A new species of supergiant Bathynomus A. Milne-Edwards, 1879 (Isopoda: Cirolanidae) from the Paracel Islands, South China Sea

<i>B.paracelensis</i> sp. nov. is the third supergiant <i>Bathynomus</i> discovered in the South China Sea after <i>B.jamesi</i> and <i>B.vaderi</i>. Its remarkable feature is its short body length and sub-parallel shape. In addition, it is different from <i>B.jamesi</i> and <i>B.vaderi</i> in features such as clypeus shape, number of maxillula keratinised spine and pleotelson spine almost straight. Phylogenetic and barcoding gap analyses confirm that <i>B.paracelensis</i> sp. nov. is not the same species as <i>B.jamsei</i>. Many morphological differences also indicate that it should be a different species from <i>B.vaderi</i>. <i>B.paracelensis</i> sp. nov. may be an intermediate species between giant and supergiant, possessing characteristics of both categories, which can increase researchers' understanding of <i>Bathynomus</i> biodiversity.