Thousands of years ago, giant armor-plated beasts known as glyptodonts roamed South America. Often referred to as "giant armadillos," these creatures grew to be the size of a small car. However, it turns out their nickname wasn't too far off. A new study from McMaster University, Canada, confirms the creatures were in fact very closely related to modern armadillos.

The glyptodont family includes one Doedicurus, which was the largest-known species in the family, growing over 13 feet long and weighing about 1.5 tons. It also boasted a fearsome spiked tail resembling a medieval mace, which was likely used in combat. The animals are commonly called "giant armadillos," but only recently have scientists concluded they really were ancient cousins of modern roly poly animals. 

"Glyptodonts in fact represent an extinct lineage that likely originated about 35 million years ago within the armadillo radiation," Hendrik Poinar, of McMaster University, said in a news release. 

"Glyptodonts should probably be considered a subfamily of gigantic armadillos," Frédéric Delsuc, one of the study researchers from the National Center for Scientific Research (CNRS) in France, added. "We speculate that the peculiar structure of their unarticulated carapace might have evolved as a response to the functional constraint imposed by the size increase they experienced over time."

For their study, researchers analyzed the genome of Doedicurus. Unlike modern armadillos, the ancient animals had rigid shells that were made from one solid piece, rather than the layered, flexible bands that allow their modern cousins to curl up into a ball. 

The last Doedicurus died about 11,000 years ago, and the tiny fossil sample analyzed for the study was about 12,000 years old. 

"Ancient DNA has the potential to solve a number of questions such as phylogenetic position--or the evolutionary relationship--of extinct mammals, but it is often extremely difficult to obtain usable DNA from fossil specimens," Poinar explained. "In this particular case, we used a technical trick to fish out DNA fragments and reconstruct the mitochondrial genome."

Based on their genetic analysis, researchers confirm Glyptodonts are a distinct subfamily in the family Chlamyphoridae, which includes the pink fairy armadillo -- the smallest species of armadillo known to exist today. 

Glyptodonts are thought to have evolved from an extinct armadillo lineage about 35 million years ago, which is about 30 million years before modern armadillos evolved. The massive creatures lived alongside early modern humans, who may have hunted them, and vanished at the end of the last ice age about 10,000 years ago, like most other megafauna. 

Furthermore, researchers estimate the animals' 35 million-year-old ancestor would have only been 13 pounds, suggesting Glyptodonts saw a tremendous increase in size as they evolved. Their study was recently published in the journal Current Biology. 

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