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Identity of the avian wing digits: Problems resolved and unsolved
Author(s) -
Young Rebecca L.,
Bever Gabe S.,
Wang Zhe,
Wagner Günter P.
Publication year - 2011
Publication title -
developmental dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.634
H-Index - 141
eISSN - 1097-0177
pISSN - 1058-8388
DOI - 10.1002/dvdy.22595
Subject(s) - wing , numerical digit , biology , identity (music) , evolutionary biology , frame (networking) , biological evolution , genealogy , zoology , genetics , aesthetics , arithmetic , computer science , mathematics , history , telecommunications , philosophy , engineering , aerospace engineering
Controversy over bird wing digit identity has been a touchstone for various ideas in the phylogeny of birds, homology, and developmental evolution. This review summarizes the past 10 years of progress toward understanding avian digit identity. We conclude that the sum of evidence supports the Frame Shift Hypothesis, indicating that the avian wing digits have changed anatomical location. Briefly, the derivation of birds from theropod dinosaurs and the positional identities of the avian wing digits as 2, 3, and 4 1 are no longer in question. Additionally, increasing evidence indicates that the developmental programs for identity of the wing digits are of digits I, II, and III. Therefore, the attention moves from whether the digit identity frame shift occurred, to what the mechanisms of the frame shift were, and when in evolution it happened. There is considerable uncertainty about these issues and we identify exciting new research directions to resolve them. Developmental Dynamics 240:1042–1053, 2011. © 2011 Wiley‐Liss, Inc.