Re: Why didn't sharks become extinct? (fwd)

[Stan Friesen <swf@ElSegundoCA.NCR.COM>]

 > 
 > ---------- Forwarded message ----------
 > >From: anne@quilty.Stanford.EDU (Anne Paulson)
 > >Newsgroups: sci.bio
 > >Subject: Why didn't sharks get extinct?
 > >Date: 8 Nov 94 16:53:22
 > >Organization: Stanford University
 > 
 > The other day, my four-year-old son asked why sharks didn't disappear
 > after the comet crash that did in the dinosaurs (the K-T crash).  We
 > researched the question at the library, but couldn't find the answer.
 > We did find that apparently every land animal weighing over 10 kg was
 > wiped out, and that there were marine extinctions of some very small
 > animals, but we didn't find out why the sharks were able to survive.
 > It must have been the same toughness that enabled them to survive the
 > mass extinctions 250 million years ago.
 > 
One suggestion has already been made, however I have another
perspective.

First, until the real dynamics of a mass extinction are worked out,
the decisive factors can only be hypothesized.  Since it is still
somewhat uncertain as to exactly how much of the extinction was
due to the meteor (probably NOT comet) impact, and how much was
due to other factors, making conlcusions on the assumption of
a primarily impact derived extinction is premature.

Now, why the caveats?  Because if the alternative model is correct,
and the extinctions had already started at the time of the impact,
then the impact probably mainly effective groups already in decline.
This opens up the possibility that the reason the sharks were not
effected is they were not in decline.

Of course this only moves the question back one notch, to
why were the sharks relatively unaffected by the factors that
were causing widespread decline in other groups?

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

The peace of God be with you.