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Re: Microraptor biplanes?

Michael Habib (mhabib5@jhmi.edu) wrote:

<I'm not sure if you mean the extended leg or the flapping leg when you ask if
it would be possible.  Modern birds can extend their legs straight backwards
from the knee down, but the femur will always point forward in flight (and
cannot rotate much past vertical).  However, Microraptor, to the best of my
knowledge, still retained the theropod femoral position (rather than a derived
bird femoral alignment).>

  Paul in the publication I cited from 2003 argues that the legs would have a
"dangling" look based on his "flying" skeletal of *Sinornithosaurus* with
slight flexure at the hip, knee, but stronger flexure at the ankle, and the
femora more or less parallel to one another, capable of everting at the hip
laterally forming a pair of flapping limbs (arms and legs). I have argued
extensively that such femoral eversion is not possible in *Microraptor* or
*Sinornithosaurus*, evidence later disregarded by Paul when he published his
article without describing the actual osteological features that permit this,
merely illustrating animals doing this. The sinornithosaur pouncing on a
psittacosaur is quite impressive, actually, and may have actually happened, but
not requiring flapping legs to be acheived. *Sinornithosaurus* for example
shows no evidence of fully pennaceous vanes on the arms, while NGMC 91 ("Dave")
only preserves cohesive vanes extending from the thigh but these were absent
below the ankle due to preservation of squamation on the metatarsus, so that
"Dave" didn't have "buttfans" as seem present in *Microraptor*. I had argued
that Paul's evidence of an absent supracetabular crest is incorrect, that the
femur based on diagenesis of the bones duyring taphonomy cannot be used to
proclaim the condition of the crushed femora of *Microraptor* or
*Sinornithosaurus* permit Paul to describe the femoral caput as elevated enough
to cause the femur to evert laterally beyond some 15 degrees. Scott Hartman and
taken the figures of the specimens and shown in more detail than I could with
words how this is possible. Thus "microraptors" did not flap their legs.
<As for the flapping, 'twisting' in the legs is very limited in birds. Nearly
all motion is restricted to parasagittal motion.>

  But then again, microraptors aren't precisely birds :).


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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