Saddle Oyster, Windowpane Oyster or Jingle Shell
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Anomiidae, Genus: Anomia, Species: Anomia trigonopsis · Anomiidae (Jingle shells or Saddle oysters) · Bivalve (Right/Lower Valve). Shape is irregular/sub-circular following the substrate.
Species
Anomia trigonopsis (Confidence level: 85%)
Shell Type
Bivalve (Right/Lower Valve). Shape is irregular/sub-circular following the substrate.
Family
Anomiidae (Jingle shells or Saddle oysters)
Size
Approximately 35-45mm in height. This is a medium-sized specimen for the species, which typically reaches 40-70mm.
Color & Pattern
Interior shows a pearly, nacreous luster with soft iridescent hues of silver, blue, and pale gold. The exterior margin is a muddy grey-white. There is a dark, pinpoint calcified mark near the center.
Rarity
Common. These shells are frequently washed up on beaches like Brighton Beach, Brisbane, after storms or high tides.
Habitat
Found in intertidal and shallow subtidal zones. It lives attached to hard substrates like rocks, larger shells, or jetty pylons in coastal bays and estuaries.
Geographic Range
Common along the eastern coast of Australia, particularly in Queensland (Brisbane area) and New South Wales, as well as New Zealand.
Description
An attractive but irregular bivalve shell characterized by its thin, translucent, and pearly interior. The shell is technically the lower (right) valve, which grows to fit the contours of the rock it was attached to. It has a distinctive waxy or silky sheen, resembling a piece of biological stained glass.
Key Features
Translucent appearance, high nacreous luster inside, irregular shape determined by attachment surface, and a small hole or notch near the hinge (byssal notch) where the animal originally attached itself.
Collector Value
Minimal monetary value (roughly $1-$5 USD), but highly desired by beachcombers and crafters for their iridescent colors. Valued more as a 'beach find' rather than a high-end investment piece.
Condition Notes
Fair to Good. The shell is a single valve (lower). It shows some edge wear and minor surface erosion but retains its beautiful inner iridescence. Collectibility Grade: Good.
Interesting Facts
Members of this family are called 'Jingle Shells' because when many are shaken together in a bag/hand, they make a metallic tinkling sound. The animal has a calcified 'plug' that passes through a hole in the shell to anchor it permanently to a rock.
Ecological Role
A filter feeder that helps clarify coastal waters. It serves as a substrate for other small encrusting organisms and is preyed upon by sea stars and predatory gastropods.
Similar Species
Monia zelandica (larger/greener) and Placuna placenta (larger, flatter, more circular). Distinguishable from common edible oysters by the lack of heavy, chalky layering and the presence of nacre.
Beach Finding Tips
Look in the drift line at Brighton Beach during low tide, especially after a period of rough surf. They are often found mixed with shell grit and debris near rocky outcrops.
Notes
Underneath/bottom side of shell on Brighton beach Brisbane