If you’ve ever been to an ocean, you’ve probably seen sand dollars on the beach or in souvenir shops. You may have even seen live sand dollars moving around on the sandy ocean floor. But what exactly are these creatures?

Sand dollars — sometimes called sea cookies, snapper biscuits, sand cakes, cake urchins or pansy shells — are species of flat, burrowing echinoids that belong to the order Clypeasteroida. Sand dollars are related to sea urchins, sea cucumbers and starfish.

Sand dollars get their name, not from their value, but from their appearance. When the skeletons (called tests) of dead sand dollars wash ashore, they are usually bright white from being bleached by the Sun. Long ago, people who found these dead sand dollars thought they looked like old Spanish or American dollar coins, so they called them sand dollars.

When sand dollars are alive, they live in shallow coastal waters along the sandy ocean floor. Unlike the white color of dead sand dollars, live sand dollars are usually green, purple or blue. Some people think live sand dollars look like fuzzy cookies!

Live sand dollars are covered with a dense, velvety layer of short spines and tubular feet. They use these spines and tubular feet to burrow into the sand and move around.

Sand dollars crawl along the ocean floor with their mouths toward the ground, eating microscopic particles of food. Most sand dollars live 8-10 years. The age of any particular sand dollar can be determined by counting the growth rings on the plates of its hard skeleton.

You may have noticed that sand dollar skeletons feature a pattern that looks like a flower. This pattern is where the live sand dollar’s tubular feet are located. In addition to helping the sand dollar move, these tubular feet also help direct food found on the ocean floor to the sand dollar’s mouth.

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    • Great questions from Mrs. Atkinson’s Class! HOORAY! While sand dollars don’t cost much today, they resemble old Spanish and American dollar coins, a currency from long ago. You can read the excerpt below for more information:

      “Sand dollars get their name, not from their value, but from their appearance. When the skeletons (called tests) of dead sand dollars wash ashore, they are usually bright white from being bleached by the Sun. Long ago, people who found these dead sand dollars thought they looked like old Spanish or American dollar coins, so they called them sand dollars.”

      We Wonder if you can do some WONDERing of your own– we’d love to hear what sand dollars eat and if they can see it! :)

  1. We are very curious about how the sand dollar consumes and expels out of the same place. We’re a little disgusted.

    Tomorrow’s guesses… starfish, hand puppets, idioms (some type of figurative language), mummy, environment, helping hands for teachers, prosthetic arms, kids helping make the world better, Mickey Mouse, and Earth Day!

    We’re still laughing at the pig and tapir.

    • Great point, Wonder Friends in Mrs. Hess’ class. We think the sand dollar’s digestive system makes our stomach flip, too! :) While researching, we learned that it can take a sand dollar nearly two days to digest its food!

      However, we’re glad to know that you are still chuckling from our Wonder earlier this week! Your guesses for tomorrow’s Wonder are outstanding, too! Great job using context clues, Wonder Friends! :)

    • What a stellar guess, Wonder Friends in Mrs. Bryant’s Class! We’re giving you all virtual high fives! You’ve got to hand it to us, it’s a great pun! :)

  2. Dear Wonderopolis,

    We enjoyed learning about sand dollars. We didn’t know they could be different colors. Some of us wondered if any other animals eat a sand dollar?

    We think tomorrow will be about helping others, a magic trick, or even a skeleton.

    thank you for the wonders,
    Mrs. Tillman’s 4th graders.

  3. We never knew that sand dollars had mouths and were all of those colors when they are alive! Very interesting! We didn’t know that sand dollars moved. We thought they just stayed in one place at the bottom of the ocean. We thought it was cool to learn about how they got their name. We didn’t know that they were fuzzy. We didn’t know that their skeletons were known as tests! What an interesting homonym.

    We think tomorrow’s Wonder will be about idioms, helping people, who invented idioms, or why we have fingers.

    • Our Wonder Friends in Mrs. Ski’s AM Class have done a SUPER job of summarizing what you learned today! We Wonder if any of you have a sand dollar at home, or have found one on the beach?

      We look forward to WONDERing with you again tomorrow! Have a terrific Thursday! :)

    • Great question, KOOLDUDE! Sand dollars are not very expensive, and if you live near a beach, you might have a lot of luck finding them in local shops! Thanks for visiting us today! :)

    • WOOHOO, we’re so glad you learned something new today, Kyle! Thanks for visiting and WONDERing with us today! See you soon! :)

    • YIPPEE, we’re glad to hear it, Caroline! We Wonder… what is your favorite fact from today’s Wonder? Thanks for sharing your super guesses, too! :)

  4. Our class took the sentences in this wonder, and had to place them in groups of what facts we thought went together! I loved doing it! And your facts are so cool! Like that one about how live ones move! Thank you for posting this wonder!

