Agriotherium africanum

[brobear]

Finite element analysis of ursid cranial mechanics and the prediction of feeding behaviour in the extinct giant Agriotherium africanum

C. C. Oldfield1, C. R. McHenry2, P. D. Clausen1, U. Chamoli3, W. C. H. Parr3, D. D. Stynder4, S. Wroe3,*
Article first published online: 20 OCT 2011

DOI: 10.1111/j.1469-7998.2011.00862.x

© 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London
Issue Journal of Zoology
Journal of Zoology
Volume 286, Issue 2, page 171, February 2012

Abstract
Historically, predicting ursid feeding behaviour on the basis of morphometric and mechanical analyses has proven difficult. Here, we apply three-dimensional finite element analysis to models representing five extant and one fossil species of bear. The ability to generate high bite forces, and for the skull to sustain them, is present in both the giant panda and the gigantic extinct Agriotherium africanum. Bite forces for A. africanum are the highest predicted for any mammalian carnivore. Our findings do not resolve whether A. africanum was more likely a predator on, or scavenger of, large terrestrial vertebrates, but show that its skull was well-adapted to resist the forces generated in either activity. The possibility that A. africanum was adapted to process tough vegetation is discounted. Results suggest that the polar bear is less well-adapted to dispatch large prey than all but one of the five other species considered. 
 
       

[brobear]

www.wired.com/2012/10/researchers-chew-over-a-prehistoric-bears-diet/

Researchers Chew Over a Prehistoric Bear’s Diet

OF ALL THE bears to come and go during the group’s 23 million year old history, none had a bite more powerful than Agriotherium africanum – a ursid as large as today’s grizzly and polar bears that roamed Africa during the latest Miocene and earliest Pliocene epochs. In a new Journal of Zoology paper by C.C. Oldfield, Colin McHenry, and colleagues, virtual models used to run bite tests predicted that the fossil bear could bring its canines down with 4566 Newtons of force – the equivalent of about one thousand pounds of pressure. The question is why this huge extinct bear required such a powerful bite.

For some prehistoric creatures, it isn’t difficult to envision their feeding habits. Tyrannosaurus rex undoubtedly clamped its heavily-fanged jaws on struggling Edmontosaurus and rotting Triceratops, and so the dinosaur’s overwhelming bite strength makes sense given its hypercarnivorous lifestyle. But the connection between skull anatomy, bite force, and diet isn’t always so clear.

The skull of Agriotherium africanum looks like that of a dedicated carnivore. Much like Arctodus – a similarly-proportioned but distantly-related bear from the Pleistocene of North America – Agriotherium had a relatively broad, deep skull well-suited to handling the stresses and strains created by large, struggling prey. Then again, the same suite of features could have just as readily been employed to dismember carcasses or crunch tough plants, and some researchers have argued that Agriotherium, Arctodus, and similar bears were omnivores that often fed on carrion rather than chasing down large prey.

As Oldfield and co-authors point out, the remarkably high bite force Agriotherium brought to bear doesn’t allow us to distinguish between the hunting and scavenging alternatives. Having a powerful bite is just as useful to an active predator as to a saprovore. And modern bears only complicate efforts to reconstruct the lifestyle of Agriotherium.

When the researchers investigated the mechanical properties of skulls representing a giant panda, a brown bear, an American black bear, an Asian black bear, and a polar bear, there was no indication that bite force, alone, predicted carnivory. Quite the contrary. The mostly-herbivorous giant panda had the strongest bite force for its size, while the hypercarnivorous polar bear had among the lowest proportional bite force. In fact, Oldfield and collaborators deemed the polar bear as “among the poorest performers” in terms of being able to handle the stresses involved with killing and consuming large prey. Maybe this is because the polar bear eats a great deal of blubber from prey that can’t put up much of a fight on land, the researchers suggest, but the main point is that there is not a simple connection between being a predator and having a strong bite.

Despite the similarities between the Agriotherium and giant panda models, though, Oldfield and collaborators don’t think that the fossil bear was an herbivore. The cheek teeth of Agriotherium are better suited to slicing than to grinding vegetation, hinting that the bear regularly dined on flesh.
What remains unknown was how Agriotherium acquired that meat. “A. africanum was more than capable of dispatching very large vertebrate prey,” the researchers write, “but this does not mean that it did.” Like so many debates in paleontology, we are left trying to untangle what an animal was capable of from what that creature actually did.

