RE: Yet more on pterosaur quad arm posture

["David Marjanovic" <david.marjanovic@gmx.at>]

> It counts as climbing.

Hopping from branch to branch (and repeatedly falling off) counts as climbing?

...

*lightbulb moment*

...Uh, sorry. This might be a linguistic misunderstanding. In English you 
"climb" stairs, and you can "climb" a mountain by just walking up instead of 
pulling yourself up a rock face; German has a more specialized word, and that's 
what I had in mind all this time.

> Again, for perching adaptations to evolve, there was a population of animals 
> that went into elevated perches WITHOUT such adaptations, and that provided 
> the selection pressure for them to evolve. Were basal paravians all doing 
> that, and did it take until, say the Sapeornis node in Avialae for the 
> arboreal adaptations to arise?

Well, if they were all doing that for 40 million years till that node, I'd 
expect some adaptations to arise earlier than that.

> The only other way it could have happened is if there were exaptations, such 
> as gripping feet (Fowler et al. 2011), that allowed elevated perches and were 
> later replaced by reversed halluces. This exaptation is reported for 
> dromaeosaurs, which are also paravians.

And it makes plenty of sense. Indeed, the hallux already isn't perfectly 
parallel to the 3rd toe in those dromaeosaurs -- all claw tips converge during 
flexion.

> And, when we ask what good the intermediate stages of flapping flight would 
> be, a valid answer is "to get 1 meter off the ground into a low roost", 
> because living basal birds (tinamous, galliforms, anatids) still share the 
> character of roosting this way.

Very good point.