If you’ve read recent articles here, you’ll have seen the coverage I’ve been giving to armadillos…
Caption: a euphractine montage… though read on for ideas about what ‘euphractine’ does or does not mean. At left, skeleton of a hairy armadillo (Chaetophractus). At right, a Six-banded armadillo Euphractus sexcinctus demonstrating how easy it is for armadillos of this sort to stand bipedally. This one was photographed at Edinburgh Zoo in 2010. Images: Darren Naish.
As usual, my initial plan wasn’t to embark on some grand tour of total armadillo diversity but, rather, to cover select facts about the group, my primary aim being to discuss where glyptodonts – the mostly enormous, entirely extinct, primarily herbivorous armadillos of the American fossil record – fit within the armadillo radiation. Follow me as I cover more of armadillo diversity, all the while aiming to get in the end to the glyptodonts and what they are…
We saw in the previous article that armadillos are today considered to consist of two primary clades, namely long-nosed armadillos (Dasypodidae) and all the others (Chlamyphoridae). Current thinking, based mostly on molecular phylogenetics (read on), has it that Chlamyphoridae consists of euphractine armadillos, fairy armadillos, and tolypeutine armadillos (Delsuc et al. 2003, Gibb et al. 2016, Barasoain et al. 2020). I must add – without getting bogged down in a discussion of armadillo taxonomic history – that armadillo specialists have historically preferred to include all armadillos within a lone family (Dasypodidae), and to recognise within it two subfamilies, Dasypodinae and Euphractinae. This was still being used as of 2024 (e.g., Carlini et al. 2009, Klimeck et al. 2024). In the taxonomic system where non-dasypodid armadillos are united within Chlamyphoridae, rather than Euphractinae, the term ‘euphractine’ is used for the Euphractes lineage alone, not for the whole of the non-dasypodid clade. Gaudin & Wible (2006) used the name Euphracta for the Euphractes clade.
Caption: a very simplified cladogram depicting the relationships of some of the animals discussed here. Eutatines, the living six-banded, hairy armadillos and kin, and Macroeuphractus and similar forms are conventionally allied within Euphractinae. However, some of these animals appear to be closer to the pampathere + glyptodont clade than others. Images: three-banded armadillo in the public domain (original here); Eutatus from Krmpotic et al. (2009); Macroeuphractus from Vizcaíno & De Iuliis (2003); Euphractus, pampathere and glyptodont by Darren Naish.
With this taxonomic framework in mind… we looked previously at one of the euphractines, the Pichi Zaedyus pichiy of southern South America. It’s now time to look at remaining euphractines, and to start getting through remaining chlamyphorids in general. As we’ll see (in the next article), this ‘two family’ taxonomy is a bit problematic, and I think it should be revised.
Remaining euphractines. Ok, with the Pichi out of the way, the other extant euphractines are the Six-banded armadillo Euphractus sexcinctus and the hairy armadillos (Chaetophractus). All (including the Pichi) are robust ecological generalists that eat just about anything, are good diggers and burrowers, and occur mostly in grasslands and semi-deserts. They vary in their degree of hairiness – as you might guess, the several Chaetophractus species are the hairiest – and all have pointed ears, a head that’s subtriangular when seen from above, and a slender, fully armoured tail.
Caption: six-banded and hairy armadillos are omnivore-carnivores that eat carrion, arthropods of all sorts, and also catch and kill vertebrates, sometimes of surprising size. For more on this issue see the 2020 article Predation and Corpse-Eating in Armadillos. Images: original video that yielded screengrab no longer online; Darren Naish.
Current convention is to regard all three of the lineages here as distinct genera, but they’re sufficiently alike that some authors have combined all of them in one genus (Euphractus Wagler, 1830 wins out). At least some molecular studies suggest that the Pichi might be nested within Chaetophractus, rather than be its sister-taxon (Delsuc et al. 2016). I was interested to learn (thanks to David Howlett in the comments of the previous Tet Zoo armadillo article) that supposed Pichi specimens kept in captivity have sometimes turned out to be misidentified Screaming hairy armadillos C. vellerosus, which goes to show that even people with hands-on experience of live armadillos can confuse Zaedyus with the Chaetophractus species.
