| American cheetah | |
|---|---|
| Miracinonyx trumani | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Family: | Felidae |
| Genus: | Miracinonyx |
| Species | |
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Miracinonyx (American cheetahs) is an extinct genus of the family Felidae, endemic to North America during the Pleistocene epoch (1.8 mya—11,000 years ago), existing for approximately 1.8 million years.[1]
There were at least two species of feline morphologically similar to the modern cheetah. Living from three million to ten or twenty thousand years ago in North America, these cats are known only from fragments of skeletons. The two species commonly identified are Miracinonyx inexpectatus and M. trumani. Sometimes a third species, M. studeri, is added to the list, but it is more often listed as a junior synonym of M. trumani. Both species are similar to the modern cheetah, with faces shortened and nasal cavities expanded for increased oxygen capacity, and legs proportioned for swift running. However, these similarities may not be inherited from a common ancestor, but result from either parallel or convergent evolution.
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Research into the American cheetah has been contradictory. It was originally believed to be an early cougar representative, before being reclassified in the 1970s as a close relative of the cheetah.[2] This suggested that ancestors of the cheetah diverged from the Puma lineage in the Americas and migrated back to the Old World, a claim repeated as recently as Johnson et. al. (2006).[3] Other research by Barnett, however, examining mitochondrial DNA and re-analyzing morphology, has suggested reversing the reclassification: the American cheetah developed cheetah-like characteristics through convergent evolution, but it is most closely related to Puma and not to the modern cheetah of Africa and Asia.[4] The supposed American origin of the modern cheetah is thus equivocal; however, it is believed to have evolved from cougar-like ancestors, whether in the Old or New World.
The cougar and M. trumani are believed to have split from a cougar-like ancestor around three million years ago;[4] where M. inexpectatus fits in is unclear, although it likely is a more primitive version of M. trumani.[5]
M. trumani was the most similar to true cheetahs in morphology. Living on the prairies and plains of western America, it was likely a predator of hoofed plains animals such as the pronghorn. In fact, predation by Miracinonyx is thought to be the reason that pronghorns evolved to run so swiftly, their 60 mph top speed being much more than needed to outrun extant American predators such as cougars and gray wolves.[6]
M. inexpectatus was more similar to the cougar, its proportions between that of the cougar and M. trumani. It had fully retractable claws and although it was likely faster than the cougar due to its slim build, it is also thought to have been more adept at climbing than M. trumani.