Ostrea equestris
species of mollusc
Ostrea equestris, commonly known as the crested oyster or horse oyster, is a species of bivalve mollusc in the family Ostreidae. It can be found along the Atlantic coast of North and South America, ranging from Virginia to Patagonia.
Description
The crested oyster has an irregular triangular or oval shape and grows to a length of about 5 cm (2 in). The left valve is deeply concave, has a raised margin and is fixed to the substrate, while the right is flattish and fits inside the other. The valves are thick with variable surface sculpturing, the whitish colour often obscured by mud, algal growth and encrusting organisms. The inside of the valves is pearly grey or greenish, and the muscle scar is colourless, which distinguishes this species from the much larger eastern oyster (Crassostrea virginica) which has a purple muscle scar.
Distribution and habitat
The species is found in shallow water on the Atlantic coast of North, Central and South America. Its range extends from Virginia in the United States southwards to San Matías Gulf in Patagonia. It grows on rocks, shells, jetties, oil platforms and other hard substrates in the subtidal zone.
Uses
The crested oyster has been eaten by humans for at least 6,000 years; the empty shells have been found in shell middens dating to that period on the coast of the Santa Lucía River basin where there were lagoons beside the estuary.
This brief starts where responsible research should: with the source description of “Ostrea equestris” as species of mollusc. Everything that follows is an evidence route, not borrowed authority.
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The subject matters to the science & nature register because the source frames it as species of mollusc. Its deeper value depends on whether names, dates, institutions and citations support that framing.
Stable identifiers, scientific names and standards terminology offer the best bridge between this overview and specialist evidence. The source revision retrieved here is dated May 21, 2026. The linked authority identifier is Q3796581. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Ostrea equestris” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.