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Post by brobear on Apr 1, 2017 16:58:42 GMT -5
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Post by brobear on Apr 1, 2017 16:59:59 GMT -5
www.bioone.org/doi/abs/10.1080/02724630903416027In 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 bonecracking 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. 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. 1,000 kg = 2,205 pounds.
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Post by brobear on Apr 1, 2017 17:04:33 GMT -5
www.sci-news.com/paleontology/convergent-evolution-giant-bears-americas-03800.htmlAncient Mitochondrial DNA Reveals Convergent Evolution of Giant Bears in the Americas Apr 20, 2016 by Sergio Prostak A study led by Dr. Kieren Mitchell of the University of Adelaide sheds new light on the evolution of what are believed to be the largest bears that ever lived on Earth. Giant bears (greater than 800-1,000 kg) roamed both North and South America during the Pleistocene, 2.5 million to 11,000 years ago. These animals belonged to a now practically extinct subfamily of bears, Tremarctinae, which is today only represented by the Andean spectacled bear (Tremarctos ornatus), a largely herbivorous bear that is found in South America. The giant North American bears (genus Arctodus) and South American bears (genus Arctotherium) have long been believed to be each others’ closest relative. However, by comparing ancient mitochondrial DNA data obtained from representatives of the two extinct genera and comparing them with the living species, Dr. Mitchell and co-authors were able to show that Arctotherium is most closely related to the Andean spectacled bear and not Arctodus. “In this study, we sequenced a mitochondrial genome from an Arctotherium femur preserved in a Chilean cave,” the scientists explained. “Our molecular phylogenetic analyses revealed that the South American short-faced bears were more closely related to the extant South American spectacled bear than to the North American short-faced bears.” The implication of this result is that these bears represent a remarkable instance of convergent evolution, as giant bears appear to have evolved independently in both North and South America. “This convergent evolution would have arisen in response to similar environmental conditions on both continents, most likely an abundance of large herbivore carcasses (killed by smaller predators), which Arctodus and Arctotherium could effectively dominate, and a lack of competing scavengers,” Dr. Mitchell and co-authors said. The findings were published April 19, 2016 in the journal Biology Letters.
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Post by brobear on Apr 1, 2017 17:06:04 GMT -5
animaliaenthusiasts.proboards.com/thread/203/giant-short-faced-arctodus-simusIntroduction: Arctodus (Greek, "bear tooth") — known as the short-faced bear or bulldog bear — is an extinct genus of bear endemic to North America during the Pleistocene ~3.0 Ma.—11,000 years ago, existing for approximately three million years. Arctodus simus may have once been Earth's largest mammalian, terrestrial carnivore. It was the most common of early North American bears, being most abundant in California. Taxonomy, classification and evolution: The short-faced bears belonged to a group of bears known as the tremarctine bears or running bears, which are endemic to North America and Europe. The earliest member of the Tremarctinae was Plionarctos edensis, which lived in 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 kya). A parallel group of bears are the South American genus Arctotherium, which reached similar size and short faced adaptions.They were also 11 feet tall on hind legs. Read more: animaliaenthusiasts.proboards.com/thread/203/giant-short-faced-arctodus-simus#ixzz4GM0oTWkESize: Arctodus simus (2 to 1.9 Ma.), 110.2 kg (240 lb) and 800 kg (1,800 lb) as noted by Legendre and Roth, inhabiting a generally more northern and larger range. It was native to prehistoric North America from about 800,000 years ago, and became extinct about 12,500 years ago. It has been found from as far north as Ikpikpuk River, Alaska to Lowndes County, Mississippi. It is one of the largest bears in the fossil record and was among the largest mammalian land predators of all time. The type specimen came from Potter Creek Cave in Shasta County, California. Males from the Yukon region - the largest representatives of the species - would have stood about 1.80 m (5.9 ft) at the shoulder (on all fours), 4 m (13.1 ft) upright and may have weighed about 800 kg (1,864 lb). Arctodus simus was the largest carnivorous mammal that ever lived in North America. Dietary habits: Researchers disagree on the diet of Arctodus. Analysis of Arctodus bones showed high concentrations of nitrogen-15, a stable nitrogen isotope accumulated by meat-eaters, with no evidence of ingestion of vegetation. Based upon this evidence A. simus was highly carnivorous, and as an adult would have required 16 kilograms (35.3 lb) of flesh per day to survive. One theory of its predatory habits envisions Arctodus 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 kilometers per hour (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. Arctodus simus, according to these arguments, was ill-equipped to be an active predator, leading some to conclude that it was a kleptoparasite, using its enormous size to intimidate smaller predators such as dire wolves, Smilodon and American lions from their kills. Recently, closer dietary research on the giant short-faced bear as well as the Cave Bear suggests that both bears were omnivores like most modern bears, and that the former did eat plants depending on availability. Extinction: The giant short-faced bear became extinct about 12,000 years ago, perhaps partly because some of its large prey died out earlier, and partly also because of competition with the smaller, more omnivorous brown bears that entered North America from Eurasia. Since its demise coincides with the development of the Clovis technology and improved hunting techniques by humans in North America, hunting pressure may also have contributed to its extinction, both directly (human hunting) or indirectly (due to the depletion of other large mammals which it may have followed to scavenge kills or depended upon as prey). Popular culture references: Arctodus simus, the giant short-faced bear, was featured in the ninth episode of Jurassic Fight Club, where it fought with an American Lion over a Steppe Bison kill made by the lion. The battle was based on a fossil find from the Natural Trap Cave, in the U.S. state of Wyoming. The program used the available fossil evidence to predict who would win in the aforementioned fight. In the end, the Arctodus won by throwing the 750-pound Mega-Lion into the enormous cave, where it died of the fall.
