For decades, paleontologists have explained that: Mirasinonychus tormani — an extinct species of cheetah-like cat that roamed the grasslands and steppes of North America more than 13,000 years ago — as North America’s answer to African cheetah (Acinonychus jubatus). A new study led by the University of California, Santa Cruz suggests that this view was largely wrong.
Mirasinonychus tormani and the ecosystem in which this species lived. Image credit: Julius Csotonyi.
Mirasinonychus tormani They roamed the open grasslands of North America during the Pleistocene epoch, about 2.5 million to 13,000 years ago.
According to fossils discovered so far, this species was 90 cm tall, approximately 2.5 m long to the tip of its tail, and weighed an average of 70 kg.
It has a slender body, long forelimbs, and a large snout, characteristics characteristic of modern fast running animals such as cheetahs and horses.
some Mirasinonychus tormani The fossils were unearthed alongside those of the pronghorn, a fast-running animal known colloquially as the “American antelope,” leading researchers to speculate that the extinct cat may have lived a lifestyle similar to modern-day African cheetahs.
“These cats were incredibly flexible, much like mountain lions in their range today,” says Dr. Molly Cassatt-Johnston. candidate at the University of California, Santa Cruz.
“We found loss-of-function mutations in certain genes that regulate circadian rhythms, suggesting they may have adapted to the extreme photoperiods of summer and winter in the northern hemisphere.”
Cassatt-Johnston and her colleagues used ancient DNA extracted from four tissues. Mirasinonychus tormani The specimens — one from Natural Trap Cave in Wyoming and three from Yukon Territory — sequenced the first high-coverage nuclear genome of an ancient species.
“It’s very difficult to imagine prehistoric species that we’ve never seen before without comparing them to what we know,” says Cassatt-Johnston.
“However, this approach can limit our understanding of the complexity, unique evolutionary history, and behavior of ancient animals.”
Genetic analysis suggests that felines are the closest relatives of modern animals. Puma (puma conqueror)We confirmed and extended previous findings based on more restricted mitochondrial DNA rather than cheetahs.
It is estimated that the two lineages diverged about 2.6 million years ago. Mirasinonychus tormaniThe cheetah’s sleek physique is thought to be an example of convergent evolution. Rather than sharing an ancestor with the African cheetah, a similar body shape arose independently in response to hunting pressure in a similar field habitat.
The Yukon fossils also dramatically push the species’ known range northward by more than 20 degrees of latitude, indicating that the cat lived in arctic grassland and tundra environments approximately 31,000 to 34,000 years ago, far beyond the temperate grasslands where most of its earlier fossils were found.
Two of the Yukon specimens were initially misidentified as mountain lions due to their remote location. Mirasinonychus tormaniexpected range.
Chemical signatures in the collagen of fossil bones indicate striking differences in diet between populations.
The Wyoming individuals exhibited isotopic values typical of a common land hunter, consistent with a mixed diet base in an open grassland ecosystem.
In contrast, Yukon individuals have nitrogen isotope values about 6 times higher than other carnivores in the region, a characteristic best explained by their dependence on salmon and other fish that migrate upstream from oceans hundreds of kilometers inland.
The genomes also revealed several dysfunctional genes common to both populations. These include two genes involved in the regulation of circadian rhythms (which may reflect the relaxation of evolutionary pressures on daily photoperiods at high latitudes) and a gene associated with sour taste perception, which appear to be commonly disrupted across cat species.
Both populations had low genetic diversity, comparable to some of today’s most inbred endangered cats, but there was no evidence of the severe inbreeding bottlenecks seen in species such as the Iberian lynx.Lynx).
Taken together, the findings suggest that Mirasinonychus tormani Rather than being specialized sprinters chasing pronghorn across the plains, they were adaptable predators that could exploit very different food sources over a vast range.
“Unfortunately, there are probably other extinct species that have been reduced to smaller dimensions than they should be,” says Cassatt-Johnston.
” Mirasinonychus tormani Fossils suggest that the ‘American cheetah’ was far more adaptable than its nickname suggests. ”
“These carnivores are widespread from the North Pole to 48 degrees north latitude,” said Matthew Wooler, a professor at the University of Alaska Fairbanks.
“They demonstrate hyperspecialty at both ends of their range, while also consuming two very different food sources.”
“Low genetic diversity itself did not determine the fate of this species,” said Beth Shapiro, a professor at the University of California, Santa Cruz.
“Mirasinonychus tormaniIt persisted for a very long time without any signs of inbreeding that would be expected before its collapse. ”
“The decline was gradual rather than sudden, which may be why they were unable to adapt to climate change.”
a paper The survey results were published in today’s magazine current biology.
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Molly Cassatt Johnston others. Habitat and dietary diversity of the Pleistocene American “cheetah” Mirasinonychus tormani. current biologypublished online on September 4, 2026. doi: 10.1016/j.cub.2026.07.072
Source: www.sci.news
