Broad-ribbed Cardita (Broad-ribbed Clam)
Phylum: Mollusca | Class: Bivalvia | Order: Carditida | Family: Carditidae | Genus: Carditamera | Species: Carditamera floridana · Carditidae (Cardita / False Cockle family) · Bivalve (single valve shown, exterior view). Shape is fan/ovate with heavy radial ribs.
Species
Carditamera floridana (High confidence)
Shell Type
Bivalve (single valve shown, exterior view). Shape is fan/ovate with heavy radial ribs.
Family
Carditidae (Cardita / False Cockle family)
Size
Approximately 1 to 1.5 inches (25-38 mm) in length. Typical adult size ranges from 0.75 to 1.5 inches.
Color & Pattern
Off-white to creamy base color with distinct yellowish-amber to orange-brown concentric highlights along the raised growth lines and radiating ridges. The coloration appears natural with light beach wear.
Rarity
Very Common. Frequently found washed ashore on beaches along the Gulf Coast and Southeastern Atlantic coast of the United States.
Habitat
Intertidal to shallow subtidal marine waters down to about 25 feet. Prefers sandy bottoms, mudflats, and seagrass beds, often burrowing lightly just beneath the substrate surface.
Geographic Range
Western Atlantic Ocean, primarily along the Southeastern United States from North Carolina south through Florida, the Gulf of Mexico, and into the Caribbean.
Description
A thick, sturdy bivalve valve characterized by strong, heavy radial ribs that fan out from the umbo (beak) to the margin. The ribs feature small, bead-like raised nodes or scales, especially towards the outer edges. The shell has a distinctive trapezoidal-to-ovate shape with a pointed, offset beak.
Key Features
15 to 20 strong, heavy radial ribs with beaded or cross-striated sculpturing; offset beak positioned near the anterior end; sturdy, thick-shelled construction that resists wave damage.
Collector Value
Minimal monetary value ($1 - $3) due to its abundance, but highly appreciated by beachcombers for its pleasing symmetry, vibrant warm tones, and durability.
Condition Notes
Good condition. A single complete valve showing clear radial ribbing and distinct coloration. Slight edge wear and minor smoothing from wave action, but overall structural integrity is well preserved. Grade: Fine to Good.
Interesting Facts
Unlike true cockles (Family Cardiidae), Carditids belong to a completely separate family despite their strong radial ribs. They use strong fibrous threads called byssus when young to attach to hard objects before living as shallow burrowers as adults.
Ecological Role
Infaunal filter feeder that strains plankton and organic detritus from the water column, helping to clarify shallow coastal waters. Serves as a food source for bottom-feeding fish, crabs, and sea stars.
Similar Species
Trachycardium muricatum (Yellow Cockle) - wider, rounder shell with sharper prickly spines on ribs; Dinocardium robustum (Giant Atlantic Cockle) - grows much larger with broader, flatter ribs.
Beach Finding Tips
Look near the high tide mark after stormy conditions or strong onshore winds along sandy beaches, especially in Florida and along Gulf Coast barrier islands.