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Post by brobear on Apr 1, 2017 17:07:25 GMT -5
iceage.museum.state.il.us/mammals/short-faced-bear-0 Short-faced bear, Arctodus simus The giant short-faced bear, Arctodus simus, was an extremely large bear that occupied much of North America throughout the Pleistocene. It is often described as the largest Pleistocene land carnivore in North America, although several new studies suggest that this member of the Carnivora family may actually have been an omnivore (Figuerido et al. 2010; Meloro 2011; Sorkin 2006). As with most other large mammals in North America, the short-faced bear went extinct at the end of the Pleistocene. The giant short-faced bear has been subdivided into two subspecies, A. simus yukonensis and A. simus simus, based on extreme differences in body size (Kurten 1967). It has been postulated that the larger subspecies, A. simus yukonensis, was restricted to the northwest portion of the species' range - specifically, Beringia, western Canada and the northwestern U.S. However, as more larger-bodied individuals have been recovered from locations in the southern portion of the giant short-faced bear's range, it has been suggested that the observed variation in body size may be due in part to extreme sexual dimorphism in the species (Schubert 2010). In some locations, males may have weighed almost twice as much as females. Order: Carnivora (Dogs, Cats, Bears, etc.) Family: Ursidae (Bears) Statistics: Height: 1.5 m (5 ft) at shoulder; 3.35 m (11 ft) when standing on hind legs Weight: Average: 700-800 kg (1540-1760 lbs); Christiansen 1999 Females: 300-400 kg (660-880 lbs); Figuerido et al. 2010 Males: 800-1000 kg (1760-2200 lbs); Figuerido et al. 2010 Status: Extinct The giant short-faced bear was an enormous animal, larger than the modern grizzly or polar bears. It had very long, legs for a bear, and a relatively short body given its height. Its feet were also distinctive in that the toes faced forward rather than inward, as in other bears. As its name suggests, this animal had a short face and broad muzzle with very robust teeth, although recent research suggests that its face may not have been much shorter, proportionally, than its modern relatives (Figueirido et al. 2010). Habitat: Based on the distribution of the species during the late Pleistocene, the giant short-faced bear occupied a range of habitats with diverse climatic conditions, including open plains, steppe tundra, boreal forests, open grasslands and subtropical woodlands (Schubert et al. 2010). Diet: Over the years, the short-faced bear has usually been described as a super predator (Kurtén 1967) and/or scavenger (Matheus 2003), and occasionally as an omnivore (Baryshnikov et al. 1994) or even an herbivore (Emslie and Czaplewski 1985; Sorkin 2006). Isotopic studies on fossil remains from Beringia (Barnes et al. 2002; Bocherens et al. 1995; Matheus 1995) indicate that individuals from Alaska and the Yukon consumed a very high proportion of meat, although similar studies have yet to be published from the southern part of its range. In fact, one recent study (Figueirido et al. 2010) of the has suggested that while meat was undoubtedly a large part of their diet, the giant short-faced bear was probably a generalized omnivore, similar to modern North American brown bears (e.g., grizzly bears), and would have eaten a variety of foods, depending on what was available. More recently, a study that analyzed the mandibular geometry of numerous living and extinct members of the Carnivora family found that the structure of the short-faced bear's mandible most closely matches that of the herbivorous Spectacled bear (Tremarctos ornatus), suggesting that this very large bear may, in fact, have been more herbivorous than previously suspected (Meloro 2011). Behavior: Given the strong association between female short-faced bear remains and cave sites, it is likely that the female of this species used caves for denning, particularly during pregnancy (Schubert and Kaufmann 2003). North American Ice Age Distribution: Arctodus simus was widely distributed across the U.S. and Canada during the last Ice Age. Recently, remains of a giant short-faced bear have been recovered from a site in the Appalachian Highlands of western Virginia (Schubert and Wallace 2009) and remains of three individuals have been recovered from two different sites in central Florida (Schubert et al. 2010). The latter find has greatly extended the known range of this animal during the last Ice Age and disproved a long held assumption that the giant short-faced bear had not ventured into the southeastern U.S. during this period (Kurtén and Anderson 1980). Status at the end of the Pleistocene: Analysis of a new suite of radiocarbon dates obtained on giant short-faced bear bones confirms that these animals went extinct roughly 11,000 years ago and most likely co-existed with groups of humans from the Clovis culture (Schubert 2010). Reasons for the species' extinction are unclear, but it is generally accepted that the extinction of larger prey species and increased competition from other species, such as brown bears or even humans, played a role in the disappearance of the giant short-faced bear during the Pleistocene/Holocene transition. Midwestern Paleontological Finds: Giant short-faced bear remains have been recovered from several cave sites in the Ozark Plateau of Missouri and Arkansas as well as from Indiana and Ohio. Recently, the remains of a short-faced bear were recovered from a farm in southwest Iowa.
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Post by brobear on Apr 1, 2017 17:19:05 GMT -5
accpaleo.wordpress.com/tag/arctodus-simus/A Central Coast Paleontologist The chronicle of an epic quest, interspersed with paleontology, archaeology, and maybe an occasional rant from an aspiring fossil hunter Some Further Thoughts on Arctodus Posted on March 20, 2011 1 Hey there every peoples! As you may remember from a little while ago i didn’t have the best outlook on everyone’s favorite ice age bruin Arctodus. The loss of what may have been one of the most fascinating carnivores of the Pleistocene is probably easier to bear (no pun intended) than i made it out to be. i have tried to make it clear that i have a mental illness that severely affects my outlook and disposition. However, looking back i now realize that Arctodus may be down, but he may not be out just yet. I talked about Arctodus being shrunk down from the giant it is often portrayed as. Well being the numb-nuts that i am, i had forgotten that the paper that stripped Arctodus of most of it’s unique characteristics actually argues that Arctodus may have been bigger than what some have argued: According to our estimates, the heaviest specimens of A. simus are UVP 015 from Utah and F:AM 25535 from Nebraska, with body masses calculated as ca. 957 and 863 kg, respectively (Table 3). In contrast, the smallest specimens are LACM 122434 from Rancho La Brea and UM25611 from Kansas, with figures of ca. 317 and 388 kg, respectively (Table 3). The fact that one third of the specimens analyzed approached a ton suggests that individuals of this size were more common than previously suspected. They go on to mention that the largest specimens come from colder climates (at least back then). This is consistent with what is observed in other mammals, in that cold climates favor larger body size. Also Arctodus appears to exhibit sexual dimorphism like modern bears, meaning that smaller specimens are most likely females. Another interesting note about the size of Arctodus comes from Riverbluff Cave in Missouri. Preserved on the walls of the cave are many parallel gouges consistent with claw marks. Based on the size and spacing of the marks they are thought to have been made by Arctodus. Another they think it’s Arctodus is that these claw marks are 12 feet up the cave wall! Finally, Eric Scott of the San Bernardino County Museum has offered to help quell my doubts by showing me an Arctodus astragalus from Murrieta and comparing it with other bears. There’s a field trip in May so I’ll try to to it then (Thanks Eric!). And as for meat consumption… Well, the isotope analysis was performed on specimens from Alaska and hence can’t be used to generalize the species. But just like we can’t generalize from a few specimens, can we really generalize based on