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The Giant Armadillo (Priodontes maximus)

We boldly continue armor week with an overview of the magnificent armadillo family.  This order of armored mammals (Cingulata) is more diverse than any other sort of armored mammals–outshining even the scaled pangolins. Today the only living members of the Cingulata order are the armadillo family (a successful group consisting of more than 20 living species) but the armadillos’ extinct cousins were once far more widespread and bizarre.  These relatives included the pampatheres–long plantigrade browsing creatures covered in banded armor who roamed the continent from one end to the other.  Even more impressive were the glyptodonts, massive tank-like creatures bigger than a compact car.

A fossil glyptodon, fossil pamphathere, and armadillo skeleton (in the far right corner)

The Cingulata order is part of the superorder Xenarthra. Separated from all other placental mammals for over 100 million years (due to South America’s unique isolation after the breakup of the southern supercontinent Gondwana), xenarthrans evolved in different directions from other mammals. The unique challenges and opportunities of their island continent resulted in bony domed giants like the pampatheres and glyptodonts, both of which are characterized by tortoise-like body armor composed of bone segments (osteoderms).  The glyptodonts were unlike tortoises in that they could not draw their head beneath their shells: instead their heads were protected by bony caps atop their skulls. The largest glyptodonts could grow to 4 metres long, 1.5 metres high and have a mass of 3 tons (Ferrebeekeeper has already written about the smallest known Cingulata species—the pink fairy armadillo, which can still be found living in the central dry lands of Argentina).

Glyptodon

Thanks to convergent evolution the herbivorous glyptodonts resembled other armored giants like cryptodire turtles and ankylosaurs.  One species of glyptodont, Doedicurus clavicaudatus, even had a heavy spiked tail (although it is unclear whether this was used against predators or to compete for territory and mates).

Doedicurus clavicaudatus

When the first members of the Cingulata order emerged in the Myocene, the top predators of South America were giant running predatory birds–the Phorusrhacidae, which resembled giant dashing eagles up to 3.2 metres (10 ft) high.  The glyptodonts, pampatheres, and armadillos outlasted these terror birds and they then outlasted the carnivorous metatherian mammals (with terrible saber teeth) which followed.  When the Isthmus of Panama connected South America with North America (and therefore with an entirely new universe of ultra-competitive mammals), the armored cingulatans competed just fine with the newcomers.  Some glyptodonts and pamphatheres wandered up through Central America and found new homes in North America.  The armadillos are still there.  However at the end of the last ice-age, a new African species arrived and brought a devastating and final end to the glyptodonts, the pampatheres, and most of the armadillos. But even this newly arrived predator seemed impressed by the greatest of armored mammals.  An Argentine anthropologist even reports discovering a site twenty leagues from Buenos Aires where early human hunters had used glyptodont shells as dwelling places.

Human Hunters Stalk a Glyptodon (Heinrich Harder)

Ah summer…the perfect time for a delicious guacamole quesadilla or a tasty avocado salad.  But have you ever looked inside an avocado?  Beneath the delicious green flesh is an immense hard seed as big as a golf ball.  Trees compete by spreading seeds efficiently.  The Norway maple in my back yard produces thousands of helicopter seeds which fly off in every direction on their own rotors. The black cherry entices countless birds to eat its fruit, pit and all, and thereby spread its seeds afar on feathered wings.  What purpose does the avocado’s giant seed serve?

Gomphotheres--can you imagine these guys running around Texas?

Well, avocado trees as a species are ancient.  They evolved together with giant mammals like glyptodons, gomphotheres, and giant sloths.  These immense herbivores could eat avocados whole and not even notice the seeds. The animals would forage away from the original tree and, in the course of time, leave the seed in a totally different location along with a pile of fertilizer.  Osage oranges are similarly symbiotic with the giant extinct grazers.  In the absence of these creatures, wild avocados and Osage oranges are slowly losing ground to other trees–even if human kind has planted the avocado for food and the Osage orange for its springy wood (which is perfect for archery).

Giant Sloth

So what happened to all these wonderful beasties?  Why is a nature documentary shot on the grasslands of Africa today so much more satisfying then one from the great Texas Llano?  Alas, they went extinct 12000 to 14000 years ago—just about the same time humankind showed up. It turns out the first humans to get to the New World loved killing charismatic megafauna even more than Buffalo Bill did.

Early Americans stalk a glyptodon.

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