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16.12.2015 17:07 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part1 Mammals ch.1 Carnivores - Hyenas,Mustelids,Viverrids
Автор: valentint Категория: Забавление   
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Hyaenidae
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1. Adcrocuta 2. Hyaenictitherium 3. Pachycrocuta 4. Protictitherium 5. Ictitherium
Hyenas originated in the jungles of Miocene Eurasia 22 million years ago, when most early feliform species were still largely arboreal. The first ancestral hyenas were likely similar to the modern banded palm civet; one of the earliest hyena species described, Plioviverrops, was a lithe, civet-like animal that inhabited Eurasia 20–22 million years ago, and is identifiable as a hyaenid by the structure of the middle ear and dentition. The lineage of Plioviverrops prospered, and gave rise to descendants with longer legs and more pointed jaws, a direction similar to that taken by canids in North America.
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The descendants of Plioviverrops reached their peak 15 million years ago, with more than 30 species having been identified. Unlike most modern hyena species, which are specialised bone-crushers, these dog-like hyenas were nimble-bodied, wolfish animals; one species among them was Ictitherium viverrinum, which was similar to a jackal. The dog-like hyenas were very numerous; in some Miocene fossil sites, the remains of Ictitherium and other dog-like hyenas outnumber those of all other carnivores combined. The decline of the dog-like hyenas began 5–7 million years ago during a period of climate change, which was exacerbated when canids crossed the Bering land bridge to Eurasia. One species, Chasmaporthetes ossifragus, managed to cross the land bridge into North America, being the only hyena to do so. Chasmopothertes managed to survive for some time in North America by deviating from the cursorial and bone-crushing niches monopolised by canids, and developing into a cheetah-like sprinter. Most of the dog-like hyenas had died off by 1.5 million years ago.

By 10–12 million years ago, the hyena family had split into two distinct groups: dog-like hyenas and bone-crushing hyenas. The arrival of the ancestral bone-crushing hyenas coincided with the decline of the similarly built family Percrocutidae.
The bone-crushing hyenas survived the changes in climate and the arrival of canids, which wiped out the dog-like hyenas, though they never crossed into North America, as their niche there had already been taken by the dog subfamily Borophaginae. By 5 million years ago, the bone-crushing hyenas had become the dominant scavengers of Eurasia, primarily feeding on large herbivore carcasses felled by sabre-toothed cats.
image One genus, Pachycrocuta, was a 200 kg (440 lb) mega-scavenger that could splinter the bones of elephants. With the decline of large herbivores by the late ice age, Pachycrocuta was replaced by the smaller Crocuta.



The largest h
yaenid of all time was Dinocrocuta gigantea in size: 2.1 m in length, 120 cm in height, 250-300 kg of weight.
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This is a large representative of Percrocutidae with hypertrophied musculature, cupola-like forehead on a massive skull, and massive bone-fracturing teeth. Based on these features, it can be presumed that it fed on carrion and was an aggressive cleptoparasite, i.e. stole other carnivores’ prey.
Modern hyenas have specialized morphological and physiological features which allow them to use effectively the entire corps of an animal when feeding. Their most notable craniodental peculiarities are the firm structure of their jaws and the morphology of their cheek teeth which are functionally differentiated not only for the consumption of soft parts of a corps, but also for fracturing bones. However, studies of hyenas’ behavior indicated that hyenas, although previously considered carrion-eaters, are nevertheless also very successful hunters. Food preferences of fossil carnivorous mammal are less known, but the examination of Dinocrocuta skull’s biomechanics indicated that it possibly was a multi-profile carnivore, capable of attacking large prey independently, as well as steal from other, more effective hunters or feed on carrion.
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Percrocutidae are an evolutionary side line of carnivores, convergently similar to hyenas, but philogenetically very close to Nimravidae and felines. There is still no common opinion as to their origin, although their connection to the Miocene African Viverridae is acknowledged. Progressive forms of Percrocutidae appear in Africa and Eurasia towards the end of the middle Miocene, and their further radiation, according to the current views, occurred in three stages. 16 million years ago, genus Percrocuta emerged, with a number of relatively small species. In Eurasia, this genus had not survived past 13 million years ago.  11.6 million years ago, Percrocuta was followed by genus Allohyaena, together with the giant form of Dinocrocuta whose habitat in Eurasia corresponds to the expansion of hipparion fauna. The third phase is represented by the expansion of habitat of large endemic forms, with their consequent extinction.
It is possible that primitive forms of Dinocrocuta emerged in Western Eurasia and migrated to East Asia and central China via Tibet in the beginning of the late Miocene, prior to the elevation of Tibetan highlands. Much later, these forms evolved into one of the most charismatic fossil animals, Dinocrocuta gigantea, extinct by the end of the Miocene.


