<i>Decodon erythroleukos</i> , a new deepwater species of hypsigenyin wrasse ( <scp>Teleostei: Labridae</scp> ) from the western <scp>Pacific Ocean</scp>

Decodon erythroleukos sp. nov. is described based on three specimens: the holotype from Okinawa, southern Japan, and one paratype each from Jewell Reef, Great Barrier Reef in Australia, and New Caledonia. The new species appears most closely related to the sympatric Decodon pacificus, sharing similar meristic and morphometric details and differing primarily based on colouration. However, molecular analysis of the mitochondrial COI gene reveals a substantial pair-wise difference of 6.2%-6.9% between the two species. Decodon pacificus is rediagnosed based on the holotype and newly collected material, and its hitherto unknown juveniles are detailed and their live colouration illustrated for the first time. Phylogenetic relationships among species of Decodon are investigated based on mitochondrial and nuclear sequence data, and a revised key to species is provided.