Attempted extended overview of the largest ever lived animals.Codex consists of collected and processed by me but written by other authors articles. Full overview of vertebrates including the latest paleontological finds. Because of the volume "ve split up. I begin with predatory mammals because these are my favorites.Individual parts are numbered according to their place in the full collection Proceedings in English in order to reach the maximum number of readers.And to preserve the style of the authors.
Опит за разширен обзор на най-големите,живели някога животни.Сборника се състои от събрани и обработени от мен,но написани от други автори статии.Пълен обзор на гръбначните животни,с включване най-новите палеонтологични находки.Заради обема съм го разделил на части.Започвам с хищните бозайници,защото това са моите фаворити.Отделните части са номерирани според мястото си в пълния сборник.
Bears
Arctotherium
The largest terrestrial carnivoran and the largest bear as well as the largest mammalian land-predator of all time was Arctotherium angustidens of the genus Arctotherium or the South American short-faced bears. A humerus of A. angustidens from Buenos Aires indicate that the big males of this species would have weighed 1,588- 1,749 kg and standing at least 11 feet (3.4 meters) tall on the hind-limbs.Arctotherium angustidens was a South-American Short Faced Bear from the genus Arctotherium. It was the largest Carnivoran that ever lived, in most regards; although male southern elephant seals can be heavier, they are semi-aquatic and covered in a layer of blubber.
A. angustidens was the largest Carnivoran that ever lived except that for southern and northern elephant seals. The northern elephant seal was 3,700 kg (8,200 lb) while the southern elephant seal was 5,000 kg (11,000 lb). It weighted about 983–2,042 kg (2,167–4,502 lb) but the authors said it was more likely 1,588 kg (3,501 lb) Arctotherium is an extinct genus of South American short-faced bears within Ursidae of the Pleistocene. Their ancestors migrated from North America to South America during the Great American Interchange, following the formation of the Isthmus of Panama during the late Pliocene. The oldest remains are from the Ensenadan epoch within the early-middle Pleistocene 1.2 Mya. Their closest relatives were the North American short-faced bears of genus Arctodus (A. pristinus and A. simus). The closest living relative would be the spectacled bear (Tremarctos ornatus)
Arctotherium was named by Hermann Burmeister in 1879. It was assigned to Tremarctinae by Krause et al. 2008. A specimen of A. angustidens from Buenos Aires shows an individual estimated, using the humerus, to weigh between 983 and 2,042 kg (2,167 and 4,502 lb), though the authors consider the upper limit as improbable and say that 1,588 kg (3,501 lb) is more likely. It is still possibly the largest bear ever found and contender for the largest carnivorous land mammal known to science. In contrast to their North American relatives, South American short-faced bears showed a trend of declining size and carnivory over time. This has been attributed to increased competition from other, later-arriving or evolving carnivorans, like jaguars, lions or Smilodon populator, following the early dispersal of short-faced bears to South America. (The North American carnivorans that invaded South America, including short-faced bears and Smilodon, quickly dominated the predatory niches formerly occupied by South America"s native metatheriansparassodont and avian phorusrhacid carnivores.)
North American short-faced bear (Arctodus simus)
The short-faced bear (Arctodus spp.) is an extinct bear that inhabited North America during the Pleistocene epoch from about 1.8 Mya until 11,000 years ago. It was the most common early North American bear and was most abundant in California. There are two recognized species: Arctodus pristinus and Arctodus simus, with the latter considered one of the largest known terrestrial mammalian carnivores.
The name short-faced bear derives from the shape of their skulls, which appear to have a proportionally short snout compared to other bears; this characteristic is also shared by its extant relatives, the spectacled bear and the grizzly bear. However, this apparent shortness is an optical illusion caused by their deep snouts and short nasal regions. The scientific name of the genus, Arctodus, derives from the Greek language and means "bear tooth".
The short-faced bear belongs to a group of bears known as the Tremarctinae, which appeared in the Americas during the earliest parts of the late Miocene epoch in the form of Plionarctos, a genus considered ancestral to Arctodus, Arctotherium and the modern spectacled bear (Tremarctos ornatus). Although the early history of Arctodus is poorly known, it evidently became widespread in North America by the Kansan age about 800,000 years ago.
