Dispersal is known to play an important role in shaping the diversity and geographic range of freshwater gastropods. Here, we used phylogenetic methods to test for the influence of dispersal and other biogeographic processes (such as vicariance) on the speciation and distribution patterns of Mercuria Boeters, 1971, a snail genus widely distributed in the western Palaearctic. The 25 extant species traditionally thought to comprise the genus, which were described mainly on the basis of morphology, have been recorded from lowland waters in both the Mediterranean and Atlantic river basins of Europe and North Africa. Using molecular phylogenies based on three gene fragments (COI, 16S rRNA and 28S rRNA) from 209 individuals, four molecular species delimitation methods and a shell characterization, we identified 14 putative species in our dataset, nine of which correspond to species classified by traditional taxonomy. Furthermore, biogeographical modelling favoured a scenario in which recurrent founder-event speciation since the late Miocene is the most probable process explaining the species diversity and distribution of the Mediterranean clades, whereas episodes of postglacial northward colonization from Iberian refugia by the species M.tachoensis may explain the current presence of the genus in Atlantic lowlands. The dispersal events inferred for Mercuria, probably promoted by multiple factors such as the changing connectivity of drainage basins driven by climate change or better access for avian dispersal vectors in lowlands, may explain the rare case among hydrobiids of a species-rich genus containing individual species with a large distribution area.

The freshwater snail genus Mercuria is widely distributed in lowland waters across Western Europe, Northern Africa and the Mediterranean islands. Approximately two-thirds of the currently recognised species are described based on their shell morphology, which may vary within species due to biotic and abiotic factors. Recent molecular phylogenies that included numerous previously documented populations recovered 14 species clades, nine of which correspond to nominal species and five, to undescribed taxa. Here, we formally describe the five undescribed taxa as new species and provide morphological descriptions of the shell and other anatomical structures for three of the other inferred clades and for the species M. maceana to elucidate their taxonomic status and assess the utility of morphological characters for species delimitation in Mercuria. Taken together, the morphological and molecular evidence suggest new identifications and synonymies, having implications on the known geographic range of the studied species, including the type species M. similis. Anatomical measurements and geometric morphometric analysis of shell shape revealed no clear differentiation among the species analysed, predicting the importance of molecular data in elucidating the species diversity of the genus.

Cerion mumia is a complex of eight subspecies distributed along the north coast of Cuba from Pinar del Rio to Camaguey provinces. The geometric morphometric analysis presented here was aimed at identifying patterns of shell shape variation to test the hypothesis of colonisation through land bridges during the Eocene-Oligocene. C. mumia cuspidatum, the easternmost population, was similar in shape to the subspecies from the north coast of Havana, but showed morphometric differences suggesting allopatric speciation followed by dispersal. The shells from the west were more globose than those from Havana or the east, which tended to be more cylindrical, as shown by the thin-plate spline analysis. As a result of the morphometric analysis I propose to elevate C. noriae comb. nov. and C. wrighti comb. nov. to species rank and to include C. noriae hondanum comb. nov. as a subspecies of C. noriae comb. nov. I report a second locality of C. noriae comb. nov. at Playa Santa Fe formation from the late upper Pleistocene. Geometric morphometric techniques are useful in species identification through comparing new samples with type material.

We studied a Middle Pleistocene molluscan association from northern Tenerife. It was composed of 14 species, all found in the TL-1 and TL-2 stratigraphic beds of the middle Pleistocene Unit I. The families present were Helicidae, Enidae with two new species, Pomatiidae, Canariellidae, Vitrinidae and Geomitridae. For the Geometric Morphometrics (GM) analysis, a total of 58 pictures from three localities were analysed, comparing the morphological similarities between Napaeus guanche sp. nov., and some closely related extant species, Pomatias laevigatus and extant and fossil Hemicycla eurythyra based on shell shape. According to the PCA, Napaeus accounted for 77.53% of the variation of the shell shape within the first two components, Hemicycla accounted for 62.62% and Pomatias accounted for 52.79%. The permutational ANOVA showed to be a useful analysis to discriminate between groups, presenting non-significance for Napaeus, and significance for Hemicycla and Pomatias depicting high similarity. Despite this, the dispersion analysis showed a relatively high dispersion of the dataset for Napaeus and Pomatias, related to sample size, while for Hemicycla, the result was significant and congruent with permutational ANOVA. We describe two new species, Napaeus lipauges and Napaeus guanche increasing the known diversity of the genus Napaeus in the Canary Islands.

Corrosella (family Hydrobiidae) represents one of the most diverse and threatened groups of spring snails in the Iberian Peninsula and Maghreb. Accurate delineation of species boundaries and understanding their geographic distributions are critical for effective conservation. However, inconsistent criteria used to define the 25 currently recognised species have led to considerable taxonomic uncertainty. This study presents a systematic revision of 24 species of Corrosella through an integrative approach combining multilocus phylogenies, morphometric analyses of shells and anatomical traits, and ecological characterisation, with comprehensive datasets for 22 species. Molecular and morphological evidence support the synonymisation of C. navasiana, C. collingi, C. tajoensis, C. valladolensis valladolensis, and C. segoviana under the earliest available name C. navasiana. Furthermore, we formally describe C. ballestae Delicado & Ramos sp. nov., a previously unrecognised species, and provide a redescription of the taxonomically complex C. hinzi. Despite a pronounced DNA sequence divergence among most species, morphological and ecological traits show significant overlap, underscoring the indispensable role of molecular data in resolving species diversity. These taxonomic updates refine the classification of Corrosella, elucidate species distributions, and establish a robust framework to support future research and conservation strategies.