Fossil Record
The presence of a carapace containing osteoderms is one of the very distinctive features of armadillos, and is true for fossil taxa as well. These elements are evident frequently in the paleontological record due to their resilience. Three distinct areas are recognized in these hardened plates. The outer and inner parts are made of thin, compact bone, while the middle zone is thicker and contains tissues for hair follicles and sweat glands. The presence of red bone marrow is rare in members of Chaetophractus, but widespread in Dasypus novemcinctus osteoderms. These findings propose an early split of both subfamilies and maintain the hypothesis that the Euphractinae are more derived than the Dasypodinae.
C. villosus earliest known fossils were found in the Pampean region, which suggests this is where the species originated. Fossil records then indicate the migration into Patagonia as the main dispersal route, which most likely occurred after the Pleistocenic glaciations. Using molecular dating, scientists estimated the first armadillos emerged around the Cretaceous/Tertiary boundary. This was followed by the divergence of anteaters and sloths in the Early Eocene era.
Read more about this topic: Big Hairy Armadillo
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