Saddle Oyster (or Jingle Shell)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Anomiidae, Genus: Anomia, Species: trigonopsis · Anomiidae (Jingle shells/Saddle oysters) · Bivalve; this is a single valve fragment (likely the upper valve). Irregular/discoid shape.
Species
Anomia trigonopsis (Common Saddle Oyster)
Shell Type
Bivalve; this is a single valve fragment (likely the upper valve). Irregular/discoid shape.
Family
Anomiidae (Jingle shells/Saddle oysters)
Size
Approximately 30-40mm in length. This is a medium-sized specimen; adults can reach 60-70mm.
Color & Pattern
Pale golden yellow to translucent creamy white. Features a pearly, nacreous interior luster. Some dark environmental staining and oxidation from the sandy substrate are visible.
Rarity
Common. These are frequently washed up on Brisbane beaches after high tides or storms.
Habitat
Found in intertidal and shallow subtidal zones. These shells cement themselves to hard substrates like rocks, jetty pylons, or other shells using a calcified byssus.
Geographic Range
Common throughout Indo-Pacific waters, including the eastern coastline of Australia and specifically Moreton Bay/Sandgate areas.
Description
An irregularly shaped, thin, and translucent bivalve valve. The shell has a distinctive waxy or pearly sheen, mimicking the appearance of a potato chip or a piece of crumpled gold foil. The margins are thin and fragile, often following the contour of the object it was originally attached to.
Key Features
Translucency, pearly nacreous luster, and an irregular, flattened shape with a notable muscular scar area visible on the interior.
Collector Value
Minimal monetary value, but high aesthetic value for crafters and beachcombers due to their unique color and light-catching properties.
Condition Notes
Fair. The shell is a beach-worn fragment with some erosion on the margins and environmental debris adhering to the surface. It lacks the lower valve and the calcified plug.
Interesting Facts
They are called 'Jingle Shells' because when several are shaken together, they make a metallic tinkling sound. The lower valve has a unique hole (foramen) through which a calcified foot attaches the animal permanently to a rock.
Ecological Role
Filter feeders that help clear the water column of plankton. They provide micro-habitats for other small organisms on their crinkled surfaces.
Similar Species
Monia zelandica (which is usually larger and more ribbed) and various species of Placuna (Windowpane oysters), which are more symmetrical and flatter.
Beach Finding Tips
Look in the high-tide drift lines at Sandgate or Brighton Beach, specifically among shell hash and small rocks where the tide deposits lighter, flatter materials.
Notes
Brighton beach Sandgate in Brisbane