At present, fairy armadillos have the least molecular data available within the armadillo family. This genus includes only 2 living species of fairy armadillo: "Chlamyphorus truncatus" (pink fairy armadillo) and "Chlamyphorus retusus" (chacoan or greater fairy armadillo). These two species are morphologically similar: both have notably reduced eyes and reinforced forearms that support enlarged digging claws. It is also one of few mammals that does not have external ears visible. Both species are specialized to subterranean lifestyle which was developed in their ancestral lineage sometime between 32 and 17 Mya. Both species have allopatric distributions; both are strictly nocturnal but the details of their ecology and population biology remain unknown. The similarities can be explained either by the presence of a shared common ancestry, which would prove the monophyly of both species, or by the result of adaptive convergence due to extreme selective pressures induced by their lifestyle (which would suggest the diphyletic origin). In 2012 the first theory was proven. The split between these two species was estimated to have occurred around 17 ± 3 Mya, around the transition between Early and Middle Miocene.