Why didn't sharks become extinct? (fwd)

[Anthony T Hartman <ahartman@oswego.Oswego.EDU>]

  The following was posted on the newsgroup sci.bio and I think it may be
of interest to this group. Please forgive me if this is inappropriate. If
this is the case, I won't make the same mistake twice.
  ----------------------------------------------------------------------------
 |  ahartman@oswego.oswego.edu  |        A T Hartman         | Oswego State   |
 |      Agammemon@aol.com       | News Editor, _Oswegonian_  |    College     |
 | aw149@freenet.cc.buffalo.edu | "We do it all night long." |  zoology bs    |
 ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
 | "The most beautiful thing we can experience is the mysterious.             |
 |  It is the source of all art and science."                                 |
 |         --Albert Einstein                                                  |
  ---------------------------------------------------------------------------- 

---------- 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.

Does anyone know what made the sharks able to survive?

-- Anne