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|Tweet Topic Started: Jan 8 2012, 05:02 PM (17,266 Views)|
|Taipan||Jan 8 2012, 05:02 PM Post #1|
Temporal range: Late Pleistocene, 1.0 –.01 Ma
Species: Smilodon populator
Smilodon populator was one of the biggest cats of all time. It was the largest of the saber-tooths, and lived in South America during the Late Pleistocene: about two million to 10,000 years ago. It originally evolved from ancestors that invaded the continent North America about three million years ago.
With an estimated weight of 200 to 300 kg and exceptional large specimens probably up to and over 400 kg, it was among the heaviest felids to have ever existed. It was much larger than its relatives, S. fatalis and S. gracilis, possessing a massive chest and front legs, and is the largest known variety of saber-toothed cat. It was more than 1.40 m (55 in) high at the shoulder, 2.6 m (100 in) long on average and had a 30 cm (12 in) tail. With an estimated weight of 360 to 470 kg (790 to 1,000 lb), it was among the heaviest known felids. Its upper canines reached 30 cm (12 in) and protruded up to 17 cm (6.7 in) out of the upper jaw. Genetic evidence suggests Smilodon populator and other members of the genus diverged from the main lineage of modern cats (subfamily Felinae) around 14-18 million years ago.
S. populator, had higher shoulders than hips and a back that sloped downwards, superficially recalling the shape of a hyena, in contrast to the level-backed appearance of S. fatalis, which was more like that of modern cats. However, while its front limbs were relatively long, their proportions were extremely robust and the forearm was shorter relative to the upper arm bone than in modern big cats, and proportionally even shorter than in S. fatalis. This indicates these front limbs were designed for power rather than fast running, and that S. populator would have had immense strength in its forequarters.
Despite being more powerfully built than other large cats, Smilodon actually had a weaker bite. Modern big cats have more pronounced zygomatic arches, while Smilodon had smaller zygomatic arches which restricted the thickness and therefore power of the temporalis muscles, and thus reduced Smilodon’s bite force. Analysis of its narrow jaws indicates it could produce a bite only a third as strong as that of a lion. There seems to a be a general rule that the saber-toothed cats with the largest canines had proportionally weaker bites. However, analyses of canine bending strength (the ability of the canine teeth to resist bending forces without breaking) and bite forces indicate the saber-toothed cats' teeth were stronger relative to the bite force than those of modern "big cats". In addition, Smilodon could open its jaws 120 degrees, whereas the lion's gape is limited to 60 degrees.
Smilodon populator is also known from the famous cave site of Ultima Esperanza, with well-preserved remains retaining endogenous DNA.
The saber-tooths were specialist predators that fed on large-bodied prey. It has been an enduring mystery as to how Smilodon used its huge teeth when hunting. Some scientists think that it would slash at prey, causing huge wounds. A more likely theory suggests that the sabers evolved for a neck death-bite. In this scenario, Smilodon would hold down its struggling prey with its huge arms while it gripped the animal's throat with its mouth, the sabers slashing through arteries and crushing the windpipe. Prey quickly would be killed in this fashion, making it less likely the Smilodon would be injured.
The social pattern of this cat is unknown. Some fossils show healed injuries or diseases that would have crippled the animal. Some palaeontologists see this as evidence that saber-toothed cats were social animals, living and hunting in packs that provided food for old and sick members. Living in groups would also help with having to compete with lions and wolves. The canine teeth and body size of Smilodon were about the same in both male and female cats. This indicates that Smilodon may not have lived in male-dominated groups (and that the teeth may not have been used for attracting mates as it has been suggested). However, it still could have hunted cooperatively.
The extinction of most large-bodied herbivores 10,000 years ago meant that Smilodon had lost all of its favorite prey. Unable to compete with small-prey specialists like the cougar, the saber-tooths became extinct about 10,000 years ago and left no descendents.
