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15.12.2015 17:04 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part1 Mammals ch.1 Carnivores - Saber-toothed cats
Автор: valentint Категория: Забавление   
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Saber-toothed cats
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A saber-toothed cat (alternatively spelled sabre-toothed cat), also misleadingly known as a saber-toothed tiger, is any of various groups of predatory mammals that were characterized by long, curved saber-shaped canine teeth. The large maxillary canine teeth extended from the mouth even closed. The saber-toothed cats were found worldwide from the Eocene epoch to the end of the Pleistocene epoch (42 mya – 11,000 years ago), existing for about 42 million years.
Despite the "cat" in their name, these animals are not closely related to modern cats. These saber-toothed animals belong to three different biological orders: taxa of the order Carnivora, including Machairodontinae from the Felidae (cat) family as well as families Barbourofelidae and Nimravidae from the "cat-like" suborder Feliformia; taxa of the order Creodonta, specifically from genus Machaeroides; and even two families from the extinct order Sparassodonta, from the clade Metatheria which are related to the infraclass of marsupial mammals rather than the placental mammals of the other orders mentioned.

The Nimravidae are the oldest, entering the landscape around 42 mya and becoming extinct by 7.2 mya. Barbourofelidae entered around 16.9 mya and were extinct by 9 mya. These two would have shared some habitats.
These subfamilies evolved their saber-toothed characteristics entirely independently. They are most known for having maxillary canines which were, in some species, up to 50 cm (19.7 inches) long and extended down from the mouth even when the mouth was closed. Sabre-toothed cats were generally more robust than today"s cats and were quite bear-like in build. They were believed to be excellent hunters and hunted animals such as sloths, mammoths, and other large prey. Evidence from the numbers found at La Brea Tar Pits suggests that Smilodon, like modern lions, was a social carnivore.
The first late saber-tooth instance is a group of animals ancestral to mammals but not yet mammals. Known as synapsids or mammal-like reptiles, they were one of the first groups of animals to experience specialization of teeth and many had long canines. Some had two pairs of upper canines with two jutting down from each side, but most had one pair of upper extreme canines. Because of their primitiveness, they are extremely easy to tell from machairodonts. With no cononoid process, many sharp "premolars" more like pegs than scissors and a very long, lizard-like head are among several characteristics that mark them out.
The second appearance of long canines is Thylacosmilus, which is the most distinctive of the saber-tooth mammals and is also easy to tell apart. It differs from machairodonts in a possessing a very prominent flange and a tooth that is triangular in cross section. The root of the canines is more prominent than in machairodonts and a true sagittal crest is absent.
The third instance of saber teeth is from order Creodonta. The small and slender Machaeroides bore canines that were thinner than in the average machairodont. Its muzzle was longer and narrower.
The fourth saber-tooth appearance is the ancient family of carnivores, the nimravids, and they are notoriously hard to tell apart from machairodonts. Both groups have short skulls, tall sagittal crests, and their general skull shape is very similar. Some have distinctive flanges, and some have none at all, so this confuses the matter further. Machairodonts were almost always bigger, though, and their canines were longer and more stout for the most part, but exceptions do appear.
The fifth appearance is the barbourofelids. These carnivores are very closely related to actual cats, and as such, they are hard to tell apart. The best known barbourofelid is Barbourofelis, which differs from most machairodonts by a much heavier and more stout mandible, smaller orbits, massive and almost knobby flanges, and canines that are farther back. The average machairodont had well-developed incisors, but barbourofelids were more extreme.
The sixth and last of the saber-tooth group to evolve were the machairodonts themselves.
1st saber-tooth instance: Synapsida, the gorgonopsid
2nd saber-tooth instance: Thylacosmilidae (Sparassodonta) - Thylacosmilus atrox
3rd saber-tooth instance: Creodonta, family undetermined - Machaeroides
4th saber-tooth instance: Nimravidae (Carnivora)
5th saber-tooth instance: Barbourofelidae (Carnivora)
6th saber-tooth instance: Felidae (Carnivora) - Smilodon
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Many of the saber-toothed cats" food sources were large mammals such as elephants, rhinos, and other colossal herbivores of the era. The evolution of enlarged canines in Tertiary carnivores was a result of large mammals being the source of prey for saber-toothed cats. The development of the saber-toothed condition appears to represent a shift in function and killing behavior, rather than one in predator-prey relations. Many hypotheses exist concerning saber-tooth killing methods, some of which include attacking soft tissue such as the belly and throat, where biting deep was essential to generate killing blows. The elongated teeth also aided with strikes reaching major blood vessels in these large mammals. However, the precise functional advantage of the saber-toothed cat"s bite, particularly in relation to prey size, is a mystery. A new point-to-point bite model is introduced in the article by Andersson et al., showing that for saber-tooth cats, the depth of the killing bite decreases dramatically with increasing prey size. The extended gape of saber-toothed cats results in a considerable increase in bite depth when biting into prey with a radius of less than 10 cm. For the saber-tooth, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "mega herbivores" as previously believed.
A disputing view of the cat’s hunting technique and ability is presented by C.K. Brain in “The Hunters or the Hunted?” in which he attributes the cat"s prey-killing abilities to its large neck muscles rather than its jaws. Large cats use both the upper and lower jaw to bite down and bring down the prey. The strong bite of the jaw is accredited to the strong temporalis muscle that attach from the skull to the coronoid process of the jaw. The larger the coronoid process, the larger the muscle that attaches there, so the stronger the bite. As C.K. Brain points out, the saber-toothed cats had a greatly reduced coronoid process and therefore a disadvantageously weak bite. The cat did, however, have an enlarged mastoid process, a muscle attachment at the base of the skull, which attaches to neck muscles. According to C.K. Brain, the saber-tooth would use a “downward thrust of the head, powered by the neck muscles” to drive the large upper canines into the prey. This technique was “more efficient than those of true cats”.
The similarity in all these unrelated families involves convergent evolution of the saber-like canines as a hunting adaptation. Meehan et a note that it took around 8 million years for a new type of saber-toothed cat to fill the niche of an extinct predecessor in a similar ecological role; this has happened at least four times with different families of animals developing this adaptation. Although the adaptation of the saber-like canines made these creatures successful, it seems that the shift to obligate carnivorism,along with
co-evolution with large prey animals, led the saber-toothed cats of each time period to extinction. As per Van Valkenburgh, the adaptations that made saber-toothed cats successful also made the creatures vulnerable to extinction. In her example, trends toward an increase in size, along with greater specialization, acted as a "macro-evolutionary ratchet": when large prey became scarce or extinct, these creatures would be unable to adapt to smaller prey or consume other sources of food, and would be unable to reduce their size so as to need less food.


