Echinoderms
KNOWN SPECIES
11,579
0.49% of our world's living things are echinoderms
CHARACTERISTICS
- animals without a backbone (invertebrates), that also have no head, eyes, or brain
- they can be divided into matching sections branching from a central point
- usually with five arms
SIZE RANGE
less than 0.39 inch to 6.5 feet (1 centimeter to 2 meters)
WHERE THEY LIVE
in oceans
Here are just SOME of the world’s echinoderms:
![Sticker about size](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_size_sticker/5943359-2-eng-US/echinoderms_size_sticker_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_size_sticker/5943359-2-eng-US/echinoderms_size_sticker_full_990.png 600w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_size_sticker/5943359-2-eng-US/echinoderms_size_sticker_full_1468.png 600w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_size_sticker/5943359-2-eng-US/echinoderms_size_sticker_full_1980.png 600w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_size_sticker/5943359-2-eng-US/echinoderms_size_sticker_full_2475.png 600w)
chocolate chip sea cucumber
SCIENTIFIC NAME:
Isostichopus badionotus
![Mottled brown long sea creature](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_cucumber/5941712-1-eng-US/echinoderms_sea_cucumber_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_cucumber/5941712-1-eng-US/echinoderms_sea_cucumber_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_cucumber/5941712-1-eng-US/echinoderms_sea_cucumber_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_cucumber/5941712-1-eng-US/echinoderms_sea_cucumber_full_1980.png 1980w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_cucumber/5941712-1-eng-US/echinoderms_sea_cucumber_full_2475.png 2400w)
sand dollar
SCIENTIFIC NAME:
Dendraster excentricus
![Coin-shaped sea creature](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sand_dollar/5941704-1-eng-US/echinoderms_sand_dollar_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sand_dollar/5941704-1-eng-US/echinoderms_sand_dollar_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sand_dollar/5941704-1-eng-US/echinoderms_sand_dollar_full_1468.png 1200w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sand_dollar/5941704-1-eng-US/echinoderms_sand_dollar_full_1980.png 1200w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sand_dollar/5941704-1-eng-US/echinoderms_sand_dollar_full_2475.png 1200w)
bat star
SCIENTIFIC NAME:
Asterina miniata
![Orange star-shaped sea creature](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_bat/5941708-1-eng-US/echinoderms_sea_bat_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_bat/5941708-1-eng-US/echinoderms_sea_bat_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_bat/5941708-1-eng-US/echinoderms_sea_bat_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_bat/5941708-1-eng-US/echinoderms_sea_bat_full_1980.png 1600w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sea_bat/5941708-1-eng-US/echinoderms_sea_bat_full_2475.png 1600w)
blood
star
SCIENTIFIC NAME:
Henricia leviuscula
![Vibrant red star-shaped sea creature](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_blood_star/5941700-1-eng-US/echinoderms_blood_star_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_blood_star/5941700-1-eng-US/echinoderms_blood_star_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_blood_star/5941700-1-eng-US/echinoderms_blood_star_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_blood_star/5941700-1-eng-US/echinoderms_blood_star_full_1980.png 1600w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_blood_star/5941700-1-eng-US/echinoderms_blood_star_full_2475.png 1600w)
sunflower sea star
SCIENTIFIC NAME:
Pycnopodia helianthoides
![Sea creature with lots of arms](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sunflower_sea_star/5941716-1-eng-US/echinoderms_sunflower_sea_star_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sunflower_sea_star/5941716-1-eng-US/echinoderms_sunflower_sea_star_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sunflower_sea_star/5941716-1-eng-US/echinoderms_sunflower_sea_star_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sunflower_sea_star/5941716-1-eng-US/echinoderms_sunflower_sea_star_full_1980.png 1600w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_sunflower_sea_star/5941716-1-eng-US/echinoderms_sunflower_sea_star_full_2475.png 1600w)
slate pencil urchin
SCIENTIFIC NAME:
Eucidaris tribuloides
![Spiky urchin with lots of tubes](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_slate_pencil_urchin/5943225-1-eng-US/echinoderms_slate_pencil_urchin_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_slate_pencil_urchin/5943225-1-eng-US/echinoderms_slate_pencil_urchin_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_slate_pencil_urchin/5943225-1-eng-US/echinoderms_slate_pencil_urchin_full_1468.png 1150w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_slate_pencil_urchin/5943225-1-eng-US/echinoderms_slate_pencil_urchin_full_1980.png 1150w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/echinoderms/echinoderms_slate_pencil_urchin/5943225-1-eng-US/echinoderms_slate_pencil_urchin_full_2475.png 1150w)
Guess what?
When stressed, sea cucumbers may spit out all of their internal organs, but they can usually grow them back!
Image Credits:
Bat star, blood star, sand dollar, Gerald and Buff Corsi/© California Academy of Sciences; chocolate chip sea cucumber, © Hans Hillewaert/CC BY-SA 4.0; slate pencil urchin, Eugene Weber/ © California Academy of Sciences; sunflower seastar, Sherry Ballard/ © California Academy of Sciences.