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17.12.2015 14:31 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part1 Mammals ch.8 Entelodonts and Pigs
Автор: valentint Категория: Забавление   
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Entelodonts
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Entelodonts (properly Entelodontidae) have generally been regarded as suiforms (close kin to pigs and peccaries) but some recent analyses have found the sampled members of the group to be members of the hippo + cetacean clade Cetancodontamorpha and hence fairly well removed phylogenetically from pigs and peccaries. Andrewsarchus, the famous Eocene giant predator or omnivore so often regarded as a mesonychian (or mesonychid), seems to be a cetancodontamorphan close to entelodonts.
Fossil evidence points to their emergence in the Middle Eocene (some 49 million to 37 million years ago) of Mongolia. They spread across Asia, Europe, and North America before becoming extinct sometime between 19 million and 16 million years ago during the early Miocene Epoch.
Entelodonts were medium-size to very large animals. The smallest ones grew to about 150 kg (about 330 pounds; the size of a large male white-tailed deer), whereas the largest ones, such as Dinohyus, weighed 900 kg (about 2,000 pounds; roughly the size of a Clydesdale horse). The skulls of entelodonts were also proportionally large, accounting for about 35 to 45 percent of the animal’s total length in Dinohyus. Entelodonts had distinctive tusklike projections of bone that grew out from the skull. These structures were related to the musculature and movements of the jaw during feeding, and they also might have protected sensitive areas of the head.
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Currently known entelodonts first appear around the Lutetian period of the Eocene with genera such as Brachyhyops. This genus is known from North America, though another genus from China called Eoentelodon has been speculated to be a synonym to Brachyhyops. This blurs the point of origin theory for entelodonts to possibly be Asia, though it’s perfectly possible that entelodonts could cross between Asia and North America over a land bridge that existed between these two continents at this time called Beringia. As such the precise point of origin for entelodonts remains uncertain, though future discoveries may help to clarify the issue.
During the late Eocene and Oligocene eras entelodonts seem to have been at their most numerous in terms of different genera. In addition they are known to have ranged across Eurasia and North America. However by the early Miocene entelodonts were on the decline and currently the latest known remains are dated to around the Burdigalian stage of the Miocene. This disappearance seems to have been global all at once with Burdigalian era remains being attributed to Asian and North American genera.
The popular conception of entelodonts regarding their size is that the earlier genera were small while the later genera grew larger, a pattern that is repeated in most animal groups. To an extent this is true for entelodonts since two of their largest genera (Paraentelodon and Daeodon) are known from Late Oligocene to early Miocene deposits. However to contradict this claim the type genus of the Entelodotnidae Entelodon is of a large size almost as big as these two later genera, yet Entelodon is dated farther back to the late Eocene to early Oligocene. This clearly indicates that even at this earlier stage in the entelodont timeline, there was still a niche for an exceptionally large genus.
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This in turn could indicate that entelodonts evolved from more moderately to larger sized ancestors, they could quickly alter in terms of size of successive generations to even the possibility that we have yet to find the earliest entelodont ancestors. If the latter is true then future discoveries of entelodonts might be yielded from the earliest Eocene to possibly even the late Paleocene. Shifting to the other end of the scale and it’s not completely out of the question that entelodont fossils may one day be discovered later into the Miocene.



Paraentelodon
was the largest entelodont that ever lived,at around 2 meters tall,3.3 m long and weight 1000 kg
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Although not especially one of the most well-known of the entelodonts, Paraentelodon is one of the largest known genera being comparable to Entelodon and Daeodon in size. Paraentelodon appears in Asia as the earlier Entelodon began to decline and continues to be largest currently known genus of entelodont in Asia in the early stages of the Miocene. Daeodon also seems to have held a similar ecological niche as Paraentelodon during the early Miocene, but is so far only known from North America.
The exact diets of entelodonts have always been subjects of debate for palaeontologists because although they may have been capable of eating plants, the larger ones such as Paraentelodon may have used their large size to either kill other animals or intimidate other predators into giving up their kills.



