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Adaptive radiation of anomodont therapsids (free pdf)

From: Ben Creisler

A new open access paper:

Marcello Ruta, Kenneth D. Angielczyk, Jörg Fröbisch and Michael J. Benton (2013)
Decoupling of morphological disparity and taxic diversity during the
adaptive radiation of anomodont therapsids.
Proceedings of Royal Society B 280 no. 1768 20131071
doi: 10.1098/rspb.2013.1071
free pdf:

Adaptive radiations are central to macroevolutionary theory. Whether
triggered by acquisition of new traits or ecological opportunities
arising from mass extinctions, it is debated whether adaptive
radiations are marked by initial expansion of taxic diversity or of
morphological disparity (the range of anatomical form). If a group
rediversifies following a mass extinction, it is said to have passed
through a macroevolutionary bottleneck, and the loss of taxic or
phylogenetic diversity may limit the amount of morphological novelty
that it can subsequently generate. Anomodont therapsids, a diverse
clade of Permian and Triassic herbivorous tetrapods, passed through a
bottleneck during the end-Permian mass extinction. Their taxic
diversity increased during the Permian, declined significantly at the
Permo–Triassic boundary and rebounded during the Middle Triassic
before the clade's final extinction at the end of the Triassic. By
sharp contrast, disparity declined steadily during most of anomodont
history. Our results highlight three main aspects of adaptive
radiations: (i) diversity and disparity are generally decoupled; (ii)
models of radiations following mass extinctions may differ from those
triggered by other causes (e.g. trait acquisition); and (iii) the
bottleneck caused by a mass extinction means that a clade can emerge
lacking its original potential for generating morphological variety