Pacific Giant Cockle or Giant Atlantic Cockle
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Cardiidae, Genus: Clinocardium, Species: Clinocardium nuttallii · Cardiidae (Cockle family) · Bivalve (two-shelled), whole individual valve with fan-like shape
Species
Dinocardium robustum or Tridacna/Clinocardium species
Shell Type
Bivalve (two-shelled), whole individual valve with fan-like shape
Family
Cardiidae (Cockle family)
Size
Approximately 3 to 4 inches in width, which is typical for a mature specimen of this species. Adults generally range between 2 to 5 inches.
Color & Pattern
Cream to off-white base color featuring striking reddish-brown or chestnut blotches and banding running across the strong, prominent radial ribs. Colors appear completely natural with vibrant contrast.
Rarity
Common, frequently discovered by beachcombers along the Pacific Northwest coast.
Habitat
Found primarily in shallow marine waters, intertidal to subtidal zones down to moderate depths, buried just beneath the surface in sandy or muddy substrates.
Geographic Range
Pacific coast of North America, ranging from Alaska down to Southern California.
Description
A robust, heavy-textured bivalve shell featuring deep, prominent radial ribs and concentric growth lines that create a textured, interlocking margin. The overall shape is broadly ovate to triangular with a strongly inflated profile.
Key Features
Numerous prominent radial ribs (usually around 30 to 35), strong serrated margin, and characteristic reddish-brown interrupted color bands over a pale background.
Collector Value
Moderately low commercial value due to abundance, but highly prized by amateur beachcombers for its pleasing symmetry and robust durability.
Condition Notes
The specimen appears to be in very good to fine condition with intact margins, strong color retention, and no major structural fractures.
Interesting Facts
Cockles are capable of using their strong, muscular foot not only to burrow rapidly into the sand but also to leap away from approaching predators like sea stars.
Ecological Role
Serves as an important filter feeder in coastal marine ecosystems, helping to clear water column particulates while acting as a prey source for fish, birds, and crabs.
Similar Species
Loggerhead Sweetlips or other cockle species like Cerastoderma edule, which generally feature different rib counts and distinct geographical ranges.
Beach Finding Tips
Look along sandy ocean beaches following winter storms or during extremely low tide events when shifting sands expose buried bivalves.