Surprise! Ancient armadillos are related to modern armadillos

Charles Darwin returned from his travels aboard the Beagle in 1836 with several curious fossils from South America — including the preserved remains of what appeared to be a giant armored mammal. He thought the ancient animal, later dubbed a glyptodont, must have looked a lot like a supersized armadillo. DNA evidence published February 22 in Current Biology suggests that Darwin was right to make the connection.

Paleontologists have long suspected that extinct glyptodonts might be somehow related to modern armored mammals. To figure out exactly where glyptodonts fit on the family tree, researchers extracted fragments of DNA from the 12,000-year-old fossilized carapace of a Doedicurus specimen unearthed in the 19th century outside Buenos Aires. From those fragments, they reconstructed the animal’s mitochondrial genome and compared it to those of modern armadillo-like animals.

Glyptodonts’ closest modern relatives are fairy armadillos and giant armadillos. By the team’s calculations, the ancient group diverged about 35 million years ago from an ancestor that weighed a mere six kilograms, or about the size of a large pumpkin. Glyptodonts later ballooned in size to an estimated 2,000 kilograms — roughly the size of a car.