Author
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Topic: Theropods and Birds showing a change in kinds
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RAZD
Member (Idle past 1404 days) Posts: 20714 From: the other end of the sidewalk Joined: 03-14-2004
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Message 22 of 150 (544393)
01-25-2010 10:06 PM
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Reply to: Message 18 by DC85 01-25-2010 10:16 AM
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posting tip
Hi DC85 If you put a white background behind the gif picture it is easier to see: [blockcolor=white][img=200] http:⁄⁄i7.photobucket.com/albums/y286/gbaz_matt/Arhaeopteryxskeleton.gif [/img][/blockcolor]
Enjoy Edited by Admin, : Add line breaks to long line.
This message is a reply to: | | Message 18 by DC85, posted 01-25-2010 10:16 AM | | DC85 has not replied |
Replies to this message: | | Message 32 by MiguelG, posted 01-28-2010 5:26 PM | | RAZD has seen this message but not replied |
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RAZD
Member (Idle past 1404 days) Posts: 20714 From: the other end of the sidewalk Joined: 03-14-2004
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Message 64 of 150 (545334)
02-03-2010 7:41 AM
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Reply to: Message 63 by caffeine 02-03-2010 5:22 AM
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Re: Feathers as novel features
Hi caffeine,
... Richard Prum, one of the world's experts on feathers, had proposed a model of feather evolution based on how they developed in the embryology of modern birds. What he predicted as 'Stage 1' in this evolution was an undifferentiated, hollow cylinder of beta-keratin. That is pretty much what we seem to have discovered in theropods. The question then becomes, how much of an ancestral structure do you need in order to evolve hollow, undifferentiated filaments of a protein already present in your skin? What's the difference between a feather follicle and a hair follicle? Enjoy.
This message is a reply to: | | Message 63 by caffeine, posted 02-03-2010 5:22 AM | | caffeine has not replied |
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RAZD
Member (Idle past 1404 days) Posts: 20714 From: the other end of the sidewalk Joined: 03-14-2004
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downy feathers first, then undifferentiated feathers, then flight feathers ...
Hi Catholic Scientist,
They put down feathers in coats because they ARE great for thermoregulation. They also are the first feathers that grow on newly hatched birds, and it is very common that organism growth patterns follow evolutionary patterns of development. Evolving a Protofeather and Feather Diversity1 | Integrative and Comparative Biology | Oxford Academic
quote: It is likely that feathers evolved from a conical shaped tubercle rather than a plate-like structure. Although the morphology of the presumably most primitive feather is unknown, minimal conditions for its production include the cellular capacity to synthesize feather proteins (={phi}-keratin) which provides the molecular phenotype, and a follicular mechanism for production and assembly of molecular and gross structure. By comparison, the most primitive animals to possess feathers are the maniraptorian dinosaurs, Protarchaeopteryx and Caudipteryx (Ji et al., 1998). The feathers on these specimens are recognizable as symmetrical primaries and semiplumes on the body. The Yixian formations of Liaong province in NE China are probably not older than 120 MYA (Smith et al., 1995Go; B. Idleman, personal communication) and, hence, early Cretaceous (Lucus and Estep, 1998Go). Although perhaps chronologically more recent, Caudipteryx is phylogenetically closest to Archaeopteryx, but may not be completely avian (Padian, 1998Go). The Yixian dinosaurs were cursorial, bipedal, and not capable of flight.
Interesting reading. Also has some thoughts on how feathers evolved. Another good reference is Feather evolution Enjoy.
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RAZD
Member (Idle past 1404 days) Posts: 20714 From: the other end of the sidewalk Joined: 03-14-2004
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Re: Feathers as novel features
Hi slevesque, sorry to add to your burden here
Real feathers are waterproof. That's why they are better insulators when they are 'wet'. The anhinga can barely fly when it emerges from the water due to the amount of water absorbed by its feathers. It has to sit in the sun to dry out, resulting in a recognizable pose. Anhinga - Wikipedia
quote: Unlike ducks, the Anhinga is not able to waterproof its feathers using oil produced by the uropygial gland. Consequently, feathers can become waterlogged, making the bird barely buoyant. However, this allows it to dive easily and search for underwater prey, such as fish and amphibians. It can stay down for significant periods.
When necessary, the Anhinga will dry out its wings and feathers. It will perch for long periods with its wings spread to allow the drying process, as do cormorants. If it attempts to fly while its wings are wet, it has great difficulty getting off the water and takes off by flapping vigorously while 'running' on the water. Anhinga will often search for food in small groups.
Birds that don't oil their feathers (like sparrows etc) can drown in water. Enjoy Edited by RAZD, : enjoy
This message is a reply to: | | Message 117 by slevesque, posted 02-05-2010 4:35 PM | | slevesque has not replied |
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RAZD
Member (Idle past 1404 days) Posts: 20714 From: the other end of the sidewalk Joined: 03-14-2004
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Re: Again with the dating.
Hi ZenMonkey,
I still assert that, as a YEC, slevesque has no standing to assert anything whatsoever regarding the dating and relationships of fossil evidence. Perhaps he is trying to understand the evolutionist argument thoroughly first. See Honest Debate: how do you read? Enjoy.
This message is a reply to: | | Message 129 by ZenMonkey, posted 02-05-2010 8:42 PM | | ZenMonkey has not replied |
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