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Pleistocene Polar Bear v South American Giant Short-faced Bear
Topic Started: Sep 16 2012, 05:53 PM (11,778 Views)
Taipan
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South American Giant Short-faced Bear - Arctotherium angustidens
Arctotherium is an extinct genus of South American short-faced bears within Ursidae of the late Pliocene through the end of the Pleistocene. They were endemic to South America living from ~2.0–0.01 Ma, existing for approximately 1.99 million years. 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.[2] A specimen of A. angustidens from Buenos Aires shows an individual estimated, using the humerus, to weight between 983–2,042 kg (2,170–4,500 lb), though the authors consider the upper limit as improbable and say that 1,588 kg (3,500 lb) is more likely, however, using the radious, the mass estimate shrinks to a maximum of 1,108 kg (2,440 lb). Independently of the method it is possibly the largest bear ever found and contender for the largest carnivorous land mammal known to science.

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Pleistocene Polar Bear - 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. 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 (Ranging up to an estimated mass of 1,200 kg (2,600 lb)). 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.

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yigit05
Sep 15 2012, 11:30 PM
pleistocene polar bear vs arctotherium
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1.0reef
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IIRC Pleistocene Polar Bears only weighed around 400kg, if so then I'd give it to Arctotherium.
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yigit05
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Vivyx
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Felines, sharks, birds, arthropods
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Bob5
Feb 13 2014, 06:32 AM
Both of these creatures are enormous, but I think that the short faced bear would win because it is still bigger.
Pleistocene Polar Bear wasn't what you would call "enormous"
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BoomerSooner
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yigit05
Mar 5 2014, 01:45 AM
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That's one scary bear. I find it amusing that saber-tooth cats are so popular, yet these monsters are rarely discussed.
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blaze
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It was no where near that big
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BoomerSooner
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deleted post
Edited by BoomerSooner, Mar 5 2014, 02:58 PM.
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BoomerSooner
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blaze
Mar 5 2014, 09:19 AM
It was no where near that big
If it was 3500 lbs, I don't think that picture is too unrealistic.
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yigit05
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BoomerSooner
Mar 5 2014, 09:12 AM
yigit05
Mar 5 2014, 01:45 AM
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That's one scary bear. I find it amusing that saber-tooth cats are so popular, yet these monsters are rarely discussed.
the world's largest bear ever.the world's largest land predator ever
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blaze
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I base its size on the size of its bones not on an estimate of its mass, the combined length of its humerus, radius and scapula doesn't exceed 147cm (4ft 10 inches) from where will the other 2ft 1in of shoulder height come from?

The same goes the only bone of U. m. tyrannus, its estimated to be 48.5cm long, about 15% longer than in a pair of big subadult polar bears but is not 15% thicker, in fact is just as thick as those shorter ulnae, so U. m. tyrannus had long arms and probably didn't even exceed 120cm (4ft) at the shoulder.
Edited by blaze, Mar 6 2014, 02:00 AM.
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