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Re: More on Birds, dinosaurs, and digits



At 11:02 PM 11/30/97 -0600, Toby White wrote:
>...  The other lines of proof include: (1) Digit V has a
>fairly unique ontogeny in that it is not part of the digital arch. 
> It forms directly at the base of IV. 

I do not see that this is any better than the primary axis argument.  As
far as I can see, extreme reduction would tend to leave a vestigial, or
nearly vestigial, digit in *exactly* this relationship.  In short, I argue
that this is also a result of the digit's reduction, and is useless for
determining *which* digit it is.

>...  (2) The chicken pes clearly has five
>digits at some points in development.  The pes and manus are 
>analogous.

But not homologous.  In other words, I do not see why the manus and pes
must necessarily follow similar development patterns, especially n so
derived and altered a case as the avian manus.

>suggests that the same is true for the manus.  (3) the morphological
>analogues in the five-digit croc and turtle manus also suggest that 
>IV is the correct identification.

Having looked at their figures, I do not see this.  As far as I can see,
and sequence that reduces digits in a way that leaves only three will
result in about the same final pattern.


In short, I saw nothing whatsoever in their article that I felt was a
convincing demonstration of the identity of the avian manual digits.

--------------
May the peace of God be with you.         sarima@ix.netcom.com
                                          sfriesen@netlock.com