Edited by Taipan, Mar 12 2012, 01:32 PM.
|Taipan||Jan 10 2012, 08:08 PM Post #2|
[quote author=taipan board=zoological thread=1194 post=17321 time=1182171451
Smilodon Populator was a lion-sized cat, extremely strong and powerful (particularly in the chest and forelimbs; an adaptation designed for its large-sized prey) and armed with 7-inch long sabre-teeth. Some debate has taken place on exactly how these were used. Some people suggested they were for climbing trees, others for punching through the skull of the prey, and still others claimed they were used to stab into the throats of the herbivores. Calculations indicated that the teeth were not strong enough for the first two applications - they would have shattered when they impacted bone, and this also ruled out the neck-bite technique used by the extant small cats. The 'stab' theory didn't hold water, either, as the cat's neck and jaw muscles were not powerful enough to propel the teeth through the thick hide.
The rear edges of the sabres are serrated, and this indicated that the cat used its teeth as blades to cut through the hide and tissues of its prey, rather than as daggers. The smaller lower canines were driven into the hide of the prey animal's neck or belly, to provide purchase for a downward strike by the sabres as the cat closed its jaws (this action is termed a 'shearing bite'). Evidence for this is the fact that Smilodon's jaws could open 25 degrees wider than those of the modern cats, allowing it to achieve a similar clearance between the tips of upper and lower canines as modern cats. By using this technique, the teeth would never encounter bone. The prey animal would then die of blood-loss. The problem with this explanation is that any torsional loads on the teeth, for example the movements of a standing prey animal, would break them. So Smilodon could not have brought down its prey using its teeth alone. It is probable that hunting took place in groups, and the upper-body strength of the cats was used to capture and restrain the prey before the fatal bite was applied to the throat.
One of the advantages of the sabre was that prey carcasses could be sliced up and carried back to the den to feed young, eliminating the need for the young cubs to accompany their mother. There is some evidence that Smilodon may have lived in a pride social structure. The Rancho La Brea asphalt pit fossils indicate that for every trapped herbivore, several Smilodon are present, leaving pack-hunting a likely scenario. In addition, the Sabres' teeth were so large that they did not fully develop until the animal was quite mature, so the level of maternal care required over a long period would have been high. This would suggest social groupings were the norm.
Smilodon Populator lived in the east of South America, and other (slightly smaller) species of Smilodon lived in North America. Its body was in some ways different from the lion; relatively, it had shorter hind- and longer fore-limbs, giving it a stance more like that of a hyaena. This would have allowed it to run more easily, and so chase prey over long distances. In contrast, the modern lion will not usually sustain a chase beyond a few hundred metres.
The Sabre-tooth design was predominant among the cats until 5-6 Ma, when climate change resulted in the forests which had covered the continents giving way to open savannah and plains. This in turn led to the proliferation of smaller herbivores, such as antelope and gazelle, which could outrun the Sabre-toothed cats easily. It was at this point that the Pantherines evolved, from which descended many of the larger cats of today, with smaller teeth and other adaptations to the new prey species.
The Sabre toothed cats were still able to survive, as the mega-herbivores were still in existence, but around 35,000 years ago further climate change led to colder weather. This saw the demise of the mega herbivores, and so the sabre-toothed cats. The evolution of hominids, who hunted with weapons, and competition from pantherine species such as the lion (which evolved only 600,000 years ago) lead to their final downfall.
|Taipan||Jan 10 2012, 08:08 PM Post #3|
Saber-toothed Cats Wrestled Prey with Powerful Arms
By Charles Q. Choi, LiveScience Contributor
posted: 02 July 2010 04:59 pm ET
Saber-toothed cats might be most famous for their oversized fangs, but scientists now find the feisty felines had another exceptional feature — powerful arms stronger than those of any cat alive today.
