The Evolution of Flight.... why are some birds grounded?

Andya, If flight/gliding can evolve from swimming (!!!) what is your incredulity based upon that rules out gliding from running?Mark------------------
"I can't prove creationism, but they can't prove evolution. It is [also] a religion, so it should not be taught....Christians took over the school board and voted in creationism. That can be done in any school district anywhere, and it ought to be done." Says Kent "consistent" Hovind in "Unmasking the False Religion of Evolution Chapter 6."

Andya,You miss the point, I understand fully that flying fish aren't true flyers, yet gliding is a plausible, I think you will agree, precursor of flight. Flying fish have managed a surface up transition.Given that we know that they have, then we also know it's not impossible. But in the grand scheme, they are unlikely to be anything like the ancestral bird. Why? Bird legs, like Archaeopterix' articulate for running in a particular way, very similar to therapodan/dinosaurs. Microraptors legs don't, & it is found more recently than Archaeopterix fossils. This means that therapod hind limbs evolved into Microraptor like legs, & then back again. Or archaeosaurs evolved Microraptor legs, then bird/therapod like legs. I therefore put it to you that Microraptor gui is actually more derived than Archaeopterix, rather than possesses ancestral characters of all birds.That said, the number of synapomorphies that birds & therapods share is amazing, & simply cannot be just written off to convergent evolution. I therefore put it to you that the large majority of evidence points to a therapod ancestor of birds. I'm happy to consider an arboreal therapod, of course. But haven't been convinced that the ground up hypothesis is sufficiently flawed enough to be considered inferior to the arboreal hypothesis. Presumably because it possessed dromaeosauridae/dinosaur characters & not archosaur?Mark[This message has been edited by mark24, 09-28-2003][This message has been edited by mark24, 09-28-2003]

Mr Jack,There's nothing wrong with the argument, nor is it not worthwhile. We just don't know the size of, nor the relative front limb dimensions, of the bird ancestors. Dromaeosaurs aren't found in rocks older than Archaeoptery so we don't know what the so-called protodromaeosaur really looked like. It doesn't always follow that bipedalism reduces the forelimbs, of course, us for example. Particularly if you are using your feathered arms for rapid changes of direction whilst prey chasing, to increase your acceleration/top speed. The flying fish managed surface up gliding without any musculature in the fins themselves.Mark

Andya, I agree, but at the moment it is a hypothetical missing link, if fact that's all both sides have. The Maniraptorans. You miss the point, bipedalism did not significantly reduce the forelimbs.Mark

Jack, But the fact remains we don't have tiny T-Rex forelimbs. They remained viable limbs, & could potentially be co-opted for other purposes, which they have alreasy been given we no longer use them for Tarzan like activities. The point I was arguing against was that bipedalism results in greatly reduced forelimbs that would be useless for co-option. It doesn't.Mark------------------
"I can't prove creationism, but they can't prove evolution. It is [also] a religion, so it should not be taught....Christians took over the school board and voted in creationism. That can be done in any school district anywhere, and it ought to be done." Says Kent "consistent" Hovind in "Unmasking the False Religion of Evolution Chapter 6."

Rei,But they remain viable for co-option, which is the point, after all.Mark

This should put the cat among the Archaeopteryx .From the excellent resource, Dinosauria On-Line.Dinosauria On-Line"Many Cretaceous theropods - dromaeosaurs, troodonts, oviraptors - are more bird-like than Archaeopteryx in many respects, and have a shoulder girdle that is similar to secondarily flightless birds. All this suggests that avian flight first evolved in arboreal theropods (where they developed big brains and forward facing eyes, features not found in flying insects and pterosaurs), and that some of the flying theropods lost flight. Not knowable at this time is whether Archaeopteryx was a member of the true bird clade, or was an independent experiment in flight, or where theropods end and birds begin, among other matters. "Mark[This message has been edited by mark24, 09-30-2003]