one paper? They have put forward the argument that Arctodus was an omnivore, but it should not be accepted as gospel truth. People argued for Arctodus being herbivorous based on anatomy, and look what happened: specimens were found that demonstrated a diet almost entirely of meat. It’s clear that Arctodus’ diet is a bit more complicated. Who knows, maybe Arctodus was an omnivore but was more carnivorous than modern bears (like, say, 30% meat 70% plants, or maybe 40%/60%). Arctodus being a primarily vegetarian animal like modern bears raises a question: if it was a generalist, why did it die out? Surely it could have adapted like it’s grizzly cousins. One of the reasons the scavenging hypothesis made sense to me was it could at least in part explain why Arctodus died out: If all the large animals that Arctodus relied on for carrion died out, then it too would die out from lack of food. Just an observation. In short, we still have much to learn about this animal. The dearth of fossils discovered so far should make it obvious that this bear isn’t giving up it’s secrets easily. To give you an idea of how rare it’s fossils are, consider diamond Valley. Tens of thousands of fossils were found there during construction of a reservoir. Now predators make up as small part of the ecosystem, so they are less likely to be fossilized. But still, paleontologists in Diamond Valley found: a saber-toothed cat mandible and foot bone, a vertebra and pelvis of the American lion, and a cranium fragment, a foot bone, and tooth fragments of a dire wolf. What did they find of Arctodus? A single incisor! Of all the fossils found, the mighty Arctodus is represented by a single front tooth. Even in a predator trap like the La Brea Tar Pits, it’s a rare beast. Compare 30 bears to 3200 dire wolves, 2000 saber-toothed cats, and over 120 American lions. Not a whole lot to go on. I think we need to try and get a better idea of this bear’s biomechanics: how strong was it’s bite, how did move, how did its limbs function? Also i think we need to try and do isotope studies on fossils besides one found in the north. Perhaps diet may also explain why larger specimens are found in places like Utah and Nebraska. But we won’t know for sure until we focus on trying to figure this animal out rather than trying to bust popular myths. Central Coast Critters: Arctodus Posted on February 27, 2011 4 Hey there every peoples! The Pleistocene is one of my favorite time periods. Especially the late Pleistocene, the timeframe often referred to as the “ice age”. It feels richly exotic and yet strangely familiar. It was a time when animals of today mingled with long dead beasts. No matter how many mammoth and bison and camel fossils I see, I never get tired of the ice age. And perhaps the most charismatic are the carnivores, namely the saber-toothed cats, dire wolf, and bigass lion (which may have been a giant jaguar). But one beast has been the subject of particular scrutiny and fanfare, a creature who has proved most enigmatic. This creature is Arctodus simus, the giant short-faced bear. Now let’s get the obvious question out of the way: how do we know this animal lived on the Central Coast? I can’t say for certain, since my information on fossils from this region is very fragmented. However I can extrapolate from nearby fossil sites. Arctodus is known from the La Brea Tar Pits in Los Angeles but this is not the only tar pit locality in California. I have found a few mentions that there were tar pits in Carpentaria, just south of Santa Barbara, which yielded ice age fossils. I have been unable to find any detailed information so I can’t say with any certainty if the short-faced bear has been found there. However I do know that it is known from the McKittrick tar pits in western Kern County. Since Arctodus is known from localities around the Central Coast, it’s not unreasonable to think it lived here as well. Arctodus has been the subject of much debate in recent times. It has often been thought of as a giant, ravenous predator that terrorized the megafauna of ice age America. But this idea, it seems, has largely been rejected. It’s almost like a reversal of what happened with Tyrannosaurus rex. People didn’t take kindly to T. rex being thought of as a scavenger, so they set out to prove it was a hunter. Arctodus suffered the opposite: people apparently had issues with it being portrayed as a hunter and set out to “cork its fangs” (to use The Lord Geekington’s lingo). But just how did this come to pass? Let’s take a look. When Arctodus was first discovered, it stood out from other bears. While scientists were able to learn that it is related to the modern spectacled bear, this animal was very different. It was huge, larger than even the polar bears found to be roaming the Arctic. It has a short muzzle and stout canines, and it walked about on long lanky limbs. It ranged from coast to coast and from Alaska to Mexico. It’s short face and long legs were seen as convergent with felids and so it was envisioned as a pursuit predator using speed combined with its great strength to tackle bison and other large prey. As you can imagine, such an image stuck in the popular imagination, as exemplified in Kirk Johnson’s “Cruising the Fossil Freeway”: Standing nearly six feet at the shoulders when on all fours, this 1,400-pound bruin was a long-legged killing machine that would make a grizzly look like a sissy. Given the size of their limbs and the nature of the Late Pleistocene landscape, short-faced bears were probably open-ground predators that chased, caught, and ate bison and horses. A bear that can run down a horse on an open field is a scary concept. But this image was not to last. Scientists began to take a second look at the “predatory uber bear”. Chief among them was a scientist at the University of Alaska Fairbanks, Dr. Paul Matheus. He performed an isotope analysis on an ancient Alaskan Arctodus bone and found that its diet was almost exclusively carnivorous. But this didn’t prove it was a predator, only that it was a meat eater. Matheus looked at the morphology of the bear’s legs and found that while they were good at supporting its weight, it lacked the joint dynamics and structural integrity to maintain a chase. In shorter words, while capable of impressive bursts of speed, Arctodus’ legs could break if it tried to turn too sharply due to its immense weight. Since herbivores employ a zig-zag pattern to escape, being unable to make sharp turns is a big problem for a predator. Matheus concluded that the bear’s long lanky limbs instead allowed it to move in a pacing gate, which is a very efficient way to get around. Matheus began to imagine Arctodus instead as a superb scavenger. Using highly efficient movement and a strong sense of smell, Arctodus could roam the countryside in search of carrion. But could Arctodus have survived on dead animals alone, something unheard off outside of soaring birds? Well maybe it did. Modern grizzlies are known to pirate wolf kills. But there were more than just wolves in Pleistocene America: saber-toothed cats, scimitar-toothed cats, giant lions (or jaguars), dire wolves, jaguars, and cheetah-like cats. Arctodus, Matheus argued, could have used its size and strength to scare any of these animals off their kills. And what if there was little left at the ice age dinner table? Matheus looked to the bear’s short skull and flat teeth. Shortening the skull allows for a stronger bite while flat teeth are ideal for crushing. What had been used as evidence for predation (a shortened skull) was now envisioned as a trait that allowed Arctodus to break open bones to access the highly nutritious marrow inside. Arctodus, he argued, was not a super predator but a super scavenger. And to be honest, I was hooked. In a bizarre twist of fate, I was more fascinated by the concept of this animal as a giant trash picker than as an insatiable terror. To my feeble mind Matheus’ arguments made sense: being unable to pursue prey, this bear was well equipped to search the land for carrion and there were plenty of predators to facilitate carcass theft. To me, this scavenging hypothesis made Arctodus unique not just among bears but among carnivores in general. No other large carnivores could be perceived as subsisting on dead meat alone. But again, things made sense to my naïve thinking: it couldn’t catch prey because