Advanced Ornithology
by
Maryam Riasat
EVOLUTION OF FEATHERS

Evolution of feathers
 Feathers are the defining characteristic of
birds
 Well developed feathers of Archaeopteryx
separated it from dinosaurs
 Later discoveries revealed that feathers and
featherlike structures are not unique to birds
 Theropods dinosaurs had them also

Feathered Dinosaurs
• Chicken sized Sinosauropteryx with
filamentous downlike feathers
• Caudipteryx with a well preserved fan of
vaned feathers on its tail and forelimbs
• More than a dozen fossil feathers of theropod
dinosaurus and dromaeosaurs have now been
found that are not closely related to
Archaeopteryx

 Ancient feathers included
downlike filamentous structures
or dino-fuzz and well-vaned, that
are essential modern feather structure
 The relation of dino-fuzz to real
feathers remains controversial
Arguments range from their being
unrelated structures to being precursors
of feathers

 Less controversial are the well preserved
vaned feathers
 A little dinosaur named Microraptor gui had
front and hind wings that sported outer
feathers with asymmetrical vanes just as in
the wings of modern flying birds
 Feathers clearly evolved in the modern form
in theropod dinosaurs and then diversified in
form and function

 It is believed that feathers evolved from scales
of some kind
 Feathers evolved not as modified scales but
as a novel epidermal structure
o A hypothesis long favored by reptile experts
is: Even if the feathers evolved from scales,
they were likely aided temperature regulation
as insulation or heat shields

 Feathers did not evolve initially in concert
with the evolution of flight
 Rather avian flight followed the initial
evoltion of vaned feathers
 Gliding and weak flapping flight fostered
additional changes in feather form and
function on the wings and tail