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Prehistoric mammals would not have tampered with this huge otter

The wolf-size otter lived in a shallow swamp surrounded by dense vegetation.

(Mauricio Antón)

Six million years ago, the shallow marshes of what is now the south of China, are dominated by large, 110-lb. (50 kilos) otters that are now extinct.

And now, researchers have found that these large otters had more than the size of their hand. It appears, that this animal had a powerful bite, six times stronger than expected from the size alone and strong enough to crush large mollusk shells or the bones of birds and small mammals, the researchers noted in a new study.

“None of the modern otters are top predators,” said Jack Tseng, the lead researcher of the study and a functional anatomist at the University at Buffalo. “They don’t attack large prey, because physically, they are not so great. We think this fossil otter was like the beer of the environment, one of the top predators,” he told Live Science. [See photos of the fearsome wolf-size otter]

Fossil fragments of the otter, Siamogale melilutra, were discovered a few years ago, but it was only recently that Tseng and his colleagues scanned and ran computational models in the digitally reconstructed skull. The objective: to find out how this wolf-size otter lived.

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According to Tseng, that is one of the two big questions that paleontologists try to answer: “What is it?” and “What is life?” (Although Tseng often goes into the field to search for new fossils, he was not involved in the expedition that discovered S. melilutra.)

To find out what the power of the otter’s jaw, Tseng, the team ran computational simulations to see how the bite would strain his jaws. They did the same for modern otters, and found that smaller otters had stiffer and therefore more powerful jaws, and larger otters had more flexible jaws. On the basis of these findings, they calculated that the old otter was a abnormal powerhouse, with a jaw strength that is six times more than what would be estimated on the basis of the animal’s body size.

“Then we saw other animals, we saw that the living species still followed the trend,” said Tseng, who extended his models to include information from other predators such as bears and wolves. “So, in this case, the sea otter was.”

Only one other animal broke the link between body size and jaw stiffness: another extinct predator called Kolponomos newportensis, a wild bear, who lived in the Pacific Northwest 20 million years ago. Although the two animals were separated by the Pacific Ocean, the habitats of both predators were abundant with hard-shelled molluscs, Tseng explained. “That is one line of evidence points to this fossil otter a large consumer of molluscs with jaws the size and strength,” he said.

But Tseng models can not definitively explain how the prehistoric otter lived. On the contrary, they offer a number of possibilities of what it would have been able to do. For example, Tseng said, fossils of the animal show that the claws were strong enough to break open mollusks, but that does not mean that it is not also hunt smaller mammals and fish. Because the fossil was not found with prey in the animal in the mouth, there is no direct evidence that indicates what the creature ate.

To find out exactly where the petrified otter fit in the food web, researchers would need to perform a chemical analysis of otter tooth enamel. That analysis could show whether it was a top predator or a predator somewhere in the middle of the food web, Tseng said. That analysis would involve the grinding of the teeth down to a fine powder, and the fossil is so rare that researchers are not willing to do that.

“We don’t want to take the risk,” Tseng said.

The researchers detailed their findings today (Nov. 9) in the journal Scientific Reports.

Original article on Live Science.

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