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Re: *Microraptor* the biplane: published
David Marjanovic (david.marjanovic@gmx.at) wrote:
<<What sort of fossil would cinch either side? If there definitively *was* a
biplane stage, what might we one day find?>>
<At least two double-decked basal bird clades.>
Not neccessarily true. It is not actually required for there to have been any
self-contained group of animals which possessed the adaptation on any lineage
to produce this feature for it to be inferred as a progressively adaptive trait
on the road to avian flight. Two groups, or clades, can be just as likely to
adapt the same smaller pennages into large fluight surfaces if they were, say,
in similar ecosystems with similar habits and dietary preferrences, or that one
was adapted as prey, and the other adapted to hunt the volant little buggers.
It will be neccessary, however, for there to be two distinct animals in the
fossil record to produce the same pennages, and be serially removed from modern
birds or verifiably "modern" flighted birds otr descendants thereof, who are
themselves more "derived" than animals without the feature but clearly derived
FROM that acestral condition, stock, and -- well -- clade.
<<If there definitively *was not* a biplane stage, what would we find
instead?>>
<At least two single-decked basal dromaeosaur clades ("dromaeosaur" here
actually meaning "everything closer to *Microraptor* than to birds").>
We would have to find out that *Microraptor* was not, in fact, a biplane.
Which is to say, the [soon to be] published work of Chatterjee and Templin and
Paul's earlier (albeit casual) treatment in _Prehistoric Times_ are mistaken on
the topic, and that my earlier comments here on the DML in 2001-2002 providing
that the leg would have been far tucked up are similarly way off the mark.
Even if deinonychosaurs or the dromaeosaurid/microraptorian clade (if even
that exists!) developed the biplanar design, they would have had to have
independantly developed the feature de novo, rather than from, say, something
on the bird line with apparent features relating to the biplanar deisgn. That
many birds and birdlike dinosaurs seem to have possessed long tibial feathers
is reason to support there was a lot of experimenting, but also that it seems
only one animal "went biplane" so far: *Microraptor*. Note that
*Sinornithosaurus* (NGMC 91) possesses NO tarsal feathers, only distinct
squamation of the tarsus, while extensive filamentous preservation suggests
lack of distinct feathers in both the type of *S. millenii* and NGMC 91,
indicating the evolved condition in *M. gui* is restricted and not broadly
present in the group.
Cheers,
Jaime A. Headden
http://bitestuff.blogspot.com/
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
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