick, which features a gigantic sperm whale as the main antagonist. The first Livyatan fossils from Peru were initially dated to around 13–12 million years ago (mya) in the Serravallian Age of the Miocene, but this was revised to 9.9–8.9 mya in the Tortonian Age of the Miocene. and so is younger than the L. melvillei holotype by around 4or 5million years. In 2019, palaeontologist Romala Govender reported the discovery of two large sperm whale teeth from Pliocene deposits near the Hondeklip Bay village of Namaqualand in South Africa. The pair of teeth, which are stored in the Iziko South African Museum and cataloged as SAM-PQHB-433 and SAM-PQHB-1519, measure and in height, respectively, the latter having its crown missing. Both teeth have open pulp cavities, indicating that both whales were young. The teeth are very similar in shape and size to the mandibular teeth of the L. melvillei holotype, and were identified as cf. Livyatan. Like the Beaumaris specimen, the South African teeth are dated to around 5mya. In 2025, Kristin Watmore and Donald Prothero reported a giant sperm whale tooth identified as cf. Livaytan discovered in Mission Viejo, California, during housing development during the 1980s and '90s. The tooth resided in the Orange County Paleontological Collection, cataloged as OCPC 3125/66099, and was incomplete but nevertheless measured at least in length and in diameter. Due to poor geographic recording at the time of its discovery, the exact stratigraphic locality was unknown, but it was reported to have come from a zone that contains both the mid-Miocene Monterey Formation and younger Capistrano Formation, the latter dating between 6.6 and 5.8 mya. The authors found the preservation of the tooth to be more consistent with Capistrano Formation fossils. The broken tooth surface exposed layers of cementum and dentin whose thicknesses fall within the known range of L. melvillei teeth. OCPC 3125/66099 represented the first evidence that either Livyatan or Livyatan-like whales were not restricted to the Southern Hemisphere and likely indicated a possibly global distribution of the cetaceans. == Description ==

The body length Livyatan melvillei was about . The body length of Livyatan is unknown because no postcranial skeleton has been found; size estimates are therefore based mainly on the holotype skull. Lambert and colleagues estimated the body length of Livyatan by comparing it to another macroraptorial sperm whale, Zygophyseter, and modern sperm whales. The authors opted to use the relationship between the bizygomatic width (distance between the opposite zygomatic processes) of the skull and body length because of the variable rostrum length in modern sperm whales and the rostrum of Livyatan being proportionally shorter. This approach yielded length estimates of using modern sperm whales and using Zygophyseter, with the range driven by the incompleteness of the Zygophyseter type specimen. It has been estimated to weigh based on the length estimate of . By comparison, the modern sperm whale length measures on average for females and for males, with some males reaching up to . The large size was probably an anti-predator adaptation, and allowed it to feed on larger prey. Livyatan is the largest extinct physeteroid discovered, possibly having one of the largest bite of any tetrapod. Basin The fossil skull of Livyatan had a curved basin, known as the supracranial basin, which was deep and wide. Unlike other raptorial sperm whales, but much like in the modern sperm whale, the basin spanned the entire length of the snout, causing the entire skull to be concave on the top rather than creating a snout as seen in Zygophyseter and Acrophyseter. The supracranial basin was the deepest and widest over the braincase, and, unlike other raptorial sperm whales, it did not overhang the eye socket. It was defined by high walls on the sides. The antorbital notches, which are usually slit-like notches on the sides of the skull right before the snout, were inside the basin. A slanting crest on the temporal fossa directed towards the back of the skull separated the snout from the rest of the skull and was defined by a groove starting at the antorbital processes on the cheekbones. The basin had two foramina in the front, whereas the modern sperm whale has one foramen on the maxilla, and the modern dwarf and pygmy sperm whales have several in the basin. The suture in the basin between the maxilla and the forehead had an interlocking pattern. ==Classification==

Livyatan was part of a fossil stem group of hyper-predatory sperm whales commonly known as macroraptorial sperm whales, or raptorial sperm whales, alongside the extinct whales Brygmophyseter, Acrophyseter and Zygophyseter. This group is known for having large, functional teeth in both the upper and lower jaws, which were used in capturing large prey, and had an enamel coating. Conversely, the modern sperm whale (Physeter macrocephalus) lacks teeth in the upper jaw, and the ability to use its teeth to catch prey. The cladograms below are modified from Lambert et al. (2017) and Paolucci et al. (2025), and represents the phylogenetic relationships between Livyatan and other sperm whales, with genera identified as macroraptorial sperm whales in bold. }} |1=†Rhaphicetus |2= }} }} }} == Palaeobiology ==

