American Cheetah - Miracinonyx inexpectatus
Temporal range: 1.8–0.011 Ma
Species: Miracinonyx inexpectatus
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.
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.
Miracinonyx inexpectatus was larger than a modern Cheetah and similar in size to a modern northern Cougar. Body mass was typically around 70 kg (150 lb) with a head-and-body length of 170 cm (67 in), tail length of around 92 cm (36 in) and a shoulder height of 85 cm (33 in). Large specimens could have weighed more than 95 kg (210 lb).
Taxonomy and evolution
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. 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). 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. 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; where M. inexpectatus fits in is unclear, although it likely is a more primitive version of M. trumani.
M. inexpectatus was more similar to the Cougar than was M. trumani, its proportions between that of the Cougar and M. trumani. It had fully retractable claws, combined with it´s lighter built made the Miracinonyx inexpectatus was likely faster than the Cougar. Due to the retractable claws it is also possible that he had been more adept at climbing than M. trumani.