Gryphaeidae Ostreidae Ostreoidea is a taxonomic superfamily of bivalve marine mollusc, sometimes simply identified as oysters,[1] containing two families.

[5] Harold Harry (1985) gives a detailed description of the morphological and anatomical features that are common in the superfamily.

[6]: 123–124  Within Ostreoidea, the degree of attachment of the left and right mantle lobes to the visceral mass varies between subgroups.

This is the posterior of the ancestral pair; the anterior muscle is not present in post-larval stages.

This is in contrast to other bivalves with reduced or missing feet where the process occurs later in development.