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Nov 10, 2010 19:38:12 GMT -9
Post by grrraaahhh on Nov 10, 2010 19:38:12 GMT -9
Prehistoric Bears Ate Everything And Anything, Just Like Modern CousinsThe short-faced bear, a hypercarnivore, also ate plants depending on their availability. The work offers key insights into the evolution of the carnivore niches during the Ice Age.
Through a statistical analysis, the experts determined the patterns of morphological variation in bears in order to prove that, rather than ancestral/descendent relations, 'the pattern had more relation to trophic ecology than to phylogenetic heritage', highlights Figueirido.
Given the glaciations of the Pleistocene (in the Quaternary period), prehistoric bears, with morphologies similar to those of present-day omnivores, ate a bit of everything depending on the resources available to them, determined by the climatic conditions. For the palaeontologist, 'during that period there was, in principle, a wide variety of prey and vegetation available, but there was also competition amongst the predators of the time'.
www.sciencedaily.com/releases/2009/04/090408170815.htm
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Nov 10, 2010 19:38:41 GMT -9
Post by grrraaahhh on Nov 10, 2010 19:38:41 GMT -9
GSFB: Blogger extract ....As Schubert and Wallace report, however, there is now evidence that at least two large carnivores lived in the same area at the same time. The most direct evidence comes from a partial right lower jaw bone with a molar tooth still embedded in it. It belonged to a very large bear, and the details of the teeth and shortening of the jaw (indicating a short face) allowed the researchers to narrow down their list of candidates to Arctodus simus, popularly known as the "short-faced bear." In fact, compared to other skeletons from this species, this individual from Virginia appears to have been especially snub-nosed. The second line of evidence comes from mammoth bones found at the same site. The scientists describe several parts of a mammoth ankle and foot that were chewed on by carnivores. The question is, "What kind of carnivores did the damage?"
One of the bones, the calcaneus (or heel bone) was bitten completely through by a predator with a large canine tooth. Only two known Late Pleistocene carnivores were large enough to inflict this type of damage; the American lion (Panthera leo atrox) and the short-faced bear. As big cats typically avoid chewing on bones, however, the bear is the more likely culprit.* This is consistent with the results of radiocarbon dating carried out on the mammoth bones and the bear jaw. The two animals lived within about 340 years of each other, so it is likely that both coexisted in the same place at the same time.
*[The authors point out, however, that American lions are often found with broken teeth. This suggests that they more regularly bit through bone and chewed hard parts of carcasses than their modern relatives in Africa and India. Though no remains have been found of the American lion at the Saltville site, it cannot be ruled out as a suspect.]scienceblogs.com/laelaps/2009/10/the_stench_emanating_from_the.phpSCHUBERT, B., & WALLACE, S. (2009). Late Pleistocene giant short-faced bears, mammoths, and large carcass scavenging in the Saltville Valley of Virginia, USA. Boreas, 38 (3), 482-492 DOI: 10.1111/j.1502-3885.2009.00090.
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Dec 11, 2010 10:58:36 GMT -9
Post by grrraaahhh on Dec 11, 2010 10:58:36 GMT -9
No evidence has turned up that the giant short-faced bear, the sabertooth cat, or any of the other extinct big beasts shown in this painting (save for the mastodon) were ever hunted by early Americans.End of the Big Beasts: www.pbs.org/wgbh/nova/evolution/end-big-beasts.html
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Jan 8, 2011 14:59:44 GMT -9
Post by grrraaahhh on Jan 8, 2011 14:59:44 GMT -9
What a BEAST!!! The Largest Known Bear, Arctotherium angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in BearsAbstract The South American giant short-faced bear (Arctotherium angustidens Gervais and Ameghino, 1880) is one of five described Arctotherium species endemic to South America and it is known for being the earliest, largest, and most carnivorous member of the genus. Here we report an extraordinarily large A. angustidens individual exhumed from Ensenadan sediments (early to middle Pleistocene) at Buenos Aires Province, Argentina. Based on overall size, degree of epiphyseal fusion, and pathologies, this bear was an old-aged male that sustained serious injuries during life. Body mass of the bear is estimated and compared to other ursid species based on a series of allometric equations. To our knowledge, this specimen now represents the largest bear ever recorded. In light of this discovery, we discuss the evolution of body size in Arctotherium (from large-to-small) and compare this to bears that exhibited different evolutionary trajectories. We suggest that the larger size and more carnivorous nature of A. angustidens, compared to later members of the genus, may reflect the relative lack of other large carnivores and abundance of herbivores in South America just after the Great American Biotic Interchange. www.bioone.org/doi/abs/10.1666/10-037.1?journalCode=pleo
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Jan 29, 2011 10:35:10 GMT -9
Post by grrraaahhh on Jan 29, 2011 10:35:10 GMT -9
Soibelzon, L. (2002).
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Mar 3, 2011 12:54:20 GMT -9
Post by grrraaahhh on Mar 3, 2011 12:54:20 GMT -9
The Hay Springs specimen is one of the notable larger North American A. Simus obtained. Nonetheless, it locally places second place to its bigger cousin from nearby Cass Count, NE.
