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Livyatan

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For the biblical creature, see Leviathan.

Livyatan
Temporal range: Tortonian
~9.9–8.9 Ma
↓
Cast of skull at the Museo di storia naturale dell'Università di Pisa
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Superfamily: Physeteroidea
Family: incertae sedis
Genus: †Livyatan
Lambert et al., 2010
Species:
†L. melvillei
Binomial name
†Livyatan melvillei
(Lambert et al., 2010)
Synonyms[1]
  • Leviathan melvillei
    Lambert et al., 2010

Livyatan is an extinct genus of sperm whale, similar in size to the modern sperm whale (Physeter macrocephalus), containing one species: L. melvillei. Its name was inspired by the biblical sea monster Leviathan, and the book Moby-Dick by Herman Melville, where the villain is a large sperm whale. It was found in the Pisco Formation of Peru and lived during the Tortonian stage of the Miocene epoch, about 9.9-8.9 million years ago (mya), however a large tooth from Australia implies either it or a close relative survived into the Pliocene, around 5 mya. It was a member of a group of hyper-predatory macroraptorial sperm whales (often shortened to "raptorial") and was an apex predator preying on whales, seals, and so forth. A characteristic of raptorial sperm whales is a functional, enamel-coated teeth on the upper and lower jaws, as well as several adaptations for hunting large prey.

Its total size was estimated to be 13.5 or 17.5 m (44 or 57 ft), making it one of the largest predators to have ever existed. The tallest tooth measured 36.2 cm (14.3 in), and is the largest tooth of any known animal. It is distinct from the other raptorial sperm whales by the basin on the skull, and how it spans the entire length of the snout. The usage of its spermaceti organ, contained in that basin, is thought to have been used in either biosonar and communication, or for ramming prey and other sperm whales. It may have interacted with the large extinct shark Megalodon, competing with it for a similar food source. Its extinction was likely caused by climate change which caused food populations to drop. The formations where the whale has been found have also unearthed a large assemblage of marine vertebrates. The whale was featured in the animated movie Ice Age: Continental Drift.

Taxonomy

Research history

Skull of the holotype at the Museum of Natural History, Lima

In November 2008, a partially preserved skull containing teeth and mandible belonging to L. melvillei, the holotype MUSM 1676, were discovered in the coastal desert of Peru in the sediments of the Pisco Formation, 35 km (22 mi) south-southwest of the city of Ica.[1][2] Rotterdam Natural History Museum researcher Klaas Post stumbled across them on the final day of a field trip there in November 2008,[3] and was part of an international team of paleontologists composed by researchers of the National Museum of Natural History in Paris, Utrecht University, and the Museum of Natural History of the National University of San Marcos in Lima, among others.[4] The fossils were prepared in Lima,[3] and are now part of the collection of the Natural History Museum there.[5]

The discoverers originally assigned the English name of the biblical monster, Leviathan, to the whale as Leviathan melvillei. However, the scientific name Leviathan was also the junior homonym for the mastodon (Mammut), so, in August 2010, the authors rectified this situation by coining a new genus name for the whale, Livyatan, from the original Hebrew spelling of the monster. The species name melvillei is a reference to Herman Melville, author of the book Moby-Dick which stars a gigantic sperm whale as the main antagonist.[4][6]

Phylogeny

Livyatan was part of a fossil stem group of hyper-predatory sperm whales commonly known as macroraptorial sperm whales, alongside the extinct whales Brygmophyseter, Acrophyseter, and Zygophyseter. This group is known for having large, functional teeth on 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 enamel, teeth in the upper jaw, and the ability to use its teeth to catch prey.[7] Livyatan belongs to a different lineage than the other raptorial sperm whales, and the size increase and the development of the spermaceti organ, a characteristic of sperm whales, are thought to have evolved independently from other raptorial sperm whales. The large teeth of the raptorial sperm whales either evolved once in the group with a basilosaurid-like common ancestor, or independently in Livyatan. The large temporal fossa in raptorial sperm whales is thought to a plesiomorphic feature, that is, a trait inherited from a common ancestor. Since fetal modern sperm whales have enamel on their teeth before being coated with cementum, it is thought that the enamel is also an ancient characteristic. The appearance of raptorial sperm whales in the fossil record coincides with the diversification of baleen whales in the Miocene, implying that they evolved specifically to exploit baleen whales.[1][8] It has been suggested that the raptorial sperm whales be placed in the subfamily Hoplocetinae, alongside the genera Diaphorocetus, Idiorophus, Scaldicetus, and Hoplocetus, which are known from the Miocene to the lower Pliocene. This subfamily is characterized by their robust and enamel-coated teeth.[9]

