Description: This saddle oyster is usually broadly circular or oval in shape but can have an irregular form depending on where it is growing. It can be up to 40 mm in size. It is attached by byssus threads through a hole in the right valve. The shell is thin, brittle and white or grey in colour, sometimes with patches of pale brown or red-brown. The left valve is convex and more solid than the concave right valve. The left valve has two scars – an oval byssal scar directly below the umbo and a circular muscle scar. The right valve has a large oval-shaped or drop-shaped byssal aperture.

Habitat: Attached to hard substrata, usually on hard ground or on dead shells. Offshore right to the edge of the Continental Shelf.

Distribution: Recorded from most coasts around Britain and Ireland, seemingly absent from SE corner of Britain.

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 40 mm.
• Thin, brittle shell that is usually white or grey sometimes with light brown or red-brown patches.
• Two scars on left valve.

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

iNaturalist: Pododesmus patelliformis at iNaturalist World Species Observations database.

GBIF data for Pododesmus patelliformis

WoRMS: Pododesmus patelliformis at World Register of Marine Species. Accepted name: Pododesmus patelliformis (Linnaeus, 1761). AphiaID: 138751.

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