Pachycrocuta brevirostris
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Pachycrocuta was a
genus of prehistoric hyenas. The largest and most well-researched species is Pachycrocuta brevirostris, colloquially known as the giant hyena as it is estimated to have averaged 110 kg (240 lb) in weight,almost the size of a lioness or tigress, making it the largest known hyena. Pachycrocuta first appeared during the late Pliocene about 3 million years ago and went extinct during the middle Pleistocene, 400,000 years ago.
Fossil remains have been found broadly in Eurasia and southern and eastern Africa. Most material consists of fragmented remains, usually of the skull, but a cache of very comprehensive bone material was unearthed at the famous Zhoukoudian site, which probably represents the remains of animals using these caves as lairs for many millennia.At the western end of their former range, at Venta Micena in southeastern Spain, a huge assemblage of Pleistocene fossils also represents a den.
Other proposed species, P. robusta and P. pyrenaica, are less well researched; the former may simply be an exceptionally large European paleosubspecies of the brown hyena, Hyaena brunnea. Sometimes included in this genus (as Pachycrocuta bellax) is the extinct giant striped hyaena, Hyaena bellax.
It was probably a small-pack hunter of large animals (up to deer size and occasionally larger). Research by anthropologists Noel Boaz and Russell Ciochon on remains of Homo erectus unearthed alongside Pachycrocuta at the Zhoukoudian site attributed scoring and puncture patterns observed on hominin long bones and skulls—originally thought to be signs of cannibalism—to predation by Pachycrocuta.Pachycrocuta may have also scavenged for food, probably preferentially so, because it was a heavyset animal not built for chasing prey over long distances. In this respect it would have differed from the spotted hyena of today, which is a more nimble animal that, contrary to its image as a scavenger, usually kills its own food but often gets displaced by lions. Apparently it was ecologically close enough to the smaller (but still large) relative Pliocrocuta perrieri that they are never found as contemporary fossils in the same region.


Mustelidae
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1. Sthenictis 2. Baranogale 3. Ekorus 4. Potamotherium 5. Arctomeles
Mustelidae is a diverse family of the order Carnivora, whose extant members typically are characterized by large necks, small heads, short legs, feet with five digits with non-retractile claws, enlarged anal scent glands, the absence of the second upper molar, and the absence of the carnassial notch on the fourth upper premolar. They either have an elongated body with a long tail or a stocky built with short tail. This is the largest family in the order Carnivora, at least partly because it has in the past been a catch-all category for many early or poorly differentiated taxa.As well as one of the most species-rich families in the order Carnivora, mustelidae is considered one of the oldest. Mustelid-like forms first appeared about 40 million years ago, roughly coinciding with the appearance of rodents. The direct ancestors of the modern mustelids first appeared about 15 million years ago.
The evolution of the weasel family could be roughly divided into five phases. After the initial origin of the family, the second phase consists of a rapid diversification of different kinds of mustelid. This takes place during the mid to late Miocene, 11 million years or so ago. It is that time that most of the main groups within the weasel family make their appearance: it is the time of the first Old World badgers, the first marten-like animals, the first otters, and so on. Clearly this was an important stage in the evolution of the family, and is responsible for the wide range of different kinds of animals it currently contains.

