Fwd: Etymology

[DPterosaur@aol.com]

[This message actually came via George Olshevsky, but I thought life
 would be easier if I made it appear to have come directly from its
 original author, David Peters.  The tradeoff is that the last
 paragraph might seem confusing if you don't recognize that it was
 meant for George.  -- MR ]

I'm looking for the etymology of the following:

Petrolacosaurus = rock ? lizard
Cosesaurus = ? lizard
 
If you don't know the etymology of the above, could you please post it
to the dino group?  And say "Hi" for me.

David Peters
DPterosaur@aol.com