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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

flapping flight.  


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. 

G Paul