it couldn’t turn well (speed may not be essential to predators, but maneuverability sure is). Because this animal had flat teeth ideal for crushing and grinding (instead of the pointed teeth of T. rex) and also because there were plenty of other animals to fill the predator role, Arctodus seemed like a shoe in for the role no one thought possible: that of a super scavenger. This hypothesis even affected (or infected, I’ll let you decide) my way of looking at things. A couple years ago Alton mentioned that a paper presented by Blaine Schubert at the Society for Vertebrate Paleontology meeting discussed a study of changes in tooth shape and body size changes in Arctodus over time. As time went on, Arctodus got bigger and the anterior grinding teeth got relatively larger, suggesting a change in diet. I had suggested (naively, it now appears) that this increase in tooth size may have been an adaptation for breaking open bones. And recently I thought about another way of looking at the scavenging bear idea: damage on herbivore bones. To the extent of my knowledge there are at least four instances where Arctodus may have been dining on the remains of the dead: A southern mammoth skeleton from Anza Borrego in California, a Columbian mammoth skeleton from Huntington Reservoir in Utah, a mammoth heel bone from Saltville in Virginia, and a mastodon femur from Kentucky (there may be more, but this is all I have read about). This may not seem like much but I’m going to go out on a limb here and compare it with bone pathologies of another kind: battle damage in Native Americans. In the cultural anthropology class I took over a year ago, we were given an article titled “Prehistory of Warfare”, which talked about warfare in stone-age societies. We can often tell if a person died in war by tell tale marks on their skeleton: fractures and crushed bone indicate clubs; narrow grooves were most likely caused by axes; and scratches in odd places, as well as embedded points, demonstrate death by arrows. Now interestingly, the highest incidence of war related death as indicated by skeletal evidence comes from California. While California is often thought of as a hippie paradise, as much as 30% of male remains from the first centuries A.D. had wounds and death blows resulting from violent attacks. It is also noted that half that number of women from the same period show similar injuries. The article goes on to say that “When we remember that not all warfare deaths leave skeletal evidence, this is a staggering number”. My point? Museum displays and classroom lectures alike talk about how unlikely it is for a bone to become fossilized. I think what could be done is look at all bones thought to have carnivore trauma and try to determine who made what. A high amount of damage attributed to Arctodus could indicate a high amount of scavenging. And like the ancient wounds, not all scavenging would leave traces behind on the bones. And when you consider all the bones that wouldn’t have made it into the fossil record, this could indicate Arctodus was doing a buttload of dumpster-diving. What’s also interesting to note is all the instances of inferred scavenging are bones from proboscideans, the biggest animals on the landscape. Now I don’t know if scavenging evidence on the Huntington Reservoir mammoth comes from tooth marks or the fact that a couple Arctodus bones were found alongside it. Though it’s presence at the site of a mammoth carcass may be some indication: Arctodus fossils have also been found alongside mammoths at Hot Springs, South Dakota and at Saltville, Virginia. But seeing as how paleontology is reliant on hard evidence, this entire paragraph is just stupid meaningless speculation on my part. I have rambled on at length about how fascinating the idea of Arctodus was a scavenger is, but it is all for naught. The giant, short-faced bear that ran around on long legs trolling for flesh apparently never existed. Recent studies have shown that everything that ever made Arctodus unique have all been faulty observations. First off, it wasn’t a giant. The bear’s odd proportions have made it difficult to pin down its size but the consensus now appears to be that the figures of 1800 pounds or more are unfounded. “Fossil Treasures of the Anza-Borrego Desert” notes that studies by a fellow named Kurten used full body length to estimate that females weighed between 550 and 614 pounds while males weighed in around 770-825 pounds. His femoral cross-section analysis put females at around 594-638 pounds. Even though it cites a specimen from Utah weighing about 1364-1452 pounds, it is noted that this is a particularly large individual. It has been argued that because Arctodus was lanky it was not as massive as other bears; therefore the estimates of one ton are erroneous. Many think now that Arctodus rarely exceeded 1200 pounds in males, making it no larger than a brown bear. But the “fang corkers” were just getting warmed up. A paper released a year ago really went to town on the short-faced bear. They found that it didn’t have as long a set of legs as people originally thought. They argued that it wasn’t proportionally different than other bears and that the long legs are something of an optical illusion caused by its short back (Brian Switek notes that modern bear skeletons do look a big leggy themselves). Given this new information, the arguments that its long legs allowed it to run down prey or cover vast tracks of land were now irrelevant. The researchers also found that it wasn’t a short-faced bear either. Again, when compared to other bears and other carnivores, Arctodus’ skull was proportionally no different. This too may be an optical illusion caused by its deep skull. And diet? They suggest that Arctodus best be viewed as an omnivore who occasional ate meat like modern brown bears. But what about those isotope studies that showed it almost exclusively ate meat? The authors contend that the specimens used are all from Alaska and thus only demonstrate that that particular population ate meat and thus should not be used to generalize an entire species roaming a continent full of different environments (Alaska is often portrayed as a steppe environment. Perhaps the Arctodus up there had to rely more on meat because suitable plant food was not available). Arctodus, the once mighty king of the ice age, was reduced to a run of the mill ursid. I know this sounds pessimistic (did I mention I suffer a mental illness ?), but what is so special about Arctodus now? Everything that ever made it unique: size, long legs, a short face, a carnivorous diet (whether through active predation or scavenging), has all been shown to be false. Pretty much it becomes like any other bear. I mean, I get excited over bison or horse fossils, which are no different from their modern relatives. But they are special at least because they are found in places they no longer live in. To have an animal usually associated with far away exotic locations found right here makes them unique. But when it comes to Arctodus… so what? We still have bears in North America. Hell we have three species of bears. And it’s possible existence on the Central Coast wouldn’t too much of a boost either, seeing as we had the equally big and ecologically similar grizzly bear roaming the place in historic times (it’s how the town of Los Osos got its name. Its full name, Canada de Los Osos, means “valley of the bears”). It seems Arctodus’ only claim to fame now is that it’s an extinct bear and we got its biology and ecology horribly wrong. Had its fangs corked? I’d say it’s effectively been castrated. They say that the bigger they are the harder they fall. And Arctodus sure has fallen hard. It went from uber bear to ultimate scavenger to just another bear. Whereas T. rex survived its fang corking, Arctodus was knocked off his pedestal for good. But this is the way science works. It’s not about what you want to believe… it’s about what the evidence says. And the evidence says that Arctodus wasn’t all that different from other bears. I know I will probably get flak for not being able to still appreciate it. I still do, but for reasons I don’t understand, Arctodus has lost most of its grandeur and wonder. I will still enjoy seeing its fossils in my museum hopping, but I can’t help but feel like the ice age has lost one of its most fascinating aspects.
