Atlantic Deep Sea Scallop (also known as Giant Scallop or Fossilized Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Placopecten, Species: Placopecten magellanicus · Pectinidae (Scallop family) · Bivalve (two-shelled), whole shell, fan-shaped disc morphology
Species
Placopecten magellanicus
Shell Type
Bivalve (two-shelled), whole shell, fan-shaped disc morphology
Family
Pectinidae (Scallop family)
Size
Approximately 4 to 5 inches across, which is typical for an adult specimen of this species. Adults generally range from 3 to 8 inches in diameter.
Color & Pattern
Uniform dark charcoal to black coloration, heavily weathered, suggesting fossilization, mineral staining, or long-term anaerobic burial in sediment. The interior layer and some minor surface wear reveal a lighter tan or off-white calcareous base underneath the dark patina.
Rarity
Uncommon in this specific dark, mineral-stained or fossilized condition, though the living species itself is very common commercially.
Habitat
Found on cold-water sandy, gravelly, or muddy bottoms from the intertidal zone down to depths of over 100 meters, typically living unattached on the ocean floor.
Geographic Range
Northwest Atlantic Ocean, ranging from the coast of Labrador and Newfoundland down to North Carolina, with higher concentrations in colder northern waters such as the Gulf of Maine.
Description
A robust, rounded, fan-shaped bivalve shell featuring prominent, radiating ribs extending symmetrically from the straight, well-defined hinge line to the scalloped ventral margin. The surface shows distinct growth stages and localized wear holes, characteristic of a naturally aged or fossilized beach or dredge find.
Key Features
Symmetrical fan-shaped disc, prominent straight hinge ears (auricles), numerous well-defined rounded radial ribs, and a lack of complex internal teeth typical of heterodont bivalves.
Collector Value
Low to moderate commercial value, but highly valued by amateur beachcombers and fossil enthusiasts due to the striking dark aesthetic caused by mineral staining.
Condition Notes
Fair to Good condition. The shell is structurally intact as a single valve with some surface pitting and localized erosion holes near the center, likely caused by boring sponges or natural decomposition during burial. The dark coloration is stable.
Interesting Facts
Scallops are among the few bivalves that can actively swim by clapping their valves together to expel water jets, and they possess dozens of primitive blue eyes lining their mantle edges to detect motion and shadows.
Ecological Role
Acts as an important filter feeder, clearing suspended matter from the water column, and serves as a major food source for sea stars, crabs, fish, and marine mammals.
Similar Species
Calico Scallop (Argopecten gibbus) and Bay Scallop (Argopecten irradians), both of which are generally smaller and more brightly colored with distinct auricular projections.
Beach Finding Tips
Look along northern Atlantic beaches after strong coastal storms, or examine dredged material and fossil banks where ancient marine sediments are exposed.