Inland Cardita (alternate: False Cardita, Cockle-like Cardita)
Phylum: Mollusca, Class: Bivalvia, Order: Carditida, Family: Carditidae, Genus: Cardita, Species: C. crassicosta · Carditidae (The Carditid or False Cockle family) · Bivalve (Two-shelled); this specimen is a single valve fragment (left valve), specifically the central portion showing strong radial ribs.
Species
Cardita crassicosta (Identification confidence: 85% based on location and sculpture)
Shell Type
Bivalve (Two-shelled); this specimen is a single valve fragment (left valve), specifically the central portion showing strong radial ribs.
Family
Carditidae (The Carditid or False Cockle family)
Size
Approximately 15-20mm in its current state. Based on proportion, the original full valve was likely 25-30mm. This is average for mature Cardita in the Moreton Bay region.
Color & Pattern
Base color is off-white to cream with distinct orange-brown to ochre mottling along the ribs. The coloration appears naturally weathered. The interior is not visible but would typically be white.
Rarity
Very Common. These are frequently washed up on the beaches of Moreton Bay, especially after high tides or storms.
Habitat
Found in intertidal and shallow subtidal zones, particularly in sandy-mud or gravelly substrates of bays and estuaries. Common in protected coastal waters.
Geographic Range
Endemic to Australia, specifically the Eastern coast ranging from Queensland (including Brisbane/Brighton) down to New South Wales.
Description
A robust, thick-walled bivalve valve fragment featuring prominent, raised radial ribs that are crossed by fine concentric growth lines, giving it a slightly beaded or 'scaled' texture. The shell is sturdy and calcified, designed to withstand turbulent bay waters.
Key Features
Bold, square-shaped radial ribs; strong hinge line (though broken here); orange-tinted peaks on the ribs; thick shell wall compared to similarly sized cockles.
Collector Value
Minimal monetary value ($0-$1) due to the fragmented condition. Complete, 'gem' quality specimens are attractive to local hobbyists but are not high-value international trade items.
Condition Notes
Poor to Fair. This is a beach-worn fragment missing the posterior and anterior margins as well as the umbo (beak). Significant erosion is present on the edges. Collectibility grade: Study Grade/Beach Find.
Interesting Facts
Unlike many bivalves that burrow deep, Carditids often attach themselves to rocks or rubble using a byssus (fine threads), or they live nestled in shallow sediment. They are often mistaken for 'true cockles' but belong to a completely different evolutionary lineage.
Ecological Role
Filter feeders that help clear particulate matter from the water column. They serve as a food source for local rays and predatory gastropods (like Moon Snails) common in Brisbane waters.
Similar Species
Fragum species (True Cockles), which have thinner shells and different hinge structures; and Venericardia species, which often have more rounded ribs.
Beach Finding Tips
Look along the high-tide line at Brighton Beach during low tide. They are often found mixed in with shell 'grit' and debris under mangroves or near jetty pylons.
Notes
Brighton Brisbane