Abstract Australian tanaidacean material collected during spring 1993 and 1994 and autumn 1994 and 1995 in vicinity of Port Hedland and Oyster Island (NW Australia) included over 800 of specimens of a new species of apseudomorph, Longiflagrum amphibium sp. n. The species is the fifth to be described in this genus, and it was found in the intertidal zone, as the other species have been. The new species is distinguished from the other members of the genus bythe shortest flagella in the antennule and by its oval pleopod basis.