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four-winged dino -- ptero homology?
Do you think the homologous case of Sharovipteryx sheds any light on the
current four-winged controversy?
Pterosaurs, and especially Sharovipteryx, apparently ran bipedally on
hind limbs encumbered(?) by flight membranes and glided with them as
well. In the latter case, the hind wings are much larger than the fore
wings, but it doesn't take too much imagination to consider that at one
point in the ancestry of Sharovipteryx the fore and hind wing membranes
were similarly sized.
The disarticulation of the femur, in the case of the bird, has a
homologous problem in the case of certain basal pterosaurs
(dimorphodontids) in which uropatagia are present yet the femoral head
is strongly angled to the femoral shaft. In my opinion the hind limbs
were held in an inverted V in these cases. Later pterosaurs improved
this situation, bringing the hind limbs into the plane of the wing by
increasing the angle between femoral head and shaft, reaching an acme in
the soaring taxa of the Niobrara and Santana formations.
In the case of the four-winged dinosaur, perhaps the legs were held in a
similar inverted V during flight. Such a vertical stabilizer is
currently used by pilotless drone aircraft and might have been a
necessary step in "teaching" the wings and tail to handle maneuvers