Smilodontini
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Smilodontini is an extinct tribe within the Machairodontinae or "saber-toothed cat" subfamily of the Felidae. The tribe is also known as the "dirk-toothed cats". They were endemic to South America, North America, Europe, Asia, and Africa during the Miocene to Pleistocene, from 10.3 mya—11,000 years ago, existing for approximately 10.289 million years.
As the name suggests, the famous genus of Smilodon is part of this group, but there are also three other distinct genera in Smilodontini. The earliest known genus of the tribe is Promegantereon, once thought to be a species of Paramachairodus. The tribe only became extinct 10,000 years ago, with the demise of Smilodon. All of these are saber-toothed cats, meaning that they have long narrow upper canines and stocky, well muscled proportions.
Like all machairodonts, smilodontins were equipped to hunt and kill prey in a manner that was seemingly quicker and more efficient than what is seen in modern cats like the pantherinae. Using their elongated canines, smilodontins would aim for the vital spots of the neck or belly (the exact placement of such bites is still hotly debated among experts), killing either by disembowelment of by severing major arteries such as the carotid. The enlarged carnassials would then be used to shear meat from the bones as the cat fed. In regards to feeding habits, the carnassials of Megantereon suggest that it was a loner that fed at leisurely paces in deep bushes or in trees, while Smilodon on the other end of the spectrum, lived in what was probably a highly competitive environment and in addition, seems to have been social, suggesting a need to eat as much as possible without losing a meal to scavengers.

 
Largest smilodonid and bigest saber-toothed cat was Smilodon populator image

The ever popular “sabertooth tiger”, Smilodon is one of the most famous prehistoric predators, and also one of the most formidable.