Arctodus simus first appeared during the middle Pleistocene in North America, about 800,000 years ago, ranging from Alaska to Mississippi, and it became extinct about 11,600 years ago. Its fossils were first found in the Potter Creek Cave, Shasta County, California. It might have been the largest carnivorous land mammal that ever lived in North America. Only one Giant Short-faced Bear skeleton has been found in Indiana, unearthed south of Rochester on west of Nyona Lake on Chet Williams" farm. It has become well known in scientific circles because it was the biggest most-nearly complete skeleton of a giant short-faced bear found in America. The original bones are in the Field Museum, Chicago. The new Indiana State Museum, Indianapolis, and the Yukon Beringia Interpretive Centre, Whitehorse, Yukon Territory, Canada, have casts made of the bones. In a recent study, the mass of six specimens was estimated, one-third of them weighed about 900 kg (1 short ton), the largest being UVP 015 at 957 kg (2,110 lb), suggesting specimens that big were probably more common than previously thought. It stood 8–10 feet (2.4–3.0 m) tall on hind legs while a large specimen would have been 11–12 feet (3.4–3.7 m) tall with a 14 foot (4.3 m) vertical arm reach, and 5–6 feet (1.5–1.8 m) high at the shoulder when walking on all fours, it was tall enough to look a man in the eye. At Riverbluff Cave, Missouri, a series of claw marks up to 15 feet (4.57 m) high have been found along the cave wall indicating Short-faced bears over 12 feet (3.65 m) tall.
Arctodus pristinus inhabited more southerly areas, ranging from northern Texas to New Jersey in the east, Aguascalientes, Mexico to the southwest, and with large concentrations in Florida, the oldest from the Santa Fe River 1 site of Gilchrist County, Florida paleontological sites.
Researchers disagree on the diet of Arctodus. Analysis of their bones showed high concentrations of nitrogen-15, a stable nitrogen isotope accumulated by meat-eaters, with no evidence of ingestion of vegetation. Based on this evidence, A. simus was highly carnivorous and as an adult would have required 16 kg (35.3 lb) of flesh per day to survive.
One theory of its predatory habits envisages A. simus as a brutish predator that overwhelmed the large mammals of the Pleistocene with its great physical strength. However, despite being very large, its limbs were too gracile for such an attack strategy. Alternatively, long legs and speed (50–70 km/h (30–40 mph)) may have allowed it to run down Pleistocene herbivores, such as wild horses and saiga antelopes, in a cheetah-like fashion. However, in this scenario, the bear’s sheer physical mass would be a handicap. Arctodus skeletons do not articulate in a way that would have allowed for quick turns, an ability required of any predator that survives by killing agile prey. Paul Matheus, paleontologist at the University of Alaska Fairbanks, determined that Arctodus" moved in a pacing motion like a camel, horse, and modern bears, making it built more for endurance than for great speed. A. simus, according to these arguments, was ill-equipped to be an active predator, leading some to conclude that it was a kleptoparasite, using its enormous size to intimidate smaller predators, such as dire wolves, Smilodon, and American lions, from their kills.
Some authors also suggest that the giant short-faced bear and the cave bear were omnivores, like most modern bears, and the former may have eaten plants depending on availability.
Ursus maritimus tyrannus
Ursus maritimus tyrannus was a very large fossil subspecies of the polar bear that descended from an Arctic population of brown bears. Its name in Latin means Tyrant Sea Bear.
Ursus maritimus tyrannus was the first polar bear and evolved sometime in the mid-Pleistocene. While the oldest fossil is 100,000 years old, they are thought to have evolved between 100,000 and 250,000 years ago from a population of brown bears likely isolated by glaciation. That population is believed to have diminished in numbers quickly into a much smaller population selected by species individual variation who adapted better to the changed environment. Over time with intense selective pressures on a small population they evolved the characteristics of the first polar bears.
