From PBS, you will enjoy this scientific exploration of fossils and why there are no squids!
They recently discovered why there are octopus fossils, but no squid fossils.  Turns out that squid can retain exhaled ammonia and use it to compensate buoyancy - and because the retained ammonia changes the pH of their tissues, it doesn't fossilize at all well.  Note that it's the ammonia that Koi breath out that lowers the pH of the bag water when shipping and allows the Koi to survive. Interesting adaptations of different aquatic species and ammonia!
 
It might surprise you but cephalopods have a pretty good fossil record, with one major exception. If squids were swimming around in the same oceans as their closest cousins, where did all the squids go?
 
Where Are All The Squid Fossils? - YouTube
These are the reference papers:
https://docs.google.com/document/d/1nVloxXDBmOY0Gz-qokbs7l9235KEG-aY-QH1...
<https://docs.google.com/document/d/1nVloxXDBmOY0Gz-qokbs7l9235KEG-aY-QH1...