Identification Key for Common Intertidal Sea Stars of Puget Sound

How to use this key
   1. Start at 1a.
   2. Count the arms on the sea star you wish to identify
and then click on the appropriate statement. You will be
moved to the next appropriate pair of statements.
   3. Click on the appropriate statement in that pair.
   4. Repeat this process until your animal is identified.

START HERE - Click either statement 1a or 1b below.

1a. Animal has five arms                                                 Go to 4
OR
1b. Animal has more than five arms                                 Go to 2
 
 
 
 
 
 
 

2a. Animal has six arms                                                 Six arm Sea Star, Lepasterias hexactis
OR
2b. Animal has more than six arms                                Go to 3
 
 
 
 
 
 
 
 
 
 
 
 
 

3a. Animal has 9 or 10 arms, smooth "skin"                      Sun Star, Solaster stimpsoni
OR
3b. Animal has more than 10 arms; spiny "skin"                Sunflower Star, Pycnopodia helianthoides
 
 
 
 
 
 
 
 
 
 
 
 
 

4a. Animal has short arms (R/r less than 3)
    * See notes                                                                       Go to 5
OR
4b. Animal larger or shaped otherwise                           Go to 7
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

5a. Prominent spines along the margin of arms                 Hippasteria spinosa
OR
5b. Smooth along margins of the arms                                  Go to 6
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

6a. Animal bright orange or red                                    Equal arm Sea Star Mediaster aequalis
OR
6b. Animal grayish; soft; leathery                                    Leather Star  Dermasterias imbricata
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

7a. Arms smooth; red on top, yellow beneath             Blood Star, Henricia leviuscula

OR
7b. Arms spiny                                                                 Go to 8
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

8a. Long arms (R/r =5 to 8)             Mottled Sea Star, Evasterias troschelli
          See notes
OR
8b. Short arms (R/r=3 to 4.5)                                       Go to 9
    See notes
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

9a. Color generally pink; animal can be up to
           two feet across                                                             Short Spined Sea Star, Pisaster brevispinus
OR
9b. Color purple, brown or orange                                    Purple Sea Star, Pisaster ochraceus

Bob Brenner
King County Department of Natural Resources
Water and Land Resources Division
700 5th ave, suite 2200
Seattle, WA 98104
bob.brenner@kingcounty.gov


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Updated 7/20/99