Miracinonyx trumani, an extinct big cat commonly known as the American cheetah, lived in North America during the Pleistocene. Its nickname comes from its resemblance to modern cheetahs, including physical traits suited for high-speed pursuit. But scientists’ understanding of this ancient predator has changed in recent years, and now, researchers have uncovered surprising new details about the species.
The findings, published today in the journal Current Biology, add to a growing body of evidence that suggests this “cheetah” wasn’t a cheetah after all. Rather, it was a highly adaptive relative of the puma. This new study also expands M. trumani’s range northward. While populations in regions known today as Wyoming and Florida lived as generalist predators in temperate grasslands, populations in the Arctic Yukon—once part of Beringia, a prehistoric land bridge that connected Asia to North America during the last Ice Age—specialized in eating fish.
Prior to this study, experts had no idea M. trumani lived so far north. The fact that this population carved out its own unique niche, dining primarily on salmon and other fish to survive in a harsh ecosystem, speaks to its incredible adaptability.
“The Pleistocene Beringia is a really well-studied paleontological ecosystem, so it’s very cool to be able to add a new carnivore into a really well-studied ecosystem,” lead author Molly Cassatt-Johnstone, a Ph.D. candidate in the Paleogenomics Lab at the University of California, Santa Cruz, told Gizmodo.
The mystery of the American cheetah
When the American cheetah was first named and officially described in 1979, fossil evidence pointed to its strong convergent morphology, or shared features, with modern cheetahs. For example, these ancient cats had elongated legs and large sinuses, both classic adaptations for chasing prey at high speeds, according to Cassatt-Johnstone.
“That was kind of the first understanding of this species,” she said. “We’ve got an American cat that seems adapted for high-speed pursuit, so we have an American cheetah.” But as scientists dug deeper, their picture of this long-lost predator grew more complicated.
In 2005, researchers sequenced mitochondrial DNA from an M. trumani fossil found in Wyoming, creating the first genetic record of the American cheetah. However, their findings suggested that this species was more closely related to modern pumas than cheetahs, “which evolutionarily makes sense,” Cassatt-Johnstone said.
“Pumas are a new world lineage; they are found in the Americas. Cheetahs are old world, so in Asia and Africa, and so there would have had to have been a migration event if they were most closely related to cheetahs,” she explained.
Over the last decade, more studies have challenged the assumption that M. trumani was a specialized, high-speed predator. The findings published today confirm that this cat was not only far less cheetah-like than scientists once believed but also likely has no modern analog.
A cat of its own
Cassatt-Johnstone and her colleagues analyzed ancient DNA and stable isotopes from big cat fossils found as far north as the Yukon. When the researchers first received the 23,000- to 31,000-year-old specimens, they thought they might be pumas, as paleontologists had found remains of those cats in the region before.
“Our job was to figure out what [species] they belonged to, and we were super surprised when we found out they weren’t pumas, they were American cheetahs,” Cassatt-Johnstone said. Until then, experts had not thought this species lived in Beringia. Its presence there is particularly surprising given that the region was heading into the Last Glacial Maximum, so the Arctic ecosystem was vastly different from that of the lower 48.
The genetic analysis confirmed that M. trumani was actually a sister species of the modern puma, having diverged from that lineage about 2.6 million years ago. The researchers now believe that its cheetah-like features are a striking example of convergent evolution—when two unrelated species (in this case, M. trumani and the modern cheetah) evolve similar traits to survive in similar environments. Indeed, M. trumani populations that roamed the North American grasslands likely needed to be fast to catch their prey.
But those that ventured into the frozen North clearly needed to find another way to eat. By analyzing stable isotopes from the fossils, the researchers reconstructed the animals’ diets. Those that lived in the Arctic specialized in eating fish, likely using their powerful forelimbs to snatch them out of the water.
“Reconstructing their diet was really surprising, and I think really shows that these cats—like other living cats or other living species today—are incredibly flexible,” Cassatt-Johnstone said. “They’re able to predate and exist and engage with their ecosystem in very different ways, depending on where they live and what resources are around them.”
While the debate over M. trumani‘s lineage may be settled, there are still questions that remain unanswered. Cassatt-Johnstone hopes future studies will dive deeper into the evolutionary history of this species and the puma to figure out if they were coexisting within North America and whether there was competitive overlap between them.