[brobear]

www.outdoorhub.com/stories/2015/11/02/five-prehistoric-bear-species-mop-floor-modern-bears/

The bear with the crushing bite (Agriotherium africanum)

This bear is not all that special at first glance. It’s about as large as a modern grizzly, and except for the raccoon-like pattern on its face, it looks much like a grizzly as well. Yet one look at the skull of an africanum will tell a different story, as will a peek at its teeth. The africanum has the strongest bite of any bear, extinct or living, and it could crush straight through almost anything. Scientists believe that the bear evolved for this trait to handle the stress of struggling prey on its teeth, but over time the africanum found itself capable of crushing bone and muscle, making going for the vitals only a formality.
When this powerful bear was not hunting for itself, it munched through carrion and used its specialized jaw to severe off entire parts of prey to save for later. Scientists believe the africanum was a big fan of plants too, and this theory came from the fact that of all modern bear species, the giant panda has the greatest bite force for its size. Just like pandas, the ancient africanum may have used its oversized teeth to chew through hard plants. It is believed to have lived during the Miocene and was found across the world.

[Polar]

What does it mean "about as large as a modern grizzly"? Grizzlies are around 400-600 pounds, and Agriotherium was about same size as a polar bear too. Unless they are using popular media description of a 1000-pound grizzly bear to compare.

[tom]

Feb 1, 2018 16:58:38 GMT -5 Polar said:

What does it mean "about as large as a modern grizzly"? Grizzlies are around 400-600 pounds, and Agriotherium was about same size as a polar bear too. Unless they are using popular media description of a 1000-pound grizzly bear to compare.

According to Wikipedia Agriotherium was quite large (9 ft. Long and up to 1900 lbs) en.wikipedia.org/wiki/Agriotherium

"Agriotherium was about 2.7 metres (9 ft) in body length and weighed around 900 kg (1,980 lb), making it larger than most living bears"

So the quote "as large as modern day Grizzlies" would seem incorrect. He would have been considerably heavier than even a large Kodiak bear.

[brobear]

There are many varied definitions of the word "grizzly" which often causes confusion. Initially, the word grizzly meant only Ursus arctos horribilis ( the inland grizzly ). More recently, the term grizzly is used ( especially among Americans ) as any brown bear - Ursus arctos. I have books that refer to the Kodiak grizzly, the Russian grizzly, and the Gobi grizzly.
There are mature male grizzlies living today that measure more than nine feet long. Also, I believe that estimated weights of prehistoric animals are very often over-estimated. When Brutus, the grizzly pal of Casey Anderson measured 9 feet high/long, he weighed roughly 900 pounds. If Agriotherium averaged 9 feet long, he very likely averaged ( IMO ) about 1,000 pounds.

[tom]

Yeah I believe these weights are estimates from fossil remains. From those remains a body mass can be estimated. Two specimens that were estimated for body mass are as follows. Given specimen 1 was considerably smaller it likely was a very young individual. The length would also be an estimate unless a complete skeleton was used for measurement. It is possible that Agriotherium had a very large dense skeletal system would could give it added weight without necessarily the added length. Bite force it would seem is very high and on par with Short Faced Bear.

Two specimens were examined by Legendre and Roth for body mass.[5]
Specimen 1: 79.3 kg (175 lb)
Specimen 2: 652.6 kg (1,440 lb)

[brobear]

www.bbc.co.uk/nature/15559929

Ancient bear had the strongest bite
By Ella Davies
Reporter, BBC Nature

The largest bear that ever lived also had the strongest bite of any land mammal, say scientists.
Agriotherium africanum was a giant short-faced bear that became extinct five million years ago.
Reconstructions of the carnivore's skull revealed that it was well adapted to resist the forces involved in eating large prey.
By comparing the skulls of several species, scientists also found polar bears to have surprisingly weak bites.
Continue reading the main story
“
Start Quote
Our analyses show that it had the most powerful bite of any known terrestrial mammal”
Dr Stephen Rowe
University of New South Wales, Australia
The findings were published in the Journal of Zoology.
Dr Stephen Wroe from the University of New South Wales, Australia, and his team used CT scanners to create 3-D images of bear skulls. They scanned six species, ranging from a giant panda to a reconstructed fossil of A. africanum.
Using the computer generated models created by student Chris Oldfield, the researchers investigated how the skulls stood up to the forces that mimicked killing and feeding behaviours.
"Our analyses show that Agriotherium africanum had an enormously powerful bite - considerably greater than for the largest of living big cats, or any living bear," said Dr Wroe.
The extinct bear exerted the highest bite force with its large canine teeth. Of all the bears the team examined, its model showed the least strain through the skull when the researchers simulated the forces of biting an item of prey.
"Our analyses show that it had the most powerful bite of any known terrestrial mammal determined thus far," Dr Wroe told BBC Nature.