Initially the isolated brown bears were no different than the variations of brown bears of that time period. Because litters of cubs can show significant species variations in hair color and hair thickness, this gave certain individuals a survival advantage passed on each generation. Eventually skull changes and even changes in dentition occurred leading to the smooth and rather quick evolution of U. maritimus tyrannus.
U. maritimus tyrannus was considerably larger then its modern relative. If everything is scaled out correctly from its remains, it would had been 183 cm (6 ft) at the shoulders, 3,6 m (12 ft) long and would have weighted an average of 1.2 tons, making it the largest bear "and one of the largest mammalian carnivores to ever walk on land". Its tremendous size makes it even bigger than the other "largest" mammalian carnivores that ever lived, including Andrewsarchus, Agriotherium, and Arctodus simus. It"s speculated that this gigantic bear would, due to its formidable size and strength, have preyed on mammoths which also lived during the time
Agriotherium
Agriotherium size is approximately 2.7 meters long and up to around 650 kilograms.
Another thing to consider is that if Agriotherium was a scavenger then it was likely getting to carcasses after all of the choice pieces of meat had been consumed with perhaps only bones being left. This would probably not be enough to thwart Agriotherium from a meal however since the short snout, strong jaw closing muscles and robust construction of the skull and jaws were all the things that Agriotherium needed to develop massive bite force. Computer modelling in a 2012 study (see links below) confirmed that Agriotherium had one of the largest bite forces known amongst the members of the Carnivora (A group of mammals that includes dogs, bears, cats, pinnipeds etc which are specially adapted to exist by eating meat). By being able to crack open bones, Agriotherium could access and eat the bone marrow within, and for those not familiar, bone marrow is one of the most nutritious parts of an animal, and can last for several years after an animals death when encased inside of the bones. One of the better known bears in the worlds fossil record, the Agriotherium genus is also easily one of the largest currently known. With this large size it would be tempting to portray Agriotherium as a savage killers of any animal that might be unfortunate enough to be in its way, yet like with its more famous relative Arctodus (better known as the giant short faced bear) first impressions may in this case be deceptive. The post cranial skeleton of Agriotherium is that of a large but relatively underpowered animal that simply does not seem to have the skeletal framework necessary to cope with high stresses, such as those expected to be encountered while undergoing extreme physical exertion (i.e. catching and subduing struggling prey). The second clue is that Agriotherium has a proportionately short snout to that seen in many other bears. The advantages of having a short snout are simple, it means that whatever is being bitten, is closer to the point of jaw articulation (fulcrum) so that greater force can be brought to bear (no pun intended) against it.
These are all features that are common to Arctodus which also has isotopic analysis of its bones revealing that it was eating nearly every type of animal in its ecosystem, something very unusual for a predator, but common for a scavenger. Given the superficial similarity in form between Agriotherium and Arctodus, it’s reasonable to speculate that Agriotherium may have been a specialised scavenger, a theory that is becoming increasingly put forward for Arctodus. Again, the concept is very simple, by being bigger than any other predator on the land, Agriotherium could in effect bully the smaller predators away from their kills. This draws parallels in bear/wolf interaction that is observed in the wild even today, where grizzly bears will watch a pack of wolves bring down a prey animal, just to charge on in and drive them off after they have done all of the work for it. This fits with the surprisingly gracile skeleton of a large animal like Agriotherium, since if it was letting other predators do the work and the killing for it, why waste precious nutrients and calories upon developing and maintaining a skeleton stronger than it needed to be?
The idea of Agriotherium being what is termed a ‘hyper-carnivore’ is plausible, though it is not certain that Agriotherium only ate meat. Like with bears today, Agriotherium may have also supplemented its diet with fruits and certain plants, particularly tougher ones that required strong jaws. However the scavenger theory does actually fit better with Agriotherium in terms of the age of known fossils. Agriotherium first appears just after halfway through the Miocene before disappearing at the end of the Pliocene. The similar Arctodus however begins to appear in the Pliocene before becoming most numerous during the Pleistocene. It might be that Agriotherium was one of the first specialised scavenger bears but was eventually replaced in the worlds ecosystems by more advanced versions that form separate genera, as well as possibly other bone crunching animals such as hyena.
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