Unio auricularius Spengler, 1793 Pseudunio auricularia (Spengler, 1793) Pseudunio auricularius auricularius (Spengler, 1793)[2] Unio sinuata Lamarck, 1819 Margaritifera auricularia is a species of European freshwater mussel, an aquatic bivalve mollusk in the family Margaritiferidae, the freshwater pearl mussels.

Formerly found throughout western and central Europe, the species is now critically endangered and is one of the rarest invertebrates worldwide, being confined to a few rivers in Spain and France.

When it is placed in the genus Margaritifera Schumacher, 1816, it is considered to be: At other times it is placed in the genus Pseudunio F. Haas, 1910, in which case it is known as: Sometimes it is given the masculine gender: It is found in: The fish hosts for the glochidium larvae of this species are: Salaria fluviatilis, Gambusia holbrooki, Acipenser baerii, Acipenser naccarii and Acipenser sturio.

[5] The hosts for this species were unknown for a long time: as recently as 1998 they were still not known.

Identification of the river blenny, Salaria fluviatilis, as a host to the glochidia of Margaritifera auricularia.