Fossil euphractines in name only, perhaps. A substantial number of fossil taxa have been regarded as euphractines. The oldest of these date to the Eocene or Early Oligocene (like Isutaetus, Parutaetus, Meteutatus and Anutaetus), a few others are from younger parts of the Oligocene (Hemiutaetus, Amblytatus and others), and others are Miocene and/or Pliocene (Vetelia, Proeuphractus, Paleuphractus and so on).
Caption: Early Oligocene armadillos from the Tinguiririca Fauna of Chile, both of which would conventionally have been included within the inclusive version of Euphractinae. At left, Meteutatus tinguiririquensis; at right, Parutaetus chilensis. This very nice illustration is from Carlini et al. (2009): no artist is credited for this illustration in the paper (unless I’ve missed it), so I assume it’s one of the authors.
These taxa are all very obscure, at least some were named for osteoderms alone, and they’re hardly ever discussed outside of the technical literature except for the very large Macroeuphractus of Pliocene Argentina. I previously covered this very interesting animal in this 2020 article devoted to carrion-eating and predation in armadillos. Macroeuphractus and a few similar taxa are sufficiently well represented in anatomical terms to win inclusion in phylogenetic studies (Gaudin & Wible 2006, Herrera et al. 2017), and results mostly indicate that they’re likely not euphractines after all, by which I mean that they’re not close relatives of Euphractus and its extant kin. Paleuphractus, Proeuphractus and Macroeuphractus were all found by Gaudin & Wible (2006) to be close to the pampathere + glyptodont clade, the main characters responsible for this position being a proportionally short snout and the detailed anatomy of the ectotympanic bulla (the bulging bony region that forms the underside of the ear region). Barasoain et al. (2021), in contrast, did find certain of these taxa to be close to Euphractus and kin.
Caption: a Macroeuphractus montage, based on the work of Vizcaíno & De Iuliis (2003). At left, the big, robust and heavily built skull of this animal (the scale bar is probably 100 mm: the paper accidentally fails to provide its length), as illustrated by Richard Lydekker in 1894. At right, speculative art provided by Vizcaíno & De Iuliis (2003) and showing Macroeuphractus about to break into a burrow inhabited by the chinchillid rodent Lagostomus. This will not end well for the rodents.
If these fossil, Euphractus-like taxa are not close relatives of Euphractus after all, it means that the features conventionally used to unite ‘euphractines’ are widespread within this section of the armadillo family tree. This wouldn’t affect the monophyly of euphractines proper. It would also mean that a series of taxa – these ‘former euphractines’, the pampatheres, and other taxa too – form a series of intermediates between glyptodonts and extant armadillos.
Eutatines and others. If it’s not already obvious, numerous fossil armadillos are known. A number are grouped together as the eutatines – yes, a word annoyingly similar to euphractines – after the relatively well-represented Eutatus of the Pliocene, Pleistocene and Holocene of Argentina, several species of which are known. Making things additionally complex is the fact that eutatines are considered within euphractines in those taxonomic systems where Euphractinae is used in the old, inclusive sense (so, certain fossil ‘euphractines’ listed above – like Meteutatus of the Eocene – are also eutatines). Eutatus was large, with a skull 26 cm long. This suggests an overall size about similar to the living Giant armadillo Priodontes maximus or maybe bigger.
Caption: Eutatus is known from very good specimens, some of which have the bulk of their armour preserved in full articulation. This skeleton of Eutatus punctatus is on show at Museu de Ciències Naturals de València, Spain. Image: Joanbanjo, CC BY-SA 3.0 (original here).