The first Livyatan fossils from Peru were 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.[8] However, in 2016, a large sperm whale tooth measuring 30 cm (12 in), specimen NMV P16205, was discovered in Pliocene strata in Beaumaris Bay, Australia, by a local named Murray Orr, and was nicknamed the "Beaumaris sperm whale" or the "giant sperm whale". The tooth was donated to Museums Victoria at Melbourne. Though it has not been given a species designation, the tooth bears an appearance similar to those of L. melvillei, indicating that it was either closely related to L. melvillei, belongs to the genus Livyatan, or is a specimen of L. melvillei. The tooth is dated to around 5 mya,[10][11][12] and so is younger than the Peruvian L. melvillei specimen by around 3 million years.[1]

Physeteroidea
Relationships between Livyatan and other sperm whales, raptorial sperm whales in bold[7][8][1]

Description

Reconstruction of Livyatan (left) next to Cetotherium (right)

The total length of L. melvillei is estimated to have been 13.5 m (44 ft) when using the modern sperm whale for scaling, and 16.2–17.5 m (53–57 ft) when using the raptorial Zygophyseter for scaling. Since only the skull of Livyatan is known, the ratio of the skull compared to the rest of the body length is unknown, and so its total body length is not known for certain. In comparison, the modern sperm whale measures on average 11 to 16 m (36 to 52 ft). The large size was probably an anti-predator adaptation, and allowed it to feed on larger prey.[1] The Beaumaris sperm whale was estimated to have been around 18 m (59 ft) and 40 t (44 short tons).[11] Livyatan is the largest fossil sperm whale discovered, and was also one of the biggest known predators, and it had one of the largest bites of any tetrapod, and possibly of any vertebrate.[1][8]

Skull

The skull of L. melvillei was 3 m (9.8 ft) long in the holotype. Like other raptorial sperm whales, Livyatan had a wide gap in between the temporal fossae on the sides of the skull and the zygomatic processes on the front of the skull, indicating a large space for holding strong temporal muscles, which are the most powerful muscles between the skull and the jaw.[1][8] The snout was robust, thick, and relatively small, which allowed it to clamp down harder and better handle struggling prey. The left and right premaxillae on the snout probably did not intersect at the tip of the snout, though the premaxillae took up most of the front end of the snout. Unlike in the modern sperm whale, the premaxillae reach the sides of the snout. The upper jaw was thick, especially midway through the snout. The right maxilla in the upper jaw became slightly convex towards the back of the snout, whereas the left maxilla became slightly concave towards the back of the snout. The vomer reached the tip of the snout, and was slightly concave, decreasing in thickness from the back to the front. A sudden thickening in the middle-left side of the vomer may indicate the location of the nose plug muscles. Each mandible in the lower jaw was higher than it was wide, with a larger gap in between the two than the modern sperm whale. The mandibular symphysis which connects the two mandibles in the middle of the lower jaw was unfused. The condyloid process, which connects the lower jaw to the skull, was located near the bottom of the mandible like other sperm whales.[1][8]

Teeth

The teeth of Livyatan were among the biggest of any animal at over 31 cm (12 in) long.[1]

