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Feathers before flight

From: Ben Creisler

In the new issue of Science in the Perspective section:

Julia Clarke (2013)
Feathers Before Flight.
Science 340 (6133): 690-692
DOI: 10.1126/science.1235463

Feathers are branched structures consisting of β-keratin--a rigid
protein material formed by pleated β sheets--with a hollow central
shaft. They are strikingly different from other forms of vertebrate
integument such as scales, skin, and hair. Until recently,
evolutionary hypotheses envisioned their origin through elongation of
broad, flat scales driven by selection for aerial locomotion such as
gliding or flapping flight. Over the course of the past two decades,
fossil discoveries, especially from northeast China, have revealed
that the early precursors of feathers were filament-like rather than
expanded scales and that branched pinnate feathers of modern aspect
predate the origin of active flight. The revolution in our
understanding of feather evolution continues, driven by rapid fossil
discoveries and by new information from the study of extant birds.