Caption: ok, so a lot of fossil armadillos are known from isolated osteoderms alone. It figures that these tough, super numerous bones have high preservation potential and thus might be over-represented in the fossil record relative to other parts of the skeleton. However, there are also quite a few fossil armadillos that are extremely well preserved, with mostly intact armour. Obviously, much of the armour on this Eutatus specimen is reconstructed, but at least some of it is articulated. Note the long, triangular form of the head shield. Again, this is E. punctatus on show at Museu de Ciències Naturals de València, Spain. Image: Joanbanjo, CC BY-SA 3.0 (original here).
Eutatus was long-snouted, with a relatively slender lower jaw and toothless premaxilla. Its teeth have flattened crowns that are elliptical in cross-section and the jaw joint resembles that of ruminants.
All of these features indicate that Eutatus was a high-fibre herbivore, presumably eating leaves, buds and maybe grasses too (Vizcaíno & Bargo 1998). A few older armadillos conventionally classified alongside Eutatus within Eutatini – they include Proeutatus and Stenotatus of the Miocene, and Doellotatus and Ringueletia of the Pliocene – are superficially similar to Eutatus but smaller and with less prominent muscle insertion points on the jaw and cranium, so they might have been omnivorous and perhaps intermediate in ecology between armadillos like Euphractus and the strongly herbivorous Eutatus (Vizcaíno & Bargo 1998).
Caption: a eutatine/eutatin montage drawing on images compiled by Vizcaíno & Bargo (1998), and with the caveat that these animals don’t group together in current phylogenetic analyses. Eutatus is obviously bigger, long-snouted and longer-jawed than the others shown here, and with a longer toothless section at the front of the upper and lower jaws.
Variation in osteoderm anatomy present across the Eutatus species indicates variation in terms of how hairy they were, and also in how adapted they were for aridity and low or high temperature (Krmpotic et al. 2009). Yes, you can make inferences about that sort of thing from osteoderm anatomy. It’s a subject I can’t do justice here but will in another article.
If you know anything about fossil armadillos, you might be thinking from the description of Eutatus given above that it sounds superficially like a pampathere, these being a group of even larger, fully herbivorous extinct armadillos (indisputable species of which are known from the Miocene to the Holocene, and from North America as well as South America). Pampatheres have often been considered close to glyptodonts.
Caption: pampatheres (like Holmesina, here on the left) and glyptodonts (like Glyptodon, on the right) are going to be discussed a bit more in the next armadillo-themed article. The fact that both groups are nested within armadillos is now well known and today we’re in the habit of giving credit to molecular researchers for discovering this, but… nope, people working on anatomy discovered this first! That’s a non-trivial point that I’ll be bigging up in the next article. This photo was taken at the Royal Ontario Museum, Toronto. Image: Darren Naish.
Engelmann (1978, 1985) suggested that all three groups (eutatines or eutatins, pampatheres, glyptodonts) formed a clade, with eutatins being closer to glyptodonts than pampatheres. However, Gaudin & Wible (2006), Billet et al. (2011) and Herrera et al. (2017) all found so-called eutatins to be non-monophyletic: as previously noted by Vizcaíno & Bargo (1998), it turns out that Proeutatus shares unusual anatomical details with pampatheres and glyptodonts (including teeth where the crowns are worn flat and have a resistant orthodentine core), whereas Eutatus itself does not (Gaudin & Wible 2006, Billet et al. 2011). In fact, the distribution of anatomical features means that Eutatus is outside the clade that unites euphractines (in the strict, restrictive sense) with pampatheres and glyptodonts. That’s bad news if you’re a eutatin superfan, but not for everyone else because what this means is that armadillos gave rise to big-bodied, specialized herbivores at least twice.
Ok, I need to stop there… to be continued…
For previous Tet Zoo articles on armadillos and othr xenarthrans, see…
Five things you didn’t know about armadillos, June 2007
What was that skull? (on glyptodonts), May 2008
I, Priodontes, the tatuasu, September 2008
Predation and Corpse-Eating in Armadillos, September 2010
The Fate of the Woolly Long-Nosed Armadillo of Peru, April 2024
Of Zaedyus, the Pichi, May 2025
Refs - -
Barasoain, D., Contreras, V. H., Tomassini, R. L. & Zurita, A. E. 2020. A new pygmy armadillo (Cingulata, Euphractinae) from the late Miocene of Andean Argentina reveals an unexpected evolutionary history of the singular Prozaedyus lineage. Journal of South American Earth Sciences 100, 102589.
