Chitons

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Below are examples of chitons you can find without much effort in northern Oregon’s exposed rocky intertidal. Even with this limited set, identifications are a challenge for me. I list some favorite field guides and online resources at the bottom of this page.

Organization and common names are my choices. I refer to WoRMS for scientific names, and I learn a ton by browsing the natural history riches in Kozloff (1993). All photos are from northern Oregon unless noted.

Tonicella
I’m pretty confident these are all lined chitons Tonicella lineata but not entirely so because other, similar Tonicella, like T. lokii, can be encountered (and not just T. lokii; there are others!). Thus it’s worth giving any Tonicella you find a close look. My examples are from the mid to low intertidal, where they are relatively abundant and easy to spot, for which I am grateful because each one is pure living beauty. I offer another photo and a few words about their pattern in Tonicella lineata’s Fine Lines; I explore the cleaner and the crust in Corallines and Chitons Layer the Lower Intertidal.

Katharina tunicata, Katy chiton
Easy to find and identify, Katies don’t try too hard to hide while they wait out the low tide. (But I feel like sometimes they’ll nose into a shadow.) You’ll be able to find them in the open on mid and low intertidal rocks, and you won’t mix them up with another chiton. I say a few more words about Katharina and show some more photos in Black Leather Chiton, Katharina tunicata, and Tidepool Treat: The Schizymenia – Katharina Connection.

And the Mopalias
Until I learn a little more about the group below, the genus is the closest I’m going to get. At the bottom of the page I’ve listed references for some of the Mopalia species you might encounter on the open coast.


References

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

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. 2009. The Beachcomber’s Guide to Seashore Life in the Pacific Northwest. Revised ed. Harbour Publishing.


Online Resources

Biodiversity of the Central Coast’s Molluscs page is a great starting place

Pacific Northwest Shell Club’s Chiton page

Aaron Baldwin’s Illustrated Keys to the chitons (Polyplacophora)

All the iNaturalist chiton pages are great fun to browse. Here are a few I looked at when I prepared this page:

Northern hairy chiton, Mopalia kennerleyi

Hind’s chiton Mopalia hindsii

Woody chiton Mopalia lignosa

Mossy chiton Mopalia muscosa


I updated this page on September 27, 2022.