Chitons - Acanthochitonidae,Schizoplacidae,Tonicellidae

Acanthochitonidae

Marrowstone Island, WA, intertidal Dungeness Spit, WA, fresh dead Freshwater Bay, WA, subtidal Anacortes, WA, intertidal

Click on photo to enlarge. Scale line in photo equals 1cm unless otherwise specified.
* Species which are commonly encountered on the beach.

Cyanoplax dentiens (Gould, 1846)
Gould's Baby Chiton *
intertidal to 6m northern Mexico to southern Alaska size to 2.7cm
This is a common intertidal species although often hard to spot due to its small size. It is variable in color but is most commonly greenish-gray to brown. White flecks or blue-green dots are also typical.
(previous names - Lepidochitona dentiens, Ischnochiton dentiens)

Cryptochiton stelleri (Middendorff, 1847)
Giant Pacific Chiton or Gumboot Chiton *
intertidal to 20m size to 35cm
southern California to northern Alaska; Japan
This is a fairly common intertidal species and is the largest chiton species in the world. The girdle completely covers the plates.
The disarticulated plates are often called "butterfly shells".
(previous name - Amicula stelleri)

Cyanoplax fernaldi (Eernisse, 1986)
Fernald's Baby Chiton
mid to high intertidal southern Oregon to SE Alaska size to 15mm
This species is hard to find due to its small size. Its preferred habitat is among Thatched Barnacles and Aggregating Anemone, where it is tucked into crevasses where it is not easily seen. This species is easy to confuse with C. dentiens although it usually has more eroded plates. Our left photo shows a rare turquoise phase.
previous names - (Lepidochitona fernaldi)

Boreochiton beringensis (Yakovleva, 1952)
Northern Red Chiton
very low intertidal to at least 30ml size to 35mm
northern BC to Bering Sea
This species may have red, green or blue patches on its plates.
(previous name - Tonicella beringensis)

Tacoma, WA, intertidal Turn Island, WA, subtidal Gabriola Is., BC, found subtidally

Tonicella insignis (Reeve, 1847)
White-Line Chiton
intertidal to 50m northern Oregon to northern Alaska size to 6cm
This species is rarely found intertidally. It is reddish-brown with lighter-toned wavy lines across the width of the plates. The girdle is light reddish-brown.

Tonicella lineata (Wood, 1815)
Lined Chiton *
intertidal to 90m southern California to northern Alaska, Japan & Siberia size to 5cm
This is a very common intertidal species. The background color is orangish but can range from pink-orange to brown-orange. Wavy bluish-white lines run across the sides of the plates which are edged in reddish-brown. The lines along the head and tail plates may be wavy, and will also be edged in reddish-brown. Some plates may be a solid color, usually a reddish tone but sometimes blue. The girdle is banded and also may vary in its colors. Very young specimens can be highly variable in the number of lines and colorations as shown in photo above right.

Tonicella rubra (Linnaeus, 1767)
Northern Red Chiton
intertidal to 145m size to 22mm
California to Arctic; in Atlantic - Connecticut and northern Europe to Arctic
This is rarely found intertidally in the Pacific Northwest. The plates are light tan with red to orange-red markings. The plates may also be uniformly reddish. The girdle is covered in minute scales which do not overlap.
(synonyms - Boreochiton ruber, Ischnochiton ruber)

Freshwater Bay, WA, subtidal Tongue Point, WA, subtidal

Tonicella cf. undocaerulea (Sirenko, 1973)
Blue-Line Chiton
intertidal to 50m southern California to central Alaska size to 5cm
This is occasionally found intertidally. It has a light orangish-pink background, and may occasionally be solid in color. Blue to white wavy lines run along the sides of the plates. There may beoccasional streaks of maroon edging some of the lines. The blue lines on the head and tail plates are distinctly zigzagged and are not edged in maroon. The girdle is banded pink and yellow.
T. undocaerulea is now known to not be present in the eastern Pacific but our local species has yet to be named.

Neah Bay, WA, preserved specimen
Tonicella cf. venusta Clark, 1999
intertidal to 140m size to 1.7cm
northern Mexico to southern Alaska
This tiny species is rarely found intertidally. It has a light orange or pink background with white zigzag lines. Light dash markings along the center of the plates separate this species from the others. The girdle appears sandy. (The ID on the photo is not confirmed but it conforms to all characteristics.)

Schizoplacidae

preserved specimens and color variations all Port Hardy, BC, intertidal

Schizoplax brandtii (Middendorff, 1847)
very low intertidal to 40m central BC to Alaska, Bering Sea & Sea of Japan size to 2cm
This is occasionally seen intertidally. It has brown striping over a blue background. The plates are split down the mid-line by cartilage-like tissue which is best seen under magnification. There may actually be more than one species represented across its range.

Chitons (Polyplacophora)

Family Acanthochitonidae, Schizoplacidae