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Re: Tracing the Evolution of Avian Wing Digits (free pdf!)

From: Ben Creisler

Sorry I didn't catch this before I posted the ref. The pdf is
available for free at:


On Thu, Jun 20, 2013 at 5:45 PM, Ben Creisler <bcreisler@gmail.com> wrote:
> From: Ben Creisler
> bcreisler@gmail.com
> A recent paper not yet mentioned on the DML:
> Xing Xu & Susan Mackem (2013)
> Tracing the Evolution of Avian Wing Digits. [Review Article]
> Current Biology 23(12): R538–R544
> http://dx.doi.org/10.1016/j.cub.2013.04.071
> http://www.sciencedirect.com/science/article/pii/S0960982213005125
> It is widely accepted that birds are a subgroup of dinosaurs, but
> there is an apparent conflict: modern birds have been thought to
> possess only the middle three fingers (digits II-III-IV) of an
> idealized five-digit tetrapod hand based on embryological data, but
> their Mesozoic tetanuran dinosaur ancestors are considered to have the
> first three digits (I-II-III) based on fossil evidence. How could such
> an evolutionary quirk arise? Various hypotheses have been proposed to
> resolve this paradox. Adding to the confusion, some recent
> developmental studies support a I-II-III designation for avian wing
> digits whereas some recent paleontological data are consistent with a
> II-III-IV identification of the Mesozoic tetanuran digits. A
> comprehensive analysis of both paleontological and developmental data
> suggests that the evolution of the avian wing digits may have been
> driven by homeotic transformations of digit identity, which are more
> likely to have occurred in a partial and piecemeal manner.
> Additionally, recent genetic studies in mouse models showing plausible
> mechanisms for central digit loss invite consideration of new
> alternative possibilities (I-II-IV or I-III-IV) for the homologies of
> avian wing digits. While much progress has been made, some advances
> point to the complexity of the problem and a final resolution to this
> ongoing debate demands additional work from both paleontological and
> developmental perspectives, which will surely yield new insights on
> mechanisms of evolutionary adaptation.