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16.12.2015 17:21 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part1 Mammals ch.2 Carnivores - Hyaenodontids and Creodonts
Автор: valentint Категория: Забавление   
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Hyaenodontidae
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1. Thinocyon 2. Megistotherium 3. Hyaenodon 4. Sinopa 5. Tritemnodon
In modern ecosystems, the mammals at the top of the food chain are members of the order Carnivora, such as dogs, cats, and hyaenas. But for the much of the Age of Mammals, carnivorans shared the meat-eating niche with an extinct family of mammals called Hyaenodontidae. Species from this diverse family could be found across Eurasia, North America, and Africa. In Africa, these mammals were the primary predators in the ecosystems where our early ancestors evolved. Despite their carnivorous habits, hyaenodontids might not have been closely related to carnivorans, and their place in the mammalian family tree has not yet been established.
Hyaenodontids of Hyaenodontidae are characterized by long skulls, slender jaws, slim bodies, and a plantigrade stance. They generally ranged in size from 30 to 140 cm at the shoulder.While Hyaenodon gigas was as much as 1.4 m high at the shoulder, 10 feet long and weighed about 500 kg, most were in the 5–15 kg range, equivalent to a mid-sized dog.The anatomy of their skulls show that they had a particularly acute sense of smell, while their teeth were adapted for shearing, rather than crushing.
Because of their size range, it is probable that different species hunted in different ways, which allowed them to fill many different predatory niches. Smaller ones would hunt in packs during the night like wolves, and bigger, fiercer ones would hunt alone during the daylight, using their sheer size and their mighty jaws as their principal weapon. The carnassials in a hyaenodontid are generally the second upper and third lower molars. However, some hyaenodontids possessed as many as three sequential pairs of carnassials or carnassial-like molar teeth in their jaws.Hyaenodontids lacked post-carnassial crushing molar teeth (such as those found in many carnivoran families, especially the Canidae and Ursidae), and thus lacked dental versatility for processing any foods other than meat.
Hyaenodontids are very unusual in regards to their tooth replacement. Studies on Hyaenodon show that juveniles took 3–4 years in the last stage of tooth eruption, implying a very long adolescent phase. In North American forms, the first upper premolar erupts before the first upper molar, while European forms show an earlier eruption of the first upper molar.
At least one hyaenodontid lineage, Apterodontinae, was specialised for aquatic, otter-like habits.
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Having evolved in Africa during the Paleocene,hyaenodontids soon after spread into India and Europe, implying close biogeographical connections between these areas.Afterwards they dispersed into Asia from either Europe or India, and finally North America.
They were important hypercarnivores in Eurasia, Africa and North America during the Oligocene, but gradually declined, with almost the entire family becoming extinct by the close of the Oligocene. Only four genera, Megistotherium, its sister genera Hyainailouros and Dissopsalis, and the youngest species of Hyaenodon, H. weilini, survived into the Miocene, of which, only Dissopsalis survived long enough to go extinct at the close of the Miocene.Traditionally this has been attributed to competition with carnivorans, but no formal examination of the correlation between the decline of hyaenodontids and the expansion of carnivorans has been reccorded, and the latter may simply have moved into vacant niches after the extinction of hyaenodontid species.