Barasoain, D., González Ruiz, L. R., Tomassini, R. L., Zurita, A. E., Contreras, V. H. & Montalvo, C. I. 2021. First phylogenetic analysis of the Miocene armadillo Vetelia reveals novel affinities with Tolypeutinae. Acta Palaeontologica Polonica 66, S31-S46.
Billet, G., Hautier, L., de Muizon, C. & Valentin, X. 2011. Oldest cingulate skulls provide congruence between morphological and molecular scenarios of armadillo evolution. Proceedings of the Royal Society B 278, 2791-2797.
Carlini, A. A., Ciancio, M. R., Flynn, J. J., Scillato-Yané, G. J. & Wyss, A. R. 2009. The phylogenetic and biostratigraphic significance of new armadillos (Mammalia, Xenarthra, Dasypodidae, Euphractinae) from the Tinguirirican (Early Oligocene) of Chile. Journal of Systematic Palaeontology 7, 489-503.
Delsuc, F., Gibb, G. C., Kuch, M., Billet, G., Hautier, L., Southon, J., Rouillard, J.-M., Fernicola, J. C., Vizcaíno, S. F., MacPhee, R. D. E. & Poinar, H. N. 2016. The phylogenetic affinities of the extinct glyptodonts. Current Biology 26, R155-R156.
Delsuc, F., Stanhope, M. J. & Douzery, E. J. P. 2003. Molecular systematics of armadillos (Xenarthra, Dasypodidae): contribution of maximum likelihood and Bayesian analyses of mitochondrial and nuclear genes. Molecular Phylogenetics and Evolution 28, 261-275.
Engelmann, G. 1978. The Logic of Phylogenetic Analysis and the Phylogeny of the Xenarthra. Ph.D. dissertation, Columbia University, New York.
Engelmann, G.1985. The phylogeny of the Xenarthra. In Montgomery, G. G. (ed) The Ecology and Evolution of Armadillos, Sloths, and Vermilinguas. Smithsonian Institution Press, Washington, DC, pp. 51-64.
Gaudin, T. J. & Wible, J. R. 2006. The phylogeny of living and extinct armadillos (Mammalia, Xenarthra, Cingulata): a craniodental analysis. In Carrano, M. T., Gaudin, T. J., Blob, R. W. & Wible, J. R. (eds) Amniote Paleobiology: Perspectives on the Evolution of Mammals, Birds, and Reptiles. University of Chicago Press, pp. 153-198.
Herrera, C. M. R., Powell, J. E., Esteban, G. I. & del Papa, C. 2017. A new Eocene dasypodid with caniniforms (Mammalia, Xenarthra, Cingulata) from northwest Argentina. Journal of Mammalian Evolution 24, 275-288.
Klimeck, T. D. F., Ciancio, M. R., Sedor, F. A. & Kerber, L. 2024. Revealing the diversity of Paleogene cingulates from Brazil: a new species of Parutaetus (Euphractinae) in the Guabirotuba Formation (middle-late Eocene). Journal of Vertebrate Paleontology e2403581.
Krmpotic, C. M., Carlini, A. A. & Scillato-Yané, G. J. 2009. The species of Eutatus (Mammalia, Xenarthra): assessment, morphology and climate. Quaternary International 210, 66-75.
Vizcaíno, S. F. & Bargo, M. S. 1998. The masticatory apparatus of the armadillo Eutatus (Mammalia, Cingulata) and some allied genera: paleobiology and evolution. Paleobiology 24, 371-383.
Vizcaíno, S. F. & De Iuliis, G. 2003. Evidence for advanced carnivory in fossil armadillos (Mammalia: Xenarthra: Dasypodidae). Paleobiology 29, 123-138.
