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Post by brobear on Jun 19, 2023 15:01:23 GMT -5
The Heavyweights: A. angustidens & A. simus shaggygod.proboards.com/thread/454/heavyweights-angustidens-simus Credits to grrraaahhh... Mar 12, 2011 Good news everyone. Collection of materials on the Americas GSFB HEAVYWEIGHTS have met with good success. Many of us have been following with strong interest the latest material covering Arctotherium angustidens. The new data on the giant South American specimen inspired me to double check and dig around for material on its comparable sized North American cousins; the Giant Short Faced Bear (A. simus). By my count, there are a handful of fossil specimens that are comparable in scope, however, the heavier build advantage goes to the South American bear. They include a northern Californian specimen with a record size ulna measurement of 591 mm; the Lake Bonville, Utah specimen with a record size femur measurement of 723 mm; a Kansas specimen with a record size humerus measuring 646 mm; a Cass County (Nebraska) specimen with a humerus measurement of 633 mm, and another large Nebraska specimen from Hay Springs. Although less revealing, a future review (to better cross reference) of skull and dental data is warranted and planned. How would a completed Gold Run Creek, Yukon Territory (record size skull find) specimen compare to some of its larger cousins? Back to our original theme and to wrap up things, unpublished photos (i.e., our northern California specimen), plus illustrations (e.g., the Cass County, NE humerus) and material data have been collected and are being organized. |
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Post by brobear on Jun 19, 2023 15:06:07 GMT -5
grrraaahhh... Mar 18, 2011 Sorry for the delay (busy schedule, material collection & organizing, etc) but I wanted to get things rolling here. First some updates, I was hoping and I am still trying to obtain fossil photos for two large Arctodus simus specimens one of them from Kansas and the other from Hay Springs, Nebraska. My efforts have led me to conclude that there has been no published photo release of these two specimens. Now for the good news - we will have a forum milestone of sorts. I did find success in obtaining photos for the Irvingtonian (Alameda, CA) specimen. FYI, there has been no published release of photos for the Irvingtonian specimen. Photos for the Cass County humerus and Lake Bonneville femur have been acquired (the Utah specimen can be found online if you look hard enough). What I am providing here is a humerus and femoral fossil comparison table for the largest A.simus & A.angustidens’ specimens. As the data reveals, although there are North American A.simus specimens that produce longer humerus values, a review of the mid shaft width values tell us that A.angustidens is the heavier built bear. Comparable femoral data suggest a similar conclusion. The closest North American specimen to approach A.angustidens relative to robusticity is the specimen from Kansas. In the North American theater, the Kansas River specimen produced a higher mid shaft width femoral values than both the Lake Bonneville and Hay Springs bears. Moreover, the Kansas specimen produces a longer humerus than the Cass County, Nebraska GSFB.  |
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Post by brobear on Jun 19, 2023 15:09:25 GMT -5
grrraaahhh... Aug 11, 2011 Coming soon folks (sorry for the long delay) but attempts were made to obtain professional assistance to help scale the different photographs but these attempts were not successful. What will be provided shortly will nonetheless prove satisfactory for all. As promised......  |
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Post by brobear on Jun 19, 2023 15:15:01 GMT -5
grrraaahhh... Oct 6, 2011 The earlier humerus data make up the top four (three bears total) GSFB largest humerus fossils. Two bears are from North America, the other & heaviest bear is from Argentina. KUVP 131586: Regrettably, the distal end for this left femur is missing so the incomplete data was ignored. UC 44686 (the longest GSFB ulna fossil): Ulna measurements A: 591 B: - C: 65 D: 47 E: 35.2 A. Greatest Length. B. Proximal diameter from tip of coronoid progress to Margo dorsalis. C. Smallest diameter from bottom of semi circular notch to Margo dorsalis.. D. Inner diameter of semi circular notch. E. Least transverse diameter of shaft, above capitulum. UC 44687 (2nd total length GSFB femur) Femur Measurements: A. 678 B. a165 C. 77 D. 62 E1. 134 A. Greatest Length. B. Greatest proximal width. C.Caput diameter. D. Least transverse width of shaft. E1. Greatest distal width over epicondyles. Source: Kurten (1967). Both CA specimen unpublished photos have been obtained & plans are to publish them later similar to the earlier humerus figure material. Ideally, I was hoping to obtain photos for the Hay Springs bear for a comprehensive publication but travel issues & scheduling conflict have complicated matters. Femoral measurements (1st in total length GSFB femur fossil): UVP 015 Lake Bonville, Utah Specimen & Material: UVP 015/1 Greatest length: 723 Greatest proximal width: 191 Caput diameter: - Least transverse width of shaft: 64 Greatest distal width over condyles: 152 shaggygod.proboards.com/thread/329 Keep in mind, different fossil models produce different weight estimates. There are some data I want to review. I will try to follow up more shortly. |
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Post by brobear on Jun 19, 2023 15:21:23 GMT -5
Body Mass Estimation
There have been few attempts to estimate the size of the ‘short-faced’ bear. Where estimates were made, often the sample size was small.
Limb bones are responsible for supporting the animal’s weight during locomotion (Anyonge, 1993; Christiansen and Harris, 2005), thus providing the best mass estimates for extinct species. Kurt´en (1967) used the reconstructed body length and the cross-sectional area of a femoral diaphysis of a large specimen from Hay Springs for calculating its mass as between 470 and 630 kg.
