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Re: *Microraptor* the biplane: published
Roberto Takata wrote:
If Chatterjee is correct in his analysis, a biplane mode of flight
would be plesiomorphic to Aves or an autapomorphy of _Microraptor_?
Chatterjee does not commit to either scenario ("Both scenarios are equally
possible", as the paper puts it). Nevertheless, the authors seem to favour
the former hypothesis (biplane configuration plesiomorphic for Aves).
Chatterjee and Templin appear to be alluding to phylogenetic bracketing in
support of this, given that hindlimb feathers have a broad distribution
among maniraptorans, inside and outside of Aves. However, at this stage
metatarsal contour feathers are only known for microraptorans and
_Pedopenna_. Thus, there is no direct evidence that metatarsal feathers are
plesiomorphic for Aves.
The 'biplane' configuration for aerial locomotion in _Microraptor_ is an
ecomorphological hypothesis. Metatarsal contour feathers as a character
that is primitive for Aves - this is a phylogenetic hypothesis. If a
phylogenetic analysis finds support for the latter, it would corroborate the
hypothesis that a biplane configuration is primitive for Aves. So far,
there is no compelling evidence that the direct ancestors of birds passed
through a biplane stage. On the other hand, there is no compelling evidence
that they didn't.
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