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Re: paleontolgist, dinosaur



From: John Bois <jbois@umd5.umd.edu>

 > On Fri, 8 Nov 1996, Stan Friesen wrote:
 > > The volcanic eruptions probably effected global climate, and perhaps
 > > induced extensive acid rain world-wide.
 > 
 > Which would not have targeted dinosaurs specifically I don't think

True, but there is precious little evidence that the extinctions
did target te dinosaurs specifically.

 > Loss of habitat variety affects _all_ creatures.

Only those that are restricted in habitat.  Widespread species
would be less affected.

 > > The effects of the impact have been well covered elsewhere.
 > 
 > Yes, but how it impacted dinos is speculative only.

Those effects are such that many diverse animals would be affected,
dinosaurs would be no exception.

 > In _Dinosaur Extinction and the end of an era: what the fossils say_, 
 > Archibald gives marine regression the most blame for killing dinos off.
 > ... At first glance this seems reasonable.  But let me say the 
 > same thing another way: Neither in what is now Africa, nor Australia,
 > nor Antarctica, nor Europe, nor Asia, nor on any Komodo-like island 
 > sanctuary, in none of these places was there habitat enough to support 
 > one dino species.  I just find that very hard to believe.

That is why I go with a multi-causal model.  No *one* cause is sufficient
in itself to explain the full pattern of extinctions (note, the full
pattern is critical - not just the dinosaur extinctions).

 > > I suspect that the changes
 > > in mineral and oxygen cycling might also effect climate and land
 > > ecology (by changing the limiting resources for plant growth, for
 > > instance).
 > 
 >      But having a long list of suspects doesn't mean you've solve
 > the crime.

When there is evidence that no one suspect could have done the job
alone, as Greg Paul points out, and when there is substantial evidence
for the presence of ALL suspects at the scene of the crime, it is
reasonable conclude that there was a conspiracy.

 >      How many angels can dance on the end of a needle?

The point was that trap-style volcanism, oceanic anoxia, sea level
low stands, and climatic cooling are all *correlated* with mass
extinctions.  That is two or more of these factors co-occur with
almost all known mass extinctions, even such relatively minor
ones as the mid-Cretaceous extinction. The two with the *highest*
correlation with mass extinctions are trap-style volcanism and
oceanic anoxia.

So now we not only have the suspects present at one crime scene, but
the *same* suspects present repeatedly at other crimes of the same type.

swf@elsegundoca.ncr.com         sarima@ix.netcom.com

The peace of God be with you.