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Eutherian morphological disparity across end-Cretaceous mass extinction (free pdf)

Ben Creisler

Here's the second new mammal paper by the authors, now out in open access:

Thomas John Dixon Halliday and Anjali Goswami (2015)
Eutherian morphological disparity across the end-Cretaceous mass extinction.
Biological Journal of the Linnean Society (advance online publication)
DOI: 10.1111/bij.12731

Free pdf:

In the aftermaths of mass extinction events, during radiations of
clades, and in several other evolutionary scenarios, there is often a
decoupling of taxonomic diversity and morphological disparity. The
placental mammal radiation after the end-Cretaceous mass extinction is
one of the archetypal adaptive radiations, but the change in
morphological disparity of the entire skeleton has never been
quantified across this important boundary. We reconstruct ancestral
morphologies of 680 discrete morphological characters onto dated
phylogenies of 177 mostly Cretaceous and Palaeogene eutherians
(placental mammals and their stem relatives). Using a new approach to
incorporate morphologies representing ghost lineages, we assess three
measures of morphological disparity (sum of ranges, sum of variances
and mean pairwise dissimilarity) across stage-level time bins within
the Cretaceous and Palaeogene. We find that the range-based metric
suggests that eutherian disparity increased immediately after the
end-Cretaceous mass extinction, while both variance-based metrics
declined from the Campanian to the Maastrichtian, but showed no change
in disparity from the Maastrichtian to the Puercan – the first North
American Land Mammal Age of the Paleocene. Increases in variance-based
metrics lag behind the range-based metric and per-lineage accumulation
rate, suggesting that the response of mammals to the
Cretaceous–Palaeogene event was characterized by an early radiation
that increased overall morphospace occupation, followed later by
specialization that resulted in increased dissimilarity.