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Bears of the Pleistocene
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Cave bear or not ?
Post #372 is the classic giant European cave bear. Posts #374 and 375 is great art-work. Interesting art-work, it means brown bear was a powerful competitor for homo species in Pleistocene from Eurasia to America, on the other hand, brown bear also was a rival for big cat up to now, did cave lion would fight with brown bear frequently at that period ? We have no evidence that I know of concerning cave lions and brown bears. Brown bears seldom used caves. My guess is pretty much as tigers hunt bears in Russia today, cave lions did likewise.  
About #376 and #377: The Atlas bear may conflicted with the Barbary lion. If the big felid lived in prides as the other lions did (and do), the ursid may not have an easy life, excepted if its diet was rather vegetarian. But perhaps I'm supposing too much.
As concerns the cave bear, I really believe the cave lion hunted it during winter when the ursid hibernated. 
A little visit back to our tyrant brown bears, as I'll provisionally nickname them.
So a while ago I came across a 2001 PhD thesis by Sarah Elizabeth Collinge (what happened to her since then, I don't know, I can't find a trace of her since this thesis), titled "Body Size and Community Structure in British Pleistocene Mammals", which aimed to estimate the body mass of various large mammal species which existed in the British Isles during the Pleistocene. https://drive.google.com/file/d/1IH9HeHk...R_USX/view This includes the brown bear, Ursus arctos, which, according to her, reached their largest size during the Banwell era (identified as MIS 4 in the text, but now known to be the earlier period of MIS 5a).  *This image is copyright of its original author She estimates a mean weight of 414kg for the bears of this time, with a standard deviation of 187kg. In the text and Appendix 4.3a, this is broken down to the fact that there is considerable variation in mass estimates for bear specimens from different sites:  *This image is copyright of its original author She writes: Quote:Mass estimates from some of the specimens approach 1000 kg, but estimates cover a very large range and imply the occurrence of unusually high sexual dimorphism in this animal. A single humerus specimen from Wretton is also large in size and produces a mass estimate of 440 kg.-pg. 319 Differences in sex composition at the sites seems a plausible enough explanation, given the high level of dimorphism seen in the brown bear, males being approximately 1.8 times the weight of females, on average. As far as I'm aware they date to the same span of ~20,000 years where this large for of brown bear existed (), though as mentioned the age of the deposits have been shifted slightly. Assuming the specimens used for the British MIS 5a bears across various sites gave an overall 1:1 sex ratio (unlikely but let's assume) I got average weights of 532kg for boars and 296 kg for sows assuming modern brown bear dimorphism. AFAIK modern Kodiaks weigh on average about 390kg for males and 210kg for sows, and polar bears 500kg and 227kg for boars and sows respectively. https://www.bearbiology.org/fileadmin/tp..._Vol_7.pdf https://www.fs.usda.gov/treesearch/pubs/.../20066.pdf https://www.researchgate.net/profile/And...ts-Sea.pdf This would make the tyrant brown bear a very large bear indeed. BUT However, I'm a bit cautious to accept those size estimates too readily. While I don't doubt that the MIS 5a brown bears of the UK were very large, I'm not sure if the mass estimates given by Collinge 2001 were accurate, or if they are overestimating to some degree. According to her she did use extant bear specimens to build regression equations to calculate ursid mass (pg. 137). But looking at the very large U. a. priscus femoral fragment I mentioned in post #358, the largest in the image, from Skarszyn, I looked at table 8 in Marciszak (2017)'s paper as well as his estimated length of 550-560mm for the complete femur. Using Christiansen (1999)'s equations, I got weights of 531-562kg for the upper and lower bounds for the femoral length estimates respectively, but using Collinge (2001)'s equations (found in Appendix 3.1.6b) on the lowest estimated FL (550mm), I got a weight of 914kg, quite a bit larger. No other measurements for the Skarszyn femoral epiphysis weight-able by Christiansen (1999)'s are available, but continuing with Collinge's ursid equations: FL(550mm) 914 FDAW 997 FDAD 1173 Mean - 1028kg Not sure how plausible it is for the Skarszyn giant to have weighed around a ton, but there seems to be some difference at least between the equations of Collinge (2001) and Christiansen (1999). Is there anyone here who knows a bit about Ursid mass estimates that might weigh in on this? @tigerluver or @GuateGojira, you've written a bit on felid mass, as far as I can tell, though I'm not sure if you can weigh in on this, or know of any users here who can... if not that's fine.
