Nothing but the tooth

Teeth are probably one of the best parts of an animal. They are tough. They Hard. They can chomp down food. What’s more when the animal dies, they stand more of a chance of outlasting the brittle bones. They take longer to weather and break down. They are less of a treat to scavengers, as there is no nice juicy marrow within teeth. And this means that teeth have a greater chance of surviving to become a fossil. And teeth are good fossils. They are very diagnostic. Looking at a tooth shape we can see straight away if it is an omnivore, herbivore, or carnivore, and then with a little work, we can identify the actual species that tooth came from. For a palaeontologist finding a tooth is the jump up with joy moment. The tooth can tell a lot about the animal they have found and with that, the environment it lived in.

In fact, teeth are so diagnostic, that many new species have been named based on teeth alone. A new species of shark that once lived off the coast of Madagascar 40 million years ago was discovered by fossil teeth. One tooth led to the discovery of a new species of mammal relative that lived around 200 million years ago. There are lots more examples. It’s fair to say that palaeontologists get very excited about teeth.

The teeth of the giant extinct armadillo Macroeuphractus outesi have long been known to be very different from other armadillo species. They are sharp and thick, which mean they were strong. Strong enough to eat things other than insects, grasses and seeds. This armadillo was a meat eater.

The skull of Macroeuphractus showing the large sharp teeth. (Image Richard Lydekker Public Domain)

As always, taxonomy with extinct animals can get in a bit of a muddle, especially when there are not abundant fossils to work from. It has been placed in several different groups over time, but recent research shows it to be closely related to glyptodonts and pampatheres rather than other armadillos. Today armadillos eat a variety of foods, mostly insects and grubs, plants and fruit, and sometimes small mammals and lizards. The teeth of our giant carnivorous armadillo suggests it primarily ate meat, and research shows it had a strong, powerful bite. This is unique among all Xenartha (the Superorder which includes sloths and armadillos). Xenartha all sustain themselves on vegetation for the most part, and will supplement their diet with insects, eggs, small reptiles, and in some cases scavenging carcasses. No herbivore is a true vegetarian. 

It’s a very interesting branch on the Xenartha tree of life. Sometime around 9 million years ago, some armadillos found their niche in eating meat. South America was the origins of armadillos, and as a continent separated from other landmasses, life experimented with different adaptations. It is likely that they dug into the burrows of other animals for a nice warm lunch, as their bodies were not built for chasing prey. They were predators, but ambush predators, breaking into the homes of unsuspecting mammals and reptiles, and devouring the occupants.  

Around 3 million years ago, they disappear, just before the dawn of the Pleistocene. Climatic changes and cooling correlate to several South American animal extinctions. As the onset of the Pleistocene began, with its rapidly changing climates, temperatures were starting to cool, which affected vegetation and species which replied on it. Their disappearance is a short time before the joining of South America and North America, which caused numerous extinctions as new animals moved to explore and exploit new lands. With so few fossils found so far, and only in the Buenos Aires Province, I like to hope that new finds will show that this unique beast survived for a little longer.

Written by Jan Freedman

Further reading:

Alberdi, M. T., et al. (1992). ‘Paleoclimatic and paleobiological correlations by mammal faunas from Southern America and SW Europe.’ Proceedings of the 1st R.C.A.N.S. Congress, Lisboa, October, 1992. Pp. 143-149. [Full article]

Cenizo, M., Siobelzon, E., & Saffer, M., .M. (2015). ‘Mammalian predator-prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence.’ Historical Biology. [Full article]

Croft, D. A. (2017). ‘Horned armadillos and Rafting Monkeys: The fascinating fossil mammals of South America.’ Indiana University Press. [Book]

Serrano-Fochs, S., et al. (2015). ‘Finite element analysis of the Cingulata jaw: An ecomorpholigical approach to Armadillo’s diets.’ PLOS One. [Full article]  

Vizcaino, S. F., (2009). ‘The teeth of the ‘Toothless’: Novelties and key innovations in the evolution of Xanarthrans (Mammalia, Xenartha).’ Paleobiology. 35(3). pp.343-366. [Abstract only]

Vizcaino, S., F., & de Iuliis, G. (2003). ‘Evidence for advanced carnivory in fossil armadillos (Mammalia: Xenartha: Dasypodidae).’ Paleobiology. 29(1). pp123-138. [Full article]

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3 Responses to Nothing but the tooth

  1. kris michael says:

    You might find this article at Tet Zoo about carnivory in modern armadillos interesting. Surprising stuff, I knew armadillos will eat rotting meat if they find it but it seems that some species actively hunt.

  2. markgelbart says:

    Seems likely it was just a scavenger.

  3. Philip says:

    So something like a South American badger then?
    How fascinating, I’d never heard of this one.

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