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17.12.2015 15:58 - Encyclopedia Largest Prehistoric Animals Vol.1 Vertebrates part1 Mammals ch.10 Whales - Giant monster Leviathan and the largest of any marine animal Balaenopter
Автор: valentint Категория: Забавление   
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The largest fossil Odontocete ("toothed whale") was the Miocenephyseteroid whale Livyatan melvillei which was estimated to be between 13.5 and 17.5 meters in length. One notable feature of L. melvillei was its teeth which could exceed 36 cm in length and were unmatched by any other animal, extinct or alive.
Researchers originally assigned the English name of the biblical monster, Leviathan, to this prehistoricwhale 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. 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.
Livyatan melvillei was 13.5 to 17.5 metres (44–57 ft) long, about the same as a modern adult male sperm whale.The skull of Livyatan melvillei is 3 metres (10 ft) long.Unlike the modern sperm whale, Physeter macrocephalus, L. melvillei had functional teeth in both its jaws.The jaws of L. melvillei were robust and its temporal fossa was also considerably larger than in the modern-age sperm whale. 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. 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.Larger "teeth" (tusks) are known, such as walrus and elephanttusks, but these are not used directly in eating.
Two physeterids have been chosen by whale experts for comparison to estimate the size of L. melvillei. The anatomy of Physeter macrocephalus yielded a total length (TL) of 13.5 m (= 44.3 feet) for L. melvillei,and that of Zygophyseter varolai yielded a TL of 17.5 m (= 57.5 feet) for L. melvillei.
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.
Fossil remains of many other animals—including baleen whales, beaked whales, dolphins, porpoises, sharks, sea turtles, seals and sea birds—have been found at the same site where the remains of L. melvillei have been excavated.L. melvillei would have been a top predator of its time along with the giant shark, C. megalodon, which was contemporaneous with L. melvillei in the same region,and the whale probably had a profound impact on the structuring of Miocene marine communities. 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.L. melvillei is likely to have preyed upon 7–10-metre (23–33 ft) baleen whales, seals and dolphins.

Zygophyseter was a raptorial sperm
whale that is sometimes called the "killer sperm whale". Discovered in southern Italy, Zygophyseter is confirmed to have been active in the Paratethys Sea which today is represented by the Mediterranean, Black, Caspian and Aral Seas. However back in the Miocene the sea levels were much higher which means that the Paratehys Sea submerged a much larger area than the these seas do today. This resulted in much of mainland Europe being turned into a chain of islands, with a direct seaway connection between Europe and the Indian Ocean.
Zygophyseter was almost certainly a powerful predator, and had teeth in both the upper and lower jaws. This is a seemingly common trait in large prehistoric predatory whales that has not been passed onto today’s large species like the sperm whale which only has teeth in the lower jaw. The teeth of Zygophyseter were also conical, sharp and rooted deep into the jaw. These are the hallmarks of a predator that tackles large and powerful prey that would damage the jaws and teeth of a lesser hunter.
Study of the skull has also revealed that Zygophyseter had a spermaceti organ, a part that would be filled with oil and wax. The structure of this organ is believed to have provided Zygophyseter with the ability to use echolocation, making prey acquisition much easier. This organ is also what gives modern cetaceans their "domed" or "box-head" head shape, and in Zygophyseter the jaws seem to have extended out from underneath this area giving Zygophyseter a bottlenose appearance.
Zygophyseter was used to work out the size of another but larger predatory prehistoric whale named Livyatan which is known only from a skull.

Brygmophyseter is an extinctgenus of toothed whale in the sperm whale family with one species Brygmophyseter shigensis.
When first described, this species was placed in an extinct form genusScaldicetus of toothed whale, as Scaldicetus shigensis.In 2006, two new genus names were independently created for the species: Naganocetus and Brygmophyseter. Since Brygmophyseter was published first, Naganocetus becomes a junior synonym.
The genus name is a combination of the
Greek word brygmos, which means "biting" or "gnashing", combined with suffix Physeter, which is the generic name of the living sperm whale, and which is also the Greek word for "blower". This has led to the occasional vernacular term "biting sperm whale" being given to the species in popular culture.
The holotype specimen (SFM-0001) was excavated from the Bessho Formation in the
Nagano Prefecture in Japan in 1988 by the residents of Shiga-mura with assistance from the staff of the Shiga Fossil Museum. The specimen is nearly complete and includes a 140 cm (4" 7"" ft) long skull. This specimen came from 15–14 million year old sediments. Unlike the extant sperm whale, Physeter macrocephalus, which has teeth in its lower jaw only, Brygmophyseter has 12 functional teeth on each side of the lower jaws and 12 functional teeth on each side of the upper jaws. The holotype specimen is currently on display in the Gunman Museum of Natural History in Japan.
The holotype specimen is around 7 metres (23 ft) long. However Brygmophyseter have been depicted significantly larger in size – up to 12 metres (39 ft) long.
Brygmophyseter was likely among the apex predators of its time. It packed a formidable jaws armed with teeth up to 14 cm (5.5 inches) long. It may have employed sonar to track prey items in deep waters, like the modern age Sperm Whales. It may also have used its large head to ram a potential opponent during conflict. Brygmophyseter would also have lived in social groups called pods, and probably hunted in packs, like modern age Orcas.
Brygmophyseter is assumed to have preyed upon a variety of animals including fish
pinnipeds, giant squid  and other cetaceans.
It shall be noted that remains of undetermined
mysticeti whales have been found in the same region where the holotype specimen was found however a predator-prey relationship between Brygmophyseter and these whales has not been inferred in the scientific literature.
The shark species
C. megalodon was likely a primary predator of the sperm whales. A large number of cetacean bones have been found with large bite marks (deep gashes) in them, which were caused by teeth that belong to C. megalodon.

However, the largest fossil whales were baleen whales from the Pliocene and Pleistocene Epochs. A notable example is the bones of a Pliocene age baleen whale, assigned the questionable name "Balaenoptera sibbaldina", which likely rivaled the modern blue whale in size.
Van Beneden (1880, p. 15) established this species on an isolated petrosal and some vertebrae from different parts of the axial skeleton. Later, in his monograph Van Beneden (1882) listed and illustrated a partial occipital shield (of a juvenile individual), a right petrosal, an isolated posterior process of the petrotympanic, a partial rib, and isolated thoracic, lumbar, and caudal vertebrae. Because no holotype was designated and the syntypes are almost certainly from different individuals, it is not possible to unambiguously diagnose this taxon. Van Beneden (1880, 1882) aligned (presumably based on size) this fossil species with the extant blue whale (Balaenoptera musculus, known to Van Beneden as Balaenoptera sibbaldus), emphasizing that relationship with a similar specific name. Van Beneden emphasized that he was naming the fossil taxon sibbaldina presumably referring to the similar large size of the fossil and living blue whale.

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