LAUSR

Abstract Background The grouper Epinephelusrankini, described from the waters off Western Australia, has long been regarded as a junior synonym of Epinephelusmultinotatus. However, the two species are discernible as distinct species on the basis of their morphological characteristics and genetic differences by the holotype material and non-type of specimens. New information In this study, Epinephelusrankini is considered as a valid species and re-described based on the examination of the holotype and additional specimens. Epinephelusrankini can be distinguished from the closely-related species E.multinotatus by the following combination of characters: body dark greyish-brown to chocolate with irregular white blotches (vs. body pale brownish-grey with irregular and small white blotches in E.multinotatus), absence of small dark brown spots (vs. numerous small dark brown spots in E.multinotatus). Furthermore, genetic differences between the two species strongly support the validity of both species based on molecular analysis (mtDNA, COI gene). In addition based on the sampling range, E.rankini was observed range from the Abrolhos Islands of Western Australia to south-eastern Indonesia, while E.multinotatus ranges from the Persian Gulf to southern Mozambique.