Re: The origin of flight: from the water up (still short!)

["James R. Cunningham" <jrccea@bellsouth.net>]

David Marjanovic wrote:

> When the wings are below a certain relative size, flight is impossible.

Doesn't that depend to some extent on the airspeed?  And size relative to what?

> *Rahonavis* has longer wings than both *Archaeopteryx* and
> *Confuciusornis* in relation to both trunk length and hindlimb length (just
> checked from illustrations); in the latter 2 the tibia is the longest bone
> in the body (the plesiomorphy), while in *R.* the ulna is longest (it is 150
> % femur length while the tibia is 137 % femur length, according to the
> description), even though the tibia is relatively longer than in the other
> two animals.

Interesting.  In Quetzalcoatlus, the relative ulna length decreases as wingspan
increases.

>     - If the tail with its long rectrices was used for steering in Archie,
> it would have been rather difficult to move if it would have been longer.

I rather doubt that it's primary purpose was for steering, but it probably could
have been used for that too.  Why would it have been more difficult to move if
it were longer?  I presume you are talking about moving while in flight?

> A tail that is mobile throughout its length (except the pygostyle), as seen in
>
> "Enigmosauria" and Pygostylia, should influence manoeuverability,

Well sure, but the pygostyle region could influence maneuverabilty too, if it
were surrounded by a muscle bulb.  I don't have a clue whether that was the case
in any of these animals.

> (I can suggest a probably cheap way to do it: Take a cormorant, or
> another diving bird that steers underwater with its stiff tail feathers,
> glue an artificial Archie tail on it --

Doesn't this presume that Archie had near zero control over tail mobility?