The largest hyaenodontid was
Simbakubwa kutokaafrika
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Simbakubwa kutokaafrika ("great lion from Africa") is an extinct species of mammal of the family Hyainailouridae in the order Hyaenodonta. It lived during the early Miocene and was found in Kenya. The type specimen was recovered from deposits dated to be 23 million years old. Possibly reaching up to 1,500 kg, it might have surpassed the modern polar bear in size. The fossils of Simbakubwa were first discovered by Matthew Borths and Nancy Stevens when they were examining fossils stored at the Nairobi National Museum in Kenya. The type specimen consists of a mandible from the lower jaw, a right upper maxilla and some post cranial remains. The light wear patterns on the dentition indicate that the holotype specimen was a young adult at the time of its death.From most of a jaw, parts of a skull and some bits of skeleton, the researchers were able to identify and name a species new to science: Simbakumba (Swahili for "big lion") Kutokaafrika ("from Africa"). These huge carnivores stood more than five feet (1.5 m) tall on four legs, weighed anywhere up to 3,300 lb (1,500 kg), and were one of the final examples of a family of mammalian carnivores called hyaenodonts that were Africa"s apex predators for about 45 million years.The study of the postcranial remains indicates Simbakubwa was possessed of a semi-digitigrade walking stance. Simbakubwa, like other hyainailourids, probably was a specialist hunter and scavenger that preyed on creatures such as rhinoceroses and early proboscideans. It may have been somewhat less specialized in crushing bone than its later relatives such as Hyainailouros. However, like Hyainailouros, Simbakubwa possessed lingually rotating carnassial blades, ensuring a constant shearing edge throughout its life.
Simbakubwa and other giant hyaenodonts, such as Megistotherium, were a very different form of carnivore from their modern brethren. Whereas modern carnivores have a single row of back teeth that are arranged to chew meat, hyaenodonts had three sets of meat-slicing teeth. All those extra blades gave them a relatively long jaw that made their heads look a little too big for their bodies,looking a bit like the wargs from Lord of the Rings.”



Yet another possible contender for the title is Megistotherium at 1000 kg

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Megistotherium (from Greek, megistos "greatest" + therion "beast" and osteon "bone" + thlaston "crushed, bruised" with -es being an agent noun: "bone-crusher") is an extinct genus of creodonts, the only known species of which is Megistotherium osteothlastes It is most likely a junior synonym of Hyainailouros sulzer.

Megistotherium osteothlastes was a large hyaenodontid creodont that lived during the early Miocene epoch some 23million years ago. Its remains have been found in the Ngorora and Muruyur Formations of Kenya, Egypt Namibia, Uganda and Libya.
Named by Robert Savage in 1973, it is one of the largest terrestrial carnivorous mammals known to have existed. It was about 1.5 meters high at the shoulders and 3.5 meters in head and body length, with a 1 meter long tail and a 65 cm long skull. Its body mass has been estimated at 500 kg or 880 kg.
This can be compared to the other large carnivorous mammals such as: Arctodus, modern polar bears, and Amphicyon ingens.
Large hyaenodontids like this one could have originally evolved as specialized predators or scavengers of large African herbivores. Mastodon bones have been found with its fossils, indicating that Megistotherium may have hunted them for food.
The carnassial teeth of Megistotherium (like those of other creodonts) were the upper first molars, and overlapped with their lower molar counterparts like scissors to form a formidable and powerful shearing action. The land that is now the Sahara desert was much more fertile in the Miocene. A considerable amount of it was grassland and rainfall was plentiful. Lakes and ponds provided water for large fauna, which provided Megistotherium and other predators with an ample supply of prey. Large hyaenodontids like this one could have originally evolved as specialized predators or scavengers of large African herbivores Gomphothere bones have been found with its fossils, indicating that Megistotherium may have hunted them for food.

The order Creodonta comprised a diverse group of predators that were most successful during the Eocene before being ecologically displaced by the order Carnivora during the late Oligocene. Megistotherium emerged in the Miocene towards the end of the creodents" flourishing; it was a part of a radiation of African hyaenodontids that occurred at that time. Hyainailouros sulzeri is very closely related to Megistotherium, extremely similar in size, structure and ratios - with a long tail, short limbs and robust body. Morales & Pickford (2005),Morlo, Miller & El-Barkooky (2007)and Morales, Pickford & Salesa (2008) suggested that Megistotherium is actually a junior synonym of Hyainailouros sulzeri, which is known by an almost complete skeleton, among other remains, and has been found in Europe, Asia and Namibia, and therefore comes from the same localities.

 

Hyainailouros sulzeri
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Hyainailouros sulzeri
was an enormous hyaenodontid creodont that lived during Miocene Epoch some 23- 12 million years ago. It has been found in Europe (France and Portugal) and Africa (Namibia and Egypt). Hyainailouros sulzeri  it is one of the largest terrestrial carnivorous mammals known to have existed. It was about 1.3 meters high at the shoulders and 3 meters in head and body length, with a 1 meter long tail and a 66 cm long skull. Its body mass has been estimated at 400 kg or 500 kg.

