Latest news on placental phylogeny

[David Marjanovic <david.marjanovic@gmx.at>]

Shawn Zack: Paleogene taxa and the higher-level interrelationships of 
eutherian mammals, SVP meeting abstracts 2008, 163A

"The higher-level phylogeny of eutherian mammals is a source of controversy 
due to conflict between phylogenetic analyses emphasizing morphology and 
those emphasizing DNA sequences as character soruces. Each source of data 
favors clades that receive little support from the other partition and, for 
some taxa, the two partitions (morphology and molecules) are in direct 
conflict. One potential explanation for this discrepancy is that, because 
existing morphologic data sets rely heavily on extant placental mammals, 
homoplasy in extant taxa may obscure relationships within a radiation that 
occurred several tens of millions of years ago. In order to address this 
issue, a new morphological data set focused on the dental and postcranial 
[huh? why leave out the skull?] morphology of Paleocene and Eocene 
eutherians was constructed. Results of analysis of this matrix are most 
consistent with existing morphological analyses. Trees constrained to agree 
with a composite molecular topology present a significantly worse fit to the 
character data than do unconstrained trees. However, there are some 
noteworthy similarities to molecular topologies, including recovery of a 
clade containing Archonta and Glires, similar to molecular Euarchontoglires 
[ = Supraprimates = "Glimates"]. While Afrotheria was not supported, a 
monophyletic assemblage of ungulate-like African mammals was recovered. This 
study also provides new data on the relationships of numerous extinct 
higher-level taxa, including: recovery of a paraphyletic Leptictimorpha that 
may form the xenarthran stem taxon; failure to unambiguously support 
alliance of most extinct lipotyphlans with living families; and, no support 
for the monophyly of Carnivoramorpha [means, Miacidae and Viverravidae were 
found far away from Carnivora -- that's a big surprise]. Additionally, 
several supposedly distantly related taxa (amphilemurid erinaceomorphs; 
plagiomenid archontans; apheliscid condylarths) are united with 
macroscelideans. Results of this study are inconsistent with [under- or 
miscalibrated...] molecular hypotheses concerning the timing and 
biogeography of the placental radiation, but instead support the 
morphological view that this radiation occurred on northern continents in 
association with the K/T boundary."

The Cretaceous tooth taxon *Gypsonictops* is traditionally considered a 
member of what Zack calls Leptictimorpha, and was found as such by Wible et 
al. 2007 (the *Maelestes* paper, or rather its supplementary information 
[fig. 6], which also found that clade outside of Placentalia), but I dimly 
remember Zack finds *Gypsonictops* somewhere else, which would AFAIK once 
again mean that no K placentals are known. I could be wrong, though. Oh, and 
I forgot where he found the taeniodonts -- keyword *Schowalteria*.