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Post by brobear on Apr 1, 2017 19:27:00 GMT -5
johnhawks.net/weblog/reviews/genetics/non-primate/short-faced-bears-mitchell-2016.htmlShort-faced bear convergence and the diversity of American extinct bears 20 Apr 2016 A neat new paper by Kieren Mitchell and colleagues in Biology Letters has an mtDNA phylogeny for some extinct bears of the Americas. The main conclusion is that the giant short-faced bears of North America and South America evolved convergently from smaller ancestors; earlier systematists had generally considered them to be sister taxa. The first paragraph gives a great review of the past diversity of this group of bears: The spectacled bear (Tremarctos ornatus) is the only living member of Tremarctinae, a previously diverse group of bears endemic to the Americas. The now-extinct Pleistocene diversity of Tremarctinae comprised the Florida spectacled bear (Tremarctos floridanus), South American short-faced bears (Arctotherium—five species; [1]) and North American short-faced bears (Arctodus—two species; [2]). These species ranged in size from the relatively small Arctotherium wingei (approx. 150 kg; [3]) to the giant short-faced bears Arctodus simus and Arctotherium angustidens, which may have attained body masses exceeding 1000 kg [4,5]. In addition, tremarctine bears displayed a diversity of foraging strategies, ranging from carnivorous/omnivorous (e.g. Arctodus simus, Arctotherium angustidens) to largely herbivorous (e.g. Arctotherium wingei, T. ornatus) [6–9]. The evolution and biogeography of this diverse group of bears is enigmatic, and currently lacks a robust phylogenetic framework. I had no idea of the past phylogenetic diversity of bears of the Americas, it seems like a really cool story. Here’s the phylogeny from the paper by Mitchell and colleagues, with all the species included:
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Post by brobear on Apr 1, 2017 19:31:10 GMT -5
Continued.... Figure 1 from Mitchell et al. 2016. Original caption: Relationships among tremarctine genera resulting from phylogenetic analysis of our mitochondrial genome dataset. Nodes reflect mean age estimates, whereas grey bars reflect 95% highest posterior densities (HPDs). Branch support values (BEAST posterior probability/RAxML bootstrap %) are given for each clade. The approximate temporal range of taxa of interest (see main text) is plotted based on the fossil record, and coloured according to distribution (North America, blue; South America, red). The extant taxon is marked with an asterisk.
The common ancestors of the Arctodus and Arctotherium clades lived in the Early Pliocene. This means that their Late Pleistocene representatives were separated by around 8–10 million years of evolutionary time. Looking at this as a paleoanthropologist, I’m tempted to compare to other similar instances of dietary convergence. For example, the robust australopiths have been argued to represent dietary convergence upon a large-molar and molarized premolar morphology, with small canine and incisor teeth, and large jaw muscles. They last existed during the later part of the Early Pleistocene, and if they were convergent in their anatomical configuration, their common ancestors may have lived in the Middle Pliocene. In this case their divergence may represent some 4 million years of evolutionary time.
Of course, that’s assuming that they are not truly sister taxa. Some evidence points in the direction of convergence, and with such clear demonstrations of convergence in other large mammal omnivore taxa, I don’t think we should rule it out.
The discussion of Mitchell and colleagues’ paper suggests an evolutionary scenario in which Arctotherium reached South America at around the same time as other members of the Pleistocene carnivore guild, including the sabretooths Smilodon and Homotherium and the modern puma and jaguar. The large-bodied Arctotherium first occurs with these predators, with no small-bodied precursor known from the fossil record of South America. They suggest that Arctodus in North America may have evolved large body size with a similar turnover of the carnivore community, in this case after the extinction of large scavengers like Agriotherium and Borophagus and the first introduction of bison into North America.
Obviously these are hypotheses to test further with better fossil samples, but I find them provocative because they do not suggest convergence after vicariance and slow adaptation to changing ecological conditions, the scenario usually described for hominin diversity in the Late Pliocene of Africa. The scenario sketched here for the bears is dynamic. A smaller-bodied Arctodus shifted to larger body size and greater scavenging when the herbivore and carnivore community of North America turned over in the Early Pleistocene. Meanwhile, Arctotherium rapidly entered an empty large scavenger niche as it dispersed along with the large cats into South America. The appearance of Arctotherium is then a parapatric event, and the establishment of the two large-bodied bear lineages in North and South America is due to the chance founding and rapid selection within one species with huge dispersal potential. This is not the isolation of two lineages in relative cul de sacs; it is the effect of rapid adaptation and a relatively small contact zone between the two genera. The weakness of any geographic and ecological barrier is further reinforced by the later dispersal of the extant South American spectacled bear, the relatives of which remained in North America from the Late Pliocene through most of the Pleistocene.
Reference
Mitchell KJ, Bray SC, Bover P, Soibelzon L, Schubert BW, Prevosti F, Prieto A, Martin F, Austin JJ, Cooper A. 2016. Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America. Biology Letters doi:10.1098/rsbl.2016.0062
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Post by brobear on Apr 1, 2017 19:33:13 GMT -5
www.beringia.com/exhibit/ice-age-animals/giant-short-faced-bear GIANT SHORT-FACED BEAR Ice age short-faced bears were the largest mammalian land carnivore to ever live in North America. These bears were nearly 1.5 metres high when walking normally, but stood about 3.4 metres tall when on their hind legs. They could have had a vertical reach of more than 4.3 metres. This is about one and a half times the size of a present-day Kodiak grizzly bear! Given its huge size and taste for meat, the short-faced bear has a surprising evolutionary history. Their closest living relative is the spectacled bear (Tremarctos ornatus), which lives among the trees in the mountainous regions of western and northern South America. Spectacled bears have short, broad faces like the ice aged short-faced bear but are nearly entirely herbivorous, preferring leaves, fruit and other vegetation. Yukon's Largest Hypercarnivore? There is some debate regarding the diets and behaviour of the ice age short-faced bear. Given its huge body stature, large molars and canine teeth, it is tempting to view them as menacing predators. However, investigation of their fossil skeletons reveals a much different picture. A prominent feature of the short-faced bear is their remarkably long, thin limb bones and feet that supported a heavy torso. These limbs were adapted for efficient long-distance pacing, rather than the explosive acceleration and high speed pursuits typical of other large predators, like lions. The limbs and feet of a short-faced bear could not support their large bodies for the rapid acceleration or sudden changes in direction necessary to take down a fleeing bison or horse. The cranium also provides some clues to short-faced bear behaviour. The nasal opening is very large, suggesting they had a pronounced sense of smell. This, combined with their long limbs, point to the short-faced bear as a solitary, wide-ranging scavenger of carcasses. Rather than killing on their own, the short-faced bear would probably smell the scent of meat in the wind, follow it to the carcass, chase off the lions or wolves, and dine on the leftovers. Their large cheek teeth were probably effective at cracking long bones for their marrow and sharp fangs could deflesh the carcass. The chemistry of short-faced bear fossil bones from Yukon and Alaska indicate a diet nearly completely composed of meat. This model of the short-faced bear's hyper-carnivorous scavenging, however, is not universally accepted. Some scientists have recently suggested that the short-faced bear was neither particularily long-limbed nor short-faced, and propose that they were omnivorous, like most bears are today. More evidence, including new short-faced bear bones found in Yukon will be needed to help solve this question.
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Post by brobear on Apr 1, 2017 19:56:45 GMT -5
www.researchgate.net/publication/223390695_The_fossil_record_of_South_American_short-faced_bears_Ursidae_Tremarctinae Abstract The present study includes a review of the geographic and stratigraphic distribution of short-faced bears (Ursidae, Tremarctinae) in South America. In addition, the authors discuss biogeographic hypotheses regarding the origin of South American tremarctines. The Tremarctinae subfamily is distributed exclusively in America, from Alaska to southern Patagonia. Its biochron comprises the temporal lapse between Late Miocene and recent times; the first record of Tremarctinae in North America corresponds to the Hemphillian and the last to the Rancholabrean. In South America, the first record corresponds to the Ensenadan. In the present day, it corresponds to the only living tremarctine, the ‘Andean Bear,’ but short-faced bears became extinct during the early Holocene. The extinction of short-faced bears in North and South America appears to have been approximately synchronous. Finally, the fossil record in South America indicates species turnover between the Ensenadan and Bonaerian, during which time the giant species Arctotherium angustidens was replaced by Arctotherium tarijense, Arctotherium bonaeriense, and Arctotherium vetustum (and probably Arctotherium wingei).
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Post by brobear on Apr 1, 2017 20:05:26 GMT -5
eol.org/pages/4441505/detailsGiant short-faced bears belong to the Ursidae family, which also includes black bears, grizzly bears and polar bears. Arctodus simus was very large in size with a short body and long slender limbs. Arctodus simus had a short neck, a short broad snout and a low forehead. Giant short-faced bears lived during the middle and late Pleistocene (about 1.3 million to ~12,500 years ago), and were found in many different habitats in North America from the steppe-tundra to grasslands. Giant short-faced bears could have been carnivores (only ate other animals) or omnivores (ate both animals and plants). Recent studies suggest that Arctodus simus was a scavenger rather than a predator. Giant short-faced bears went extinct approximately 12,500 years ago. New information on the Giant short-faced bear is being discovered all the time and opening the debate on the behavior and life-style of this giant bear. The first giant short-faced bears appeared during the middle Pleistocene (about 1.3 million years ago), and were widespread throughout North America. They were found from Alaska and northern Canada to Mexico, and from California to Virginia. Giant short-faced bears belong to the Ursidae family, which also includes black bears, grizzly bears and polar bears. Arctodus simus was very large in size with a short body and long, slender limbs. Arctodus simus had a short neck, a short broad snout, and a low forehead with eyes that were set in the front of the skull. Its front and back feet pointed forward, which was different from most bears whose feet point inwards. It was also very light for its size and could move very quickly. The teeth of Arctodus simus were similar to the teeth of the brown bear. It had a front set of large canine teeth followed by many large, jagged molars. These teeth were used to cut into animal hide, tear and slice meat, and possibly grind coarse plant material. Giant short-faced bears were extremely large in size. They were 1.5m ( 4 feet 11 inches ) at the shoulder, over 3m ( 9 feet 10 inches ) when standing with a 4.2m ( 13 feet 9 inches ) vertical reach, and weighed about 500kg. ( 1100 pounds ). The size of Arctodus simus would vary depending on sex and location. Males were typically 15% bigger than females, and giant short-faced bears found in Alaska and the Yukon were much larger than individuals found in other locations. Giant short-faced bears lived during the middle and late Pleistocene (about 1.3 million to ~12,500 years ago), when the most recent ice ages took place. They were found in many different habitats in North America from the steppe-tundra to grasslands. Many fossil remains of Arctodus simus were also found in caves, and it appears that only the females lived in caves. What and how giant short-faced bears ate is hotly debated in the scientific community. Some think that Arctodus simus were carnivores, which means they only ate other animals. They ate large herbivores like bison, deer, horses and ground sloths. However, recent studies have found proof that Arctodus simus were omnivores, which means they ate both animals and plants. Initially, scientists thought that Arctodus simus was an extremely powerful predator that skillfully hunted its prey. Several recent studies of Arctodus simus suggest that its body was not suited to hunting and it was more likely a scavenger. A scavenger eats animals that have been killed by other predators. Rather than a predator, Arctodus simus was a super-scavenger. Scientists are still researching these theories to discover how this giant bear obtained its food and what it ate. Giant short-faced bears went extinct approximately 12,500 years ago. During this time the last ice age ended and many large herbivores (like mammoths and mastodons) began to go extinct due to the change in climate and increased hunting pressure by humans. Arctodus simus ate many large herbivores, and the disappearance of these herbivores could have played a large role in its extinction. There is some evidence that competition from brown bears for food also played a role in the extinction of Arctodus simus but scientists are still researching and debating this theory. What I learned about the woolly mammoth is that they live in the grasses lands in Europe, Siberia, and North America. They also live during the ice age times. Some wolly mammoths lived on small islands. Woolly mammoths also lived in Paul Island, Alaska until 5,706 years ago roamed on wrangle Island Siberia until about 3,700 years ago. Little is known about the behavior of Giant short-faced bears but from studying their fossils and their modern bear cousins, scientists can make a few educated guesses on their behavior. It is thought that Arctodus simus lived alone except for mothers with cubs and during mating times. Arctodus simus belongs to the Ursidae family, which also includes black bears, grizzly bears and polar bears. There is one other well-known species of Arctodus, Arctodus pristinus or the short-faced bear. Arctodus pristinus is a primitive bear, and could be the ancestor of Arctodus simus.