A comparison in skull stress for bears biting with their canines (a) A. africanum, (b) Asian bear, (c) black bear, (d) brown bear, (e) giant panda, (f) polar bear and (g) polar bear. Pink shows an area of high strain, while dark blue areas show no strain.
Results for another short-faced bear, the giant panda, were also notable; the animal's skull appeared to be well adapted to high levels of stress.
This might seem surprising for an animal with a diet strictly limited to plant material, but Dr Wroe pointed out that the panda had a large "grinding area" to chew through tough stalks of bamboo.
In comparison, A. africanum had the smallest grinding area of the bears analysed.
'Power to kill'

The researcher said that A. africanum may have been a "hypercarnivore" with an unparalleled level of meat in its diet for a bear.
"There has been considerable debate over the diet of A. africanum and other short-faced bears. Some have argued that these bears were more carnivorous than most living bears," said Dr Wroe.
"There can be no doubt that this beast had the power to kill almost anything it could get a hold of - it could also have chased any other predators off their kills; hence it could also have been a very effective scavenger."
"Its skull was well adapted to resist the forces that would have been generated under such extreme loads."

Fat-sucker
The study also revealed that the polar bear was a surprisingly "poor performer".
"It has a really surprisingly weak bite for its size - arguably the weakest among living bears," Dr Wroe told BBC Nature.
He pointed out that these huge carnivores tended to target relatively "easy-to-kill", blubbery prey, such as seals.
"It might be more correctly categorised as a specialised 'fat-sucker' than a real meat eater," he said.
The skull comparisons revealed that the polar bear had much shorter blade-like teeth for ripping flesh than the supersized A. africanum.
These extinct giants lived in Africa at the end of the Miocene epoch and into the Pleistocene - five million years ago - and measured up to 2.7m in length. ( 8 feet 10.5 inches ).

[brobear]

en.wikipedia.org/wiki/Agriotherium

Agriotherium was about 2.7 metres (9 ft) in body length and weighed around 900 kg (1,980 lb), making it larger than most living bears. Except for the extinct subspecies of modern polar bear Ursus maritimus tyrannus and Arctotherium, Agriotherium was along with the short-faced bear, Arctodus simus the largest member of terrestrial Carnivora. It had dog-like crushing teeth. Its primary diet was carnivorous and secondary was omnivorous possibly classifying this animal as mesocarnivore. With a body mass close to those of most large ungulates (bovines, cervids, camelids, and others), it is probable that Agrotherium could have preyed on these. Agriotherium also likely scavenged, and would not have been hesitant about stealing kills from such animals as the sabertooth cat Amphimachairodus, with whom it shared territory with in China and North America alike and the feliform Barbourofelis, which it lived alongside in Texas, as evidenced by fossil deposits at Coffee Ranch.

Body mass
Two specimens were examined by Legendre and Roth for body mass.

Specimen 1: 79.3 kg (175 lb)
Specimen 2: 652.6 kg (1,440 lb)
Bite strength
A 2011 estimate that compared the bites of a few selected bears, both extant and extinct, concluded that Agriotherium had the strongest bite-force of any mammalian land-predator yet estimated.

[brobear]

www.researchgate.net/publication/257591973_Tooth_Root_Morphology_in_the_Early_Pliocene_African_Bear_Agriotherium_africanum_Mammalia_Carnivora_Ursidae_and_its_Implications_for_Feeding_Ecology

Tooth root surface areas serve as proxies for bite force potentials, and by extension, dietary specialization in extant carnivorans. Here, we investigate the feeding ecology of the extinct large-bodied ursid Agriotherium africanum, by comparing its root surface areas (reconstructed with the aid of computed tomography and three-dimensional image processing) and bite force estimates, with those of extant carnivorans. Results show that in absolute terms, canine and carnassial bite forces, as well as root surface areas were highest in A. africanum. However, when adjusted for skull size, A. africanum’s canine roots were smaller than those of extant solitary predators. With teeth being the limiting factor in the masticatory system, low canine root surface areas suggest that A. africanum would have struggled to bring down large vertebrate prey. Its adjusted carnassial root sizes were found to be smaller than those of extant hard object feeders and the most carnivorous tough object feeders, but larger than those of extant omnivorous ursids and Ursus maritimus. This and the fact that it displayed its highest postcanine root surface areas in the carnassial region (rather than the most distal tooth in the tooth row) suggest that A. africanum consumed more vertebrate tissue than extant omnivorous ursids. With an apparent inability to routinely bring down large prey or to consume mechanically demanding skeletal elements, its focus was most likely on tough tissue, which it acquired by actively scavenging the carcasses of freshly dead/freshly killed animals. Mechanically less demanding skeletal elements would have been a secondary food source, ingested and processed mainly in association with muscle and connective tissue.

Tooth Root Morphology in the Early Pliocene African Bear.... Available from: www.researchgate.net/publication/257591973_Tooth_Root_Morphology_in_the_Early_Pliocene_African_Bear_Agriotherium_africanum_Mammalia_Carnivora_Ursidae_and_its_Implications_for_Feeding_Ecology [accessed Apr 02 2018].

[brobear]

prehistoric-fauna.com/Agriotherium

Agriotherium
7 reviews
Agriotherium (Agriotherium Wagner, 1837)

Order: Carnivora
Family: Ursidae
Size: 2.5 m in length, 165 cm in height, 600 kg of weight
Time period: the Miocene - Pleistocene (North America, Europe, Africa, and Asia).
Typical representative: Agriotherium africanum Hendey, 1980

Agriotherium is an extinct genus of Ursidae of the Miocene through Pleistocene epochs, endemic to North America, Europe, Africa, and Asia living from ~13.6–2.5 Ma, existing for approximately 11.1 million years. Agriotherium was about 2.7 metres in body length, making it larger than most living bears. Except for the extinct subspecies of modern polar bear Ursus maritimus tyrannus and Arctotherium , Agriotherium was along with the short-faced bear, Arctodus simus the largest member of terrestrial Carnivora. It had dog-like crushing teeth. Its primary diet was carnivorous and secondary was omnivorous possibly classifying this animal as mesocarnivore. With a body mass greater than most large ungulates (horses, bovines, camelids, and rhinoceroses), it is probable that Agrotherium could have preyed on these. 
 

600 kilograms is equal to
1,322.77 pounds (avoirdupois)  
   
165 centimeters is equal to
64.96 inches ... 5 feet 5 inches.

[brobear]

www.wired.com/2012/10/researchers-chew-over-a-prehistoric-bears-diet/

OF ALL THE bears to come and go during the group’s 23 million year old history, none had a bite more powerful than Agriotherium africanum – a ursid as large as today’s grizzly and polar bears that roamed Africa during the latest Miocene and earliest Pliocene epochs. In a new Journal of Zoology paper by C.C. Oldfield, Colin McHenry, and colleagues, virtual models used to run bite tests predicted that the fossil bear could bring its canines down with 4566 Newtons of force – the equivalent of about one thousand pounds of pressure. The question is why this huge extinct bear required such a powerful bite.

For some prehistoric creatures, it isn’t difficult to envision their feeding habits. Tyrannosaurus rex undoubtedly clamped its heavily-fanged jaws on struggling Edmontosaurus and rotting Triceratops, and so the dinosaur’s overwhelming bite strength makes sense given its hypercarnivorous lifestyle. But the connection between skull anatomy, bite force, and diet isn’t always so clear.

The skull of Agriotherium africanum looks like that of a dedicated carnivore. Much like Arctodus – a similarly-proportioned but distantly-related bear from the Pleistocene of North America – Agriotherium had a relatively broad, deep skull well-suited to handling the stresses and strains created by large, struggling prey. Then again, the same suite of features could have just as readily been employed to dismember carcasses or crunch tough plants, and some researchers have argued that Agriotherium, Arctodus, and similar bears were omnivores that often fed on carrion rather than chasing down large prey.

As Oldfield and co-authors point out, the remarkably high bite force Agriotherium brought to bear doesn't allow us to distinguish between the hunting and scavenging alternatives. Having a powerful bite is just as useful to an active predator as to a saprovore. And modern bears only complicate efforts to reconstruct the lifestyle of Agriotherium.

When the researchers investigated the mechanical properties of skulls representing a giant panda, a brown bear, an American black bear, an Asian black bear, and a polar bear, there was no indication that bite force, alone, predicted carnivory. Quite the contrary. The mostly-herbivorous giant panda had the strongest bite force for its size, while the hypercarnivorous polar bear had among the lowest proportional bite force. In fact, Oldfield and collaborators deemed the polar bear as “among the poorest performers” in terms of being able to handle the stresses involved with killing and consuming large prey. Maybe this is because the polar bear eats a great deal of blubber from prey that can’t put up much of a fight on land, the researchers suggest, but the main point is that there is not a simple connection between being a predator and having a strong bite.

