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What was a South American herbivore doing with saber teeth?

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saber-toothed herbivore from south americaSome extinct animals have anatomical oddities that seem destined to be confined to the marginalia of history. Questionable characters, such as the single-fingered dinosaur and the flightless, club-winged bird, ultimately died off despite—if not because of—their idiosyncratic adaptations.

Now, researchers have described a perplexing, long-extinct creature, this time with some dubious dental assets: large saber teeth. A seemingly strange adaptation for a plant eater.

This Middle Permian creature exhibits what Jörg Fröbisch, of the Humboldt Museum in Berlin, kindly describes as "a unique dentition."

The aptly named Tiarajudens eccentricus (Tiaraju for its location, "dens" for teeth—and eccentricus, well, you can gather that bit) was a dog-sized animal that lived some 260 million years ago in what is now Brazil.

"Large saber canine [teeth] are unexpected in a herbivore," wrote the authors of the study that describes the new anomodont, a member of the therapsid group (which produced some lines that eventually led to mammals).

extinct saber-toothed animal found in brazilAnd these fangs weren’t subtle. The saber teeth were more than half the length of the animal’s 22.5-centimeter-long skull—proportionally bigger even than those of a carnivorous contemporary, the Inostrancevia.

Among four-legged animals, a plant-based diet had only emerged some 40 million years earlier, but the sizable teeth do not appear to be a holdover from carnivorous ancestors.

So if it wasn’t tearing meat like a saber-tooth tiger, what was it doing with these two outsized teeth? "The function of the saber teeth is unknown," wrote authors of the new study. But they might have used them to scare away predators, fight among each other or show off for potential mates—or perhaps all three.

Saber teeth are not totally unknown in the herbivore world. There are a few living deer, such as the water deer Hydropotes and musk deer Moschus, that have protruding teeth. But before this little anomodont was uncovered, the earliest known example was the Titanoides, which didn’t emerge until 57 million years ago.

These saber teeth are not, apparently, to be confused with the tusks simultaneously sprouting from a sister anomodont group, the dicynodonts.

skull saber tooth anomodontWith this distinction, Fröbisch poses an existential question—for T. eccentricus, at least: "When is a saber tooth a saber tooth, and when is it a tusk or simply an enlarged canine?"

The answer, actually, still seems unclear and, he notes, "appears to be vague and primarily based on length." But perhaps it will be worth chewing over, as he points out that it should help explain a bit about the evolution of herbivores and their "complex social interactions"—or lack thereof.
The study, led by Juan Carlos Cisneros, of the Universidade Federal do Piauí in Teresina, Brazil, and accompanying essay by Fröbisch were published in the March 25 issue of Science.

Images of T. eccentricus courtesy of Juan Cisneros

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  1. 1. BlakeJustBlake 12:34 pm 03/25/2011

    Apparently the water deer that are current day omnivores with these sorts of tusks have muscles that allow them to move them out of the way when eating and flare them out when threatened. I wonder if anything can be told about their facial muscles from the fossils to see if they have some sort of similar functions.

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  2. 2. Lowndes 12:56 pm 03/25/2011

    The reason has to be very similar to the reason cows have horns and moose have antlers: weapons, mating strategies, possibly tools for finding/eating particular foods. Walrus have big teeth they use to haul out onto ice and fight. What’s the big deal??

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  3. 3. Jennifer 12:43 am 03/26/2011

    Walruses have similar tusks which they use for many purposes, including raking clams from the sea bed. Perhaps these creatures used their tusks for digging and grubbing up roots and tubers.

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  4. 4. jtdwyer 10:25 am 03/26/2011

    I guess you get the prize for mentioning tusks – I was looking for some mention of elephants and their tusks, but found none but yours.

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  5. 5. Lowndes 2:31 pm 03/26/2011

    jt, Salutations.

    Tusks~teeth, check the response just before Jennifer’s.


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  6. 6. Lowndes 3:01 pm 03/26/2011

    Jennifer, I thought about digging but these teeth/tusks would not be useful for that being pointed almost straight down. To be used at this angle, the animal would have to lay down on the ground. If these teeth were forward (as in elephants), they could be used for digging. The walrus has his head in that position when he is trying to haul out. The naked mole rat has forward pointing teeth (actually outside the mouth) they use for digging and they are almost laying on the "ground" to begin with.

    These teeth were most likely used for defense (wild hogs), mating strategy, and in a social group, for dominance, similar to cows at a feed trough – the cow with the longest horns will rake the neighbors to claim the biggest share (most space) at the trough. Larger teeth are an easier change than horns or antlers, but accomplish the same uses.

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  7. 7. jtdwyer 5:52 pm 03/26/2011

    Thanks – well done!

    Sorry I missed your comment.

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