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Necrolestes, South American Miocene mammal as nontherian Mesozoic survivor

From: Ben Creisler

Non-dino but may be of interest:

Guillermo W. Rougie, John R. Wible, Robin M. D. Beck, and Sebastian
Apesteguía (2012)
The Miocene mammal Necrolestes demonstrates the survival of a Mesozoic
nontherian lineage into the late Cenozoic of South America.
Proceedings of the National Academy of Sciences (advance online publication)
doi: 10.1073/pnas.1212997109

The early Miocene mammal Necrolestes patagonensis from Patagonia,
Argentina, was described in 1891 as the only known extinct placental
“insectivore” from South America (SA). Since then, and despite the
discovery of additional well-preserved material, the systematic status
of Necrolestes has remained in flux, with earlier studies leaning
toward placental affinities and more recent ones endorsing either
therian or specifically metatherian relationships. We have further
prepared the best-preserved specimens of Necrolestes and compared them
with newly discovered nontribosphenic Mesozoic mammals from Argentina;
based on this, we conclude that Necrolestes is related neither to
marsupials nor placentals but is a late-surviving member of the
recently recognized nontherian clade Meridiolestida, which is
currently known only from SA. This conclusion is supported by a
morphological phylogenetic analysis that includes a broad sampling of
therian and nontherian taxa and that places Necrolestes within
Meridiolestida. Thus, Necrolestes is a remnant of the highly endemic
Mesozoic fauna of nontribosphenic mammals in SA and extends the known
record of meridiolestidans by almost 45 million years. Together with
other likely relictual mammals from earlier in the Cenozoic of SA and
Antarctica, Necrolestes demonstrates the ecological diversity of
mammals and the mosaic pattern of fauna replacement in SA during the
Cenozoic. In contrast to northern continents, the Cenozoic faunal
history of SA was characterized by a long period of interaction
between endemic mammalian lineages of Mesozoic origin and metatherian
and eutherian lineages that probably dispersed to SA during the latest
Cretaceous or earliest Paleocene.

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