[brobear]

( IMO ) Agriotherium was a powerful scavenger and kleptoparasite just like his distant relatives Arctodus and Arctotherium. 
 
600 kilograms is equal to
1,322.77 pounds (avoirdupois)

165 centimeters is equal to
64.96 inches ... 5 feet 5 inches. 
 
Note: If this shoulder height is average, then I would place Agriotherium in the size range of Arctodus simus.  

[brobear]

www.tandfonline.com/doi/abs/10.1080/08912960500476366

The hypothesis that giant short-faced bears of the genera Agriotherium and Arctodus were primarily carnivorous and preyed on large terrestrial mammals is examined. It is argued that the shape and wear pattern of the cheek teeth and the presence of the premasseteric fossa on the mandible in these two ursids suggest a large amount of plant material in their diet. Likewise, the absence of adaptations for either ambush or pursuit predation in their skull and postcranial skeleton suggest that they did not prey on large terrestrial mammals. Further support for this conclusion is provided by a comparison of the dental and skeletal morphology of Agriotherium and Arctodus to that of Hemicyon ursinus, an extinct ursid widely accepted to have been a predaceous carnivore. However, it is also argued that the giant short-faced bears included a large amount of animal material in their diets, which was obtained by scavenging.

[brobear]

link.springer.com/article/10.1007%2Fs10914-012-9218-x

Tooth root surface areas serve as proxies for bite force potentials, and by extension, dietary specialization in extant carnivorans. Here, we investigate the feeding ecology of the extinct large-bodied ursid Agriotherium africanum, by comparing its root surface areas (reconstructed with the aid of computed tomography and three-dimensional image processing) and bite force estimates, with those of extant carnivorans. Results show that in absolute terms, canine and carnassial bite forces, as well as root surface areas were highest in A. africanum. However, when adjusted for skull size, A. africanum’s canine roots were smaller than those of extant solitary predators. With teeth being the limiting factor in the masticatory system, low canine root surface areas suggest that A. africanum would have struggled to bring down large vertebrate prey. Its adjusted carnassial root sizes were found to be smaller than those of extant hard object feeders and the most carnivorous tough object feeders, but larger than those of extant omnivorous ursids and Ursus maritimus. This and the fact that it displayed its highest postcanine root surface areas in the carnassial region (rather than the most distal tooth in the tooth row) suggest that A. africanum consumed more vertebrate tissue than extant omnivorous ursids. With an apparent inability to routinely bring down large prey or to consume mechanically demanding skeletal elements, its focus was most likely on tough tissue, which it acquired by actively scavenging the carcasses of freshly dead/freshly killed animals.
Mechanically less demanding skeletal elements would have been a secondary food source, ingested and processed mainly in association with muscle and connective tissue.

[King Kodiak]

SKULLS OF AGRIOTHERIUM AFRICANUM.





shaggygod.proboards.com/thread/771/agriotherium

[King Kodiak]

AGRIOTHERIUM AFRICANUS SKULL-LATERAL VIEW.

[brobear]

Agriotherium sp. Location: China Age: Late Miocene, 6 MYA (skull replica, 18.5 inches long).  
                                                            

[brobear]

shaggygod.proboards.com/


THE DISTINCTION BETWEEN AGRIOTHERlUM AND INDARCTOS

Indarctos was first separated from Hyaenarctos by Pilgrim in 1913 chiefly by its enlarged talon of M2/. Owing to the absence of veritable association of upper and lower dentitions, in the ensuing 20 years the discussion had been mainly restricted to the characters of the upper dentition. Zdansky's adoption of the differentiation of the two genera was based exactly on the characters of M2/, as proposed by Pilgrim in 1913. Frick, while considering Indarctos one of this three subgenera of the genus Hyaenarctos, dwelt on P4/-M 1 in 1926. Matthew's correct summary of the differences of the two genera in 1929 was based also on P4 -M1. Pilgrim was the first to combine the lower dentition, namely M/1 with the upper ones in his diagnostic characters for the two genera and his viewpoints have been subsequently widely accepted. According to this author, the most important characters, by which Agriotherium differs from Indarctos, with exception of the less important position of the zygomatic arch, are:

1. P1 to P3 are small, single-rooted teeth; one lower premolar is missing.
2. Inner border of the upper molars shorter than the outer border.
3. M2/ without talon.
4. P4/ with antero-posterior diameter greater than that of M1/; parastyle prominent.
5. M/1 relatively short, with talonid much shorter than trigonid, and hypoconid higher
than entoconid.

[King Kodiak]

AGRIOTHERIUM AFRICANUM