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Re: Screaming dromaeosaur biplane killers of the air
Greg Paul (GSP1954@aol.com) wrote:
<As Boris Sorkin pointed out to me at SVP, the legs of Johel dromaeosaurs
could sprawl laterally because the femoral heads are spherical rather than
cylinderical (verified by my high resolution photos of the type
Sinornithosaurus, can be seen in the original Nature paper), and because
the sinornithosaur described in Nature April 2001 is spread eagled with
the legs splayed out. (In addition to the multiple specimens with the leg
feathers, this leg specialization verifies the presence of a wing on
sinornithosaur legs). This is never true of Archaeopteryx which is always
preserved on its side because it had a more dinosaurian cylinderical
femoral head and therefore could not sprawl the legs, and did not need to
since it lacked large leg wings. The later, secondarily flightless
dromaeosaurs logically reverted back to the dinosaurian cylinderical
femoral head and vertical only legs.
Since the legs could sprawl and the primary feathers are lift producing
strongly asymmetrical, sharp edged and therefore fully aerodynamic
structures of the sort always used for flight purposes in modern birds,
there is no doubt the leg arrays were true wings. The leg wings are as big
as the arm wings, so the former were not extra tail surfaces for normal
I'd like to point out that it is not presently possible without seeing
this data from Sorkin to determine the femoral extensiveness in these
basal dromaeosaurs. In NGMC 91, the femora are incomplete most proximally.
In *Microvenator* (CAGS 20-7-004), the femoral head is exposed in caudal
view and is not elevated or spherical in shape, but rather is horizontal,
on a short unconstricted neck, terminating medially in a subspherical
"hemi-ball" as in various other maniraptorans, such as *Bagaraatan*,
troodontids, etc. The greater trochanter also extends further dorsally
than the caput (in CAGS 20-8-001 and GAGS 20-7-004), which prevents
lateral extension of the femur as Greg posits above. The femora of
*Cryptovolans* are not well-enough preserved proximally to determine so.
In IVPP V13352 (type of *M. gui*) the far, right side femur is preserved
on underside completely, but the proximal end is obscured, whereas the
near, left side femur is incomplete proximally on the slab.
Jaime A. Headden
Little steps are often the hardest to take. We are too used to making leaps
in the face of adversity, that a simple skip is so hard to do. We should all
learn to walk soft, walk small, see the world around us rather than zoom by it.
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
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