Pacific Wing Oyster (also known as the Winged Pearl Oyster)
Kingdom: Animalia, Phylum: Mollusca, Class: Bivalvia, Order: Ostreida, Family: Pteriidae, Genus: Pteria, Species: Pteria sterna · Pteriidae (Winged Pearl Oyster family) · Bivalve (two-shelled). The specimen shown is a single valve (likely the left valve), displaying a characteristic 'wing-like' elongated posterior ear.
Species
Pteria sterna
Shell Type
Bivalve (two-shelled). The specimen shown is a single valve (likely the left valve), displaying a characteristic 'wing-like' elongated posterior ear.
Family
Pteriidae (Winged Pearl Oyster family)
Size
Approximately 2.5 to 3 inches in length. This is a mid-sized specimen; adults typically range from 2 to 6 inches.
Color & Pattern
Base color is a creamy nacreous white with distinctive radiator-like streaks of reddish-brown and tan along the growth lines. The interior (not fully visible) would possess a brilliant silvery or rainbow iridescence (mother-of-pearl).
Rarity
Common in the Gulf of California (Cabo region), though intact beach-washed specimens in good condition are less common than fragmented ones.
Habitat
Subtidal marine environment. They typically attach themselves via a byssus to rocks, coral, or gorgonians (sea fans) in depths ranging from 1 to 25 meters.
Geographic Range
Eastern Pacific Ocean, ranging from Southern California and Baja California (Cabo San Lucas) south to Peru.
Description
A striking asymmetric bivalve featuring a long, straight hinge line that extends into a distinct 'wing' or auricle. The shell is thin but strong, with a pearly luster. The exterior is relatively smooth except for fine concentric growth lines where the brown pigmentation is concentrated.
Key Features
The most diagnostic feature is the elongated hinge line (the 'wing') and the rich, pearly interior. The brown streaking on a white/cream background and the overall teardrop-to-fan shape are characteristic of Pteria.
Collector Value
Relatively low ($2 - $10 USD) for weathered beach specimens. Gem-quality, large paired valves with intact periostracum and vibrant color are more desirable to collectors but are usually obtained via diving rather than beachcombing.
Condition Notes
Fair to Good. The shell shows significant beach-wear (erosion) which has smoothed down the original scaly texture of the periostracum. The margins are somewhat chipped, and the color is slightly sun-bleached, but the overall form is recognizable.
Interesting Facts
This species is historically significant for 'La Paz pearls.' In the 19th and early 20th centuries, it was the primary source of high-quality natural pearls in Mexico. It is one of the few oyster species that can produce highly valuable 'black' or bronze pearls naturally.
Ecological Role
Suspension feeders that filter plankton from the water column. They provide structural habitat for small epibiotic organisms that grow on their shells. In Mexico, they are a protected species under certain management plans due to historical over-harvesting for the pearl industry.
Similar Species
Pinctada mazatlanica (Mazatlan Pearl Oyster) which is much more circular and lacks the long hinge wing; and Pteria colymbus (Atlantic Wing Oyster), which is geographically separated in the Atlantic/Caribbean.
Beach Finding Tips
In Cabo, look along the high tide line after a storm or strong swell. They are often found entangled in the dried holdfasts of kelp or gorgonians that have washed ashore.
Notes
Cabo