https://www.researchgate.net/publication...onia_Chile
The southernmost bear: Pararctotherium (Carnivora, Ursidae, Tremarctinae) in the latest Pleistocene of Southern Patagonia, Chile. A second upper incisor belonging to the tremarctine bear Pararc-totherium was recovered from latest Pleistocene deposits in Cueva de los Chingues, Magallanes, Chile (San Roman et al., 2000; Fig. 1). This is the southernmost record of an ursid in the world and one of the youngest records of Pararctotherium. The paleoenvironment of south-ern Patagonia in the latest Pleistocene (ca. 11,000 yBP) was a cold grassland. The Ursidae originated during the late Eocene in the Holarctic region and throughout its history has primarily been restricted to the Northern Hemisphere. Ursids twice dispersed into Africa (Hunt, 1996): the Hem-icyoninae in the early Miocene and Agriotherium in the late Miocene, with the latter reaching the southern tip of Africa (ca. 33Њ 43Ј S). The Tremarctinae is comprised of five genera: Plionarctos, consid-ered Pararctotherium to be a subgenus of Arctotherium. We regard both Arctotherium and Pararctotherium as valid, distinct genera based on the systematic and phylogenetic revision of South American fossil bears by LHS (e.g., Soibelzon, 2000, 2002; Soibelzon et al., 2000). Tremarctines dispersed into South America from North America at least twice. The oldest records of Arctotherium are early Pleistocene (Ensenadan age; Kraglievich and Ameghino, 1940; Berman, 1994; Soi-belzon and Bond, 1998; Soibelzon et al., 2001; Soibelzon, 2002). Tre-marctos, which lacks a fossil record in South America, probably crossed the Panamanian Isthmus in the latest Pleistocene or Holocene (Soibel-zon, 2002). South American fossil bears are primarily recovered from the Pampean Region (ca. 33Њ S), with isolated finds in Brazil, Bolivia, Chile, Venezuela, and Uruguay. Arctotherium latidens is the lone En-senadan tremarctine in South America. Following its extinction, tre-marctines were represented by several species of Pararctotherium dur-ing the middle to late Pleistocene (Bonaerian and Lujanian ages; Cione and Tonni, 1999). It was distributed widely across southern South America (Bolivia, Brazil, Argentina, Uruguay, and Chile) and persisted until the end of the Lujanian (Soibelzon and Bond, 1998; Soibelzon, 2002).
I am interested to know more about Paractotherium pamparum and also more on the subject of post# 379.
http://zmmu.msu.ru/rjt/articles/article....ages=71-75
Skull of the Pleistocene brown bear (Ursus arctos) from Yakutia, Russia. Baryshnikov G.F., Boeskorov G.G. P. 71-75 A skull of the robust brown bear found in the mouth of Ulakhan-Orto-Stan River in the north of Yakutia has been examined. Its morphometrical characteristics referred the specimen to the subspecies U.arctospriscus Goldfuss, 1818 recorded in the later Middle and Late Pleistocene of Europe. This find revealed the wider distributional range for U.a.priscus, extending eastward as far as the northern part of East Siberia. DOI: 10.15298/rusjtheriol.3.2.04 (01-12-2019, 07:09 PM)brotherbear Wrote: http://zmmu.msu.ru/rjt/articles/article....ages=71-75Interesting, the last cave lion's population also from Yakutia Russia, it means cave lion would likely to conflict with brown bear at the same area during the late Pleistocene 
Cave Bear paw, it measures 13 inches long
Credit to @natural_selections  *This image is copyright of its original author
Does anyone here know what Ursus taubacbensis was? This bear is new to me.
 (05-18-2020, 09:04 AM)bruin Wrote: Does anyone here know what Ursus taubacbensis was? This bear is new to me. That is a synonym for fossil brown bears and might be a superfluous classification rather than a valid taxa. To quote Marciszak et al. (2015): "Fossil European brown bears were described by many authors under different names (e.g. Ursus ferox, taubachensis, horribilis etc.) (see Erdbrink, 1953 and reference therein; Pacher, 2007). Erdbrink (1953: 321) noted: “No other bear has been the cause of so much nomenclatorial confusion and general controversy”. The taxonomical nature of the Pleistocene bears was widely discussed by e.g. Erdbrink (1953) and Pacher (2007), and in general point of view authors agree with Baryshnikov and Boeskorov (2004) and Baryshnikov (2007) in recognition of three different fossil brown bear forms." It seems generally U. taubachensis specimens are part of U. priscus or U. artcos. I've attached three papers that shed light on the topic.
Included in what I've learned for the Pleistocene brown bears. Those in Europe were Kodiak bear-sized omnivores perhaps as much as 80% carnivorous living among mostly vegetarian cave bears. The brown bears of Ice Age N. America were Yellowstone grizzly-sized bears perhaps as much as 80% vegetarian living among the much more carnivorous short-faced bears.
But after the extinction of the mega-fauna, the brown bears of Europe became more vegetarian that their ancestors. The grizzly of N. America became a larger bear than previously and was perhaps as much as 80% carnivorous. With the extinction of the dire wolves, the various big cats, and the short-faced bears, the grizzly took-on the role of monarch among the Carnivora of N. America. WORLD'S RECORDS GRIZZLY BEAR: Greatest length of skull without lower jaw: 17 4/16 Greatest width of skull: 10 9/16 SCORE: 27 13/16 WORLD'S RECORDS ALASKA BROWN BEAR: Greatest length of skull without lower jaw: 17 15/16 Greatest width of skull: 12 13/16 SCORE: 30 12/16 This record grizzly skull ( inland grizzly ) was not killed by a hunter but was found by a hunter. It was a very rare discovery of a grizzly skull from the days when grizzlies followed the massive bison herds. Less than one inch difference in length from the *record Kodiak bear skull. Roughly two inches narrower in width. Consider that this is a discovery of a random bear - not likely the "biggest bear in the woods" - which would be a huge coincidence - and it is a Kodiak bear sized grizzly. The skull has a narrower shape. The grizzly populations which tend to be the most carnivorous tend to have narrow skulls. ( more polar bear-like ).
https://www.kwch.com/content/news/Kansas-sisters-find-grizzly-bear-skull-along-Arkansas-River-563213811.html
These three skulls found in Kansas might be from some of the grizzlies of the "Old West" who followed the bison herds. Or possibly Pleistocene. My guess is Holocene because of the long canines. From the scant evidence of Pleistocene grizzlies, they are thought to have leaned more towards a vegetarian diet. After the extinction of the mega-fauna, they became more carnivorous, until the invasion of Euro-Americans with modern rifles. Any thoughts?  *This image is copyright of its original author
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