You might think that “living fossil” is a bit of an oxymoron, however you’d be mistaken. To be considered one, the living organism in question must more or less maintain the same anatomy and behavior over millions of years while watching the rise and fall of many other still-evolving species.
Somewhere on the cephalopod’s evolutionary journey from snail to octopus sits the Nautilus; which has changed very little in the last 500 million years. At one point, the oceans contained hundreds of different types, but nowadays only six remain, all of which are found along the deep slopes bordering Indo-Pacific coral reefs. Like the squid and the octopus, the Nautilus has tentacles, but many more of them that lack suckers. It also lacks the complex central nervous system of its advanced family members and has been shown to have a much poorer memory in comparison.