Re: protofeathers

[Alan Brush <brush@uconnvm.uconn.edu>]

An earlier message from Tom Hopp:
> And as I understand Alan, there may have been proto- forms of all the
>>different feather morphologies, not just one that gave rise to all the
>>others. Amen.
This is certainly not the case. In theory, whatever the first structure, and I argue that it may have been simply a structure similar to a barb that grew continually (which BTW could describe the situation in Sinosauropteryx). Subsequent changes that produces pennaceous or plumulose feather parts which were organized into the existing morphologies, are simply the breaking of symmetry in the follicle and differential growth rates. These 2 factors alone gave rise to all the modification of the basic morphology. Further, and this is more speculative, I posit that the most direct way to increase design complexity is to simply fuse these structures (barb homology (?) at their bases. That coincidentally produces the morphology of natal down.

Ron Ornsteins comment:

>As I understood him, I think he meant something else - namely that you
>cannot, based on current knowledge, put the known types of feathers into an
>evolutionary hierarchy such that down, for example, is more "primitive"
>than contour feathers; further, as the thing that evolved first was a
>feather-producing mechanism with sufficient flexibility to produce a wide
>variety of feather types from the get-go, the question (and thus the
>distinction between feathers and "protofeathers") may not mean much.  
>

is precisely the argument I make. As a matter of fact, it is easily argued that the answer to the query "what did a primitive feather look like?" might be answered by'depends on what part of the body do you mean. In other words, once the machinery appeared, then the morphology follows.

Cheers,

Alan

Alan H. Brush
92 High St.
Mystic, CT 06355
Brush@uconnvm.uconn.edu