Size comparisons

[tigerluver]

(09-28-2020, 10:01 AM)Rishi Wrote:

(09-28-2020, 09:50 AM)Stripedlion2 Wrote: Can y’all do a size comparison of an average cave bear to an average polar bear then the largest cave bear compared to the largest polar bear.

I have one for short-faced bear. Won't vouch for its accuracy though, especially because we do not know how large the largest of these  bears was...

*This image is copyright of its original author

*This image is copyright of its original author

Digging through a post from 4 years ago, U. m. tyrannus seems to be overexaggerated in that comparison.

(01-06-2016, 03:53 AM)tigerluver Wrote: The largest U. m. tyrannus is a fragmented ulna estimated to be no less than c. 485 mm by Kurten (1964) in length. The largest polar bear male published in the same work has a 428 mm. The largest A. angustidens ulna is 570 mm and the largest 591 mm for A. simus if I'm not mistaken. 

Small sample size for U. m. tyrannus, no doubt, but it still seems well outclassed by the giant short-faced bears. Averaging the ulna lengths of the 6 males in Kurten  (1964) and assuming these males average 450 kg and ulna scales isometrically, this specimen would would around 860 kg. Issue is, the ulna is a distal long bone and often lengthens for locomotion rather than mass, and if U. m. tyrannus is not a carbon copy of the modern polar but rather more cursorial, this specimen would be lighter than 860 kg. The width measurements for fossil ulna show a specimen either as robust or a bit less robust than the modern polar bears, so 800 kg may be more likely. 

Use this link to read Kurten (1964): The evolution of the Polar Bear, Ursus maritimus Phipps 

One last thing, seeing the 591 mm ulna for A. simus, and comparing it to A. angustidens 570 mm ulna, which is from the same specimen whose 620 mm humerus gave it the title of heaviest bear, this title is again brought into question. I've already gone over the femur issue, and now this A. simus ulna produces a humerus of no less than 640 mm assuming equal proportions.

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