Necrolestes

Necrolestes ("grave robber" or "thief of the dead") is an extinct genus of non-therian mammals, which lived during the Early Miocene in what is now Argentine Patagonia. It contains two species, N. patagonensis and N. mirabilis, and is the most recent known genus of dryolestoid. The type species N. patagonensis was named by Florentino Ameghino in 1891 based on remains found by his brother, Carlos Ameghino in Patagonia. Fossils of Necrolestes have been found in the Sarmiento and Santa Cruz Formations.

Description
About one-third of the skeleton of N. patagonensis—including most of the skull— has been found as disassociated bones of several individuals. The jaw bends up at the tip, possibly supporting a fleshy appendage similar to the sensitive tentacles of the star-nosed mole. Necrolestes is also sometimes reconstructed as a mole-like creature. It probably fed on insects or worms.

Classification
Its classification is not firmly resolved due to it being highly apomorphic and having an anatomy unlike any other known mammal, living or extinct. It was thought to be a therian mammal; placement within either the marsupial lineage (Metatheria) or as a member of Eutheria would have been possible given that South America as an island had extensive lineages of both marsupial and placental mammals. However, phylogenetic analyses conducted by Rougier et al. (2012), Chimento, Agnolin and Novas (2012) and Averianov, Martin and Lopatin (2013) recovered Necrolestes in an unexpected phylogenetic position as a nontherian mammal that belonged to the clade Meridiolestida;[4][5][6] if confirmed this would make Necrolestes the youngest known member of the group. Within Meridiolestida, Rougier et al. (2012) found Necrolestes to be particularly closely related to the genera Cronopio and Leonardus;[4] Chimento et al. (2012) found it to be in unresolved polytomy with Cronopio, Leonardus and the clade containing all other meridiolestidans[5] while Averianov et al. (2013) recovered Cronopio, Necrolestes and Leonardus as forming a grade at the base of Meridiolestida rather than a clade.[6]

Meridiolestidans themselves were initially classified as member of the clade Dryolestida;[7] this result was confirmed by the analysis of Chimento et al. (2012),[5] while Rougier et al. (2012) recovered them as slightly more closely related to the placental mammals, marsupials and amphitheriids than the members of Dryolestida were,[4] and Averianov, Martin and Lopatin (2013) recovered meridiolestidans as the sister group of spalacotheriid "symmetrodonts".[6] However, various subsequent studies have consistently shown a dryolestoid identity for meridiolestidans.

Phylogeny
This cladogram follows the paper of Rougier, Wible, Beck and Apesteguía of 2012: