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new aspect of extinction



 From: David Pelly
 To: M.Brett-Surman, Smithsonian Institution.
 Date: Thu, 30 Jan 1997 23:03:54 -0800
 From: <jenauld@gate.net>
 Subject: another aspect of extinction theory
 Content-Type: text/plain; charset=us-ascii
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 I have been given permission to post this file to the DinoNet. please
 respond to Mr. Pelly Off-line at <jenauld@gate.net> with the phrase
 TO MR.PELLY in the subject line. Thanks.

 *****************************************

 My name is Dave Pelley, and I am a supervisor in the Education
 Department at Sea World of Florida.  I hate to take any of your valuable
 time, but I could use your advice.
 Quite by accident roughly two years ago I stumbled upon something that
 may be signifigant regarding the Cretaceous extinction, and I have been
 quietly researching it on my own time (out of both curiosity and
 boredom!) since then.  Its kind of crazy, and it had absolutley nothing
 to do with dinosaurs originally, but I have come to the realization that
 there is the slightest possibility that there may be some validity to
 this idea.
 Before I go any further, let me state clearly that I have no motivations
 other than the satisfaction of my own curiosity, and that if anything
 were ever to come of this at this point I really wouldn't want anything
 to do with it.
 <snip> ,let me give it to you in a nutshell:
 I believe that for some reason (asteroid near miss perhaps), the
 seasonal photoperiod lengths of the Cretaceous period were suddenly and
 drastically altered 65 million years ago, such that all organisms
 directly affected by photoperiod or those that lived in a tightly-knit
 food chain with organisms directly dependant on photoperiod could not
 adapt and were therefore selected against (talk about a run on
 sentance!).
 <snip>  let me explain my reasoning.
 I actually came across this idea one day while thinking about penguins
 and their dependancy upon photoperiod.  Being the odd biological type
 that I am, I was wondering to myself how much someone could "monkey
 around" with the penguin's photoperiod before they would finally cease
 exhibiting reproductive behavior.  From there, it just kind of dawned on
 me that this might be the crucial link that explains why certain plants
 and animals were selected against at the Cretaceous Extinction, while
 others were not.  In fact, by creating a simple chart representing (in
 broad terms) the organisms alive today, a drastic and sudden change in
 seasonal light cycles would result in an almost identical mass
 extinction.  This explains why some seemingly hardy species went extinct
 (dinos), and why other "delicate" species (like tropical frogs) did not.
 As we both know, being dependant upon seasonal light cues is not a
 "weakness" at all, it in fact makes good evolutionary sense.  If you let
 the seasons dictate when you do certain high-energy activities, you have
 alot of extra time to save/store/obtain energy the rest of the year.
 Its a great strategy that should work because seasonal light cycles are
 relatively fixed.  What are the chances of an asteroid near misiing the
 planet and changing our light cycles anyway?  A billion to one?  It is a
 good strategy that many ectotherms utilize, but it really cost them 65
 million years ago when the "impossible" happened.   Obviously, I am kind
 of biased at this point, but no other theory explains the selectivity of
 the marine and plant extinctions as well as this idea.  Organisms that
 were not sensitive to photperiodic cycles were fairly unscathed by the
 mass extinctions, while the sensitive species were wiped out.  Further,
 a change in photoperiod would not neccessarily involve a signifigant
 temperature change, either (although it probably did).
 <snip> I think
 that the iridium layer is evidence of a meteor/asteroidal bombardment.
 Although most have pointed to an impact as the cause of the extinction
 (and I have no doubt of the bombardment), I feel that it was the one
 that missed us that actually did the damage.  The gravitational effect
 of a really big asteroid just missing us would be enough to cause a
 slight "wobble" of the earth on it's axis, which would explain the
 sudden and drastic change in the seasonal light cycles.  The effects of
 this, of course, would be catastrophic.  Dinosaurs would be waiting for
 light cues cues to induce migration and/or breeding that would never
 come, or they would have had a total change literally overnight of the
 seasons as they knew them (thus disrupting nesting, migration, etc.).
 Photoperiod change explains the "fern spike" at the end of the
 Cretaceous, and the temporary decline in angiosperms.  It explains why
 corals were selected against, but most fish were not.
 Ok, that's it.  This is the simple, condensed version and I appreciate
 you taking time to look at it.  If there is anything to this idea,
 please advise me as to what to do.  I have amassed a large file of info,
 but I'm done with it and ready to "move on" to other things that I am
 interested in.  Do I just file it away as a neat hobby that gave me
 something to do in my spare time for a couple of years, or is there some
 validity to this?  If it would help someone out, they are more than
 welcome to have what I have compiled from my resources.
 Again, thanks for your time,  I realize you probably get stuff like this
 all the time, so I appreciate your patience.
 This theory has spurred some lively
 debates with all my biologist-crony friends down here, but most were
 pretty open to it.  Hope it made for some good reading!
   Dave Pelley

Mike Brett-Surman    brett-surman.michael@nmnh.si.edu
or at mnhpb018@sivm.si.edu
Smithsonian Institution (not "institute" ;-)