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the molecular evidence

Hi listmember

I need your appreciations about this new paper

Birds have dinosaur wings: the molecular evidence

Alexander O. Vargas & John F. Fallon, 2004..
Jour. Experimental Zoology B304 IN PRESS.

ABSTRACT. Within developmental biology, the digits of the wing of birds are
considered on embryological grounds to be digits 2, 3 and 4. In contrast,
within paleontology, wing digits are named 1, 2, 3 as a result of
phylogenetic analysis of fossil taxa indicating that birds descended from
theropod dinosaurs that had lost digits 4 and 5. It has been argued that the
development of the wing does not support the conclusion that birds are
theropods, and that birds must have descended from ancestors that had lost
digits 1 and 5. Here we use highly conserved gene expression patterns in the
developing limbs of mouse and chicken, including the chicken talpid2mutant
and polydactylous Silkie breed (Silkie mutant), to aid the assessment of
digital identity in the wing. Digit 1 in developing limbs does not express
Hoxd12, but expresses Hoxd13. All other digits express both Hoxd12and
Hoxd13. We found this signature expression pattern identifies the
anteriormost digit of the wing as digit 1, in accordance with the hypothesis
these digits are 1, 2 and 3, as in theropod dinosaurs. Our evidence
contradicts the long-standing argument that the development of the wing does
not support the hypothesis that birds are living dinosaurs.


Bruno H.