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Bird embryo wing digits are 1, 2, 3



From: Ben Creisler
bh480@scn.org

In case this new paper in Science has not been mentioned 
yet:

Koji Tamura, Naoki Nomura, Ryohei Seki, Sayuri Yonei-
Tamura, and Hitoshi Yokoyama (2011)
Embryological Evidence Identifies Wing Digits in Birds as 
Digits 1, 2, and 3.
Science 331(6018): 753-757 (11 February 2011)
DOI: 10.1126/science.1198229 
http://www.sciencemag.org/content/331/6018/753.abstract

Abstract
The identities of the digits of the avian forelimb are 
disputed. Whereas paleontological findings support the 
position that the digits correspond to digits one, two, 
and three, embryological evidence points to digit two, 
three, and four identities. By using transplantation and 
cell-labeling experiments, we found that the 
posteriormost digit in the wing does not correspond to 
digit four in the hindlimb; its progenitor segregates 
early from the zone of polarizing activity, placing it in 
the domain of digit three specification. We suggest that 
an avian-specific shift uncouples the digit anlagen from 
the molecular mechanisms that pattern them, resulting in 
the imposition of digit one, two, and three identities on 
the second, third, and fourth anlagens.