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Re: flying Archie

John Bois wrote:

Prey _capture_ has been emphasized as a selective advantage of a shorter
tail. It could be that predator _avoidance_, for example via rapid vertical
takeoff, was also a big deal.

In basal birds (including _Archaeopteryx_), predator avoidance (or evasion) could have been achieved in the old-fashioned way: Running away. The thing about a long bony tail is that it does help keep the center of mass posteriorly, whereas shortening the tail (and expanding the sternum and pectoral musculature) shifts the center of mass forward of the hips. Modern birds have had to do a complete 'makeover' of the hindlimb in order to locomote on the ground, with stride generation principally occuring at the distal femur, not the hip.

I don't know at what stage the femur was decoupled from stride generation in avian evolution, but there must have been a transitional phase from the primitive theropod style to the derived avian style. During this transition, running on the ground might have been difficult, and birds may not have yet reached the point where a vertical takeoff was do-able. This could have been one selective pressure that kept _Archaeopteryx_ in its plesiomorphic coleurosaurian body plan. There are "costs" associated with the modern avian body plan, and I suspect Archie represents a compromise: it kept the benefits of a coelurosaurian osteology (including the primitive terrestrial locomotor style), while the plumage became dedicated to aerial locomotion.

Don Ohmes wrote:

Not local eco-stuff... also, implied in your post is the idea that A. may have been more optimal for tree to tree flight than modern birds, and birds sacrificed that to obtain long-distance flight. Highly doubtful, right?

I personally don't believe that _Archaeopteryx_ was optimal for tree-to-tree flight. The reason I say this is that its perching abilities were minimal to nonexistent. However, I do believe that _Archaeopteryx_ was adapted for flying over short distances.

Heinz Peter Bredow wrote:

I think that this concentration on Archaeopteryx regarding the origin of flight is arbitrary.

I don't think it is. Chronologically and morphologically, _Archaeopteryx_ is the first known theropod to show evidence of powered flight. Thus, until we have evidence to the contrary, then we must assume that _Archaeopteryx_ at least approximates an early stage in the evolution of flight. It certainly may not have been directly ancestral to later birds; and I don't deny that it is possible that _Archaeopteryx_ is a bizarre aberrant form that is a complete red herring to avian evolution (as you suggest). But the latter implies that we know a *lot* less than we think we do about avian evolution, which is a sobering thought.