Description: This saddle oyster can be up to 60 mm. It is usually white or grey, occasionally with a tinge of pink, purple or blue. The shell has a sculptured surface of wavy concentric lines which are often raised in an irregular scales, and the surface is often covered with barnacles, bryozoans, calcareous algae etc. The valves often take on the shape of the surface on which they are growing so can be quite irregular in shape. The left valve is convex and more solid, while the right valve is flat or irregularly concave, and more fragile. There are three distinct scars on the left valve in a diagonal line in the concave section of the shell.

Habitat: Attached to hard substrata and also sometimes algal holdfasts. Found from the lower shore down to 150 m or deeper.

Distribution: Recorded from all around Britain and Ireland.

Similar Species: There are a few species of saddle oyster found in Britain and Ireland which could potentially be confused. Anomia ephippium has three scars on the left valve while Pododesmus patelliformis only has two.

Key Identification Features:

• Saddle oyster up to 60 mm in length.
• White or grey; occasionally tinged with blue, purple or pink.
• Left valve convex, right valve flat or irregularly concave.
• Three scars on left valve.

Distribution Map from NBN: Anomia ephippium at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Anomia ephippium at iNaturalist World Species Observations database.

GBIF data for Anomia ephippium

WoRMS: Anomia ephippium at World Register of Marine Species. Accepted name: Anomia ephippium Linnaeus, 1758. AphiaID: 138748.

Classification: Biota; Animalia; Mollusca; Bivalvia; Autobranchia; Pteriomorphia; Pectinida; Anomioidea; Anomiidae; Anomia