Size and Weight:
About the American Lion (Panthera Leo Atrox):
Contrary to popular belief, the "saber-toothed tiger" (more accurately referred to by its genus name, Smilodon) wasn't the only feline apex predator of Pleistocene North America: there was also the American Lion, Panthera leo atrox. If this plus-sized cat was in fact a true lion--some paleontologists speculate that it may have been a species of jaguar or tiger--it was the biggest of its kind that ever lived, outweighing its contemporary African relatives by hundreds of pounds. Even still, the American Lion was no match for Smilodon, a more heavily built predator (only distantly related to the Panthera family) that employed an entirely different hunting style.
On the other hand, the American Lion may have been smarter than Smilodon; in prehistoric times, thousands of saber-toothed tigers got trapped in the La Brea Tar Pits in search of prey, but only a few dozen specimens of Panthera leo atrox. Intelligence would have been a valuable trait in the competitive landscape of Pleistocene North America, where the American Lion had to out-hunt not only Smilodon, but also the Dire Wolf (Canis diris) and the Giant Short-Faced Bear (Arctodus simus). Unfortunately, by the end of the last Ice Age, all of these vicious carnivores occupied the same dismal playing field, hunted to extinction by early humans at the same time as climate change and a reduction in their accustomed prey thinned out their populations.