Margarya

Margarya is a genus of large operculate freshwater snails, aquatic gastropod molluscs in the family Viviparidae.

Taxonomy
The genus Margarya was described by Nevill (1877) based on shells of the type species collected by A.R. Margary from Lake Erhai, the type locality of Margarya melanioides. Based on shell and radular morphology, Tchang & Tsi (1949) revised this genus for the first time and recognized seven distinct species. He created two subgenera of Margarya, viz Tchangmargarya and Mabillemargarya. The first molecular phylogeny showed that the genus Margarya is polyphyletic and divided into three distinct clades. Combining study of comparative morphology and molecular phylogeny, Zhang et al. revised the systematics of Margarya and recognized eight genuine extant species. However, only four species were found belonging to Margarya s. str., the rest species belonging to distinct genus Tchangmargarya or Anularya.

Distribution
This genus appear to be endemic to Dian Lake, Erhai Lake, Cibi Lake, Jianhu Lake, Xihu Lake, and Lugu Lake in Yunnan Province in the China.

Species
There are 4 extant species and 4 fossil species of Margarya s. str. Margarya bicostata and Margarya mansuyi are transferred to Anularya. Margarya yangtsunghaiensis is transferred to Tchangmargarya. Species within the genus Margarya include 8 species: Species brought into synonymy:
 * (extant) Margarya francheti (Mabille, 1886)
 * (extant) Margarya melanioides Nevill, 1877 - type species
 * (extant) Margarya monodi (Dautzenberg & Fischer, 1905)
 * (extant) Margarya oxytropoides (Heude, 1889)
 * (fossil) Margarya spinicostata Li, 1987
 * (fossil) Margarya angulata Li, 1987
 * (fossil) Margarya nana Huang, 1986
 * (fossil) Margarya nanningensis Tian, Fuersich & Schneider 2013
 * Margarya carinata (Neumayr, 1887) : synonym of Margarya melanioides Nevill, 1877
 * Vivipara delavayi (Mabille, 1886) : synonym of Margarya melanioides Nevill, 1877
 * Margarya tropidophora (Mabille, 1886) : synonym of Margarya francheti (Mabille, 1886)
 * Cipangopaludina dianchiensis Zhang, 1990 : synonym of Margarya oxytropoides (Heude, 1889)
 * Margarya melanioides dianchiensis Huang, 2007 : synonym of Margarya oxytropoides (Heude, 1889)
 * Margarya elongata Tchang & Tsi, 1949 : synonym of Margarya monodi (Dautzenberg & H. Fischer, 1905)
 * Margarya tchangsii Xia, 1982 : synonym of Margarya monodi (Dautzenberg & H. Fischer, 1905)
 * Margarya yangtsunghaiensis Tchang & Tsi, 1949 : synonym of Tchangmargarya yangtsunghaiensis (Tchang & Tsi, 1949)
 * Margarya yini (Tchang & Tsi, 1982) : synonym of Margarya monodi (Dautzenberg & H. Fischer, 1905)

Cladogram
The cladogram based on sequences of mitochondrial 16S ribosomal RNA and cytochrome-c oxidase I (COI), and nuclear ITS2 genes showing the phylogenic relationships of the genus Margarya indicates that Margarya is polyphyletic. Margarya as traditionally delimited decayed into three distinct clades. The sister lineages of two of these clades are representatives from different viviparid genera, which are widely distributed in East and Southeast Asian rivers and lakes. These predominantly riparian viviparids also differ markedly in their shell morphology. Herein only genus-level phylogenic relationship is given, whereas relationship between lower taxonomic units deserve further study.