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.
The similarity between M. trumani and the cheetah is an example of parallel evolution. As grasslands became more common in both Africa-Eurasia and North America, cougar-like cat species from both continents evolved to catch the new fleet-footed herbivores. The claws of M. trumani had even become only partially retractable, to be used for better grip at high speeds.
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.