Glyptodonts, extinct shelled mammals, were long suspected to be cousins to modern-day armadillos. But new genetic analyses of a 14,000-year-old fossil from an Argentine museum reveal that these ancient herbivores (artist’s concept, above) weren’t the distant kin of today’s Texas roadkill. They actually were armadillos, albeit ones that could grow to the size of Volkswagen Beetles. The fossil, a shell fragment from a large individual of the genus Doedicurus, yielded enough genetic material to completely reconstruct DNA from the creature’s mitochondria, the tiny energy factories found in each living cell. When compared to previous genetic analyses from living armadillos, the new analysis put Doedicurus squarely within the armadillo family tree, not outside of it, the researchers report online today in Current Biology. The team’s analysis suggests that glyptodonts first evolved about 35 million years ago, when the last common ancestor of all glyptodonts and many of today’s armadillos—a species whose fossils are yet to be discovered—weighed in at about 6 kilograms. That’s about the size of an average nine-banded armadillo, but nowhere near the largest glyptodonts, which probably tipped the scales at a whopping 2 metric tons, the researchers say. By comparison, today’s armadillos range in size from the chipmunk-sized, 85-gram pink fairy armadillo to the 54-kilogram giant armadillo, which can be the size of a small pig. Unlike living armadillos, which can roll into a ball to protect themselves, the largest glyptodonts had fused carapaces and likely depended on their shells and clubbed tails, as well as their immense size, for self-defense.
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