The neglected operculum: A revision of the opercular characters in river snails (Caenogastropoda: Viviparidae)

Abstract

The morphological identification of many groups of gastropods is mostly based on shell morphology and genital structures. The value of opercular characters as taxonomic characters has so far been barely studied and evaluated. Here, the opercular characters of river snails (Viviparidae) have been revised systematically for the first time. Based on a morphological study of the opercula of 38 species of 25 viviparid genera, 16 newly defined opercular characters are shown to be useful for genus and species identification. A detailed diagnosis and description of opercular characters for each genus/species is given. One new generic assignment of a viviparid species is proposed based on this study, namely Cipangopaludina nagaensis n. comb.