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Post by brobear on Dec 2, 2019 10:30:54 GMT -5
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Post by brobear on Dec 11, 2019 17:16:24 GMT -5
Arctodus simus skull:
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Post by Deleted on Dec 12, 2019 22:47:15 GMT -5
More Arctodus simus skulls, taken from Jurassic Fight Club (documentary)
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Post by brobear on Dec 13, 2019 1:35:09 GMT -5
Nice verdugo. Even at size-parity, the short-faced bears had a more robust / more powerful bite than bears of the genus Ursus.
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Post by brobear on Dec 29, 2019 3:24:47 GMT -5
paleoenterprises.com/product-category/bear-fossils/ The short-faced bears belonged to a group of bears known as the tremarctine bears or running bears, which have been found in the Americas and Europe. The earliest member of the Tremarctinae was Plionarctos edensis, which lived in Beijing, Indiana and Tennessee during the Miocene Epoch (10 mya). This genus is considered ancestral to Arctodus, as well as to the modern spectacled bear, Tremarctos ornatus. Tremarctos floridanus was a contemporary. Although the early history of Arctodus is poorly known, it evidently became widespread in North America by the Kansan age (about 800,000 years ago). The South American genus, Arctotherium, was the closest relative to Arctodus and it had similar short-faced adaptions and reached similar or greater sizes. Arctodus simus first appeared during the middle Pleistocene in North America, about 800,000 years ago, ranging from Alaska to Mississippi, and it became extinct about 11,600 years ago. Its fossils were first found in the Potter Creek Cave, Shasta County, California. It might have been the largest carnivorous land mammal that ever lived in North America. In a recent study, the mass of six specimens was estimated, one-third of them weighed about 900 kg (1 short ton), the largest being UVP 015 at 957 kg (2,110 lb), suggesting specimens that big were probably more common than previously thought. Furthermore, claw marks reaching heights of up to 4.6 m (15 ft) on the walls of the Riverbluff Cave are indicative of the great size of the short-faced bears that made them. Arctodus pristinus (3.0-2.2 Mya), a species with two specimens weighing 500.7 kg (1,100 lb) and, in a likely subadult specimen, 63.6 kg (140 lb) inhabiting more southern areas from northern Texas to New Jersey in the east, Aguascalientes, Mexico to the southwest, and with large concentrations in Florida, the oldest from the Santa Fe River 1 site of Gilchrist County, Florida paleontological sites. Researchers disagree on the diet of Arctodus. Analysis of their bones showed high concentrations of nitrogen-15, a stable nitrogen isotope accumulated by meat-eaters, with no evidence of ingestion of vegetation. Based on this evidence, A. simus was highly carnivorous and as an adult would have required 16 kg (35.3 lb) of flesh per day to survive. One theory of its predatory habits envisages A. simus as a brutish predator that overwhelmed the large mammals of the Pleistocene with its great physical strength. However, despite being very large, its limbs were too gracile for such an attack strategy. Alternatively, long legs and speed (50–70 km/h (30–40 mph)) may have allowed it to run down Pleistocene herbivores such as steppe horses and saiga antelopes in a cheetah-like fashion. However, in this scenario, the bear’s sheer physical mass would be a handicap. Arctodus skeletons do not articulate in a way that would have allowed for quick turns, an ability required of any predator that survives by killing agile prey. Dr. Paul Matheus, paleontologist at the University of Alaska Fairbanks, determined that Arctodus moved in a pacing motion like a camel, horse, and modern bears, making it built more for endurance than for great speed. This giant bear was only recently recognized as a member of the fossil record in Florida. Recent research has indicated that this giant predator, the king of his world, may not have been the runner once thought. His suspected running abilities were based mostly on the length of his ulna and legs, but now researchers are saying that he was simply a huge bear, thus his limbs were so large because he was huge. Whatever, he was likely the largest and most fierce predator at the time he lived.
