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How birds got their wings

Frank Robert

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A branch of the tree of life that includes the time when the propatagium, vital to flight in future birds, came about.
"Modern birds capable of flight all have a specialized wing structure called the propatagium without which they could not fly. The evolutionary origin of this structure has remained a mystery, but new research suggests it evolved in nonavian dinosaurs. The finding comes from statistical analyses of arm joints preserved in fossils and helps fill some gaps in knowledge about the origin of bird flight.
For a long time now, we have known modern birds evolved from certain lineages of dinosaurs that lived millions of years ago. This has led researchers to look to dinosaurs to explain some of the features unique to birds, for example, feathers, bone structure and so on. But there's something special about the wings of birds in particular that piqued the interest of researchers at the University of Tokyo's Department of Earth and Planetary Science."
"At the leading edge of a bird's wing is a structure called the propatagium, which contains a muscle connecting the shoulder and wrist that helps the wing flapping and makes bird flight possible," said Associate Professor Tatsuya Hirasawa.
"It's not found in other vertebrates, and it's also found to have disappeared or lost its function in flightless birds, one of the reasons we know it's essential for flight. So, in order to understand how flight evolved in birds, we must know how the propatagium evolved. This is what prompted us to explore some distant ancestors of modern birds, theropod dinosaurs."
 
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Frank Robert

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Only on paper.
You must have missed the physical evidence connecting propatagium in fossils of certain dionsaurs and wing joints of all birds except those who have lost the ability for flight. You can falsify the theory by finding flying birds w/o a propatagium.
 
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Ophiolite

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You can falsify the theory by finding flying birds w/o a propatagium.
They're out there Frank. I've seen 'em. Trouble is when I creep up on them the pesky rascals just fly away! What more proof do you need?
 
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The Barbarian

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"Modern birds capable of flight all have a specialized wing structure called the propatagium without which they could not fly.
The killer question for those denying that birds are dinosaurs is "What feature found in birds, is not also found in at least some dinosaurs?" And now, it seem that this feature isn't going to be the magic bullet, either.
 
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The Barbarian

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It seems that the propatagium was preadapted to flight, having evolved before flying dinosaurs evolved. What Gould referred to as a "spandrel", a phenotypic feature that is a byproduct of the evolution of some other characteristic, rather than a direct product of adaptive selection.

Our analyses support the hypothesis that the preserved propatagium-like soft tissues in non-avian theropod dinosaurs (oviraptorosaurian Caudipteryx and dromaeosaurian Microraptor) are homologous with the avian propatagium, and indicate that all maniraptoran dinosaurs likely possessed the propatagium even before the origin of flight. On the other hand, the preserved angles of wrist joints in non-avian theropods are significantly greater than those in birds, suggesting that the avian interlocking wing-folding mechanism involving the ulna and radius had not fully evolved in non-avian theropods. Our study underscores that the avian wing was acquired through modifications of preexisting structures including the feather and propatagium.
 
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