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Re: New bird digit study supports "frame shift"
quite clearly, birds are not monophyletic but arose from two
DIFFERENT 75 my ghost linages of basal archosaurs, both developing the
semilunate carpal and feathers convergently to theropods!
BANDitry to the max!
On Sun, Sep 4, 2011 at 12:27 PM, <email@example.com> wrote:
> From: Ben Creisler
> A new online paper:
> Zhe Wang, Rebecca L. Young, Huiling Xue & Günter P.
> Wagner (2011)
> Transcriptomic analysis of avian digits reveals conserved
> and derived digit identities in birds.
> Nature (advance online publication)
> Morphological characters are the result of developmental
> gene expression. The identity of a character is
> ultimately grounded in the gene regulatory network
> directing development and thus whole-genome gene
> expression data can provide evidence about character
> identity. This approach has been successfully used to
> assess cell-type identity. Here we use transcriptomic
> data to address a long-standing uncertainty in
> evolutionary biology, the identity of avian wing digits.
> Embryological evidence clearly identifies the three wing
> digits as developing from digit positions 2, 3 and 4
> (ref. 6), whereas palaeontological data suggest that they
> are digits I, II and III. We compare the transcriptomes
> of the wing and foot digits and find a strong signal that
> unites the first wing digit with the first foot digit,
> even though the first wing digit develops from
> embryological position 2. Interestingly, our
> transcriptomic data of the posterior digits show a higher
> degree of differentiation among forelimb digits compared
> with hindlimb digits. These data show that in the stem
> lineage of birds the first digit underwent a
> translocation from digit position 1 to position 2, and
> further indicate that the posterior wing digits have
> unique identities contrary to any model of avian digit
> identity proposed so far.
> News story:
> Note that this analysis is different from the one
> recently posted in Nature Communications, which seemed to
> indicate that there is no “frame shift” in digit position.