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[dinosaur] Schowalteria, Late Cretaceous taeniodont + extinct Nesophontes traced back to Cretaceous




Ben Creisler
bcreisler@gmail.com

New papers:

Richard C. Fox (2016)
The status of Schowalteria clemensi, the Late Cretaceous taeniodont (Mammalia).
Journal of Vertebrate Paleontology, Article: e1211666 
DOI: 10.1080/02724634.2016.1211666.
http://www.tandfonline.com/doi/full/10.1080/02724634.2016.1211666


Schowalteria clemensi Fox and Naylor, from the latest Cretaceous lower Scollard Formation, Red Deer Valley, Alberta, is the only known Mesozoic member of the extinct mammalian order Taeniodonta. Schowalteria clemensi was originally classified in the derived family Stylinodontidae, but more recent studies employing computer-assisted phylogenetic and stratocladistic analyses of taeniodont interrelationships contend that S. clemensi is the basal taeniodont, whereas Onychodectes, long considered the basal taeniodont, is instead the sister group of stylinodontids alone. These studies, however, are deeply flawed, marred by selection of problematic outgroups, incorrect scoring of numerous character states and of the stratigraphic age of S. clemensi, omission of all stylinodontid-like characters of S. clemensi, and reliance on major, implausible reversals during early taeniodont history. The more recent of these analyses also examined the relationship of taeniodonts within Eutheria, but this data set includes 54 (61%) erroneous scores for S. clemensi, the only taeniodont in the analysis. Moreover, subsequently published errata introduced new errors into the analyses. Thus, the hypothesis that S. clemensi is the earliest discovered stylinodontid remains unrefuted by these studies: the earliest history of stylinodontids and that of more basal taeniodonts is still to be discovered, among species older than S. clemensi itself.



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Selina Brace, Jessica A. Thomas, Love Dalén, Joachim Burger, Ross D. E. MacPhee, Ian Barnes and Samuel T. Turvey (2016)
Evolutionary history of the Nesophontidae, the last unplaced Recent mammal family.
Molecular Biology and Evolution (advance online publication)
doi: 10.1093/molbev/msw186
http://mbe.oxfordjournals.org/content/early/2016/09/07/molbev.msw186.abstract

The mammalian evolutionary tree has lost several major clades through recent human-caused extinctions. This process of historical biodiversity loss has particularly affected tropical island regions such as the Caribbean, an area of great evolutionary diversification but poor molecular preservation. The most enigmatic of the recently extinct endemic Caribbean mammals are the Nesophontidae, a family of morphologically plesiomorphic lipotyphlan insectivores with no consensus on their evolutionary affinities, and which constitute the only major Recent mammal clade to lack any molecular information on their phylogenetic placement. Here we use a palaeogenomic approach to place Nesophontidae within the phylogeny of recent Lipotyphla. We recovered the near-complete mitochondrial genome and sequences for 17 nuclear genes from a ~750-year-old Hispaniolan Nesophontes specimen, and identify a divergence from their closest living relatives, the Solenodontidae, more than 40 million years ago. Nesophontidae is thus an older distinct lineage than many extant mammalian orders, highlighting not only the role of island systems as “museums” of diversity that preserve ancient lineages, but also the major human-caused loss of evolutionary history.

News:

http://www.livescience.com/56080-caribbean-mammal-traced-to-dinosaur-age.html

http://phys.org/news/2016-09-ancient-dna-extinct-caribbean-island.html