    • We bet that was a fun and helpful exercise to do, Alexi! Thanks for sharing your classroom activity with us- we’re so glad we could be a part of it! Thanks for WONDERing with us! :)

    • We’re sorry to hear that, Grace W! We bet refreshing the page will help. If not, we recommend trying to watch the Wonder video at home or in the library. If you’re at school, sometimes video streaming is not available, or it could even be blocked. :)

  5. Wow! I really liked today’s wonder! I have seen sand dollars before, and I thought that they were just sand. I never even knew that sand dollars were sea creatures, and that they were purple, green and blue when they are alive. So I guess that I have only seen dead ones. It was fascinating to learn that they are related to sea urchins, sea cucumbers and starfish. I leared a lot today!
    Thank you for today’s wonder!

    • You’re not alone, Berkleigh! Many Wonder Friends have learned a LOT from today’s under the sea Wonder! :)

      We’re so happy that you enjoyed learning new things about sand dollars and their habitat! :)

  6. Dear Wonderopolis,

    Only some of us have seen a sand dollar before and some of us have even seen a live one too. We were wondering if the sand dollar skeleton is smooth or rough feeling?

    We think tomorrow’s wonder will be about archaelogoy or a skeleton.

    Thank you for the wonders,
    Mrs. Witkowski’s 4th graders

    • Way to go, Wonder Friends in Mrs. Witkowski’s 4th grade class! We haven’t held a sand dollar in our own hands, but we bet it would tickle a bit as their feet moved around! Thanks for WONDERing with us today, and using your imagination to guess what tomorrow will bring! See you soon, Wonder Friends! :)

  7. We love sand dollars & we made up a deserted island currency system. One shark tooth is worth 5 sand dollars, one sand dollar is worth 5 starfish, and one starfish is worth 2 fancy shells! Our guess for tomorrow’s wonder is something about mechanics or octopuses!!! Thanks again!!!

    • What a SUPER idea, Gwen and Angus! We would like to shop on your island, we’d have to make sure we have a pocket full of shark teeth! :) Way to use your imaginations, we’re very proud of you! :)

    • Me, oh, my, there are so many great guesses from Mrs. Jones’ 3rd grade! We can’t wait to give you a virtual high five tomorrow! :)

  8. We thought today’s Wonder was didn’t AMOUNT to much …money… lol! However, we liked learning how they look and live in the water when they are alive. It was interesting to learn about their multi-tasking digestive system. Weird. Very weird. Reminded us of jellyfish though! Several of us have sand dollars including JC who has a birthday tomorrow. Therefore he is hoping tomorrow’s Wonder really takes the cake!

    See… we are really thinking the Wonder will be about idioms. We just spent a week focussed on idioms and they have driven the kids up the wall! Mrs. Ski is on cloud nine over their test results, though. These smarties are the apple of her eye! :) Some of us think that tomorrow’s wonder will be about people with one arm or prosthetics or new cars for hands free trunk access.

    • We’re glad you were WONDERing with us under the sea today, Wonder Friends in Mrs. Ski’s PM Class! A happy birthday to JC– we hope you have a WONDERful day! We sure are glad we learned that sand dollars are real, not just shells like some of us thought!

      Speaking of idioms, have we got a Wonder you will enjoy! It’s a throw-back… a Wonder from the past. We really think this will be right up Mrs. Ski’s alley, if you know what we mean! Wonder of the Day® #77– Why Do People Say “A Dime a Dozen”? http://wonderopolis.org/wonder/why-do-people-say-%E2%80%9Ca-dime-a-dozen%E2%80%9D/ :-)

  9. I did not know that they were purple & more. (Carlee did this)
    I learned a lot about sand dollars. (Rori did this)

    :] ;] {; {:

    :} ;}

    • Way to go, Carlee and Rori! We are so glad you shared what you learned about sand dollars today! We LOVE learning something new with great Wonder Friends like you! We hope you have a terrific Thursday, full of fun! :-)

    • It’s so great that you enjoyed WONDERing with us today, Aces! It’s lots of fun to discover something new about creatures under the sea! Thanks for visiting today, and we’ll see you soon, Wonder Friend! :)

  10. I did not know that sand dollars were alive at times I thought it was just a shell.

    I have a question what is the least populated country that we know of in the world?

