Close your eyes and imagine yourself face to face with a saber-toothed cat. You will most likely see in your frightened mind the long, curved upper canines – especially eerie because those dagger-like teeth remained in plain sight, even when the cat closed its mouth.
What appears in your imagination may be incorrect, at least for a species of saber-toothed cat that was one of the most widespread in Earth’s ancient history. In a study published last month in the journal Quaternary Science Reviews, a team of researchers claim that many artistic reconstructions of Homotherium latidens are flawed. Depictions of cats with sharp teeth at hand need revision, as the defining characteristic of the animal was a concealed weapon until the cat was ready to strike or open its mouth.
Homotherium latidens was “the most powerful saber-toothed cat from the Pleistocene of the Old World,” said Mauricio Antón, an artist paleontologist, expert on saber-toothed cats and one of the study’s authors. According to the fossil record, Homotherium first appeared about four million years ago, in the Pliocene. The species ranged from the southernmost tip of Africa, through Eurasia and South America. A Friesenhahn Cave fossil site in Texas suggested that groups of homotheriums may have hunted cooperatively to bring down mammoths. The species became extinct 10,000 years ago.
The cat was the size of a lion, weighed up to 550 pounds, and had long, serrated, scimitar-like upper canines. In an article that Mr. Antón wrote in 2009, he concluded: “The tips of the sabers of Homotherium would have been visible in life, protruding beyond the lips”, even when the cat was at rest. In other words, Homotherium fits the stereotypical profile of the saber-toothed cat.
But more recently, Antón has begun to wonder if he and other paleontology researchers were wrong about the cat’s lethal dentition.
For decades, almost everything scientists knew about saber-toothed cats came from fossils and dissections of modern big cats. “When you dissect a dead fat cat, the lips are in a special position because the muscles that control the lips are relaxed,” Antón said. “That’s where our data came from.”
Then in 2016, while watching a film he had made about a magnificent male lion gaping in the Okavango Delta, Mr. Antón noticed something he had never seen before: “The lip inferior contracted when the mouth closed, and before complete closure it enveloped the tip of the canine. I was like, ‘Do I really see this?’ It was a Eureka moment.
To understand the implications of his observation, Antón and a team of scientists studied living big cats in great detail. They examined the fossil dissections with what Mr Antón described as “new eyes”. And they did a 3D CT scan of an intact three-million-year-old fossil of a Homotherium latidens that had been excavated in Perrier, France.
Gema Siliceo, postdoctoral researcher at Comenius University in Slovakia and co-author of the study, said the combination of these techniques provides “a huge amount of information that we can use to infer the life appearance of an extinct felid”.
Their studies confirmed that there was simply no room for the lower lip and soft tissue between the upper canine of Homotherium and the gum. But there was room for the canines to be hidden against the closed part of the lower mandible or jaw.
Regardless of their aesthetics, saber-toothed cats remained fearsome predators. Unlike modern big cats such as lions and tigers, Homotherium’s narrow, blade-like teeth were “precision weapons”, Antón said. “Once the sabers cut the arteries in the neck,” he added, “the animal was losing blood very quickly and fainting within seconds.”
A lion’s upper canines are about 1.5 inches long. Homotherium were 3 inches long. Those of the largest saber-toothed cat, the 900-pound Smilodon fatalis, were perhaps 6 inches long, which is why the new findings don’t apply to Smilodon’s teeth: no jaw could accommodate such a tooth.
Even so, the study’s authors wonder where detective stories like this might lead next. “We know about 30 to 40 species of saber-toothed cats,” Dr. Siliceo said, “but there are still many more to be found.” Even this year, Chinese scientists described a previously unknown dwarf sabertooth and another the size of a jaguar.
According to Mr. Antón, this could be just the beginning. “We have a whole biosphere in the drawers of the museum just waiting to be discovered.”