Salinalona gen. nov., an euryhaline chydorid lineage (Crustacea: Branchiopoda: Cladocera: Anomopoda) from the Oriental region

Until now, a single endemic cladoceran genus was known from the Oriental region. We propose the region’s second endemic lineage of generic rank, Salinalona gen. nov., to accomodate the South East Asian Alona sarasinorum Stingelin, 1900 and the Indian A. taraporevalae Shirgur and Naik, 1977. Morphological revision shows that the external similarities with Alona Baird, 1843 or Leberis Smirnov, 1969 and Celsinotum Frey, 1991 that have been proposed in the past, are the result of convergence. The small lineage is euryhaline, even halophylic, an unusual adaptation in the order Anomopoda and particularly in the family Chydoridae. We discuss the position and adaptation of Salinalona gen. nov., such as a strongly modified hook on the first limb, based on a detailed study of populations from Maikhao peat swamp, Phuket island, Thailand. We include comparative notes on the circumtropical genus Euryalona Sars, 1901, with detailed morphology of the Asian E. orientalis (Daday, 1898). A key to all species of both genera is included.