Saddle Oyster fragment (also known as a Jingle Shell or Windowpane Oyster fragment)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Anomiidae, Genus: Anomia, Species: descripta · Anomiidae (Jingle shells or Saddle oysters) · Bivalve (fragment). Specifically, it appears to be a worn portion of the upper (left) valve showing calcified attachment points.
Species
Most likely Anomia descripta (Confidence: 85% based on location)
Shell Type
Bivalve (fragment). Specifically, it appears to be a worn portion of the upper (left) valve showing calcified attachment points.
Family
Anomiidae (Jingle shells or Saddle oysters)
Size
Approximately 20-30mm in width. This is small for the species; adults can reach 60-100mm.
Color & Pattern
Translucent white to pearly cream. The fragment has an iridescent, nacreous luster typical of the family's interior. No visible banding remains due to erosion and specimen thinness.
Rarity
Very Common. These shells are frequently found as fragments on beaches after high tides or storms.
Habitat
Intertidal and shallow subtidal zones. They adhere to hard substrates like rocks, jetty pylons, or other larger shells in protected bays.
Geographic Range
Indo-West Pacific; specifically common along the coast of Queensland (QLD), Australia, and surrounding tropical waters.
Description
A beach-worn, irregular fragment of a Bivalve shell. It possesses a characteristic thin, translucent, and pearly texture. The shape is wavy and 'saddle-like' with a visible pin-hole which likely represents a predator bore hole or a worn portion near the byssal notch.
Key Features
Translucency, pearly/mother-of-pearl luster, and a paper-thin, fragile structure. The irregular, wavy margins are diagnostic of the Anomiidae family.
Collector Value
Low. While aesthetically pleasing due to the luster, fragments are generally not valued by serious collectors unless they are complete valves with intact hinges and byssal notches.
Condition Notes
Poor/Fragmentary. This is not a complete specimen; it is a broken shard that has been significantly weathered by wave action. A small hole is visible, possibly from a predatory gastropod. Collector grade: Poor.
Interesting Facts
Commonly called 'Jingle Shells' because when several are shaken together, they make a metallic tinkling sound. The living animal attaches to rocks via a calcified plug that passes through a hole in the lower valve.
Ecological Role
Filter feeders that help clear the water of plankton. They provide habitat for secondary encrusting organisms. They are preyed upon by sea stars and drills.
Similar Species
Monia zelandica (which is typically larger and more circular) and various species of Placuna (Windowpane oysters), which are flatter and more symmetrical.
Beach Finding Tips
Look in the drift line at Brighton/Sandgate during low tide. They are often mixed in with shell grit and seaweed. Look for the 'shimmer' of the nacre against the sand.
Notes
Brighton Sandgate qld