    • Isn’t it cool to learn something new about sand dollars, Grace? We have an entirely new understanding of how they live– and some of us thought they were just shells, too! :-)

      Thanks for sharing your very own Wonder, too! We hope you have a SUPER day! :)

    • Thanks for sharing your comment, lili13! Who knew that sand dollars led such an interesting life? Thanks for WONDERing with us! :)

    • Hi there, Wonder Friend Kathy! Thanks for stopping by to say hello! We have found one or two sand dollars on the beach, but not many more! However, scientists have found many while they dig in certain areas– that’s how they observe sand dollars in their natural habitat! Thanks for WONDERing with us today, and sharing your very own Wonders, too! HOORAY! :-)

  11. Wow! Wonderopolis is decent, indeed! Maybe you could make the next video showing me how awesome you are! ♥ Me :D

    • Well thanks so much, Wonder Friend! We are here to help spread Wonder and inspire Wonder Friends just like you! Our videos will be about different topics, but we’re glad you enjoy visiting us! :)

    • We LOVE the word you created to describe today’s Wonder, Wondergirl7! Thanks for visiting us today! We are sorry to hear that your sand dollar was broken– they are pretty fragile! It’s okay, because we were learned a whole lot about the sand dollar’s life today! Thanks for WONDERing with us! :)

    • Thanks for summarizing your favorite features of a sand dollar, Kate! We’re so glad you enjoyed our Wonder– thanks for sharing! :)

    • Thank you so much for your kind comment, Wonder Friend! We have lots of Wonder Friends to help us research new Wonders of the Day®! Thanks for WONDERing with us! :)

  12. Thank you for making these AWESOME videos!!!!! I’ve been thinking, though… how are insects born?! Like, ants for instance…..

    • Hi there, Wonder Friend! We are glad you’ve been WONDERing about insects with us- thanks for stopping by! We will have to do some WONDERing about insect births… perhaps you can do some research, too! :)

    • Great question, Wonder Friend Pizzacuttercat! We Wonder if you can do some research of your own about sand dollars and their size! We’d LOVE to learn more with your help! :)

    • Hey there, Salisha! Thanks for sharing your comment about sand dollars! It depends where you buy the sand dollar, but usually they’re not very expensive (perhaps a few dollars!) We Wonder, if you ruled the world, would you change the currency from dollars to sand dollars?! :)

  13. I found a large sand dollar about three feet underground in Washington, 11 1/2 cm long and a little over an inch wide is this special?

    • Hey there, Wonder Friends Kennedy and Elizabeth! Thank you for sharing your comments with us- we’re happy to know that you enjoyed learning about sand dollars today! :)

    • Hey there, Salmiel! Thanks for sharing your comment, we are glad you’re here! While sand dollars used to be considered valuable, they are now used as trinkets and gifts from the beach! We Wonder if you have ever received a sand dollar, or given one to another person? :)

  14. My Grandpa has a whole HUGE box full of sand dollars! He has an enormous bubbly one from the Philippines, and some teeny tiny ones. I got to take the tiny ones home! They look like Mentos! Guess what? If a sand dollars is brown or gray, it was living when it washed up, then dried out or starved. If It is white, it died a while ago, then was washed up or something, and the older it gets the whiter it gets. They are not white when they are living. Some are much lighter and appear to be white though.

    • WOW, thanks for sharing your awesome comment with us today, Sarah! It sounds like you and your Grandpa have been WONDERing about and observing sand dollars for a while0- HOW COOL! :)

      We love your description for sand dollars, especially when they’re different sizes! :)

    • You got it, Wonder Friends Bailey and Maliha! We LOVE your enthusiasm and we’re so glad you learned something new with us today! HOORAY for WONDERing! :)

  15. wonderopolis rocks!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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Have you ever wondered…

  • How much is a sand dollar worth?
  • Why are they called sand dollars?
  • What sea creatures are sand dollars related to?

Wonder Gallery

Sand DollarVimeo Video

Try It Out

Ready to set up a marine-based currency system? Let’s say that you and a whole cruise ship full of passengers have been shipwrecked on a previously-deserted island. The island has plenty of fresh water and marine life abounds.

You’ve been able to set up shelters using materials you retrieved from the wrecked cruise ship. Unfortunately, the island you now occupy is not on any map known to man. It could be years before rescuers stumble upon you.

In the meantime, you need to reestablish a basic society on the island. Each person has individual talents that can be used in important ways. To help create a system that makes trading easier, you decide to create a basic currency system based upon the marine life found on the island.

What do you start with? The sand dollar, of course! What is it worth? It’s up to you, but we’d suggest one dollar just so people don’t get confused.

Here are some other common forms of marine life found on the island:

  • seashells
  • starfish
  • shark teeth
  • crabs
  • oysters

What should each be worth and why? Can you set up a simple conversion table to let people know, for example, how many seashells are equal to one crab? Have fun coming up with a new form of marine currency!

Still Wondering

Check out EDSITEment!’s Under the Deep Blue Sea lesson to explore oceans and ocean life!

Wonder What’s Next?

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