Flight evolved twice?

i suppose it's debatable, actually. haha good one.

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Thread moved here from the Biological Evolution forum.

Yes, very true. Perhaps I should have said dinosaurs evolved flight twice (note: peterosaurs are not evolved from dinosaurs).

Some more news

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Aslan is not a Tame Lion

yeah yeah, old new. microraptor's kinda cool though.

Thanks, jar, great link.Key observation from the article: Can you hear the whoosh of goal posts in rapid retreat?

probably not. if i recall, microraptor was WAY out of sequence -- a fluke. notice four-winged dinosaurs weren't very popular, and we don't have very many four-winged birds today.but yes, other than that, lots of transitional stages.

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I was thinking about this fossil last night and wondering how it could perch on a branch: as soon as it lowered the feet they would stop and the bird would 'trip' and do a belly-flop.It also seems impossible that the leg feathers would be splayed to the side while it was on the ground as that would require space and prevent any running for take-off = dead meat.The conclusion I come to is that the leg feathers must {feather\windvane} to the rear to allow running and perching.If this is the case then they could equally be used to "run" in the air, using the upper wings for lift.{abe}And this of course gets us back to ground up versus tree down{/abe}What do you think?This message has been edited by RAZD, 10*15*2005 12:59 PM

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we are limited in our ability to understand
by our ability to understand

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RebelAAmerican.Zen[Deist
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most of the thought i've heard suggests that microraptor was aboreal, whereas the dinosaurs that evolved powered flight were runners.however, i'm not totally sure. the pictures i'm looking at kind of seem to show the hallux too far up the leg for it to perch, and it does seem to have a sternum. but i don't know a lot bout microraptor. i'll keep looking.

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I remembered reading something about this from Jar's article, so I went and grabbed it: So, arboreal is the claim.They seem to think it could perch; why do you guys think perching would be a problem? I didn't understand RAZD's original description. Seems to me their feet are exposed enough to grab something; am I just not properly visualizing the motions necessary to perch?Ben

well, i'm trying to find some better pictures. but the reconstructions i've seen show the hallux (1st toe) too far up the foot. it has to be lower to be used like a modern bird's, to perch. basically, imagine trying to grab a branch if you thumb was half-way down your arm.but the foot isn't really shaped like a running foot either. so i don't know.

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The problem is that as the feet straighten to {reach\grab} the perch the feathers on it go vertical, so the feet stop before the bird, and either they stop before the bird reaches the branch (and belly flops on it), or they stop on the branch while the bird's body keeps going.Either way, it sounds like something for the Silly Design Institute ...ORThe feathers on the feet can {fair\flap} backwards to prevent this drag.This would also allow them to run on the ground, thus invalidating the only arboreal concept.But the real trick is that in the air that same running motion would engage the feathers on the down-stroke to power the bird, while using the upper wings as {lift\glider} members only before they need to develop flapping power.It's a beautiful intermediate between {running\gliding} and {flapping\flying} if that can be shown to be the case.

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we are limited in our ability to understand
by our ability to understand

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RebelAAmerican.Zen[Deist
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i'm looking at this thing closely, and i can;t figure it out.it has arboreal TOES, but the running leg proportions and the 2nd toe of a dromeosaur. it doesn't seem to have an opposed hallux, and not in the right place for grasping branches.if you could show me something on it's feet, i'd greatly appreciate. right now, i can't seem to tell what it would have done. right now, it looks far too much like a running dino for me to say it lived in trees -- even if that's what all the pro's are saying.evowiki says:

quote:

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The metatarsal feathers are probably inconsistant with a cursorial lifestyle, and the osteology of the manus and pes provide further support for an arboreal ecology.

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http://www.evowiki.org/index.php/Microraptor_gui

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the foot, maybe. but its hands look exactly like archaeopteryx, which are basically extended dromeosaurid hands.oh, and here's a more plausible gliding method, which i happened to find on deviantart Microraptor Gliding by Qilong on DeviantArtand a skeletal reconstruction: http://www.deviantart.com/view/16668095/This message has been edited by arachnophilia, 10-15-2005 11:51 PM

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I thought that reconstruction was ruled out by the hip bones not letting the legs extend back that way.That rear leg toe usage seems weird like running on the back of your hand with that one up the shin. Perhaps it controls the angle of the leg feathers?Fun to speculate.Another thing to consider for the arboreal version though is the way birds grasp trunks instead of brancheshttp://www.dcwild.com/images/Backyard/Wren%201.jpgThis kind of perch would require the full stop with wings and feet both straight up to aquire.It depends on what the leg feathes can and cannot do.

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we are limited in our ability to understand
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RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ...
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i'm not sure. i know very little about microraptor gui. do you have any information you could share?