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North American Giant Short-faced Bear - Arctodus simus
#1
North American Giant Short-faced Bear - Arctodus simus

[Image: Giant-Short-Faced-Bear.jpg]

Scientific classification 
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Ursidae
Subfamily: Tremarctinae
Genus: Arctodus

Subspecies
There are currently two recognized subspecies;
1. Arctodus simus yukonensis : the large specimens of Alaska, Yukon, Nebraska, California (Irvington) and perhaps Utah. 
2. Arctodus simus simus : the smaller specimens of Rancho La Brea 

Arctodus simus, also known as the giant short-faced bear is an extinct species of bear. The genus Arctodus is known as the short-faced or bulldog bears. A. simus is likely the largest bear that ever lived. It was native to prehistoric North America from about 12.5-800 kya.

Range
A. simus was native to North America, where it ranged from the north central plains -- Alaska and Canada -- to central Mexico, and California to Virginia. It was the most common of early North American bears, being most abundant in California.

[Image: Short_Faced_Bear_Range.png]


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 the New World. The earliest member of the Tremarctinae was Plionarctos, which lived in Texas during the Pliocene Epoch, (2-5 mya). This genus is considered ancestral to Arctodus, as well as to the modern spectacled bear, Tremarctos ornatus. Although the early history of Arctodus simus is poorly known, it evidently became widespread in North America by the Kansan age (about 800 kya).

[Image: Arctodus.jpg]

Physiology
Arctodus simus stood as high as two meters (seven feet) at the shoulder on all four legs. When standing bipedally, the animal was over 3.3 m (10 feet) in total height, with a possible reach of almost 4.2 m (14 feet). It is estimated to have weighed 600-860 kg (1300-1900 pounds), around the same weight of its contemporary (or slightly larger) the grizzly bear. The largest specimens were found in Alaska and the Yukon Territory. Males were 20% bigger than females. It was the largest land predator during the Ice Age in North America. The skull was unusual due to its lack of a well-defined forehead and the presence of a short broad muzzle, resembling that of Panthera rather than that of any modern bears. The muscles which passed between the broad cheek bones to power the lower jaws were extremely well-developed and are thought to be adapted for bone crushing in order to obtain the rich marrow. An Arctodus lower jaw can be distinguished from those of the genus Ursus by the slanting ridge dividing muscle attachment areas. Rather than having a waddling gait like modern bear species, Arctodus had toes extending straight forward, presumably being able to move with greater ease. In addition, unlike Ursus, Arctodus had a passage on the lower inside portion of the humerus for a slip of muscle (entepicondylar foramen).

Arctodus had a very short, broad muzzle, the skull having an olfactory area twice as large as that of a grizzly, and this, along with its great height, likely allowed the bear to identify a carcass from much greater distances. The jaw bone was massively foreshortened as in a feline, allowing Arctodus to eat even bone and marrow.

[Image: BC_114_Short_faced_bear_with_insert.jpg]

It was distinguished from its cousin (and possible ancestor) Arctodus pristinus by its bigger, broader, more crowded teeth, its shorter face, and its relatively longer legs.

Analysis of A. simus bones show it occasionally suffered from diseases such as osteomyelitis, as well as tuberculosis-like and possibly syphilis-like infections.

Dietary habits
Analysis on Arctodus bones showed high concentrations of nitrogen-15, a stable nitrogen isotope accumulated by meat-eaters with no evidence of ingestion of vegetation. A. simus was an obligate carnivore, and as an adult would have daily required 16 kg (35 pounds) of flesh to survive.

Extinction
The giant short-faced bear became extinct some 12 kya, 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 on which it may have followed for its kills or depended on as prey).

[Image: 800px-ArctodusSimusReconstruct.jpg]


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#2
Prehistoric Bears Also Ate Everything And Anything

[Image: 090408170815_1_900x600.jpg]
Top: skull of the North American short-faced bear (Arctodus simus) from the Museum of Natural History in New York. Bottom: and skull of the European cave bear (Ursus spelaeus) from the Museum of Natural History in Berlin.
Credit: Photos courtesy of Borja Figueiro / SINC

ScienceDaily (Apr. 8, 2009) — By comparing the craniodental morphology of modern bear species to that of two extinct species, researchers from the University of Málaga have discovered that the expired plantigrades were not so different from their current counterparts. The cave bear, regarded as the great herbivore of the carnivores, was actually more omnivorous than first thought.

The 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.

