Below are examples of chitons you can find without much effort in northern Oregon’s exposed rocky intertidal. I don’t flip rocks, so these are the just chitons that don’t mind some daylight exposure. Even with this limited set, identification is a challenge for me. I list some of my favorite field guides and identification resources at the bottom of this page. I have relied heavily on them, but any identification errors are mine.
Below, organization and common names are my choice. 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 otherwise noted in the caption.
Lined Chiton, Tonicella lineata– Look for lined chitons on the crustose corallines. They’re common, but you’ll need to pick a good low tide to find them. Lined chitons are variable, but the variation I’ve noticed is much more limited than what you’ll see in some of the guides. The lined chiton is featured in Corallines and Chitons Layer the Lower Intertidal.
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Black leather chiton, Katharina tunicata– Easy to find and easy to identify, Katharina doesn’t try to hard to hide while it waits out low tide. You’ll find it in the open on low intertidal rocks. Out in the open, in daylight, Katharina will frequently nose into a shadow. There is individual variation, as seen in the photos below, but you won’t mix it up with any other chiton. I say a few words about Katharina in Black Leather Chiton, Katharina tunicata.
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And the mopalias…- Identifying chitons is tough. Until I learn a little more about the group below, the closest I’m going to get is the genus Mopalia. I’m guessing Mopalia kennerleyi is represented in the below, but M. hindsii, M. muscosa, and M. lignosa are all in the running. If you have thoughts, please let me know.
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. 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
Pacific Northwest Shell Club’s Chiton page
Aaron Baldwin’s Illustrated Keys to the chitons (Polyplacophora)
iNaturalist’s page on the northern hairy chiton, Mopalia kennerleyi
iNaturalist’s page on Hind’s chiton Mopalia hindsii
