Re: *Microraptor* the biplane: published

[Tim Williams <twilliams_alpha@hotmail.com>]

Anthony Docimo wrote:

> What sort of fossil would cinch either side?  If there definitively *was* a 
> biplane stage, what might we one day find?  If there definitively *was not* 
> a biplane stage, what would we find instead?

Ah yes, good question.  That's the problem with any hypothesis concerning 
behaviour in fossil taxa: they are impossible to demonstrate empirically.  
The same limitations also apply to all the hypotheses regarding powered 
flight in _Archaeopteryx_.  Such hypotheses can be corroborated or even 
refuted; but they can never be "proven".  The best we can do is see how a 
particular ecomorphological hypothesis stacks up against known aerodynamic 
or biomechanical data.

The thing is, the discovery of metatarsal feathers in a primitive bird 
(avian) might corroborate the hypothesis that this character is ancestral 
for Aves.  This is because metatarsal feathers are known for certain 
deinonychosaurs (like _Microraptor_) and a phylogenetic analysis may recover 
this character as plesiomorphic for Aves.  But this is a phylogenetic 
hypothesis.  The idea that the presence of metatarsal feathers coupled with 
forelimb feathers indicates a 'biplane' arrangement for flight means going 
further than simple phylogeny.

In other words, proposing that _Microraptor_ used the 'biplane' arrangement 
for aerial locomotion is an ecomorphological hypothesis.  However, proposing 
that this 'biplane' arrangement was ancestral to avian flight is both an 
ecomorpholological hypothesis and a phylogenetic hypothesis.

Cheers

Tim

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