| Necrolestes | |
|---|---|
 | |
| Skull ofN. patagonensis | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Clade: | Cladotheria |
| Clade: | †Meridiolestida |
| Family: | †Necrolestidae Ameghino,1891[1] |
| Genus: | †Necrolestes Ameghino, 1891 |
| Type species | |
| Necrolestes patagonensis Ameghino, 1891 | |
| Species | |
| |
Necrolestes ("grave robber" or "thief of the dead") is an extinct genus ofmammals, which lived during theEarly Miocene in what is nowArgentinePatagonia. It is the most recent known genus ofMeridiolestida, an extinct group of mammals more closely related totherians (marsupials and placentals) than tomonotremes, which were the dominant mammals in South America during the Late Cretaceous. It contains two species,N. patagonensis andN. mirabilis; thetype speciesN. patagonensis was named by Florentino Ameghino in 1891 based on remains found by his brother,Carlos Ameghino in Patagonia. Fossils ofNecrolestes have been found in theSarmiento andSanta Cruz Formations.[2] Its morphology suggests that it was a digging, subterranean-dwelling mole-like mammal that fed on invertebrates.
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About one-third of the skeleton ofN. patagonensis—including most of the skull— has been found as disassociated bones of several individuals. The snout bends upwards at its end. The opening of the nasal fenestra has a septomaxilla separating thenasal andpremaxilla bones, which is unknown intherian mammals, with the nasal fenestra also appearing to have ossified external nasal cartilage.[3] The forelimbs have numerous characters in common with those offossorial mammals, including amedially curvedolecranon process of the ulna, and a mediolaterally compressed head of the humerus.[4]
Necrolestes was probably a subterranean mole-like mammal that fed on invertebrates. The morphology of the snout suggests that it dug by lifting its snout upwards, similar to modernmarsupial moles andgolden moles, as well as by using its forelimbs. The high volume of the middle ear suggests that it had enhanced hearing of low-frequency sounds.[3]
Its classification was historically unclear due to it being highlyapomorphic and having ananatomy unlike any other known mammal, living or extinct. It was thought to be atherian mammal; placement within either themarsupial lineage (Metatheria) or as a member ofEutheria 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 Rougieret al. (2012), Chimento, Agnolin and Novas (2012) and Averianov, Martin and Lopatin (2013) recoveredNecrolestes in an unexpected phylogenetic position as a nontherian mammal that belonged to the cladeMeridiolestida;[5][6][7] if confirmed this would makeNecrolestes the youngest known member of the group. Within Meridiolestida, Rougieret al. (2012) foundNecrolestes to be particularly closely related to the generaCronopio andLeonardus;[5] Chimentoet al. (2012) found it to be in unresolvedpolytomy withCronopio,Leonardus and the clade containing all other meridiolestidans[6] while Averianovet al. (2013) recoveredCronopio,Necrolestes andLeonardus as forming agrade at the base of Meridiolestida rather than a clade.[7] A subsequent 2017 monograph of the skull anatomy further supported a placement within Meridiolestida.[3]
Thiscladogram follows the paper of Rougier, Wible, Beck and Apesteguía of 2012:[5]