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Post by brobear on Apr 1, 2017 20:06:58 GMT -5
iceage.museum.state.il.us/mammals/short-faced-bear-0 Short-faced bear, Arctodus simus The giant short-faced bear, Arctodus simus, was an extremely large bear that occupied much of North America throughout the Pleistocene. It is often described as the largest Pleistocene land carnivore in North America, although several new studies suggest that this member of the Carnivora family may actually have been an omnivore (Figuerido et al. 2010; Meloro 2011; Sorkin 2006). As with most other large mammals in North America, the short-faced bear went extinct at the end of the Pleistocene. The giant short-faced bear has been subdivided into two subspecies, A. simus yukonensis and A. simus simus, based on extreme differences in body size (Kurten 1967). It has been postulated that the larger subspecies, A. simus yukonensis, was restricted to the northwest portion of the species' range - specifically, Beringia, western Canada and the northwestern U.S. However, as more larger-bodied individuals have been recovered from locations in the southern portion of the giant short-faced bear's range, it has been suggested that the observed variation in body size may be due in part to extreme sexual dimorphism in the species (Schubert 2010). In some locations, males may have weighed almost twice as much as females. Order: Carnivora (Dogs, Cats, Bears, etc.) Family: Ursidae (Bears) Statistics: Height: 1.5 m (5 ft) at shoulder; 3.35 m (11 ft) when standing on hind legs Weight: Average: 700-800 kg (1540-1760 lbs); Christiansen 1999 Females: 300-400 kg (660-880 lbs); Figuerido et al. 2010 Males: 800-1000 kg (1760-2200 lbs); Figuerido et al. 2010 Status: Extinct Physical Description: The giant short-faced bear was an enormous animal, larger than the modern grizzly or polar bears. It had very long, legs for a bear, and a relatively short body given its height. Its feet were also distinctive in that the toes faced forward rather than inward, as in other bears. As its name suggests, this animal had a short face and broad muzzle with very robust teeth, although recent research suggests that its face may not have been much shorter, proportionally, than its modern relatives (Figueirido et al. 2010). Habitat: Based on the distribution of the species during the late Pleistocene, the giant short-faced bear occupied a range of habitats with diverse climatic conditions, including open plains, steppe tundra, boreal forests, open grasslands and subtropical woodlands (Schubert et al. 2010). Diet: Over the years, the short-faced bear has usually been described as a super predator (Kurtén 1967) and/or scavenger (Matheus 2003), and occasionally as an omnivore (Baryshnikov et al. 1994) or even an herbivore (Emslie and Czaplewski 1985; Sorkin 2006). Isotopic studies on fossil remains from Beringia (Barnes et al. 2002; Bocherens et al. 1995; Matheus 1995) indicate that individuals from Alaska and the Yukon consumed a very high proportion of meat, although similar studies have yet to be published from the southern part of its range. In fact, one recent study (Figueirido et al. 2010) of the has suggested that while meat was undoubtedly a large part of their diet, the giant short-faced bear was probably a generalized omnivore, similar to modern North American brown bears (e.g., grizzly bears), and would have eaten a variety of foods, depending on what was available. More recently, a study that analyzed the mandibular geometry of numerous living and extinct members of the Carnivora family found that the structure of the short-faced bear's mandible most closely matches that of the herbivorous Spectacled bear (Tremarctos ornatus), suggesting that this very large bear may, in fact, have been more herbivorous than previously suspected (Meloro 2011). The giant short-faced bear was an enormous animal, larger than the modern grizzly or polar bears. It had very long, legs for a bear, and a relatively short body given its height. Its feet were also distinctive in that the toes faced forward rather than inward, as in other bears. As its name suggests, this animal had a short face and broad muzzle with very robust teeth, although recent research suggests that its face may not have been much shorter, proportionally, than its modern relatives (Figueirido et al. 2010).
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Post by brobear on Apr 1, 2017 20:11:03 GMT -5
www.bioone.org/doi/abs/10.1080/02724630903416027In 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 bonecracking 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. 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 ( 2200 pounds ) 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 Apr 19, 2017 20:47:49 GMT -5
Of the eight species of living bears, only the giant panda and the Andean bear are not members of the Ursus genus. Neither of these two bear species hibernate. We therefore have no reason to believe that the short-faced bears ever hibernated. Also, neither the giant panda nor the Andean bear are as comfortable nor as skilled at bipedal standing and walking as those of the genus Ursus.