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Mar 9, 2011 12:35:27 GMT -9
Post by grrraaahhh on Mar 9, 2011 12:35:27 GMT -9
As noted.... Short faced bear ,subadult? Alaskan brown bear Confusion leading to mistaken mislabeling of the two fossil skulls have occurred.
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Mar 12, 2011 19:26:10 GMT -9
Post by grrraaahhh on Mar 12, 2011 19:26:10 GMT -9
As noted.... Short faced bear ,subadult? Alaskan brown bear Confusion leading to mistaken mislabeling of the two fossil skulls have occurred. From the U.a.lasiotus myth & lore thread: Head of a bear, Ainu village of Shiraoi, Japan. shaggygod.proboards.com/index.cgi?board=lore&action=display&thread=3&page=1Note: It is understood, there were no GSFB in Japan. That point is not being made.
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Mar 13, 2011 11:50:07 GMT -9
Post by grrraaahhh on Mar 13, 2011 11:50:07 GMT -9
Beringia Brown Bear Migration into North America & Brown Bear/A.simus Relations (Limited Extract):"Therefore, the founding population at 21 ka B.P. appears to have contained considerable amounts of existing, but already monophyletic, mt diversity. This is not consistent with a very small founding population, but rather indicates a larger group that had been drawn from a more diverse, but primarily monophyletic, population elsewhere." "Fig. 1. Phylogeny and sample details for brown bear (U. arctos) specimens. (A) Phylogenetic tree constructed with two fragments (135 and 60 bp) of the control region and neighbor-joining (HKY model) showing clades (1 to 4) and subclades (a to c). The topology is in agreement with that of other, larger data sets (7). (B) Radiocarbon dates and speci c locations of the specimens. Additional specimen data are provided in the supplementary material (11).larger group that had been drawn from a more diverse, but primarily monophyletic, population elsewhere." "Few specimens are available from pre–35 ka B.P. populations, but within this group only the Yukon Territory population (Sixtymile) appears polyphyletic (4 and 2c, n 5 2). In contrast, the bear population around Fairbanks at the same time appears monophyletic for subclade 3c (n 5 8). This geographic division between bear populations in interior Alaska and the Yukon Territory is similar to that between modern 3a/3b populations, indicating that the geographic location of population barriers (but not the populations themselves) may be relatively constant through time. Such barriers are presumably ecological or physiographic (e.g., the Yukon-Tanana Uplands, Olgilvie Mountains, Brooks Range) (Fig. 2A)." "Because no obvious climatic or environmental events appear to explain the extinction and recolonization of brown bears in eastern Beringia, alternative explanations need to be considered. There is a marked inverse correlation between the chronology of brown bears and the much larger, hypercarnivorous, shortfaced bears in eastern Beringia (Fig. 3A). Although the two species coexisted for at least 10,000 years (;45 to 35 ka B.P.) during the interstadial, short-faced bear fossil dates are concentrated between 35 to 21 ka B.P. when brown bears were absent. Furthermore, brown bear recolonization (;21 ka B.P.) is precisely coincident with the last record of short-faced bears in Beringia.""Stable-isotope data (Fig. 3B) suggest that the diets of the two bear species differed substantially while they were contemporaneous. Enriched levels of 15N show that short-faced bears were carnivorous, whereas brown bears were variably omnivorous and herbivorous, similar to most noncoastal bears today (Fig. 3B) (8, 19). In contrast, during the period 21 to 10 ka B.P. following the apparent extinction of short-faced bears in Beringia, brown bears also show an enriched mean 15 N signal relative to both the pre–35 ka B.P. and modern populations. However, competitive interaction is extremely difficult to infer from the paleo-record, and several environmental factors can affect isotopic ratios. In addition, much taxonomic turnover would be expected to occur around 21 ka B.P. during the environmental changes of the early LGM. If the enriched signal does indeed reflect a higher trophic level, then it may simply indicate an increased carcass biomass availability 21 to 10 ka B.P., which presumably disappeared following the extinction of many large-mammal taxa in the terminal Pleistocene." "The pronounced phylogeographic structure of modern Alaskan bears is unrelated to the separation of clades 3a and 3b [245 to 310 ka B.P. (7)] or the subsequent expansion of clade 3b (79 to 100 ka B.P.), which probably long preceded the colonization events in east Beringia (Fig. 2). This finding is supported by the presence of both clades in Japan (5). Furthermore, the phylogeographic pattern is not directly attributable to a post-LGM expansion (2, 7, 23, 24) because clade 3b is present in the Fairbanks region at 21 ka B.P., coincident with the LGM, and 3a is unrecorded until after 10 ka B.P." Dynamics of Pleistocene Population Extinctions in Beringian Brown Bearswww.sciencemag.org/content/295/5563/2267.abstract
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Mar 13, 2011 12:26:27 GMT -9
Post by grrraaahhh on Mar 13, 2011 12:26:27 GMT -9
Fig. 1. Proximal femur of Ursus americanus (left) and Arctodus simus (UTEP 5689.4.38). Some idea of size can be seen from the medial-lateral measurement of the head of the femur: 68.5 mm for Arctodus and 36.5 mm for Ursus americanus. Giant Short-faced Bear specimen from U-Bar Cave. www.utep.edu/leb/pleistNM/taxaMamm/Arctodus.htm
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Mar 13, 2011 16:07:53 GMT -9
Post by grrraaahhh on Mar 13, 2011 16:07:53 GMT -9
Large brown bear skulls (the last example, northern Japan brown bear) & miss-identification of sub adult/female GSFB.
