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Agriotherium africanum
Topic Started: Jan 8 2012, 07:33 PM (5,153 Views)
Taipan
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Agriotherium africanum

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Temporal range: Late Miocene–Pleistocene

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Superfamily: Arctoidea
Family: Ursidae
Subfamily: Ursinae
Tribe: Ursavini
Genus: Agriotherium
Species: Agriotherium africanum

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.

Taxonomy
Agriotherium was named by Wagner (1837). It was assigned to Agriotheriini by Chorn and Hoffman (1978); to Hemicyoninae by Qiu et al. (1991); to Ursavini by Hunt (1998); to Ursidae by Wagner (1837), Carroll (1988) and Salesa et al. (2006), and Ursinae by Krause et al. 2008.

Morphology
Agriotherium was about 2.7 metres (9 ft) 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 terrestial 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.

Body mass
Two specimens were examined by Legendre and Roth for body mass.
Specimen 1: 79.3 kg (170 lb)
Specimen 2: 652.6 kg (1,400 lb)
Edited by Taipan, Oct 19 2017, 04:28 PM.
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Ancient bear had the strongest bite

By Ella Davies
Reporter, BBC Nature

Posted Image
Scanning the skull revealed meaty secrets

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.

The findings were published in the Journal of Zoology.

Dr Stephen Wroe from the University of Newcastle, 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.

Posted Image
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.

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.

http://www.bbc.co.uk/nature/15559929
Edited by Taipan, Oct 19 2017, 04:19 PM.
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italiano
 
Were their canines as large as the reconstruction makes them appear?


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prehistoriccat
 
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Taipan
Jan 12 2012, 10:18 PM
Ancient bear had the strongest bite

By Ella Davies
Reporter, BBC Nature

Posted Image
Scanning the skull revealed meaty secrets

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.

The findings were published in the Journal of Zoology.

Dr Stephen Wroe from the University of Newcastle, 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.

Posted Image
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.

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.

http://www.bbc.co.uk/nature/15559929



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.

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http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.2011.00862.x/full
Edited by Taipan, Oct 19 2017, 04:23 PM.
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