The team of palaeontologists have reconstructed the trophic ecology, or eating habits, of two extinct bear species that lived during the Pleistocene (between 2.59 million and 12,000 years ago): the Short-faced Bear (Arctodus simus) of North America and the Cave Bear (Ursus spelaeus) of Europe. The morphometric analysis carried out on the eight bear species in existence today has confirmed that prehistoric bears were not fussy eaters.

'Knowing what the extinct bears ate is of utmost relevance to finding out about the evolution of carnivore niches in the Pleistocene when climatic conditions were changing', explains Borja Figueirido, lead author of the study and researcher for the Ecology and Geology Department of the Faculty of Sciences at the University of Málaga. Scientists have discovered that, even at that time, bears were 'great opportunists' thanks to their morphological and ecological flexibility.

The study, published recently in the Journal of Zoology, focuses on two species of prehistoric bear because scientists believed that they had disparate feeding preferences. It was presumed that the Short-faced Bear was a carnivore and the cave bear an herbivore; 'probably the most herbivorous species of the Ursus genus', asserts Figueirido.

'The study has revealed that the craniodental morphologies of these two bears are more suited to the omnivorous diet than the specialised diet previously put forward', the researcher points out.

Fossilised skulls, great biomarkers

The researchers studied the osteological material of the current species (skull and jaw) and the same anatomical elements of the fossilised remains of the extinct bears, conserved in various international museums.

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'.

Today there are cases of bears with specialised eating habits. From a morphological and ecological perspective, the Polar Bear (Ursus maritimus), exclusively carnivorous, and the Panda Bear (Ailuropoda melanoleuca), strictly herbivorous, have the greatest challenge to change their eating habits in the face of climatic change. 'Although not as specialised as that of a lion, if the few resources that the giant panda and the polar bear depend on were to disappear, their situation would be complicated', confirms Figueirido.

'The study has revealed that the craniodental morphologies of these two bears are more suited to the omnivorous diet than the specialised diet previously put forward', the researcher points out.

Story Source: Plataforma SINC. "Prehistoric Bears Ate Everything And Anything, Just Like Modern Cousins." ScienceDaily. www.sciencedaily.com/releases/2009/04/090408170815.htm (accessed December 31, 2016).




Journal reference:
1.Figueirido et al. Ecomorphological correlates of craniodental variation in bears and paleobiological implications for extinct taxa: an approach based on geometric morphometrics. Journal of Zoology, 2009; 277 (1): 70 DOI: 10.1111/j.1469-7998.2008.00511.x

Abstract
Relative warp analyses of landmarks describing cranial and mandibular shape are used for investigating patterns of morphological variation among extant bears (Mammalia, Carnivora, Ursidae) indicative of diet and feeding behavior. These patterns are used for deriving inferences about the autecology of two extinct species previously assumed to have had different dietary preferences, the North American giant, short-faced bear Arctodus simus and the Eurasian cave bear Ursus spelaeus. Results reveal a set of shared craniodental traits among the herbivorous bears, including short and vaulted skulls with well-developed zygomatic arches, lateralized orbits and small canines, concave jaws with a highly positioned condyle, large moment arms for the temporalis and masseter muscles, and long cheek teeth. In contrast, those bears that consume animal resources have long skulls with small zygomatic arches, frontalized orbits and well-developed canines, and long jaws with a deep mandibular symphysis, low muscle leverages, a condyle situated at the level of the tooth row and reduced cheek teeth. The craniodental morphology of omnivorous bears is intermediate between those of faunivores and herbivores. This is also the case of the short-faced bear and the cave bear, which suggests that previous reconstructions of the feeding ecology of these extinct species (highly carnivorous for A. simus and herbivorous for U. spelaeus) should be revised.

http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.2008.00511.x/abstract
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#3
New Weight Estimates - not so giant?

