Pacific Wing Oyster (fragment)
Phylum: Mollusca, Class: Bivalvia, Order: Ostreida, Family: Pteriidae, Genus: Pteria, Species: Pteria sterna · Pteriidae (Wing Oyster family) · Bivalve (fragment), fan-shaped with elongated posterior wings
Species
Pteria sterna
Shell Type
Bivalve (fragment), fan-shaped with elongated posterior wings
Family
Pteriidae (Wing Oyster family)
Size
Approx. 1.5 - 2 inches wide; this fragment represents about 30% of an adult shell which can reach 4-5 inches.
Color & Pattern
Off-white to pearly grey exterior with visible concentric growth lines. The interior (nacreous layer) shows a strong silvery-white iridescence, or 'mother of pearl'. The coloring appears slightly weathered/sun-bleached.
Rarity
Common beach find as fragments; complete live-taken specimens are uncommon for casual beachcombers.
Habitat
Attached to hard substrates like rocks, gorgonians (sea fans), or dock pilings in shallow subtidal waters down to 25 meters.
Geographic Range
Eastern Pacific Ocean, from Baja California (Cabo San Lucas) and the Gulf of California south to Peru.
Description
A delicate, pearly fragment of a Pacific Wing Oyster. The shell exhibits the characteristic 'wing' extension near the hinge. Despite being a fragment, it retains the beautiful nacreous luster and fine, concentric ridges that define the species' growth cycles.
Key Features
Elongated hinge line forming a 'wing', thin profile, and a thick interior layer of high-quality iridescent nacre. The fragment shows distinctive drill holes from a predatory sponge or snail.
Collector Value
Minimal financial value as a fragment ($0-$1). Whole, large specimens with intact wings and rich coloration can fetch $10-$20. It is highly valued in the jewelry industry for its mother-of-pearl.
Condition Notes
Poor to Fair (fragmentary). This is a beach-worn piece lacking the complete hinge and paired valve. Presence of small boreholes indicates post-mortem predation or sponge activity. Collectibility is low as a specimen but high as craft material.
Interesting Facts
This species is famous as the 'Perlas del Mar de Cortez' (Pearls of the Sea of Cortez). It was the primary source of the legendary black and grey pearls harvested by Spanish explorers in Mexico during the 16th century.
Ecological Role
Suspension feeders that filter plankton from the water. They provide structural habitat for other small marine organisms and are sensitive indicators of water quality and temperature changes.
Similar Species
Pinctada mazatlanica (Mazatlan Pearl Oyster), which is thicker, more circular, and lacks the elongated wing-like hinge extensions.
Beach Finding Tips
In Cabo, look in the 'wrack line' after a storm or high tide. They are often found tangled in washed-up sea fans (Gorgonians) to which they were originally attached.
Notes
Cabo