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Re: Pro(to)avis




----- Original Message ----- From: "Michael Habib" <mhabib5@jhmi.edu>
To: <david.marjanovic@gmx.at>
Cc: "DML" <dinosaur@usc.edu>
Sent: Saturday, September 17, 2005 1:08 AM
Subject: Re: Pro(to)avis



I agree that it is risky to assume that the legs could reach a full
horizontal position (given that the specimens are crushed and that this
would be an unusual trait for theropods).

A crushed but very well illustrated referred specimen of *Microraptor zhaoianus* denies any capability for sprawling. But this wasn't even what I was talking about.


Assume *M. gui* held its feet in parallel, horizontal positions... if the metatarsal feathers stuck out laterally, we get a sort of biplane (with a small lower wing). This would help to explain why the foot feathers are more asymmetric than the hand feathers (which were directed laterocaudally rather than just laterally). This assumes that the long feathers on the lower and upper leg didn't get in the way, however. They would have to be directed caudally.

However, perhaps the feathers on the entire leg were directed caudally. http://dino.lm.com/images/display.php?id=2036 http://dino.lm.com/images/display.php?id=1204 http://dino.lm.com/images/display.php?id=1074 http://dino.lm.com/images/display.php?id=899 Who knows. The fossils are 2D. Perhaps the feathers were even mobile around the long axis of the foot???

If, anyway, the feathers could be spread out like a fan and folded back, the issue of how to run on hindwings becomes moot.

1) The limbs may have been held subhorizontal, but still held close
enough to a horizontal plane to generate lift.

Impossible for the legs. Maybe not for the foot feathers.

2) The hindlimb feathers may have more important to increasing passive
stability than to generating lift.

Possible. But then the forewings do look a little small... or at least narrow...