ScienceDaily (Nov. 21, 2012)
— A new study looking at the structure of feathers in bird-like
dinosaurs has shed light on one of nature's most remarkable inventions
-- how flight might have evolved.
Academics at the Universities of Bristol, Yale and Calgary have shown
that prehistoric birds had a much more primitive version of the wings
we see today, with rigid layers of feathers acting as simple airfoils
for gliding.
Close examination of the earliest theropod dinosaurs suggests that
feathers were initially developed for insulation, arranged in multiple
layers to preserve heat, before their shape evolved for display and
camouflage.
As evolution changed the configuration of the feathers, their
important role in the aerodynamics and mechanics of flight became more
apparent. Natural selection over millions of years ultimately modified
dinosaurs' forelimbs into highly-efficient, feathered wings that could
rapidly change its span, shape and area -- a key innovation that allowed
dinosaurs to rule the skies.
This basic wing configuration has remained more or less the same for
the past 130 million years, with bird wings having a layer of long,
asymmetrical flight feathers with short covert feathers on top. They are
able to separate and rotate these flight feathers to gain height,
change direction and even hover.
This formation allows birds to move in such a way as to produce both
lift and thrust simultaneously -- a capability that man, with the help
of technology, is still trying to successfully imitate.
The research, published November 21 in
Current Biology, looked at the dinosaur
Anchiornis huxleyi and the Jurassic bird
Archaeopteryx lithographica.
The latter is 155 million years old and widely considered to be the
earliest known bird, presenting a combination of dinosaur and bird
characteristics.
Their wings differed from modern day birds in being composed of
multiple layers of long feathers, appearing to represent early
experiments in the evolution of the wing. Although individual feathers
were relatively weak due to slender feather shafts, the layering of
these wing feathers is likely to have produced a strong airfoil.
The inability to separate feathers suggests that taking off and
flying at low speeds may have been limited, meaning that wings were
primarily used in high-speed gliding or flapping flight.
Dr Jakob Vinther, from the University of Bristol's Schools of
Biological and Earth Sciences, said: "We are starting to get an
intricate picture of how feathers and birds evolved from within the
dinosaurs. We now seem to see that feathers evolved initially for
insulation. Later in evolution, more complex vaned or pinnate feathers
evolved for display.
"These display feathers turned out to be excellent membranes that
could have been utilised for aerial locomotion, which only very late in
bird evolution became what we consider flapping flight. This new
research is shedding light not just on how birds came to fly, but more
specifically on how feathers came to be the way they are today -- one of
the most amazing and highly specialised structures in nature."
Dr Nicholas Longrich of Yale University added: "By studying fossils
carefully, we are now able to start piecing together how the wing
evolved. Before, it seemed that we had more or less modern wings from
the Jurassic onwards. Now it's clear that early birds were more
primitive and represented transitional forms linking birds to dinosaurs.
We can see the wing slowly becoming more advanced as we move from
Anchiornis, to
Archaeopteryx, to later birds."
Story Source:
The above story is reprinted from materials provided by University of Bristol.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
- Nicholas R. Longrich, Jakob Vinther, Qingjin Meng, Quangguo Li, Anthony P. Russell. Primitive Wing Feather Arrangement in Archaeopteryx lithographica and Anchiornis huxleyi. Current Biology, 21 November 2012 DOI: 10.1016/j.cub.2012.09.052
University of Bristol (2012, November 21). New evidence on dinosaurs' role in evolution of bird flight.
ScienceDaily. Retrieved November 22, 2012, from http://www.sciencedaily.com /releases/2012/11/121121130817.htm
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