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Post by brobear on Oct 12, 2018 10:46:28 GMT -5
rsbl.royalsocietypublishing.org/content/12/4/20160062 Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America Kieren J. Mitchell, Sarah C. Bray, Pere Bover, Leopoldo Soibelzon, Blaine W. Schubert, Francisco Prevosti, Alfredo Prieto, Fabiana Martin, Jeremy J. Austin, Alan Cooper Published 19 April 2016.DOI: 10.1098/rsbl.2016.0062 Abstract The Tremarctinae are a subfamily of bears endemic to the New World, including two of the largest terrestrial mammalian carnivores that have ever lived: the giant, short-faced bears Arctodus simus from North America and Arctotherium angustidens from South America (greater than or equal to 1000 kg). Arctotherium angustidens became extinct during the Early Pleistocene, whereas Arctodus simus went extinct at the very end of the Pleistocene. The only living tremarctine is the spectacled bear (Tremarctos ornatus), a largely herbivorous bear that is today only found in South America. The relationships among the spectacled bears (Tremarctos), South American short-faced bears (Arctotherium) and North American short-faced bears (Arctodus) remain uncertain. In this study, we sequenced a mitochondrial genome from an Arctotherium femur preserved in a Chilean cave. Our molecular phylogenetic analyses revealed that the South American short-faced bears were more closely related to the extant South American spectacled bear than to the North American short-faced bears. This result suggests striking convergent evolution of giant forms in the two groups of short-faced bears (Arctodus and Arctotherium), potentially as an adaptation to dominate competition for megafaunal carcasses. 1. Introduction The spectacled bear (Tremarctos ornatus) is the only living member of Tremarctinae, a previously diverse group of bears endemic to the Americas. The now-extinct Pleistocene diversity of Tremarctinae comprised the Florida spectacled bear (Tremarctos floridanus), South American short-faced bears (Arctotherium—five species; [1]) and North American short-faced bears (Arctodus—two species; [2]). These species ranged in size from the relatively small Arctotherium wingei (approx. 150 kg; [3]) to the giant short-faced bears Arctodus simus and Arctotherium angustidens, which may have attained body masses exceeding 1000 kg [4,5]. In addition, tremarctine bears displayed a diversity of foraging strategies, ranging from carnivorous/omnivorous (e.g. Arctodus simus, Arctotherium angustidens) to largely herbivorous (e.g. Arctotherium wingei, T. ornatus) [6–9]. The evolution and biogeography of this diverse group of bears is enigmatic, and currently lacks a robust phylogenetic framework. Previous palaeontological studies have considered the short-faced bears (Arctotherium and Arctodus) as forming a monophyletic clade [19–21]. The proportionally larger and wider molars of both Arctodus and Arctotherium set them apart from other bears [19–21], and the cranium and mandible morphology of Arctodus simus and Arctotherium angustidens are strikingly similar [6]. However, the similarities between Arctodus and Arctotherium could alternatively result from convergent evolution driven by adaptation to the same ecological niche and/or feeding behaviour, as dental and mandible characters are frequently correlated with diet [8]. Similarly, the huge size of Arctodus simus and Arctotherium angustidens may have been convergent, and linked to their ecology by allowing predation on large herbivores and competition for carcasses. Consequently, resolving the phylogenetic relationships among these taxa would have important implications for our understanding of body size and foraging strategy evolution in tremarctines. We sequenced a near-complete mitochondrial genome from a specimen of Arctotherium and compared these new data with previously published sequences from the extant spectacled bear T. ornatus, the North American giant short-faced bear Arctodus simus, and a number of additional outgroups.
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Post by brobear on Oct 12, 2018 10:47:56 GMT -5
CONTINUED: 2. Methods Analyses were performed on an Arctotherium femur collected from Cueva del Puma, Chile (complete right femur, no. 32104, Centro de Estudios del Hombre Austral, Instituto de la Patagonia, Universidad de Magallanes). DNA extraction and genomic library preparation were performed in the ancient DNA laboratory at the Australian Centre for Ancient DNA, University of Adelaide. The Arctotherium genomic library was enriched for mitochondrial DNA, and sequenced on an Illumina MiSeq; the resulting reads were assembled into a mitochondrial genome. We aligned the Arctotherium mitochondrial genome sequence to 13 previously published carnivoran sequences, used PartitionFinder v. 1.1.1 [22] to determine optimal partitioning and substitution models, and performed phylogenetic analyses with RAxML v. 8.2.0 [23] and beast v. 1.8.0 [24]. See the electronic supplementary material for detailed methods. 3. Results Our analyses recovered relationships among outgroup taxa that were consistent with previous genetic studies ([12,25], but see [26]). Within Tremarctinae, we recovered strong support for a clade comprising Tremarctos ornatus and Arctotherium to the exclusion of Arctodus simus (Bayesian posterior probability = 1.0, maximum-likelihood bootstrap percentage = 98%; figure 1). Our mean estimate for the time of divergence between Tremarctos and Arctotherium was 4.1 Ma (95% highest posterior density, HPD = 3.0–5.3 Ma), and 4.8 Ma for the most recent common ancestor of Tremarctos, Arctotherium and Arctodus (95% HPD = 3.6–6.2 Ma). In general, node age estimates from our molecular dating analyses were slightly younger than those of a previous study of ursid mitochondrial DNA [12], although our 95% highest posterior densities (HPDs) overlapped with theirs substantially for equivalent nodes. These differences likely arise from our less restrictive calibration on the root of the tree, which allowed for the possibility that the Eocene Parictis is not a true member of the bear lineage. Conversely, a study of nuclear DNA obtained dates for the radiation of Ursinae that were much younger than ours [26], likely as a result of our conservative constraint on the crown-age of Ursidae, which permitted this node to substantially predate its first unequivocal fossil representative (electronic supplementary material).
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Post by King Kodiak on Nov 4, 2018 10:23:07 GMT -5
The prehistoric bears are hard to classify, all we have are fossils, that is why there is some confusion. www.differencebetween.net/science/nature/difference-between-genus-and-species/South american short faced bear (Arctotherium) Family: Ursidae Subfamily: Tremarctinae Genus: Arctotherium North american short faced bear (Arctodus) Family: Ursidae Subfamily: Tremarctinae Genus: Arctodus Notice that the GENUS is different, but the SUBFAMILY is the same.
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Post by brobear on Nov 4, 2018 15:25:32 GMT -5
Both the living Andean bear and the Florida spectacled bear are more closely related to Arctotherium than to Arctodus. Also, The panda bears and Agriotherium are closer to the short-faced bears than to the genus Ursus.
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Post by King Kodiak on Nov 4, 2018 15:53:05 GMT -5
The prehistoric bears are hard to classify, all we have are fossils, that is why there is some confusion. www.differencebetween.net/science/nature/difference-between-genus-and-species/South american short faced bear (Arctotherium) Family: Ursidae Subfamily: Tremarctinae Genus: Arctotherium North american short faced bear (Arctodus) Family: Ursidae Subfamily: Tremarctinae Genus: Arctodus Notice that the GENUS is different, but the SUBFAMILY is the same. We have talked alot about this today, and i have been breaking my brain the whole day. As you can see, for these prehistoric bears they dont use “species”, they use subfamily and genus. The question is, does this mean that these two bears are the same species, but different subspecies?
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Post by King Kodiak on Nov 4, 2018 16:03:26 GMT -5
A genus can have many species, and its above species. The question is, are these 2 short faced bears the same species, but different subspecies? They are the same subfamily as you can see.
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