Saber-toothed cats strong-armed prey

Forelimbs were especially thick for their length

A saber-toothed cat’s pounce may have been as bad as its bite. These extinct animals had exceptionally strong forelimbs that probably held a victim still while razorlike teeth ripped out its throat, a new study shows.

Most carnivorous cats suffocate their victims with a long, crushing bite to the throat or nose. This wouldn’t have worked for sabertooths because their formidable twin canines were surprisingly fragile. The teeth were oval-shaped when cross-sectioned – like blades are – rather than round like other cats’. That made saber-shaped teeth good for slicing through flesh, but easily snapped by writhing prey.

Now paleontologists have an explanation for how one saber-toothed cat, Smilodon fatalis, avoided breaking those delicate pearly whites. A fossil analysis shows that the animal’s humerus, the bone between the shoulder and elbow, was stronger than in any other cat, living or extinct.

Though they had long thought the sabertooth’s forelimb bones seemed unusually thick, scientists had never measured the inner strength of the bones.

“This is the first study to look at the internal bone to see how strong limbs are and how they resist forces,” says vertebrate paleontologist Julie Meachen-Samuels, who conducted the research at the University of California, Los Angeles and now works at the National Evolutionary Synthesis Center in Durham, N.C.

Meachen-Samuels compared leg bones of 29 wild carnivorous cat species with those of S. fatalis. Digital X-rays revealed details of the bones’ insides — including the cortex, the hard outer bone that surrounds the inner marrow.

Turns out the sabertooth’s forelimb cortex was thicker relative to bone length than all the other cats. This would have made the bones more resistant to bending and twisting, Meachen-Samuels and Blaire Van Valkenburgh of UCLA report July 2 in PLoS ONE.

“It’s very strong evidence that the limbs were used in certain ways to grapple with prey so it could make a quick bite,” says Christopher Shaw, paleontologist at the George C. Page Museum in Los Angeles, who was not involved in the research.

Ongoing work looking at several types of saber-toothed cats shows that the longer the teeth, the thicker the forelimbs, Meachen-Samuels says. She interprets this to mean that long teeth and strong bones coevolved, because the cats needed the arm strength to protect long teeth.

The strong forelimb–sharp tooth combination was perfect for pouncing on prey, pinning it down and quickly gouging its throat. Sabertooths were thus probably good at hunting large animals like bison and camels. During the last ice age, many of these large animals died out, so saber-toothed cats had less to eat.

Sabertooths “had such a specific mode of prey killing that they were probably limited in the range of prey they could take,” Meachen-Samuels says. Such a specific hunting niche probably led to their extinction, she adds.

The study is important because it gives researchers an idea about what life was like for carnivorous creatures at the time, says vertebrate paleontologist Virginia Naples of Northern Illinois University in DeKalb. “Using that information could give us a model to look at changes in predator and prey communities today.”

STRONG-ARMED Saber-toothed cats (skeleton of Smilodon fatalis shown) may have pinned their prey with strong forelimbs. Julie Meachen-Samuels

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