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Post by brobear on Dec 29, 2019 3:32:40 GMT -5
The Giant Short Faced Bear was 1,5 to 1,80 m (5 to 6 feet) tall at the shoulder and rose to an impresive 3 m (10 feet) when standing on its hind legs, it weighted 600 to 800 kgs (1320 - 1760 pounds) the giant was taller than a Polar Bear . The short muzzle gave it a more lion-like face than other bears, it has a relatively wide skull and very powerful jaws. Its closest living relative is the South American Spectacled Bears. What did they eat? Analysis of the bones of Short Faced Bears shows that they were exclusive meat eaters and they were well adapted to this task, their shortened jaws would have brought their crushing teeth closer to the back of the skulland so have increased their power. This Bear seen to be adapted for cracking large bones to extract the nutritious marrow. Book Prehistoric America - Miles Barton, Nigel Bean, Stephen Dunleavy, Ian Gray, Adam White.
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Post by brobear on Jan 2, 2020 5:35:43 GMT -5
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Post by brobear on Jan 4, 2020 8:27:45 GMT -5
www.tandfonline.com/doi/full/10.1080/02724630903416027?fbclid=IwAR3EP2ydacvvn1Q9DKvAd346llYVlgfhdWSF3gb0Vuix205cyM7Vff-7HpA Demythologizing Arctodus simus, the ‘short-faced’ long-legged and predaceous bear that never was. In this study, we review the previous evidence on the paleobiology of the giant, ‘short-faced’ bear Arctodus simus (Mammalia: Carnivora: Ursidae) and contribute new ecomorphological inferences on the paleobiology of this enigmatic species. Craniodental variables are used in a comparative morphometric study across the families Felidae, Hyaenidae, Canidae, and Ursidae. Principal components analyses (PCAs) do not show an ecomorphological adaptation towards bone-cracking or hypercarnivory in the ‘short-faced’ bear. In contrast, PCAs and discriminant analyses restricted to the craniodental data set of ursids suggest close morphological resemblance between A. simus and the extant omnivorous bears.
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Post by brobear on Jan 4, 2020 8:30:03 GMT -5
Continued: In addition, the scaling of snout length on neurocranial length in bears indicates that the face of A. simus was not particularly short. Body mass estimates obtained from major limb bone measurements reveal that A. simus specimens of around 1000 kilograms were more common than previously suspected. Scaling relationships in extant bears of limb lengths on the least width of the femoral shaft (the variable best correlated with body mass) indicate that A. simus was not as relatively long-legged as previously thought. For these reasons, although the isotopic signature of A. simus has been interpreted as evidencing that it consumed large amounts of flesh relative to some contemporary populations of Ursus arctos, our results do not support the previous views of A. simus as a fast-running super-predator or as a specialized scavenger. In contrast, the picture that emerges from this study is one of a colossal omnivorous bear whose diet probably varied according to resource availability.
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Post by brobear on Jan 4, 2020 8:32:07 GMT -5
Continued: INTRODUCTION With an average body mass estimated at 700–800 kg (Christiansen, 1999b), the enigmatic ‘short-faced’ and ‘long-legged’ bear Arctodus simus (Cope, 1879) (Mammalia: Carnivora: Ursidae: Tremarctinae) was the largest terrestrial carnivoran that ever existed in North America, playing a pivotal role in the Pleistocene ecosystems (Fig. 1A). As a matter of fact, remains of Arctodus have been recovered from more than 100 North American localities, spanning the middle Irvingtonian through the Rancholabrean (Richards and Turnbull, 1995) and becoming extinct with most of the megafauna after the last glacial maximum (Guthrie, 2006), at ≤11,400 BP (Gillette and Madsen, 1992). Quote: With an average body mass estimated at from 1,543.24 pounds to 1,763.70 pounds. Quote: In any case, our results provide a coherent picture of A. simus as the largest North American carnivore during the Quaternary.
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Post by brobear on Jan 4, 2020 8:39:13 GMT -5
Continued: The feeding ecology of A. simus has been subject of controversy during the last decades and still remains as an open debate. For example, Kurtén (1967) suggested that it was an active predator (Fig. 1B) based on several features that, in his opinion, evidenced a ‘felid-like’ anatomy compared to other bears. These traits include a short and broad muzzle, highly sectorial carnassials, a highly vaulted calvarium, powerful jaws, and elongated limbs. Following Kurtén's hypothesis, most authors have since then assumed that A. simus was one of the largest cursorial carnivores ever known (e.g., Voorhies and Corner, 1986; Guthrie, 1988; Richards et al., 1996; Barnes et al., 2002; Fox-Dobbs et al., 2008).
