Calico Clam, also known as the Calico Scallop or Calico-patterned Bivalve
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: gibbus · Pectinidae (Scallop family) · Bivalve (two-shelled clam), whole shell, fan/disc shape
Species
Argopecten gibbus (or related Pacific calico/pebble clam species)
Shell Type
Bivalve (two-shelled clam), whole shell, fan/disc shape
Family
Pectinidae (Scallop family)
Size
Approximately 0.75 to 1 inch in diameter, which is typical for smaller or juvenile specimens of this group. Adults generally range between 1 and 2.5 inches.
Color & Pattern
Vibrant orange and white mottled or zigzag patterns (calico pattern), highly glossy and natural-looking with well-preserved coloration.
Rarity
Common to Uncommon depending on the specific beach, though beautifully patterned intact small specimens are always a delightful find.
Habitat
Shallow marine waters, typically found on sandy bottoms, among seagrass beds, or shell grit in intertidal to shallow subtidal zones.
Geographic Range
Found in tropical and subtropical waters of the Americas, including the Pacific coast of Costa Rica (such as Guanacaste region).
Description
A charming, small bivalve shell featuring a classic rounded fan shape with subtle radial ribs and a striking, colorful mottled pattern of bright orange and white. The surface is smooth yet textured with fine growth lines, showcasing a glossy, polished finish typical of pristine beach-drifted specimens.
Key Features
Rounded fan shape, symmetrical or nearly equilateral valves, prominent radial ribs, and a distinct vibrant calico (mottled orange and white) color scheme.
Collector Value
Low to moderate commercial value, but high sentimental and aesthetic value for casual beachcombers and shell enthusiasts.
Condition Notes
Good to Fine condition, intact whole valve with bright, unfaded natural colors and minimal surface wear.
Interesting Facts
Many small bivalves and scallops in this family are capable of swimming short distances by rapidly clapping their valves together to expel water.
Ecological Role
Acts as a filter feeder helping to maintain water clarity and serves as an important food source for marine predators such as crabs, fish, and rays.
Similar Species
Other small pectinids and venerid clams, distinguished by the specific rib count and characteristic zigzag/mottled color patterns.
Beach Finding Tips
Look in shell-rich driftlines (such as Playa Conchal in Guanacaste, Costa Rica), sift through fine shell grit at low tide, or search after storms.
Notes
Guanacaste conchal Costa Rica