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Re: Aw: RE: Arboreal Theropods: The prize at the bottom of the cracker jack box



Tim Williams wrote:
> However, occasional/opportunistic tree-climbing seems entirely
> plausible (such as _Microraptor_ grabbing a little birdie off a tree
> branch).  But because this is still part of a fundamentally
> terrestrial ecology, it perhaps would not seep through into the
> anatomy.  So it's difficult to test for.

About those paravians and their questionable affinity for trees... I
may be barking up the wrong tree here (ha ha ha), but has anyone ever
attempted to formally resolve an "adaptive landscape"?  Species with
similar behaviors tend to cluster on the same peak; i.e. possess a
combination of traits that would be favored by natural selection for a
niche.  Maybe the suite of features possessed by paravians is an
example of such an adaptive landscape?  Maybe help resolve when one
peak was left for another peak?  Not quite sure how it's done, but
maybe such an analysis will help level the playing field, as it
were... de-emphasize those linch-pin traits in favor of a
whole-organism approach?  A superficial glance at all of the taxon
which often come under arboreal/scansorial scrutiny do indeed appear
to have possessed a peculiar combination of traits (e.g. peaks) that
some interpret as those for an arboreal/scansorial lifestyle, while
other traits are seen as not being favored by selection for such a
lifestyle (e.g. valleys), so on, and so forth.  Of course, my
understanding of adaptive landscapes is that they are notoriously hard
to test, and I'm certain even more so when extinct animals are
concerned.

Just a thought....

Oh, and if this hasn't already been done, and if I just planted the
seed in someone's brain who is actually in the position to try and do
this, you are welcome ;-)

V/r,
Kris

On Tue, Jul 23, 2013 at 8:31 AM, Tim Williams <tijawi@gmail.com> wrote:
> Jason Brougham <jaseb@amnh.org> wrote:
>
>> Well, hey, you can always say my counterexamples don't count. Strictly
>> speaking, they don't, because we are using derived animals to see what may
>> have been possible for primitive ones.
>
>
> Excellent point, IMHO.  There are a great many extant birds that show
> rudimentary aerial behaviors, such as WAIR or CFD (by fully volant
> species, including juveniles) or fluttering and short glides as
> exhibited by some secondarily flightless birds (the kagu has been
> mentioned, but there are others).
>
>
> It is possible that one of these extant non-flight aerial behaviors
> replicates the incipient flight behavior of the theropod ancestors of
> birds.  But they might not.  We may never know which behavior(s)
> engendered flight in theropods.  However, I don't think we should
> assume that it was "trees-down", despite the intuitive attraction of
> an arboreal origin of flight.
>
>
>> My goal is to stop people in this forum from saying it is impossible that
>> basal paravians utilized trees to some limited extent. I believe I have
>> demonstrated that it is possible, and that categorically excluding it with
>> the current evidence is not correct.
>
>
> I don't recall anyone saying that it was impossible for basal
> paravians to use trees.  Speaking solely for myself, I would say that
> the evidence for arboreality (i.e., spending most or all of their time
> in trees) in microraptorines and archaeopterygids is less than
> compelling.  To me, there is nothing in the osteology to back up
> arboreal ecologies in these taxa.
>
>
> However, occasional/opportunistic tree-climbing seems entirely
> plausible (such as _Microraptor_ grabbing a little birdie off a tree
> branch).  But because this is still part of a fundamentally
> terrestrial ecology, it perhaps would not seep through into the
> anatomy.  So it's difficult to test for.
>
>
> I'm certainly intrigued by GSP's data on _Microraptor_'s claw
> curvature.  Might highly arced pedal claws be useful for gaining
> purchase on soft terrain, such as a forest floor, or soft mud?
>
>
>
>
>
>
> Cheers
>
> Tim