A new species of Parasesarma (Brachyura, Sesarmidae) from Western Australia, with a key to the species from Australia

Nine species of <i>Parasesarma</i> are currently recorded from continental Australian mangroves. The present study describes a new species, <i>P. otiense</i> <b>sp. nov.</b>, from Western Australia. <i>Parasesarma otiense</i> <b>sp. nov.</b> occurs sympatrically with <i>P. hartogi</i> and <i>P. holthuisi</i> in the mangroves of Exmouth Gulf. In both COX1 and 16SBI trees, the new species is well nested within <i>Parasesarma</i>, but divergent from other species. Morphologically, the new species is distinct from other <i>Parasesarma</i> in having eight asymmetric tubercles with the distal slope longer than the proximal slope on the upper surface of the cheliped dactylus. <i>Parasesarma otiense</i> is the tenth species of <i>Parasesarma</i> recorded from continental Australia, taking the number of species assigned to the genus <i>Parasesarma</i> to 59. A key to the species of <i>Parasesarma</i> known from Australian waters is provided to aid in their identification.