Despite the way they're portrayed in movies, saber-tooth cats weren't just big felines that happened to have enormous front teeth. The whole lifestyle of saber-toothed cats (and their close cousins, the scimitar-tooths, dirk-tooths and "false" saber tooths) revolved around using their armament to wound and kill prey, most often giant herbivores, but occasionally early hominids and other big cats. (See a gallery of saber-toothed cat pictures.)
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That said, let's get a couple other issues out of the way early on. First, the most famous prehistoric cat, Smilodon, is often referred to as a "saber-toothed tiger," but the word "tiger" actually refers to a specific, modern genus of big cat. More properly, Smilodon should be called a saber-toothed cat, just like its large-fanged contemporaries of the Tertiary and Quaternary periods. And second, as with many features in nature, the saber-tooth head plan evolved more than once, and not just in cats, as we'll see below.
Saber-Toothed Cats: True or False?
The first carnivores that could reasonably be described as "saber toothed" were the nimravids, primitive, vaguely cat-like beasts that lived about 35 million years ago. As closely related to early hyenas as they were to early cats, nimravids weren't technically felines, but genuses like Nimravus and Hoplophoneus boasted some impressive canines.
For technical reasons (mostly involving the shapes of their inner ears), paleontologists refer to nimvravids as "false" saber tooths, a distinction that makes less sense when you take a gander at the skull of Eusmilus. The two front canines of this leopard-sized nimravid were almost as long as its entire skull, but their thin, dagger-like structure places this carnivore firmly in the "dirk-toothed" category ("dirk" being the ancient Scottish word for "dagger").
Confusingly, even some primitive felines are categorized as "false" saber tooths. A good example is the aptly named Dinofelis ("terrible cat"), whose somewhat short, blunt canines, though bigger than those of any large cat alive today, don't merit its inclusion in the true saber-tooth camp. Even so, Dinofelis was a menace to other mammals, including the early hominid Australopithecus (which may have figured on this cat's dinner menu).
Exclusion from the camp of "true" saber-toothed cats makes more sense in the case of Thylacosmilus. This was a marsupial mammal that raised its young in pouches, kangaroo-style, rather than a placental mammal like its true saber-toothed cousins. Ironically, Thylacosmilus went extinct about two million years ago when its South American habitat was colonized by true saber-tooths migrating down from the North American plains.
The Kings of the Saber-Tooths: Smilodon and Homotherium
Smilodon (and no, its Greek name has nothing to do with the word "smile") is the animal that most people have in mind when they refer to "saber-toothed tigers." This long-fanged carnivore was a bit shorter, stockier and heavier than the typical modern-day lion, and it owes its fame to the fact that thousands of Smilodon skeletons have been fished out of the La Brea Tar Pits in Los Angeles (whose film industry has immortalized "saber-toothed tigers" in countless caveman flicks). Although Smilodon probably snacked on the occasional hominid, the bulk of its diet consisted of the large, slow herbivores crowding the American plains.
Smilodon had a long time in the sun, persisting from the beginning of the Quaternary period (a few million years ago) to about 10,000 B.C., when early humans hunted the dwindling population to extinction. The only other prehistoric cat to match Smilodon's success was Homotherium, which spread across wider territory (Eurasia and Africa, as well as North and South America) and was perhaps even more feared. Homotherium's canines were sleeker and sharper than those of Smilodon (which is why paleontologists call it a "scimitar-toothed" cat), and its hunched, hyena-like posture may have been more intimidating. (Homotherium may have resembled hyenas in another respect: there's evidence that it hunted in packs, a good strategy for bringing down multi-ton mammoths.)
Next Page: the Lifestyles of Saber-Toothed Cats, and a List of Major Genuses
