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Norm King asked if in addition to the morphological change AND the protein chan
ge couldn't feathers still have come from scales.
In addition to the proteins themselves, there are a separate set of genes
for each of the structures. It's now just scale protein genes becoming
feather protein genes. The scale genes in reptiles can be found in birds,
as well as bird scale genes (but they are different in a variety of ways.
There are also differences in the developmental sequences between avain
scale-beak-claw anb feather. The feather follicle is unique.
BTW, differences in morphology of the contour feathers (including all
body and flight (primary) feather are fashioned from the same proteins.
The differences in morphology are most likely due to changes in growth patterns
This is a function of the follicle. Follicles, buy the way, are also capable
of producing feathers of different morphology in each molt. Clearly another
mechanism involving timing.