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RE: Who says dromaeosaurs can't fly?
In a message dated 9/13/2 2:34:15 PM, TiJaWi wrote:
"In the secretary bird (_Sagittarius
serpentarius_) the greater length of the legs relative to the wings is due
principally to the extraordinary elongation of the distal hindlimb. This
bird spends most of its waking hours walking on the ground, stalking
terrestrial prey. As a neornithine bird, the femur is largely decoupled
from stride generation, and so it falls to the distal hindlimb elements to
provide the bird with an elevated sensory platform.
BTW, I'm not necessarily contradicting the idea that _Cryptovolans_ was
volant. I just think comparing dromies with modern cursorial birds is
apples and oranges. Both have vastly different evolutionary pedigrees."
As I noted in my post, the hindlegs of Crypto are longer relative to the body
than Archaeopteryx, which helps explain why the leg/arm length ratio is
higher than Crypto even though the wings are the same size in the two
animals. That there are modern avian flier with legs longer than the arms
shows that this feature in Crypto does not challange its flight status.
"is the presence of "robust, flattened
central finger and bowed metacarpals" necessarily due to powered flight? I
know the ecomorphological rationale: These features allowed firmer
attachment of the primaries so as to better resist torsional forces during
However, the suite of features seen in this array of dromies can also be
explained by less demanding forms of aerial locomotion: i.e. gliding and
parachuting. If these same predators continued to use their forelimbs for
the capture and processing of prey (such as in the "death from above"
scenario you mentioned), this could provide a selective mechanism for a
stronger attachment of the primaries to the forelimb skeleton - particularly
in the manus/carpus region. The dino-bird wouldn't want its primaries to be
detached by struggling prey."
The wings of Crypto are as big as those of birds, the sternal apparatus is
far advanced above that of Archaeopteryx and so forth. There is no evidence
it was a mere glider. Since Archaeopteryx lacked finger flanges despite its
very large, fully developed wings, gliding predatory avepods basal to
Archaeopteryx certainly did not have finger flanges.