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Fwd: Origin of bird pygostyle (free pdf)

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 From tomasz.skawinski@o2.pl Wed Jul 30 15:40:50 2014
Subject: Origin_of_bird_pygostyle_(free_pdf)
From: Tomasz_Skawinski <tomasz.skawinski@o2.pl>
To: = DML <dinosaur@usc.edu>
Date: Thu, 31 Jul 2014 00:40:41 +0200

I think this paper has not been mentioned before:

Dana J Rashid, Susan C Chapman, Hans CE Larsson, Chris L Organ,
Anne-Gaelle Bebin, Christa Merzdorf, Roger Bradley and John R Horner
>From dinosaurs to birds: a tail of evolution.
EvoDevo 5: 25

A particularly critical event in avian evolution was the transition
from long- to short-tailed birds. Primitive bird tails underwent
significant alteration, most notably reduction of the number of caudal
vertebrae and fusion of the distal caudal vertebrae into an ossified
pygostyle. These changes, among others, occurred over a very short
evolutionary interval, which brings into focus the underlying
mechanisms behind those changes. Despite the wealth of studies delving
into avian evolution, virtually nothing is understood about the
genetic and developmental events responsible for the emergence of
short, fused tails. In this review, we summarize the current
understanding of the signaling pathways and morphological events that
contribute to tail extension and termination and examine how mutations
affecting the genes that control these pathways might influence the
evolution of the avian tail. To generate a list of candidate genes
that may have been modulated in the transition to short-tailed birds,
we analyzed a comprehensive set of mouse mutants. Interestingly, a
prevalent pleiotropic effect of mutations that cause fused caudal
vertebral bodies (as in the pygostyles of birds) is tail truncation.
We identified 23 mutations in this class, and these were primarily
restricted to genes involved in axial extension. At least half of the
mutations that cause short, fused tails lie in the Notch/Wnt pathway
of somite boundary formation or differentiation, leading to changes in
somite number or size. Several of the mutations also cause additional
bone fusions in the trunk skeleton, reminiscent of those observed in
primitive and modern birds. All of our findings were correlated to the
fossil record. An open question is whether the relatively sudden
appearance of short-tailed birds in the fossil record could be
accounted for, at least in part, by the pleiotropic effects generated
by a relatively small number of mutational events.

With kind regards,
Tomasz Skawiński