Re: Microraptor also ate fish

[Tim Williams <tijawi@gmail.com>]

Jason Brougham <jaseb@amnh.org> wrote:

> Mickey has been indefatigable here in reminding us all that UNCERTAINTY must 
> be
> respected in science. We must not overinterpret our evidence, and we must 
> remember that
> even the best - supported hypothesis can still be proven wrong in an instant 
> by new
> discoveries. Though it may be a bummer to say "we don't know", if we stop 
> saying that then
> we are letting speculation get the best of us.


I think I agree with you.  But I think "uncertainty" should not be an
excuse for rampant hand-waving.


What I'm all about is morphological correlates and testable
hypotheses.  So your raven example is quite pertinent...


> Let's consider the proposal that there is no way that Microraptor could climb 
> onto a terminal
> branch. Ravens, Corvus corax, weigh about 1.2 kg, about the same as some 
> specimens of
> Microraptor. [snip]  We all know that ravens have fully developed halluces, 
> but uncertainty
> exists about the possible gripping function of Microraptor's second toe and 
> the function of
> manual claws in stabilizing climbing.


Unless you are arguing that _Microraptor_ could perch like a raven
(and clearly you aren't), I would say that comparing _Microraptor_ to
a raven is irrelevant and moot.  _Microraptor_ has no morphological
traits that are correlated with an ability to climb out on to terminal
branches the way ravens do.  Yes, _Microraptor_ might have done so.
Animals often perform functions for which they are not adapted.  But
I'm trying to keep our inferences about an animal's behavior to a
soundly scientific footing (so to speak).  In short: What was
_Microraptor_ actually *adapted* to do?


I agree that uncertainty exists about the possible gripping function
of _Microraptor_'s second toe, and the function of manual claws in
stabilizing climbing.  However, before we embark upon too much
speculation, I'd like to have some evidence that the foot was
biomechanically capable of grasping a narrow branch.  The study by
Fowler et al. (2011), which is centered on _Deinonychus_, makes it
clear that the second toe was involved in gripping large prey.  This
grasping pes may have been exapted in other lineages for arboreal
perching; but it wasn't there yet.  Not even close, IMHO.


Regarding the manual claws, there is an issue regarding how it is
difficult to distinguish predation from climbing ability (after all,
both require gripping).  This leaves scope for exaptation, if a
predatory manus was co-opted for climbing, which is possible in small
maniraptorans.  This is an entirely scientific example of
"uncertainty".


But if we say that the manual claws or pes could be used for functions
for which they were clearly not adapted, then we're on shaky ground.
This is a way that "uncertainty" is mis-used.  The foot of
_Microraptor_ was *not* adapted for perching.  No amount of discussion
about wood ducks and ravens will convince me of otherwise.


> Therefore it may be HARDER for Microraptor to do so, but I would not be 
> comfortable saying
> there is NO way.


I'd say the morphology of _Microraptor_ says "no way".  It has no
adaptations that correlate with an ability to grasp narrow branches,
either with its hands or feet (or both together).  If we are going to
claim that _Microraptor_ engaged in behaviors for which it was *not*
adapted, and that these behaviors were important to its life habits,
then I think we're heading in the wrong direction.


> Uncertainty is a high principle, everyone.


Yes, but let's not use uncertainty as an invitation for woolly thinking.






Cheers

Tim