Today marks the end of a International Cephalopod Awareness Days, during which we appreciate our tentacled, bilaterally symmetrical aquatic friends. More specifically, octopi, squid, nautili, and cuttlefish (and yes, it is fun employing the rarely-used plural forms of octopus and nautilus.)

So exactly what is a cephalopod?

It’s a class of animals under the mollusk phylum, so they’re somewhat related to snails and clams. They have bilateral symmetry, which basically means one half of their body is a mirrored reflection of the other, just like us. Many can change their color almost instantaneously to camouflage themselves or to show when they’re alarmed or angry. They have tentacles, and are regarded as the most intelligent animal class of all invertebrates.

The octopus in particular has a highly complex nervous system. The majority of its neurons are found in its arms, and the arms sometimes act independently of the brain, each having its own thinking system… in a way. They can also use tools, solve puzzles, and predict the outcome of the World Cup.

Not only do cephalopods boast all these amazing qualities, many of them have been exhibiting them for hundreds of millions of years, earning them the title “living fossils.” Seems they’ve been doing something right.

In honor of our smart, squishy friends, here’s a close up with each one.

The Shedd Aquarium has two in-depth articles on the nautilus and octopus, which will definitely increase your cephalopod awareness.