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Re: Wing Feather Arrangement in Archaeopteryx and Anchiornis

From: Ben Creisler

A press release from Bristol University:



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 [ [1],
[2] and [3]]. It has generally been assumed that wing feathers in the
Jurassic bird Archaeopteryx [ [4], [5], [6], [7], [8] and [9]] and
Cretaceous feathered dinosaurs [ [10] and [11]] had the same
arrangement. Here, we redescribe the wings of the archaic bird
Archaeopteryx lithographica [ [3], [4] and [5]] and the dinosaur
Anchiornis huxleyi [ [12] and [13]] 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 [14] and Anchiornis [12] 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.