"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."
http://accpaleo.wordpress.com/2011/02/27/central-coast-critters-arctodus/ 





Was the Giant Short-Faced Bear a Hyper-Scavenger? A New Approach to the Dietary Study of Ursids Using Dental Microwear Textures
Shelly L. Donohue, Larisa R. G. DeSantis, Blaine W. Schubert, Peter S. Ungar

Abstract
Dramatic environmental changes associated with global cooling since the late Miocene, and the onset of glacial-interglacial cycles in the Pleistocene served as a backdrop to the evolutionary radiation of modern bears (family Ursidae). These environmental changes likely prompted changes in food availability, and triggered dietary adaptations that served as motive forces in ursid evolution. Here, we assess correspondence of dental microwear textures of first and second lower molars with diet in extant ursids. We use the resulting baseline data to evaluate the hypothesis that the Pleistocene giant short-faced bear, Arctodus simus, was a bone consumer and hyper-scavenger at Rancho La Brea, California, USA. Significant variation along the tooth row is consistent with functional differentiation, with the second molar serving as a better dietary recorder than the first. Results evince significant variation among species: carnivorous and omnivorous ursids (Ursus maritimus, U. americanus) have significantly higher and more variable complexity (Asfc) than more herbivorous ones (Ailuropoda melanoleuca, Tremarctos ornatus, U. malayanus), and A. melanoleuca is differentiated from U. maritimus and U. americanus by significantly higher and more variable anisotropy (epLsar) values. Arctodus simus from Rancho La Brea exhibits wear attributes most comparable to its closest living relative (T. ornatus), which is inconsistent with hard-object (e.g., bone) consumption, and the hypothesis that short-faced bears were bone consuming hyper-scavengers across their range.

[Image: journal.pone.0077531.g001&representation=PNG_M]
Figure 1. Phylogeny and dietary ecology of Ursidae including three-dimensional microwear photosimulations of analyzed taxa.
Phylogeny modified from Krause and colleagues [1] with an update to polar bear origination from Miller and co-authors [2]. The shaded bar highlights the rapid evolutionary radiation of bears, which correlates with climatic and environmental changes. Numbers indicate divergence dates in millions of years. Po, Pliocene; Ps, Pleistocene; H, Holocene. A–F are three-dimensional photosimulations of lower second molars taken at 100× magnification, length and width measurements of photosimulation F correspond to all. A. Ursus maritimus, NMNH 512117; B. Ursus americanus, UF 28436; C. Ursus malayanus, NMNH 151866; D. Tremarctos ornatus, NMNH 271418; E. Ailuropoda melanoleuca, NMNH 259028; F. Arctodus simus, LACMHC 1292.

[Image: journal.pone.0077531.g002&representation=PNG_M]
Figure 2. Depiction of ursid tooth facets analyzed for dental microwear.
Pictured: Ursus americanus (NMNH 198391), left mandible, buccal view, anterior is to the right. Shading indicates scanned regions. A. Second molar (m2) hypoconulid, mesial facet. B. First molar (m1) protoconid, buccal facet.

[Image: journal.pone.0077531.g003&representation=PNG_M]
Figure 3. Bivariate plot of complexity (Asfc) vs. anisotropy (epLsar) for lower second molars of ursids.
Polygons enclose data points.

[Image: journal.pone.0077531.t001&representation=PNG_M]
Table 1. Descriptive statistics of dental microwear attributes used to differentiate diet in bears.

[Image: journal.pone.0077531.t002&representation=PNG_M]
Table 2. Pairwise differences for microwear attributes of extant ursid lower second molars (Dunn’s procedure).

[Image: journal.pone.0077531.t003&representation=PNG_M]
Table 3. Pairwise differences of variance between lower second molars of all extant and extinct bears.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0077531 





Giant prehistoric bears evolved to fill scavenger gap

ABC Science By Anna Salleh
Updated about 2 hours ago

Ancient bears evolved to become giants so they could scavenge prey killed by others, a new study suggests.

Key points
  • Giant carnivorous bears roamed the Americas in ancient times

  • Their only living relative is a much smaller vegetarian

  • The giant bears evolved so they could dominate scavenging
The findings, published in the Royal Society journal Biology Letters, found that short-faced bears weighing over a tonne evolved independently in North and South America.

"We think their large size was a particular advantage that let them exploit carcasses from other predatory species," said evolutionary biologist Dr Kieren Mitchell from the University of Adelaide, who was lead author on the new paper.

Dr Mitchell said giant bears from the Tremarctinae group were among the largest land-based carnivorous mammals that ever lived. The bears roamed the grasslands and open woodlands of the New World from about 2.5 million years ago to about 12,000 years ago.

The animals strode around on their long legs, eating whatever they could find, but the shape of their teeth suggests they were better adapted for eating meat than plants, he said.

At the time the giant bears lived there would have been lots of large herbivores, such as bison and mammoth in North America, and horses and giant ground sloths in South America.

There would also have been specialised predators like wolves, lions and sabre-tooth cats, but there would have been no specialised scavengers, Dr Mitchell said.

