For decades, paleontologists described Miracinonyx trumani, an extinct North American felid, as the continent’s answer to the African cheetah. New genetic research led by the University of California, Santa Cruz, upends that picture. Ancient DNA pulled from four fossils shows the animal’s closest living relative is the puma, not the cheetah, and that its range stretched from Wyoming grasslands to Arctic river valleys in the Yukon. The genomes also reveal a Yukon population that appears to have lived on migrating fish rather than chasing pronghorn across open plains.
A Body Built for Speed, Interpreted a Different Way
Based on fossils uncovered to date, Miracinonyx trumani stood about 90 centimeters, or three feet, tall, stretched roughly 2.5 meters (eight feet) from nose to tail tip, and weighed around 70 kilograms (150 pounds) on average. Its slender body, long forelimbs, and large nasal cavities are features shared with modern fast-running animals such as cheetahs and horses. Some of its fossils have turned up alongside those of pronghorns, animals known colloquially as the American antelope, which led earlier researchers to assume the felid hunted them much the way an African cheetah runs down open-plains prey.
Sequencing Genomes from Wyoming and the Yukon
Molly Cassatt-Johnstone, a Ph.D. candidate at the University of California, Santa Cruz, and her colleagues extracted ancient DNA from four Miracinonyx trumani specimens, one from Natural Trap Cave in Wyoming and three from Yukon Territory, to sequence the first high-coverage nuclear genomes of the species. The results, detailed in an account of the study, describe a felid that behaved more like a generalist puma than a specialized sprinter. “It’s very hard to imagine a prehistoric species we’ve never seen without comparing it to something we know,” Cassatt-Johnstone said, “but this approach can limit our understanding of ancient animals’ complexity, unique evolutionary histories, and behaviors.”
“These cats were remarkably flexible, much like pumas are across their range today,” Cassatt-Johnstone added, describing loss-of-function mutations the team found in genes that regulate circadian rhythms, a pattern that suggests the animals adapted to the extreme light cycles of Arctic summers and winters.
Nuclear DNA Settles the Puma Connection
The genetic analysis places Miracinonyx trumani as the closest relative of the living puma (Puma concolor), not the cheetah, confirming and extending earlier work based on more limited mitochondrial DNA. The two lineages appear to have split around 2.6 million years ago. The species’ sleek, cheetah-like build looks like a case of convergent evolution: similar body shapes arising independently in response to similar open-habitat hunting pressures, rather than shared ancestry with the African cheetah.
Yukon Fossils Push the Range Into the Arctic
The Yukon fossils extend the species’ known range dramatically northward, by more than 20 degrees of latitude, showing that it lived in Arctic steppe-tundra environments roughly 31,000 to 34,000 years ago, far beyond the temperate grasslands where most previous fossils had been found. Two of the Yukon specimens had originally been misidentified as pumas, precisely because their location fell so far outside where researchers expected to find Miracinonyx trumani.
“This species of carnivore has this massive range, all the way from the Arctic to the Lower 48,” said Matthew Wooller, a professor at the University of Alaska Fairbanks. “They’re demonstrating uber-specialization at two ends of their range, while also feeding on two completely different food sources.”
Isotopes Point to a Fish-Eating Population in the North
Chemical signatures in the fossils’ bone collagen point to a striking dietary split between the two populations. The Wyoming individual showed isotope values typical of a generalist terrestrial hunter, consistent with the mixed prey base of an open grassland ecosystem. The Yukon individuals, by contrast, carried nitrogen isotope values roughly six parts per thousand higher than other carnivores in the region, a signature best explained by reliance on salmon and other fish that migrate upriver from the ocean, hundreds of kilometers inland. A university announcement of the findings described the Yukon population as tertiary consumers that had carved out a niche unlike anything expected of a cheetah-like sprinter.
What Low Genetic Diversity Reveals About the Species’ Decline
The genomes also showed a handful of disabled genes shared by both populations, including two involved in regulating circadian rhythms (a possible sign of relaxed evolutionary pressure on daily light cycles at high latitudes) and a gene tied to sour-taste perception that appears to be broken across cat species generally. Both populations showed low genetic diversity, comparable to some of today’s most inbred endangered cats, though without evidence of the severe inbreeding bottlenecks seen in species such as the Iberian lynx.
“Low genetic diversity didn’t doom this species by itself,” said Beth Shapiro, a professor at the University of California, Santa Cruz. “Miracinonyx trumani persisted for a very long time without the signs of inbreeding we’d expect before a collapse.” “The decline was slow, not sudden, and that may be what left it unable to adapt when the climate shifted.” The study appeared in the journal Current Biology.
Cassatt-Johnstone said the reassessment illustrates a broader problem with how extinct animals get remembered. “There are probably other extinct species that, unfortunately, have been reduced to fewer dimensions than they deserve,” she said. “The Miracinonyx trumani fossils suggest that this ‘American cheetah’ was far more adaptable than its nickname implies.”
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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