A new species of Gaillardiellus Guinot, 1976 (Crustacea, Brachyura, Xanthidae) from the coral reefs of the South China Sea

A new xanthid species of Gaillardiellus Guinot, 1976, is described from the coral reefs of the Xisha and Nansha Islands in the South China Sea. The new species, Gaillardiellus magiruber sp. nov., closely resembles G. rueppellii (Krauss, 1843) but can be distinguished mainly by its closer proximity of the outer orbital angle and anterolateral margin, which lacks an accessory lobe, a broader and non-protruding front, and notable differences in live coloration and size.

Molecular analysis of mitochondrial cytochrome c oxidase I (COI) sequences further corroborates the validity of this new species. An updated identification key for Gaillardiellus is provided.