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FW: Microraptor hanqingi, new species from China.



________________________________________
From: Jason Brougham
Sent: Thursday, May 24, 2012 11:27 PM
To: tijawi@gmail.com
Subject: RE: Microraptor hanqingi, new species from China.

You are right and we agree that arboreality in basal paravians is not proven 
and should not be assumed. I have an open mind as to whether basal paravians 
were arboreal or terrestrial, as well as the possibilities of mixed habitat, 
including roosting. I certainly do not think there is conclusive evidence for 
roosting in these early forms, but I have been keenly interested to see how 
many of the most unlikely modern birds, including highly cursorial ones and 
even some of the few birds with no halluces, can roost and even nest in trees.

I wonder why you say that galliforms are poor analogs for basal paravians? The 
only aspects of the latter bauplan you named are long necks and long legs and 
leg proportions. if cursorial theropods like turkeys aren't good analogs for 
cursorial theropods like, say, Caudipteryx, then what are? And what living 
animal would you say is the best analog for Archaeopteryx?

Perhaps you could strengthen your arguments by explicitly listing those 
differences between the bauplan of basal paravians and modern birds that may 
make it impossible or unlikely for the former to roost in trees.

You did say that petrels have the benefit of being descended from a  perching 
bird. This benefit, I guess, in your context is simply being relatively squat. 
But Epidendrosaurus may be equally or even more short necked and short legged 
compared to petrels. And how does a long - necked bauplan keep an animal from 
roosting anyway? No non-avian theropod has legs as disproportionately long as 
the Secretarybird, Sagittarius. Yet they perch quite readily (albeit with good 
halluces).

Galliforms have a rudimentary hallux that is elevated above the other toes, but 
it can usually touch the ground. Nonetheless, I have many photos of turkeys 
roosting in trees, adopting postures where the hallux is held clear and does 
not oppose the other toes 
osture is often used by galliforms in trees and is rarely mentioned. This is 
where the birds climb around on slender branches by catching the branches 
between their longer toes, say between II and III or III and IV. I don't know 
if they can pinch the branches or simply catch them fork-like and press down 
with their body mass. I can document in in grouse, turkeys, and chickens. This 
method should be entirely possible in basal paravians.

I guess to make any progress in this matter we'd have to compile a multivariate 
data set, including many body proportions and hallucal morphologies, and see if 
there is a strong signal of what range of measurements in morphological 
characters correlates with roosting. If all basal paravians fall outside that 
range, then we'd have some evidence that you're correct in doubting they could 
roost.

I don't think anyone's ever done that with anything other than toe proportions, 
have they?

One last thing, lizards, snakes, and frogs have also given rise to arboreal 
forms multiple times. Comparative studies could also benefit from looking at 
how they made the transitions to roosting, nesting, and even gliding.
________________________________________
From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu] on behalf of Tim Williams 
[tijawi@gmail.com]
Sent: Thursday, May 24, 2012 10:18 PM
To: dinosaur@usc.edu
Subject: Re: Microraptor hanqingi, new species from China.

Jason Brougham <jaseb@amnh.org> wrote:

> Alright, fair enough, petrels are squatter than Archaeopteryx. But there are 
> bipedal, cursorial, theropods with the bauplan of long legs and long necks 
> and small, elevated, halluces that
>  are not fully capable of perching - and they also roost in trees. Galliforms 
> like turkeys, I'm thinking of.


Turkeys have a descended, reversed hallux that is eminently capable of
opposing the anterior toes.  It's just not as specialized for perching
as in those birds (including other galliforms, like cracids) that
spend much more of their time in trees.  The peacock is similar to the
turkey in this 


> I was worried that someone would say petrels can sit in trees because they 
> descended from birds that had functioning halluces. It seems illogical to say 
> that a morphological character
> is crucial for a certain function, but that the function can be retained even 
> if the character is lost.


That's not what I said at all.  What I said was that the morphology of
modern flighted birds is quite different to that of theropods like
_Archaeopteryx_ or _Microraptor_.


> Let's just take this moment to note, there are theropods with no halluces 
> that roost
> and nest in trees. If you don't believe it google image search "petrel tree".


I believe that petrels can roost in trees.  I also happen to think
that it's largely irrelevant to the ecologies of _Archaeopteryx_ or
_Microraptor_.


> I am troubled that you dismiss any comparison between the function of basal 
> paravians and modern birds because the former have long necks and legs.


Again, that's not actually what I said.  I was speaking to the overall
bauplan.  Paravians like _Archaeopteryx_ or _Microraptor_ were
cursors; the proportions and ranges of motion at the joints reflect
that.


> In reality, this fact is little
> appreciated, but Microraptor, Anchiornis and Xiaotingia have necks roughly as 
> long as their skulls, putting them closer to medium - length - necked birds 
> like crows than they are to
> long - necked forms like storks or ducks.


But not to petrels, which is what my statement was in response to.


> The former retain long bony tails, of course, but it's not clear that basal 
> paravians would have had important functional differences from
> phasianids like peacocks with much heavier and longer masses of feathers on 
> their tails. If turkeys and peacocks aren't close enough to basal paravians 
> for you to serve as analogs,
> then no animal alive on earth today is, so no analogs can be cited.


Turkeys and peacocks are poor analogs for basal paravians.


> There is no perfect analog alive today for basal paravians, but the imperfect 
> ones we have demonstrate 
identified and measured a set of
> morphologies that correlate with the ability to roost in trees in living 
> animals, so this possibility cannot be excluded for basal paravians.


Fair enough.  But I'll turn this statement around and say this
possibility (roosting behavior in basal paravians) should not be
*assumed* until this work is done.  Simply saying "Well,
petrels/turkeys/tinamous roost in trees, why not _Archaeopteryx_ or
_Microraptor_?" is not a valid scientific argument.







Cheers

Tim