There were at least three species living in both North and South America; the smallest species, Smilodon gracilis, was about the size of a modern day jaguar, while Smilodon fatalis was as big as a lion.
However, the South American species Smilodon populator dwarfed both of them, weighing 300 kgs (661lbs) on average and reaching up to 500 kgs (1102lbs) when fully grown!
Smilodon was not as agile as modern day big cats, but it was immensely powerful, with thicker, stronger limbs and neck than modern day cats, and particularly long claws to hold on to prey. Its fangs could reach 30 cms (12″) in length, and were perfect for causing mortal injury to mammoths, ground sloths and possibly any large animal unlucky enough to be ambushed by this super predator.

Smilodon went extinct 10,000 years ago, meaning it encountered humans, and probably hunted them once in a while. But perhaps the most amazing thing about Smilodon, is that it is the only prehistoric cat known to have caused the extinction of an entire species. The victim was another formidable predator, the saber-toothed marsupial or marsupial relative known as Thylacosmilus.
This beast ruled South America for millions of years, until the sea levels became lower and North America became connected to South America.
Smilodon, native to North America, made the journey to South America about 2 million years ago. Thylacosmilus disappeared practically at the same time, outcompeted, and perhaps even, hunted to extinction by the cat. In other words, Smilodon basically conquered an entire continent, driving its less adaptable competitors to extinction, therefore its place as #1 in this list.

Amphimachairodus
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Amphimachairodus is an extinct genus of large machairodonts belonging to the clade known as Eumachairodontia (true saberteeth) along with relatives like Smilodon and Homotherium. It is also a member of the tribe Homotherini within Machairodontidae and is most closely related to such species as Xenosmilus, Homotherium itself, and Nimravides. It inhabited Eurasia, Northern Africa and North America during the late Miocene epoch.
Amphimachairodus was an inhabitant of woodlands and open floodplains as based on finds in Pikermi in Greece and Shanxi Province in China, indicating it had habitat preferences similar to modern lions in many respects. Specimens recovered from Turolian deposits in indicate that the fauna living there was much the same, differing only by species in many cases. Among the creatures it shared its environment were bovids such as Parabos, Lutung monkeys, the mastodon Anancus, the rhino Aceratherium, antelopes such as Tragoportax and Miotragocerus as well as gazelles and deer, a very large species of hyrax, early goats, various girraffes, camels such as Paracamelus, the horse Hipparion, a species of aardvark, the chalicothere ancylotherium and the beaver-like Dipoides. Other carnivores it shared its territory with include the bear Agriotherium, fellow machairodonts Metailurus and Paramachairodus and hyenas like Thalassictis.
The larger herbivores were likely common prey for Amphimachairodus, and it likely have competed with Agriotherium for food, likely having to yield kills to the bear and possibly also stealing kills from hyenas such as Thalassictis and from Metailurus when the opportunity arose.
In North America, in places such as Coffee Ranch in Texas, Amphimachairodus coloradensis shared territory with Agriotherium as it had in Africa and Eurasia, but also shared territory with the feliform Barbourofelis and the canids Epicyon and Borophagus, and herbivores like the camel Aepycamelus, the pronghorn antelope Cosoryx, horses like Neohipparion and Nannippus, the peccary Prosthennops and rhinoceroses like Teleoceras.In the Djurab desert in northern Chad in central Africa, Amphimachairodus kabir co-existed with fellow machairodonts Lokotunjailurus, Tchadailurus and early representatives of the genus Megantereon. In addition, animals such as crocodiles, three-toed horses, fish, monkeys, hippos, aardvarks, turtles, rodents, giraffes, snakes, antelopes, pigs, mongooses, foxes, hyenas, otters, honey badgers and the hominid Sahelanthropus dwelled here, providing ample food. Based on these and other fossils, it is theorized that the Djurab was once the shore of a lake, generally forested close to the waters with savannah-like areas some distance away.The great number of cat species in the environment indicates that there was significant room and available niches for multiple species of large felids to coexist.


Machairodus kabir
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Despite Smilodon’s fame as the classic “sabertooth tiger”, its short tail and different body proportions were very different from an actual tiger.
Machairodus, on the other hand, probably looked pretty much like a gigantic tiger with saberteeth; it had very tiger-like proportions and a long tail, although it is impossible to know if it had stripes, spots or any other kind of fur markings.
Machairodus is seldom mentioned as a giant feline, but some fossil remains found in Chad, Africa, (and classified as a new species, Machairodus kabir), suggest that this creature was among the largest cats of all times- weighing up to 490 (1080lbs) or perhaps 500 kgs (1102lbs), and being “the size of a horse”. It fed on elephants, rhinos and other large herbivores which were abundant at the time.
Machairodus kabir probably looked somewhat like the gigantic “sabertooth tiger” in the film 10.000 B.C, although sadly, it went extinct during the Miocene period, long before the appearance of humans.



