http://www.sciencedirect.com/science/article/pii/S0960982212011943
Primitive bird:
In modern birds (Neornithes), the wing is composed of a layer of long, asymmetrical flight feathers overlain by short covert feathers [1-3]. It has generally been assumed that wing feathers in the Jurassic bird Archaeopteryx [4-9] and Cretaceous feathered dinosaurs [10, 11] had the same arrangement. Here, we redescribe the wings of the archaic bird Archaeopteryx lithographica [3-5] and the dinosaur Anchiornis huxleyi [12, 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.
Longrich NR, Vinther J, Meng Q, Li Q, Russell AP.
Modern bird feather layers:
Anchiornis overlapping feathers:
ReplyDeletehttp://www.sciencedirect.com/science/article/pii/S0960982212011943
http://rspb.royalsocietypublishing.org/content/early/2009/07/31/rspb.2009.0846.full
ReplyDelete"The presence of a reticular pattern resulting from the dorsoventral compression of distinct layers of actinofibrils in phylogenetically distinct taxa such as Jeholopterus, which occupies a basal position within pterosaurs (Kellner 2004b), the non-pterodactyloid Pterorhynchus and a possible tapejarid pterodactyloid from the Crato Formation (Sayão & Kellner 1998), suggests that the presence of multi-layered actinofibrils in the wing membrane was widespread among pterosaurs".
http://en.wikipedia.org/wiki/Anchiornis
ReplyDeleteAnchiornis is notable for its proportionally long forelimbs, which measured 80% of the total length of the hind limbs. This is similar to the condition in early avians such as Archaeopteryx, and the authors pointed out that long forelimbs are necessary for flight. Anchiornis also had a more avian wrist than other non-avialan theropods. The authors initially speculated that it would have been possible for Anchiornis to fly or glide. However, further finds showed that the wings of Anchiornis, while well-developed, were short when compared to later species like Microraptor, with relatively short primary feathers that had rounded, symmetrical tips, unlike the pointed, aerodynamically proportioned feathers of Microraptor.[2]
Personal correspondence:
ReplyDelete"i have [not] done any serious search on the flight capablity of Anchiornis. i guess Anchiornis might have some flight capability. for example it has relatively long and robust arms, and also the feather shaft is curved, a feature sometimes related to flight."
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Dr. XU, Xing
Links on anchiornis:
ReplyDeletehttp://link.springer.com/article/10.1007%2Fs11434-009-0009-6
http://www.nature.com/nature/journal/v461/n7264/full/nature08322.html
http://www.sciencedirect.com/science/article/pii/S0960982212011943
ReplyDeleteThis 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.