Born Big-Boned: Saber-toothed kittens may have been born with thicker bones than coexisting cats

Born Big-Boned: Saber-toothed kittens may have been born with thicker bones than coexisting cats

Saber-toothed cats (Smilodon fatalis) from the Pleistocene (37,000 to 9,000 years ago) are known to have had more robust skeletons compared to other wildcats. However, how and when saber-toothed cats developed these strong bones is a mystery.

To better understand the growth of Smilodon bones, Katherine Long from California State Polytechnic University and her colleagues measured and analyzed hundreds of bones at various stages of development from both Smilodon and the tiger-sized cat Panthera atrox, which existed at the same time. The bones are housed at the La Brea Tar Pits Museum.

The researchers found that while Smilodon bones were more robust than the Panthera bones, they did not increase in robustness with age as expected; instead, the cats were born with more robust bones to begin with. They found that the growth of Smilodon bones followed a similar pattern to other primitive cat species, where the bones actually grow longer and more slender more quickly than they grow thick. This finding suggests that feline growth and development is more similar between species than previously thought, even among species with very different bone structures.

“Saber-tooth cats had extraordinarily strong front limbs for tackling and subduing prey before they slashed their throats or bellies with their saber-like canine teeth,” says co-author Don Prothero. “Using the extraordinary collection of limb bones of saber-tooth kittens at La Brea Tar Pits, we found that their limbs don’t become more robust as they grew up, but instead retain the stereotypical growth pattern where the limbs grow longer more quickly than they grow thick. To compensate, saber-tooth kittens were born with unusually robust limbs and retained that pattern as they grew.”

Growth series of juvenile limb bones of Smilodon fatalis, showing the dramatic transformation of size and shape as a cat ages.

Growth series of juvenile limb bones of Smilodon fatalis, showing the dramatic transformation of size and shape as a cat ages.

Reference:  Long K, Prothero D, Madan M, Syverson VJP (2017) Did saber-tooth kittens grow up musclebound? A study of postnatal limb bone allometry in felids from the Pleistocene of Rancho La Brea. PLoS ONE 12(9): e0183175. https://doi.org/10.1371/journal.pone.0183175

Image Credit: James St. John, Flickr; Long et al (2017)

Author

Tessa is the Journal Media Manager at PLOS. She graduated from the University of California, Berkeley with degrees in Rhetoric and Music. She can be reached by email at tgregory@plos.org and on Twitter at @tessagregs.

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