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DANGEROUS GRINThe massive canine teeth and incisors of Xenosmilus hodsonae (skull at left) produced evenly spaced perforations (dental imprint at top right) that would have made it easy to rip out a fist-sized hunk of flesh from its prey. The dental imprint at lower right depicts the wounds that might have been inflicted by the dirk-toothed Smilodon fatalis.Martin et al.

CLEVELAND — Analyses of fossils reveal that a third, newly recognized type of saber-toothed cat — one that killed by biting large chunks of flesh from its victim instead of biting its neck and slashing the major blood vessels there — roamed the Americas about a million years ago.

All modern-day cats, from tabbies to tigers, have cone-shaped incisors and canine teeth at the front of their jaws, and most of these felines are relatively lithe. But the extinct saber-toothed cats were a different breed altogether.

Previously, scientists split those cats into two morphotypes, or combinations of body type and tooth shape, says Virginia Naples, a vertebrate paleontologist at Northern Illinois University in DeKalb. One group, the dirk-toothed cats, had stout bodies, short legs, and long, narrow, finely serrated canine teeth in their upper jaws. Felines in the other group, the scimitar-toothed cats, were slimmer than the dirk-toothed cats, had longer legs and had canine teeth that also were serrated but relatively shorter and broader than those of dirk-toothed cats. 

At the annual meeting of the Society of Vertebrate Paleontology on October 18, Naples and her colleagues proposed a new, third type of saber-toothed cat: A stoutly built feline whose full array of teeth — not just the canines — were serrated. Because analyses of fossils from one of these felines suggest that the teeth on its upper jaw meshed with those on its lower jaw to produce a clean, nearly continuous cut, the researchers suggest calling the new morphotype “cookie-cutter cats.”

The fossils that inspired the cookie-cutter moniker belong to Xenosmilus hodsonae, a creature that lived about 1 million years ago. Those remains were found in what is now northernmost South America and the southeastern United States, and the cat is presumed to have lived in areas in between as well. The creature, which was first described in 2000, is about the same size and shape as a modern-day giant panda, says Naples. Xenosmilus’ bones were larger than those of other saber-toothed cats, and analyses suggest that the cookie-cutter cats’ forelimbs had a much larger range of motion, enabling them to more effectively grab and hold prey. “This was the sumo wrestler of big cats,” Naples notes.

Atop Xenosmilus’ robust, flat-footed frame sat a skull with a devastating set of teeth. As with other saber-toothed cats, the canine teeth were long, robust and serrated. Unlike its kin, however, Xenosmilus’ incisors, which span the front of the upper jaw, were large and evenly spaced, says Larry Martin, a vertebrate paleontologist at the University of Kansas in Lawrence and a coauthor of the new report. Also, because Xenosmilus’ incisors vary in length, the full force of the creature’s bite would have been concentrated on only two teeth at a time — an arrangement that would have made it easier to bite into any tough-hided prey, he notes.

While other saber-toothed cats probably dispatched their prey by biting its neck and severing the major blood vessels there, cookie-cutter cats probably just hung on and bit out a fist-sized chunk of flesh, causing massive blood loss that would have sent victims into shock in about 10 seconds or so, says Martin. That technique, plus Xenosmilus’ stocky stature, hints that cookie-cutter cats ambushed their victims, rather than chasing prey long distances

“This cat could easily hold and bring down whatever it grabbed,” says Christopher Shaw, a vertebrate paleontologist at the Natural History Museum of Los Angeles County. That, along with the creature’s ability to cleanly rip out large hunks of flesh, would have been an effective combination against any prey, he notes.

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