Chitons

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Below is a selection of chitons I’ve been lucky to find and photograph in northern Oregon’s exposed rocky intertidal habitats. They’re the most easy-to-spot chitons—the ones you can find with a light touch without turning rocks or creating disturbances. However, easy-to-spot doesn’t translate to easy identification, at least not for me. Experts cover these and many more chitons in the guides and online resources at the bottom of this page. Organization and common names are my choices; unless noted, the photos are from northern Oregon.

Here’s to the chitons!


Tonicella
I’m pretty confident these are lined chitons Tonicella lineata. They are relatively abundant in the mid and low intertidal zones, something I’m grateful for because each one is pure living beauty.

Chiton among crustose corallines, articulated corralines, some red blades, and a giant green anemone.
Tonicella is a beautiful Pacific Northwest chiton
A kind of shy looking chiton with its head down, tucked into some articulated corallines, crustose corallines, mussels, a limpet, and surfgrass also make an appearance.
Can you tell which direction its head is pointing?
Featuring a chiton on crustose corallines. Red blades on either side.
Look for lined chitons among the crustose corallines
Closeup on a chiton upside down in a crevice.
Lined chitons don’t mind being upside down
Close in on a chiton that has seemingly cleared a small area of crustose corallines off a vertical surface. The scene also features a sponge and a portion of a giant green anemone.
Maintaining a little open ground
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Katharina tunicata, Katy chiton
Katies don’t try too hard to hide. (But sometimes they’ll nose into a shadow.) Look for them on mid and low intertidal rocks, where you won’t confuse them with any other chiton.

A fairly closeup view of a single black leather or Katy chiton on a bare rock in between blades of sea cabbage.
Katharina tunicata cozy with the sea cabbage
Passing low tide in a pleasing setting
Low tide reveals a Katy down among the reds
And the head is pointing… (Which direction?)
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Mopalia
The gallery provides just a glimpse of variation among the easy-to-spot Mopalia. (I’m not entirely confident in my selections, but I think they are all Mopalia.)

A wet nondescript limpet on a wet rock.
Even out in the open, it wouldn’t be hard to miss this beauty
A chiton partially visible, about half covered by seaweed. A few barnacles and Some fresh Nucella eggs are also present.
Just over half a chiton
A chiton perched on a giant barnacle. Four giant green anemones fill out the scene.
Perched among giants
A chiton noses up against a giant green anemone. At the rear, a notch or cleft in the girdle.
A prominent cleft at the rear
Chiton on a mostly bare rock with a few barnacles and a small starfish.
Leptasterias dead ahead
Closeup on a chiton with rather worn plates and a bit of encrustation on the anterior plates.
A brush with Nucella
Sand on the girdle and crustose reds on the valves add camouflage to a chiton.
Going the extra mile to blend in
A chiton shares space with giant green anemones and gooseneck barnacles.
Lovely blue valves
A chiton on a smooth rock is partially buried in sand. A small limpet on one of the posterior valves.
Picked up a hitchhiker

It’s not too uncommon to find drifted valves washed up on the beach.

Drifted chiton valves are sometimes called butterfly shells
***


References

Gotshall, D. W. 2005. Guide to Marine Invertebrates, Alaska to Baja California. 2nd Edition (Revised). Shoreline Press.

Harbo, R. M. 2011. Whelks to Whales: Coastal Marine Life of the Pacific Northwest. 2nd ed. Harbour Publishing Co.

Kozloff, E. N. 1993. Seashore Life of the Northern Pacific Coast. 3rd ed. University of Washington Press.

Lamb, A. and B. P. Hanby. 2005. Marine Life of the Pacific Northwest. Harbour Publishing.

Sept. J. D. 2019. The New Beachcomber’s Guide to the Pacific Northwest. Harbour Publishing.


Online Resources

Pacific Northwest Shell Club’s Chiton page. Accessed April 25, 2023.

Aaron Baldwin’s Illustrated Keys to the Chitons (Polyplacophora). Accessed April 25, 2023.

Biodiversity of the Central Coast’s Molluscs page. Accessed April 25, 2023.

Common Sea Life of Southeastern Alaska: A field guide by Aaron Baldwin & Paul Norwood. Accessed April 25, 2023.

Friends of Netarts Bay WEBS Mollusks page. Accessed April 25, 2023.


Cowles, D. (2005). Tonicella lineata (Wood, 1815). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed April 25, 2023.

Lunsford, R. (2002). Katharina tunicata. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed April 25, 2023.


I updated this page on April 27, 2023.