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Re: Screaming dromaeosaur biplane killers of the air
Headden and others are posting some statements that may mislead the unwary.
In the type C. pauli and M. gui (probably the same species) the distal
primaries (folded over the femur in C. pauli, not to be confused with the
more distal tibia based feathers) are actually quite long, indeed they are
longer relative to the hand in both specimens, and in that sense are closer
to the modern avian condition than is Archaeopteryx. The most proximal
preserved ulna feathers are also long, about as long as the ulna, maybe
longer - it being difficult to be exact from the photos, and there are badly
placed sediment breaks in both specimens. There certainly is no reason to
think that the innermost feathers shortened dramatically as restored in the
top view illustration, this does not happen in flying birds. When the wing
is posed in a normal flight position it has a moderate, fairly typical forest
bird chord/span ratio, and the span and area/mass ratios plot in the middle
of the flying avian range, and are similar to Archaeopteryx. The wings were
therefore fully capable of generating as much lift as modern bird wings, and
had high thrust potential as well. The large size of the wings is readily
apparent in the articulated type M. gui. To consider these enormous, fully
refined arm wings merely maneuvering control surfaces, or compare them the
dinky little, symmetrical, frayed edged feather arrays on the wee arms of
Caudipteryx, is absurd.
As I detail in DA, the Johel dromaeosaurs have a large set of arm, pectoral
girdle, and trunk adaptations for advanced flight not present in
Archaeoptryx, which itself was probably a competent powered flier, not just a
glider. In no regard are the flight adaptations of the dromaeosaurs'
forelimbs inferior (read the descriptions of the various Johel coracoids and
study the illustrations carefully).
The spherical femoral head of the type Sinornithosaurus is pictured in the
Nature description, my hi-res photos verify it. Combined with the splayed out
hindlegs of the completely articulated spread eagled sinornithosaur later
described in Nature and the presence of well developed leg wings, the burden
is upon those who wish to challange the ability of Johel dormaeosaur legs to
sprawl. Citing the condition on later dromaeosaurs and troodonts is not
pertinent since these are more derived, smaller armed, flightless forms that
had no need for sprawling, spherical femoral heads. It is called evolution,
in this case reversal (probably genetically simple) to the ancestoral
condition due to a return to the ancestoral, nonvolant lifestyle.
In all modern birds large, strongly asymmetrical distal primaries with trim
edges are always used for flight, display is at best a secondary function.
Since this form applies to the distal leg feathers the only logical
scientific conclusion is that they evolved primarily for flight, and that
display was at most a secondary use. If the dromaeosaur's leg feathers were
the same size yet symmetrical then it could only be concluded that they were
for display. But this is not the case, ergo arguing that aerodynamic feathers
were mainly for display is not logical of scientific.
Since the foot feathers could fold up relative to the metatarsus, I'm not so
sure they would have hindered movement on the ground - indeed it seems to be
an adaptation for allowing ground locomotion which most fast moving climbing
animals are capable of. So does not contradict the arboreal adaptations of
the Johel dromaeosaurs.
Biplane, for those having trouble with basic etymology, means two(bi)
wings(planes). The arrangment of the wings is not definitive. There are
tandem biplanes, staggered biplanes, and so forth.