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Bears of the Pleistocene
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Posts #14 thru #26 shows strong evidence that the Pleistocene grizzly was no larger than today's grizzlies. However, there is also evidence that at least some inland grizzly populations from the early Holocene right up until the invention of the modern breech-load rifle ( 1848 ) were indeed in the size-range of salmon-eating coastal bears. I believe that the demise of the giant short-faced bears was a stepping stone for the grizzly.
Ursus deningeri - http://prehistoric-fauna.com/Ursus-deningeri
Ursus deningeri (Ursus deningeri Richenau, 1904) Order: Carnivora Family: Ursidae Dimensions: length - 2,5 m, height - 135 сm, weight - 150-600 kg Temporal range: Pleistocene of Eurasia Ursus deningeri (Deninger's bear) is an extinct species of mammal of the family Ursidae (bears), endemic to Eurasia during the Pleistocene for approximately 1.7 million years, from ~1.8 Mya to 100,000 years ago.The range of this bear has been found to encompass both Europe and Asia, demonstrating the ability of the species to adapt to many Pleistocene environments. U. deningeri is a descendant of U. savini and an ancestor of U. spelaeus. Ursus deningeri has a combination of primitive and derived characters that distinguishes it from all other Pleistocene bears. Its mandible is slender like that of living brown bears and Ursus etruscus. It also has derived characters of cave bears (Ursus spelaeus) and is considered to be the descendant of Ursus savini and very close to the common ancestor of brown bears. *Note: 600 kg = 1300+ pounds.
Cave Bear subspecies:
1 - Ursus deningeri - a giant ancestral cave bear. 2 - Ursus kudarensis - Asiatic cave bear. 3 - Ursus eremus - a smaller cave bear. 4 - Ursus ladinicus - a smaller cave bear. 5 - Ursus spelaeus ingressus - the giant omnivorous cave bear. 6 - Ursus spelaeus spelaeus - the giant vegan cave bear. 7 - Ursus spelaeus sensu lato - ?
Cave Bears and Brown Bears: Phylogenetic distance tree showing the placement of the cave bear sequences when the 139 bp control region fragment is used. The tree was calculated by the NJ method. Bootstrap values obtained after 1000 replicates are indicated for each branch. The tree is rooted with two U. americanus sequences. The various populations of brown bear are designated as in [7], as follows: PYR (Pyrenees, France), CAN (Cantabrian mountains, Spain), NOR (Norway), DAL (Dalarna, Sweden), CRO (Croatia), SLO (Trentino, Italy), ABR (Abruzzo, Italy), BUL (Bulgaria), GRE (Greece), EST (Estonia), RUS (Russia, Slovakia, Lapland, and Finland), RO (Romania)
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Short Faced Bear Arctodus simus Skull
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http://www.pnas.org/content/97/4/1651.full.pdf
Population genetics of Ice Age brown bears. The Pleistocene was a dynamic period for Holarctic mammal species, complicated by episodes of glaciation, local extinctions, and intercontinental migration. The genetic consequences of these events are difficult to resolve from the study of present-day populations. To provide a direct view of population genetics in the late Pleistocene, we measured mitochondrial DNA sequence variation in seven permafrost-preserved brown bear (Ursus arctos) specimens, dated from 14,000 to 42,000 years ago. Approximately 36,000 years ago, the Beringian brown bear population had a higher genetic diversity than any extant North American population, but by 15,000 years ago genetic diversity appears similar to the modern day. The older, genetically diverse, Beringian population contained sequences from three clades now restricted to local regions within North America, indicating that current phylogeographic patterns may provide misleading data for evolutionary studies and conservation management. The late Pleistocene phylogeographic data also indicate possible colonization routes to areas south of the Cordilleran ice sheet.  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author Giant Short Faced Bear in Fields Museum of Chicago 
For those interested in the book from which the above excerpts were provided, here it is.
