A propos de quelques noms de na ades : Pourquoi faut- il oublier Potomida et Pseudunio ?

The study of European naiads has long been hampered by troubling problems in nomenclature, rising from a tradition plagued with unjustified usages, and yielding the highest recorded synonymy rates. Here two genus-level names are shown to be still incorrectly used. Pseudunio Haas, 1910 was originally introduced on purely conchological grounds to seggregate Unio auricularius Spengler, 1798 (=U. sinuatus Lamarck, 1819) from Margaritifera Schumacher, 1816. Pseudunio has recently been resurrected by several authors to subgenus and even genus level in monothetic schemes based on variable hinge traits, but molecular genetics and anatomy both fail to support such multiplication of genera, and point instead at the cohesiveness of Margaritifera as the single extant genus of margaritiferids. Potomida Swainson, 1840 was introduced to group all European naiads possessing a heavy hinge, a grouping that is now known to be far from natrual. The type of Potomida is by original designation Unio sinuatus; thus it constitutes a synonym of Margaritifera, as first recognized by Gray (1847). However, Potomida has frequently (but not universally) been used to allocate Unio littoralis Cuvier, 1774, on the basis that the description of this genus includes a figure that can be identified as this species. Actually, the correct genus name for it is Psilunio Stefanescu, 1896; this has priority over Rhombunio Germain, 1911. Therefore, both Pseudunio and Potomida must be abandoned for good; the correct names for the two naiads involved are Margaritifera auricularia (Spengler, 1798) and Psilunio littoralis (Cuvier, 1774).