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Mar 14, 2011 0:32:48 GMT -9
Post by warsaw on Mar 14, 2011 0:32:48 GMT -9
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Mar 17, 2011 21:12:59 GMT -9
Post by grrraaahhh on Mar 17, 2011 21:12:59 GMT -9
Giant Short-faced Bears (Arctodus simus) in Pleistocene Florida USA, a Substantial Range ExtensionAbstract Fossils of the giant short-faced bear, Arctodus simus (Cope, 1879), have been recovered from over 100 localities in North America, extending from Mexico to Alaska and California to Virginia. Despite this large range, the species has never been recorded from the southeastern United States. The lesser short-faced bear, Arctodus pristinus Leidy, 1854 is well represented from this region, particularly Florida, but all known occurrences are late Pliocene – middle Pleistocene in age (about 2.5 to 0.3 Ma). Differentiating A. simus from A. pristinus can be difficult because large individuals of A. pristinus overlap in size with small individuals of A. simus, and there are few morphological differences. However, these two taxa can be clearly separated based on the relative proportions of their molars and premolars. Two Pleistocene records of A. simus representing a minimum of three individuals from the Withlacoochee River drainage of central Florida are reported here, substantially extending the distribution of this massive bear into southeastern North America. A late Pleistocene age for these occurrences is corroborated by an associated Rancholabrean fauna and rare earth elemental analyses. One of the reported individuals is quite large, supporting the hypothesis of extreme sexual dimorphism in A. simus and rejecting a hypothesis of two subspecies. www.bioone.org/doi/abs/10.1666/09-113.1
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Mar 18, 2011 8:41:34 GMT -9
Post by grrraaahhh on Mar 18, 2011 8:41:34 GMT -9
Same author, earlier article:
"If short-faced bears were large, aggressive scavengers capable of stealing carcasses from other large carnivores, then it seems unlikely that brown bears could dominate them in direct interference competition. And while brown bears may have preferred to feed on animal carcasses, it seems more likely that they would have avoided direct confrontation with a dominant bear. The ecological plasticity of brown bears and their ability to hibernate may have been the keys to their ultimate survival at the end of the Pleistocene, while Arctodus, the highly specialized forager, was not able to find a niche in Holocene ecosystems. Most likely, carcass densities on Holocene landscapes fell below levels necessary to sustain minimal viable populations of short-faced bears. Since many bears hibernate to survive poor food availability during winter, this may be an indirect indication that short-faced bears, and perhaps all New World bears, never evolved this strategy to survive seasonal dietary bottlenecks.”
Paul E. Matheus, 1995, Diet and co-ecology of Pleistocene short-faced bears and brown bears in eastern Beringia. Quaternary Research 44(3):447-453.
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Mar 18, 2011 21:20:33 GMT -9
Post by grrraaahhh on Mar 18, 2011 21:20:33 GMT -9
Key extracts from a recent 2010 paper on A.simus body weight & mass: Body Mass Estimation"Few attempts have been made to estimate the size of the ‘short-faced’ bear. For example, Kurten (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. Similarly, 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. Finally, 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. Unfortunately, all these studies were based on a small number of specimens, which do not reflect the wide intraspecifc body mass range expected in a highly dimorphic species such as A. simus (Kurten, 1967; Cox, 1991). As indicated above, in this study we 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." "The fact that one third of the specimens analyzed approached a ton suggests that individuals of this size were more common than previously suspected." Figueirido, Borja. 2010, Demythologizing Arctodus simus, the ‘Short-Faced’ Long-Legged and Predaceous Bear that Never Was. Also.... Per Christiansen's 1999 popular paper on A.simus & Cave bear body mass: What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? Abstract Body masses of the giant short-faced bear (Arctodus simus Cope) and the cave bear (Ursus spelaeus Rosenmueller & Heinroth) were calculated with equations based on a long-bone dimensions:body mass proportion ratio in extant carnivores. Despite its more long-limbed, gracile and felid-like anatomy as compared with large extant ursids, large Arctodus specimens considerably exceeded even the largest extant ursids in mass. Large males weighed around 700-800 kg, and on rare occasions may have approached, or even exceeded one tonne. Ursus spelaeus is comparable in size to the largest extant ursids; large males weighed 400-500 kg, females 225-250 kg. Suggestions that large cave bears could reach weights of one tonne are not supported. Free PDF LINK: www.sekj.org/PDF/anzf36/anzf36-093p.pdf
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