Arctotherium wingei from Venezuela
 *This image is copyright of its original author  *This image is copyright of its original author Arctotherium wingei it was a small Bear that weighted up to 300 kilograms and measured 2 meters long
There are two Pleistocene bears each of which is arguably the biggest bear ever. Some will argue Arctodus simus while others will insist on Arctotherium angustidens. There may be an even older rival in this contest for the biggest bear ever. There was a bear, possibly closer to the giant panda lineage than to the other bears, that lived back roughly six million years ago, that might have equaled or even surpassed the giant short-faced bears in size. He is now known as Indarctos atticus.
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It seems peoples tend to overestimate the size of prehistoric animals. We saw this with gigantopithecus blacki which some poorly made estimate give us a fictionnal 500+ kilo apes. We also saw this with some prehistoric feline such as the american lion and he other bear species like ursus maritimus tyrannus etc. It's true that both arctodus simus and arctotherium augustidens were likely bigger than any extant bears and are probably both the largest extinct bear species ever discovered. However, indarctos atticus really doesn't deserve that title. You may have heard of a poster named blaze on carnivoraforum, he is a very knowlogeable when it come to size estimate of extinct animal. He also have a deviantart account where he debunked several of those misleading size estimates. Here is what he say about the subject : ''Indarctos (I. atticus and I. oregonensis) This taxon has not been claimed as “the biggest” in the literature as far as I am aware but it has certainly being called like that on the internet, this claim steams from an estimate of 3 metric tonnes made in Finarelli and Flynn (2006) based on the area of the first molar, this estimate is deemed highly improbable in the paper itself and certainly an overestimation, I can’t test it since they do not make know the specimen or measurements used and the equation they do provide doesn’t appear to give ridiculous results when compared to those obtained through GDI in a big specimen of Arctodus simus, so I will look into the size of the known limb bones. The postcranial skeleton of Indarctos atticus is poorly known so is a little surprising to find out that the most complete forelimbs yet found sat in a storage room for a 100 years, more surprising still is that radius and ulna pertaining to this specimen were described way back in 1931 (Pilgrim, 1931) but no one bothered with the rest of the bones until 2001. Roussiakis (2001) described associated forelimb material from Pikermi, Greece, stored in a wooden box and wrapped in newspapers, they likely belong to the excavations of 1901 made by Woodward and Skouphos. The specimen described by Roussiakis (2001) comprises a right humerus, a right ulna, right radius, right metacarpals I-V, all right wrist bones and left metacarpals II-V, every bone has its own catalogue number and they go from PA 1909/91 to PA 2028/91. The greatest length of the right humerus, catalogued as PA 1944/91 is 458.7mm in greatest length and the transverse diameter of its distal epiphysis is 110.5mm, the radius is 384.5mm long, their functional length can be estimated from the figures at 446mm and 349mm for the humerus and radius respectively, matching those of CNHM 63802, a male brown bear from the Alaska peninsula (Davis, 1964), probably the largest brown bear mentioned in the literature. Since the skull of CNHM 63802 is 45cm in greatest length and 26.7cm in zygomatic width and spring masses of full grown brown bears of comparable skull size have been estimated to be from 385kg to 544kg (Miller and Sellers, 1992) we can expect this specimen of Indarctos atticus to be that heavy right? The regression equations for greatest humeral length used by Soibelzon and Schubert (2011) offer support to this idea, giving masses from 490 to 710kg but there is something we are overlooking. The regression equation for the distal epiphysis gives a mass of only 270kg, a fraction of the others, why? because the ratio of transverse diameter of distal epiphysis* to greatest length of the humerus of this specimen is 24.1, much lower than in the brown bear, which can reach a ratio of 32 (Ehrenberg, 1964) and lower still than the ratio in Arctodus simus of 26.9 (Richards and Turnbull, 1995) the same hold true for the radius of this same specimen, therefore it doesn’t seem like a stretch to suggest that Indarctos atticus had long, relatively gracile forelimbs despite resembling those of the brown bear