Frimbria clams have a very distinctive ornamentation with many closely spaced commarginal ribs on both valves that produce a "frilled" look). Genus Fimbria originated about 180 million years ago during earliest Jurassic time in east Asia and became widespread in warm oceans thereafter; until late Cenozoic time when its geographic range slowly contracted. Today, they are confined to the Indo-Pacific area, where they live in close association with reef-coral habitats (Squires, 1990). Fimbria is currently classified (WoRMS, 2024) as belonging to the subfamily Fimbriidae, within the family Lucinidae.
A specimen of Fimbria fimbriata (Linne, 1758), (2 inches long, and almost 2 inches tall) collected in sand at low tide, in 10 feet of water on the Great Barrier Reef, off the coast of McKay, Queensland, Australia. The images in the above successive sequence are: left-valve exterior and interior; right-valve exterior and interior, and top view of both valves together (articulated). Notice how confusingly similar the two valves are exteriorly.
References Cited:
Squires, R. L. 1990. New Paleogene Fimbria (Mollusca: Bivalvia) from the Pacific coast of southwestern North America. Journal of Paleontology 64(4): pp. 552-556, figs. 1-3.
WoRMS. 2024. https://marinespecies.org
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