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RE: Birds vs. the pterosaurs



From: John Bois (Tuesday, February 06, 2001 6:22 AM):

>A striking bias appears in many posts on this subject: unwillingness to
consider mundane causes--such as predation and competition--for
extinction (i.e., forces that are routine in modern ecologies)because 
of a lack of paleo evidence; and a willingness to embrace fantastic
causes--such as bolide--despite a lack of evidence connecting extinctions
to such an event.<

[snip]

>And, it may well be that forces at work on land were different from those
operating at sea.  After all, terrestrial extinctions are not known to be
synchronous with marine extinctions.  Indeed, rough synchronicity between
these biome-level events may be cooincidental or indicative of
causation--unfortunately there is, as yet, no way of knowing which.  With
all deference, we just have to suck it up.<


I have to say first that what is fantastic to one person may be mundane to
another.  Bolide collisions are, after all, known to occur and are therefore
just as mundane, even if episodic and catastrophic, as competition, etc.


Then, Ronald Orenstien wrote (11:58 AM 06/02/01):
>At 10:26 AM 06/02/01 -0600, Demetrios Vital wrote:
>>The breathing abilities of the animals at the end of the Cretaceous is, in
my mind, a more than major explanation for the extinctions of the respective
families.  Non-avian-dinosaurs and pterosaurs had less efficient breathing
systems than birds.<<

[snip] 

>In short, without the physiological information we need we can only guess 
at how effective Mesozoic reptiles were at gas exchange, or at dealing with 
oxygen stress, and therefore -- since we cannot establish the differences 
among different forms with any accuracy -- this is useless as an 
explanation for extinction.  At the very least, before you can claim that a 
difference among taxa explains why one group survived and another did not, 
you have to be able to prove to that difference really exists.,


At various times on the list we have discussed "just-so
stories"--interpretations that make sense but which we really can't document
scientifically.  Of course Ron is right, and so is John Bois.


Darren Naish wrote (6:45 AM 06/02/01):
>Pterosaurs and birds probably didn't compete directly, but as 
pterosaur lineages died out, their ecological roles may have been 
occupied by birds. So-called competitive replacement is probably rare 
(see Benton 1996).<


In view of how complicated physiology and ecology can be, I don't see how we
can say this.  I know it is essentially impossible to document any
particulat example of competitive replacement.  The only extinctions for
which we know the certain cause have happened in the last few hundred
years--we saw it happen.  This does not mean that competitive extinction or
perhaps overpredation by an agent other than Man has not occurred, just that
we can't prove it.  However, they remain likely explanations for any number
of extinctions.  But they are just-so stories, just like most every other
interpretation we make.  Basically, then, all of our explanations are
useless.

Well, do we want to make interpretations or not?