[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
RE: Archaeopteryx running & CNN report on the feathered dino
Jim Cunningham wrote:
> More seriously, once you develop an effective supracoracoideus, you no
> longer need the cursorial ability (this has to do with landing, not
> with trees down or ground up theories). And once you develop the
> you no longer need the hand to assist with vortex control during
Again, this is assuming an overriding selection for improved flight
ability in early avian (and "pre-avian") evolution - up to and including
_Archaeopteryx_. What if the first birds retained good-running ability
so they could chase down prey on the ground? What if they had grasping
hands so they could grab prey?
I'm not disagreeing with your aerodynamic interpretations; the use of
the appendages in ground-level predation is not mutually exclusive with
an aerodynamic function. However, there is the possibility that the
reason why _Archaeopteryx_ has a grasping manus, cursorial hindlimbs and
long tail is for the same reasons that its ancestors did.
>Why do aerodynamic benefits have to be limited to higher, longer, more
Oh, they don't have to be limited to this. I was continuing on from the
premise that *if* incipient aerial behavior took the form of
prey-catching leaps, then there might be good reasons for retaining the
ancestral maniraptoran body plan - at the expense of better aerodynamic
abilities. I'm not arguing this is the *only* possible behavior that
could have given rise to flight.
>What is there about Archaeopteryx anatomy that indicates that it was a
>particularly inefficient or ineffective flyer?
Puny sternum. Lack of a supracoracoideus pulley system (as you note).
I don't dispute that the frond-like tail could have acted as a sort of
"third wing" for the legs. But you must admit - the long tail is pretty
David Marjanovic wrote:
> >The specimens of _Archaeopteryx_ do not show hindlimb feathers
> >some early interpretations).
> What else are the contour feathers on the shins of the Berlin
I didn't know about tarsal feathers in _Archaeopteryx_. Are you
>Don't know about tertials, but many contour feathers on the body of the
>Berlin specimen were _prepared away_ to reveal the bones. Read more in
><duck and cover> Feduccia 1996.
I don't think this issue has been settled beyond reasonable doubt.
However, I am aware that some early sketches of one of the
_Archaeopteryx_ specimens do show contour feathers (can't remember which
one - was it the Berlin specimen). But this doesn't hold for *all* the
_Archaeopteryx_ specimens. If one Archie specimen did preserve contour
feathers, then it's exceptional in this respect.
>I think because they don't retract their legs when they fly; to
>drag, they have streamlined shins, in analogy to aeroplanes with fixed
Other birds have leg feathers too, such as some owls and sandgrouse.
Maybe they're used as leg warmers?
Timothy J. Williams
Iowa State University
Ames IA 50014
Phone: 515 294 9233
Fax: 515 294 3163