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Re: postulated bird/pterosaur competition... with a little HUMOR (?) at the end :o)



    Concerning pterosaur extinction, it seems to me that Jim Cunningham has
hit a very important nail squarely on the head  in telling us:

    "For soaring animals, there are several distinct techniques and methods
for extracting energy from different types of atmospheric dynamics.  Access
to
these specific energy sources is dependent upon planform, aspect ratio, and
wingloading among other things.  Should atmospheric dynamics change faster
than a species is capable of morphing to accomodate, that species will
disappear."

    Even before the K/T cosmic impact, one might suspicion that atmospheric
temperatures, 'jet streams', or major weather-pattern steering currents may
have been substantially effected as a result of the massive output of
volcanic debris into the upper atmosphere by the Deccan Traps. Those effects
could even have been global in various degrees, and I wonder if especially
the changing wind patterns, velocities, localized wind-shear effects, and
temperature changes might have caused, for example, survival problems for
many pterosaur species appreciably before the K/T terminal event.

    In situations of wind extremes, I suspect that an 'Achilles tendon' in
the pterosaurs might well have been the very long, slender, digit IV 'wing
finger'.  As an adaptation facilitating flight, that item was extremely
thin-walled and hollow, and served the function well in environments to
which it was suited. But when winds became very extreme and turbulent it is
not wild speculation to think that many 'wing fingers' could have become
broken in flight, spelling certain doom for the unfortunate pterosaur. (A
wind-induced tear in the flight membrane would have been less likely, I
suspect, but still potentially fatal.)  It seems to me that the wings of
birds might be much less vulnerable. What say you, Jim Cunningham?

    John Bois, please note:  That kind of failure of a species, or even an
entire clade, has NOTHING to do with competition and everything to do with
lack of adaptation to drastically altered weather across a time period too
short for adaptive change to have occurred, just as Jim Cunningham
mentioned.

    The situation was vastly the more-so if there were any pterosaurs,
anywhere, that somehow survived the initial devastation of the K/T cosmic
impact, per se.   Drastically altered oceanic and atmospheric currents would
have continued for very long periods, and attendant wind strengths and
directions (to say nothing of acid rains, temperature changes, etc. and
likely the disappearance of most if not all the pterosaurs' prey from the
environment to which it was adapted) would undoubtedly have finished off any
straggling pterosaurs. Considering those circumstances, it seems ludicrous
to suggest that competition with birds was the culprit!

    John Bois, could it be that in your childhood, you watched Hitchcock's
THE BIRDS and it was just too much for you to handle?  :o)

    Sorry, John, I just couldn't resist.

    But I personally think your idea about pterosaur disappearance due to
bird competition is, well, for the birds! (Pun intended.)

    But, WAIT folks!  Now let's see...huuummm...if John's middle name should
be VOGEL, with a family name like BOIS, that would make him John BIRD TREE!
Ah!  That might account for his tenaciously holding to ...   :) ...but a
German bird on a French tree?  Nah!

    Anyhow, at least in my analytical 'tree', the bird competition idea
simply doesn't perch, for the reasons described earlier, herein, and a host
of others.

    Ray Stanford

"You know my method.  It is founded upon the observance of trifles." --
Sherlock Holmes in The Boscombe Valley Mystery

----- Original Message -----
From: "James R. Cunningham" <jrccea@bellsouth.net>
To: <john_conway@mac.com>; <dinosaur@usc.edu>
Sent: Monday, July 15, 2002 5:02 AM
Subject: Re: ...bats by day, and bats, birds, by night.