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Post by brobear on Jan 5, 2020 7:05:14 GMT -5
Ancient polar bear or giant brown bear?
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Post by brobear on Jan 7, 2020 13:32:11 GMT -5
www.marinemammalscience.org/facts/ursus-maritimus/ When the polar bear was originally documented, two subspecies were identified: the American polar bear (Ursus maritimus maritimus) by Constantine J. Phipps in 1774, and the Siberian polar bear (Ursus maritimus marinus) by Peter Simon Pallas in 1776. This distinction has since been invalidated. One alleged fossil subspecies has been identified: Ursus maritimus tyrannus, which became extinct during the Pleistocene. U.m. tyrannus was significantly larger than the living subspecies. However, recent reanalysis of the fossil suggests that it was actually a brown bear.
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Post by OldGreenGrolar on Feb 6, 2020 22:47:53 GMT -5
Rough comparison of Ursus maritimus tyrannus (left) with human (red) and polar bear (right).
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Post by brobear on Feb 17, 2020 3:39:13 GMT -5
TheGreenArtos, where is the site "address" of reply #62?
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Post by OldGreenGrolar on Feb 21, 2020 21:14:12 GMT -5
TheGreenArtos, where is the site "address" of reply #62? I found it on google. I will try to search for it later.
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Post by brobear on Feb 22, 2020 3:00:10 GMT -5
TheGreenArtos, where is the site "address" of reply #62? I found it on google. I will try to search for it later. You don't have to bother with it. But just remember to post the address of the sites you find for reference; Thanks.
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Post by OldGreenGrolar on Feb 22, 2020 3:11:12 GMT -5
I found it on google. I will try to search for it later. You don't have to bother with it. But just remember to post the address of the sites you find for reference; Thanks. Will do.
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Post by OldGreenGrolar on Feb 22, 2020 3:35:53 GMT -5
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Post by brobear on Feb 22, 2020 6:25:21 GMT -5
Above picture - try to envision U.M.tyrannus as a grizzly... which would be more realistic according to some ( experts ).
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Post by OldGreenGrolar on Feb 23, 2020 3:19:55 GMT -5
Above picture - try to envision U.M.tyrannus as a grizzly... which would be more realistic according to some ( experts ). So experts believe that U.M. tyrannus would look more like a brown bear which would seem more accurate considering polar bears owe their existence to the brown bear.
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Post by King Kodiak on Feb 23, 2020 6:52:52 GMT -5
Above picture - try to envision U.M.tyrannus as a grizzly... which would be more realistic according to some ( experts ). So experts believe that U.M. tyrannus would look more like a brown bear which would seem more accurate considering polar bears owe their existence to the brown bear. Yeah, most experts actually believe that Tyrannus was a brown bear. It could actually be the Pleistocene European brown bear (Ursus arctos Priscus), or maybe a different subspecies. It could still be a large Pleistocene polar bear though.
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Post by brobear on Mar 26, 2020 5:18:18 GMT -5
Reply #3... www.polarresearch.net/index.php/polar/article/viewFile/6131/6810The Kew Bridge find is special in that it is an ulna of a very large animal, considerably larger than present-day polar bears. Kurtén (1964) assigned it to a polar bear subspecies, Ursus maritimus tyrannus. The Kew Bridge specimen has recently been reinvestigated by scientists at London’s Natural History Museum, and they are now confident that the Kew animal was a type of brown bear, U. arctos (Andy Currant, pers. comm. 2008). reply #15.... That said, it is true that these British bears were isolated for a considerable amount of time, from about 87.22-66.8 thousand years ago, based on the dating of this period, spanning roughly 20,000 years. From this; my thoughts are: a group of steppe brown bears - Ursus arctos priscus - were isolated from others of their kind for 20,000 years certainly creating a new subspecies. I am waiting and expecting a name-change to Ursus arctos tyrannus.
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Post by brobear on Apr 2, 2020 10:18:37 GMT -5
Ghari Sher - wildfact.com/forum/topic-bears-of-the-pleistocene?page=26 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. drive.google.com/file/d/1IH9HeHk...R_USX/viewThis 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).
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Post by brobear on Apr 2, 2020 10:20:11 GMT -5
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:
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Post by brobear on Apr 2, 2020 10:22:15 GMT -5
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. www.bearbiology.org/fileadmin/tp..._Vol_7.pdfwww.fs.usda.gov/treesearch/pubs/.../20066.pdfwww.researchgate.net/profile/And...ts-Sea.pdfThis 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.
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Post by OldGreenGrolar on Dec 9, 2020 6:48:34 GMT -5
Ursus Maritimus Tyranus is predicted to be a 400 pound brown bear so it might not even exist or it might be a huge brown bear subspecies.
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Post by brobear on Dec 9, 2020 6:52:12 GMT -5
Ursus Maritimus Tyranus is predicted to be a 400 pound brown bear so it might not even exist or it might be a huge brown bear subspecies. *Where is your source?
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Post by OldGreenGrolar on Dec 9, 2020 6:58:07 GMT -5
Ursus Maritimus Tyranus is predicted to be a 400 pound brown bear so it might not even exist or it might be a huge brown bear subspecies. *Where is your source? domainofthebears.proboards.com/post/1279/My mistake it says 400 kgs not pounds.
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Post by brobear on Dec 9, 2020 7:56:47 GMT -5
400 kilograms is equal to 881.85 pounds. I have doubts as to the accuracy of this.
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Post by brobear on Jan 6, 2021 12:30:59 GMT -5
From reply #6: dinopedia.fandom.com/wiki/Ursus_maritimus_tyrannus Quote: An unpublished reinvestigation of the fossil suggests that the fossil is actually a brown bear. *Why in the name of Uncle Sam's top hat did this procrastinating 'Gold Brick' wannabe biologist not publish his work? WTH!
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