as the modern killer whale (Orcinus orca). Hunting Livyatan was an apex predator, and probably had a profound impact on the structuring of Miocene marine communities. Using its large and deeply rooted teeth, it is likely to have hunted large prey near the surface, its diet probably consisting mainly of medium-sized baleen whales ranging from in length. It probably also preyed upon sharks, seals, dolphins and other large marine vertebrates, occupying a niche similar to the modern killer whale (Orcinus orca). It was contemporaneous with and occupied the same region as the otodontid shark O. megalodon, which was likely also an apex predator, implying competition over their similar food sources. It is assumed that the hunting tactics of Livyatan for hunting whales were similar to that of the modern killer whale, pursuing prey to wear it out, and then drowning it. Modern killer whales work in groups to isolate and kill whales, but, given its size, Livyatan may have been able to hunt alone. Isotopic analysis of enamel from a tooth from Chile revealed that this individual likely operated at latitudes south of 40°S. Isotopic analyses of contemporary baleen whales in the same formation show that this Livyatan was not commonly feeding on them, indicating it probably did not exclusively eat large prey, though it may have targeted baleen whales from higher latitudes. Spermaceti organ in the modern sperm whale (Physeter macrocephalus) The supracranial basin in its head suggests that Livyatan had a large spermaceti organ, a series of oil and wax reservoirs separated by connective tissue. The uses for the spermaceti organ in Livyatan are unknown. Much like in the modern sperm whale, it could have been used in the process of biosonar to generate sound for locating prey. It is possible that it was also used as a means of acoustic displays, such as for communication purposes between individuals. It may have been used for acoustic stunning, which would have caused the bodily functions of a target animal to shut down from exposure to the intense sounds. Another theory says that the enlarged forehead caused by the presence of the spermaceti organ is used in all sperm whales between males fighting for females during mating season by head-butting each other, including Livyatan and the modern sperm whale. It may have also been used to ram into prey; if this is the case, in support of this, there have been two reports of modern sperm whales attacking whaling vessels by ramming into them, and the organ is disproportionally larger in male modern sperm whales. An alternate theory is that sperm whales, including Livyatan, can alter the temperature of the wax in the organ to aid in buoyancy. Lowering the temperature increases the density to have it act as a weight for deep-sea diving, and raising the temperature decreases the density to have it pull the whale to the surface. == Palaeoecology ==

(above) and Livyatan were apex predators of the same region. On the basis of these fossils, it was likely that the distribution of Livyatan was widespread. Prior to 2023, paleontologists initially believed that the genus was restricted to the Southern Hemisphere. The warmer waters around the equator have been known to be a climatic barrier for numerous cetaceans since Neogene times, and it was then-hypothesized is that Livyatan may have been among the cetaceans unable to cross the equatorial barrier. However, collecting bias was another explanation given the apparent rarity and poor fossil record of Livyatan, '' (right) L. melvillei is also known from the Bahía Inglesa Formation of Chile, whose fossiliferous beds are dated between the Tortonian and Messinian 9.03–6.45 mya. Like the Pisco Formation, the Bahía Inglesa Formation famously holds one of the richest marine vertebrate assemblages. Baleen whale remains include ancient minke whales, grey whales, bowhead whales and cetotheriids. Of the toothed whales, five species of pontoporiids as well as beaked whales, porpoises, three other species of sperm whales such as cf. Scaldicetus, and the Odobenocetops have been yielded. Other marine mammals include the marine sloth Thalassocnus and pinnipeds like Acrophoca. At least 28 different species of sharks have been described, including many extant ground sharks and white sharks as well as extinct species such as the false mako (Parotodus sp.), broad-toothed mako, megalodon and the transitional great white Carcharodon hubbelli. Other marine vertebrates include penguins and other seabirds, and species of crocodiles and ghavials. The Beaumaris sperm whale was found in the Black Rock Sandstone Formation of Beaumaris Bay, in Australia near the city of Melbourne, dating to 5mya in the Pliocene. Beaumaris Bay is one of the most productive marine fossil sites in Australia for marine megafauna. Shark teeth belonging to twenty different species have been discovered there, such as from the whale shark (Rhincodon typus), the Port Jackson shark (Heterodontus portusjacksoni), the broad-toothed mako and megalodon. Some examples of whales found include the ancient humpback whale Megaptera miocaena, the dolphin Steno cudmorei and the sperm whale Physetodon baileyi. Other large marine animals found include ancient elephant seals, dugongs, sea turtles, ancient penguins such as Pseudaptenodytes, the extinct albatross Diomedea thyridata and the extinct toothed seabirds of the genus Pelagornis. The South African teeth attributed as cf. Livyatan are from the Avontuur Member of the Alexander Bay Formation near the village of Hondeklip Bay, Namaqualand, which is also dated to around 5mya in the Pliocene. The Hondeklip Bay locality enjoys a rich heritage of marine fossils, whose diversity may have been thanks to the initiation of the Benguela Upwelling during the late Miocene, which likely provided large populations of phytoplankton traveling the cold nutrient-rich waters. Cetaceans are the most abundant fauna in the bay, although remains tend to be difficult to conclusively identify. Included are three species of balaenopterids including two undetermined species and one identified as cf. Plesiobalaenoptera, an ancient grey whale (cf. Eschrichtius sp.), an undetermined balaenid, an unidentified dolphin, and another undetermined species of macroraptorial sperm whale. Other localities of similar age on the South African west coast have also yielded many additional species of balaenopterids and sperm whales as well as ten species of beaked whales. Large sperm whale teeth of up to around ~ in length are common in Hondeklip Bay, indicating a high presence of large sperm whales like Livyatan in the area. The locality has also a high presence of sharks indicated by a large abundance of shark teeth; however, most of these teeth have not been identified. Megalodon teeth have been found in the bay, and evidence from bite marks in whale bones indicate the additional presence of the great white shark, shortfin mako and broad-toothed mako. Other marine fauna known in Hondeklip Bay include pinnipeds such as Homiphoca capensis, bony fish and rays. A large banana-shaped hole, resembling a bite from a Livyatan sp., was observed in the tooth of a medium-sized macroraptorial sperm whale found in California. A Livyatan sp. tooth measuring was actually discovered in the same area. This suggests that Livyatan was an apex predator that preyed on top predators that engaged in competitive exclusion by feeding on smaller macroraptorial sperm whales, such as Acrophyseter. Extinction Livyatan-like sperm whales became extinct by the early Pliocene likely due to a cooling trend causing baleen whales to increase in size and decrease in diversity, becoming coextinct with the smaller whales they fed on. It has been hypothesized by some that their extinction was the result of competition large predatory globicephaline dolphins, however evidence for this hypothesis are largely unsupported. ==Notes==