Siambathynella janineana sp. nov. (family Parabathynellidae) discovered in Thailand is herein described. The new species displays an exclusive character: a distinctive organ on the antennule of males. It also unique combination morphological characters, including seven-segmented and antenna, sexual dimorphism antennule, one-segmented exopod thoracopod I two-segmented one thoracopods II to VII, ...