This is just fascinating, cephalopods (or, at least, the octopus/squid branch of that class) have been discovered to do extensive RNA editing, giving them access to much more complex protein building behaviors than most creature's far less dynamic
To quote the NYTimes: "natural selection seems to have favored RNA editing in coleoids, even though it potentially slows the DNA-based evolution that typically helps organisms acquire beneficial adaptations over time."
The first two extinction events:
* 439 Mya (Million years ago) Ordovician–Silurian Extinction
** "86% of life on Earth was wiped out."
** "Trilobites, brachiopods, and graptolites died off in large numbers but interestingly, this did not lead to any major species changes during the next era."
* 364Mya Late Devonian Extinction
** "75% of species were lost"
The ancestors of cephalopods "became dominant during the Ordovician period," that is 485.4–443.8 Mya -- before that first extinction event. It seems that octopii are pretty adaptable as they are -- physically changing shape, changing skin appearance, incredibly mobile. And now the genetics of the creatures seem to be pretty flexible and mutable as well.
My mind swirls with what ifs and curiosity: Surely we have lost cephalopod diversity with the extinction events. There's no reason to believe the most smart-like-human-smart creature lineages would have survived all extinctions. The cost of those extinction events to a slowly evolving lineage would be much higher than to us vertebrates. (And plants' capacity for diversifying genetics seems much more than animals' capacity) What if there hadn't been extinction events? What would the apex of cephalopod evolution be like then?