The Extinct 'American Cheetah' Wasn't a Cheetah — and Some Ate Only Fish

The extinct Miracinonyx trumani, long nicknamed the 'American cheetah' for its slender body and long legs, was more closely related to modern pumas than to African cheetahs, according to a new study in the journal Current Biology. Some populations living near the Arctic ate almost exclusively fish, challenging the assumption that these animals chased fast-running prey like pronghorns.

"It's very hard to imagine a prehistoric species we've never seen without comparing it to something we know," said Molly Cassatt-Johnstone of the University of California, Santa Cruz, the paper's first author. M. trumani roamed North America's open grasslands during the Pleistocene epoch, from about 2.5 million to 16,000 years ago, and its slender body, long forelimbs and large nasal cavities resembled those of fast-running animals such as cheetahs or horses, leading researchers to assume a cheetah-like lifestyle.

The team sequenced the most complete M. trumani ancient DNA data set so far from four specimens, one from Wyoming and three from Canada's Yukon Territory, confirming the Yukon samples belonged to M. trumani and extending its known range more than 20 degrees of latitude, or over 1,400 miles, farther north than previously known. Comparing this DNA with nine other cat species, the researchers found M. trumani shared a common ancestor with modern cheetahs about 4.7 million years ago, but was most closely related to pumas, having diverged from a shared ancestor about 2.6 million years ago.

Analyzing nitrogen and carbon in the Yukon fossils to determine diet, the researchers found the Yukon individuals preyed almost exclusively on fish, with nitrogen profiles resembling those of fish-specialist orcas and sea wolves off British Columbia's coast. In contrast, the Wyoming M. trumani had nitrogen markers of a terrestrial predator eating mostly herbivores, similar to lions. The researchers also found two of the species' circadian rhythm genes were nonfunctional, which may suggest populations at high latitudes adapted to extreme daylight and darkness, or were nocturnal. Like the woolly mammoth, M. trumani likely went extinct as the last ice age gave way to the warmer Holocene.