[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Arms into wings



Tom appears to be right.  And Kathleen Earl has measured starlings and quail
launch performance on force tables, and found that they, like most other birds
achieve about 80-85% of launch energy with their legs (in this case, by leaping,
not running).  Archie's legs were capable of similar performance, and perhaps
similar take-off technique, with a horizontal velocity sufficient to minimise
the need for the sc's contribution to flapping frequency (and thereby to the
power to weight ratio).
Jim

Thomas R. Holtz, Jr. wrote:

> At 05:20 PM 3/2/99 -0500, Patrick Norton wrote:
>
> >I guess I'm suggesting that overall function of the arm and hand as prey
> >capturing devices must have been compromised over time once selection
> >began acting to improve aerodynamic performance.  If you are running
> >after a dragonfly and flapping, you can't also be grabbing for it with
> >your hands-- at least not without breaking the flapping rhythm.
>
> EEEEeeekk!!!
>
> (I didn't just read that, did I?)
>
> The "chasing a dragonfly" model is about as dead as _Archaeopteryx_.  No one
> I know of considers that a likely life habit: heck, even Ostrom was only
> partly serious when proposing it.
>
> Archie would presumably be going after more substantial game (lizards,
> sphenodontians, etc.), and dromaeosaurids much more substantial game (other
> dinosaurs).
>
> More to the point, as Padian & Gauthier showed back in 1985, the predatory
> strike of a eumaniraptoran forelimb uses the same basic movements in the
> same sequence as the flight stroke: it would be a synchronized movement.
>
> >The
> >process involved a fundamental shift in the function of the arms and
> >hands from prey capture to flight. The carpometacarpus was simply the
> >coup de grace.
>
> Yes, and the carpometacarpus doesn't appear until well up in birds (after
> Archie and _Confuciusornis_ split off from other birds).
>
> Thomas R. Holtz, Jr.
> Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
> Dept. of Geology              Email:tholtz@geol.umd.edu
> University of Maryland        Phone:301-405-4084
> College Park, MD  20742       Fax:  301-314-9661