Another close contender was
Daeodon
was at 12 ft long and 7 ft at the shoulder.
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Daeodon (from Greek or "dreadful", and οδον, odon "teeth") is an extinctgenus of entelodontartiodactyl that inhabited North America between 29 to 19 million years ago during the late Oligocene and early Mioceneepochs. The type species is Daeodon shoshonensis, the last and largest of the entelodonts, known adults of this species possess skulls about 90 cm (3 ft) in length. It had a broad distribution across the United States but it was never abundant.
Although not specified in Cope"s original description, the name Daeodon comes from the Greek words daios, meaning "hostile" or "dreadful" and odon, meaning "teeth".
The genus Daeodon was erected by the American anatomist and paleontologist Edward Drinker Cope in 1878. He classified it as a perissodactyl and thought that it was closely related to "Menodus". This classification persisted until the description of "Elotherium" calkinsi in 1905, a very similar and much more complete animal from the same rocks, which was promptly assigned as a species of Daeodon by Peterson (1909). This lead to Daeodon"s reclassification as a member of the family Entelodontidae. The exact relationships between Daeodon and other entelodonts are not well understood, some authors (Lucas et al., 1998) consider the greater morphological similarity of Daeodon to Paraentelodon rather than to earlier North American entelodonts, like Archaeotherium, as evidence for Daeodon being a descendent from a Late Oligocene immigration of large Asian entelodonts to North America However, the existence of distinct specimens of Archoetherium showing characters reminiscent of those present in both Paraentelodon and Daeodon raises the possibility of both genera actually being descended from a North American common ancestor.
The type species of Daeodon is D. shohonensis, which is based on a fragment of a lower jaw from the John Day Formation of Oregon. Several other species were assigned to the genus in the subsequent decades, like D. calkinsi, D. mento and D. minor. Since 1945, it had been suggested that two other taxa were actually junior synonyms of Daeodon, but the formalization of this referral didn"t take place until the work of Lucas et al. (1998). Ammodon leidyanum, named by Cope"s rival, O. C. Marsh, and Dinohyus hollandi, a complete skeleton from the Agate Springs quarry of Nebraska, were found to be indistinguishable from each other and in turn both were indistinguishable from D. shoshonensis. With the exception of D. calkinsi, which was tentatively excluded from Daeodon, the other previously recognized species of Daeodon were also synonymized to D. shoshonensis. That same year, an obscure entelodont, Boochoerus humerosum, was also synonymized to Daeodon by Foss and Fremd (1998) and, albeit its status as a distinct species was retained, they note that the differences could still be attributed to individual or population variation or sexual dimorphism.
Daeodon shoshonensis is one at the largest known entelodont; known adult individuals had skulls about 90 cm (3 ft) long and were around 1.8 m (6 ft) tall at the shoulders. It"s differentiated from other entelodonts by a suite of unique dental characters, the shape and relatively small size of the cheekbone flanges of its skull compared to those of Archaeotherium, the small size of its chin tubercle, as well as features of its carpus and tarsus and the fusion of the bones of the lower leg. Like other entelodonts, its limbs were long and slender with the bones of the foreleg fused together and with only two toes on each foot. It also had a relatively lightly constructed neck for the size of its head, whose weight was mostly supported by muscles and tendons attached to the tall spines of the thoracic vertebrae, similar to those of modern day bison and white rhinoceros.


Entelodon
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Entelodon (meaning "complete teeth", from Ancient Greek entelēs "complete" and odōn "tooth", referring to its "complete" eutherian dentition is an extinct genus of entelodontartiodactyl endemic to Eurasia. Fossils of species are found in Paleogene strata ranging in age from the Houldjinian (37.2–33.9 mya) until the Rupelian epoch of the early Oligocene (33.9–28.4 mya). Entelodon was a fairly typical entelodont, with a large, bulky body, slender legs, and a long snout.
Like other entelodonts, Entelodon had complete eutherian dentition (3 incisors, 1 canine, 3 premolars, and 3 molars per quadrant). It had only two toes on each foot, and its legs were built for fast running. Its long, wide head was supported by a robust, short neck and its cheekbones were greatly enlarged and protruded noticeably from the sides of the head. Though it was more closely related to hippos and whales than pigs, its skull was generally pig-like. It is presumed to have been an omnivore.
Entelodon was around 1.35 m (4.4 ft) tall at the shoulders, with a 65 cm (2 ft 2in) skull.