However, Emslie and Czaplewski (1985) tried to demythologize A. simus based on morphological similarities with its closest living relative, the South American spectacled bear (Tremarctos ornatus). They suggested that A. simus was omnivorous, with a diet that included huge amounts of vegetable matter (Fig. 1D), although they also emphasized its bone-cracking capabilities. In any case, the morphological similarity in the craniodental anatomy of A. simus and T. ornatus probably arises from their close phylogenetic relationship as tremarctine bears, rather than reflecting an evolutionary convergence.
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Post by brobear on Jan 4, 2020 8:40:50 GMT -5
Continued: Subsequent advances in isotopic analyses of bone collagen and their paleoecological applications led Matheus (1995), Bocherens et al. (1995), and Barnes et al. (2002) to revive the ‘big fierce’ hypothesis. More specifically, based on the comparatively high δ15N of A. simus, they suggested that it was a strict carnivore, thus corroborating Kurtén's hypothesis. Additionally, Matheus (1995) also concluded that due to the likely competition with other predators, A. simus was more likely to have been a specialized scavenger than a fast cursorial predator (Fig. 1C). Under this reconstruction, the long limbs of A. simus would have allowed it to forage economically across a large home range, and its large size could have been a deterrent for the Pleistocene carnivores, hence facilitating carcass kleptoparasitism (Matheus, 1995). However, the hypothesis of A. simus as a super-predator has been revived recently by Fox-Dobbs et al. (2008), who analyzed carbon and nitrogen isotopes of late Pleistocene carnivores and megafaunal prey species from eastern Beringia. In this study, A. simus was considered the most specialized member of the carnivoran guild, suggesting that it may have displaced from carcasses other species such as saber-tooth cats (e.g., Homotherium serum) and lions (Panthera atrox).
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Post by brobear on Jan 4, 2020 8:42:43 GMT -5
Continued: Sorkin (2006) questioned the interpretations derived from isotopic analyses on the basis that the ranges of δ13C and δ15N values measured in bone collagen of terrestrial mammals do not allow distinguishing of strict carnivores from omnivores that include significant amounts of flesh in their diet. Sorkin (2006) also analyzed the dental and skeletal morphology of A. simus, following a comparative anatomical approach, and concluded that the ‘short-faced’ bear was a big omnivore whose diet would have included a high percentage of animal matter obtained through scavenging.
Finally, in a recent study, Figueirido et al. (2009) performed a relative warp analysis of skull variation among the living bears and two extinct species, A. simus and the European cave bear (Ursus spelaeus). Their results showed that craniodental shape primarily reflects the feeding adaptations of ursids and only secondarily their phylogenetic affinities. Of interest to this study, both A. simus and U. spelaeus plotted in the cranial and jaw morphospaces within the living omnivorous bears.
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Post by brobear on Jan 4, 2020 8:43:53 GMT -5
Continued: In summary, a review of the available paleobiological evidence indicates that the feeding adaptations of A. simus are not well understood and deserve more in-depth study. The objective of this article is to re-evaluate the ecomorphological evidence on the trophic behavior of the ‘short-faced’ bear following a comparative approach based on morphometric analyses of the craniodental and appendicular skeleton in ursids.
Institutional Abbreviations—AMNH, American Museum of Natural History, New York; F:AM, Frick Collection, American Museum of Natural History, New York; LACM, Los Angeles County Museum, California; MFN, Museum für Naturkunde, Berlin; NHM, Natural History Museum, London; MNCN, Museo Nacional de Ciencias Naturales, Madrid; MNHN, Muséum National d’Histoire Naturelle, Paris; FMNH-PM, Field Museum of Natural History, Chicago; UM, University of Michigan, Museum of Paleontology, Michigan; UVP, Utah Vertebrate Paleontology, Utah Division of State History, Utah.