Unlike the modern sperm whale, Livyatan had functional teeth in both of its jaws. The wearing on the teeth indicate that the teeth sheared past each other while biting down, meaning it could bite off large portions of flesh from its prey. None of the teeth of the holotype were complete, and none of the back teeth were well-preserved. As well as this, the teeth were deeply embedded into the gums and could interlock, which were adaptations to holding struggling prey. The lower jaw contained 22 teeth, and the upper jaw contained 18 teeth. Unlike other sperm whales with functional teeth in the upper jaw, no tooth roots were entirely present in the premaxilla portion of the snout, and, consequently, its tooth count was lower than those sperm whales. Aside from the modern Kogia sperm whales, it has the lowest tooth count in the lower jaw of any sperm whale.[1][8]

The most robust teeth were the fourth, fifth, and sixth teeth in each side of the jaw. The well-preserved teeth all had a height greater than 31 cm (12 in), and the largest tooth of the holotype was the second and third on the left lower jaw, which was calculated to be around 36.2 cm (14.3 in) high. The first right tooth was the smallest at around 31.5 cm (12.4 in). These teeth are thought to be among the largest of any known animal, to the exclusion of tusks,[1][8] and the Beaumaris sperm whale tooth measured around 30 cm (12 in).[11] In comparison, the largest tooth of Tyrannosaurus measured around 30.5 cm (12 in),[13] and the teeth of Megalodon, a large extinct shark, were around 18 cm (7.1 in).[14] Some of the lower teeth have been shown to contain a facet for when the jaws close, which may have been used to properly fit the largest inside the jaw. The tooth diameter decreased towards the base, and the biggest diameters of the teeth were around 11.1 cm (4.4 in). All teeth featured a rapid shortening of the diameter towards the tip of the tooth, which was probably in part due to wearing throughout its life. The curvature of the teeth decreased from front to back, and the lower teeth were more curved at the tips than the upper teeth. The front teeth projected forward at a 45° angle, and, like in other sperm whales, cementum was probably continually added onto the teeth throughout its lifetime.[1][8]

Cast of the skull and teeth at the Museo di storia naturale dell'Università di Pisa

All tooth sockets were cylindrical and single-rooted. The tooth sockets increased in size from the first to the fourth and then decreased, the fourth being the largest at around 197 mm (7.8 in) in the upper jaws, which is the largest of any known whale species. The tooth sockets were smaller in the lower jaw than they were in the upper jaw, and they were circular in shape, except for the front sockets which were more ovular.[1][8]

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 most deep and wide 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, and 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 separates the snout from the rest of the skull, and is defined by a groove starting at the antorbital processes on the cheekbones. The basin had two foramina in the front, as opposed to the modern sperm whale which has one foramen on the maxilla, or to the modern Kogia sperm whales which have several in the basin. The suture in the basin between the maxilla and the forehead had an interlocking pattern.[8]

The supracranial basin suggests that it might have had a large spermaceti organ, a series of oil and wax reservoirs separated by connective tissue. The spermaceti organ could have been used in biosonar to generate sound, as it is in the modern sperm whale, or for ramming. An alternate theory says that sperm whales, including Livyatan, can alter the temperature of the spermaceti in the organ, such that 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.[1][3][8]

Paleobiology

Livyatan probably occupied the same niche as the modern killer whale (Orcinus orca).[1]

Livyatan was an apex predator, and probably had a profound impact on the structuring of Miocene marine communities. Livyatan, using its large and deeply rooted teeth, was likely to have hunted large prey near the surface, and its diet probably was consisted of mainly medium-sized baleen whales. 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 and occupied the same region as Megalodon, which was likely also an apex predator, implying competition over their similar food source.[1][4][15] 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.[1][16] Modern killer whales work in groups to isolate and kill whales, but given its size Livyatan may have been able to hunt alone.[17]

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 for locating prey. It is possible that it was also used as a means of acoustic displays, such as for communication purposes between individuals. An alternate theory is that the enlarged forehead caused by the presence of the spermaceti organ was used between males fighting for females during mating season by head-butting each other. It may have also been used to ram into prey, if this is the case; to support 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 sperm whales. Ramming may have also been used in defense against Megalodon.[1][3]

Palaeoecology

Megalodon (above) and Livyatan were apex predators of the same region.[1] Painting by Karen Carr.