The rate of formation of new groups slows down in the third phase, during the late Miocene. Even so, we should see some new forms appearing, often caused by species being isolated on different continents. For example, it"s this time that the researchers suggest the American and Asian otters separated from one another, and that the South American grisons parted company with their Old World kin, such as zorillas.
Things speed up again during the Pliocene, a time of prolonged climate change that altered the environment for many animals. According to the analysis, while individual modern species may not have originated at this time, the evolutionary lines that led to them often did. We"d expect to see the the first American mink, the first clawless otters, the first hog badgers, and maybe the first wolverines appearing at around this time, among others.
The Ice Ages represent the final phase, and the general types of mustelid had all already appeared by that time, leaving only some "fine tuning" as individual populations became isolated by sheets of ice and formed new species. This may have happened, for example, with the closely related pine martens and sables. Perhaps the most significant newcomer they predict at this time would be the appearance of the first polecats.
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Today, the giant otter is the largest of all mustelids, but it isn"t the largest ever to have lived. That honour may go to Enhydriodon, a gigantic species of otter from Africa. Although we only have the skull to go on, if it"s in proportion to the rest of the animal, it may have weighed 100 kg or more when it was alive, making it the size of a small bear. It seems unlikely that it was particularly aquatic at that size, although it may have used rivers as bears do today; it"s also not very clear what it ate. Despite its land-based lifestyle, it"s teeth suggest that it"s closest surviving relative may be the sea otter.


The largest
mustelids of all time was Enhydriodon dikikae - bear otter
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The bones of the enormous otter were found in the 3.2 – 3.4 million year old deposits of Dikika in Ethiopia’s Afar Valley. Among paleontologists, this area is best known for discoveries of early humans – such as the juvenile Australopithecus afarensis named “Selam” – but these rocks have also yielded remains representing other parts of the local fauna. One, a raccoon dog named Nyctereutes lockwoodi, was just described last year, and the otter was another previously-unknown component of the ancient ecosystem.

Described by Denis Geraads, Zeresenay Alemseged, Renй Bobe, and Dennй Reed, the otter has been given the name Enhydriodon dikikae. A partial skull, a portion of the lower jaw, a humerus, and a few femur fragments are all that have been found so far. That is not very much to go on, but the authors of the new paper argue that this otter was quite unusual.
“The most striking feature of the [partial skull] is its very large size,” Geraads and colleagues state, “more suggestive of a bear than of a modern otter.” If Enhydriodon dikikae had a skull proportioned like its living relatives, the whole head would have been nearly ten inches long. This is about three inches longer than the skull of the largest living otter – the appropriately-named giant otter of South America – and may indicate that the bear otter was well over seven feet long.
Exactly how big the whole animal was, though, is difficult to say. No total length estimate was provided, and, based upon comparison of molar size with other otters, the scientists gave a wide weight estimate of about 200 to 400 pounds. More precise estimates of this large otter’s size will have to await further material.
How this otter made its living is also unclear. The authors of the new study suggest that the bear otter was more terrestrial than modern otter species, but their reasoning suffers from two significant flaws. First, citing a 2008 study of fossil otter femurs by paleontologist Margaret Lewis, Geraads and co-authors state that the femur fragments of their new species are anatomically similar to the femur of a large fossil otter found in Hadar, Ethiopia and designated AL-166-10. The femurs from the two species are quite similar, but it actually argues against the bear otter spending more time on land. Lewis found that AL-166-10 possessed features associated with a semi-aquatic lifestyle, perhaps similar to that of living sea otters.
A feature of the bear otter’s humerus was also cited as evidence for a life spent mostly on land. Down near the elbow joint, there is a prominent facet of bone called the medial epicondyle which was an important attachment site for muscles, ligaments, and tendons in the lower arm. In semi-aquatic species like the sea otter and giant otter, this knob of bone is quite large and has a squared-off outline, but the medial epicondyle is relatively reduced in size in the bear otter. Since another fossil otter found in Chad called Sivaonyx beyi also had a relatively small medial epicondyle and was interpreted as spending much of its time on land, Geraads and co-authors infer that the bear otter was “mostly terrestrial.”
The argument that Enhydriodon dikikae was a landlubber is relatively weak. Only one characteristic of the humerus is cited as supporting this conclusion, and the anatomy of the otter’s femur may directly contradict the hypothesis. The details of the otter’s prehistoric environment do not do much to help. Fossils of fish, crocodiles, and hippos are found in the same layers of strata, as well as fully-terrestrial animals. Future fossil discoveries and in-depth study of the otter’s remains may provide a greater degree of resolution about this species and other fossil otters. For now, though, our understanding of otter evolution is frustratingly incomplete. Many prehistoric species are known only from teeth and maybe a few skeletal scraps. As ever, we need more bones.


Megalictis ferox
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Megalictis ferox was a species of large predatory mustelid, now extinct, which existed in North America during the "cat gap" in the Miocene period. It is thought to have resembled a large wolverine, with a length - 1,6 m, tail - 40 cm, height - 50 - 70 сm, weight - 50 - 120 kg.

