Smilodon fatalis – one of the last great sabercats – was a ferocious carnivore. Gaping museum mounts are a reminder of the extinct cat’s destructive capabilities. But such menacing skeletons only offer a snapshot of predator’s life. It’s not as if Smilodon sprung from the ground fully-formed and started tearing after the nearest baby mammoth. If there were sabercats, there must have been saberkittens.
When I visited the famous La Brea asphalt seeps last year for a Smilodon story, I asked curator John Harris and collections manager Aisling Farrell if they had any young sabercats in the rows upon rows of chocolate-colored bone collected from the site. They led me to a specific tray among the racks of immaculately-cleaned Smilodon bones and, sure enough, there were skull pieces from several juvenile cats nestled against the plastic.
It was heartbreaking to think of the unwary saberkittens becoming trapped in the black ooze. If I happened across such a scene I would rush to pick up the cats, end up trapped in the tar myself, and, following anthropological convention, be named “Cat Man” when paleontologists later discovered the associated skeletons. But although the thought of helpless, tar-matted Smilodon kittens is tragic, their bones have not gone to waste. Their rare remains, and those of their older kin, are helping paleontologists understand how roly-poly Smilodon infants grew up into intimidating throat-rippers.
Like all cats, Smilodon got through life with two sets of teeth. Their first dental armaments were milk teeth, including canines that were not quite so long as their parents’ but were still flattened and saber-like. And much like kittens you may have raised yourself, little Smilodon kept their milk teeth until their adult teeth pushed the old ones out of the way. Skulls of this transition in action show the sabercat’s awkward, double-fanged teething phase.
Those adult fangs came in quick. In a pair of papers, University of California paleontologist Robert Feranec looked to the teeth of adult La Brea Smilodon to estimate the growth of the famous weapons. By tracking fluctuations of carbon and oxygen isotopes, which were laid down in the enamel of the two sampled Smilodon canines as they formed, Feranec determined that those distinctive, permanent slashers grew at a rate of about 5.8mm each month over a period of 22 months. In the same amount of time it takes modern lions to grow their adult canines, Smilodon sprouted insanely-long slashers.
Despite the high rate of growth, though, 22 months was a long time for a Smilodon to be without its fully-developed cutlery. The saber teeth would have been functional before they ceased growing, of course, but many months of early growth – when their grown-up canines were pushing aside their milk fangs bit-by-bit – likely kept young Smilodon cute for a long time. An extended period of infancy and weaning, megafauna expert Ross Barnett pointed out on Twitter, might mean that saberkittens stayed adorable and playful for longer than other cats. Science has yet to ascertain how dangerous it would have been to give saberkittens chin scritches, however.
[A big hat-tip to paleontologist Ross Barnett for pointing me to Feranec's papers.]
Feranec, R. 2004. Isotopic evidence of saber-tooth development, growth rate, and diet from the adult canine of Smilodon fatalis from Rancho La Brea. Palaeogeography, Palaeoclimatology, Palaeoecology. 206, (3-4): 303-310
Feranec, R. 2008. Growth differences in the saber-tooth of three felid species. PALAIOS. 23: 566-569