Octopi are cephalopods, a class of marine mollusks related to cuttlefishes, squids, nautilus’s. They lost their carapaces in order to maneuver through tight spaces, increase their agility and their access to niches limited by their large shells (look up ammonites), though nautiluses have retained their carapace due to being survivors of an ancient lineage. The development of camouflage and mimicry is their evolutionary response to losing their ancestral shell. Their eye is reflective of the need for a panoramic field of vision to remain vigil due to predation like other prey animals hence convergent evolution. The mollusk phylum (snails, scallops clams, abalone, chitons etc) is among the most important prey items for marine vertebrates.
sidenote: had to retype this shyt so many time’s because of this flabby ass site lmaoooo