Re: Paedomorphosis ( Re: BARYONYX' CLAWS )

[Ronald Orenstein <ornstn@inforamp.net>]

At 11:39 PM 11/04/98 -0400, you wrote:
>In a message dated 98-04-11 22:08:49 EDT, m_troutman@hotmail.com writes:
>
><<  Well, if you define it that way... a person's terminology is 
> different from an another person's. Controlled leaping is seen in 
> kangaroos, kangaroo rats, grasshoppers, monkeys, and other creatures, 
> not your typical fliers. I call arboreal gliding; arboreal gliding and 
> flapping flight; flight. >>
>
>Not aerodynamically controlled leaping.

May I suggest (with some trepidation as I have watched this argument develop)
that a lot of this discussion is about semantics?  Who really cares whether
what we are talking about is "flight", "swimming", "gliding", "controlled
leaping" or whatever?  From an adaptive standpoint none of this matters.  What
does matter, I suggest, are questions like:

1.  To what extent are the forelimbs used in locomotion (in any medium)?
2.  To what forces are these limbs likely to be subjected during the course of
this locomotion?
3.   What sort of structural adaptations exist to deal with these forces?
etc.

Thus the penguin issue really is not "do penguins fly underwater" but "what
are
the modifications made to the penguin forelimb structure" or, to fit the
paedomorphosis argument, "what features in the wing of volant birds usually
lost in flightless ones are retained in penguins, and to what extent can this
be explained by similarities in the way the forelimbs are used?"

As far as "controlled leaping" is concerned, remember that many of the animals
that appear to be able to do this do so with structures that may not be
apparent in fossils: elongated hair on sakis, extended toe webbing in "flying"
frogs etc.

Which brings me back to my other frequent point:  until we actually have good
fossils of some of the early "protobirds" we are talking about any speculation
on what these critters were doing seems idle, and in any case ignores the fact
that they may have been doing all sorts of things using adaptations that
either
do not fossilize or are so slight in their differences from ancestral
conditions that they might be exceedingly difficult to recognize, let alone
interpret in any functional way.  Thus, unless a fossil shows up that is
both a
clearly and considerably specialized volant or near-volant form and obviously
represents an ancestor to both birds and at least some theropods, the
"difference" between BCF and BADD may be minimal, unimportant or impossible to
distinguish.
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@inforamp.net