This can be compared to the other large carnivorous mammals such as: Arctodus, modern polar bears, and Amphicyon ingens.
Large hyaenodontids like this one could have originally evolved as specialized predators or scavengers of large African herbivores. Mastodon bones have been found with its fossils, indicating that may Hyainailouros sulzeri have hunted them for food.


Hyaenodon gigas

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Hyaenodon gigas was a genus of the family Hyaenodontidae from the middle Eocene-early Miocene of Europe, Asia and North America. Members of the genus differ considerably in size and occupied various niches of terrestrial predators. The earliest known H. gigas found in Asia and dating to the late. During the second half of the Eocene epoch, it settled across the northern hemisphere, often occupying released Endangered Oxyacids of the ecological niches. They have become quite common in much of Asia, North America and Europe, but Africa somehow passed. It may seem that it outwardly resembled several modern members of the family of the caninae, although in reality they are far from their peers. This race is much more united in a variety of animals who have held a variety of niches with predators of the land.
The largest of the genus Hyaenodon gigas,
being 500 kilograms (1,100 lb) and around 10 feet (3.0 m) long, and the length of the head reaches 50 cm or more. It supported a heavy head which is rather short and had a very strong neck, which was needed to keep caught up with its teeth and break out the victim. Their prey, like the modern dogs, were grabbed by a toothy mouth (and not as a cat, like claws and teeth).
The larger members of the genus are relatively long and have slender limbs, based on several fossils in the parts of the fingers, and apparently adapted to the active movement on hard ground. With moving the hind limbs, this species of Hyaenodon could make sharp throws for prey, and the front may have been needed to cope with food until it got to fall.
Very likely that these predators were digging with its front paws on the ground, looking for small animals that live in burrows or holes which arranged themselves.
With a rather massive addition, H. gigas probably would not have been able to do a long run. Rather, they were ambush predators, briefly, but actively pursuing prey, so does about most of today"s large and small cats. There is no doubt that H. gigas was able to catch, throw and cut a relatively large animal with its powerful hunting abilities including sharp canine teeth for biting the victims neck after leaping onto it and pushing it onto the ground.

 

Oxyaenidae
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1. Palaeonictis 2. Sarkastodon 3. Apataelurus 4. Patriofelis 5. Oxyaena
Oxyaenidae is a family of carnivorous mammals. Traditionally classified in Creodonta, this group may be related to pangolins.The group contains four subfamilies comprising thirteen genera.North American oxyaenids were the first creodonts to appear during the late Paleocene, while smaller radiations of oxyaenids in Europe and Asia occurred during the Eocene.They were superficially cat-like beasts that walked on flat feet, in contrast to modern cats, which walk or run on their toes. Anatomically, characteristic features include a short, broad skull, deep jaws, and teeth designed for crushing rather than shearing, as in the hyaenodonts or modern cats.
Oxyaenids were specialized carnivores that preyed on other terrestrial vertebrates, eggs and insects. They were capable of climbing trees, which is suggested by fossil evidence of their paws.


The largest
creodont was Sarkastodon
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The largest creodont and oxyaenid was Sarkastodon weighting at 800 kg. Sarkastodon is an extinctgenus within the family Oxyaenidae that lived during the upper Eocene, approximately 35 million years ago. It was a large, carnivorous animal that lived in what is today Mongolia. Sarkastodon is known only from a skull and jawbones. Sarkastodon, like creodonts in general, was probably a hypercarnivore that preyed on large mammals in its range during the Late Eocene, such as brontotheres, chalicotheres,and rhinoceroses
The type specimens of S. mongoliensis are known from Eocene deposits from the Irdin Manha Formation of Mongolia. Additional material referred to Sarkastodon is known from the Ulan Shireb beds (100 miles away from the holotype locality) of Inner Mongolia. These specimens were discovered by Dr. Garber in 1930, on an expedition to the Gobi Desert
Sarkastodon was a hypercarnivore, with hyaena-like dentition specialised in bone-cracking. The sharp, slicing premolars (which form roughly rectilinear cutting blades) and crushing molars enabled Sarkastodon to eat both bone and flesh.


  










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