"This opened up a bit of a gap that looks like the bears took advantage of separately in North and South America."

By turning into giants, the bears could spot vultures circling and quickly get to any newly-killed prey and get a meat meal without the risk and energy of having to do their own hunting.

"They could just get anything out of the way that was there originally, and just tuck in," Dr Mitchell said.

Genetic study of living and extinct bears

The giant bears in North America belonged to the genus Arctodus while in the South America it was the genus Arctotherium.

Both were members of a group, which today has only one living member — the much smaller and largely vegetarian Andean spectacled bear (Tremarctos ornatus).

To shed light on the evolution of the giant bears, Dr Mitchell and colleagues compared the mitochondrial DNA of Arctotherium and Arctodus bears with the DNA of the living spectacled bear.

This included DNA extracted from a femur of a giant bear found in a cave in Chile and DNA from the largest species of North American giant bear Arctodus simus.

The genetic analysis showed the South American giant bear was more closely related to the modern bear, even though it looked more like the North American giant bear, indicating the two extinct species evolved independently as an adaptation to exploit a similar ecological niche.

http://www.abc.net.au/news/2016-04-20/prehistoric-bears-became-giants-to-dominate-scavenging/7338852




Journal Reference:
Kieren J. Mitchell, Sarah C. Bray, Pere Bover, Leopoldo Soibelzon, Blaine W. Schubert, Francisco Prevosti, Alfredo Prieto, Fabiana Martin, Jeremy J. Austin, Alan Cooper Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America 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.


http://rsbl.royalsocietypublishing.org/c...4/20160062

Attached to this post:[Image: attach.png] Ancient_mitochondrial_DNA_reveals_convergent_evolution_of_giant_short_faced_bears__Tremarctinae__in_North_and_South_America.pdf (226.9 KB)





Taipan Wrote:
Ursus arctos Wrote:From the supplementary materials of the article "Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was":
[Image: Arctodussimus.png]
[Image: Arctodussimusskulls.png]
Bear FM 30492 (the fourth down in the series of pictures):
Skull length: 496 mm
Zygomatic width: 362.82 mm

Score= 33.8 inches

Skull height not listed, but visibly very tall.

Here is the study:

Journal Reference:
Figueirido; et al. (2010). "Demythologizing Arctodus simus, the 'short-faced'". Journal of Vertebrate Paleontology. 30 (1): 262–275. doi:10.1080/02724630903416027

ABSTRACT
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. 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.

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 the same line of reasoning, we agree with Sorkin (2006) that the dental characters recognized by Kurten (1967) as evidencing a morphological trend towards carnivory are very ambiguous, and that the previous interpretations of A. simus as a scavenging specialist (Matheus, 1995) are based exclusively on the analysis of bone collagen isotopes, which do not allow distinguishing among highly carnivorous species from those more omnivorous that consume a relatively high percentage of flesh (Sorkin, 2006).
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.
We do agree with Matheus (1995) that the huge body size of this extinct bear probably facilitated kleptoparasitism of ungulate carcasses. In fact, the ecological circumstances in the Pleistocene of North America differed from those of today, due to the presence of saber-tooth cats in the carnivore guild. These predators were probably less able to exploit a carcass than modern pantherine cats, because their dentition was even more specialized
for meat slicing (Christiansen, 2008). This, combined with jaw gape restrictions resulting from their hypertrophied upper canines (Emerson and Radinsky, 1980) and weaker bite forces compared to pantherines (McHenry et al., 2007), probably forced saber-tooths to consume exclusively soft tissues (Palmqvist et al., 2007). Such highly derived craniodental anatomy probably resulted in the availability of relatively large amounts of flesh
and all bone nutrients in their kills. These unexploited resources might have opened broad opportunities of scavenging for other species such as A. simus (for a review on the ecological connection between saber-tooths and the giant bone-cracking hyenas in the Old World, see Arribas and Palmqvist, 1999). Under this ecological scenario, it would be reasonable to assume that meat and bone marrow were likely to be the primary food resources for some Northern populations of A. simus (Matheus, 1995), in which the survival during the cold season could have depended on the regular scavenging of ungulate carcasses, as in Alaskan brown bears (Pasitschniak-Arts, 1993). Such inference is in agreement with the climatic cycles of the Pleistocene, an epoch in which resource availability was frequently changing (Figueirido et al., 2009). However, this dietary niche should not be generalized for the entire biogeographic range of the species.
In any case, the paleobiology of the wrongly termed ‘shortfaced’ bear is far from being well understood. In our view, the current situation demands a deep taxonomic revision, including a more detailed inspection of the appendicular adaptations of ursids and perhaps the exploration of skull biomechanics using finite element analysis. Such approaches could contribute crucial insights into the paleobiology of this emblematic fossil species.
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#4
Ursus arctos Wrote:The longest known humerus and ulna length measures for A. simus I am aware of:
Humerus: 64.6 cm
Ulna: 59.1 cm

Both of these are far above average size.

