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Saber-tooth cats grew their fangs faster than human fingernails

Saber-tooth cats, the bane of early humans (and pretty much every creature that co-existed with them), roamed the Earth for 42 million years before going extinct at the end of the ice age. Now, a new study has found that their trademark teeth may have evolved later in their evolutionary stage, but when they grew, they grew fast.

Skeleton of Smilodon (Smilodon fatalis). Exhibit in the National Museum of Nature and Science, Tokyo, Japan.

The saber-tooth cats were found worldwide from the Eocene epoch (42 million years ago) to about 11,000 years ago – the earliest human cultures might have actually seen them in action. Despite the “cat” in their name, these animals are not closely related to modern cats, belonging to a different evolutionary tree. The most well known saber-tooth cat is the Smilodon, who emerged 2.5 million years ago and weighed up to 440 kg.

With their incredibly long teeth, they have fascinated us for centuries, and researchers have been striving to understand how, and why these teeth evolved. Now, they are one step closer, after learning that these teeth grew incredibly fast.

“For predators such as big cats, an important determinant of an individual’s full hunting ability is the time required to grow their weapons—their teeth,” explains Z. Jack Tseng, who is a National Science Foundation and Frick Postdoctoral Fellow in the American Museum of Natural History’s Division of Paleontology. The study co-author goes on to say, “This is especially crucial for understanding sabertoothed predators such as [the species] Smilodon.”

The sabers they developed were a remarkable adaptation, and Tseng wanted to see just how long it took for a specimen to grow its teeth. So he and his team conducted chemical analysis on fossils and meticulously analyzed the chemical composition and structure of the sabers. They came up with a stunning results: the saber teeth grew by 6 mm per month – twice as fast as human fingernails!

“Timing of development is critical for many aspects of vertebrate ecology and evolution,” reports New York State Museum Pleistocene vertebrate paleontology curator Robert Feranec and study co-author. “Changes in the timing of life-history events can have major effects on an organism’s adult features and final appearance. For extinct species, we can usually only determine the relative sequence of development events. This technique will permit the determination of absolute developmental age not only for Smilodon, but other extinct species.”

Reconstruction o saber-tooth cat by Marcus Dublin.

So even though they had huge fangs, much longer than those of today’s lions, they didn’t take so much time to grow them. However, when it comes to biting, tooth size isn’t everything. Using computer models, scientists estimated the bite strength that saber cats use and found that it was actually weaker than their gripping force – so it seems likely that they killed their prey by gripping, not biting. However, the long canines were extremely efficient at biting the neck.

Saber tooth cat mostly hunted large, slow prey. The Smilodon for example was an apex predator and primarily hunted large mammals like bison, camels, horses and even mammoths. They were experts at ambushing and used their large mass to disrupt the balance of their prey, making it vulnerable. They would likely still be alive today, if most of their prey hadn’t gone extinct.

The study is published in the journal Proceedings of the National Academy of Sciences.


Illustration of a cougar-like nimravid. (c) thorthebarbarian.com

Saber-tooth-like cats ambushed and killed their own kind

Illustration of a cougar-like nimravid. (c) thorthebarbarian.com

Illustration of a cougar-like nimravid. (c) thorthebarbarian.com

Looking close at suspicious marks and cuts present in the skulls of saber-tooth like cats which roamed North America millions of years ago, paleontologist Clint Boyd of the South Dakota School of Mines and Technology found what he believes are clear signs that the animals used to ambush and kill their own kind.

Fierce predators native to North American that lived some 32-34 million years ago, Nimravids are a group of extinct saber-toothed felids also known as false saber-tooths. In 1936 a peculiar skull belonging to such a cat exhibited bite marks made by the same animal’s long canine teeth. Not too much attention was given to the fact, but in 2010 a girl hiking through the Badlands National Park found a nimravid skull which also bore nimravid bite marks. Boyd, who was working at the park at that time, took interest in the find and decided to examine other skulls for collections all over the country as well.

The skull found in 2010. Red arrows show bite marks. (c) MINDY HOUSEHOLDE

The skull found in 2010. Red arrows show bite marks. (c) MINDY HOUSEHOLDE

“Some of the best specimens with bite marks were right in front of people,” he said. “Older specimens did not show the bite marks until they were cleaned up.” Some actually still had dirt in the holes made by the bite marks and others had had the holes repaired by curators unaware of their significance.

“What we found is that these bite marks are a lot more common than previously thought.”

With so many clear signs of nimravids murdered by their own kind there was no doubt that the animals were competing with each other in a highly aggressive manner. Skull analysis revealed another import insight too: all attacks thus far described were made by ambush, from behind. Kills were made either by inserting a fang into an eye socket or puncturing the skull.

Not an accurate depiction of nimravid rivalty. Most likely, the beasts would perform sneak attacks on each other.

Not an accurate depiction of nimravid rivalry. Most likely, the beasts would perform sneak attacks from behind.

A nimravid’s canine teeth were its biggest and most valuable asset, as well as its most vulnerable. If they broke, the cats would have surely been doomed, killed either by starvation or other predators. That’s why there has been no attested nimravid bite mark on its prey’s skulls. Instead the cats   used the canines to tear out the soft tissues in the throats of their prey and would have been careful not to bang them on bone, which might have damaged their most important hunting weapon.

Fatal nimravid bite marks are found on a surprising 10 percent of nimravid skulls in three species of nimravids over a range of four million years. Why? Because it’s worth the risk when dealing with competitors.  They were still careful not to damage their canines, though, since most attacks are directed towards the eye socket. Museums often present illustrated depictions of rivaling nimravids facing each other in open plain. This likely needs revision, instead a more accurate painting would depict an ambush scene.

“It’s very hard to get behavior from fossils,” said Kurt Spearing, a researcher at Morningside College in Sioux City, Iowa, who works on fossil cats and their close relatives and was not directly involved in Boyd’s work.

But in this case, he agrees that the behavior of nimravids is remarkably clear: “These guys were incredibly aggressive towards each other.”

via Discovery