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Post by brobear on Jan 4, 2020 8:47:09 GMT -5
www.tandfonline.com/doi/full/10.1080/02724630903416027?fbclid=IwAR3EP2ydacvvn1Q9DKvAd346llYVlgfhdWSF3gb0Vuix205cyM7Vff-7HpA ( same site as above ) continued. MATERIALS AND METHODS Species and Specimens We analyzed both the cranial and postcranial skeleton. The craniodental data set includes 411 individuals from 57 species belonging to the families Ursidae, Canidae, Felidae, and Hyaenidae (Table 1). Bears are represented in this data set by the eight living species and A. simus. Canids include 25 species of the subfamily Caninae, including the 4 pack-hunting, hypercarnivorous species (Lycaon pictus, Canis lupus, Cuon alpinus, and Speothos venaticus; Van Valkenburgh, 1991; Van Valkenburgh and Koepfli, 1993), 21 species with a meso- or hypocarnivorous behavior, and 4 extinct borophagines (Epicyon saevus, Epicyon haydeni, Aelurodon ferox, and Borophagus diversidens), which have all been interpreted as pack-hunters with bone-cracking capabilities (Wang et al., 1999; Van Valkenburgh et al., 2003). Felids are represented by 17 extant species, which cover nearly two orders of magnitude in body size, and hyaenids include the three ossiphagous species of this family. The latter two families were included to evaluate if A. simus shows morphological convergences with the living cats or with the bone-cracking hyenas, respectively, because such convergences would be expected if this extinct bear were a hypercarnivore (Kurtén, 1967) or behaved as a specialized scavenger (Matheus, 1995). Canids were included in the morphometric analyses because the putative convergent characters between A. simus and the feloid carnivores could be hidden by phylogenetic constraints, which is not the case with canids, because they are phylogenetically closer to the ursids (Bininda-Edmonds et al., 1999).
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Post by brobear on Jan 4, 2020 9:00:53 GMT -5
Continued: CONCLUSIONS Our results suggest that A. simus was neither a super-predator nor a specialized scavenger, at least over its whole geographic range. Instead, the ecomorphological analyses suggest that the overall craniodental morphology of this ursid is similar to that found in the living omnivorous bears. In addition, we have shown that the snout of A. simus is not shorter than expected for an omnivorous bear this large, and also its legs are not as relatively long for its size as previously assumed. Thus, we suggest that the popular description of A. simus as a ‘short-faced’ bear should be revised in the light of the new evidence. Although it is true that A. simus exhibits a broad rostrum, this is also the case of the Malayan sun bear and the Andean bear, which are both omnivorous. Thus, we conclude that this character is not an accurate indicator of a highly carnivorous diet in bears. In short, we suggest that A. simus may be best envisaged as a colossal omnivore whose diet probably included varying amounts of meat according to food availability. Of course, we do not wish to imply that A. simus did not prey occasionally on bison, deer, or ground sloths, nor that it did not scavenge the carcasses left over by the hypercarnivores such as saber-tooth cats (Smilodon fatalis and Homotherium serum), giant lion (Panthera atrox), and dire wolf (Canis dirus). We simply affirm that A. simus did so in a similar manner as some North American populations of brown bears (e.g., Alaska and Yukon) currently do so.
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Post by brobear on Jan 4, 2020 9:01:47 GMT -5
ACKNOWLEDGMENTS This research has been financed by the Spanish Ministry of Science and Education, project CGL2008–04896/BTE, and FPU grant to B. Figueirido. We are especially grateful to G. Slater for providing us the pictures of A. simus from Rancho La Brea. Thanks also to O. San-Isidro for his reconstruction and illustrations of A. simus. P. Christiansen, C. M. Janis, B. Van Valkenburgh, and S. F. Vizcaíno contributed useful comments for developing the manuscript and provided insightful suggestions for improving an earlier version of the paper. We also acknowledge the comments of two anonymous reviewers. *Note: so much more to see on the actual site. I only covered that which I viewed as the highlights.
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Post by brobear on Jan 7, 2020 5:02:26 GMT -5
Biggest bear and biggest cat of Pleistocene N. America.
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Post by King Kodiak on Jan 7, 2020 6:16:38 GMT -5
Yeah, while the largest Pleistocene south american cat was the Smilodon populator. Largest Pleistocene south american bear was Arctotherium Angustidens. Both a little larger than their North american counterparts.
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Post by brobear on Jan 11, 2020 6:47:59 GMT -5
Reply #150 - Quote: With an average body mass estimated at 700–800 kg. *My Conclusion: Result of your conversion: 750 kilograms is equal to 1,653.47 pounds (avoirdupois) = average weight of 1,650 pounds. *Note: The greatest weight recorded for a Kodiak bear in the wild is 1656 lb ( 751 kg ) for a male shot at English Bay.
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