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Cynodont radiation and morphological diversity (free pdf)

From: Ben Creisler

A new paper in open access:

Marcello Ruta, Jennifer Botha-Brink, Stephen A. Mitchell and Michael
J. Benton (2013)
The radiation of cynodonts and the ground plan of mammalian
morphological diversity.
Proceedings of the Royal Society B 280 (1769) 20131865
doi: 10.1098/rspb.2013.1865

Cynodont therapsids diversified extensively after the Permo-Triassic
mass extinction event, and gave rise to mammals in the Jurassic. We
use an enlarged and revised dataset of discrete skeletal characters to
build a new phylogeny for all main cynodont clades from the Late
Permian to the Early Jurassic, and we analyse models of morphological
diversification in the group. Basal taxa and epicynodonts are
paraphyletic relative to eucynodonts, and the latter are divided into
cynognathians and probainognathians, with tritylodonts and mammals
forming sister groups. Disparity analyses reveal a heterogeneous
distribution of cynodonts in a morphospace derived from cladistic
characters. Pairwise morphological distances are weakly correlated
with phylogenetic distances. Comparisons of disparity by groups and
through time are non-significant, especially after the data are
rarefied. A disparity peak occurs in the Early/Middle Triassic, after
which period the mean disparity fluctuates little. Cynognathians were
characterized by high evolutionary rates and high diversity early in
their history, whereas probainognathian rates were low. Community
structure may have been instrumental in imposing different rates on
the two clades.

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