Saddle Oyster (also known as Jingle Shell or False Oyster)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Anomiidae, Genus: Anomia, Species: Anomia trigonopsis · Anomiidae (Jingle shells or Saddle oysters) · Bivalve (Two-shelled mollusk); this specimen is a single upper (left) valve. The shape is sub-circular to irregular.
Species
Anomia trigonopsis (High confidence based on locality and morphology)
Shell Type
Bivalve (Two-shelled mollusk); this specimen is a single upper (left) valve. The shape is sub-circular to irregular.
Family
Anomiidae (Jingle shells or Saddle oysters)
Size
Approximately 35-45mm in diameter. This is a mature size for the species, which typically ranges from 20mm to 60mm.
Color & Pattern
Naturally translucent pearly-white to silvery-grey with subtle yellowish-tan highlights near the margins. This specimen appears slightly weathered and sun-bleached. The interior (if visible) would typically show a brilliant nacreous/mother-of-pearl iridescence.
Rarity
Very Common (Extremely frequent find on Brisbane beaches like Sandgate and Brighton).
Habitat
Found in intertidal and shallow subtidal zones, typically attached to hard substrates like rocks, larger shells, or jetty pilings in bays and estuaries.
Geographic Range
Mainly the South-Western Pacific; very common along the coasts of Australia (including Queensland/Brisbane) and New Zealand.
Description
A thin, translucent, and slightly fragile bivalve shell with an irregular, wavy outline. The exterior is characterized by fine concentric growth lines and a 'scaly' or lamellar texture. It has a distinctively pearly, metallic luster that catches the light, giving it a gemstone-like appearance when wet.
Key Features
Thin, translucent shell structure; pearly nacreous luster; irregular shape that often conforms to the substrate it was attached to; lack of distinct radial ribs (unlike some scallops).
Collector Value
Low monetary value due to its abundance, but high aesthetic value for craft-makers and beachcombers. Pristine, colorful specimens (orange or deep gold) are more desirable than beach-worn white ones.
Condition Notes
Fair to Good. The shell is intact but shows significant surface weathering and loss of the original vivid luster due to exposure on the beach. There are small chips along the delicate margins and some calcified deposits from other marine organisms.
Interesting Facts
The common name 'Jingle Shell' comes from the sound they make when several are shaken together in a pocket or used in wind chimes. The living animal attaches to rocks via a calcified byssus that passes through a permanent hole in the bottom (right) valve—a feature unique to this family.
Ecological Role
Filter feeder that helps clear the water of plankton and organic debris. They serve as a food source for predatory gastropods (boring snails) and certain crab species. They are generally not restricted but should be collected responsibly.
Similar Species
Monia zelandica (which is usually larger and more ridged) and Placunamiola species. It can be distinguished from oyster spat by its pearly interior and thinner shell.
Beach Finding Tips
Look along the high-tide line after a storm or strong swell. They are often found mixed in with shell grit and seaweed in calm bay areas like Sandgate. Look for the 'glint' of pearl against the sand.
Notes
Brighton beach Sandgate in Brisbane