Suidae
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The Suidae are a widespread family of Cetartiodactyla that originated in the Oligocene at least 20 million years ago (Ma). They last shared a common ancestor with the Tayassuidae (New World Suiodae) during the late Eocene/early Oligocene. The Suidae family has been extremely success- ful, having colonized the African and Eurasian continents. Given the diversity of fossil Suidae in Eurasia and Africa, they have been used as a stratigraphic dating tool for decades.This diversity is still apparent today, and the family is composed of a minimum of five extant genera made up of 17 species in Africa and Eurasia. The success of these species is evident in the multitude of habitats in which they are found, including tropical Island Southeast Asia (ISEA); the high plateau of the Himalayas; and the diverse environments of Siberia, central and western Eurasia, and North Africa.
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A, Platgonus (late Pleistocene); B, Mylohyus sp. (late Pleistocene); C, Chacoan peccary (living); D, white-lipped peccary (living), E, collared peccary (living)
Morphological and molecular analyses of these species have revealed numerous aspects of their biology, including both their speciation and the ease with which many lineages have and continue to hybridize. This trait has made them an ideal model for evolutionary biologists, though it has also complicated the identification of taxonomic species.Lastly, suid species have had a long shared history with humans, from their association with early hominids in Africa, to their domestication (that today makes them a prime source of protein for billions of people), to their modern use as a biomedical model.

 

The largest wild suid to ever exist was Megalochoerus homungous
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Dimensions: length - 380 cm, height - 180-220 сm, weight ~1600 kg 
Megalochoerus is an extinct genus of large and long-legged animals in the pig family from the Miocene of Africa. The suid species Kubanochoerus khinzikebirus and K. marymuunguae are now assigned to Megalochoerus. The largest species - Megalochoerus homungous.
New collections of suoids from Gebel Zelten,although limited in quantity, are interesting because they contain the first known snout of the giant kubanochoere Megalochoerus khinzikebirus, hitherto represented only by a maxilla fragment, a mandible and some isolated teeth. Comparisons can thus be made with Libycochoerus massai and Kubanochoerus gigas of which more complete material has been described. These three genera are basically similar in snout morphology, but there are differences in position of the incisive foramina and in premolar proportions, the largest species having relatively and sometimes absolutely smaller anterior premolars than the smaller species.
The species Megalochoerus khinzikebirus is known from Cheparawa, Kenya, aged 14.5 Ma,(Pickford, 2001) and the larger species M. homungous occurs in deposits at Nyakach, Kenya,(Pickford, 1993) aged about 14 Ma. Undescribed material of this species is known from Nachola,Kenya, aged 16 Ma, and Kipsaraman, Kenya, aged 14.5 Ma. The Gebel Zelten specimens attributed to M. khinzikebirus, thus suggest an age of between 16 and 14 Ma for the deposits from which they came,the larger specimens favouring the younger end of this time span.All the Kenyan fossils attributed to Megalochoerus khinzikebirus and M. homungous, came from deposits that accumulated in well wooded to forested palaeoenvironments. It is likely that Gebel Zelten would have been equally well wooded to forested at the time of deposition. The bunodont nature of the cheek dentitions of these kubanochoeres, which are superficially similar to those of bunodont gomphotheres in terms of their functional morphology, suggests that Megalochoerus was probably an omnivore, concentrating on fruits, leafy branches, and tree bark, but avoiding underground food resources and grass. The transversely arranged, massive upper central incisors in particular,suggest that tree bark may have been an important food resource in this lineage.



Kubanochoerus gigas
, having measured up to 550 kg (1,210 lb) and stood more than 1.3 m (4.3 ft) tall at the shoulder.

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The largest species, the aptly named K. gigas, grew to be up 1.2 metres (3.9 ft) at the shoulder, and probably weighed up to 500 kilograms (1,100 lb) in life. The heads of these pigs were unmistakable, with small eyebrow horns, and a large horn emanating from the forehead of the males. It is speculated that the males used their forehead horns for jousting with each other. The species K. massai was originally thought to be an African species belonging to this genus, as the first specimen shared the genus" distinctive eyebrow horns. Its lack of a forehead horn lead experts to interpret the skull as belonging to a female. However, recently, K. massai has been split off into its own genus, Libyochoerus (commemorating the fact that it was originally found in Libya.) Some species of the genus Megalochoerus have been also reassigned to Libyochoerus, though, many experts do not agree with this.


Notochoerus

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Notochoerus is an extinct genus of very large pig-like animals from the subfamily Tetraconodontinae. Fossils have been found in Africa, notably Uganda and Ethiopia.Notochoerus were among the largest pigs ever, with adults weighing up to 450 kg (990 lbs).These pigs were likely derived from the genus Nyanzachoerus. Like other tetraconodontine pigs, the males had ornamental growths on their skulls, formed from enamel. This was a large pig, larger than living species.Fossils of males of these species show that they had large lumps on their muzzle and widely flaring cheekbones. Their tusks were only of moderate size. It can be assumed that the ornaments were used as a mating display.















 




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