Diversity of marine ostracods (Crustacea) from the inner Gulf of Thailand

This study examined ostracod assemblages from surface sediments collected at four major river mouths—Mae Klong, Bang Pakong, Chao Phraya, and Tha Chin—and adjacent offshore sites in the Gulf of Thailand. Forty species are identified, including one new genus, Aothai Forel, Chitnarin, Weerachai & Ketwetsuriya gen. nov., with the type species Aothai kresnae sp. nov. Ostracod distribution shows a clear spatial differentiation between river-mouth and offshore environments. River-mouth assemblages are dominated by Neocyprideis agilis (Wouters, 2005) and are characterized by low salinity (less than 30 PSU), shallow depths, and fine-grained sediments. In contrast, offshore assemblages exhibit higher species diversity and are dominated by taxa such as Keijella multisulcus Whatley & Zhao, 1988, Sinocytheridea impressa (Brady, 1869), Hemicytheridea cancellata (Brady, 1868), Stigmatocythere indica (Jain, 1977), and Neomonoceratina rhomboidea (Brady, 1868). This study provides the first comprehensive documentation of modern ostracod assemblages from the inner Gulf of Thailand and establishes a baseline for future taxonomic, ecological, and palaeoenvironmental investigations in this region.