Mollusc and fossil

[curioucity]

Will Molluscs leave fossils when they die?
I know the answer is yes for those with shells like snail, but what about the ones without, like squids, octopuses, shell-less slug?

 

[river-wind]

Octopi have in a internal skeletal structure, which, under the right conditions, could become a fossil. Infact, nearly any tissue can be fossilised, either through a process of replacing the organic matter, molecule by molecule, with inert componants such as rock, or through a imprinting process, where a patterned imprint of the tissue is made in mud, which hardens to rock. The former gives fossilised bones to look at, and is largely special to animals with solid material (which doesn't bio-degrade quickly), the latter can occur with any material, from bacteria to full-sized dinosaurs to trees to algea.

 

[curioucity]

Really?
wait, here's a question:
If a creature (animal preferably) were to be drown in mud, could it be fully fossilized with all its organs preserved (dead)?
And by the way, I just want to know too if there exists prehistoric octopi or squids or whatever fossils.....
And about what you said, surely that applies to Coelenterata (such as jellyfish) too right?