Livyatan is known from the Tortonian stage of the Upper Miocene 9.9-8.9 mya in the Pisco Formation of Peru, which is known for its well-preserved assemblage of marine vertebrates. The formation lies in the subduction zone between the Nazca Plate and the South American Plate, causing numerous pull-apart basins. Among the baleen whales found, the most common was an undescribed species of cetotheriid whale measuring 5 to 8 m (16 to 26 ft), and most of the baleen whales found were roughly the same size. Toothed whale remains found consist of beaked whales (such as Messapicetus gregarius), ancient pontoporiids (such as Brachydelphis mazeasi), oceanic dolphins, and the raptorial Acrophyseter. All seal remains found represent the earless seals. Also found were large sea turtles such as Pacifichelys urbinai, which points to the development of seagrasses in this area. Partial bones of crocodiles were discovered. Of the seabirds, fragmentary bones of cormorants and petrels were discovered, as well as two species of boobies. The remains of many cartilaginous fish were discovered in this formation, including over 3500 shark teeth, which mainly belonged to the ground sharks, such as requiem sharks and hammerhead sharks; and to a lesser extent mackerel sharks, such as white sharks, sand sharks, and Otodontidae. Many shark teeth were associated with the extinct broad-tooth mako (Cosmopolitodus/Carcharodon hastalis) and Megalodon, and the teeth of these two sharks were found near whale and seal remains. Eagle rays, sawfish, and angelsharks were other cartilaginous fish found. Most of the bony fish findings belonged to tunas and croakers. Livyatan and Megalodon were likely the apex predators of this area during this time.[15][18]

The Beaumaris sperm whale was found in the Black Rock Sandstone Formation in Australia near the city of Melbourne, dating to 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, such as from the whale shark (Rhincodon typus), the Port Jackson shark (Heterodontus portusjacksoni), the broad-toothed mako, and Megalodon (Carcharocles 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.[19][20][21][22]

A cooling event at the end of the Miocene, which caused baleen whales to increase in size and decrease in diversity, may have been the cause of the extinction of Livyatan, becoming coextinct with the small baleen whales it fed on. An alternate, though less likely, theory is that it became too big to effectively hunt the smaller creatures it depended on.[1][3][4][5]

In fiction

In the 20th Century Fox animated movie Ice Age: Continental Drift, a 37 m (123 ft) Livyatan with three rows of teeth named "Precious" appears.[23]

