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Wing Feather Arrangement in Archaeopteryx and Anchiornis

From: Ben Creisler

A new online advance paper:

Nicholas R. Longrich, Jakob Vinther, Qingjin Meng, Quangguo Li &
Anthony P. Russell (2012)
Primitive Wing Feather Arrangement in Archaeopteryx lithographica and
Anchiornis huxleyi.
Current Biology (advance online publication)
doi: http://dx.doi.org/10.1016/j.cub.2012.09.052

In modern birds (Neornithes), the wing is composed of a layer of long,
asymmetrical flight feathers overlain by short covert feathers and .
It has generally been assumed that wing feathers in the Jurassic bird
Archaeopteryx  and  Cretaceous feathered dinosaurs  had the same
arrangement. Here, we redescribe the wings of the archaic bird
Archaeopteryx lithographica and the dinosaur Anchiornis huxleyi  and
and show that their wings differ from those of Neornithes in being
composed of multiple layers of feathers. In Archaeopteryx, primaries
are overlapped by long dorsal and ventral coverts. Anchiornis has a
similar configuration but is more primitive in having short, slender,
symmetrical remiges. Archaeopteryx and Anchiornis therefore appear to
represent early experiments in the evolution of the wing. This
primitive configuration has important functional implications:
although the slender feather shafts of Archaeopteryx  and Anchiornis
make individual feathers weak, layering of the wing feathers may have
produced a strong airfoil. Furthermore, the layered arrangement may
have prevented the feathers from forming a slotted tip or separating
to reduce drag on the upstroke. The wings of early birds therefore may
have lacked the range of functions seen in Neornithes, limiting their
flight ability.


► The early bird Archaeopteryx has a primitive wing composed of
multiple feather layers
► A similar configuration is found in the feathered dinosaur Anchiornis
► Wing structure and function evolved markedly between feathered
dinosaurs and modern birds