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Author Topic:   Where are all the missing links?
arachnophilia
Member (Idle past 1374 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 15 of 302 (231920)
08-10-2005 2:10 PM
Reply to: Message 9 by deerbreh
08-10-2005 12:50 PM


Re: Flying squirrels
How likely is that flying (gliding) squirrels could ever develop full fledged flight? Is it possible that many flying animals had transitional gliding forms?
there's some debate over the functionality and purpose of feathers originally. the "gliding" hypothesis is not generally accepted by everyone.
for instance, feathers appeared to have developed first in small gournd-based theropods for warmth and/or display. flight seem to have developed from the ground up, so to speak.

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Replies to this message:
 Message 16 by deerbreh, posted 08-10-2005 2:37 PM arachnophilia has replied
 Message 17 by Theus, posted 08-10-2005 3:48 PM arachnophilia has replied

arachnophilia
Member (Idle past 1374 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 24 of 302 (232032)
08-10-2005 6:18 PM
Reply to: Message 17 by Theus
08-10-2005 3:48 PM


Re: Evolution of feathers
However, there is still a large gap between flight feathers and down.
actually, there's not. the discoveries are rather recent. we have a species with down, a species with long hair-like feathers, a species with vanes, a species with symmetric nearly modern feathers without barbules and one with asymetric ones with barbules. that's pretty much all of the steps. not much mystery involved anymore.
hmmm... T-rex arms suddenly looking pretty handy now...
no, they really don't. they're so tiny that any "lift" effect wings would have would be negligable, if even present. i think they're not built like raptor arms, that move in an action very similar to flapping. you kind of have to remember exactly how disproportionately small t. rex's arms were. he couldn't even reach his mouth with them.
Of course it's pure speculation, but that would explain the diversity of theropod forms and sizes and why there doesn't seem to be a straight line to our avian friends.
no, there isn't a set path. those are pretty hard to find in the fossil record. archaeopteryx may not be a direct ancestor of modern birds, but it's definitally transitional in the right direction. certainly it shares a common ancestor with modern birds, and it's more closely related to that ancestor than birds today.

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Replies to this message:
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arachnophilia
Member (Idle past 1374 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 25 of 302 (232033)
08-10-2005 6:22 PM
Reply to: Message 16 by deerbreh
08-10-2005 2:37 PM


Re: Flying squirrels
would guess that the "arboreal gliding hypothesis" is more relevant to mammal flight than birds
you mean bats? lol. it's a good case for bats, probably. (i don't actually know this one. anyone?)
but as an "armchair evolutionist" I would not rule it out for birds.
well, it's not totally rules out. there are some feathered dinos that seem to have been arboreal. microraptor seems to have jumped from tree to tree -- and as such has FOUR wings.
but the main path to flight seems to have been from the ground. leg feathers are pretty uncommon even in later arboreal feathered dinos (as some has suggested archaeopteryx is). sort of an evolutionary dead end, not the source.

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arachnophilia
Member (Idle past 1374 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 41 of 302 (232153)
08-11-2005 3:10 AM
Reply to: Message 38 by Theus
08-10-2005 11:26 PM


t. rex's arms
Congratulations! You have found the reasonably esoteric "thread within a thread"!
oh dear, have i ever.
There certainly are indicators that it was used for something, but it may be specific to something we cannot measure, such as mating behavior.
a popular theory is "getting up off the ground." doubt that has TOO much weight to it, but they certainly seem to be very ineffective for hunting.
It was no problem for T-rex to outrun Triceratops or a Hadrosaur, but outrunning T-rexes in competition for food is something else entirely.
there was some suggestion for a while that t. rex was a sprinter at best, as he's not really built for speed in any way. i think the argument had mostly to do with leg proportions -- he doesn't have a leg structure conducive to a good run. so the idea that he feathers would have been much use at all for lift is kind of suspect if he's not that good of a runner.
but if you have any good information on this, i'd be interested in what you (or dr bakker!) has to show. (hey, one can keep dreaming, right?)
Excellent point on the feathers (downy vs. flight). However, I was referring to the initial functional jump, not the now-known path of it's development. There must be an additional selectional step to focus on downy feathers to push them toward feathers capable of flight.
i'm not totally sure.
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arachnophilia
Member (Idle past 1374 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 42 of 302 (232154)
08-11-2005 3:12 AM
Reply to: Message 40 by randman
08-11-2005 12:10 AM


Re: Missing Links / Missing Birds
You find a bird with lizard-like qualities you position as "half-way" in between, and then complain that creationists "just cannot be satisfied" as if that is some sort of conclusive evidence.
no, we find a half-dozen or more species at various intermediate points, and then complain when creationists refuse to connect the dots.

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arachnophilia
Member (Idle past 1374 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 47 of 302 (232337)
08-11-2005 2:21 PM
Reply to: Message 43 by Nuggin
08-11-2005 3:42 AM


Re: Missing Links / Missing Birds
I'd love to have you on a jury if I was being tried for a crime.
there is such a thing as reasonable doubt. but in this case, the doubt is nowhere near reasonable.

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