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Archaeopteryx

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Majir
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« on: January 19, 2011, 01:28:28 pm »

Specimens of Archaeopteryx were most notable for their well-developed flight feathers. They were markedly asymmetrical and showed the structure of flight feathers in modern birds, with vanes given stability by a barb-barbule-barbicel arrangement.[21] The tail feathers were less asymmetrical, again in line with the situation in modern birds and also had firm vanes. The thumb, however, did not yet bear a separately movable tuft of stiff feathers.

The body plumage of Archaeopteryx is less well documented and has only been properly researched in the well-preserved Berlin specimen. Thus, as more than one species seems to be involved, the research into the Berlin specimen's feathers does not necessarily hold true for the rest of the species of Archaeopteryx. In the Berlin specimen, there are "trousers" of well-developed feathers on the legs; some of these feathers seem to have a basic contour feather structure but are somewhat decomposed (they lack barbicels as in ratites),[22] but in part they are firm and thus capable of supporting flight.[23]

There was a patch of pennaceous feathers running along the back which was quite similar to the contour feathers of the body plumage of modern birds in being symmetrical and firm, though not as stiff as the flight-related feathers. Apart from that, the feather traces in the Berlin specimen are limited to a sort of "proto-down" not dissimilar to that found in the dinosaur Sinosauropteryx, being decomposed and fluffy, and possibly even appeared more like fur than like feathers in life (though not in their microscopic structure). These occur on the remainder of the body, as far as such structures are both preserved and not obliterated by preparation, and the lower neck.[22]

However, there is no indication of feathering on the upper neck and head. While these may conceivably have been **** as in many closely related feathered dinosaurs for which good specimens are available, this may still be an artifact of preservation. It appears that most Archaeopteryx specimens became embedded in anoxic sediment after drifting some time on their back in the sea—the head and neck and the tail are generally bent downwards, which suggests that the specimens had just started to rot when they were embedded, with tendons and muscle relaxing so that the characteristic shape of the fossil specimens was achieved. This would mean that the skin was already softened and loose, which is bolstered by the fact that in some specimens the flight feathers were starting to detach at the point of embedding in the sediment. So it is hypothesized that the pertinent specimens moved along the sea bed in shallow water for some time before burial, the head and upper neck feathers sloughing off, while the more firmly attached tail feathers remained.[24]

http://en.wikipedia.org/wiki/Archaeopteryx
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