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Late Cretaceous metatherians and survival into Paleocene



From: Ben Creisler
bcreisler@gmail.mail

A new non-dino paper that may be of interest:



Thomas E. Williamson, Stephen L. Brusatte, Thomas D. Carr, Anne Weile
& Barbara R. Standhard (2012)
The phylogeny and evolution of Cretaceous–Palaeogene metatherians:
cladistic analysis and description of new early Palaeocene specimens
from the Nacimiento Formation, New Mexico.
Journal of Systematic Palaeontology 10(4):625-651
DOI:10.1080/14772019.2011.631592
http://www.tandfonline.com/doi/full/10.1080/14772019.2011.631592

Metatherian mammals were the most diverse mammalian clade in North
America through the Late Cretaceous, but they underwent a severe
extinction at the Cretaceous–Palaeogene (K-Pg) boundary. In order to
clarify the origin of Palaeogene metatherians and the pattern of
metatherian survivorship across the K-Pg boundary we conducted an
inclusive species-level phylogenetic analysis of Cretaceous and early
Palaeogene metatherian taxa. This analysis includes information from
new Palaeocene specimens from south-western North America. Both the
phylogenetic topology and information from new specimens support the
validity of the genus Thylacodon and justify the recognition of a new
species, T. montanensis. Thylacodon is closely related to Swaindelphys
and Herpetotheriidae, which must have diverged by the latest
Cretaceous due to its close relationship with late Campanian
Ectocentrocristus. Pediomyidae and ‘Peradectidae sensu lato’ together
comprise a major metatherian clade. Maastrichtidelphys, from the Late
Cretaceous of the Netherlands, is the oldest member of ‘Peradectidae
sensu lato’, indicating a Cretaceous origination for this group.
Therefore, the major groups Herpetotheriidae and ‘Peradectidae sensu
lato’, represented almost completely by Palaeocene taxa, must have
originated in the Late Cretaceous. The lineages leading to these
clades include at least four lineages that must have crossed the K-Pg
boundary and therefore confirm that the K-Pg boundary marked a
profound extinction event for metatherians and suggests that
Palaeogene taxa originated from only a few clades of Cretaceous
species, all of which were relatively minor or very rare components of
known Cretaceous mammalian faunas.