References

  1. ^ a b c d e f g h i j k l m n o p q r s t u Lambert, Olivier; Bianucci, Giovanni; Post, Klaas; de Muizon, Christian; Salas-Gismondi, Rodolfo; Urbina, Mario; Reumer, Jelle (2010). "The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru" (PDF). Nature. 466 (7302): 105–108. Bibcode:2010Natur.466..105L. doi:10.1038/nature09067. PMID 20596020.
  2. ^ "Livyatan melvillei". Paleobiology Database. Retrieved 12 November 2017.
  3. ^ a b c d e Fang, Janet (30 June 2010). "Call me Leviathan melvillei". Nature News. doi:10.1038/news.2010.322.
  4. ^ a b c d Ghosh, Pallab (30 June 2010). "'Sea monster' whale fossil unearthed". BBC News. Retrieved 2 July 2010.
  5. ^ a b Sample, Ian (30 June 2010). "Fossil sperm whale with huge teeth found in Peruvian desert". The Guardian. Retrieved 2 July 2010.
  6. ^ Lambert, Olivier; Bianucci, Giovanni; Post, Klaas; de Muizon, Christian; Salas-Gismondi, Rodolfo; Urbina, Mario; Reumer, Jelle (2010). "Corrigendum: the giant bite of a new raptorial sperm whale from the Miocene epoch of Peru". Nature. 466 (1134): 105–108. Bibcode:2010Natur.466.1134L. doi:10.1038/nature09381.
  7. ^ a b Berta, A. (2017). The Rise of Marine Mammals: 50 Million Years of Evolution. Baltimore, Maryland: Johns Hopkins University Press. pp. 112–113. ISBN 978-1-4214-2326-5.
  8. ^ a b c d e f g h i j k l Lambert, O.; Bianucci, G.; de Muizon, C. (2017). "Macroraptorial Sperm Whales (Cetacea, Odontoceti, Physeteroidea) from the Miocene of Peru". Zoological Journal of the Linnean Society. 179: 404–474. doi:10.1111/zoj.12456.
  9. ^ Toscano, A.; Abad, M.; Ruiz, F.; Muñiz, F.; Álvarez, G.; García, E.; Caro, J. A. (2013). "Nuevos Restos de Scaldicetus (Cetacea, Odontoceti, Physeteridae) del Mioceno Superior, Sector Occidental de la Cuenca del Guadalquivir (Sur de España)" [New Remains of Scaldicetus (Cetacea, Odontoceti, Physeteridae) from the Upper Miocene, Western Sector of the Guadalquivir Basin]. Revista Mexicana de Ciencias Geológicas (in Spanish). 30 (2).
  10. ^ Jeffrey, Andy (2016). "Giant killer sperm whales once cruised Australia's waters (and we have a massive tooth to prove it)". Earth Touch News Network. Retrieved 31 May 2016.
  11. ^ a b c "Huge Tooth Reveals Prehistoric Moby Dick in Melbourne". Australasian Science Magazine. Retrieved 24 April 2016.
  12. ^ McSweeney, F.; Buckeridge, J. (2017). The Fossils of the Urban Sanctuary (PDF). Cheltenham, Victoria, Australia: Greypath Productions. p. 62. ISBN 978-1-76056-338-7.
  13. ^ "Sue's vital statistics". Field Museum of Natural History. Retrieved 27 November 2017.
  14. ^ Mustain, A. (2011). "For Sale: World's Largest Shark Jaws". LiveScience. Retrieved 27 November 2017.
  15. ^ a b Bianucci, G.; Di Celma, C.; Landini, W.; Post, K.; Tinelli, C.; de Muizon, C. (2015). "Distribution of fossil marine vertebrates in Cerro Colorado, the type locality of the giant raptorial sperm whale Livyatan melvillei (Miocene, Pisco Formation, Peru)". Journal of Maps. 12 (3): 543. doi:10.1080/17445647.2015.1048315.
  16. ^ Pitman, R. L.; Ballance, L. T.; Mesnick, S. I.; Chivers, S. J. (2001). "Killer Whale Predation on Sperm Whales: Observations and Implications". Marine Mammal Science. 17 (3): 494–507. doi:10.1111/j.1748-7692.2001.tb01000.x.
  17. ^ "New Leviathan Whale Was Prehistoric "Jaws"?". National Geographic. 30 June 2010. Retrieved 3 July 2010.
  18. ^ Parham, J. F.; Pyenson, N. D. (2010). "New sea turtle from the Miocene of Peru and iterative evolution of feeding ecomorphologies since the Cretaceous" (PDF). Journal of Paleontology. 84 (2): 231–247. doi:10.1666/09-077R.1.
  19. ^ "Beaumaris Bay Fossil Site, Beach Rd, Beaumaris, VIC, Australia". Australian Heritage Database. Retrieved 24 November 2017.
  20. ^ Smith, B. (2012). "Trove of ancient secrets submerged under the sea". The Age. Retrieved 24 November 2017.
  21. ^ Long, J. (2015). "We need to protect the fossil heritage on our doorstep". The Conversation. Retrieved 24 November 2017.
  22. ^ "Beaumaris (Miocene of Australia)". fossilworks.org. Retrieved 25 November 2017. {{cite web}}: Italic or bold markup not allowed in: |website= (help)
  23. ^ "Ice Age Movie Characters". Twentieth Century Fox Film Corporation. Retrieved 28 November 2017.
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