Factoid of the Week February 9, 2017 Exhibit Spotlight: Smilodon
Factoid of the Week February 9
Exhibit Spotlight: Smilodon
As an icon of prehistory, the Sabertooth Tiger looms large in the popular imagination. Sometimes this leads to misinterpretations of fossil evidence, leading to legends often mistaken for science. Then again, this spectacular creature often lives up to its own legendary status.
First off, it’s not a tiger. Modern cats and the sabertooths diverged from a common ancestor roughly 14 million years ago. The epithet “saber-toothed cat” more accurately describes the animal in terms of its pedigree. Since they both probably occupied an apex predator niche, the term “tiger” might seem to fit fine, but consider this: lions, orcas, Tyrannosaurus rex, and humans occupy that niche as well, but calling them tigers seems a bit more metaphorical, yes?
Scientists currently recognize three species of Smilodon: gracilis, fatalis, and populator. The oldest species, Smilodon gracilis, first appeared between 2.6 and 1.8 million years ago. The smallest and rarest Smilodon species, it ranged across the United States from California to Florida, and as far north as Pennsylvania. It may also have lived as far south as Venezuela.
Thanks to the Rancho la Brea Tar Pits, Smilodon fatalis is the best understood species. It also has by far the most intimidating name. Heavier in build than S. gracilis, it shared North and Central America with its smaller cousin until about 500,000 years ago, and survived until the end of the great Ice Age.
The youngest species, S. populator, ranks as the largest cat currently known to science. It dominated ecosystems in South America for about a million years, but does not seem to have ventured into its North American cousins’ domains. Taken together, the three Smilodon species show a clear evolutionary trend that favored size. Other aspects of these animals remain much less clear.
I’ve detailed the three species separately to illustrate a point: in paleontology, dealing with vast amounts of time and a lack of data sometimes forces us to take the long view. We end up overgeneralizing about behavior and body features, we downplay the possibilities of variety across populations and geography, or set competing hypotheses against one another when each might prove true for different species. To get an idea for the possibilities, let’s compare Smilodon with the still-living genus of big cats, Panthera. This genus comprises 5 living and about 8 extinct species. The living species include lions, tigers, leopards, jaguars, and snow leopards. Panthera behavior ranges from solitary to social, all except the snow leopard can roar, and just look at the variety of coloration! Hotly argued issues on Smilodon like hunting strategy and sociality may have differed just as much among its species as modern Panthera. S. fatalis may have formed prides, while S. populator and S. gracilis walked by themselves (a little Rudyard Kipling reference, there). S. gracilis may have ambushed prey from trees, while S. fatalis and S. populator may have run prey to ground. Unless we acknowledge the possibility of sharply divergent lifestyles in spite of similar body forms, we risk hampering our own investigations with pet ideas. Soapbox rant achieved!
NO overview on these cats should skip addressing those massive, bizarre fangs. They could measure up to 11 inches long in S. populator, although about 1/3 of that length would have been embedded in the skull. Their length corresponds with an increase in the animal’s gape—where modern lions can only open their mouth about 60˚, Smilodon could achieve a snake-like 120˚. To accommodate such an extreme hinge, its jaw muscles were reduced, giving it a much weaker bite than modern big cats.
The blade-like shape of these fangs and the presence of serrations may indicate a slashing function, although this hypothesis is highly contested. The animals’ heavily-muscled neck, shoulders, and forelimbs may have held prey fast, allowing the cat to target and sever key blood vessels. Though such a strategy makes sense, it has proven difficult to test. One study went so far as to build a robot to simulate a Smilodon’s bite, but it could reach no final conclusion. Competing explanations for those massive choppers include what I’ll call the “Crampon Theory.” That is, the teeth helped the animal grip its prey’s throat, following the suffocation strategy used by many modern cats.
In any case, once Smilodon started eating, those big fangs might have necessitated delicate, deliberate feeding behaviors. With a weaker bite, it might not have had as easy a time cracking open bones, limiting its efficiency in getting nutrition from each kill. Likewise, the size and shape of the fangs may have subjected them to greater stresses, leading to increased breakage. However these fangs functioned, they still had their share of drawbacks.
Our exhibit may feature two species of Smilodon. A skull labeled “Smilodon californicus” on the second level actually represents S. fatalis. I’m tempted to call the outdoor sculptures S. gracilis thanks to the lighter build and smaller size of the adult, but the presence of dire wolves in the display means it’s probably meant to represent S. fatalis as well. —Jeff Bond