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Author Topic:   Early birds had dino-feet: study
Hongi
Inactive Member


Message 31 of 36 (352759)
09-28-2006 6:43 AM
Reply to: Message 29 by RAZD
09-27-2006 9:01 PM


quote:
Welcome to the fray Hongi.
Thank you RAZD.
quote:
what this is more evidence of, is that a dinosaurian trait was retained in spite of what habitat the critter preferred
Do we have evidence that Archaeopteryx lived in trees at all? Right now, both sides of the debate on whether ground-up or tree-down seem a little short on evidence.
Edited by Hongi, : No reason given.

This message is a reply to:
 Message 29 by RAZD, posted 09-27-2006 9:01 PM RAZD has replied

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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 32 of 36 (352770)
09-28-2006 7:40 AM
Reply to: Message 31 by Hongi
09-28-2006 6:43 AM


... evidence that Archaeopteryx lived in trees at all?
I believe the evidence is more that Archy was semi-aquatic, a different feather of a horse altogether.
The reason there is still a debate on ground-up vs tree-down is that there is still no convincing evidence one way or the other.
Personally I think ground-up is more likely.
First, there is good evidence of the benefit of undeveloped wings in young grouse to be able to "run" up tree trunks using the non-flight capable wings to generate enough thrust to get a grip on the tree.
http://findarticles.com/...s/mi_m1134/is_10_112/ai_111736241
Second, there would be more selection pressure to actually take off to avoid predation.
Third, non-flight wings would also be useful for (a) changing direction rapidly and (b) appearing bigger than you really are and (c) mating displays.
Enjoy.

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This message is a reply to:
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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 33 of 36 (352880)
09-28-2006 3:28 PM
Reply to: Message 28 by Dr Adequate
09-27-2006 8:20 PM


You're assuming a lineage which did all its adapting to living in trees before it started to glide/fly. There is no reason why this should be the case.
Not so, I'm assuming it was adapted to living in trees. The article states that the feet were adapted to "running on the ground"; I asked you whether this was correct because I've not studied the fossils and don't really have the technical knowledge to determine either way anyhow. While we need not expect the features to be exactly those of perching birds, we should expect them to be those of a tree dweller not a ground runner (squirrels certainly do not have feet like those of dedicated ground dwellers such as deer, hogs or even capyburra). The "Trees Down" hypothesis does require that ancestoral "pre-birds" were tree dwellers, and this should leave us with feet adapted to tree dwelling.
The article may be overstating it's case; I don't know. But if it what it says is correct then I think this counts as a compelling reason for supporting ground-up. Although it is, of course, possible that the first birds were tree dwelling and Archaeopteryx then re-adapted for running on the ground.

This message is a reply to:
 Message 28 by Dr Adequate, posted 09-27-2006 8:20 PM Dr Adequate has replied

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 Message 34 by Dr Adequate, posted 09-28-2006 9:45 PM Dr Jack has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 34 of 36 (352997)
09-28-2006 9:45 PM
Reply to: Message 33 by Dr Jack
09-28-2006 3:28 PM


You're assuming a lineage which did all its adapting to living in trees before it started to glide/fly
Not so, I'm assuming it was adapted to living in trees.
You're claiming that its feet should have been completely adapted to arborial living. Why?
(squirrels certainly do not have feet like those of dedicated ground dwellers such as deer, hogs or even capyburra).
Yes, well, I'm not sure that the appropriate comparison for a tree-dwelling rodent should be either an ungulate or a semi-aquatic rodent with webbed feet.
If you compare the feet of the adorable little Southern flying squirrel is RAZD's link to those of, say, a gerbil, can you see any significant difference?
Squirrel feet are well adopted to running on the flat too, you know. Nippy little creatures, they are.
Edited by Dr Adequate, : No reason given.
Edited by Dr Adequate, : No reason given.
Edited by Dr Adequate, : No reason given.

This message is a reply to:
 Message 33 by Dr Jack, posted 09-28-2006 3:28 PM Dr Jack has replied

Replies to this message:
 Message 35 by Dr Jack, posted 09-29-2006 5:14 AM Dr Adequate has replied

  
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 35 of 36 (353043)
09-29-2006 5:14 AM
Reply to: Message 34 by Dr Adequate
09-28-2006 9:45 PM


You're claiming that its feet should have been completely adapted to arborial living. Why?
Because that's what the "tree's down" hypothesis postulates: that bird evolved from tree dwelling creatures.

This message is a reply to:
 Message 34 by Dr Adequate, posted 09-28-2006 9:45 PM Dr Adequate has replied

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 Message 36 by Dr Adequate, posted 09-29-2006 12:43 PM Dr Jack has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 36 of 36 (353122)
09-29-2006 12:43 PM
Reply to: Message 35 by Dr Jack
09-29-2006 5:14 AM


* sigh *
But not that they were completely adapted to that in every respect before the evolution of wings (which, under the TDH, was also an adaptation to living in trees, and arguably a much more useful one then, e.g. a reversed hallux). There is nothing in the hypothesis which demands that Archaeopteryx should have evolved "feet-first".
Can you point out any adaptation for arboreal life which is "missing" from the foot of Archaeopteryx (other than the reversed hallux, which is also "missing" from the Southern flying squirrel)?
If you can show me some adaptation which all arboreal animals have, and Archaepteryx lacks, I shall eat the primitive ancestor of a crow.
'Til then, the point is moot.

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