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Evolution of feathers and beta-keratins



From: Ben Creisler
bh480@scn.org

A recent paper not yet mentioned on the DML:

Matthew J. Greenwold, Roger H. Sawyer (2011)
Linking the molecular evolution of avian beta (â) keratins to the evolution
of feathers.
Journal of Experimental Zoology Part B: Molecular and Developmental
Evolution
316: 609?616
DOI: 10.1002/jez.b.21436
http://onlinelibrary.wiley.com/doi/10.1002/jez.b.21436/abstract

Abstract
Feathers of today's birds are constructed of beta (beta)-keratins,
structural proteins of the epidermis that are found solely in reptiles and
birds. Discoveries of "feathered dinosaurs" continue to stimulate interest
in the evolutionary origin of feathers, but few studies have attempted to
link the molecular evolution of their major structural proteins
(beta-keratins) to the appearance of feathers in the fossil record. Using
molecular dating methods, we show that before the appearance of Anchiornis
(~155 Million years ago (Ma)) the basal beta-keratins of birds began
diverging from their archosaurian ancestor ~216 Ma. However, the
subfamily of feather beta-keratins, as found in living birds, did not begin
diverging until ~143 Ma. Thus, the pennaceous feathers on Anchiornis,
while being constructed of avian beta-keratins, most likely did not contain
the feather beta-keratins found in the feathers of modern birds. Our
results demonstrate that the evolutionary origin of feathers does not
coincide with the molecular evolution of the feather beta-keratins found in
modern birds. More likely, during the Late Jurassic, the epidermal
structures that appeared on organisms in the lineage leading to birds,
including early forms of feathers, were constructed of avian beta-keratins
other than those found in the feathers of modern birds. Recent biophysical
studies of the beta-keratins in feathers support the view that the
appearance of the subfamily of feather beta-keratins altered the
biophysical nature of the feather establishing its role in powered flight. 


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