The genus Megalictis was first described by W. D. Matthew in 1907, and assigned to the family Mustelidae. Two similar genera discovered at the same time, Aelurocyon (Peterson, 1907) and Paroligobunis (Peterson, 1910) were identified as synonymous with Megalictis in 1996. P. R. Bjork, in 1970, assigned the genus to the subfamily Mellivorinae, whilst J. A. Baskin reassigned it to Oligobuninae in 1998. Two other species have been identified in the genus: Megalictis petersoni and Megalictis frazieri, whilst two more, Megalictis brevifacies and Megalictis simplicidens, have since been determined to be synonymous with Megalictis ferox. Other synonyms for the species include Aelurocyon brevifacies, Brachypsalis simplicidens and Paroligobunis simplicidens.
Specimens of the species have been found at ten sites in South Dakota, Nebraska and Wyoming, dated to the Harrisonian period - from 24.8 to 20.6 million years ago. The 19 specimens so far identified have a wide range of sizes, which is believed to be evidence of extreme sexual dimorphism, a phenomenon where males and females of the species will grow to different sizes; a 1996 study rejected the possibility of multiple "morphologically uniform" but differently sized species as unlikely. However, later studies identified significant morphological variation in the joints of the forearms, which would not be consistent with sexual dimorphism. suggests that the identification of all of these as a single species may need revision.
Some writers suggest it could grow to the size of a black bear, whilst others suggest a less exceptional mass of 20–60 kilograms, compared to the wolverine of 10–20 kilograms. Ekorus ekakeran, a comparable mustelid of the same period found in Africa, is estimated to have been around 40 kilograms. Matthew described it as having short stout legs, with short feet and long non-retractible claws, similar to a modern wolverine but about twice the size, and noted that "the teeth indicate an animal fully as predaceous as the wolverine, but the skeleton points to more fossorial habits". Research comparing the joints of the forelegs to modern mammalian carnivores suggests that it waited in ambush and grappled with its prey, rather than hunting it down by pursuit like a modern cheetah.


Ekorus ekakeran

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Ekorus ekakeran is a large extinct mustelid that inhabited late MioceneKenya.
Standing 60 centimeters tall at the shoulders, its build was not similar to that of modern mustelids. Modern-day weasels have short legs and can only achieve short bursts of speed. The legs of Ekorus are built like those of leopards. It appears that before Africa"s big cats ruled the savannas, the giant mustelid Ekorus chased down its prey, such as the three-toed horse Eurygnathohippus and the large pig Nyanzachoerus. The reason for this evolution may be related to the Great Rift Valley. Before the rift opened, Kenya was more forested. Eventually as moisture was drawn from the forests by the highlands, the forests opened up into grasslands. The swifter creatures built for open terrain prospered, while the slower forest species perished.


Giant Raccoon Chapalmalania altaefrontis
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Chapalmalania is an extinct procyonidgenus from the Pliocene of South America, which lived from 5.3 to 1.8 million years ago.

Though related to raccoons and coatis, Chapalmalania was a large creature, reaching 1.5 metres (4.9 ft) in body length, with a short tail. It probably resembled the giant panda. Due to its size, its remains were initially identified as those of a bear. It evolved from the "dog-coati" Cyonasua, which probably island-hopped from Central America during the late Miocene (7.5 million years ago), as perhaps the earliest southward mammalian migrants of the Great American Interchange. When the Isthmus of Panama rose from the sea to allow further invasions by other North American species, Chapalmalania was unable to compete and its lineage went extinct, after being present in South America for 5 million years.


Viverra leakeyi
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Viverra leakeyi, also known as Leakey"s civet or the giant civet, is an extinct species of civet. Its fossils have been found in Africa, from Langebaanweg, Ethiopia, Tanzania, and the Omo Valley.
Being the largest viverrid currently known to ever exist,it grew to about the size of a small leopard, around 40 kilograms (88 lb) and 59 centimetres (23 in) high at the shoulder. V. leakeyi looked physically similar to living Asiatic civet species but is thought to be more closely related to the African Civettictis civetta due to their location.
This civet more than likely was strictly carnivorous as according to the fossil specimens" dentition: in comparison, living civet species are observed to be omnivorous instead. Because of V. leakeyi"s size and dentition, the living animal is thought to be an active predator
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Автор: valentint
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