Broad-Ribbed Carditid (also known as the Broad-Ribbed Cardita)
Phylum: Mollusca, Class: Bivalvia, Order: Carditida, Family: Carditidae, Genus: Carditamera, Species: C. floridana · Carditidae (Cardita or False Mussel family) · Bivalve (clams, scallops, etc.); Single valve present; Shape is sub-trapezoidal to rounded-oval.
Species
Carditamera floridana
Shell Type
Bivalve (clams, scallops, etc.); Single valve present; Shape is sub-trapezoidal to rounded-oval.
Family
Carditidae (Cardita or False Mussel family)
Size
Approximately 0.75 to 1 inch. Adults typically range from 0.5 to 1.5 inches; this specimen is a mature, average-sized representative.
Color & Pattern
Base color is creamy white to off-white. There are faint traces of brownish-purple spots or bands on the ribs, though it appears somewhat sun-bleached. The interior is likely smooth white.
Rarity
Very Common. These shells are frequently washed up in large numbers on Florida Gulf Coast beaches.
Habitat
Typically found in shallow marine waters, intertidal zones to 30 feet deep. It prefers sandy or muddy substrates and is often found near seagrass beds.
Geographic Range
Western Atlantic: found from North Carolina down through Florida, the Gulf of Mexico, and into the West Indies.
Description
A sturdy, thick-walled bivalve characterized by approximately 15-20 strong, radiating ribs. The ribs are broad and slightly beaded or scaled. The shell has an asymmetrical, elongated shape with the beaks (umbones) positioned toward the anterior end.
Key Features
Heavy, prominent radial ribs; sub-trapezoidal shape; hinger plate with strong cardinal teeth; crenulated (scalloped) inner margins corresponding to the external ribs.
Collector Value
Low monetary value ($0.50 - $1.00) due to high abundance. However, they are highly desirable for craft projects and beginner collections because of their durability and classic 'clam' aesthetic.
Condition Notes
Good condition. It is a single valve rather than a paired set. The surface shows minor beach wear/erosion, and colors are slightly faded due to sun exposure, but the rib structure remains crisp and identifiable.
Interesting Facts
Unlike many clams that burrow deep, Carditamera species often live partially buried or attached to debris. They are sometimes called 'Bird Wing' shells by casual beachcombers due to their profile.
Ecological Role
Suspension feeder that filters plankton from the water column. They serve as a food source for bottom-dwelling predators like rays, crabs, and gastropods (e.g., whelks and drills).
Similar Species
Venericardia borealis (Northern Cardita) which is rounder and found in colder waters, and Arca zebra (Turkey Wing) which has a much more elongated, 'winged' appearance and different hinge.
Beach Finding Tips
Look along the Gulf Coast of Florida after a high tide or storm. They are often found in 'shell pockets' where heavier, ribbed shells accumulate due to wave action.