How the Squid Lost Its Shell

Published on Apr 17, 2018
The ancestors of modern, squishy cephalopods like the octopus and the squid all had shells. In ancient times, their shell was their greatest asset but it eventually proved to be their biggest weakness.
Special thanks to Franz Anthony for the beautiful cephalopod reconstructions. You can see more of Franz's tremendous work at
And thanks as always to Nobumichi Tamura for allowing us to use his wonderful paleoart:
Produced in collaboration with PBS Digital Studios:
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  • Coleoids are incredible creatures. They're incredibly intelligent, incredibly adaptable, and incredibly tasty!

  • I'm sorry.... all I can think of is Calamari with Marinara Sauce.....

  • Was anyone else surprised that Nautilus was not an extinct species and is in fact, a modern day squid? Like seriously

  • I took it

  • I think Eons videos in general are fantastic and I watch old ones when I have free time. However this was one of your very best, partly because cephalopods are about the most interesting of all species to me. And now Nautiloids. Please do more on the amazing family here. For other topics, I would think more on making chemistry more understandable to the average person - I was 40 before I really got a clue on how chemistry makes the world, and not simply through the Haber-Bosch process. Thank you.

  • John Green works for PBS?

  • The correct plural of octopus is octopodes, not octopuses.

  • Who the f is Hank?

  • Video on the jawed fish of the Devonian !

  • 🐙

  • Bring on the cephalopods man😎👌🏽👍🏽

  • octopuses will continue evolve and be smart enough to drive soon. too bad self driving cars will a steal their dream away.

  • How about the history of arthropods including the eurypterids, crustaceans and others?

  • I would like to know how you know about these events that killed many species. What kind of trail did those events leave so you could ve able to identify them? And how do you do that?! I love the channel by the way

  • How recent did the ship land that brought octopus here? With their stylus. LOL

  • 3:43 looks like a loaf of tiger bread.

  • Stay fresh!

  • Why did it take until 2018 for this video to exist? awesome work I love it thank you a lot

  • I'm glad and surprise to not find any creationist in the comments section.

  • does that mean that humans will go through the same?

  • Came for the squids, stayed for the Hank Green

  • @6:43 "the same event that killed the non-alien dinosaur"... what about the alien dinosaurs, were they oki?

  • *That* explains the awkward Bill Cipher head shape.

  • *Splatoon memes*

  • Gotta love how the squid at 1:04 is blurred like it's nsfw

  • do you have one on the evolution period, cambrian and so on simplified?

  • Thanks

  • It's like the transition from wearing full Havel armor to being close to absolutely stark-naked.

  • “Octopuses” 6:15

  • "your channel is super awesome!!!" - my 4 yr old Thanks !

  • Lord helix

  • By one who knows

  • i thought that shell on the thumbnail was a karambit

  • Can you do a story about limestones and chalk?

  • Suddenly I'm in the mood for some fried calamari.

  • 😇

  • Hank said that all cephalopods used to have shells. How do we know that? If there were cephalopods without shells, they wouldn’t have fossilized, right?

  • But they can't out smart us heh heh >:D

  • Is that Hank Green?

  • I mean it's interesting, but let's be honest here, a lot of this is just guessing. It shouldn't be stated as fact. Sure there's the fossil record but it's not like it's 100% complete, you can't actually observe the animal in action. And some these fossils are exceptionally rare, maybe only two or three examples of the species have ever been discovered. Just not a big enough sample size to rule out coincidental characteristics. Can we construct very reasonable and entirely possible scenarios from highly specific observations? Yes absolutely. Having never observed the actual scenarios taking place on more than just a correlation basis, is it reasonable to state these predictions as fact? No. It's not that we shouldn't discuss it, but we really need more to go off of before these things become accepted facts. Because "Scientists" or a magical sounding word for a university employee that studies material samples along with the observations and reasoning of others like them, are humans. They're normal people with mostly normal lives just like you and me. It's media outlets like this that cloud that into a mystical image of something very abstract, which has very little to do with what these people actually think and do in real life. When really it's quite straightforward. There's no magic in science, there's no abstract in biology. There are things we know, and things we guess are probable based on what we know and/or want to believe. All great topics, fascinating ideas, very real possibilities, we just can't loose sight of the difference between the two.

