Atlantic Cockle (Prickly Cockle / Yellow Cockle)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Cardiidae, Genus: Dinocardium, Species: Dinocardium robustum · Cardiidae (Cockle family) · Bivalve (two-shelled mollusk), fan/heart-shaped single valve
Species
Dosinia discus or Dinocardium robustum (likely Dinocardium robustum)
Shell Type
Bivalve (two-shelled mollusk), fan/heart-shaped single valve
Family
Cardiidae (Cockle family)
Size
Approximately 2 to 2.5 inches in diameter, which is typical for a mid-sized adult cockle specimen.
Color & Pattern
Displays concentric growth rings with a distinct color gradient: dark greyish-blue towards the older umbo (beak) region transitioning into warm tan, yellowish, and reddish-orange hues along the ventral margin, intersected by radial ribs.
Rarity
Common
Habitat
Inhabits shallow marine environments, intertidal and subtidal sandy ocean floors, burrowing just beneath the surface of the sand.
Geographic Range
Western Atlantic, ranging from the southeastern United States (North Carolina down to Florida) through the Gulf of Mexico and into the Caribbean.
Description
A rounded, heart-shaped single valve featuring pronounced radial ribs intersecting with concentric growth lines. The umbo is well-defined and prominent, showing natural mineral staining or darkening near the apex while the outer edge retains vibrant orange and pinkish-tan coloration.
Key Features
Strongly arched, heart-shaped profile in cross-section; clear, evenly spaced radial ribs running from the umbo to the crenulated edge; distinct color transition from dark grey-green at the beak to salmon-orange along the margin.
Collector Value
Low monetary value ($1 - $5) due to its abundance, but highly valued by beachcombers and craft collectors for its vibrant color gradients and classic shell geometry.
Condition Notes
Good condition. The exterior details and radial sculpturing remain clearly intact, though slight mineral discoloration/staining near the umbo indicates prior burial in anaerobic sand before washing ashore.
Interesting Facts
Cockles possess a strong, muscular foot that allows them to jump across the seafloor to escape predators like sea stars. Their thick shells protect them from wave action in shallow intertidal waters.
Ecological Role
Functions as a burrowing filter-feeder that clears microalgae and organic detritus from water, serving as a vital food source for sea stars, shorebirds, fish, and crabs.
Similar Species
Trachycardium muricatum (Yellow Cockle) which has sharper, pricklier ribs, and Clinocardium nuttallii (Nuttall's Cockle) found on the Pacific coast.
Beach Finding Tips
Best found along high-energy sandy beaches after stormy weather or during low tide near the drift line, where wave action unearths buried bivalve valves.