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Dagger-like saber-toothed cat canines took years to grow

New technique suggests rapid canine growth, but delayed dental maturity in saber-toothed cats

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This partial fossilized jaw is from a baby Smilodon fatalis. At the time of the cat's death, one of its adult canines (inside, top) was erupting alongside the baby canine... view more

Credit: Courtesy of Wysocki, Feranec, Tseng, and Bjornsson

The fearsome saber-toothed cat teeth may have fully emerged later in life than those of modern big cats, but they grew at a rate about double that of their living relatives, according to a study published July 1, 2015 in the open-access journal PLOS ONE by Aleksander Wysocki from Clemson University, and colleagues.

The saber-toothed cat lived in North and South America until going extinct about 10,000 years ago. The cats are famous for their protruding canines, which could grow to be about 7 inches long. Although well-preserved fossils are available to researchers, very little is known about the ages at which the animals reached key developmental stages.

Using saber-toothed cat specimens recovered from the La Brea Tar Pits in Los Angeles, the authors of the study combined data from stable oxygen isotope analyses, micro-computed tomography, and previously published studies to establish the eruption rate for the saber-toothed cat's permanent upper canines and to calculate the timing of other growth events.

The authors of the study estimate that the permanent dentition of saber-toothed cats was fully erupted by 14 to 22 months, with the exception of the upper canines. These weren't fully developed until about three years of age, which is delayed in comparison to similar-sized living members of the cat family. The eruption rate of the saber-toothed cat's permanent upper canines was 6 millimeters per month -- double the growth rate of an African lion's teeth.

The researchers suggest that the technique used in the study could be applied to a variety of extinct species to better understand the manner and rate by which different animals grew, for example, by looking at the tusks of extinct elephants or marine mammals.

"Despite having canine crown heights that were more than twice those of the lion, it didn't require twice as much time to develop its canines," added lead author Aleksander Wysocki.

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Adapted by PLOS ONE from release provided by the author.

URL to the freely available paper: http://dx.plos.org/10.1371/journal.pone.0129847

Citation: Wysocki MA, Feranec RS, Tseng ZJ, Bjornsson CS (2015) Using a Novel Absolute Ontogenetic Age Determination Technique to Calculate the Timing of Tooth Eruption in the Saber-Toothed Cat, Smilodon fatalis. PLoS ONE 10(7): e0129847. doi:10.1371/journal.pone.0129847

Funding: Funding for this study was provided by the Society of Vertebrate Paleontology, U.C. Berkeley Department of Integrative Biology, American Museum of Natural History's Theodore Roosevelt Grant, and an NSF DDIG to RSF. ZJT is supported by NSF DEB-1257572 and a Frick postdoctoral fellowship from the American Museum of Natural History. Logistical support was provided by the NY State Museum. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

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