Metailurini
Homotheriini
Smilodontini Machairodontinae is a subfamily of family Felidae, the family which contains all true cats. Machairodontinae contains the cats we know as "saber-toothed cats", and though many of the cats show only minor increase in the size and length of their canine teeth, it also contains the famed genus of Smilodon.

There are two basic types of Machairdontinae: dirk-toothed and scimitar-toothed. Dirk-toothed cats had elongated, narrow upper canines and generally had stocky bodies. Scimitar-toothed cats had broader and shorter upper canines and a typically more lithe form and longer legs. Long-toothed cats often had a bony flange that extended from their lower mandible. However, one genus of cats, Xenosmilus , breaks this mould, possessing both the stout heavy limbs associated with dirk-toothed cats, along with the stout canines of a scimitar-toothed cat.

In spite of the common name, saber-toothed 'tigers', these felines could be more properly referred to as saber-toothed cats. They were not even in the same subfamily as tigers, there is no evidence that they had tiger-like coat patterns, and this broad group of animals certainly did not all live or hunt in the same manner as the modern tiger.

It is commonly thought that saber-toothed cats lived only in cold areas caused by an ice age.While some certainly did live in snowy conditions and/or during an ice age, many lived in warmer climates, both before, during and after an ice age. Machairodonts stretch back into the Oligocene and only became extinct in the last 10,000 years.

The way machairodonts hunted is hotly debated. It was originally suggested that they must have used a 'stabbing' motion with their teeth (dropping their jaws wide open, baring their teeth, and thrashing downward). This is unlikely, for the teeth, being so long, were fragile, and a large prey animal thrashing about could easily injure the teeth, which would impair hunting. Some suggested that they may have slashed at the belly of large animals with their teeth and waited for them to die of blood loss. This is more plausible (though risk of breakage is still high), However, when the bite of a dirk toothed cat is compared to the neck of a large ungulate it matches up with animals neck to show a bite that would severe all arteries and veins, along with acting as a clamp around the windpipe. This is still risky for their teeth if the prey moved overly much, but less risky than the stabbing method, for with the neck bite, they would be anchored with their incisors and lower canines. Also, if they worked in prides (there is evidence that some species may have), they could subdue the animal before performing the killing bite.