in several aspects (Roussiakis, 2001) and that equations based on length alone will result in overestimates, at last, to put in perspective its physical dimensions consider its shoulder height, the sum of the functional length of its humerus and radius is 79.5cm plus a scapula 31.5cm tall (estimated based on the proportions of A. simus) plus the height of the hand and flesh will put it at no more than 117cm at the shoulder. Based on the tables in (Roussiakis, 2001) this individual is definitely the largest specimen of I. atticus with the exception of two metacarpals from Concud, Spain, described by Crusafont-Pairó and Kurtén (1976), which are around 30% longer than the equivalent in the Pikermi individual, however, they are considerably slender, even in absolute terms and that they really belong in I. atticus is uncertain. I. oregonensis was described by Merriam, Stock and Moody (1916), known by teeth, fragmentary humerus, fragmentary ulna and other assorted fragmentary postcranial material, the humerus is sufficiently complete however and was estimated at 490mm long, 6.8% larger than the I. atticus from Pikermi, the proportions are similar but is slightly more robust, shoulder height will be no more than 125cm.  *This image is copyright of its original author While big specimens of Indarctos spp. do reach great sizes they are not outside the known range of extant brown and polar bears, not even the “over 850kg” as ultimately suggested by Finarelli and Flynn (2006) much less 3 metric tonnes seem realistic estimates. Up next, Ursus maritimus tyrannus. Notes: * I’d prefer to use shaft measurements but they are disparately reported in the literature with some giving greatest width while others minimum width. **Is important to mention that the slenderness of the bones is not appreciated in lateral view. References: Soibelzon, L. H., and Schubert, B. W. (2011). The Largest Known Bear, Arctotherium angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears. Journal of Paleontology 85(1), 69-75. Finarelli, J. A., and Flynn, J. J. (2006). Ancestral State Reconstruction of Body Size in the Caniformia (Carnivora, Mammalia): The Effects of Incorporating Data from the Fossil Record. Systematic Biology 55(2), 301-313. Pilgrim, G. E. (1931). Catalogue of the Pontian Carnivora of Europe in the Department of Geology. - 174 pp. London (British Museum Natural History Geology). Roussiakis, S. J. (2001). Postcranial remains of lndarctos atticus (Ursidae, Mammalia) from the classical locality of Pikermi (Attica, Greece), with a description of the front limb. Senckenbergiana lethaea 81(2), 347-358. Davis, D. D. (1964). The Giant Panda. A morphological study of evolutionary mechanisms. Fieldiana: Zoology Memoirs, 3: 1-339. Miller, S. D., and Sellers, R. A. (1992). Brown bear density on the Alaska Peninsula at Black Lake, Alaska. Final report on completion of density estimation objectives of cooperative interagency brown bear studies on the Alaska Peninsula. Alaska Department of Fish and Game, Juneau. Ehrenberg, K. (1964). Ein Jungbärenskelett und andere Höhlenbärenreste aus der Bärenhöhle im Hartlesgraben bei Hieflau (Steiermark). Annalen des Naturhistorischen Museums in Wien, 67: 189-252. Richards, R. L, and W. D., Turnbull. (1995). Giant short-faced bear (Arctodus simus yukonensis) remains from Fulton County, Northern Indiana. Fieldiana: Geology (New Series) 30:1–34. Crusafront-Pairó, M. and Kurtén, B. (1976). Bears and bear-dogs from the Vallesian of the Vallés-Penedés basin, Spain. Acta Zoologica Fennica, 144: 1-29. Merriam, J. C., Stock, C. and Moody, C. L. (1916). An American Pliocene bear. University of California Publications Bulletin of the Department of Geology, 10 (7): 87-109.'' http://blazze92.deviantart.com/journal/The-largest-known-bear-Part-1-440241554
Thank you HyperNova for clearing this matter up for me. Another mythical monster slain by knowledge.
Cave Bears (Ursus spelaeas)
Cave Bear standing credit to The Fossil Store, two Cave Bear skeletons in Museo Civico di Storia Naturale di Milan credit to Ettore anzalone, Cave Bear skull credit to Drake Fortner and Cave Bear skull credit to Christian D. Link  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author
  *This image is copyright of its original author Sketchs of the giant short faced bear... Such as I see this beast. Certainly the first one's head is too big. And being much more used to draw lions and tigers, I have certainly too some bad automatic reflexes.
Short Faced Bears skeletons and skull
Credits to @bakedbeeenz @siahmn @tmstephenson  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author
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