EDIT:
Proportions don't seem right. Ulna is actually not that far above average. IIRC, the empty circles= Yukon specimens, while filled = a different population (California?):
[Image: ulna2.jpg]
In which case that ulna length figure is regularly exceeded.

73 cm for the humerus however seems far to long.
From "The Largest Known Bear" by Soibelzon, et al (2011), citing Merriam and Stock (1925), mean (range) lengths of a sample of 13 A. simus humerus was 46.5 (43.8-59.4) cm.

Ursus arctos Wrote:From Sorkin's 2006 article on Ecomorphology of the giant short faced bears, measurements are:
Average ulna length of specimens AMNH and FMNH PM 24880: 450.0 mm

Humerus length of AMNH: 539.0 mm
Humerus length of FMNH PM 24880: 580.0 mm
Average of humerus lengths for these two specimens is thus 559.5 mm.

Ulna/humerus length= 80.4%


Ulna/humerus length you gave for that drawing:
61/73= 83.6%



I wouldn't say the ulna is especially short in that drawing; it is similar in length or a little longer than what is indicated by Sorkin.




Radius/humerus length you gave for the drawing, however:
50/73= 68.5%

Is relatively short. Radius/humerus length for a specimen of A. simus provided by Sorkin in the same article as above: 75.2%
This is from specimen FMNH PM 24880 (the one with a 580 mm long humerus).

The brachial index of A. simus is very low compared to most other carnivores; P. leo, for example, ranged from 86.9–94.8% (n=4), P. tigris from 80.5–84.7 (n=6), and C. crocuta 107.1–110.4 
(n=3) so in actuality A. simus really short have relatively short distal limb segments.

Flesh Wrote:Short-faced bears, largest carnivores in the Ice Age, became omnivores to survive

Date: March 22, 2018
Source: Asociación RUVID
Summary: Based on the analysis of fossil teeth, a study shows that short-faced bears (Arctodus simus), the largest carnivores in the Ice Age, became omnivores to survive.

Based on the analysis of fossil teeth conducted by researcher Alejandro Romero, from the University of Alicante's Departament of Biotechnology, a study shows that short-faced bears (Arctodus simus), the largest carnivores in the Ice Age, became omnivores to survive. The study, led by the University of Málaga (UMA) researcher Borja Figueirido, was recently published in the journal Scientific Reports.

The scientific community previously thought that this extinct animal from North America was exclusively carnivorous, but, as pointed out by Mr Figueirido, "we dethroned the largest hypercarnivorous mammal ever to roam the Earth." He adds: "Our results also suggest that the Arctodus simus population in southern North America was more omnivorous than the highly carnivorous populations in the north-east."

Specifically, after the analysis involving microscopic techniques and virtual models developed by the UA researcher, carious lesions caused by carbohydrates, present in plants, were found in the dental remains discovered at the La Brea Tar Pits site in Los Angeles, California, described by Alejandro Romero as "one of the most paradigmatic sites to study fossil mammals from the Pleistocene in North America."

The UA researcher also highlights that "this is an interesting study, as caries were found for the first time in the dental remains of Arctodus simus, which proves that they could adapt to plants present in their diet as a result of climate change or competition with other predators."

Other participants in the study included vertebrate ecology and palaentology experts like Alejandro Pérez-Ramos, from the UMA, and researchers from the Natural History Museum and the La Brea Tar Pits Museum of Los Angeles, USA.


Story Source:

Materials provided by Asociación RUVID. Note: Content may be edited for style and length.

Journal Reference:

1. Borja Figueirido, Alejandro Pérez-Ramos, Blaine W. Schubert, Francisco Serrano, Aisling B. Farrell, Francisco J. Pastor, Aline A. Neves, Alejandro Romero. Dental caries in the fossil record: a window to the evolution of dietary plasticity in an extinct bear. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-18116-0



https://www.sciencedaily.com/releases/20...112509.htm
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