Mortensen's Cockle, also commonly known as the Heart Cockle or West Coast Cockle
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Cardiidae, Genus: Trachycardium, Species: Trachycardium mortenseni · Cardiidae (Cockle family) · Bivalve (two-shelled), whole individual valve, fan or heart-shaped morphology
Species
Trachycardium mortenseni (or related Clinocardium / Vasticardium species, with high confidence for a type of cockle)
Shell Type
Bivalve (two-shelled), whole individual valve, fan or heart-shaped morphology
Family
Cardiidae (Cockle family)
Size
Approximately 1.5 inches in length and width, which is a medium to large size for a juvenile or average-sized adult specimen depending on the exact species range of 1 to 3 inches.
Color & Pattern
Off-white to cream base color with subtle reddish-brown or orange-brown speckling and banding concentrated along the posterior margin. The colors appear natural and slightly sun-bleached on the prominent ribs. The interior is generally white with hints of the exterior pattern showing through.
Rarity
Common, frequently discovered by beachcombers walking along sandy tropical or subtropical shorelines after high tides or storms.
Habitat
Shallow subtidal to intertidal zones, typically found buried just beneath the surface of clean sand, mud, or fine gravel substrates in marine environments.
Geographic Range
Indo-Pacific region, widely distributed across tropical and subtropical shallow waters, often found along the coasts of Southeast Asia, Australia, and various Pacific island chains.
Description
An attractive, robust bivalve shell featuring a symmetrical, heart-shaped profile when viewed laterally. It is heavily sculptured with strong, prominent radial ribs that extend from the umbo to the scalloped margin, creating a distinct corrugated texture that provides excellent structural strength.
Key Features
Distinguished by strong, radiating ribs (typically 20 to 30), a rounded heart-shaped cross-section when viewed from the side, a slightly asymmetrical hinge plate, and deeply crenulated margins where the ribs meet.
Collector Value
Low to moderate commercial value, highly popular among beginner and intermediate shell collectors due to its pleasing symmetry and tactile ribbed texture. Typically sold in tourist shell shops for a nominal price.
Condition Notes
Good to Fine condition. The valve is intact with a well-preserved margin and strong radial ribs showing minimal wear. Minor natural color fading due to sun exposure, but overall structurally sound and highly collectible.
Interesting Facts
Cockles are capable of remarkable locomotion; unlike many sedentary bivalves, they use a strong, muscular foot to leap or burrow rapidly away from predators like starfish and carnivorous snails.
Ecological Role
Cockles play an important role in benthic ecosystems as filter feeders, helping to clear water columns of phytoplankton and organic particles. They serve as a vital food source for shorebirds, rays, and carnivorous gastropods.
Similar Species
Other members of the Cardiidae family such as the Common Edible Cockle (Cerastoderma edule) or the Strawberry Cockle (Fragum fragum). They can be distinguished by subtle variations in rib count, shape, and specific color patterning.
Beach Finding Tips
Look along sandy beaches during low tide, particularly near the wrack line or in shallow sand bars where waves wash up shell debris. Pay attention to symmetrical valves washed clean by surf.