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RE: new aspect of extinction




>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.
<snip>
>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>

This ties in with the reasoning I posted many years ago that the land   
animals with functional pineal glands survived the K-T extinction,  and   
that the animals with no ability to measure seasons other than through   
temperature changes, did not survive.   The pineal gland is a light   
receptor that measures photoperiod in many animals.  The dinosaurs of the   
late Cretaceous appear (supported so far in my research-but still   
tracking hadrosaurs and late Cretaceous Asian dinosaurs) to have lacked a   
functional pineal gland in 90% of all species checked (in text) so far.   
 I base this on the thickness of the parietal bone over the supposed area   
of the pineal gland.  The Dinosauria (UC BERKELEY Press) has been quite   
helpful in describing many species' skulls as having cartilage filling   
this area, as well.  I assume very thick parietal bones would not let   
light hit the pineal gland.  Neither would excessive amounts of   
cartilage.
 My reasoning was similar; since the pineal gland is such a primitive   
trait that has survived to today but isn't fully functional in all modern   
species, why does it still exist?  Then "What animals had them that   
survived the KT extinction?"  then "Did the dinosaurs have functional   
pineal glands?".  After some discussion on this list, I was advised to   
research more into it.  I haven't haven't spent a great deal of time   
tracking it, but so far it looks good.
]
 -Betty Cunningham
(bettyc@flyinggoat.com)