Machairodus giganteus
image The largest Machairodus was around 2.5 meters long, 1,3 meters tall at the shoulder.  Weight estimated at up to 320 kg.Machairodus giganteus,the largest species known within the genus Machairodus, was a large lion-sized saber-toothed cat with elongated upper canines and cheek teeth efficiently adapted for slicing meat. The animal is known mostly from a variety of fragmentary fossils found through Europe and Asia, with the best-preserved skulls coming from China. Social behavior is also indeterminable but may have paralleled that in modern feline species. Machairodus giganteus is associated with faunas typical of an open plain environment and may have had a life-style similar to that of a modern lion. Machairodus giganteus could have hunted in large packs or in small groups, maybe mating pairs. Large packs would have been beneficial in bringing down the large prey but would have meant more mouths to feed requiring more time pursuing prey. The array of prey animals available varied in size from creatures larger than buffalo such as large giraffids to medium-sized fast-running antelope. Cooperative hunting would have been more advantageous in capturing both large and small prey, using more muscle to take down the large prey and possibly using more successful ambush tactics for the small prey.

 

Xenosmilus
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Although not as famous as
Smilodon, Xenosmilus was nonetheless an exceptionally powerful Pleistocene era big cat that is estimated to have weighed between 230-400 kg. This estimate puts Xenosmilus within the same weight class as the largest species of Smilodon, and even though it was smaller, Xenosmilus would have been proportionately stronger for its size.
Xenosmilus had been placed within the Machairodontinae group of sabre-toothed cats, mainly because of the large forward canines. However the canines were not as long as they were in other species, although the teeth in general do seem to be more robust possibly indicating that prey was still alive and struggling when they were brought into use. However the immensely powerful build of Xenosmilus meant that it was capable of wrestling almost any prey to the ground with ease, suggesting that teeth breakage would not have to be risked.
Because Xenosmilus has a powerful short legged build associated with the dirk toothed cats combined with broad upper canines as seen in the scimitar tooth cats, its exact classification has been a subject of some confusion. It could be that Xenosmilus displays a link between the two cat groups, or alternatively the features of Xenosmilus are simply a freak case of convergent evolution.
Xenosmilus is estimated to have lived one million years ago during the Calabrian phase of the Pleistocene. However because only the two specimens from the same locale are known, the full temporal range of Xenosmilus in the fossil record cannot be established. However this placement does reveal that potential competition for Xenosmilus could have come from the earlier species of Smilodon,
Dire wolves, and possibly the Dire wolf ancestor, Armbruster"s Wolf.
One of the prey animals chosen by Xenosmilus are peccaries, often referred to as New World Pigs. This is confirmed by the presence of numerous peccary bones found in association with the Xenosmilus remains, and during the Pleistocene peccaries would have provided an abundant food source.

 

Machairodontini
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Machairodontini is an extinct tribe of large saber-toothed cats of the subfamily Machairodontinae, that lived in Europe, Asia, Africa, and North America, during the late middle Miocene through middle Pleistocene.
Previous analysis of the saber-toothed cats used Linnaean classification based the morphology of the upper canines, which suggested that there were four tribes within the subfamily of Machairodontinae.
These tribes include Machairodontini, Homotherini, Smildontini, and Matailurini seen in the cladogram of Machairodontinae. Then upon finding further fossils, Machairodontini was assigned to the Homotherini tribe. The Homotherini includes species such as Machairodus, (M. aphanistus and M. giganteus).
These species are characterized by their scimitar teeth that make up the large upper canines. The Smildontini tribe includes species such as Paramachairodus, Megantereon, and Smilodon. These species have been characterized based on their longer, dagger-like teeth. The other tribe Matailurini includes species such as Matailurus and Dinofelis. These have been classified by having teeth different than the previous two clades, the long serrated teeth and the long, dagger-like teeth. Unfortunately, there are few postcranial skeletons of saber-toothed cats preserved, so available phylogenetic characters are largely cranial.
New research published in 2013 took a different approach to elucidating the evolutionary relationships of saber-toothed cats.This approach used cladistic phylogeny instead of the previous Linnaean classification. The results concluded the original four tribes could not be recovered by parsimony analysis because many of the synapomorphies of the saber toothed cats are based on other bones that the prominent, upper canines.
Workers now regocnize a clade for true saber toothed cats called Eumachairodontia that includes species from all of the previously proposed tribes: Megantereon, Smilodon, Amphimachairodus, Homotherium and Xenosmilus. The synapomorphy for the "true saber-toothed" clade Eumachairodontia is the hypertrophied, greatly flattened upper canines. The true machairodontines have a synapomorphy of flattened, small, lower canines and other bone variations such as the small upper first molar compared to basal, pre-saber toothed cats large, transversely situated upper first molar and large upper third premolar parastyle.
 

