Evidence suggests saber-toothed cats held onto their baby teeth to stabilize their sabers
California's state fossil—are familiar to anyone who has ever visited Los Angeles' La Brea Tar Pits, a sticky trap from which more than 2,000 saber-toothed cat skulls have been excavated over more than a century.
Though few of the recovered skulls had sabers attached, a handful exhibited a peculiar feature: the tooth socket for the saber was occupied by two teeth, with the permanent tooth slotted into a groove in the baby tooth.
Paleontologist Jack Tseng, associate professor of integrative biology at the University of California, Berkeley, doesn't think the double fangs were a fluke.
Nine years ago, he joined a few colleagues in speculating that the baby tooth helped to stabilize the permanent tooth against sideways breakage as it erupted. The researchers interpreted growth data for the saber-toothed cat to imply that the two teeth existed side by side for up to 30 months during the animal's adolescence, after which the baby tooth fell out.
In a new paper published in the journal The Anatomical Record, Tseng provides the first evidence that the saber tooth alone would have been increasingly vulnerable to lateral breakage during eruption, but that a baby or milk tooth alongside it would have made it much more stable.
The evidence consists of computer modeling of saber-tooth strength and stiffness against sideways bending, and actual testing and breaking of plastic models of saber teeth.
"This new study is a confirmation—a physical and simulation test—of an idea some collaborators and I published a couple of years ago: that the timing of the eruption of the sabers has been tweaked to allow a double-fang stage," said Tseng, who is a curator in the UC Museum of Paleontology.
A mechanical analysis of the distinctive canines of California's saber-toothed cat (Smilodon fatalis) suggests that the baby tooth that preceded each saber stayed in place for years to stabilize the growing permanent saber tooth, perhaps allowing adolescents to learn how to hunt without breaking them. Credit: Massimo Molinero
A portion of the right maxilla of a saber-toothed cat, Smilodon fatalis, showing a fully erupted baby saber tooth with the adult tooth just erupting. Based on Tseng's tooth eruption timing table, he estimates that the animal was between 12 and 19 months of age at the time of death. The fossil is from the La Brea Tar Pits and is housed at the Natural History Museum of Los Angeles County. Credit: Jack Tseng, UC Berkeley
A finite element model of an adult saber tooth indicating saber bending stress. The warmer the color, the higher the stress and the more likely failure will occur in a particular area of the tooth model. The red dot near the tip is where the force was applied to measure the sideways bending stress. Credit: Jack Tseng, UC Berkeley