Commonly known as the "saber-toothed tiger," the extinct cat Smilodon fatalis roamed the Americas until roughly 10,000 years ago, preying on "megafauna" — large animals such as mammoths, bison, camels and mastodons. Their specialization on such giant creatures might have doomed these hunters when their Ice Age prey died off.
The most recognizable features of the saber-toothed cat — giant, dagger-like canines — were also perhaps its most puzzling. The fangs would have been excellent at inflicting deadly slashing bites to its prey's throat, but their size and shape would also have made them highly vulnerable to fracturing compared with modern cats. That led researchers to wonder how the fangs developed in the first place.
"Cats living today have canines that are round in cross-section, so they can withstand forces in all directions," said researcher Julie Meachen-Samuels, a paleontologist at the National Evolutionary Synthesis Center in Durham, N.C. "If the prey is struggling it doesn't matter which way it's pulling — their teeth are unlikely to break."
In contrast, the long canines of saber-toothed cats were oval in cross-section, or thinner side-to-side, making them relatively fragile. This suggested that saber-toothed cats must have killed prey differently from other cats. In fact, research published in 2007 suggested Smilodon had a wimpy bite.
That's where the powerful arms come in. These predators might have pinned victims down with their heavily muscled forelimbs to protect their teeth from fracturing as they bit struggling prey, Meachen-Samuels said.
Feline wrestling match
In an arm-wrestling match of sorts, the researchers compared saber-tooth arms with those of other cats. To do so, they X-rayed the arm and leg bones of fossils recovered from the La Brea Tar Pits in Los Angeles. They also analyzed the limb bones of 28 cat species living today — ranging in size from the 6-pound (2.7-kilogram) margay to the 600-pound (272-kg) tiger — as well as the extinct American lion, the largest cat with conical teeth that ever lived. These measurements helped the researchers estimate bone length, rigidity and strength for each species.
Species with longer limbs generally had stronger bones. However, while saber-tooth leg bones fell within the normal range, their arm bones were exceptionally thick for their length. Not only that, their arms also had thicker cortical bone — the dense outer layer that makes bones strong and stiff.
"When I looked at Smilodon, I knew they were thicker on the outside than other cats, but I was really shocked at how much thicker they were on the inside as well," Meachen-Samuels told LiveScience.
The thicker cortical bone seen with the saber-toothed cats makes sense if the arms were under greater stress than normally expected for cats their size, Meachen-Samuels explained. Just as lifting weights improves bone density over time, so too may the repeated strain of grappling with prey have resulted in thicker and stronger arm bones in saber-toothed cats.
"As muscles pull on bones, bones respond by getting stronger," Meachen-Samuels said. "Because saber-toothed cats had thicker arm bones, we think they must have used their forelimbs more than other cats did."
The researchers would like to next look at other saber-toothed cats, as well as other saber-toothed predators that once existed. "There aren't a lot of arm bones to X-ray for other saber-toothed predators, but it'd be interesting to see if there were convergent processes with their arms as well," Meachen-Samuels said.
Meachen-Samuels and her colleague Blaire Van Valkenburgh detailed their findings online July 2 in PLoS ONE.
|Taipan||Jan 10 2012, 08:09 PM Post #4|
How a Smilodon sabretooth cat closed its gaping mouth
By Victoria Gill
Science and nature reporter, BBC News
Page last updated at 12:14 GMT, Friday, 25 February 2011
The sabretoothed cats killed prey with a deep stabbing bite to the throat
The mystery of how prehistoric sabretoothed cats coped with their oversized teeth has been solved in part by a new analysis of the cats' jaws.
To impale prey with these impressive weapons, the famous sabretoothed cats must have opened their mouths wider than any modern big cat, but it was unclear if their jaw muscles were strong enough to do it.
Now the new analysis reveals that the cats' jaw muscles evolved into a specialised pattern, which allowed them to open their mouths so wide.
Details are reported in the Zoological Journal of the Linnean Society.
Per Christiansen, from Aalborg University in Denmark, led the study. He took a novel approach to studying the extinct predators by creating a complex model of how their jaws moved.
