Biodiversity & Conservation

Saddle oyster - Anomia ephippium

Anomia ephippium

Image David Fenwick - Intertidal saddle oyster Image width ca XX cm
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Distribution map

Anomia ephippium recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

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Anomia ephippium is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Mollusca Snails, slugs, mussels, cockles, clams & squid
Class Bivalvia Clams, cockles, mussels, oysters, and scallops
Authority Linnaeus, 1758
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Common on all coasts of Britain and Ireland.
Habitat information icon Habitat information Found from the intertidal to depths of 150 m on rocks , bivalve shells, often scallop shells and algal holdfasts.
Text page icon Description Anomia ephippium is an irregularly shaped bivalve with a thin shell, found attached to stones and to other bivalve shells. It is approximatelty circular and up to 60 mm in diameter. The right valve is lowemost and adjacent to the substratum, the left valve is uppermost. It attaches to the substratum by byssal threads though a hole in the right valve. The right valve often takes on an impression of the substratum and this is most obvious when an individual has been attached to a scallop. The edge of the left valve is often shaped to fit exactly onto the substratum. The shell is very thin and brittle, usually white with a blue or pink tinge. The left valve has irregular growth lines on its surface although these can be worn off in older individuals.
Identifying features
  • Shell valves unequal. Left valve is convex often overlapping the right valve and has a sculpture of wavy growth lines. The right valve is flat, often taking on the topography of the substratum it is attached to, with a large hole through which the byssum passes for attachment to the substratum.
  • Left valve has three muscle scars in the concavity of the shell.
  • No hinge teeth.
  • Shell white, occasionally with blue or pink tinge.
Additional information icon Additional information The four species of saddle oysters are easy to recognise as a group but it can be difficult to separate the species. Anomia ephippium is distinguished from other saddle oysters (Anomiidae) by a line of three muscle scars on the inside surface of the convex valve.

This review can be cited as follows:

Ken Neal 2004. Anomia ephippium. Saddle oyster. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 19/05/2013]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=2527>