Art,
 
Actually, you can get some pitch change while playing a shell.  If the
player has a bit of trumpet or similar instrument background, he or she
can get some interesting sounds out.  Some of your dying dinosaur stuff
plus other notes.  When I was a kid (and played the trumpet) I had a
queen conch with the tip ground off to use as a horn.  I found the
easiest sound was the low to high pitch, fog horn type thing.  I fear
that after all of these years, any sound I could manage would be worse
than your dying dino.
 
Tom Eichhorst in New Mexico, where we call people by yelling, "Fresh
green chile!"