Beautifully preserved skeletons of the most recently extinct sabretoothed cat, Smilodon, have been uncovered in tar pits in the US, offering the researcher plenty of fossilised remains to work with.
These fearsome-looking cats - the biggest of which would have hunted very large prey, including buffaloes, horses and extinct giant ground sloths - had a relatively weak bite force compared to their modern feline relatives, previous studies have revealed.
But this is not surprising, according to Dr Christiansen. He has found the cats must have had remarkable jaw muscles to close their mouths with any force at all.
"Smilodon could open its mouth wider than any modern cat," explained Dr Christiansen, "because if you have big teeth, you have to open your mouth at a very high angle to get anything in your mouth."
Smilodon (right) was able to open its mouth wider than any modern cat
Over the years, scientists have debated what the now extinct cats used their enormous teeth for, with some even suggesting the teeth were ornaments that males used to attract mates.
But the consensus is now that the teeth, which measured up to 20cm, delivered final, fatal stabs to already subdued prey.
Bulkier and more muscular than most modern cats, Smilodon would have brought large animals down with its forelimbs.
"They pounced on their prey, wrestled it to the ground and twisted the neck with massive forelimbs," explained Dr Christiansen.
"They then delivered a quick, powerful and deep stabbing bite to the throat or upper neck. But, there were no minute-long massive asphyxiating throat-clamps like those used by modern big cats when they suffocate prey. The sabrecats simply didn't have the jaw muscles for that."
Opening their mouths sufficiently wide to kill and consume their hard-earned meal would have stretched and significantly weakened their jaw muscles.
Dr Christiansen created a model of the cats' jaws, carefully calculating how they must have moved, to work out how Smilodon evolved to compensate for this weakness.
His model revealed how the cats' jaw muscles were aligned to pull its jaws closed, very directly and efficiently.
But Smilodon would also have done something that every cat-owner can see a relic of in their own pet.
"When you put a piece of food on the floor for your cat, you'll see it bobs its head forward as it eats it," he explained.
"And we know that [Smilodon] probably closed its jaws by twisting its head downward and throwing its head forward.
"Its neck was longer than that of modern cats and its neck muscles would have been stronger."
The study also looked back at the earliest and most primitive sabretoothed animals.
"Smilodon was outrageous in terms of its anatomy," said Dr Christiansen.
"It was the most [highly evolved and therefore] different from modern cats, so to understand this animal from a biological sense, you need to study more primitive animals to work out why they have become that way through evolution."
Smilodon would have brought down prey with its powerful forelimbs
He examined hundreds of skulls, drawing an evolutionary map showing why sabretooths evolved such different jaw anatomy from modern cats.
"Killing ecology", he explained, was the driving factor - the evolutionary pressure to kill prey with a deep and efficient stab to the throat.
"The cat species became gradually more and more specialised, culminating with monsters such as Smilodon," said Dr Christiansen.
As sabretooths evolved longer canine teeth, their jaw muscles actually grew smaller, but the fibres became more vertically orientated and thus probably more efficient in closing the jaw.
Dr Christiansen explained: "At the same time, changes in the way the muscle fibres inserted on the lower jaw meant that the animals could stretch their muscles more - the fibres became re-orientated so as to allow a higher gape, necessary for gaping with huge fangs."
But their impressive appearance might well have been key to their demise; the sabre-toothed cats were dependent on large, relatively slow-moving prey.
"They had very powerful but heavy bodies and rather short, extremely powerful legs," said Dr Christiansen, "so they probably weren't very fast, and certainly nowhere near as fast and agile as leopard and tigers."
|Taipan||Jan 10 2012, 08:12 PM Post #5|
|Taipan||Jan 10 2012, 08:13 PM Post #6|
Edited by Taipan, Jan 22 2012, 08:42 PM.
|Red Dog||Jan 11 2012, 07:04 AM Post #7|
Below is a relevant graph and analysis from Anyonge's referenced study above. This graph illustrates locomotor adaptions and animals toward the right are more adapted for cursoriality and animals toward the left are more adapted for grappling. Coursers include wolves, hyenas, and cheetahs. Ambushers are big cats, and ambulators are bears.
