Listen to Episode 153 on PodBean, YouTube, Spotify, or wherever you listen to your favorite podcasts!
Body armor is a rarity among mammals, and yet this particular group has made it work in modest modern species and gigantic ancient ones. This episode, we discuss the past and present of Armadillos.
In the news
Possible links between marine extinctions and the rise of land plants
Croc-like reptiles offer clues to the evolution of archosaurs
Once-heated fish teeth might be the oldest evidence of cooking
New Cretaceous species is Europe’s largest known sea turtle
Armored Mammals
Armadillos are strange and fascinating mammals. They belong to a group called Xenarthra, whose other members – sloths and anteaters – are also strange and fascinating. Armadillos share their cousins’ simple teeth and powerful clawed forelimbs, and they are set apart by their most famous feature: the multi-sectioned armor that covers most of their bodies. This armor is made up of many tiny osteoderms (skin bones, as also seen in crocodilians, turtles, ankylosaurs, and more) that cover parts of their head, back, and tail.
Top right: Pink fairy armadillo. Image by Cliff, CC BY 2.0
Bottom left: Giant armadillo. Image by Mamíferos de Colombia, CC BY-NC 2.0
Bottom right: Three-banded armadillo. Image by Ltshears, CC BY-SA 3.0
Top: Nine-banded armadillo skeleton. Image by Ellenm1, CC BY-NC 2.0
Bottom: Seven-banded armadillo skull. Image by Lukas Large, CC BY-SA 2.0
Left image by Sandstein, CC BY 3.0. Right image by Polyoutis, CC BY-SA 4.0
The lineage of mammals that includes armadillos – the Cingulata – has been around for at least 60 million years or so, and for most of that time, they were restricted to the isolated continent of South America, along with the other xenarthrans. The fossil record of Cingulata includes numerous well-preserved skulls and skeletons, as well as lots of fossilized osteoderms. Ancient armadillos were quite diverse, including a variety of familiar-looking forms as well as oddities like the strange horned armadillos and the gigantic igloo-shaped glyptodonts.
Left: Art of Peltephilus by Apokryltaros, CC BY-SA 3.0
Right: Sketch of Peltephilus skull from Internet Archive Book Images
Perhaps the most famous ancient armadillos are pampatheres and glyptodonts. Pampatheres had segmented armor like modern armadillos, while glyptodonts tended to have a single turtle-like shell of armor and sometimes spiky tail weapons. Both groups existed for tens of millions of years right up to the end of the Ice Age, both were groups of armored herbivores, and both grew quite large – the largest pampatheres would have weighed hundreds of kilograms, while the very largest glyptodonts were the size and weight of cars.
Bottom: The Pleistocene glyptodont Glyptodon. Image by Arent, CC BY-SA 3.0
Around three million years ago, a new connection between South and North America led to the Great American Biotic Interchange, during which many groups dispersed across the two previously-separated continents. After tens of millions of years of isolation, this event allowed armadillos to move into North America for the first time. For a few million years during the Ice Age of the Pleistocene Epoch, North America was home to its very own glyptodonts and pampatheres. Sadly, the big species vanished at the end of the Pleistocene, but modern armadillos persist in both South and North America.
Learn More
Remarkable Creatures (ancient giant armadillos), Twilight Beasts
The giant armadillos of the Americas
The Xenarthrans: Armadillos, Glyptodonts, Anteaters, and Sloths (technical, paywall)
—
If you enjoyed this topic and want more like it, check out these related episodes:
- Episode 24 – Sloths
- Episode 25 – The Pleistocene Megafaunal Extinction
- Episode 43 – The Great American Biotic Interchange (GABI)
- Episode 74 – South America
We also invite you to follow us on Twitter, Facebook, or Instagram, buy merch at our Zazzle store, join our Discord server, or consider supporting us with a one-time PayPal donation or on Patreon to get bonus recordings and other goodies!
Please feel free to contact us with comments, questions, or topic suggestions, and to rate and review us on iTunes
COMMON DESCENT 