Employing Kurt'en's method, Nelson and Madsen (1983) obtained an estimate of 620–660 kg for the specimen UVP 015 from Salt Lake County (Northern Utah), based on the diaphyseal area of the femur.
Christiansen (1999b) used several measurements taken in the proximal limb bones to estimate the mean mass of three specimens of A. simus as ca. 770 kg.
Figueirido et al. (2010) measured the maximum length and least width of the diaphyseal shaft of each major limb bone in a data set of 58 specimens of the eight species of extant ursids. Log-transformed data were used for calculating least squares bivariate regression functions of body mass on each measurement. For each bear species, we used published estimates of average mass (Van Valkenburgh, 1990; Christiansen, 1999b, 2002; Egi, 2001; Anderson, 2004). The accuracy of the bivariate regression functions was evaluated from their percent prediction errors (%PE) and the percent standard error of the estimates (%SEE) following Smith (1981, 1984). Approximately one third of specimen body mass estimates approached one tonne - the author further speculates that bears of this size were more common than previously suspected.
Soibelzon and Schubert (2011) obtained body mass of South American short-faced bears following the estimates by Soibelzon and Tartarini (2009) employing the allometric equations published by other authors (e.g., Van Valkenburgh,1990; Anyonge, 1993; Viranta, 1994; Christiansen, 1999; Egi, 2001). The study by Soibelzon and Tartarini (2009) compared more than sixty equations based on teeth, skull and postcranial measurements, and found the most reliable predictor of body size for large specimens was six measurements of the humerus (proposed by Anyonge, 1993; Egi, 2001; Christiansen, 1999) and one on the radius (formulated by Viranta, 1994) (for more details see Soibelzon and Tartarini, 2009). Thus, the size of the individual described here is estimated based on the preserved humerus and radius using these seven equations. The result, the Argentine specimen had an estimated body mass ranging from 983 to 2,042 kg depending on the equations considered while the mean and median body mass estimates (considering all equations) were 1,588 and 1,749 kg respectively.
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Post by brobear on Jun 19, 2023 15:28:18 GMT -5
Both models provided by "Prehistoric Fauna". The two biggest bears that have ever lived right next to each other; on your right we have the giant Arctotherium specimen (based on a 620mm humerus) and on your left we have the "Behemoth of Kansas River" (based on a 646mm humerus). They are looking down at your average Joe... On all fours...
 Giant vs Giant. Arctodus simus vs Arctotherium angustidens size comparison |
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Post by brobear on Jun 19, 2023 15:37:28 GMT -5
By tigerluver who is a biologist and also among the better posters over on WF.  |
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Post by brobear on Jun 19, 2023 16:05:55 GMT -5
Arctodus Simus (record skull)
Greatest Skull Length: 521mm
Mastoid Width: 240mm
Greatest Length/Mastoid Width-Ratio: 2.170
Arctotherium Angustidens
Condylobasal Length of the Skull: 402.8mm (n=11; range: 364-430mm)
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Post by brobear on Jun 20, 2023 4:12:56 GMT -5
Ursus arctos - Aug 15, 2012 shaggygod.proboards.com/thread/966/largest-bear-fossils grrraaahhh said: In examining the largest GSFB humerus fossil (A.angustidens), it is difficult to quantify the full impact of the large pathology at the mid shaft point; compare both left and right fossil humerus measurement values for the South American giant. ________________________________________________ The article followed Merriam and Stock (1925) for measurements. I haven't read that article, but if the midshaft measurements included these pathologies (note that the left humerus was wider; 9.3 vs 9.1 cm in AP diameter, and 9.0 vs 8.4 cm in ML diameter) they may exaggerate the size of this animal, especially in comparison to these largest Arctodus simus specimens with even longer humeri. At regions other than midshaft (where the pathologies are) the widths look similar. And I don't only mean the epicondyles-the actual diaphysis look similar in shape and width elsewhere. Arctotherium angustidens was probably much larger on average as a species or even regional population (hard to say when sample size of mature males=1), but I wouldn't be surprised if the largest known individual bears so far are all actually Arctodus simus. |
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Post by brobear on Jun 20, 2023 4:48:36 GMT -5
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Post by brobear on Jun 20, 2023 4:56:07 GMT -5
A gallery of "short-faced bears." A) Arctotherium angustidens; B) Arctotherium bonariense; C) Arctotherium vetustum; D) Arctotherium tarijense; E) Arctotherium wingei; F) Arctodus simus; G) Arctodus pristinus; H) Tremarctos ornatus (spectacled bear); I) Tremarctos floridanus. From Figueirido and Soibelzon, 2010. www.wired.com/2011/02/demythologizing-arctotherium-the-biggest-bear-ever/  |
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Post by brobear on Jun 20, 2023 5:00:09 GMT -5
Fossil of 700,00-year-old giant bear found north of Buenos Aires  |
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Post by brobear on Jun 20, 2023 5:16:52 GMT -5
Here is a picture of Arctodus's humerus  |
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Post by brobear on Jun 20, 2023 5:19:22 GMT -5
Arctotherium angustidens and a modern Andean bear.  |
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Post by brobear on Jun 20, 2023 5:26:10 GMT -5
Arctodus Simus (record skull) Greatest Skull Length: 521mm Mastoid Width: 240mm Greatest Length/Mastoid Width-Ratio: 2.170 Arctotherium Angustidens Condylobasal Length of the Skull: 402.8mm (n=11; range: 364-430mm) Well, I have spent the bigger part of two hours searching for information on the measurements of the skull of Arctotherium angustidens. Came up empty.  |
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