Here is a discussion. Function 1 (the horizontal axis) is the more important of the two functions. The weights of the variables impacting this are listed in the table below (ignore the signs, the absolute value of the variables are how much they impact the results).
Overall, Smilodon Fatalis appears more adapted for grappling than Panthera Atrox. Smilodon Populator was more specialized than Smilodon Fatlis and would likely score even higher.
Edited by Red Dog, Jan 11 2012, 07:04 AM.
|Red Dog||Jan 11 2012, 07:05 AM Post #8|
Smilodon fatalis killed conspecifics with bites to the skull or ribs.
Smilodon may have used a careful canine shear bite to the throat with huge prey, such as the ice-age bison (larger than the modern species), but apparently it could bite the skull ot ribs of other smilodons.
[quote author=reddhole board=interspecific thread=3578 post=38347 time=1221153518]IMHO, the fragility of Smilodon's canine teeth is overstated. While it is true that Smildon killed ice-age megafauna (i.e. ~ 3,000 lb. Pleistociene bison) with a careful and precise canine-shear bite, similar-sized predators were (at least sometimes) killed with bites to the skulls or ribs. The following extract is from this study:
Source: Per Christiansen, "Comparitive Bite Force and Canine Bending Strength in Feline and Sabertooth Felids: Implications for Predator Ecology", Zoological Journal of the Linnean Society, 151: 2, 2007, P 423-437
Note the following statement:
Smilodon may generally have avoided biting directly into bone during hunting, but direct evidence exists of it being an aggressive predator with a bite powerful enough to drive canines through bone, such as another Smilodon skull with a deep bite wound, or a rib cage with a canine tip still embedded in it.
This is also supported by this study's measurements of the sabertooth's canine bending strength. S AP and S LM are different measurement of canine strength. Smilodon fatalis's canines were similar (and in some respects greater) in strength as lions, tigers and jaguars, but the sabertooth cat was also heavier.
IMHO, Smilodon could have also dispatched a similar sized carnivore with a canine shear bite to the throat as well. All cats have to be somewhat careful when they bite, and must have decent control over their adversary before making a killing bite. The extra control a Smilodon would require could easily be met by its vastly superior strength.
|Red Dog||Jan 11 2012, 07:08 AM Post #9|
Source: Prevosti, F.J. and Vizcaíno, S.F. 2006. Paleoecology of the large carnivore guild from the late Pleistocene of Argentina.
Acta Palaeontologica Polonica 51 (3): 407–422.
The size and morphology of Smilodon populator indicate that
it preyed habitually on middle−sized mammals such as large
armadillos, equids, small glyptodonts (e.g., Sclerocalyptus
migoyanus), and large camelids, but it would also be able to
hunt megamammals weighing approximately 1000 to 2000
kg, as well as juveniles of the larger species (i.e., Megatherium
americanum Cuvier, 1796).
|Megafelis Fatalis||Jan 12 2012, 04:04 AM Post #10|
|Megafelis Fatalis||Jan 12 2012, 04:29 AM Post #11|
Edited by Taipan, Jan 22 2012, 08:39 PM.
|Megafelis Fatalis||Jan 12 2012, 04:48 AM Post #12|
|Megafelis Fatalis||Jan 14 2012, 08:00 PM Post #13|
S.populator and S.fatalis
Smilodon Populator's calws compared to modern big cats
|Megafelis Fatalis||Jan 14 2012, 09:30 PM Post #14|
Edited by Megafelis Fatalis, Jan 14 2012, 09:30 PM.
|populator135||Jan 19 2012, 08:57 AM Post #15|
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