Some 5-9 million years ago, a bad boy called Machairodus lahayishupup roamed the open spaces in North America (pronounced Mah-CHI-rho-duss Lah-HIGH-ees-hoop-oop). It was the largest cat of its time (that we know of, at least), weighing up to 900 pounds (410 kg) and hunting pretty much everything that moved, including prey ten times larger than itself.

Big teeth, big cats

Animals in the Machairodus genus are thought to be largely similar to today’s lions or tigers, with a couple of major distinctions; one, when it comes to their teeth. The saber-toothed cats, as their name implies, had long canines protruding from the mouth. The canines are thin and flattened, like the blade of a knife or (you’ve guessed it) a saber.

M. lahayishupup was no different in this regard, but it was different in terms of size.

“We believe these were animals that were routinely taking down bison-sized animals,” said study co-author Jonathan Calede, an assistant professor of evolution, ecology, and organismal biology at The Ohio State University’s Marion campus. “This was by far the largest cat alive at that time.”

Calede worked on the study with John Orcutt, assistant professor of biology at Gonzaga University, who initiated the project. Orcutt had found a large fossil that had been labeled as a cat when he was a graduate student, but he didn’t really know what species it was. The two researchers analyzed similar fossils from museums in Oregon, Idaho, California, and Texas to get to the bottom of it.

The researchers had no complete fossils, so they had to make deductions based on incomplete fossils — forearm bones in particular. They figured that if forearm bones can indeed tell ancient species apart, that would also be true for modern cats. So they visited museums and photographed forearm specimens of lions, pumas, panthers, jaguars, and tigers. They then used specialized software to digitize and analyze the photos, creating a model of each elbow.

“We found we could quantify the differences on a fairly fine scale,” Calede said. “This told us we could use the elbow shape to tell apart species of modern big cats.

“Then we took the tool to the fossil record – these giant elbows scattered in museums all had a characteristic in common. This told us they all belonged to the same species. Their unique shape and size told us they were also very different from everything that is already known. In other words, these bones belong to one species and that species is a new species.”

They realized that the new species is a relative of the saber-toothed cats — an old cousin to the famous Smilodon that went extinct about 10,000 years ago. But this newly discovered species lived some 5-9 million years ago and was much bigger than its relatives.

“We’re quite confident it’s a saber-toothed cat and we’re quite confident it’s a new species of the Machairodus genus,” Orcutt said. “The problem is, in part because we haven’t necessarily had a clear image in the past of how many species were out there, our understanding of how all these saber-toothed cats are related to each other is a little fuzzy, particularly early in their evolution.”

America’s own saber-toothed cat

The researchers thought that, in addition to confirming its status as a new species, these bones could also offer information about its size and habits. They calculated the association between bone size and body mass in modern big cats and then extrapolated it to the fossils, estimating its size and weight.

Based on how big it was, it would have also hunted large prey. At the time rhinoceros were particularly abundant, as well as giant camels and giant ground sloths, so researchers think that’s what it would have tried to prey on.

But while these findings help us understand ecosystems in America a few million years ago, it also raises an interesting question: at a time when Europe and the Americas were already separated for a long time, why did animals evolve in such a similar way? There are no saber-toothed cats now, so what was it that pushed evolution in this direction at the time?

“It’s been known that there were giant cats in Europe, Asia and Africa, and now we have our own giant saber-toothed cat in North America during this period as well,” he said. “There’s a very interesting pattern of either repeated independent evolution on every continent of this giant body size in what remains a pretty hyperspecialized way of hunting, or we have this ancestral giant saber-toothed cat that dispersed to all of those continents.

“It’s an interesting paleontological question.”

The study was published in the Journal of Mammalian Evolution.