Largest species known within the genus Machairodus,was Machairodus horribilis
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A newly described fossil skull from one of the largest of the saber-toothed cats, Machairodus horribilis, is the biggest saber-toothed skull ever found, and is helping scientists understand the diversity of killing techniques used by these extinct and fearsome predators.
Paleontologists Deng Tao, Zhijie Tseng, and colleagues set the record straight in a new paper all about a huge skull of Machairodus horribilis. The fossil, found in the roughly 8.3 million year old rock of China’s Longjiagou Basin, is a little bit crushed. Time and the caprices of geology have squished the cheeks and wide frontal bones of the skull into a much narrower profile. Reconstructed to its shape in life, however, the cream-colored cranium represents a menacingly large sabercat.
The new Machairodus horribilis skull measures over 16 inches long. That’s not only longer than all other known skulls of contemporary sabercats, but also those of the Ice Age celebrities Smilodon and Homotherium. That translates to an estimated body mass of over 892 pounds for this particular Machairodus horribilis, putting it in the same range as the burly Smilodon populator. However you care to slice it, this was one big cat.
And while M. horribilis may have had the biggest skull of the saber-toothed cats, it didn"t necessarily have the biggest bite. When scientists analyzed the skull alongside its saber-toothed cousins, they estimated that it couldn"t stretch its jaws as wide as some of the other extinct cats, which likely affected what type of prey it hunted and how it brought them down.
M. horribilis lived in the steppes and forests of northwestern China during the late Miocene epoch (11.6 million to 5.3 million years ago). The skull"s upper surface measures 1.4 feet (415 millimeters) in length, and likely represents an adult male. Its incisors are arranged in a "gentle arch" and its signature upper canines are serrated on both edges, the study authors wrote.
According to the size of the skull (NWU 48Wd0001), M. horribilis from Longjiagou is estimated to have had a body weight of about 405 kg (893 lbs) as a living animal.
M. horribilis from Longjiagou has the largest skull of any sabertooth cat, but it likely did not exhibit the predatory behavior of derived taxa such as Smilodon or Homotherium, and instead hunted comparatively smaller preys. Derived predatory behaviors apparently have evolved several times independently in sabertooth cats along with changes of habitats and preys through the whole evolutionary history of sabertooth cats (Antуn, 2013), as has clearly occurred in some ungulates, especially tooth crown changes in the family Equidae (Mihlbachler et al., 2011). The mixture of primitive and derived morphological characteristics in the cranium of M. horribilis is consistent with previously observed mosaic evolutionary patterns in early machairodontines, and additionally provides evidence that gigantism may be one of several mechanisms to increase gape prior to the evolution of the full suite of anatomical features associated with more efficient killing bite mechanism (Antуn, 2013). Future discoveries of postcranial elements belonging to M. horribilis would allow these functional morphological interpretations to be further tested.

It would be a mistake to treat Machairodus horribilis just like any other sabercat, though. While the feline shared the long, serrated fangs and other modifications seen in its relatives, for example, Deng and colleagues point out that Machairodus horribilis had a relatively small gape. The cat could only open its mouth about 70 degrees, comparable to what modern lions are capable of, rather than the ludicrous 120 degrees Smilodon could achieve. Along with differences in muscle attachments, the paleontologists write, this means that Machairodus horribilis may have targeted relatively smaller prey than later sabercats tackled.
Machairodus horribilis comes to us, then, as something that was neither like modern cats nor like later sabercats. Its thin canines would have dictated a targeted throat bite, yet the limitations of its muscles and gape likely limited the size of its preferred prey to a narrower range. To cut it short, big predators did not always pounce upon even larger prey.








 

 

 

 

  


 


 




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