Description of a new species of the genus Islamia Radoman, 1973 (Caenogastropoda: Hydrobiidae) from deposits of the Neogene in Southern Spain

Abstract

The Hydrobiidae family stands out as the most specious group among freshwater gastropods, with approximately 906 described species, the majority of which are narrow-range endemics. Analysing and classifying these organisms pose significant challenges due to their diminutive size (typically 1 to 5 mm) and simplified morphology, offering limited morphological characteristics for differentiation. The genus Islamia, with a high species richness, occurs mainly in the Mediterranean continental ecosystems, with ca. 50 nominal species, including four fossil species. There are limited references to fossils of Islamia specimens in Spain, and some records may have erroneous genus assignments. The current study introduces a new species of the genus Islamia from Neogene deposits near Alcalá de Jucar, Spain. This research aims to formally describe Islamia arcana sp. nov. based on shell shape characteristics. The discovery of new species in the Júcar Valley sedimentary rocks marks the first record of this genus in the Iberian Peninsula for the Neogene period. The estimated age of the sedimentary rocks in the Júcar Valley aligns with previous molecular clock estimates for the extant species and the proposed age of the genus Islamia within a European context.