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Re: Cretaceous Extinction comments (long)



jamolnar@juno.com wrote:
> Sorry it has taken me so long to collect my thoughts, but I've been
> reading up on some references, looking at everyone's replies, gone back
> to the archives and various sources, and I'd like to answer (and ask)
> more questions.

I appreciate the depth of thought that went into your posting. 
 
> Betty's Cunningham's pineal idea is interesting, but how does it explain
> the shark, horseshoe crab, and other marine critters that do not have
> pineals?  

good point.  So far I was merely considering why DINOSAURS were hit when
when the KT extinction occured and had not yet moved the thought onto
many other species beyond mammals, birds, amphibians, and reptiles (all
terrestial vertebrates who had some memebers survive the KT).  I have
not yet completed my research into these particlular animals (I still
haven't found info on crocs for example-haven't looked terribly hard yet
though ....).  

I realize I need to address pterasaurs as they were also terrestial
vertebrates that became extinct and am just starting to look at and
understand basic (read very basic) pterasaur anatomy.  

Do you really think I should investigate marine animals?  I have no idea
if they even NEED a photoreceptor or would be affected by one if they
had one, since they live quite a great deal of their life at various
depths, rendering a light-measuring organ slightly (IMHO) unuseable.  I
believe the marine extinctions and survivals at the KT were probably one
of the multiple cause-and-effects mentioned so frequently in this list
and probably don't have the same reasons for extinction and survival as
land vertebrates did..

> Thus Rob Meyerson suggests that if animals awaken to a post-impact world full
> of food restrictions, more of the small-bodied individuals will make it
> through to sustain that species' reproductive diversity and viability.

and why certain species of 15 foot-plus crocs made it from the
Cretaceous into the Paleocene (ref from early discussions on this list)
(Jeff Poling's site is so handy)

> If the bottom of the ocean was a
> refuge for the crab, why didn't a few mosasaurs (and the other sea
> monsters and ammonites) make it too?

again, I haven't addressed marine animals.  Maybe because the crab could
come on land and the others couldn't?  Haven't the foggiest idea about
sharks' survival.
 
> "Physiological dependency upon seasonal changes in light levels is the
> one common link that dinosaurs, angiosperms, corals, sponges, bryozoans,
> etc. have in common, and it was this one factor that was the primary
> cause of the Cretaceous mass extinction."   If this is true, why are the
> dinosaurs the only taxon in that sentence that didn't make it across,
> while some representatives of all the others did?  And what of all the
> other critters with dependency on seasonal changes in light level that
> made it too (birds especially)?  This can't be the only answer.

Right, my point is that most late Cretaceous dinosaurs COULDN'T make use
of a photoreceptor.  The modifications of most late Cretaceous
dinosaurs' parietal bones (which I assume to be over the pineal gland)
don't seem to allow for aid in it's functionality.  I need to address
the same area in pterasaurs, who also became extinct, and (INITIAL
RESPONCE ONLY-NOT YET INVESTIGATED) seem to share much of the LC
dinosaurs' inclination to wacky head crests, frills, bells, and whistles
that may also render the pineal gland's ability to measure light
effectively unusable.

> Michael Teuton raises lots of important questions about the impact's
> effects in the oceans.  I too haven't seen any numbers crunched as to the
> effect of this asteroid's immediate impact on ocean temperature, acidity
> or chemistry.  Could the chemistry of the ocean been so changed it
> affected the ability of marine animals to either a) build their
> exoskeletons/skeletons, b) have their remains preserved, c) obtain
> untainted food or d) breathe? How would the amount of dissolved oxygen in
> the ocean be affected by the impact?

Recently at the Cal Paleontology Conference at UC Berkeley, a student
talked of his preliminary work with paleofloriminifera (fossil planktons
and diatoms) in learning surface temperature changes of paleo-oceans by
examine growth rates of contemporary and extinct floriminifera with a
formula based on growth during light exposures (His study is based on
exposures due to depths of the creature, but I feel it may play an
important part in telling us the weather, as well).  This might help
when his studies are complete.  These life-forms can measure changes in
hour-long rates as they frequently add new chambers to themselves in
four-hour periods.  They are very specific measuring devices.  So are
fossil corals in measuring fossil temperatures and chemical changes. 
Many paleontologists feel that a "de-oxygenating event" such as that
when the lower, unoxygenated areas at the extreme depths of the ocean
reverse with the oxygenated areas nearer the surface as might occur with
a large asteroid impact in the ocean, may have happened at the KT.  

Maybe horseshoe crabs survived because they are capable of breathing
atmospheric air?  Maybe the other marine invertebrates that didn't
survive couldn't?
 
> And if the ocean became acidic due to acid rain fallout, so would the
> fresh water on land, and what about all the freshwater animals (like
> amphibians) that made it through?

probably didn't happen to the extent that acid rains are happening
currently.  Evidence against nastier acid rains is suggested by that
very reason-amphibians survived.

> If we can match
> an idea that explains the dinosaur's demise PLUS the marine plankton's
> selective extinctions, I think we'll have it.  We don't yet!

I still feel that there were multiple reasons for the extreme extinction
rate during the KT event.  My pineal gland theory is merely one in a
whole pile of factors that could be considered at the time. 

> Being this is a wide
> range of unrelated bird species, and bird sizes, a hibernating dinosaur
> is not out of the question, 

I am not addressing the 'hibernating' dinosaur theory.  I leave that to
somebody else.

> Stanley Friesen suggests that most birds do not hibernate because they
> CAN migrate; it is easier and more convenient for them to do so.

and they know WHEN to migrate in part due to photoreceptors.  This is
still helping my theory.
 
> The Cretaceous mass extinction was VERY selective.  Maybe all our
> theories are correct, but not for every species or taxon.  I guess all
> this discussion leads to one conclusion: there is no ONE cause for (or
> theory to explain) all the K-T extinctions!

well said.
 
> Now, I feel I need to vent here, being the person who started all this
> recent extinction talk. 

also well said.
-- 
           Betty Cunningham  
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