The Smilodon were descendants of Megantereon, the ancestor of the cat subfamily Machairodontinae. His American Continent descendants included Smilodon Populator of South America and the North America's Smilodon Fatalis, Smilodon Californicus and Smilodon Floridanus.
The Smilodon was a little shorter then the common day Lion but possessed twice its weight. From studying their remains it is clear that their short but powerful hind legs did not encourage chasing prey.
They were designed to stalk and ambush larger prey from short distances. It is thought that their diets consisted mainly of Baby Mammoths, Ground Sloths, Mastedons and other slower moving Plant Eaters.
There have been numerous theories concerning how the Saber-tooth used its massive canines to kill.
Because the Canines were less indestructible than they might have looked, the theory closest to reality is; instead of attacking the prey by biting into the spine, where there was a higher risk of tooth breakage, they would attack a soft fleshy area, either the underbelly or the underside of the neck, producing a devastating slashing wound that would induce quick death from shock and blood loss.
No one knows exactly how a Smilodon looked. The common rendition shows the colorization of a lion. Smilodon Fatalis, which lived in the North American Woodlands, would have been better served by having the spotty coloration of a leopard or the grey appearance of a wolf.
It is hard to imagine that they could have stalked and survived as long as they did, without being able to blend in with the fauna of their surroundings.