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Re: Of course nonavian dinosaurs could fly - duh

> > Elongate feathers on the metatarsus would be
> > equally awkward in an arboreal bird as in a
> > ground-dwelling bird.

Bear in mind that the Jurassic was still grass-less and largely herb-less. That 
still leaves two other problems:
The ground effect establishes a ceiling (perhaps a meter above ground) that is 
tough to break from below - even if you could glide-hop a bit, that does not 
mean that you were able to become free-flying (even free-gliding), because as 
soon as you get out of the ground effect "cushion", sustaining airborneness 
becomes suddenly much tougher.
Meanwhile, the non-sprawling leg posture would make the conventional climbing 
styles seen today virtually impossible.

Though in the Jurassic at least, in either case an animal that evolved the 
basic abilities to do either - basic gliding, or some alternate way of climbing 
(perhaps involving dorsoventral rather than lateral spine flexion, think 
inchworms - Geometridae caterpillars - for the resultant motion) - would have 
few if any competitors. 

But there are also predators to avoid. In the case of ground effect, I am not 
sure whether the increased vertical speed would be significant enough to help. 
In the case of climbing ability, even a vestigial ability to get up a trunk or 
rock would be helpful. Baboons (which cannot really climb well) climbing trees 
to avoid lions (which when adult can climb even worse) is such a case, but they 
have to use such a partially "inchworm-style" or "vertical gallopping" 
technique. It is easier to thwart a terrestrial predator by vertical than by 
horizontal movement, in particular as leg feathers might give you getter 
hop-gliding ability but increase the interference with even a clubmoss or other 
low growth and are thus at least altogether neutral as regards the ability to 
turn quickly.

(If they were neutral, they could still be crucial in the evolution of flight, 
but the crucial step would be subsequent to evolving them, not evolving them in 
the first place)