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Re: Scales, hair, integumentary structure relationships?

David Marjanovic (david.marjanovic@gmx.at) wrote: 

<In all* modern birds, including the hoatzin at all growth stages, the third 
finger contains a single short bone which is probably a fusion product and 
encased in the same flesh as the second finger. The second and third 
metacarpals are fused at the proximal and the distal end; the first metacarpal 
is very short and fused to the proximal ends of the others as well as to the 
distal carpals.>

  I am curious as to the source of info that a single phalanx would be the 
product of a fusion, rather than simply losing the distal elements of the 
digit? It seems plausible to me, as it appears in the pedal features, than an 
intermediate phalanx would simply not condense during development, or would 
gain the characteristics (as happens in mammals) of the preceeding or suceeding 
digit, and thus simply not have that phalanx. Since distal loss of phalanges 
appears to be classic for birds, given the absence of ungual-like elements of 
the manus in most birds, should we not predict that phalangeal elimination is 
the culprit, rather than phalangeal fusion?


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)