  • well, war, war never changes

  • Siphuncle is fun to say.

  • because shelled squid is ugly

  • so the humbolt is not a squid ?


  • Too bad all the animals from the Cambrian just show up with no precursors or transitional formsor we might know where they came from.

  • They floated out to the upper ocean, then several million years later decided against it. GG evolution

  • awesome channel. subscribing

  • Love squids and octopuses!

  • Great. Could be a bit slower for the likes of me- the general public not conversant with biology. Thanks anyway.

  • squids are so amazing.. cuddlefish especially.. its like they are from another planet..

  • What do you know on the setup of DNA-RNA-Protein sequence? Do you think "Membrane-first" or "Duplication-first" is a more like scenario? In both cases - how do you think could the synthesis of membrane components start?

  • YUMMY!

  • its weird how learning just out of interest is so much more fun than being forced to learn something

  • Brilliant

  • I thought Sci Show had a different intro? Hank what are you doing here? Lol

  • There are fish that can turn invisible in the water I don’t me camouflage I mean invisible, I want to learn about them, please.

  • I didn't understand one word but it sounded cool.

  • So squids are the real sea slugs rofl

  • Am I wrong for watching the whole video and kept going "mmmmm calamari"

  • Do vid on the evolution of hibernation 👌🏼

  • 6;44 do I hear “non-aliendinosaur”?

  • Learn a lot. Thanks!

  • Fantastic video, really well researched and very nicely presented. Two thumbs up! I only wish you'd managed to squeeze in the enormous and uber-fascinating Parapuzosia seppenradensis somewhere... :)

  • Amazing, truly amazing.

  • Took me a moment to recognize the guy from Crash Course.

  • Finally they buffed Nautilus

  • It seems the tables have turned.

  • Eon: teach us about coral fossils, please. I don't understand how such slow growing organisms have survived so many catastrophic events when so many others, particularly the ocean dwelling, have gone extinct.

  • 4:48 PRAISE HELIX!

  • Why is this so familiar, almost as if we humans had experienced all of that in a different order in only a few thousand years... The pioneers = pilgrims, arms race between the fish and the cephalopods = Cold War, and a few other things, the mass extinction = world wars and the before and after, something about it is repeating in short amount of time...

  • Bears 🐻

  • Omanyte in pokemon

  • My boy Squidward went from getting gas to taking orders.

  • How do you go from molusk to jawed fish with hyper maneuvirability and scales??

  • I would love to learn more about the octopus and it's possible connection to 'alien' dna?

  • Splatoon Lore

  • 0:14 awww look at that little guy, little did he know he would evolve to become the greatest fear of all Japanese school girls

  • If i knew Hank hosted some of this channel's content I would've clicked on this video alot faster.

  • Plus they're very tasty!

  • Best video for drinking game! Difficulty levels: Easy: “mollusk” Medium: “cephalopods” Expert: “ shell” Hardcore: “ every hand movement”

  • Is the gladius named after the sword or is the sword named after the gladius ?

  • Watting a stupid splatoon comment

  • Here because of Splatoon

  • Absolutely engaging and educative. Epic. We'd like to see more about the Devonian period and the creatures that lived there. Additionally, mosasaurs and the food web that existed back then.

  • Beautifull

  • What was that Pokémon again?

  • I didn't know Hank was on PBS as well!?

  • All hail our tentacled overlords

  • If coeliods learned to live and even thrive without their shells then why are noctis (noctloids?) Still around thats what i dont understand as animals evolve and more and more efficient forms of life are brought into existance why are less efficent forms allowed to stay. If "only the strong survive" why are the weak still here after eons of time.

  • Subscribed. I wish I had youtube back in my schooldays x) gj carry on

  • And that squid was me?

  • How did I not know about this channel until now

  • A little mollusc in a party hat.

  • snailn’t

  • Wait a minute.. am I watching the scishow? Or Hank finally got a job?

  • Is this Macro or Micro evolution, or is this not evolution at all?


  • I'd definitely watch this video if i needed to an essay about this.