The systematics of the viviparid freshwater snail genus Margarya endemic to the ancient lakes of Yunnan, China, is revised based on comparative analyses of morphological features, including shell, operculum, radula, and genital anatomy, and molecular phylogenetic analyses of partial sequences of the mitochondrial 16S rDNA (16S) and cytochrome c oxidase subunit I (COI) genes, as well as the nuclear Internal Transcribed Spacer 2 (ITS2). The taxonomic utility of key anatomical and morphological features in this group is evaluated. The genus Margarya as delimited previously is split into three genera in order to retain monophyletic taxa: (1) Margarya s.s., consisting of four species, i.e. the type species Margarya melanioides plus Margarya francheti, Margarya oxytropoides, and Margarya monodi; (2) the previously introduced subgenus Tchangmargarya is elevated to an independent genus containing two species, Tchangmargarya yangtsunghaiensis and the new species Tchangmargarya multilabiata sp. nov.; and (3) a new genus, Anularya gen. nov., is described, also containing two species, i.e. Anularya mansuyi and Anularya bicostata. Molecular phylogenies based on analyses of three gene fragments have identical topologies, supporting the monophyly of these genera. The sister group of Margarya s.s. is Cipangopaludina, whereas the sister group of Anularya is Sinotaia; Tchangmargarya is sister to a clade containing all the aforementioned groups. Features of the operculum and the right male tentacle (penis) are particularly informative on the generic level, whereas shell and radular characters are especially useful to differentiate species. The phylogenetic relationships recovered here are consistent with orogenic patterns of the Yunnan Mountains. Changes in the river system and water area of ancient lakes caused by tectonic activities probably play an important role in speciation and shaping the current pattern of species distribution in Yunnan.

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.

A new genus of viviparid snail, Dalipaludinagen. nov., from the Yunnan Plateau of China is described within an integrative taxonomic framework based on data from the mitochondrial COI marker and morphology. Dalipaludina can be distinguished from all other viviparid genera by a unique combination shell, operculum and radula characters. Four species are assigned here to the new genus, Dalipaludina delavayanacomb. nov., Dalipaludina oxytropoidescomb. nov., Dalipaludina occidentaliscomb. nov., and Dalipaludina pyramidellacomb. nov., and one species is newly assigned to Margarya, Margarya dianchiensiscomb. nov. The four species of Dalipaludina are allopatrically distributed in shallow water lentic habitats at high altitude regions of the Yunnan Plateau.

Morphometrics are fundamental for the analysis of size and shape in fossils, particularly because soft parts or DNA are rarely preserved and hard parts such as shells are commonly the only source of information. Geometric morphometrics, that is, landmark analysis, is well established for the description of shape but it exhibits a couple of shortcomings resulting from subjective choices during landmarking (number and position of landmarks) and from difficulties in resolving shape at the level of micro‐sculpture. With the aid of high‐resolution 3D scanning technology and analyses of fractal dimensions, we test whether such shortcomings of linear and landmark morphometrics can be overcome. As a model group, we selected a clade of modern viviparid gastropods from Lake Lugu, with shells that show a high degree of sculptural variation. Linear and landmark analyses were applied to the same shells in order to establish the fractal dimensions. The genetic diversity of the gastropod clade was assessed. The genetic results suggest that the gastropod clade represents a single species. The results of all morphometric methods applied are in line with the genetic results, which is that no specific morphotype could be delimited. Apart from this overall agreement, landmark and fractal dimension analyses do not correspond to each other but represent data sets with different information. Generally, the fractal dimension values quantify the roughness of the shell surface, the resolution of the 3D scans determining the level. In our approach, we captured the micro‐sculpture but not the first‐order sculptural elements, which explains that fractal dimension and landmark data are not in phase. We can show that analyzing fractal dimensions of gastropod shells opens a window to more detailed information that can be considered in evolutionary and ecological contexts. We propose that using low‐resolution 3D scans may successfully substitute landmark analyses because it overcomes the subjective landmarking. Analyses of 3D scans with higher resolution than used in this study will provide surface roughness information at the mineralogical level. We suggest that fractal dimension analyses of a combination of differently resolved 3D models will significantly improve the quality of shell morphometrics.

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