Résumé
Fairy armadillos or pichiciegos (Xenarthra, Dasypodidae) are among the
most elusive mammals. Due to their subterranean and nocturnal lifestyle,
their basic biology and evolutionary history remain virtually unknown. Two
distinct species with allopatric distributions are recognized:
Chlamyphorus truncatus is restricted to central Argentina, while
Calyptophractus retusus occurs in the Gran Chaco of Argentina, Paraguay,
and Bolivia. To test their monophyly and resolve their phylogenetic
affinities within armadillos, we obtained sequence data from modern and
museum specimens for two mitochondrial genes (12S RNA [MT-RNR1] and NADH
dehydrogenase 1 [MT-ND1]) and two nuclear exons (breast cancer 1 early
onset exon 11 [BRCA1] and von Willebrand factor exon 28 [VWF]).
Phylogenetic analyses provided a reference phylogeny and timescale for
living xenarthran genera. Our results reveal monophyletic pichiciegos as
members of a major armadillo subfamily (Chlamyphorinae). Their strictly
fossorial lifestyle probably evolved as a response to the Oligocene
aridification that occurred in South America after their divergence from
Tolypeutinae around 32 million years ago (Mya). The ancient divergence
date (∼17 Mya) for separation between the two species supports their
taxonomic classification into distinct genera. The synchronicity with
Middle Miocene marine incursions along the Paraná river basin suggests a
vicariant origin for pichiciegos by the disruption of their ancestral
range. Their phylogenetic distinctiveness and rarity in the wild argue in
favor of high conservation priority.